- Effect of calcination temperature on the structure and catalytic performance of copper-ceria mixed oxide catalysts in phenol hydroxylation
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We report on highly active CuO@CeO2 catalysts prepared by the surfactant-template method and calcined at different temperatures. Then the obtained catalysts were characterized by means of various analytical techniques. Our findings show that the BET surface area and pore volume of the CuO@CeO2 catalyst measured by N2 adsorption-desorption are decreasing with the elevation of calcination temperature. From the results of XRD and XPS, we determined the oxidation state of copper in the copper-ceria mixed oxide catalysts. The CuO@CeO2 catalysts displayed good catalytic activity for the phenol hydroxylation using H2O2 as an oxidant. Moreover, we found that the catalytic activity is improved for high calcining temperature and the optimum conditions were obtained when the catalyst CuO@CeO2 is calcined at 800 °C, which lead to higher phenol conversion of 54.62% with 92.87% of selectivity for catechol and hydroquinone. More importantly, the catalyst seems to be easily recovered by simple centrifugation. The results of catalyst recycling illustrated that the catalytic activity remained high even after five cycles with slight Cu leaching and slight loss of activity. Finally, a possible mechanism in phenol hydroxylation by H2O2 over CuO@CeO2 catalyst was also proposed.
- Amadine, Othmane,Essamlali, Younes,Fihri, Aziz,Larzek, Mohamed,Zahouily, Mohamed
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- Oxidation of Electron-Rich Arenes Using HFIP-UHP System
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The straightforward oxidation of electron-rich arenes, namely, phenols, naphthols, and anisole derivatives, under mild reaction conditions, is described by means of the use of an environmentally benign HFIP-UHP system. The corresponding quinones or hydroxylated arenes were obtained in moderate to good yields.
- Llopis, Natalia,Baeza, Alejandro
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- Nitrogen Dioxide and Related Free Radicals: Electron-transfer Reactions with Organic Compounds in Solutions containing Nitrite or Nitrate
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The absolute rate constants for the reaction of NO32-. (formed by one-electron reduction of nitrate) with oxygen, benzoquinone, and methyl viologen have been determined by pulse radiolysis.Experiments have shown that such reactions can occur in competition with the hydrolysis reaction leading to NO2. and that the formation of the latter can be catalysed by the presence of hydrogen or ammonium ions.Absolute rate constants for the oxidation of the phenothiazine derivative metiazinic acid, of 2,2'-azinobis-(3-ethyl-2,3-dihydrobenzothiazole-6-sulphonate), of ascorbate, and of dihydroxyfumarate by NO2. have also been measured.
- Forni, Luigi G.,Mora-Arellano, Victor O.,Packer, John E.,Willson, Robin L.
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- Improving removal of 4-chlorophenol using a TiO2 photocatalytic system with microwave and ultraviolet radiation
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A conventional photocatalytic system is a viable tool to purify wastewaters, whereas poor degradation performance due to diverse pollutants under various conditions still leaves it behind commercial markets. This study aimed to determine the degradation e
- Ki, Seo Jin,Jeon, Ki-Joon,Park, Young-Kwon,Jeong, Sangmin,Lee, Heon,Jung, Sang-Chul
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- Synthesis of Cu2 (OH)PO4 crystals with various morphologies and their catalytic activity in hydroxylation of phenol
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Copper hydroxyphosphate (Cu2(OH)PO4) crystals with various morphologies have been successfully synthesized by a simple hydrothermal method, using different organic amines as the morphology-controlling agents. These Cu2(OH)PO4 crystals were used as catalysts for phenol hydroxylation by H2O2, and they showed distinct activities. The sheet morphology of Cu2(OH)PO4 crystals with a large percentage of reactive facets ({011} facets) exhibited enhanced catalytic activity in hydroxylation of phenol.
- Fu, Weiwei,Wang, Runwei,Wu, Lele,Wang, Hongbin,Wang, Xu,Wang, Aijing,Zhang, Zongtao,Qiu, Shilun
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- Preparation and photocatalytic performance of silver-modified and nitrogen-doped TiO2nanomaterials with oxygen vacancies
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The photocatalysis of titanium dioxide (TiO2) exerts excellent degradation performance against contaminants in the environment. However, it prefers to absorb ultraviolet light rather than visible light, which significantly constrains its widespread use under visible light. Here, we prepared oxygen vacancy-containing TiO2viaAg-modification and N-doping. The utilization of visible light for phenol degradation was significantly enhanced by Ag/N co-doping. The characterization results showed a shuttle-like material coupled with multiple oxygen vacancies, and a well-designed experiment demonstrated that the Ti?:?N?:?Ag ratio of 1?:?0.45?:?0.32 presented optimal performance for phenol degradation. The batch experiment results also proved the modified TiO2as a potent photocatalyst against phenol degradation with an 80.8% degradation efficiency within 5 hours under visible light and with a 99.3% degradation efficiency within 2 hours under ultraviolet light. What is more, we also demonstrated that hydroxyl radical was the mainly effective radical in the mineralization of phenol and put forward a possible degradation pathway based on the observed intermediates. Lastly, the cycling tests indicated that the proposed photocatalyst is durable with a fair phenol degradation ability after recycling 5 times.
- Zhang, Hong,Jiang, Yingyu,Zhou, Baiqin,Wei, Zhuo,Zhu, Zhenya,Han, Lijuan,Zhang, Ping,Hu, Yingying
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- The photochemistry of 4-chlorophenol in water revisited: The effect of cyclodextrins on cation and carbene reactions
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The photochemistry of 4-chlorophenol (1) in water and in the presence of cyclodextrins has been studied by means of steady-state and time-resolved experiments. These have shown that 1 undergoes photoheterolysis of the C-Cl bond in the triplet state to yield the 4-hydroxyphenyl cation 32 in equilibrium with 4-oxocyclohexa-2,5-dienylidene, 33. These triplet intermediates scarcely react with a n nucleophile, such as water, nor abstract hydrogen from this solvent, thus they are long-lived (≈1 μs). Specific trapping of both intermediates has been achieved. The cation adds to 2-propenol, kadd～1.3× 108 M-1 s-1, to form the long-lived phenonium ion 11 (with λmax = 290 nm), which then converts to 3-(4-hydroxyphenyl)propane-1,2-diol (10). Carbene 33 is trapped by oxygen to give benzoquinone and is reduced by D-glucose (kq = 8.5 × 10-1 s-1) to give the phenoxyl radical (8) and phenol (9). Cyclodextrins have been found to trap the intermediates much more efficiently (kq = 9.4×10 8M-1s-1 with β-CD), which indicates that inclusion is involved. Ground state 1 forms inclusion complexes with 1:1 stoichiometry and association constants of 140 and 300 M-1 with α- and β-CD, respectively. Complexation does not change the efficiency or the mode of photofragmentation of 1; however, it does influence the course of the reaction because the major portion of the intermediates are reduced to phenol within the cavity (k′red ≥ 5 × 107 s-1) either via a radical 8 or via a radical cation 9+. Under these conditions, neither 2-propenol nor oxygen trap the intermediates to a significant extent.
- Manet, Ilse,Monti, Sandra,Bortolus, Pietro,Fagnoni, Maurizio,Albini, Angelo
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- Effective photodegradation of organic pollutantsin the presence of mono and bi-metallic complexes under visible-light irradiation
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The synthesis of new mono and bi-metallic complexes such as Zn (II) and Ag-Zn (II) complexes with organic functional group-based ligand (OFL) presented in the current work along with the exploration of their applicability in the photocatalytic degradation
- Chetti, Prabhakar,Gade, Ramesh,Guguloth, Venkanna,Pola, Someshwar,Ravulapelly, Koteshwar Rao,Subburu, Mahesh
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- Peroxomonophosphoric Acid Oxidation. 7. Studies of the Kinetics and Substituent Effect in the Oxidation of Aniline
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The kinetics of the oxidation of aniline and 12 substituted anilines by peroxomonophosphoric acid (PMPA) have been measured.The reactions are first order in PMPA and first order in amine.The rate laws are given in eq 10 and 13.The unprotonated amine is the reactive species.Correlation of log rates with ?, ?+, ?-, and ΔpKa yielded values of ρ (-1.37), ρ+ (-1.31); ρ- (-1.38), and β (0.58), respectively.The values suggest an electron-deficient reaction center, and the Bronsted coefficient, β, indicates considerable bond formation in the transition state.All the ortho substituents provide steric retardation for the formation of the transition state.Oxidation of aniline gives azobenzene, azoxybenzene, p-aminophenol, and p-benzoquinone routed through the reactive intermediate phenylhydroxylamine.The individual reactivities of various ionized PMPA species with the amine have been estimated.
- Panda, Abhina K.,Mahapatro, Surendra N.,Panigrahi, Ganesh P.
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- Two-Dimensional Layered Zinc Silicate Nanosheets with Excellent Photocatalytic Performance for Organic Pollutant Degradation and CO2 Conversion
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Two-dimensional (2D) photocatalysts are highly attractive for their great potential in environmental remediation and energy conversion. Herein, we report a novel layered zinc silicate (LZS) photocatalyst synthesized by a liquid-phase epitaxial growth route using silica derived from vermiculite, a layered silicate clay mineral, as both the lattice-matched substrate and Si source. The epitaxial growth of LZS is limited in the 2D directions, thus generating the vermiculite-type crystal structure and ultrathin nanosheet morphology with thicknesses of 8–15 nm and a lateral size of about 200 nm. Experimental observations and DFT calculations indicated that LZS has a superior band alignment for the degradation of organic pollutants and reduction of CO2 to CO. The material exhibited efficient photocatalytic performance for 4-chlorophenol (4-CP) degradation and CO2 conversion into CO and is the first example of a claylike 2D photocatalyst with strong photooxidation and photoreduction capabilities.
- Wang, Lan,Bahnemann, Detlef W.,Bian, Liang,Dong, Guohui,Zhao, Jie,Wang, Chuanyi
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- Fermy's Salt Promoted Oxidative Degradation of p-Hydroxybenzylamines and p-Hydroxybenzamides. A Novel Approach to p-Quinones
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p-Hydroxybenzylamines and primary p-hydroxybenzamides undergo oxidative degradation by the action of Fermy's salt, thus providing p-benzoquinones in good yields.
- Saa, Jose M.,Llobera, Antonia,Deya, Pedro M.
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- Electron Attachment to p-Benzoquinone and Photodetachment from Benzoquinone Anion in Nonpolar Solvents
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Although p-benzoquinone has a high electron affinity (1.9 eV), its reaction with excess electrons exhibits an unusual solvent and temperature dependence.The reaction is fast and has a positive activation energy in n-pentane but is much slower and has a negative activation energy in Si(CH3)4, neopentane, and 2,2,4,4-tetramethylpentane.The results can be explained in terms of an equilibrium with a short-lived excited state of the anion: e- + benzoquinine benzoquinone(-)*.The attachment rate is fast in all solvents.The reverse, autodetachment from the excited anion, is characterized by an activation energy, which depends on the value of V0, the energy level of the electron in the liquid.For Si(CH3)4 for which V0 is the lowest (-0.55 eV), the activation energy is 5.7 kcal/mol.As V0 increases, the activation energy increases and is 9.4 kcal/mol in 2,2,4,4-tetramethylpentane for which V0=-0.35 eV.When V0 is close to zero, as in n-pentane, the activation energy is so large that detachment from the excited anion state is too slow to compete with deactivation and a fast diffusion-controlled forward rate is observed.The spectrum of benzoquinone anion as observed by the laser photodetachment technique is reported, and the threshold for photodetachment is found to be 2.32 eV in Si(CH3)4 and 2.58 eV in 2,2,4-trimethylpentane.The quantum yield of photodetachment reaches a maximum value at 480 nm in Si(CH3)4.
- Holroyd, R. A.
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- Synthesis of binary Cu-Pd-alginates dry bead and its high catalytic activity for hydroxylation of phenol
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A series of binary Cu-Pd-alginate catalysts was prepared and their catalytic activities for phenol hydroxylation were investigated. The binary catalysts were characterized by UV-vis/DRS, FT-IR, ICP-AES, XPS, SEM and EDX measurements. The results of phenol hydroxylation illustrated that the conversions of phenol were associated with the immobilized content of the Cu2 + ions, as well the selectivities to dihydroxybenzene were determined by the immobilized content of the Pd2 + ions. The highest conversion of phenol catalyzed by Cu-Pd-ALG-30-1 was 53.9%, with selectivities to catechol and hydroquinone being 61.3% and 38.2%, respectively.
- Shi, Fengwei,Zheng, Jinlong,Xu, Kai,Zhang, Long,Hu, Jianglei
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- Kinetics and mechanism of oxidation of hydroquinone by tetrabutylammonium tribromide ion in aqueous acetic acid
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The oxidation of hydroquinone by environmentally benign tetrabutyl ammonium tribromide (TBATB) was carried out in 50% V/V aqueous acetic acid medium under pseudo-first-order conditions, keeping a large excess of hydroquinone over the oxidant. The main rea
- Zende,Kalantre,Gokavi
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- Kinetics of chlorine dioxide oxidation of benzidine in wastewater
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Reaction kinetics of benzidine oxidation with ClO2 in the wastewater were investigated systematically by detecting concentrations of benzidine with HPLC at regular intervals. The results showed that the reaction was first-order with respect to both ClO2 a
- Cao, Xiangyu
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- Oxidative degradation of phenol by corona dielectric barrier discharge at gas-liquid interphase
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In this study, corona gas-liquid dielectric barrier discharge reactor for phenol degradation was investigated. The discharge was formed between two needle metal electrodes and an aqueous solution surface where the counter electrode was submerged and separated by a quartz dielectric tube. Effects of solution conductivity, pH and gas composition on the degradation were examined. Experimental results showed that the degradation of phenol proceeded perfectly in a wide range of solution conductivity. In the process of degradation of phenol, ozone was additionally formed. The removal of phenol increased with the order: argon air oxygen. Increasing pH was favorable for phenol removal. When using argon as the discharge gas, the major degradation products were catechol, hydroquinone, hydroxyhydroquinone, acetic acid, formic acid and oxalic acid. In oxygen or air discharges, 1,4-benzoquinone and muconic acid were additionally formed. The energy efficiency of removal of phenol has been compared with other competitive processes.
- Wang, Lei,Yu, Xin,Li, Guoxin,Li, Dailin
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- On the formation of benzene oxide/oxepin in the gas-phase reaction of OH radicals with benzene
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Product formation in the gas-phase reaction of OH radicals with benzene was studied under flow-tube conditions at 13 and 100 mbar at 298 K in O2/He mixtures using direct MS, on-line FT-IR spectroscopy and GC-MS/FID detection. Benzene was used in a large excess, preventing consecutive reactions of products. Under all experimental conditions investigated there was no clear indication for a formation pathway for benzene oxide/oxepin; the observed yield was 0.03 (FT-IR) and 0.01 (GC-MS). Observed products were CO: 0.30±0.13, phenol: 0.23±0.07, formic acid: 0.13±0.05, p-benzoquinone: 0.055±0.009, and unidentified carbonyls: 0.59±0.11 (yields at 100 mbar).
- Berndt,Boege,Herrmann
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- DUET ELECTROSYNTHESIS OF p-BENZOQUINONE FROM BENZENE
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The combination of anodic oxidation of benzene using Ag(I)/Ag(II) mediator with cathodic oxidation of benzene using Cu(I)/Cu(II) mediator in a single electrolytic cell produces p-benzoquinone selectively in both anodic and cathodic chambers.
- Ito, Sotaro,Iwata, Mikio,Sasaki, Kazuo
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- Anchoring of Fe(III)salicylamide onto MCM-41 for catalytic hydroxylation of phenol in aqueous medium using hydrogen peroxide as oxidant
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Fe(III)salicylamide immobilized on MCM-41 has been developed for hydroxylation of phenol in water medium using hydrogen peroxide as the oxidant. In the first step, the amine group containing 3-aminopropyltrimethoxy silane has been immobilized on the surface of MCM-41 via co-condensation. The amine group upon condensed with methyl salicylate afford a bidentate ligand in the mesoporous matrix for anchoring Fe(III) ions in the second step. Small angle XRD, N2 adsorption-desorption isotherms, 13C and 29Si cross-polarization magic angle spinning NMR spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance UV-vis spectra were employed for the characterization of the catalysts. The heterogeneous iron salicylamide complex shows excellent catalytic activity in phenol hydroxylation using hydrogen peroxide as the oxidant and water as the solvent. Notably, phenol shows high conversion (64.6%) with very high selectivity for dihydroxybenzene compounds. The heterogeneous catalyst shows a successive slight decrease in catalytic activity when reused for three more times. Graphical Abstract: Fe(III)salicylamide-MCM-41 has been synthesized successfully through an easy co-condensation route. XRD and N2 adsorption-desorption showed mesoporosity is retained even after complexation and FT-IR and diffuse reflectance UV-vis spectra confirmed the formation of complex. The heterogeneous catalyst exhibit excellent catalytic performance and stability in phenol hydroxylation reaction for the formation of dihydroxybenzene derivatives using H2O2.
- Parida,Singha, Sudarshan,Sahoo
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- An efficient method for the oxidation of phenolic compounds using new Co(II) and Fe(II) phthalocyanines
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In this study novel Co(II) and Fe(II) phthalocyanines have been successfully prepared and their structural characterization have been done using with different spectroscopic methods (IR, 1H-NMR, UV–Vis, mass spectroscopies and elemental analysis). Substituted phenolic compounds as substrate, different kinds of oxidants and novel Co(II) and Fe(II) phthalocyanines as catalyst have been used in all oxidation reactions. Temperature, different oxidants, ox./cat. ratio effects on the catalysis have been determined. Interestingly, Co(II) phthalocyanine exhibits superior catalytic activity and durability in the catalysis over oxidation of p-nitrophenol (4-NP). The present method is simple, environmentally benign and amenable scale up process.
- Saka, Ece Tugba,?elik, Gonca,Sark?, Gülb?nar,Kantekin, Halit
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- Catalytic effect of active carbon black Chezacarb in wet oxidation of phenol
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The catalytic effects of hydrophilic granulated active carbon black Chezacarb have been tested in the oxidation of dilute (5 000 ppm) aqueous solutions of phenol. The research was focused on combined utilization of sorption and chemical (oxygen functional groups) properties of carbon black which support formation of free radicals in oxidation and on the catalytic effects of metals (Fe, Ni and V) present in the sorbent mentioned. The oxidation was carried out in a stainless steel autoclave of 1.25 1 capacity. The reaction temperatures and the total pressures varied in the intervals of 120-160 °C and 3-5 MPa, respectively. The reaction mixture was analyzed by means of HPLC with UV detection (254 nm). The experimental data were evaluated by means of the ASPEN PLUS 9.2 program. The model of laboratory autoclave involved the reaction kinetics as well as the phase equilibria and dissolution of oxygen and carbon dioxide in the reaction mixture. Although the active carbon black shows a lower catalytic activity than the usual copper catalyst in the wet oxidation, it has the advantage of avoiding the undesirable releases of heavy metals in waste waters, which escapes accompany the application of copper catalysts.
- Tukac, Vratislav,Hanika, Jiri
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- Sulfonic-functionalized MIL-101 as bifunctional catalyst for cyclohexene oxidation
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Metal-organic frameworks (MOFs) are newly emerging and versatile platforms for designing catalysts, and catalytic oxidation of cyclohexene has attracted much academic and industrial attention for the versatile reactivity of the substrate and the great importance of the various oxygenated products. Here we report the bifunctional catalytic properties of a sulfonic-containing MOF, MIL-101-SO3H, for cyclohexene oxidation. The sulfonic group and the Cr(III) site acts in a complementary or collaborative way. The Cr(III) framework promotes the oxidation to 3-hydroperoxycyclohex-1-ene (perox) and 2-cyclohexen-1-one (1-one) (route A), whereas the sulfonic group in collaboration with the Cr(III) framework promotes the oxidation to diol (route B) and also enhances further conversions in route A: from perox to 1-one, to 2-cyclohexen-1,4-dione (dione) and even to benzoquinone. With the bifunctional MOF, molecular oxygen alone cannot oxidize cyclohexene but participates as oxidant cooperating with tert-butyl hydroperoxide (TBHP) to accelerate the reactions and to alter the product distribution in favor of dione.
- Sun, Weng-Jie,Gao, En-Qing
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- Immobilization of tyrosinase on Fe3o4@Au core–shell nanoparticles as bio-probe for detection of dopamine, phenol and catechol
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Abstract: An optical bio-probe based on the immobilized tyrosinase on the surface of Fe3O4@Au was described for the detection of dopamine, phenol and catechol. The prepared bio-probe (Fe3O4@Au@tyrosinase) was characterized by means such as TEM, SEM, VSM, DLS and TGA. In the presence of the bio-probe, the phenol, catechol and dopamine were converted to benzoquinone, o-quinone and dopaquinone, and the fluorescence spectra appeared at 308?nm, 329?nm and 336?nm with ex?=?270?nm, respectively. However, by increasing the concentration of phenolic compounds in the bio-probe, the amount of products (benzoquinone, o-quinone and dopaquinone) was increased which was the reason for the increase in fluorescence intensity. Using this mechanism, a bio-probe was designed such that the intensity of the fluorescence spectra increased proportionally with the increase of the substrate concentrations after different time periods. The 0.003?mg/mL of tyrosinase was loaded on 1.65?mg/mL of the Fe3O4@Au. The highest performance for a bio-probe was demonstrated at room temperature and pH 6.8. By investigating the characteristics of the response of the bio-probe to different phenolic compounds, it was found that the bio-probe had a linear response in the concentration range 5.0–75.0?μM, 10.0–100.0?μM for phenol and dopamine and 50.0–500.0?M for catechol. The Michaelis–Menten constant (Km) of the bio-probe was calculated as 0.6?μM. Finally, the bio-probe seems to be stable and efficient even after about 2 months. Graphic abstract: A novel and easy method for the detection of dopamine, phenol and catechol by florescence that uses oxide capability to identify the phenolic compounds was introduced.[Figure not available: see fulltext.].
- Arkan, Elham,Karami, Changiz,Rafipur, Ronak
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- Direct synthesis of phenol from benzene catalyzed by multi-V-POMs complex
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A novel catalyst, [Mo2V2O9(bpy) 6][PMo11VO40], was synthesized by the self-assembling of [PMo11VO40]4- and [Mo 2V2O9(bpy)6]4+ unit and characterized by elemental analyses, TG, IR, X-ray powder diffraction and X-ray single crystal diffraction. [Mo2V2O9(bpy) 6][PMo11VO40] with multi-isolated active sites showed good catalytic activities for hydroxylation of benzene to phenol. A high yield of phenol (25.5%) with selectivity to phenol of 90.7% was obtained using H2O2 as oxidant. The catalyst can be recycled for 5 times while its structure was unchanged and its catalytic activity was maintained.
- Yang, Hua,Wu, Qing,Li, Jun,Dai, Wen,Zhang, Hengyun,Lu, Dan,Gao, Shuang,You, Wansheng
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- Catalytic Oxidation of Naphthalene on Palladium in Cooperation with Copper(I)/(II) Redox Couple
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Catalytic oxidation of naphthalene in moist acetic acid solutions has been studied.The catalyst used was a silica-supported palladium which works in cooperation with the Cu(1+)/Cu(2+) redox couple.Products were 1-naphthol, 1,4-naphthoquinone and (E)-2-formylcinnamaldehyde with a total yield of more than 78percent in which naphthoquinone shared 40percent.Reaction mechanism has been discused in comparison with that of benzene.
- Kuroda, Yasushi,Kunai, Atsutaka,Hamada, Michiyuki,Kitano, Tomoyuki,Ito, Sotaro,Sasaki, Kazuo
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- Oxidative degradation of monomeric and dimeric phenylpropanoids: Reactivity and mechanistic investigation
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The oxidative degradation of lignin related model compounds catalysed by [N,N'-bis(salicylidene)ethane-1,2-diaminato]cobalt(II), [Co(salen)], have been studied in chloroform. Arylglycerol β-aryl ethers, phenylcoumarans and apocynol showed very high conversion values within 30 minutes of the start of the reaction and their conversion rates were higher than those reported for phenylpropenoidic compounds, methyl (E)-ferulate and methyl (E)-4-hydroxycinnamate. The results of the CW electron paramagnetic resonance (EPR) investigation using the X-band, performed at the reaction temperature (298 K) showed that two phenoxy cobalt radicals ([CoIII(salen)(ROH)(RO·)] and [CoIII(salen)(RO-)(RO·)]) are involved in the oxidation mechanism of all the phenol compounds ROH. In a frozen solution the [CoIII(salen)(ROH))(RO·)] radical prevailed and its axial magnetic anisotropy was determined using high frequency, 190 GHz, CW EPR spectra. The X-band EPR monitoring of the phenoxy cobalt radicals during the reaction showed a faster decrease in the amounts of radical in the oxidation of propanoidic phenols compared with that of propenoidic phenols. The lifetime of the radicals formed from substrates having a methoxy group ortho to the aromatic hydroxy was also shorter than from substrates lacking this functionality. Both reactivity and spectroscopic data suggest that the lifetime of the phenoxy cobalt radicals correlates with the conversion rates of the substrates.
- Canevali, Carmen,Orlandi, Marco,Pardi, Luca,Rindone, Bruno,Scotti, Roberto,Sipila, Jussi,Morazzoni, Franca
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- Degradation of substituted phenols with different oxygen sources catalyzed by Co(II) and Cu(II) phthalocyanine complexes
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Research on substituted phenol degradations has received substantial attention. In this work, effective Co(II) and Cu(II) phthalocyanine complexes as catalysts were studied to degrade toxic phenols to harmless products. The effect of various process parameters, such as initial concentration of phenol, catalyst, oxygen sources, and temperature on the degradation reaction was investigated to achieve maximum degradation efficiency. The catalytic activities of Co(II) and Cu(II) phthalocyanines were evaluated for oxidation of phenolic compounds such as p-nitrophenol, o-chlorophenol, 2,3-dichlorophenol, and m-methoxyphenol. Co(II) phthalocyanine displayed good catalytic performance in degradation of 2,3-dichlorophenol to 2,3-dichlorobenzaldehyde and 2,3-dichloro-1,4-benzoquinone with the highest TON and TOF values within 3 h at 50 °C. The fate of catalyst during the degradation process was followed by UV–Vis spectroscopy.
- Saka, Ece Tugba,Dügdü, Esra,ünver, Yasemin
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- Application of photoactive electrospun nanofiber materials with immobilized meso-tetraphenylporphyrin for parabens photodegradation
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The pollution of aqueous environment by trace amounts of anthropogenic chemical substances has a hazardous impact on regular development of plants and animals as well as on human health. The paper presents the results of studies on the heterogeneous degradation of butyl- and benzylparaben in aqueous solutions using photochemically catalyzed processes. Meso-tetraphenylporphyrin (TPP) was immobilized in the polyurethane nanofiber material by electro-spinning method. The xenon lamp was used as a simulated sunlight source. The influence of various process parameters on reaction rate was investigated. The reuse of the carrier with the immobilized photosensitizer was examined. The major role of the singlet oxygen (1Δg) during the photodegradation was proved by using sodium azide and radical scavengers. The adsorption isotherms of parabens onto nanofiber material were determined using BET model. The kinetic study showed that the heterogeneous photodegradation of parabens could be modeled using Langmuir-Hinshelwood model and rate constants have been reported. The reaction pathway for the photodegradation of parabens via 1Δg was proposed.
- Gmurek,Bizukoj?,Mosinger,Ledakowicz
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- Photooxidation in water by new hybrid molecular photocatalysts integrating an organic sensitizer with a polyoxometalate core
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Hybrid compounds consisting of an organic sensitizer and a polyoxometalate unit were synthesized following two strategies: a) the covalent functionalization of lacunary decatungstosilicate with organosilylfulleropyrrolidines; b) the charge interaction between cationic sensitizers and the polyoxoanions, yielding electrostatic aggregates. These hybrid complexes effect catalytic photooxygenation in water under heterogeneous conditions, 25°C and O2 (1 atm), using visible light irradiation (λ>375 nm). As representative target substrates, phenol (4 mM) is oxidized in 150 min with a COD loss up to 30% (TON up to 50), while L-methionine methyl ester (15 mM) undergoes selective photooxygenation to the corresponding sulfoxide in 90 min (TON up to 200). The photocatalyst stability has been evaluated on the basis of system recycling along three oxidation runs. The inhibition exerted by sodium azide, a typical 1O2 quencher, suggests the occurrence of a Type II photooxidation mechanism.
- Bonchio, Marcella,Carraro, Mauro,Scorrano, Gianfranco,Bagno, Alessandro
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- Promoting Effect of TiO2 and Al2O3 Supports on the Activity of Vanadium Oxide Catalyst for the Oxidation of Benzene Measured in Terms of the Turnover Frequency
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The following relationship, V2O5-TiO2 > unsupported V2O5 > V2O5-Al2O3, was found to hold for the turnover frequency for the oxidation of benzene, which indicates the promoting effect of the TiO2 support on the reaction with vanadium oxide catalyst.
- Inomata, Makoto,Miyamoto, Akira,Murakami, Yuichi
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- Synthesis of iron orthophosphate catalysts by solution and solution combustion methods for the hydroxylation of benzene to phenol
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Iron orthophosphate was prepared by solution and solution combustion method for use as a catalyst in the hydroxylation of benzene to phenol. The products of each method were structurally identical. The morphology and size of the catalyst were significantly influenced by the synthesis method. The catalytic activity of the catalysts in the liquid phase hydroxylation of benzene was studied. The yields of the solution combustion synthesized and solution synthesized iron orthophosphate were 24.52% and 8.90%, respectively, under optimized conditions. The iron orthophosphate synthesized by the solution combustion method exhibited better catalytic performance characteristics than the one prepared by the solution method.
- Baykan, Demet,Oztas, Nursen Altuntas
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- Electrochemically-induced spirolactonization of α-(methoxyphenoxy)alkanoic acids into quinone ketals
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Anodic oxidation of two series of α-(2)- and α-(4-methoxyphenoxy)alkanoic acids were studied both at the analytical and preparative scales in order to delineate mechanistic aspects of electrochemically induced spirolactonization and to develop synthetically useful orthoquinone bis- and monoketals. Although α-monomethylated carboxylic acids and acetic acid derivatives do not undergo any spiroannulation, α-dimethylated carboxylic acids furnished spirolactones in high yields. A gem-dimethyl effect is invoked to explain these differences in cyclization capacity. Electrooxidation conditions can be selected to furnish either quinone spirolactone bis- or monoketals. Chemoselective monohydrolysis of bisketals can also be accomplished in a stepwise fashion to furnish the corresponding spirolactone monoketals, but the ortho compound unfortunately dimerized in situ via a Diels-Alder process. An ECEC pathway is proposed to rationalize the observed spirolactonizations on the basis of cyclic voltammetry analyses.
- Deffieux, Denis,Fabre, Isabelle,Courseille, Christian,Quideau, Stephane
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- A Chemo-Enzymatic Cascade for the Smart Detection of Nitro- and Halogenated Phenols
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The flavin-dependent monooxygenase, HadA, catalyzes the dehalogenation and denitration of the toxicants, nitro- and halogenated phenols, to benzoquinone. The HadA reaction can be applied in one-pot reactions towards the de novo synthesis of d-luciferin by coupling with d-Cys condensation. d-luciferin, a valuable chemical widely used in biomedical applications, can be used as a substrate for the reaction of firefly luciferase to generate bioluminescence. As nitro- and halogenated phenols are key indicators of human overexposure to pesticides and pesticide contamination, the technology provides a sensitive and convenient tool for improved biomedical and environmental detection at ppb sensitivity in biological samples without the requirement for any pre-treatment. This dual-pronged method combines the advantages of waste biodetoxification to produce a valuable chemical as well as a smart detection tool for environmental and biomedical detection.
- Watthaisong, Pratchaya,Pongpamorn, Pornkanok,Pimviriyakul, Panu,Maenpuen, Somchart,Ohmiya, Yoshihiro,Chaiyen, Pimchai
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- Degradation of p-nitrophenol using CuO/Al2O3 as a Fenton-like catalyst under microwave irradiation
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CuO/Al2O3 was synthesized successfully by the impregnation-deposition method and used as a heterogeneous catalyst in a microwave assisted Fenton-like process (MW/FL). The morphology and physico-chemical properties of the CuO/Al2O3 catalyst were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. The degradation of p-nitrophenol (PNP) was investigated by different processes, including microwave irradiation (MW) alone, hydrogen peroxide (H2O2) oxidation under microwave irradiation without the catalyst (MW/H2O2), a Fenton-like (FL) process, a MW/FL process and a thermally-assisted Fenton-like (TH/FL) process. The results showed that the CuO/Al2O3 catalyzed MW/FL could generate more hydroxyl radicals (OH) and remove PNP more effectively compared to other processes. The effects of initial pH, dosage of H2O2 and catalyst, microwave power and radiation time, and PNP concentration on the removal efficiency were also studied. The results showed that 93% removal efficiency of PNP was obtained within 6 min under optimized conditions. Moreover, the catalyst had a good stability and reusability, thus expanding the scope of non-iron based catalysts in the Fenton-like reactions.
- Pan, Weiqian,Zhang, Guangshan,Zheng, Tong,Wang, Peng
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- Electron-transfer oxidation of chlorophenols by uranyl ion excited state in aqueous solution. Steady-state and Nanosecond flash photolysis studies
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The oxidation of chlorophenols by photoexcited uranyl ion was studied in aqueous solution at concentrations where the ground-state interactions were negligible. Nanosecond flash photolysis showed that a clean electron-transfer process from the chlorophenols to the excited uranyl ion is involved. This is suggested to lead to the formation of a U(V)/chlorophenoxyl radical pair complex. The efficiency of this charge-transfer process is unity for the three chlorophenols. However, low product yields suggest that in the absence of oxygen, back electron transfer, both within the radical pair and from separated uranium(V) to phenoxyl radicals, appears to be the major reaction pathway. In the presence of oxygen the quantum yields of disappearance of chlorophenol and of photoproduct formation increased. This leads to the conclusion that oxygen favors reaction with uranium(V) and/or the uranium(V) - phenoxyl radical pair, leading to the formation of the superoxide anion and its conjugate acid, HO2*, which then regenerate UO22+. Based on this, a catalytic cycle for chlorophenol photooxidation involving uranyl ion and molecular oxygen is proposed.
- Sarakha, Mohamed,Bolte, Michele,Burrows, Hugh D.
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- Electrochemical incineration of 4-chlorophenol and the identification of products and intermediates by mass spectrometry
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This report summarizes results obtained as part of a larger effort to demonstrate the applicability of electrolytic procedures for the direct anodic (oxidative) degradation of toxic organic wastes. We refer to this process as "electrochemical incineration" (ECI) because the ultimate degradation products, e.g., carbon dioxide, are equivalent to those achieved by thermal incineration processes. In this work, the ECI of 4-chlorophenol is achieved in an aqueous medium using a platinum anode coated with a quaternary metal oxide film containing Ti, Ru, Sn, and Sb oxides. The electrode is stable and active when used with a solid Nafion membrane without the addition of soluble supporting electrolyte. Liquid chromatography (LC), including reverse phase and ion exchange chromatography, is coupled with electrospray mass spectrometry (ES-MS) and used, along with gas chromatography-mass spectrometry (GC-MS) and measurements of pH, chemical oxygen demand (COD), and total organic carbon (TOC), to study the reaction and identify the intermediate products from the ECI of 4-chlorophenol. Twenty-six intermediate products are identified and reported. The most abundant of these products are benzoquinone, 4-chlorocatechol, maleic acid, succinic acid, malonic acid, and the inorganic anions chloride, chlorate, and perchlorate. After 24 h of ECI, a solution that initially contained 108 ppm 4-chlorophenol yields only 1 ppm TOC with 98% of the original chlorine remaining in the specified inorganic forms. LC-ES-MS and direct infusion ES-MS detection limits are between 80 ppb and 4 ppm for these intermediate products. Elemental analysis of the electrolyzed solutions by inductively coupled plasma mass spectrometry ICP-MS showed that only trace amounts (25 ppb) of the metallic elements comprising the metal oxide film were present in the solution.
- Johnson, Steve K.,Houk, Linda L.,Feng, Jianren,Houk,Johnson, Dennis C.
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- Photocatalytic transformation of chlorophenols under homogeneous and heterogeneous conditions using palladium octadodecylthio phthalocyanine
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Homogeneous and heterogeneous photosensitized transformations of 4-chlorophenol (4-CP) and pentachlorophenol (PCP) using palladium octadodecylthiophthalocyanine (PdODPc) were investigated. Under heterogeneous conditions, the photosensitizer was supported on functionalized single walled carbon nanotubes (SWCNTs). Homogeneous photosensitization proved to be more effective than the heterogeneous reaction in terms of percentage of transformation achieved. The kinetics of heterogeneous catalysis proved that ads-PdODPc-SWCNT-COOH (where SWCNT has been functionalized with COOH groups) was reusable for 4-CP while its activity degenerated when reused for PCP. Singlet oxygen was confirmed as playing an active role in the reactions.
- Ogunbayo, Taofeek B.,Nyokong, Tebello
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- Hydrolysis of N-Acetyl-p-benzoquinone Imines: pH Dependence of the Partitioning of a Tetrahedral Intermediate
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The hydrolysis reactions of N-acetyl-p-benzoquinone imine, 1a, and its 3,5- and 2,6-dimethyl analogues, 1b and 1c, in the pH range 0.3-10.5 are described.At pH 6.0 the carbinolamide intermediates 2a-c can be detected by 1H NMR, UV, and HPLC methods.The pH-dependent partitioning of 2a and 2c can be monitored since the reversion of these intermediates to the protonated N-acylimines 5a and 5c leads to products of the conjugate attack of Cl(-), the 3-chloroacetaminophen derivatives 4a and 4c.A mechanism for the hydrolysis of 1a-c (Scheme I) is proposed which accurately predicts the time dependence of the formation of 2 and the final hydrolysis products, the p-benzoquinones 3, and 4.The alternative O-protonation mechanism (Scheme II) is tentatively rejected on the basis of substituent effect data.The relationship of the hydrolysis reactions of 1a-c to those of ordinary imines is discussed.
- Novak, Michael,Bonham, Gayl A.,Mulero, Julio J.,Pelecanou, Maria,Zemis, Joseph N.,et al.
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- Thermodynamics of Disproportionation and Heats of Hydration of 1,4-Benzosemiquinone and 1,4-Naphthosemiquinone at pH 7.1
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The thermodynamics of disproportionation of 1,4-benzosemiquinone (BQ*-) and 1,4-naphthosemiquinone (NQ*-) in cacodylic-cacodylate buffer at pH 7.1 was studied by spin resonance (ESR) spectroscopy and solution calorimetry.The disproportionation of BQ*- was found to be more exergonic and exothermic than that corresponding to NQ*- in both aqueous and gas phases.These semiquinones disproportionate about 40 times more exothermically in the gaseous than in the aqueous phase.The differences between the enthalpies of disproportionation corresponding to BQ*- and NQ*- are 51 and 14 kJ/mol in the gaseous and aqueous phases, respectively.The heats of hydration of BQ*- and NQ*- were determined with a convenient thermochemical cycle based on the enthalpies of disproportionation.The single-ion heats of hydration of BQ*- and NQ*- were found to be -360 and -377 kJ/mol, respectively.The heats of hydration of the net negative charge in BQ*- and NQ*- were found to be the same.
- Alegria, Antonio E.,Munoz, Carlos,Rodriguez, Maria S.
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- New Way of Hydroquinone and Catechol Synthesis using Nitrous Oxide as Oxidant
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The synthesis of dihydroxybenzenes (DHB) via the gas-phase oxidation of phenol with nitrous oxide in the presence of benzene was studied. Addition of benzene to the feed mixture greatly improves the selectivity and catalytic stability of the Fe-containing
- Ivanov,Sobolev,Pirutko,Panov
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- On the photocatalytic degradation of phenol and dichloroacetate by BiVO4: The need of a sacrificial electron acceptor
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The photodegradation of phenol and dichloroacetic acid (DCAA) by BiVO 4 was studied in the absence as well as presence of selected electron scavengers. The experiments were performed under the visible (vis) irradiation of aqueous solutions over a wide pH range (1-13). Phenol was photocatalytically degraded by BiVO4 into p-benzoquinone below pH 3 and into an open-ring structure at pH 13. Methylene blue (MB) accelerated the reaction below the isoelectric point of BiVO4 and did not undergo significant degradation. In presence of H2O2, phenol was rapidly degraded up to pH 9. The degradation rates are two orders of magnitude higher than in absence of electron scavenger. The degradation of dichloroacetic acid was only possible in presence of H2O2. High initial concentrations of H2O2 inhibit the reaction and its consumption is very fast. Sequential additions of this sacrificial electron acceptor (SEA) enables the total degradation of a 1 mM DCAA solution.
- Castillo, Nikola C.,Ding, Laura,Heel, Andre,Graule, Thomas,Pulgarin, Cesar
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- Synthesis and characterization of a new fluorescent probe for reactive oxygen species
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We report the development of a new fluorescence sensor for reactive oxygen species (ROS) based on a benzofurazan structure. The sensor, NBFhd, is initially non-fluorescent and reacts with peroxyl radicals by hydrogen transfer in an aqueous medium under neutral conditions to release the fluorescent N-methyl-4-amino-7-nitrobenzofurazan (NBF) and 1,4-benzoquinone. NBFhd shows excellent contrast and no interference in the region of cell autofluorescence and is a new tool to detect ROS in homogeneous and biological systems. This journal is The Royal Society of Chemistry.
- Heyne, Belinda,Beddie, Chad,Scaiano
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- Direct catalytic benzene hydroxylation under mild reaction conditions by using a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups
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Direct catalytic hydroxylation of benzene under mild reaction conditions proceeded efficiently in the presence of a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups in an acetonitrile solution with excess H2O2. Mechanistic studies suggested that the reaction was catalyzed by a high-valent iron-oxo species generated in situ. Moreover, the peripheral methyl groups of the catalyst were presumed to have enhanced the production rate of the iron-oxo species.
- Tanaka, Kentaro,Teoh, Chee-Ming,Toyoda, Yuka,Yamada, Yasuyuki
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supporting information
p. 955 - 958
(2022/02/07)
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- Photocatalytic removal of benzene over Ti3C2T: XMXene and TiO2-MXene composite materials under solar and NIR irradiation
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MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2-MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol-gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors.
- Calvino, José J.,Constantinescu, Gabriel,Frade, Jorge R.,Kovalevsky, Andrei V.,Labrincha, Jo?o A.,Lajaunie, Luc,Lopes, Daniela V.,Sergiienko, Sergii A.,Shaula, Aliaksandr L.,Shcherban, Nataliya D.,Shkepu, Viacheslav I.,Tobaldi, David M.
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p. 626 - 639
(2022/01/22)
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- Electrochemical Strategy for the Simultaneous Production of Cyclohexanone and Benzoquinone by the Reaction of Phenol and Water
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Cyclohexanone and benzoquinone are important chemicals in chemical and manufacturing industries. The simultaneous production of cyclohexanone and benzoquinone by the reaction of phenol and water is an ideal route for the economical production of the two c
- Wu, Ruizhi,Meng, Qinglei,Yan, Jiang,Liu, Huizhen,Zhu, Qinggong,Zheng, Lirong,Zhang, Jing,Han, Buxing
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p. 1556 - 1571
(2022/02/01)
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- Aromatic C?H Hydroxylation Reactions with Hydrogen Peroxide Catalyzed by Bulky Manganese Complexes
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The oxidation of aromatic substrates to phenols with H2O2 as a benign oxidant remains an ongoing challenge in synthetic chemistry. Herein, we successfully achieved to catalyze aromatic C?H bond oxidations using a series of biologically inspired manganese catalysts in fluorinated alcohol solvents. While introduction of bulky substituents into the ligand structure of the catalyst favors aromatic C?H oxidations in alkylbenzenes, oxidation occurs at the benzylic position with ligands bearing electron-rich substituents. Therefore, the nature of the ligand is key in controlling the chemoselectivity of these Mn-catalyzed C?H oxidations. We show that introduction of bulky groups into the ligand prevents catalyst inhibition through phenolate-binding, consequently providing higher catalytic turnover numbers for phenol formation. Furthermore, employing halogenated carboxylic acids in the presence of bulky catalysts provides enhanced catalytic activities, which can be attributed to their low pKa values that reduces catalyst inhibition by phenolate protonation as well as to their electron-withdrawing character that makes the manganese oxo species a more electrophilic oxidant. Moreover, to the best of our knowledge, the new system can accomplish the oxidation of alkylbenzenes with the highest yields so far reported for homogeneous arene hydroxylation catalysts. Overall our data provide a proof-of-concept of how Mn(II)/H2O2/RCO2H oxidation systems are easily tunable by means of the solvent, carboxylic acid additive, and steric demand of the ligand. The chemo- and site-selectivity patterns of the current system, a negligible KIE, the observation of an NIH-shift, and the effectiveness of using tBuOOH as oxidant overall suggest that hydroxylation of aromatic C?H bonds proceeds through a metal-based mechanism, with no significant involvement of hydroxyl radicals, and via an arene oxide intermediate. (Figure presented.).
- Masferrer-Rius, Eduard,Borrell, Margarida,Lutz, Martin,Costas, Miquel,Klein Gebbink, Robertus J. M.
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p. 3783 - 3795
(2021/03/09)
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- Hydroxylation of benzene to phenol over heteropoly acid H5PMo10V2O40supported on amine-functionalized MCM-41
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Supported catalysts with Keggin type heteropoly acids (H5PMo10V2O40) loaded onto amine-functionalized MCM-41 for the catalytic hydroxylation of benzene to phenol with H2O2were prepared by a wet impregnation method. The effects of the preparation conditions on the properties and activity of the supported catalysts were fully investigated. The results showed that the catalyst retained the mesoporous structure of MCM-41 and H5PMo10V2O40was dispersed uniformly on the surface of the amine-functionalized MCM-41. Meanwhile, the reusability and catalytic performance of the catalyst were affected by two key factors,i.e., the interaction between the heteropoly acid and the surface of MCM-41, and the hydrophobicity of the catalyst since they decide the leaching of H5PMo10V2O40and the adsorption of benzene. The catalyst with H5PMo10V2O40loaded onto amine-functionalized MCM-41, which was prepared using ethanol as the solvent, exhibited the highest phenol yield (20.4%), a turnover frequency value of 20.3 h?1and good reusability. We believe this work offers an effective and facile strategy for the preparation of a new catalyst for hydroxylation of benzene to phenol.
- Kong, Yan,Li, Shichao,Li, Yanjun
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p. 26571 - 26580
(2021/08/17)
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- Direct Acetoxylation of Arenes
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Acetoxylation of arenes is an important reaction and an unmet need in chemistry. We report a metal-free, direct acetoxylation reaction using sodium nitrate under an anhydrous environment of trifluoroacetic acid, acetic acid, and acetic anhydride. Arenes (31 examples), with oxidation potentials (Eox, in V vs SCE) lower than benzene (2.48 V), were acetoxylated with good yields and regioselectivity. A stepwise, single electron-transfer mechanism is proposed.
- Hong Nguyen, Thi Anh,Hou, Duen-Ren
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supporting information
p. 8127 - 8131
(2021/08/23)
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- Oxidative Dearomatization of Phenols and Polycyclic Aromatics with Hydrogen Peroxide Triggered by Heterogeneous Sulfonic Acids
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We report herein a method for the oxidative dearomatization of phenols and bare polycyclic arenes into the corresponding quinoid derivatives using hydrogen peroxide. The reaction is catalyzed by sulfonic acids and best results were achieved using heterogenized species. The best results using phenols were achieved using a hybrid material, namely a perfluorinated polymer functionalized with sulfonic acid groups supported on silica. The dearomatization of polycyclic aromatic hydrocarbons performed better using the polymeric acid catalyst. These methods operate under mild conditions, using mild and benign oxidants and thus minimizing the formation of waste.
- Pancrazzi, Francesco,Maestri, Giovanni,Maggi, Raimondo,Viscardi, Rosanna
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supporting information
p. 5407 - 5414
(2021/10/25)
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- One-Pot Transformation of Hypervalent Iodines into Diversified Phenoxazine Analogues as Promising Photocatalysts
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A facile and efficient quinoline-fused 4H-benzo[b][1,4]oxazine has been successfully fabricated through an oxidative O-arylation, Pd-catalyzed double N-arylation of 4-hydroxyquinoline derivatives and trivalent aryl iodides. Diversified fused heterocycles could be easily constructed in overall high isolated yields with great substrate scope. The afforded heteroatom-"doped"phenoxazine 3 demonstrated high molar absorptivities and excellent stability and redox reversibility. These phenoxazine analogues therefore could be utilized as promising catalysts in the photoredox catalyzed perfluoroalkylation of heteroarenes and photopromoted radical polymerization (OATRP).
- Cheng, Jiajia,Huang, Liangsen,Xiao, Hongxiang,Jiang, Shulin
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supporting information
p. 15792 - 15799
(2021/11/01)
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- Method for preparing p-benzoquinone through catalytic oxidation of 1, 4-benzenediol
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The invention discloses a method for preparing p-benzoquinone through catalytic oxidation of 1, 4-benzenediol. The method comprises the following steps: carrying out centrifugal treatment on mother liquor for preparing 2, 3-dicyanohydroquinone; adding the centrifuged mother liquor and sodium hypochlorite into a micro-channel reactor; sequentially mixing and stirring the to-be-reacted liquid added into the microchannel reactor, and then crystallizing and filtering; and adding water into solid phase benzoquinone obtained after crystallization treatment for washing to obtain a p-benzoquinone product. According to the invention, the problem of waste of raw materials caused by conversion of the raw materials into 1, 4-benzenediol in the preparation process of 2, 3-dicyanohydroquinone at present is solved.
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Paragraph 0039-0055
(2021/07/28)
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- Electrochemical-In-Situ-Oxidative Sulfonylation of Phenols with Sulfinic Acids as an Access to Sulfonylated Hydroquinones
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The electrochemical in-situ oxidative sulfonylation of phenols with sulfinic acids access to sulfonylated hydroquinones has been developed. A series of sulfonylated hydroquinones were prepared under mild mediator-, catalyst- and exogenous-oxidant-free con
- Sun, Xue,Zhang, Fanjun,Yan, Kelu,Feng, Wenfeng,Sun, Xuejun,Yang, Jianjing,Wen, Jiangwei
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supporting information
p. 3485 - 3490
(2021/06/17)
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- PHOTOOXIDATION OF 2,3,6-TRIMETHYLPHENOL
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The present invention relates to the photooxidation of 2,3,6-trimethyl- phenol to yield 2,3,5-trimethylbenzoquinone using methylene blue as photo- sensitizer in a solvent mixture of water and alcohols using light of the high wave- length range of the visible spectrum.
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Page/Page column 14-15
(2021/11/26)
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- PHOTOOXIDATION OF PHENOLIC COMPOUNDS
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The present invention relates to the photooxidation of phenolic compounds to the respective quinoid compounds using methylene blue as photosensitizer in a solvent mixture of water and alcohols using light of the high wavelength range of the visible spectrum.
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Page/Page column 17-18
(2021/11/26)
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- PHOTOOXIDATION OF 2,3,5-TRIMETHYLPHENOL
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The present invention relates to the photooxidation of 2,3,5-trimethyl- phenol to yield 2,3,5-trimethylbenzoquinone using methylene blue as photo- sensitizer in a solvent mixture of water and alcohols using light of the high wavelength range of the visible spectrum.
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Page/Page column 14-17
(2021/11/26)
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- Oxidative degradation of toxic organic pollutants by water soluble nonheme iron(iv)-oxo complexes of polydentate nitrogen donor ligands
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The ability of four mononuclear nonheme iron(iv)-oxo complexes supported by polydentate nitrogen donor ligands to degrade organic pollutants has been investigated. The water soluble iron(ii) complexes upon treatment with ceric ammonium nitrate (CAN) in aqueous solution are converted into the corresponding iron(iv)-oxo complexes. The hydrogen atom transfer (HAT) ability of iron(iv)-oxo species has been exploited for the oxidation of halogenated phenols and other toxic pollutants with weak X-H (X = C, O, S,etc.) bonds. The iron-oxo oxidants can oxidize chloro- and fluorophenols with moderate to high yields under stoichiometric as well as catalytic conditions. Furthermore, these oxidants perform selective oxidative degradation of several persistent organic pollutants (POPs) such as bisphenol A, nonylphenol, 2,4-D (2,4-dichlorophenoxyacetic acid) and gammaxene. This work demonstrates the utility of water soluble iron(iv)-oxo complexes as potential catalysts for the oxidative degradation of a wide range of toxic pollutants, and these oxidants could be considered as an alternative to conventional oxidation methods.
- Jana, Rahul Dev,Munshi, Sandip,Paine, Tapan Kanti
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supporting information
p. 5590 - 5597
(2021/05/04)
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- Benzoic acid resin (BAR): a heterogeneous redox organocatalyst for continuous flow synthesis of benzoquinones from β-O-4 lignin models
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A polymer-bound organocatalyst for Baeyer-Villiger reaction and phenol oxidation under continuous flow conditions is described for the first time.BARhas revealed two catalytic activities that enabled the generation of a novel approach for the synthesis of benzoquinones from β-O-4 lignin models in a one-pot protocol. High catalytic activities (yields up to 98%), selectivities, recyclability and productivity were achieved.
- Dias, Kevin de Aquino,Pereira Junior, Marcus Vinicius Pinto,Andrade, Leandro Helgueira
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supporting information
p. 2308 - 2316
(2021/04/07)
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- Insights into the electrochemical degradation of phenolic lignin model compounds in a protic ionic liquid-water system
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Cleavage of aryl ether (Caryl-O) bonds is crucial for the conversion and value-added utilization of lignin and its derivatives, but remains extremely challenging under mild conditions due to strong Caryl-O linkages. In this study, the Caryl-O bond breaking is achieved through electrocatalytic oxidation of four phenolic lignin model compounds with typical Caryl-O bonds,i.e., 4-ethoxyphenol (EP), 4-phenoxyphenol (PP),p-benzyloxyphenol (PBP), and 2-(2-phenylethoxy)phenol (2-PEP), in a protic ionic liquid [BSO3Hmim][OTf]-H2O electrolyte, and the electrocatalytic oxidation mechanism is also fully explored. The effects of H2O on the viscosity and conductivity of the [BSO3Hmim][OTf] ionic liquid system, as well as the solubility and diffusion coefficients of O2and the four lignin substrates, are investigated to optimize the optimal ratio of the electrolyte system composed of [BSO3Hmim][OTf] and H2O. Electrochemical oxidation-reduction behaviors of the four lignin substrates in the [BSO3Hmim][OTf]-H2O system and the effect of O2and N2atmospheres on degradation are studied in detail by using cyclic voltammetry (CV) curves. Finally, by combining the analysis of degradation products with isotope labeling experiments, the C-O bond cleavage mechanism is obtained, which mainly involves direct and indirect oxidation. Specifically, under a N2atmosphere, the substrates are oxidized directly on the RuO2-IrO2/Ti mesh electrode through Caryl-O bond splitting to form quinone and carbonium ions, while under an O2atmosphere, apart from the direct oxidation on the electrode, indirect oxidation of the lignin substrates also occurs throughin situgenerated H2O2. This study may provide some insight into developing effective strategies for efficient utilization of lignin under mild conditions.
- Liu, Guangyong,Wang, Qian,Yan, Dongxia,Zhang, Yaqin,Wang, Chenlu,Liang, Shijing,Jiang, Lilong,He, Hongyan
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p. 1665 - 1677
(2021/03/09)
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- Highly efficient titanosilicate catalyst Ti-MCM-68 prepared using a liquid-phase titanium source for the phenol oxidation
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A highly efficient Ti-MCM-68 catalyst for phenol oxidation with H2O2 was prepared by a mild liquid-phase treatment for the first time. The key preparation procedures to excellent catalytic activity and high para-selectivity were the use of aqueous solutions of the Ti source and calcination at 650 °C prior to catalytic use.
- Inagaki, Satoshi,Ishizuka, Ryo,Ikehara, Yuya,Odagawa, Shota,Asanuma, Kai,Morimoto, Shunsuke,Kubota, Yoshihiro
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p. 3681 - 3684
(2021/02/03)
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- A high-nuclearity CuI/CuIInanocluster catalyst for phenol degradation
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Herein, we report a 54-nuclei copper nanocluster, [Cu54S13O6(tBuS)20(tBuSO3)12] (Cu54), which is the largest atom-precise CuI/CuIImix-valent cluster reported. The Cu54nanoclusters supported by TiO2exhibit decent photocatalytic activity for phenol degradation under visible light. This work provides a platform to explore the catalytic behaviors of CuI/CuIInanosystems.
- Liu, Li-Juan,Zhang, Jiang-Wei,Asad, Muhammad,Wang, Zhao-Yang,Zang, Shuang-Quan,Mak, Thomas C. W.
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supporting information
p. 5586 - 5589
(2021/06/12)
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- TiO2/Polyethersulphone films for photocatalytic degradation of acetaminophen in aqueous solution
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In this study, TiO2-polyethersulfone films with different TiO2 loadings, prepared by the phase inversion method were tested as photocatalysts for degradation of acetaminophen in aqueous solution. The prepared films were characterized by XRD, SEM-EDX, AFM, and XPS. The successful incorporation of the titanium dioxide nanoparticles was confirmed by the XRD and SEM-EDX. SEM images revealed a much smoother surface for the pristine PES as compared to the TiO2-PES films, while EDX result confirmed the immobilization of titanium, as increasing amounts of titania were detected with increased loading of titanium dioxide. The SEM cross sectional images also show that the prepared films transformed into porous structures with tear-like pores and the porosity increased from 0.06%, for pristine PES, to 0.35% for the (14 wt%) TiO2-PES, and then dropped slightly to 0.32% in (17 wt%) TiO2-PES due to the onset of aggregation. The TiO2-PES photocatalyst film with 14 wt% content of TiO2 exhibited 51% degradation efficiency for a film surface area of 80 cm2, and a maximum efficiency of 80% at 320 cm2 film surface area. However, an increased TiO2 loading up to 17 wt% led to a decline in efficiency which is attributed to agglomeration and possible defective pore structure of the films. The reactivity of the acetaminophen molecule, modelled using the density functional theory (DFT), enabled identification of the acetamido group and the aromatic ring as the regions most prone to electrophilic and radical attack, respectively.
- Abdullah, Abdul H.,Adlan Mohd Hir, Zul,Chijioke-Okere, Maureen O.,Njoku, Paschal C.,Ogukwe, Cynthia E.,Oguzie, Emeka E.
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- Enhanced photocatalytic activity for 4-nitrophenol degradation using visible-light-driven In2S3/α-Fe2O3 composite
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In2S3/α-Fe2O3 composites were synthesized using the methods of hydrothermal treatment and reflux. Characterization such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and Photoluminescence (PL) was used to characterize the crystallinity and morphology of the composites, which proved the successful synthesis of the In2S3/α-Fe2O3 heterostructures. The 4-nitrophenol (PNP) degradation experiments by visible light were studied to evaluate the photocatalytic activity of the In2S3/α-Fe2O3 composites. The composites showed much higher photocatalytic degradation activities and TOC removal rate than both pure In2S3 and α-Fe2O3. The PNP degradation rate of composites was about 4.7 and 11.9 times that of pure In2S3 and α-Fe2O3, respectively. The degradation process was detected by high performance liquid chromatography and mass spectrometry, and the degradation pathway was explained. Based on the trapping experiments, e? and ?OH were the main active species and a Z-scheme photocatalytic mechanism of In2S3/α-Fe2O3 was proposed, which showed the double advantage of high redox ability and efficient electron-hole pairs separation.
- Fang, Lujuan,Huang, Xiangyang,Jiang, Ruanjing,Liu, Zijing,Munthali, Rodger Millar,Wu, Xiaogang,Zhang, Ying
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- High-efficiency catalytic wet air oxidation of high salinity phenolic wastewater under atmospheric pressure in molten salt hydrate media
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An improved catalytic wet air oxidation (CWAO) process for high salinity phenolic wastewater is reported for the first time by using molten salt hydrates (MSHs) as reaction media. One feature of such a process is that it allows the operation to be conducted at atmospheric pressure owing to the temperature-increasing effect of MSHs. Another feature is that the inorganic salts in phenolic wastewater can be separated readily, taking advantage of the common-ion salting-out effect between inorganic salts and MSHs. Continuous catalytic oxidation degradation of the simulated high salinity phenolic wastewater demonstrated that more than 92% of phenol can be removed with chemical oxygen demand (COD) as high as 85% after reacting in CaCl2·3H2O medium at 150 °C with air as an oxidant. Meanwhile, the desalination efficiency of NaCl in continuous operation could reach up to 100%. It was found that CeCl3was an excellent catalyst for CWAO of phenol. XPS and UV-vis spectral characterization as well as radical scavenger experiments proved that [˙OH/Ce4+] was responsible for the synergistic catalytic degradation mechanism of phenol. Current work not only paves the way for developing a high-efficiency CWAO technology for concentrated organic wastewaters with high salinity, but also helps to better understand MSHs as reaction media.
- Tan, Hongzi,Wang, Shuai,Wang, Jinghua,Song, Feng,Sun, Xiuyu,Zhao, Rongrong,Zhang, Yuan,Cui, Hongyou
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supporting information
p. 2167 - 2174
(2021/02/06)
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- A Cu-bis(imidazole) Substrate Intermediate Is the Catalytically Competent Center for Catechol Oxidase Activity of Copper Amyloid-β
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Interaction of copper ions with Aβ peptides alters the redox activity of the metal ion and can be associated with neurodegeneration. Many studies deal with the characterization of the copper binding mode responsible for the reactivity. Oxidation experiments of dopamine and related catechols by copper(II) complexes with the N-terminal amyloid-β peptides Aβ16 and Aβ9, and the Aβ16[H6A] and Aβ16[H13A] mutant forms, both in their free amine and N-acetylated forms show that efficient reactivity requires the oxygenation of a CuI-bis(imidazole) complex with a bound substrate. Therefore, the active intermediate for catechol oxidation differs from the proposed in-between state for the catalytic oxidation of ascorbate. During the catechol oxidation process, hydrogen peroxide and superoxide anion are formed but give only a minor contribution to the reaction.
- Bacchella, Chiara,Dell'acqua, Simone,Nicolis, Stefania,Monzani, Enrico,Casella, Luigi
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p. 606 - 613
(2021/02/05)
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- Enhanced nonradical catalytic oxidation by encapsulating cobalt into nitrogen doped graphene: highlight on interfacial interactions
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Supported metal catalysts are widely used for heterogeneous catalytic processes (e.g., Fenton-like reaction), but the mechanisms of interfacial processes are still ambiguous. Herein, unique nanocarbon based catalysts with Co nanoparticles encapsulated in
- Yu, Xiaoyong,Wang, Lijing,Wang, Xin,Liu, Hongzhi,Wang, Ziyuan,Huang, Yixuan,Shan, Guoqiang,Wang, Weichao,Zhu, Lingyan
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supporting information
p. 7198 - 7207
(2021/03/29)
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- Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
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In many metal catalyses, the traditional strategy of removing chloride ions is to add silver salts via anion exchange to obtain highly active catalysts. Herein, we reported an alternative strategy of removing chloride anions from ruthenium trichloride using an organic [P+-N-] zwitterionic compound via multiple hydrogen bond interactions. The resultant organic-metal hybrid catalytic system has successfully been applied to the aerobic oxidation of alcohols, tetrahydroquinolines, and indolines under mild conditions. The performance of zwitterion is far superior to that of many other common Lewis bases or Br?nsted bases. Mechanistic studies revealed that the zwitterion triggers the dissociation of chloride from ruthenium trichloride via nonclassical hydrogen bond interaction. Preliminary studies show that the zwitterion is applicable to catalytic transfer semi-hydrogenation.
- Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
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p. 3498 - 3506
(2021/04/07)
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- Conjugated-Polypyridine-Derivative-Derived Semiconductive Iodoplumbates with Tunable Architectures and Efficient Visible-Light-Induced Photocatalytic Property
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By mediation of the pH values, three novel inorganic-organic iodoplumbate hybrids, [Me3TPT][Pb3I9] [1; Me3TPT = trimethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine], [Me3TPT]2[Pb9I24] (2), and [Me3TPT]2[Pb19I44] (3), have been achieved under solvothermal conditions. The large conjugated in situ N-alkylation polypyridine derivatives act as structure-directing agents and electron acceptors, making the materials feature adjustable structural variations with 0D, 1D, and 2D structures and a potential semiconductive performance with narrow energy gaps (1.72, 1.80, and 1.78 eV for 1-3, respectively), which result in their efficient photocatalytic activity under visible-light irradiation. Theoretical calculation reveals that the conjugated organic moieties greatly contribute to the conduction band, leading to narrow band gaps. It is expected that the work will contribute to the exploitation of novel semiconducting halometallates by employing conjugated organic species as structure-directing agents.
- Li, Chen,Wang, Kui,Li, Xin-Yu,Jiang, Xiao-Fan,Wei, Qi,Li, Jin-Hua,Wang, Guo-Ming
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p. 2105 - 2111
(2021/03/23)
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- Heterogeneous Fenton-like oxidative degradation of sulfanilamide catalyzed by RuO2-rectorite composite
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RuO2-rectorite (RuO2-Rec) was prepared by intercalation, deposition and calcination. Its structure was characterized by XRD, XPS, SEM and EDS. It was used as a catalyst for the sulfanilamide (SA) degradation in the presence of H2O2. Unlike sodium-rectorite and RuO2 which couldn’t catalyze the degradation of SA, RuO2-Rec could effectively catalyze the decomposition of H2O2 into hydroxyl radicals to degrade SA. The degradation rate could reach ~ 100% under the optimal conditions of 58?μmol/L of SA, 1.16?mmol/L of H2O2, 0.133?g/L of RuO2-Rec, pH 3.5 and 25?°C in 5?h. The degradation process conformed to pseudo-first-order kinetic correlation. This degradation was affected by pH, the amount of RuO2-Rec and the concentrations of H2O2 and SA. However, under the optimal pH value of 3.5, a high degradation rate could be achieved with the increase in SA concentration from 58?μmol/L to 290?μmol/L as long as the optimal ratio of RuO2-Rec, H2O2 and SA kept unchanged. In addition, RuO2-Rec was stable and possessed low ruthenium leaching rate and excellent reusability. Therefore, RuO2-Rec is expected to be an active catalyst for the pollutant removal in the heterogeneous Fenton-like system.
- Pan, Feifei,Yang, Jianhong,Cai, Jun,Liu, Lianye
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p. 4595 - 4611
(2021/07/26)
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- RETRACTED ARTICLE: Selective photocatalytic conversion of guaiacol using g-C3N4 metal free nanosheets photocatalyst to add-value products
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Valorization of lignin into high valuable chemical is a critical challenge. Its availability is a key factor for the development of viable lignocellulosic processes to replace fossil derived compounds. In this work, new insights on the high photocatalytic conversion of guaiacol (82%) as a lignin model compound was achieved, also, high selectivity to p-benzoquinone (59%), catechol (27%), and pyrogallol (6%) was obtained using metal-free pyrolyzed g-C3N4 under visible light irradiation. To highlight the new insights, experimental parameters were modified to control the reaction mechanism to increase selectivity and photo-conversion. g-C3N4 photocatalyst was synthesized through urea calcination at 550 °C and the photocatalytic performance was assessed in terms of pyrolysis time, where higher time resulted in better photocatalytic activity. This effect was attributed to smaller structures and therefore better quantum confinement of the charges. The oxidation was promoted by [rad]OH radicals, which were detected through EPR operando mode and the addition of radical scavengers. A reaction pathway was proposed, in which the ·OH attacks guaiacol through a methoxy group. The photocatalytic reaction can be tuned using external oxidant agents such as O2 and/or H2O2 to promote certain radical formation, enhancing conversion rates and promoting selectivity for a specific product, where yield shifting from p-benzoquinone to pyrogallol was experimentally observed.
- Rojas,Espinoza-Villalobos,Salazar,Escalona,Contreras,Melin,Laguna-Bercero,Sánchez-Arenillas,Vergara,Caceres-Jensen,Rodriguez-Becerra,Barrientos
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- Structural and Biochemical Studies Enlighten the Unspecific Peroxygenase from Hypoxylon sp. EC38 as an Efficient Oxidative Biocatalyst
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Unspecific peroxygenases (UPOs) are glycosylated fungal enzymes that can selectively oxidize C-H bonds. UPOs employ hydrogen peroxide as the oxygen donor and reductant. With such an easy-to-handle cosubstrate and without the need for a reducing agent, UPOs are emerging as convenient oxidative biocatalysts. Here, an unspecific peroxygenase from Hypoxylon sp. EC38 (HspUPO) was identified in an activity-based screen of six putative peroxygenase enzymes that were heterologously expressed in Pichia pastoris. The enzyme was found to tolerate selected organic solvents such as acetonitrile and acetone. HspUPO is a versatile catalyst performing various reactions, such as the oxidation of prim- and sec-alcohols, epoxidations, and hydroxylations. Semipreparative biotransformations were demonstrated for the nonenantioselective oxidation of racemic 1-phenylethanol rac-1b (TON = 13 000), giving the product with 88% isolated yield, and the oxidation of indole 6a to give indigo 6b (TON = 2800) with 98% isolated yield. HspUPO features a compact and rigid three-dimensional conformation that wraps around the heme and defines a funnel-shaped tunnel that leads to the heme iron from the protein surface. The tunnel extends along a distance of about 12 ? with a fairly constant diameter in its innermost segment. Its surface comprises both hydrophobic and hydrophilic groups for dealing with substrates of variable polarities. The structural investigation of several protein-ligand complexes revealed that the active site of HspUPO is accessible to molecules of varying bulkiness with minimal or no conformational changes, explaining the relatively broad substrate scope of the enzyme. With its convenient expression system, robust operational properties, relatively small size, well-defined structural features, and diverse reaction scope, HspUPO is an exploitable candidate for peroxygenase-based biocatalysis.
- Ebner, Katharina,Glieder, Anton,Kroutil, Wolfgang,Mattevi, Andrea,Rinnofner, Claudia,Rotilio, Laura,Swoboda, Alexander
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p. 11511 - 11525
(2021/09/22)
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- Efficient hydroxylation of benzene to phenol by H2O2using Ni-doped CuWO4on carbon nitride as a catalyst under solar irradiation and its structure-activity correlation
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A series of environmentally benign and highly efficient Z-scheme Ni-doped CuWO4 nanoparticles on graphitic carbon nitride (g-C3N4) were synthesized. The Ni-CuWO4 nanoparticles were prepared via the substitution of Ni2+ on a wolframite CuWO4 crystal. The photocatalytic activity of these nanocomposites was investigated for the hydroxylation of benzene to phenol, considering the importance of phenol and carcinogenicity of benzene. An excellent benzene conversion of 98.5percent, with 82.7percent selectivity and 81.5percent yield of phenol, was achieved over 0.2percent Ni-CuWO4/g-C3N4 in 15 minutes under sunlight using H2O2 as an oxidant in water, which is higher than those of pristine g-C3N4 and Ni-CuWO4. The high yield of phenol is mainly attributed to the narrow band gap of the semiconductor and enhanced visible light absorption capacity over a specific range of wavelength by the introduction of g-C3N4, which minimized the rapid recombination of photogenerated holes and electrons. The computational study related to this work also implied the high optical property and stability of the photocatalyst. This journal is
- Basyach, Purashri,Borthakur, Sukanya,Chetia, Pubali,Guha, Ankur Kanti,Kalita, Lisamoni,Saikia, Lakshi,Sonowal, Karanika
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p. 12774 - 12789
(2020/07/23)
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- Dopamine polymer derived isolated single-atom site metals/N-doped porous carbon for benzene oxidation
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Isolated single-atom site metals/nitrogen-doped porous carbon (ISAS M/NPC, M = Fe, Co, Ni) catalysts are successfully prepared by a top-down polymerization-pyrolysis-etching-activation (PPEA) strategy, which uses dopamine as the precursor. Due to the isolated single atom Fe active sites and porous structure, the ISAS Fe/NPC catalyst displays a high benzene conversion up to 42.6percent and nearly 100percent phenol selectivity.
- Wu, Konglin,Zhan, Fei,Tu, Renyong,Cheong, Weng-Chon,Cheng, Yuansheng,Zheng, Lirong,Yan, Wensheng,Zhang, Qinghua,Chen, Zheng,Chen, Chen
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supporting information
p. 8916 - 8919
(2020/08/17)
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- Method for preparing p-benzoquinone compound by using dual-catalytic system
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The invention belongs to the technical field of organic synthesis, and relates to a p-benzoquinone compound preparation method, which comprises: 1) sequentially adding a phenol compound, a transitionmetal salt catalyst, an acidic ionic liquid and a solvent to a high pressure reaction kettle, introducing oxygen to achieve a specified pressure, heating to a specified temperature, continuously stirring, and carrying out a reaction for 0.5-5 h; and 2) after the reaction is finished, separating the catalyst from the reaction system, evaporating the solvent, washing the residual solid with a solvent, and carrying out steam stripping to obtain the p-benzoquinone compound. According to the method disclosed by the invention, high conversion rate and high selectivity are ensured, the dosage of thetransition metal catalyst is effectively reduced, the ionic liquid catalyst can be recycled multiple times, a low-emission and environment-friendly production process is realized, the economy is alsogreatly improved, and the method is suitable for industrial production.
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Paragraph 0020-0022; 0027
(2020/04/02)
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- Preparation method and application of high-safety hydroquinone composition
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The invention also provides a preparation method of a high-safety hydroquinone composition, comprising the following steps of: 1) adding aniline, MnO2 and sulfuric acid into a reaction device according to a molar ratio of aniline to MnO2 to sulfuric acid being 1: 1-5: 2-6, and stirring until the reaction is complete to obtain p-benzoquinone, wherein the feeding temperature is 0-15 DEG C and the reaction temperature is 0-30 DEG C; and 2) carrying out steam distillation on the prepared p-benzoquinone reaction liquid, adding iron powder into the collected distillation condensate according to a molar ratio of p-benzoquinone to iron powder being 1: 0.5-1.0, and stirring at 70-100 DEG C until the reaction is complete to prepare hydroquinone. The method has the advantages of simplicity and convenience in operation, high yield, high purity, low cost, suitability for industrial production and the like.
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Paragraph 0008; 0098-0100; 0103-0105; 0108-0110
(2020/12/10)
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- Differences in the Mechanisms of MnO2Oxidation between Lignin Model Compounds with the p-Hydroxyphenyl, Guaiacyl, and Syringyl Nuclei
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The purpose of this study was to examine how the rate and mechanism of MnO2 oxidation differ between the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) types of simple nonphenolic lignin model compounds as well as the p-ethylphenyl (E) type compounds. The oxidation was conducted using an excess amount of MnO2 in a sulfate buffer solution at a pH value of 1.5 at room temperature. MnO2 oxidized at least the G and S nuclei, although it commonly oxidizes alcohols present at the benzyl position. The oxidation rates of the benzyl alcohol derivatives were in the order of G- > S- ? H- > E-type, which suggests that the rates are determined by the electronic effects of their methoxy and ethyl functional groups on not only their benzyl positions but also their aromatic π-electron systems. The kinetic isotope effect was observed in the MnO2 oxidations of the same derivatives deuterated at their benzyl hydroxymethyl groups. The observed magnitudes were in the order of E- ? H- > G- ? S-type, suggesting that the contribution of oxidation of their aromatic nuclei, which is another reaction mode of the oxidation of their benzyl positions, increases in the reverse order.
- Sun, Shirong,Akiyama, Takuya,Yokoyama, Tomoya,Matsumoto, Yuji
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p. 6819 - 6825
(2020/07/02)
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- Oxidation of benzyl alcohol by novel peripherally and non-peripherally modular C2-symmetric diol substituted cobalt (II) phthalocyanines
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In this study, a modular ligand structure was designed by altering the binding position of the phenyl group at backbone of hydrobenzoin. A series of regio isomeric substituted phthalonitriles derived from this modular C2-symmetric ligand was sy
- G?k, Halil Zeki,G?k, Ya?ar,Y?lmaz, Mustafa Kemal
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- Different performances of Ni3(PO4)2 in TiO2 photocatalysis under aerobic and anaerobic conditions
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It has been reported that cobalt phosphate (CoP) deposited on TiO2 is beneficial to the photoelectrochemical (PEC) oxidation of water in a phosphate solution, but detrimental to the photocatalytic (PC) oxidation of phenol even in a phosphate solution. Herein, we report amorphous nickel phosphate (NiP) deposited on TiO2 being more active than TiO2 in a phosphate-free solution. This was observed not only from the PEC oxidation of water, but also from the PC oxidation of phenol under air, and from the PC reduction of water to H2 under N2 in the presence of methanol, respectively. During the PC reactions under air and N2, however, the suspension of NiP/TiO2 changed its colour from white to pale yellow and dark grey, respectively. Such colour changes were also observed from CoP/TiO2 under similar conditions. Through a spectral and thermodynamic analysis, it is proposed that under air, NiP is oxidized to a high valence Ni species, and then regenerated through water and phenol oxidation, while NiP under N2 is reduced to metallic Ni, followed by proton reduction.
- Chen, Chen,Wang, Yaru,Xu, Yiming,Zhao, Jianjun
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p. 1761 - 1768
(2020/04/09)
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- Light driven photodegradation of 4-nitrophenol with novel Co and Cu phthalocyanine in aqueous media
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In this work, we have used two different metal centered water soluble phthalocyanines for the degradation of 4-nitrophenol in water media. In the photodegradation reactions that took place in the photoreactor for 1 h without using any oxidant, 4-nitrophenol compound was completed with 95% (for CoPc) and 97% (for CuPc) conversion to toxic and non-harmful species. The hydroquinone compound was identified as the main product and the benzoquinone compound as the by-product. The turnover number for Cu phthalocyanine was 1896 and for Co phthalocyanine was 2101. Finally, recovery studies were carried out for water soluble Cu phthalocyanine used as photocatalyst and the number of cycles was determined as 7.
- Tekintas, Kader,Tugba Saka, Ece
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- Design, syntheses, spectroscopic, aggregation properties of novel peripheral octa-substituted zinc(II), magnesium(II) and lead(II) phthalocyanines and investigation of their photocatalytic properties on the photooxidation of 4-nitrophenol
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In the present paper, the syntheses, spectroscopic characterization, aggregation behaviours and photocatalytic properties of phthalocyanine compounds were searched. Octa-substituted phthalocyanines (ZnII (Pc-Zn), MgII (Pc-Mg) and PbII (Pc-Pb)) with eight peripheral (E)-3-(3-hydroxyphenyl)-1-(2,4,5-trimethoxyphenyl)prop-2-en-1-one groups were synthesized by cyclotetramerization. The spectral properties of these compounds were carried out that used widespread spectroscopic techniques. Later on, aggregation properties of synthesized phthalocyanines were examined in polar and apolar solvents. In addition to this, the photocatalytic activities of new synthesized metallophthalocyanines containing various central metal ions (zinc (II), magnesium (II) and lead (II)) were investigated. Three different metal centered phthalocyanines have been prepared for the photodegradation of 4-nitrophenol. In the photodegradation reactions that carried out in the photoreactor for 1 h without using any oxidant, 4-nitrophenol compound was completed with 90% (for PbII (Pc-Pb)), 56% (for ZnII (Pc-Zn)) and 12% (for MgII (Pc-Mg)) conversion from toxic species to non-harmful species and unknown intermediates. The turnover numbers were determined as 1500 for PbII (Pc-Pb), 933 for ZnII (Pc-Zn).
- Kahriman, Nuran,Kantekin, Halit,Serdaro?lu, Vildan,Tekintas, Kader,Tugba Saka, Ece,Yalazan, Halise
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- Synthesis, aggregation, photocatalytical and electrochemical properties of axially 1-benzylpiperidin-4-oxy units substituted silicon phthalocyanine
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Photosensitized catalysis is the initiation of degradation or transformation reactions of molecules using a combination of light and photoactive materials as catalysts. In this work, 1-benzylpiperidin-4-oxy substituted silicone phthalocyanine (SiPc) 3 has been synthesized and characterized with different spectral data and determined catalytic behavior in p-nitrophenol degradation with 1758 turnover number (TON) and 586 turnover frequency (TOF) values. Metallophthalocyanine 3 is soluble in different organic solvents and investigated aggregation behavior in common organic solvents. Electrochemical properties of metallophthalocyanine 3 was defined by using cyclic voltammetry (CV) technique. Silicone phthalocyanine (SiPc) 3 shows one irreversible reduction couple R1 at ?0.85 V (ΔEp = 288 mV), one reversible reduction couple R2 at ?1.54 V (ΔEp = 95 mV) and one quasi-reversible oxidation couple O1 at 1.07 V (ΔEp = 135 mV).
- Saka, Ece Tugba,Yalazan, Halise,B?y?kl?oglu, Zekeriya,Kantekin, Halit,Tekintas, Kader
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- Periodic mesoporous titania with anatase and bronze phases-the new generation photocatalyst: Synthesis, characterisation, and application in environmental remediation
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High-quality 2D-hexagonal ordered mesoporous titania with a well-crystallized framework structure and a high surface area was successfully synthesized, in a reproducible way, using Pluronic F127, Pluronic P123, Synperonic F108 and CTAB as structure-directing agents, and the resulting nanostructured matrix is designed as TMF-127, TMP-123, TMF-108 and TMC-016/TMC-036, respectively. The periodic array of the pore structure of these mesoporous materials is described by combining small-angle X-ray diffraction, high-resolution transmission electron microscopy and nitrogen sorption techniques. All these materials show significant amounts of intrinsic defects, viz., electrons trapped in oxygen vacancy and/or Ti3+ centres, by tuning the pore structure. These defects in-turn promote the charge separation of photogenerated excitons, and therefore exhibit excellent photocatalytic activity for the degradation of famotidine (TMP-123: DE100 = 75 min; P-25: DE100 = 120 min), and 4-chlorophenol (TMP-123: DE95 = 180 min; P-25: DE60 = 180 min). The superior activity of the mesoporous titania over the fumed titania (P-25) is ascribed to: (i) light absorption extending into the visible region, (ii) low charge-transfer resistance and high carrier density, and (iii) intrinsic Ti3+ defects, as deduced from DRUV-Visible, photo-electrochemical (Nyquist and Mott-Schottky) and EPR studies, respectively.
- Vatti, Surya Kumar,Gupta, Sanjeev,Raj, Rayappan Pavul,Selvam, Parasuraman
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p. 16269 - 16284
(2020/10/14)
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- Cuo and ceo2 assisted fe2o3/attapulgite catalyst for heterogeneous fenton-like oxidation of methylene blue
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In this paper, CuO and CeO2 were screened as co-catalyst components for Fe2O3/attapulgite (ATP) catalyst, and three new catalysts (CuO-Fe2O3/ATP, CeO2-Fe2O3/ATP and Cu
- Dong, Lingyu,Du, Jianhua,Qian, Chunyuan,Wang, Yi,Zhang, Ting
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p. 23431 - 23439
(2020/07/03)
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- Can Donor Ligands Make Pd(OAc)2a Stronger Oxidant? Access to Elusive Palladium(II) Reduction Potentials and Effects of Ancillary Ligands via Palladium(II)/Hydroquinone Redox Equilibria
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Palladium(II)-catalyzed oxidation reactions represent an important class of methods for selective modification and functionalization of organic molecules. This field has benefitted greatly from the discovery of ancillary ligands that expand the scope, reactivity, and selectivity in these reactions; however, ancillary ligands also commonly poison these reactions. The different influences of ligands in these reactions remain poorly understood. For example, over the 60-year history of this field, the PdII/0 redox potentials for catalytically relevant Pd complexes have never been determined. Here, we report the unexpected discovery of (L)PdII(OAc)2-mediated oxidation of hydroquinones, the microscopic reverse of quinone-mediated oxidation of Pd0 commonly employed in PdII-catalyzed oxidation reactions. Analysis of redox equilibria arising from the reaction of (L)Pd(OAc)2 and hydroquinones (L = bathocuproine, 4,5-diazafluoren-9-one), generating reduced (L)Pd species and benzoquinones, provides the basis for determination of (L)PdII(OAc)2 reduction potentials. Experimental results are complemented by density functional theory calculations to show how a series of nitrogen-based ligands modulate the (L)PdII(OAc)2 reduction potential, thereby tuning the ability of PdII to serve as an effective oxidant of organic molecules in catalytic reactions.
- Bruns, David L.,Musaev, Djamaladdin G.,Stahl, Shannon S.
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supporting information
p. 19678 - 19688
(2020/12/18)
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- Carbon nanotubes as catalysts for wet peroxide oxidation: The effect of surface chemistry
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Three magnetic carbon nanotube (CNT) samples, named A30 (N-doped), E30 (undoped) and E10A20 (selectively N-doped), synthesized by catalytic chemical vapor deposition, were modified by introducing oxygenated surface groups (oxidation with HNO3, samples CNT-N), and by heat treatment at 800 °C for the removal of surface functionalities (samples CNT-HT). Both treatments lead to higher specific surface areas. The acid treatment results in more acidic surfaces, with higher amounts of oxygenated species being introduced on N-doped surfaces. Heat-treated samples are less hydrophilic than those treated with nitric acid, heat treatment leading to neutral or basic surfaces, only N-quaternary and N-pyridinic species being found by XPS on N-doped surfaces. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4-nitrophenol solutions (4-NP, 5 g L?1) at atmospheric pressure, T = 50 °C and pH = 3, using a catalyst load of 2.5 g L?1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP. The high temperature treatment enhanced significantly the activity of the CNTs towards CWPO, evaluated in terms of 4-NP and total organic carbon conversion, due to the increased hydrophobicity of their surface. In particular, E30HT and E10A20HT were able to remove ca. 100% of 4-NP after 8 h of operation. On the other hand, by treating the CNTs with HNO3, the activity of the less hydrophilic samples decreased upon increasing the concentration of surface oxygen-containing functionalities, whilst the reactivity generated inside the opened nanotubes improved the activity of the highly hydrophilic A30 N.
- Martin-Martinez, Maria,Machado, Bruno F.,Serp, Philippe,Morales-Torres, Sergio,Silva, Adrián M.T.,Figueiredo, José L.,Faria, Joaquim L.,Gomes, Helder T.
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p. 332 - 340
(2019/03/17)
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- An efficient and recyclable copper nano-catalyst for the selective oxidation of benzene to p-benzoquinone (p-BQ) using H2O2(aq) in CH3CN
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The molecular copper complex tetrakis(acetonitrile)copper(I) perchlorate [Cu(CH3CN)4ClO4] (1) was shown to act as a catalyst precursor for the efficient oxidation of benzene to p-benzoquinone (p-BQ) with a percentage selectivity of 60–80% under mild conditions, and produces phenol (PhOH) as a minor product at room temperature. Here, we obtained evidences showing the formation of copper based nanoparticle catalyst (NC) (2) from 1 to be the vital step responsible for its ability to catalyze the conversion of benzene to p-BQ, presumably via double oxidation. Addition of a considerable amount of H2O to the reaction mixture improved the selectivity for forming p-BQ to 84% and/or the conversion efficiency to 98%. In addition, the copper NC easily formed in situ through the oxidation of substrate using H2O2 in CH3CN. After separating the NC from the reaction mixture and recycling them several times, it still maintained comparable catalytic efficiency and selectivity for the conversion of benzene to p-BQ.
- Wanna, Wondemagegn Hailemichael,Ramu, Ravirala,Janmanchi, Damodar,Tsai, Yi-Fang,Thiyagarajan, Natarajan,Yu, Steve S.-F.
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p. 332 - 346
(2019/01/24)
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- Hexacoppergermsesquioxanes as complexes with N-ligands: Synthesis, structure and catalytic properties
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A simple and versatile strategy of synthesis of cage metallagermaniumsesquioxanes is demonstrated for isolation of Cu6-based phenylgermsesquioxanes 1–6. Structure of newly synthesized coppergermsesquioxanes was established by single-crystal X-ray diffraction analysis. General principle of these cages’ topology implies the presence of two linear Cu3 fragments, coordinated by three pairs of ligands. These are: (i) cyclic germsesquioxanes [PhGeO1,5]5, products 1–6, (ii) 1,10-phenanthrolines, (1, 3–5) or 2,2’-bipyridines, (2, 6), (or and (iii) OX species (X = H, 1–2, CH3, 3, H and C2H5O, 4, HCO, 5, CH3CO, 6). Appearance of non-expected species (formiate for 5, acetate for 6), resulted from corresponding alcohols used as reaction media, points at easyness of oxidation processes in the conditions of such self-assembling reactions. Catalytic tests showed high activity of complexes 1 and 2 as precatalysts in homogeneous oxidations of alkanes (cyclohexane, methylcyclohexane, n-heptane, cis-1,2-dimethylcyclohexane with hydrogen peroxide in acetonitrile solution. Hydroxyl radicals take part in the reaction. The same complexes catalyze oxidation of alcohols (cyclohexanol, 2-heptanol, 1-phenylethanol) to corresponding ketones with tert-butyl hydroperoxide in almost 100% yield. With the addition of various alkyl ammonium salts, complex 2 could also furnish corresponding amides in high yield.
- Kulakova, Alena N.,Korlyukov, Alexander A.,Zubavichus, Yan V.,Khrustalev, Victor N.,Bantreil, Xavier,Shul'pina, Lidia S.,Levitsky, Mikhail M.,Ikonnikov, Nikolay S.,Shubina, Elena S.,Lamaty, Frédéric,Bilyachenko, Alexey N.,Shul'pin, Georgiy B.
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- METHODS FOR OXIDATION FROM BENZENE TO P-BENZOQUINONE, METHODS FOR PROCDUCTION OF 1,4-HYDROQUINONE FROM BENZENE, AND CATALYST PRECURSORS FOR THE METHODS THEREOF
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The bare copper salts including tetrakis(acetonitrile)copper(I) perchlorate [Cu(CH3CN)4ClO4] or copper metal were shown to be the catalyst precursors for the efficient oxidation of benzene to p-benzoquinone (60-80%) under mild conditions. This system also yields minor product of phenol. The present application obtained evidences to show that the formation of copper nano-catalyst is the vital component and responsible for the production of benzoquinone via double oxidation in a concerted like manner. The nano-catalyst can easily form in situ through the oxidation of substrate in a H2O2/H2O/CH3CN system and be separated from the reaction mixture as well as recycled for several times with comparable catalytic efficiency from benzene top-benzoquinone and phenol.
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Sheet 11; 26; 27
(2019/06/27)
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