- Nickle-Schiff base covalently grafted to UiO-66-NH2 as heterogeneous catalyst for ethylene oligomerization
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Metal organic frameworks (MOFs) UiO-66-NH2 had been modified by reaction of pyridine-2-carboxaldehyde with the amino groups to form a pyridineimine that act as ligand of metal Ni. The UiO-66-NH2 grafted pyridineimine nickel catalyst of post synthetic modification was assessed by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), inductively coupled plasma mass spectrometry (ICP-MS) and nitrogen adsorption–desorption, and the catalytic performance of the UiO-66-NH2 grafted pyridineimine nickel catalyst in ethylene oligomerization was investigated. The results showed that the catalyst structure, reaction temperature, Al/Ni molar ratio and reaction pressure had a significant effect on the catalytic activity and products selectivity. The catalytic activity of 3.76 × 105 g·(mol Ni·h)?1 and 75.94% selectivity of butene were obtained when the reaction temperature was 25 ℃, Al/Ni molar ratio was 1000 and reaction pressure was 1.2 MPa.
- Chen, Liduo,Jin, Rui,Li, Cuiqin,Mao, Guoliang,Tan, Jinyan,Wang, Jun,Zhang, Na
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- Tuning crystal phase of molybdenum carbide catalyst to induce the different selective hydrogenation performance
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α-MoC, β-Mo2C, and MoC-Mo2C were synthesized and investigated in the selective hydrogenation of 1,3-butadiene to understand the effect of crystal phases. The catalysts were characterized by XRD, N2-physisorption, SEM, TEM, XPS and chemisorptions. The adsorption properties and electronic properties over MoC(001) and Mo2C(001) were investigated by DFT calculations. The catalysts were evaluated at low and high temperatures in a fixed-bed reactor. β-Mo2C exhibits high activity and low butenes selectivity, due to the high concentration of hydrogen at each active site as well as the stronger adsorption and higher capacity of alkene; MoC-Mo2C shows better stability due to synergetic effect. At high temperature, the reaction rate is more dependent on the PH2 than PC4H6. Increasing PH2 could promote the activity and reduce oligomers formation. β-Mo2C exhibits the best performance at high temperatures concerning its high activity and the inhibition of oligomerization. This work is valuable for the non-precious metal catalyst development.
- Ding, Ziluo,Hou, Ruijun,Sun, Kening,Xu, Yamei,Yang, Qiuchen
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- Ethylene oligomerization with 2-hydroxymethyl-5,6,7-trihydroquinolinyl-8-ylideneamine-Ni(II) chlorides
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A series of Ni complexes of the general formula [2-(MeOH)-8-{N(Ar)}C9H8N]NiCl2, where Ar = 2,6-Me2C6H3 in Ni1; 2,6-Et2C6H3 in Ni2; 2,6-i-Pr2C6H3 in Ni3; 2,4,6-Me3C6H2 in Ni4; 2,6-Et2-4-MeC6H2 in Ni5 and 2,4,6-t-Bu3C6H2 in Ni6 has been synthesized and characterized by elemental analysis and IR spectroscopy. On activation with MMAO or Et2AlCl, these complexes showed high activity in ethylene oligomerization, reaching 2.23 × 106 g·mol–1 (Ni) h–1 at 30 °C with the Al/Ni ratio of 5500 and 9.11 × 105 g·mol–1 (Ni) h–1 with the Al/Ni of 800, respectively. Moreover, the content of α-C4 indicated high selectivity exceeding 99% in the Ni/Et2AlCl system. Comparing with the previous report by our group, this work discloses higher activity, presumably due to the substituent at the 2-position within the ligand influencing the steric hindrance around the metal atom. Furthermore, it is worth noting that the branched alkenes have been observed (iso-C6: 35.3 – 57.2%) in the oligomerization products.
- Xu, Lei,Li, Jiaxin,Lin, Wenhua,Ma, Yanping,Hu, Xinquan,Flisak, Zygmunt,Sun, Wen-Hua
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- Vapor-phase dehydration of 1,4-butanediol to 1,3-butadiene over Y2Zr2O7 catalyst
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Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over Y2O3-ZrO2 catalysts. In the dehydration, 1,3-butadiene (BD) together with 3-buten-1-ol (3B1OL), tetrahydrofuran, and propylene was produced depending on the reaction conditions. In the dehydration over Y2O3-ZrO2 catalysts with different Y contents at 325°C, Y2Zr2O7 with an equimolar ratio of Y/Zr showed high selectivity to 3B1OL, an intermediate to BD. In the dehydration at 360°C, a BD yield higher than 90% was achieved over the Y2Zr2O7 calcined at 700°C throughout 10 h. In the dehydration of 3B1OL over Y2Zr2O7, however, the catalytic activity affected by the calcination temperature is roughly proportional to the specific surface area of the sample. The highest activity of Y2Zr2O7 calcined at 700 °C for the BD formation from 1,4-BDO is explained by the trade-off relation in the activities for the first-step dehydration of 1,4-BDO to 3B1OL and for the second-step dehydration of 3B1OL to BD. The higher reactivity of 3B1OL than saturated alcohols such as 1-butanol and 2-butanol suggests that the C=C double bond of 3B1OL induces an attractive interaction to anchor the catalyst surface and promotes the dehydration. A probable mechanism for the one-step dehydration of 1,4-BDO to BD was discussed.
- Matsuda, Asami,Matsumura, Yoshitaka,Sato, Satoshi,Yamada, Yasuhiro
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- Regioselective Gas-Phase n-Butane Transfer Dehydrogenation via Silica-Supported Pincer-Iridium Complexes
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The production of olefins via on-purpose dehydrogenation of alkanes allows for a more efficient, selective and lower cost alternative to processes such as steam cracking. Silica-supported pincer-iridium complexes of the form [(≡SiO?R4POCOP)Ir(CO)] (R4POCOP=κ3-C6H3-2,6-(OPR2)2) are effective for acceptorless alkane dehydrogenation, and have been shown stable up to 300 °C. However, while solution-phase analogues of such species have demonstrated high regioselectivity for terminal olefin production under transfer dehydrogenation conditions at or below 240 °C, in open systems at 300 °C, regioselectivity under acceptorless dehydrogenation conditions is consistently low. In this work, complexes [(≡SiO?tBu4POCOP)Ir(CO)] (1) and [(≡SiO?iPr4PCP)Ir(CO)] (2) were synthesized via immobilization of molecular precursors. These complexes were used for gas-phase butane transfer dehydrogenation using increasingly sterically demanding olefins, resulting in observed selectivities of up to 77 %. The results indicate that the active site is conserved upon immobilization.
- Sheludko, Boris,Castro, Cristina F.,Khalap, Chaitanya A.,Emge, Thomas J.,Goldman, Alan S.,Celik, Fuat E.
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p. 407 - 415
(2020/12/01)
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- CATALYTIC HYDROCARBON DEHYDROGENATION
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A catalyst for dehydrogenation of hydrocarbons includes a support including zirconium oxide and Linde type L zeolite (L-zeolite). A concentration of the zirconium oxide in the catalyst is in a range of from 0.1 weight percent (wt. %) to 20 wt. %. The catalyst includes from 5 wt. % to 15 wt. % of an alkali metal or alkaline earth metal. The catalyst includes from 0.1 wt. % to 10 wt. % of tin. The catalyst includes from 0.1 wt. % to 8 wt. % of a platinum group metal. The alkali metal or alkaline earth metal, tin, and platinum group metal are disposed on the support.
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Paragraph 0063; 0064; 0124; 0125
(2021/03/13)
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- Tandem catalysts for the selective hydrogenation of butadiene with hydrogen generated from the decomposition of formic acid
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We report for the first time the selective hydrogenation of 1,3-butadiene to butene using formic acid as the hydrogen source with 1 wt% Pd/carbon in a continuous flow reactor. The catalytic results show that the selectivity is even higher when formic acid is used compared to gas hydrogen.
- Carrales-Alvarado, D. H.,Dongil, A. B.,Guerrero-Ruiz, A.,Rodríguez-Ramos, I.
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supporting information
p. 6479 - 6482
(2021/07/07)
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- A selective and stable Fe/TiO2catalyst for selective hydrogenation of butadiene in alkene-rich stream
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The replacement of precious metals by more abundant and therefore much less expensive metals remains a very important challenge in catalysis. A Fe/TiO2catalyst prepared by deposition-precipitation with urea showed very high selectivity to alkenes (>99%), even at high conversion (>90%), in selective hydrogenation of butadiene in an excess of propene. Its activity is very stable at 175 °C whereas the catalyst deactivates at 50 °C, although it is also initially very active. The presence of metallic iron seems to be necessary to ensure these excellent performances.
- Casale, Sandra,Delannoy, Laurent,Louis, Catherine,Méthivier, Christophe,Santander de Soto, Laura,Wang, Zhao
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supporting information
p. 7031 - 7034
(2021/07/21)
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- Selective dehydration of 1-butanol to butenes over silica supported heteropolyacid catalysts: Mechanistic aspect
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Butenes are considered as important olefinic building block to produce fuels/fuel additives and commodity chemicals. In the present investigation, selective dehydration of 1-butanol to butenes was studied in a continuous-flow fixed-bed reactor using various silica-supported heteropolyacid (HPA) catalysts such as phosphotungstic acid (PTA), silicotungstic acid (STA), phosphomolybdic acid (PMA), and silicomolybdic acid (SMA) as the solid acid catalysts. The physicochemical properties of these HPA were determined by BET, powder XRD, FTIR, NH3-TPD, and Py-FTIR. The acid strength and Br?nsted/Lewis (B/L) acid ratio were increased with higher loading of HPA on silica. The nature of HPA (addenda and hetero atom) and loading of HPA are important factors for the dehydration of 1-butanol and selectivity towards butenes. PTA and STA showed superior catalytic activity than PMA and SMA. The reaction temperature and WHSV also strongly affected the butanol conversion and selectivity of butenes. The selectivity of di-n?butyl ether decreases with the rising temperature from 523 K to 623 K. The isomerization of 1-butene leading to the formation of other butene isomers depends on the HPA loading, temperature, and WHSV. The presence of molybdenum addendum atom in PMA and SMA promotes dehydrogenation and hydrogenation, leading to the formation of various light hydrocarbons. The 20PTA/SiO2 catalyst afforded 99.8% selectivity towards butenes at quantitative conversion of 1-butanol, whereas the 20STA/SiO2 catalyst gave nearly 97.0% conversion of 1-butanol and 99.9% butenes selectivity at 673 K, 37.4 h?1 of WHSV.
- Dutta, Saikat,Kella, Tatinaidu,Mal, Sib Sankar,Shee, Debaprasad,Vennathan, Anjana Anandan
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- Pt/TS-1 catalysts: Effect of the platinum loading method on the dehydrogenation of n-butane
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A series of catalysts in which platinum was supported on the crystalline pure titanium silicalite (TS-1) were prepared using two different loading methods, namely, an ethylene glycol (EG) reduction method and the conventional incipient wetness impregnation (IM) technique. Various characterization techniques were used to study the effect of the loading method on the physicochemical and morphological properties of the prepared catalysts. Also the effect of the platinum-loading method on the dehydrogenation of n-butane was investigated in a fixed-bed reactor. The results show that the EG method favors the formation of a more-concentrated Pt dispersion, which results in much better catalytic activities for the selective formation of butenes and butadiene (> 97 %). This phenomenon is interpreted by carrying out density functional theory (DFT) calculations with focus on the relationship between the coverage of n-butane on Pt surface and the activation barrier for the first C[sbnd]H bond cleavage.
- Shao, Mingyuan,Hu, Chaoquan,Xu, Xuebing,Song, Yang,Zhu, Qingshan
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- Synthesis of a ni complex chelated by a [2.2]paracyclophane-functionalized diimine ligand and its catalytic activity for olefin oligomerization
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A diimine ligand having two [2.2]paracyclophanyl substituents at the N atoms (L1) was prepared from the reaction of amino[2.2]paracyclophane with acenaphtenequinone. The ligand re-acts with NiBr2(dme) (dme: 1,2-dimethoxyethane) to form the dibromonickel complex with (R,R) and (S,S) configuration, NiBr2(L1). The structure of the complex was confirmed by X-ray crystallog-raphy. NiBr2(L1) catalyzes oligomerization of ethylene in the presence of methylaluminoxane (MAO) co-catalyst at 10–50 °C to form a mixture of 1-and 2-butenes after 3 h. The reactions for 6 h and 8 h at 25 °C causes further increase of 2-butene formed via isomerization of 1-butene and formation of hexenes. Reaction of 1-hexene catalyzed by NiBr2(L1)–MAO produces 2-hexene via isom-erization and C12 and C18 hydrocarbons via oligomerization. Consumption of 1-hexene of the reaction obeys first-order kinetics. The kinetic parameters were obtained to be ΔG≠ = 93.6 kJ mol?1, ΔH≠ = 63.0 kJ mol?1, and ΔS≠ = ?112 J mol?1deg?1. NiBr2(L1) catalyzes co-dimerization of ethylene and 1-hexene to form C8 hydrocarbons with higher rate and selectivity than the tetramerization of eth-ylene.
- Osakada, Kohtaro,Takeuchi, Daisuke,Tojo, Yoshi-Aki
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- RED SLUDGE USED AS A CATALYST FOR OLEFIN ISOMERIZATION
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The invention relates to systems and a method for isomerizing a charge to form a stream of alpha-olefin product. An example of a process includes calcination of red mud, flow of an olefin feedstock onto red sludge in an isomerization reactor, and separation of alpha-olefin from reactor effluent.
- -
-
Paragraph 0006; 0010; 0012; 0028
(2021/12/31)
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- Understanding the Deactivation of Ag?ZrO2/SiO2 Catalysts for the Single-step Conversion of Ethanol to Butenes
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Ag?ZrO2/SBA-16 has recently been found to be efficient for catalyzing the single-step conversion of ethanol to butene (1- and 2-butene mixtures) in the presence of H2. The reaction proceeds via a cascading sequence of reactions over mixed metal and Lewis sites, with the catalyst composition tuned to selectively favor butene formation. However, the catalyst slowly deactivates when evaluated over long reaction times. In this work, we evaluated the lifetime of the Ag?ZrO2/SBA-16 catalyst system for ethanol-to-butene conversion at 325 °C for up to 800 hours on stream. Several characterization techniques were used to elucidate the mechanism(s) by which catalyst deactivation occurs. Coke deposition, Ag particle sintering, and Ag0-to-Ag+ oxidation state change were identified to be the major causes of catalyst deactivation. Coke deposits cover primarily Lewis acid sites which are responsible for aldol condensation, Meerwein-Ponndorf-Verley (MPV) reduction, and dehydration reactions. Ag particle sintering and Ag oxidation state change leads to a reduction in the number of metallic Ag sites responsible for the dehydrogenation/hydrogenation steps. The fresh catalyst likely experiences hydrothermal sintering in the early stage of reaction and permanently loses some active Lewis acid sites before reaching a new structural steady state. The deactivation of Lewis acid sites leads to a decrease in overall ethanol conversion, whereas the deactivation of the metallic Ag sites decreases the butene selectivity. For catalyst regeneration, oxidative calcination (at 500 °C) followed by reduction (at 325 °C) successfully removes all the coke species on the catalyst surface and restores the metallic Ag particles of the 4Ag?4ZrO2/SBA-16 catalysts.
- Lin, Fan,Dagle, Vanessa Lebarbier,Winkelman, Austin D.,Engelhard, Mark,Kovarik, Libor,Wang, Yilin,Wang, Yong,Dagle, Robert,Wang, Huamin
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p. 999 - 1008
(2020/12/18)
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- Degradation of Organic Cations under Alkaline Conditions
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Understanding the degradation mechanisms of organic cations under basic conditions is extremely important for the development of durable alkaline energy conversion devices. Cations are key functional groups in alkaline anion exchange membranes (AAEMs), and AAEMs are critical components to conduct hydroxide anions in alkaline fuel cells. Previously, we have established a standard protocol to evaluate cation alkaline stability within KOH/CD3OH solution at 80 °C. Herein, we are using the protocol to compare 26 model compounds, including benzylammonium, tetraalkylammonium, spirocyclicammonium, imidazolium, benzimidazolium, triazolium, pyridinium, guanidinium, and phosphonium cations. The goal is not only to evaluate their degradation rate, but also to identify their degradation pathways and lead to the advancement of cations with improved alkaline stabilities.
- You, Wei,Hugar, Kristina M.,Selhorst, Ryan C.,Treichel, Megan,Peltier, Cheyenne R.,Noonan, Kevin J. T.,Coates, Geoffrey W.
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supporting information
p. 254 - 263
(2020/12/23)
-
- Bridging the Gap: From Homogeneous to Heterogeneous Parahydrogen-induced Hyperpolarization and Beyond
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Demonstration of parahydrogen-induced polarization effects in hydrogenations catalyzed by heterogeneous catalysts instead of metal complexes in a homogeneous solution has opened an entirely new dimension for parahydrogen-based research, demonstrating its applicability not only for the production of catalyst-free hyperpolarized liquids and gases and long-lived non-equilibrium spin states for potential biomedical applications, but also for addressing challenges of modern fundamental and industrial catalysis including advanced mechanistic studies of catalytic reactions and operando NMR and MRI of reactors. This essay summarizes the progress achieved in this field by highlighting the research contributed to it by our colleague and friend Kirill V. Kovtunov whose scientific career ended unexpectedly and tragically at the age of 37. His role in this research was certainly crucial, further enhanced by a vast network of his contacts and collaborations at the national and international level.
- Chekmenev, Eduard Y.,Goodson, Boyd M.,Bukhtiyarov, Valerii I.,Koptyug, Igor V.
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p. 710 - 715
(2021/04/14)
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- Tuning supported Ni catalysts by varying zeolite Beta heteroatom composition: effects on ethylene adsorption and dimerization catalysis
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The influence of zeolite heteroatom composition on the electron density and catalytic activity of a supported Ni cation is examined. Ni-[X]-Beta catalysts, where X = Al, Ga, Fe, or dealuminated, were synthesized and characterized with probe molecule adsorption with FTIR spectroscopy and C2H4dimerization catalysis. It was observedviaCO adsorption that supported Ni cations were increasing in electron density in the order: [Fe] > [Ga] > [Al]. C2H4dimerization activity increased with increasing electron density of the Ni cation. Despite similarities in reported acid site strength, the acid sites on [Fe]-Beta in this work had significantly lower activity than those on [Ga]-Beta for the skeletal isomerization of linear butenes as well as C2H4dimerization. Introducing H2as a reactant resulted in a decrease in dimerization activity for Ni-[Al]-Beta and Ni-[Ga]-Beta but an increase for Ni-[Fe]-Beta. The selectivity and activity of Ni-[DeAl]-Beta changed dramatically with the introduction of H2, which subsequently converted all C2H4withca.100% selectivity towards C2H6(even with a lower space velocity relative to without H2). These results demonstrate the ability of heteroatom composition to tune catalysis by using C2H4dimerization catalysis as a test reaction with zeolite Beta supported Ni catalysts.
- Meloni, Michael,Runnebaum, Ron C.
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p. 3393 - 3401
(2021/06/06)
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- METHOD TO PRODUCE C4 OLEFINS FROM NATURAL GAS-DERIVED ACETYLENE
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In accordance with the purpose(s) of the present disclosure, as embodied and broadly described herein, the disclosure relates to a method for producing C4 olefins from acetylene using supported metal-based catalysts and metal-based promoters. The method is inexpensive, efficient, and environmentally sound. Additionally, the method is selective for C4 olefins and other value-added products based on changes to reaction parameters including temperature, feed gas composition, and promoter identity. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.
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-
Paragraph 0015; 0016; 0019; 0020; 0246
(2021/10/22)
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- Method for eliminating hydrogen chloride by catalytic cracking of chloralkane
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The invention discloses a method for eliminating hydrogen chloride by catalytic cracking of chloralkane, comprising the following steps of: carrying out a cracking reaction on chloralkane under the action of a biomass-based nitrogen-doped carbon catalyst to eliminate hydrogen chloride so as to prepare corresponding olefin, wherein the biomass-based nitrogen-doped carbon catalyst is prepared by carbonizing biomass or a mixture of biomass and a nitrogen source at 400-1000 DEG C, and the biomass is selected from at least one of bamboo processing leftovers, wood processing leftovers, plant straws,plant leaves, cereals, beans, cereal processing leftovers, bean processing leftovers and livestock manure. The method disclosed by the invention has the advantages of simple preparation process, easily available raw materials, low cost, strong process controllability, easiness in large-scale production, high catalytic cracking conversion rate of the chloralkane, high product selectivity, low energy consumption and the like.
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-
Paragraph 0136-0141
(2020/08/06)
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- Silver(I) and Nickel(II) Complexes with Oxygen- or Nitrogen-Functionalized NHC Ditopic Ligands and Catalytic Ethylene Oligomerization
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Potentially bidentate ditopic ligands containing a N-heterocyclic carbene (NHC) donor associated with an ether or an amine have been prepared and coordinated to NiII centers. The influence of the length of the alkyl chain, –(CH2)2– or –(CH2)3– connecting the ether or the amine group to the heterocycle was examined. In the analogous AgI complexes [Ag{Im(Dipp)(C3OMe)-κ1CNHC}2]Cl (8), 9 and 10, in the neutral NiII complexes with a C3 spacer trans-[NiCl2{Im(Dipp)(C3OMe)-κ1CNHC}2] (5a), 6, and 7, and in the cationic cis-[Ni{Im(Dipp)(C3OMe)-κ1CNHC}2(NCMe)2](PF6)2 (15) and cis-[Ni{Im(Mes)(C3OMe)-κ1CNHC}2(NCMe)2](PF6)2 (16), the ligand is monodentate. [(ImH)(Dipp)(C3OMe)][NiX3{Im(Dipp)(C3OMe)-κ1CNHC}] (14a, X = Cl) and (14b, X = Br) are rare examples of complexes of the type [NiX3(NHC)]–. For comparison, [NiBr2{(Im)(Dipp)(C2NMe2)-κ2,CNHC,Namine}] (24) and [NiBr2{(Im)(Dipp)(C3NMe2)-κ2,CNHC,Namine}] (25) contain a six- or a seven-membered κ2CNHC,Namine chelate, respectively. Various NiII complexes were evaluated as precatalysts for ethylene oligomerization. The structures of the carbene (Dipp)(C3OMe)imidazole-ylidene (4) and of the complexes 5a, 7, 8, [(ImH)(Dipp)(C3OMe)]2[NiCl4] (11a), [(ImH)(Dipp)(C3OMe)]2[NiBr4] (11b), [(ImH)(Me)(C3OMe)]2[NiCl4] (13), 14b, 16·NCMe, [Im(H){C(Me)(=NDipp)}(C3OMe)]2 [NiCl4] (18), [AgCl{Im[C(Me)=NDipp](C3OMe)}-κ1CNHC] (19), [AgCl{Im(Dipp)(C3NMe2)-κ1CNHC}] (23), 24, 25 and trans-[NiCl2{Im(Dipp){CH2CH2C(O)OEt}}2] were analyzed by X-ray diffraction.
- Ren, Xiaoyu,Wesolek, Marcel,Bailly, Corinne,Karmazin, Lydia,Braunstein, Pierre
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p. 1073 - 1087
(2020/01/02)
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- 2-(: N, N -Diethylaminomethyl)-6,7-trihydroquinolinyl-8-ylideneamine-Ni(ii) chlorides: Application in ethylene dimerization and trimerization
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A series of Ni(ii) complexes with the general formula [2-((NEt2)Me)-8-{N(Ar)}C9H8N]NiCl2, where Ar = 2,6-Me2C6H3 in Ni1, 2,6-Et2C6H3 in Ni2, 2,6-i-Pr2C6H3 in Ni3, 2,4,6-Me3C6H2 in Ni4, 2,6-Et2-4-MeC6H2 in Ni5, and 2,4,6-t-Bu3C6H2 in Ni6, has been prepared using a one-pot reaction of 2-(N,N-diethylaminomethyl)-6,7-dihydroquinolin-8(5H)-one with the corresponding aniline and nickel dichloride hexahydrate. The resultant complexes were characterized using elemental analysis and FT-IR spectroscopy, while the mononuclear Ni1 and Ni3 were also the subject of single-crystal X-ray diffraction study. On activation with MMAO, the complexes Ni1-Ni6 displayed good activity in ethylene oligomerization, forming hexenes (ca. 48% 1-hexene) as the major products and exhibiting thermal stability up to 50 °C under 10 atm C2H4. When MAO was applied as the cocatalyst, lower activity was observed, but the catalyst showed higher selectivity toward ethylene dimerization. It is also worth noticing that an induction period was observed as the Ni/MAO catalysts reached their peak activity after 30 min. This journal is
- Li, Jiaxin,Ma, Yanping,Hu, Xinquan,Flisak, Zygmunt,Tongling, Liang,Sun, Wen-Hua
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p. 17047 - 17052
(2020/10/27)
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- Differences in acid and catalytic properties of W incorporated spherical SiO2 and 1%Al-doped SiO2 in propene metathesis
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Propene self-metathesis to ethylene and 2-butene was investigated over tungsten-based catalysts (9 wt.% W) supported on silica and 1%Al-doped SiO2, prepared by different processes. On pure SiO2, incorporating WOx improved tungsten dispersion and formation of active tetrahedral WOx species, compared to the impregnated ones. However, negative effect was found when tungsten was incorporated in the 1%Al-doped SiO2 as the catalysts contained more crystalline WOx, lower tetrahedral species, and lower Lewis acid sites, compared to the W-imp 1Al2O3/SiO2 prepared by impregnation. Incorporating both W and Al in the SiO2 by sol-gel method may lead to suppression of bridge hydroxyl Si(OH)Al group, as a consequence more crystalline WOx was formed. Nevertheless, the abundance of Bronsted and Lewis acid was found to play important role in the propene metathesis and the secondary metathesis of 1-butene reactions than surface silanol and the presence of tetrahedral tungsten oxide species on the 1%Al-doped SiO2 supported catalysts.
- Hongrutai, Nattaphon,Panpranot, Joongjai,Praserthdam, Piyasan,Srisakwattana, Tanaya,Wannakao, Sippakorn,Watmanee, Sutasinee
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-
- Synthesis of 1,3-Butadiene from 1-Butanol on a Porous Ceramic [Fe,Cr]/γ-Al2O3(K,Ce)/α-Al2O3 Catalytic Converter
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Abstract: —A two-stage method was developed for the synthesis of 1,3-butadiene by dehydration of 1-butanol to a mixture of butenes on γ-Al2O3 granules prepared by self-propagating high-temperature synthesis (SHS) followed by dehydrogenation of the butene fraction to 1,3-butadiene using a porous ceramic catalytic SHS converter [Fe,Cr]/γ-Al2O3(K,Ce)/α-Al2O3. The dehydration of 1-butanol to the butene mixture proceeded almost completely at ~100percent selectivity on γ-Al2O3 granules obtained by SHS at 300°C, which is 50 degrees lower than on industrial gamma-alumina granules. The use of an original hybrid catalytic membrane reactor (HCMR) with selective removal of hydrogen from the reaction zone led to a ~1.3-fold increase in the yield of 1,3-butadiene at ultrapure hydrogen extraction of up to 16 mol percent of the total amount of the hydrogen product. The catalytic activity of the system did not decrease after 20 h of experiment, in contrast to its activity in the industrial process, where catalyst regeneration is performed every 8–15 min.
- Dumeignil, F.,Fedotov, A. S.,Heyte, S.,Marinova, M.,Moiseev, I. I.,Paul, S.,Simon, P.,Tsodikov, M. V.,Uvarov, V. I.
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p. 390 - 404
(2020/07/03)
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- Understanding the deactivation behavior of Pt/WO3/Al2O3 catalyst in the glycerol hydrogenolysis reaction
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The selective hydrogenolysis of glycerol to 1,3-propanediol is a highly important reaction for both improving the profitability of biodiesel and valorization of biomass. While intensive research efforts have been devoted to enhancing the catalytic activity and selectivity, little is focused on the stability although the latter is of paramount importance to practical applications. In this work, we investigated the stability of Pt/WO3/Al2O3 and observed a continuous deactivation trend during a 700 h time-on-stream run. Neither the leaching of active W nor the coking was responsible for the deactivation. Instead, XRD, HAADF-STEM and CO chemisorption results clearly showed the occurrence of significant aggregation of Pt particles, which caused a remarkable decrease of Pt-WOx interfacial sites. As a consequence, strong Br?nsted acid sites which were in situ formed by H2 dissociation at the Pt-WOx interfacial sites were reduced, leading to the deactivation of the catalyst.
- Lei, Nian,Liu, Fei,Miao, Zhili,Pan, Xiaoli,Wang, Aiqin,Wang, Hua,Zhang, Tao
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p. 1261 - 1267
(2020/03/13)
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- Bimetallic Au-Pd alloy nanoparticles supported on MIL-101(Cr) as highly efficient catalysts for selective hydrogenation of 1,3-butadiene
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Gold-palladium (Au-Pd) bimetallic nanoparticle (NP) catalysts supported on MIL-101(Cr) with Au : Pd mole ratios ranging from 1 : 3 to 3 : 1 were prepared through coimpregnation and H2reduction. Au-Pd NPs were homogeneously distributed on the MIL-101(Cr) with mean particle sizes of 5.6 nm. EDS and XPS analyses showed that bimetallic Au-Pd alloys were formed in the Au(2)Pd(1)/MIL-101(Cr). The catalytic performance of the catalysts was explored in the selective 1,3-butadiene hydrogenation at 30-80 °C on a continuous fixed bed flow quartz reactor. The bimetallic Au-Pd alloy particles stabilized by MIL-101(Cr) presented improved catalytic performance. The as-synthesized bimetallic Au(2)Pd(1)/MIL-101(Cr) with 2 : 1 Au : Pd mole ratio showed the best balance between the activity and butene selectivity in the selective 1,3-butadiene hydrogenation. The Au-Pd bimetallic-supported catalysts can be reused in at least three runs. The work affords a reference on the utilization of a MOF and alloy nanoparticles to develop high-efficiency catalysts.
- Guo, Luxia,Jiang, Shuai,Li, Yingjie,Liu, Lili,Tai, Xishi,Yan, Shijuan,Zhou, Xiaojing
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p. 33417 - 33427
(2020/09/21)
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- Deoxygenation of Epoxides with Carbon Monoxide
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The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO2 from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C?O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration.
- Maulbetsch, Theo,Jürgens, Eva,Kunz, Doris
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p. 10634 - 10640
(2020/07/30)
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- PROCESS FOR HYDROGENATION OF 1,3-BUTADIENE
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Methods of improving the selectivity of selective hydrogenation of residual 1,3-butadiene in a C4 fraction of a hydrocarbon raffinate stream in a fixed-bed reactor are described. The methods may include co-feeding a competitive chemical species that increases the mechanistic selectivity to 1- and 2-butenes while increasing isomerization selectivity to 2-butene in the product stream. The hydrogenation reactor and competitive chemical species conditions may be tailored to selectively produce butenes over butane or iso-butane, where the butenes comprise 1 -butene and/or 2-butene.
- -
-
Paragraph 0064-0086
(2020/11/12)
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- Silica-Grafted Tris(neopentyl)aluminum: A Monomeric Aluminum Solid Co-catalyst for Efficient Nickel-Catalyzed Ethene Dimerization
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A silica-supported monomeric alkylaluminum co-catalyst was prepared via surface organometallic chemistry by contacting tris(neopentyl)aluminum and partially dehydroxylated silica. This system, fully characterized by solid-state 27Al NMR spectroscopy augmented by computational studies, efficiently activates (nBu3P)2NiCl2 towards dimerization of ethene, demonstrating comparable activity to previously reported dimeric diethylaluminum chloride supported on silica. Three types of aluminum surface species have been identified: monografted tetracoordinated Al species as well as two types of bisgrafted Al species—tetra- and pentacoordinated. Of them, only the monografted Al species is proposed to be able to activate the (nBu3P)2NiCl2 complex and generate the active cationic species.
- Copéret, Christophe,Florian, Pierre,Gordon, Christopher P.,Lesage, Anne,Moroz, Ilia B.,Viger-Gravel, Jasmine
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supporting information
p. 16167 - 16172
(2020/07/04)
-
- Single-reactor conversion of ethanol to 1-/2-butenes
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A simplified processes for producing desired chemicals such as butenes from feedstock mixtures containing ethanol. In one set of embodiments this is performed in a single step, wherein a feed containing ethanol in a gas phase is passed over an acidic metal oxide catalyst having a transition metal dispersion of at least 5% on a metal oxide support. The ethanol content of the feedstock mixture may vary from 10 to 100 percent of the feed and in those non-eat applications the ethanol feed may contain water.
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Page/Page column 5
(2020/06/03)
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- Quantitative production of butenes from biomass-derived γ-valerolactone catalysed by hetero-atomic MFI zeolite
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The efficient production of light olefins from renewable biomass is a vital and challenging target to achieve future sustainable chemical processes. Here we report a hetero-atomic MFI-type zeolite (NbAlS-1), over which aqueous solutions of γ-valerolactone (GVL), obtained from biomass-derived carbohydrates, can be quantitatively converted into butenes with a yield of >99% at ambient pressure under continuous flow conditions. NbAlS-1 incorporates simultaneously niobium(v) and aluminium(iii) centres into the framework and thus has a desirable distribution of Lewis and Br?nsted acid sites with optimal strength. Synchrotron X-ray diffraction and absorption spectroscopy show that there is cooperativity between Nb(v) and the Br?nsted acid sites on the confined adsorption of GVL, whereas the catalytic mechanism for the conversion of the confined GVL into butenes is revealed by in situ inelastic neutron scattering, coupled with modelling. This study offers a prospect for the sustainable production of butene as a platform chemical for the manufacture of renewable materials.
- Lin, Longfei,Sheveleva, Alena M.,da Silva, Ivan,Parlett, Christopher M. A.,Tang, Zhimou,Liu, Yueming,Fan, Mengtian,Han, Xue,Carter, Joseph H.,Tuna, Floriana,McInnes, Eric J. L.,Cheng, Yongqiang,Daemen, Luke L.,Rudi?, Svemir,Ramirez-Cuesta, Anibal J.,Tang, Chiu C.,Yang, Sihai
-
-
- Air and Moisture Tolerant Synthesis of a Chelated bis(NHC) Methylpalladium(ii) Complex Relevant to Alkyl Migration Processes in Catalysis
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An air-and moisture-tolerant alternate synthetic pathway to the preparation of a cationic chelated bis(NHC) methylpalladium(ii) complex, [{(MesIm)2CH2}Pd(Me)(NCMe)][PF6], is described. The pathway involves the isolation of a bis(NHC) AgI complex, [{(MesIm)2CH2}2Ag2][PF6]2, via metallation of the corresponding diimidazolium salt with Ag2O followed by carbene transfer to [(COD)PdBrMe]. This new method avoids a previously reported unstable intermediate that displayed rapid decomposition at room temperature, attaining the targeted cationic methylpalladium(ii) complex in high yield. CO/ethylene copolymerisation catalysis trials are reported showing solvent dependent catalyst lifetime and copolymer yields. Preliminary ethylene insertion studies are also outlined revealing possible pathways leading towards catalyst deactivation.
- Gardiner, Michael G.,Ho, Curtis C.,McGuinness, David S.,Liu, Yi Ling
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p. 1158 - 1164
(2020/09/17)
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- New PtSn structured catalysts with ZnAl2O4 thin film for n-butane dehydrogenation reaction
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Starting from structured supports based on compact spheres coated with a thin and porous layer of ZnAl2O4, mono and bimetallic catalysts were prepared. These catalysts were applied for the n-butane dehydrogenation reaction to produce light olefins. The structured supports were synthesized by coating with: bohemite-nitrate purified method (BP) and citrate-nitrate method (C). From the characterization results, the existence of strong Pt-Sn interaction in both bimetallic catalysts with probable alloys formation was found. In the PtSn/Sp-Zn-C catalyst, where higher metallic Pt-Sn interactions were observed, most of its metallic particles have sizes between 1 and 1.5 nm, which indicates a good metallic dispersion. These properties led to a catalyst with the best catalytic behavior, thus showing high yields to butenes, and a very good stability. Moreover, the presence of a structured support improves the mass and heat transference in this reaction carried out at high temperature.
- de Miguel, Sergio,Ballarini, Adriana,Bocanegra, Sonia
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- CATALYST SYSTEMS THAT INCLUDE METAL OXIDE CO-CATALYSTS FOR THE PRODUCTION OF PROPYLENE
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Embodiments of methods of synthesizing a metathesis catalyst system, which include impregnating tungsten oxide on silica support in the presence of a precursor to produce a base catalyst; calcining the base catalyst; impregnating a metal oxide co-catalyst comprising a metal oxide onto the surface of the base catalyst to produce a doped catalyst; and calcining the doped catalyst to produce a metathesis catalyst system. Further embodiments of processes for the production of propylene, which include contacting a hydrocarbon feedstock comprising a mixture of 1-butene and 2-butene with embodiments of the metathesis catalyst system to produce, via metathesis conversion, a product stream comprising propylene.
- -
-
Paragraph 0069-0070
(2020/05/02)
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- A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite
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There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.
- Chen, Wei,Corma, Avelino,De Baerdemaeker, Trees,De Vos, Dirk E.,Dong, Zhuoya,Kolb, Ute,Lei, Chi,Müller, Ulrich,Ma, Yanhang,Marler, Bernd,Martínez, Cristina,Martínez-Triguero, Joaquín,Meng, Xiangju,Parvulescu, Andrei-Nicolae,Wu, Qinming,Xiao, Feng-Shou,Yokoi, Toshiyuki,Zhang, Weiping,Zheng, Anmin
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supporting information
p. 15649 - 15655
(2020/07/04)
-
- Olefin reaction in the catalyst and the olefin production
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PROBLEM TO BE SOLVED: To provide a catalyst for obtaining an olefin in high selectivity with a vicinal diol as a raw material.SOLUTION: A catalyst for olefination reaction for use in a reaction to produce an olefin by a reaction of a polyol, having two adjacent carbon atoms each having a hydroxy group, with hydrogen comprises: a carrier; at least one oxide selected from the group consisting of oxides of the group 6 elements and oxides of the group 7 elements supported on the carrier; and at least one metal selected from the group consisting of silver, iridium, and gold supported on the carrier.SELECTED DRAWING: None
- -
-
Paragraph 0145-0146; 0149
(2020/10/31)
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- Synthesis and catalytic performance of zeolite-Y supported on silicon carbide in n-heptane cracking
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In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ～400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrostatically attracts negatively charged aluminosilicate seeds and promotes the growth of zeolite (ZY) particles over SiC, thus leading to the formation of stable ZY?SiC supported catalysts. The supported ZY catalysts with different weight ratio of ZY and SiC were synthesized and characterized by various techniques such as XRD, SEM, SEM-EDX, SEM-mapping, TEM, STEM, FT-IR, 27Al MAS NMR and N2 sorption. The characterization of the supported ZY catalysts suggests the uniform growth of ZY particles over SiC together with the creation of hierarchical micro-mesopores assembly. In the catalytic cracking of n-heptane, the catalyst ZY?SiC-50 displayed a remarkable improvement in reaction rate when compared to commercial zeolite-Y (CBV-600) amounting to 3.5 folds enhancement. Interestingly, the light olefins yield is also substantially improved. At WHSV of 8 h?1 and 475 °C, the highest light olefin yield (24–36 %) was achieved over ZY?SiC-50 whereas the reference catalyst, CBV-600 produced lower light olefins yield (7–17 %). Moreover, the supported ZY catalyst exhibited less deactivation rates. This improved performance is attributed to the hierarchical micro-mesopores assembly created by the homogeneous dispersion of zeolite crystals on SiC which offers fast diffusion pathways for the reactants and enhanced accessibility to active sites thus leading to higher observed reaction rates and fast diffusion of products thus minimizing the occurrence of side reactions.
- Alhassan, Saeed M.,Berthod, Mikael,Dabbawala, Aasif A.,Joseph, Tony,Khan, Shaihroz,Mittal, Hemant,Morin, Stephane,Singaravel, Gnana,Vaithilingam, Balasubramanian V.,Wahedi, Yasser Al
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-
- Intermetallic GaPd2 Thin Films for Selective Hydrogenation of Acetylene
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The preparation of single-phase and catalytically active GaPd2 coatings was accomplished via DC magnetron sputtering using an intermetallic sputter target. Thin and uniform layers were deposited on borosilicate glass, Si(111) and planar as well as micro-structured stainless steel foils. The specimens were examined regarding their phase composition, film morphology and microstructure. Thin films of different layer thickness were catalytically characterized in the semi-hydrogenation of acetylene, which was conducted at 473 K and a feed gas composition of 0.5 vol.percent C2H2, 5 vol.percent H2 as well as 50 vol.percent C2H4 in helium. Pre-reduction of the catalyst was found to be essential to enhance the catalytic selectivity. Sputtered GaPd2 showed a high selectivity of 73 percent for the hydrogenation to ethylene at conversion levels above 80 percent. The surface-specific activity was strongly increased to 8.97 molacetylene·(A0·h)–1 compared to bulk- or nanoscale GaPd2 (1.93 and 0.30 molacetylene·(A0·h)–1, respectively) caused by the high specific surface area of the thin films.
- Zimmermann, René R.,Siebert, Martin,Ibrahimkutty, Shyjumon,Dittmeyer, Roland,Armbrüster, Marc
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p. 1218 - 1226
(2020/06/09)
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- NNNO-Heteroscorpionate nickel (II) and cobalt (II) complexes for ethylene oligomerization: the unprecedented formation of odd carbon number olefins
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The unprecedented observation of odd carbon number olefins is reported during nickel- catalyzed ethylene oligomerization. Two complexes based on Co (II) and Ni (II) with novel tetradentate heteroscorpionate ligand have been synthesized and fully characterized. These complexes showed the ability to oligomerize ethylene upon activation with various organoaluminum compounds (Et2AlCl, Et3Al2Cl3, EtAlCl2, MMAO). Ni (II) based catalytic systems were sufficiently more active (up to 1900 kg·mol (Ni)?1·h?1·atm?1) than Co (II) analogs and have been found to be strongly dependent on the activator composition. The use of PPh3 as an additive to catalytic systems resulted in the increase of activity up to 4,150 kg·mol (Ni)?1·h?1·atm?1 and in the alteration of selectivity. All Ni (II) based systems activated with EtAlCl2 produce up to 5 mol. percent of odd carbon number olefins; two probable mechanisms for their formation are suggested – metathesis and β-alkyl elimination.
- Zubkevich, Sergey V.,Tuskaev, Vladislav A.,Gagieva, Svetlana Ch.,Kayda, Anatoliy S.,Khrustalev, Victor N.,Pavlov, Alexander A.,Zarubin, Dmitry N.,Bulychev, Boris M.
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-
- Nickel(II) complexes with tripodal NNN ligands as homogenous and supported catalysts for ethylene oligomerization
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Four new coordination compounds of nickel (II) with derivatives of N,N-bis(pyrazol-1-ylmethyl)propylamine were synthesized; their composition and structure were confirmed with IR-spectroscopy and elemental analysis. The structures of products 13 and 15 were unambiguously established in an X-ray diffraction study. Compounds 13 and 15 crystallize in the orthorhombic space groups Pna21 and P212121 correspondingly and represent a monomeric octahedral nickel complexes, that are typical for tridentate scorpion-type ligands. New method for immobilization of nickel complexes with derivatives of N,N-bis(pyrazol-1-ylmethyl)propylamine on silica gel modified with aminopropyl groups was proposed. The EXAFS/XANES analysis indicated that Ni atom in the supported complexes adopt almost octahedral geometry, being partly surrounded by nitrogen atoms from organic ligand and partly grafted to silica surface through silanol groups, with Br? in outer coordination sphere. Both the original and the supported complexes, when activated with Et2AlCl or Et3Al2Cl3, catalyze ethylene oligomerization with the predominant formation of butene isomers. Generally, the immobilized complexes show higher activity and better selectivity towards 1-butene formation.
- Tuskaev, Vladislav A.,Zubkevich, Sergei V.,Saracheno, Daniele,Gagieva, Svetlana Ch.,Dorovatovskii, Pavel V.,Kononova, Elena G.,Khrustalev, Victor N.,Zarubin, Dmitry N.,Bulychev, Boris M.,Kissin, Yury V.
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-
- Chromium complexes based on thiophene–imine ligands for ethylene oligomerization
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A new set of Cr(III) complexes, {L}CrCl3(THF), based on thiophene–imine (2a, L?=?PhOC6H4(N═CH)-2-SC4H3; 2b, L?=?PhOC2H4(N═CH)-2-SC4H3; 2c, L?=?Ph(NH)C2H4(N═CH)-2-SC4H3; 2d, L?=?PhOC6H4(N═CH)-2-SC4H2-5-Ph; 2e, L?=?Ph(NH)C2H4(N═CH)-2-SC4H2-5-Ph) have been prepared and characterized using elemental analysis and infrared spectroscopy. Upon activation with methylaluminoxane, all the chromium complexes generated active systems affording a nonselective distribution of α-olefins with turnover frequencies in the range 9500–93?500?(mol ethylene)?(mol Cr)?1?h?1, and producing mostly oligomers (95.0–99.3?wt% of total products). Small amounts of polymer were produced in these oligomerization reactions (0.8–8.2?wt%). The catalytic activities were quite sensitive to the ligand environment. Moreover, the effects of oligomerization parameters (temperature, [Al]/[Cr] molar ratio, time) on the activity and on the product distribution were examined.
- Ferreira, Jorge,Zilz, Raquel,Boeira, Igor S.,da Silva, Sabrina M.,Casagrande, Adriana C.A.,Casagrande, Osvaldo L.
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-
- Activated Niobium and Tantalum Imido Complexes: From Tuneable Polymerization to Selective Ethylene Dimerization Systems
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The niobium and tantalum imido complexes [CpMCl2(NDipp)], [MCl3(NR)(dme)] (R=tBu, Ph, 2,6-iPr2C6H3 (Dipp), and Mes), and [TaCl3(NDipp)(tmeda)] were tested in combination with EtAlCl2 for the dimerization of ethylene. The niobium systems afforded dimers or polymers, depending on the nature of the imido ligand, with overall productivities in the range 720 to 13,720 (mol C2H4)(mol Nb)?1. The nature of the polyethylene produced (LDPE or HDPE) depended on the imido ligand and the niobium concentration at which catalysis was run. In contrast, the tantalum/dme systems all mediated ethylene dimerization with productivities of up to 4,503 (mol C2H4)(mol Ta)?1, with overall selectivities to butenes of between 73–81 wt %; selectivity within the dimer fraction to 1-butene was in the range 72 to 100 %. The productivity of [TaCl3(NDipp)(tmeda)] was six times higher than that of its dme-bearing counterpart, but at the cost of selectivity to 1-butene. For the tantalum imido-mediated ethylene dimerization the composition of the product slate formed is indicative of a metallacyclic mechanism being operative.
- Messinis, Antonis M.,Batsanov, Andrei S.,Howard, Judith A. K.,Hanton, Martin J.,Dyer, Philip W.
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p. 1756 - 1764
(2019/02/26)
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- (Arylimido)niobium(V) Complexes Containing 2-Pyridylmethylanilido Ligand as Catalyst Precursors for Ethylene Dimerization That Proceeds via Cationic Nb(V) Species
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(Arylimido)niobium(V) complexes containing 2-pyridylmethylanilido ligand Nb(NAr)X2(L) [L = 2-(2,6-Me2C6H3)NCH2(C5H4N); X = NMe2 (2a,b), OCH(CF3)2 (3a-c), Me (4a-c), CH2SiMe3 (5a); Ar = 2,6-Me2C6H3 (a), 2,6-iPr2C6H3 (b), 2-MeC6H4 (c)] have been prepared, and structures of 3a,b, 4b, and 5a were determined by X-ray crystallography. The dimethyl complexes (4a,b) exhibited catalytic activities for ethylene dimerization in the presence of methylaluminoxane (MAO), whereas the activity by 4c was negligible under the same conditions. Complex 4b showed the highest activity, and the activity at 50 °C was higher than those conducted at 25 and 80 °C. The major product was 1-butene, and 1-hexene was formed by subsequent reaction of ethylene with 1-butene accumulated in the reaction mixture. A first-order relationship between the activity [turnover frequency (TOF)] and ethylene pressure was observed, suggesting that the metal-alkyl species would play a role in this catalysis. The activities further increased remarkably upon addition of [Ph3C][B(C6F5)4] at 50 °C; TOF at the initial stage (5 min) of 2 100 000 h-1 (583 s-1) has been attained. Reactions of the dimethyl complexes (4a,b) with 1.0 equiv of [Ph3C][B(C6F5)4] in Et2O afforded [Nb(NAr)Me(L)]+[B(C6F5)4]-(Et2O)2 (6a,b), and the reaction of 6b with ethylene afforded 1-butene and 1-hexene even in the absence of MAO, clearly suggesting that the cationic species play a role in this catalysis. X-ray absorption near edge structure spectra of the catalyst solutions containing 4b (in toluene at 25 °C) and MAO (10 and 50 equiv) showed no significant differences in the pre-edge peak positions and intensities from that in the dimethyl complex (4b), strongly suggesting that both the oxidation states and the basic structures are maintained upon addition of MAO in these catalyst solutions.
- Kuboki, Masaharu,Nomura, Kotohiro
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supporting information
p. 1544 - 1559
(2019/04/17)
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- Catalytic ethylene oligomerization on cobalt(II) bis(imino)pyridine complexes bearing electron-withdrawing groups
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A series of novel bis(imino)pyridine cobalt(II) chlorides, LCoCl2, with the bis(imino)pyridine ligands bearing one or several electron-withdrawing substituents (F, Cl, Br, CF3) at the aniline moieties, have been prepared and characterized. In the presence of methylalumoxane (MAO), these complexes have demonstrated high ethylene oligo- and polymerization activity (up to 1.8·107 g products?(mol Co)?1 h?1 bar?1), affording products ranging from 1-butene and Z,E-2-butenes to strictly linear low-molecular-weight (Mn ～ 300…700) polyethylene. The dependence of the reaction outcome on the ligand structure is discussed.
- Antonov, Artem A.,Semikolenova, Nina V.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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- Selectivity Effects on N, N, N′-Cobalt Catalyzed Ethylene Dimerization/Trimerization Dictated through Choice of Aluminoxane Cocatalyst
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The cobalt(II) chloride complexes, [2-(C7H4N2H)-8-(ArN)C10H8N]CoCl2 (Ar = 2,6-Me2C6H3 Co1; 2,6-Et2C6H3 Co2; 2,6-i-Pr2
- Huang, Yongfeng,Zhang, Randi,Liang, Tongling,Hu, Xinquan,Solan, Gregory A.,Sun, Wen-Hua
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p. 1143 - 1150
(2019/03/07)
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- Selective Ethylene Dimerization by Palladium(II) Complexes Bearing a Phosphinoferrocene Sulfonate Ligand
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Palladium(II) complexes featuring the hybrid anionic ligand 1′-(diphenylphosphino)ferrocene-1-sulfonate (L-), viz., trans-(Et3NH)2[Pd(μ-Cl)Me(L-κP)]2 (1), [Pd(Me)(dmap-κN1)(L-κ2O,P)](2; dmap = 4-(dimethylamino)pyridine), and [Pd(η3-allyl)(L-κ2O,P)] (6), were synthesized and together with the previously reported compounds trans-(Et3NH)2[PdCl2(L-κP)2] and [Pd(LCY)(L-κ2O,P)] (LCY = 2-[(dimethylamino-κN)methyl]phenyl-κC1 and 2-[(methylthio-κS)methyl]phenyl-κC1) tested as precatalysts for Pd-catalyzed ethylene dimerization. Only compound 1 gave rise to an active catalyst after activation by sequential halogen removal with Tl[PF6] and Na[BAr′4] (Ar′ = 3,5-bis(trifluoromethyl)phenyl) in chloroform. Thus, the formed catalyst efficiently mediated the dimerization of ethylene showing both good activity (TOF ≈ 95 h-1) and high selectivity for 1-butene (95%) at 21 °C and 30 bar of ethylene pressure. DFT calculations have shown that the dimerization reaction is thermodynamically preferred over the formation of higher oligomers and that O,P-chelate coordination of the phosphinosulfonate ligand in all Pd(II) reaction intermediates is vital for the catalytic process. In particular, the O,P-chelating phosphinoferrocene sulfonate ligand stabilizes and electronically differentiates the reaction intermediates and favors concerted ethyl migration to coordinated ethylene giving rise to 1-butene.
- Zábransky, Martin,Oberhauser, Werner,Manca, Gabriele,Císa?ová, Ivana,?těpni?ka, Petr
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p. 1534 - 1543
(2019/03/19)
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- Ethylene oligomerization promoted by nickel-based catalysts with silicon-bridged diphosphine amine ligands
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A series of nickel complexes [Ni(L1)Br2] (C1), [Ni(L2)Br2] (C2) and [Ni(L3)Br2] (C3) (L1 = N-isopropyl-N-(((diphenylphosphanyl)methyl)dimethylsilyl)-1,1-diphenylphosphanamine, L2 = N-cyclopentyl-N-(((diphenylphosphanyl)methyl)dimethylsilyl)-1,1-diphenylphosphanamine, L3 = N-(2,6-diisopropylphenyl)-N-(((diphenylphosphanyl)methyl)dimethylsilyl)-1,1-diphenylphosphanamine) were synthesized and characterized by elemental analysis, mass spectrometry, spectroscopy and single-crystal X-ray diffraction. L1, L2 and L3 each act as bidentate ligands. Upon activation with ethylaluminum dichloride, these complexes produce efficient catalytic systems for selective dimerization of ethylene to 1-butene, with catalytic activities of 3.45 × 107?g/(molNi·h) and 95.6% butene selectivity containing 87.6% 1-butene fraction.
- Wei, Wei,Yu, Buwei,Alam, Fakhre,Huang, Yongwang,Cheng, Shaoling,Jiang, Tao
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p. 125 - 133
(2018/10/02)
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- Effects of metal oxide surface doping with phosphonic acid monolayers on alcohol dehydration activity and selectivity
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Controlling the near-surface environment of heterogeneous catalysts is of fundamental importance for high selectivity and activity. Self-assembled monolayers (SAMs) are effective tools to control reaction selectivity and activity for both supported noble metal and metal oxide catalysts. We previously demonstrated tunable dehydration activity of alcohols on phosphonic acid-modified, anatase-phase TiO2. In this work, we investigated the generality of this approach by studying the modification of other metal oxides including Al2O3, CeO2, CuO, Fe2O3, MgO, rutile-TiO2, SnO2, V2O5, WO3, ZrO2, and ZnO. Modification of these materials with phosphonic acids results in the formation of SAMs on the surface, as determined by infrared spectroscopy; studies of the thermal stability on selected catalysts indicated that the SAMs remained intact up to approximately 400 °C in inert environments. Decomposition of alcohols on these native materials resulted in dehydration, dehydrogenation, and condensation. Upon functionalization with phosphonic acid modifiers, the activity of all pathways decreased significantly, except for dehydration on CeO2, anatase-TiO2, and SnO2. We explored the properties of these oxides that may be responsible for this increase in dehydration activity using correlations to bulk properties. This analysis supported the hypothesis that phosphonic acid monolayers act as surface-level dopants for metal oxides of specific metal-oxygen bond strength and oxidation state.
- Ellis, Lucas D.,Ballesteros-Soberanas, Jordi,Schwartz, Daniel K.,Medlin, J. Will
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p. 102 - 106
(2019/01/04)
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- Effective Hydrogenolysis of Glycerol to 1,3-Propanediol over Metal-Acid Concerted Pt/WOx/Al2O3 Catalysts
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Selective cleavage of secondary C?O bond is an important yet challenging strategy in glycerol valorization, and the product 1,3-propanediol (1,3-PDO) is of great value in polyester industry. Herein, we report a series of Pt/WOx/Al2O3 catalysts for selective hydrogenolysis of glycerol in a fixed-bed reactor and obtain the highest space-time yield of 1,3-PDO (191.7*10?3 g1,3-PDO h?1 g?1 cat.) to date. Both Pt and W have substantial effects on the 1,3-PDO yield with the optimum Pt/W atomic ratio of 1/2～1/4. Spectroscopy characterizations as well as chemisorption experiments reveal that at the medium domain size of WOx, hydrogen spillover can take place to the greatest extent due to the improved dispersion of Pt and the suitable reducibility of WOx. Dehydration/dehydrogenation tests of 2-butanol suggest that strong Br?nsted acid sites are created via hydrogen dissociation at the Pt?WOx interface and spillover to the neighboring oxygen atom. Such in situ formed protons are critical to the selective cleavage of secondary C?O bonds of polyols.
- Lei, Nian,Zhao, Xiaochen,Hou, Baolin,Yang, Man,Zhou, Maoxiang,Liu, Fei,Wang, Aiqin,Zhang, Tao
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p. 3903 - 3912
(2019/07/18)
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- Controlling catalytic activity and selectivity for partial hydrogenation by tuning the environment around active sites in iridium complexes bonded to supports
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Single-site Ir(CO)2 complexes bonded to high-surface-area metal oxide supports, SiO2, TiO2, Fe2O3, CeO2, MgO, and La2O3, were synthesized by chemisorption of Ir(CO)2(acac) (acac = acetylacetonate) followed by coating with each of the following ionic liquids (ILs): 1-n-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4], 1-n-butyl-3-methylimidazolium acetate, [BMIM][Ac], and 1-(3-cyanopropyl)-3-methylimidazolium dicyanamide, [CPMIM][DCA]. Extended X-ray absorption fine structure spectroscopy showed that site-isolated iridium was bonded to oxygen atoms of the support. Electron densities on the iridium enveloped by each IL sheath/support combination were characterized by carbonyl infrared spectroscopy of the iridium gem-dicarbonyls and by X-ray absorption near-edge structure data. The electron-donor/acceptor tendencies of both the support and IL determine the activity and selectivity of the catalysts for the hydrogenation of 1,3-butadiene, with electron-rich iridium being selective for partial hydrogenation. The results resolve the effects of the IL and support as ligands; for example, the effect of the IL becomes dominant when the support has a weak electron-donor character. The combined effects of supports and ILs as ligands offer broad opportunities for tuning catalytic properties of supported metal catalysts.
- Babucci, Melike,Fang, Chia-Yu,Perez-Aguilar, Jorge E.,Hoffman, Adam S.,Boubnov, Alexey,Guan, Erjia,Bare, Simon R.,Gates, Bruce C.,Uzun, Alper
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p. 2623 - 2632
(2019/03/05)
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- Plant-mediated synthesis of AgPd/γ-Al2O3 catalysts for selective hydrogenation of 1,3-butadiene at low temperature
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In this dissertation, silver-palladium (AgPd) bimetallic nanoparticles were synthesized by a green biosynthesis method using Cacumen platycladi leaf extract, which provided both reductive and protective agents. Then the supported AgPd/γ-Al2O3 catalysts were obtained by the sol-immobilization method, and the as-biosynthesized AgPd/γ-Al2O3 catalysts with different particle sizes and compositions were used for 1,3-butadiene hydrogenation. Optimization of the catalyst preparation and selective hydrogenation parameters was performed. Using the catalyst, a 1,3-butadiene conversion of 98.2% and a butene selectivity of 88.1% were achieved. The durability experiment of AgPd/γ-Al2O3 catalysts was carried out for 50 h, and the activity decreased slightly and the selectivity almost remains the same during the 50 h, indicating their remarkable stability. The results of TEM and TG analysis showed that the size of the AgPd nanoparticles was nearly the same before and after the durability experiment, and the existence of residual biomolecules on the catalyst surface helped to prevent agglomeration and modification of the surface properties of the catalyst, which would promote desorption of the product, and then avoid intensifying the level of further hydrogenation.
- Lu, Fenfen,Sun, Daohua,Jiang, Xia
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p. 13891 - 13898
(2019/09/16)
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- Electrophilic Organoiridium(III) Pincer Complexes on Sulfated Zirconia for Hydrocarbon Activation and Functionalization
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Single-site supported organometallic catalysts bring together the favorable aspects of homogeneous and heterogeneous catalysis while offering opportunities to investigate the impact of metal-support interactions on reactivity. We report a (dmPhebox)Ir(III) (dmPhebox = 2,6-bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl) complex chemisorbed on sulfated zirconia, the molecular precursor for which was previously applied to hydrocarbon functionalization. Spectroscopic methods such as diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS), dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy, and X-ray absorption spectroscopy (XAS) were used to characterize the supported species. Tetrabutylammonium acetate was found to remove the organometallic species from the surface, enabling solution-phase analytical techniques in conjunction with traditional surface methods. Cationic character was imparted to the iridium center by its grafting onto sulfated zirconia, imbuing high levels of activity in electrophilic C-H bond functionalization reactions such as the stoichiometric dehydrogenation of alkanes, with density functional theory (DFT) calculations showing a lower barrier for β-H elimination. Catalytic hydrogenation of olefins was also facilitated by the sulfated zirconia-supported (dmPhebox)Ir(III) complex, while the homologous complex on silica was inactive under comparable conditions.
- Syed, Zoha H.,Kaphan, David M.,Perras, Frédéric A.,Pruski, Marek,Ferrandon, Magali S.,Wegener, Evan C.,Celik, Gokhan,Wen, Jianguo,Liu, Cong,Dogan, Fulya,Goldberg, Karen I.,Delferro, Massimiliano
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supporting information
p. 6325 - 6337
(2019/04/25)
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