- Levulinic acid production from Cicer arietinum, cotton, Pinus radiata and sugarcane bagasse
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Levulinic acid is a key platform chemical. Even gasoline range chemicals could be produced from levulinic acid making it a strategically significant compound. Producing levulinic acid from biomass is attractive from economic as well as environmental aspec
- Victor, Amudhavalli,Pulidindi, Indra Neel,Gedanken, Aharon
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- Selective glucose transformation by titania as a heterogeneous Lewis acid catalyst
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The Lewis acidity of phosphate-immobilized anatase TiO2 (phosphate/TiO2) has been studied to develop novel environmentally benign reaction systems. Fourier transform infrared (FT-IR) measurements suggested that most Lewis acid sites on bare and phosphate/TiO2 surface function even in water. phosphate/TiO2 exhibits high catalytic performance for selective 5-(hydroxymethyl)furfural (HMF) production from glucose in THF/water (90/10 vol.%) solution. This is attributed to water-tolerant Lewis acid sites on phosphate/TiO2 that promote step-wise conversion of glucose into HMF. The catalyst was easily recovered from reaction solution by simple decantation or filtration, and can be used repeatedly without significant loss of original activity for subsequent reactions.
- Nakajima, Kiyotaka,Noma, Ryouhei,Kitano, Masaaki,Hara, Michikazu
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- Selective conversion of cellulose to hydroxymethylfurfural in polar aprotic solvents
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Herein, we report a new reaction pathway to produce hydroxymethylfurfural (HMF) from cellulose under mild reaction conditions (140-190°C; 5 mM H 2SO4) in polar aprotic solvents (i.e. THF) without the presence of water. In this system, levoglucosan is the major decomposition product of cellulose, followed by dehydration to produce HMF. Glucose, levulinic acid, and formic acid are also produced as a result of side reactions with water, which is a by-product of dehydration. The turnover frequency for cellulose conversion increases as the water content in the solvent decreases, with conversion rates in THF being more than twenty times higher than those in water. The highest HMF yield from cellulose was 44% and the highest combined yield of HMF and levulinic from cellulose was 53%, which are nearly comparable to yields obtained in ionic liquids or biphasic systems. Moreover, the use of a low boiling point solvent, such as THF, facilitates recovery of HMF in downstream processes.
- Weingarten, Ronen,Rodriguez-Beuerman, Alexandra,Cao, Fei,Luterbacher, Jeremy S.,Alonso, David Martin,Dumesic, James A.,Huber, George W.
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- Solid acid-catalyzed cellulose hydrolysis monitored by in situ Atr-Ir spectroscopy
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The solid acid-catalyzed hydrolysis of cellulose was studied under elevated temperatures and autogenous pressures using in situ ATR-IR spectroscopy. Standards of cellulose and pure reaction products, which include glucose, fructose, hydroxymethylfurfural (HMF), levulinic acid (LA), formic acid, and other compounds, were measured in water under ambient and elevated temperatures. A combination of spectroscopic and HPLC analysis revealed that the cellulose hydrolysis proceeds first through the disruption of the glycosidic linkages of cellulose to form smaller cellulose molecules, which are readily observed by their distinctive C-O vibrational stretches. The continued disruption of the linkages in these oligomers eventually results in the formation and accumulation of monomeric glucose. The solid-acid catalyst accelerated the isomerization of glucose to fructose, which then rapidly reacted under hydrothermal conditions to form degradation products, which included HMF, LA, formic acid, and acetic acid. The formation of these species could be suppressed by decreasing the residence time of glucose in the reactor, reaction temperature, and contact with the metal reactor. The hydrolysis of regenerated cellulose proceeded faster and under milder conditions than microcrystalline cellulose, which resulted in increased glucose yield and selectivity. Vibrating acids: The solid acid-catalyzed hydrolysis of cellulose has been studied by using in situ ATR-IR spectroscopy. It is possible to monitor the formation and consumption of important products and intermediates by their distinctive vibrational characteristics under the reaction conditions. Copyright
- Zakzeski, Joseph,Grisel, Ruud J. H.,Smit, Arjan T.,Weckhuysen, Bert M.
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- In situ NMR spectroscopy: Inulin biomass conversion in ZnCl2 molten salt hydrate medium - SnCl4 addition controls product distribution
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The dehydration of inulin biomass to the platform chemicals, 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA), in ZnCl2 molten salt hydrate medium was investigated. The influence of the Lewis acid catalyst, SnCl4, on the produ
- Wang, Yingxiong,Pedersen, Christian Marcus,Qiao, Yan,Deng, Tiansheng,Shi, Jing,Hou, Xianglin
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- Synergistic catalytic effect of the ZnBr2-HCl system for levulinic acid production using microwave irradiation
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A catalytic process for the selective conversion of carbohydrates to levulinic acid is developed. A synergy in the catalytic action is observed when a combination of ZnBr2 and HCl was used as the catalyst which is attributed to the in situ generation of HBr. Carbohydrates, namely, glucose, molasses and sucrose, were employed as feedstock for levulinic acid production. Microwave irradiation of glucose either in the presence of HCl alone or both HCl and ZnBr2 as catalysts yielded the formation of levulinic acid. But the conversion of glucose to levulinic acid was much faster (only 6 min) when both HCl and ZnBr2 were employed together. The effect of the reaction parameters like, the time of irradiation, % power, and amount of substrate and catalyst on the yield of levulinic acid were studied. The reaction products in each case were analysed using 1H and 13C NMR. The yield of levulinic acid was estimated using HPLC. The maximum yield of levulinic acid obtained from glucose was 53 wt%.
- Kumar, Vijay Bhooshan,Pulidindi, Indra Neel,Gedanken, Aharon
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- A new functionalized ionic liquid for efficient glucose conversion to 5-hydroxymethyl furfural and levulinic acid
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The conversion of glucose to 5-hydroxymethyl furfural (5-HMF) and levulinic acid (LA) using ionic liquid is a promising method for producing liquid fuels from renewable resources. In this study, three types of acidic functionalized ionic liquids (FILs) were prepared and used as catalysts in the conversion of glucose to 5-HMF and LA. The prepared FILs were characterized using CHNS elemental analysis and 1H and 13C NMR. The acidity of the FILs was examined using pyridine-FTIR, Hammett and acid-base titration methods. The FIL with high acidity and with both Br?nsted and Lewis acid sites present seemed suitable for 5-HMF and LA production. Among the tested FILs, 1-sulfonic acid-3-methyl imidazolium tetrachloroferrate ([SMIM][FeCl4]) demonstrated the highest catalytic performance. The yields of 5-HMF and LA reached as high as 18% and 68%, respectively after 4 h at 150°C. The catalyst was reused five times without significant loss of activity. Furthermore, for the kinetic analysis performed for glucose conversion, the activation energy and pre-exponential factor for the reaction were 38 kJ mol-1 and 925 min-1, respectively. The experimental results demonstrated the potential of FIL as a catalyst for biomass transformation to platform chemicals under mild process condition.
- Ramli, Nur Aainaa Syahirah,Amin, Nor Aishah Saidina
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- 5-Hydroxymethylfurfural and levulinic acid derived from monosaccharides dehydration promoted by InCl3 in aqueous medium
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Indium trichloride (InCl3) was used as catalyst for the conversion of monosaccharides into 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) in aqueous medium. 5-HMF yield of 60% (10 min) and LA yield of 57% (60 min) were achieved from glucose at 180 °C with 2.5 mol% of InCl 3, and 5-HMF yield of 79% (15 min) and LA yield of 45% (60 min) were obtained from fructose under the same conditions. Moreover, the isomerization process between glucose and fructose was investigated through the comparative studies of glucose/fructose mixture with different ratios as substrates. It was found that InCl3 could not only catalyze the isomerization of glucose to fructose as well as the reverse direction, but also have the positive effects on the dehydration and conversion of monosaccharides. Based on this, a catalytic mechanism of dehydration of glucose and fructose promoted by InCl 3 was proposed.
- Shen, Yue,Sun, Jiankui,Yi, Yuxuan,Wang, Bo,Xu, Feng,Sun, Runcang
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- Effect of NaCl on the conversion of cellulose to glucose and levulinic acid via solid supported acid catalysis
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Cellulose is hydrolyzed to glucose, which is further converted to levulinic acid in the presence of Nafion, as a surface supported acid catalyst. The addition of simple alkali metal halide salts, including NaCl, provides significant enhancement to the yield. The catalyst can be recycled suggesting possible extension into a continuous flow reactor for the synthesis of the biofuel precursors.
- Potvin, Joshua,Sorlien, Erin,Hegner, Jessica,DeBoef, Brenton,Lucht, Brett L.
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- Conversion of hemicellulose into furfural using solid acid catalysts in γ-valerolactone
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Hold the water: The hemicellulose fraction of lignocellulose can be converted into furfural in high yields (80 %) using solid acid catalysts (H-mordenite) in a monophasic system with γ-valerolactone (GVL) as the solvent. Furfural degradation reactions are decreased significantly when the water concentration in GVL is minimized, thus resulting in high furfural yields. Copyright
- Gürbüz, Elif I.,Gallo, Jean Marcel R.,Alonso, David Martin,Wettstein, Stephanie G.,Lim, Wee Y.,Dumesic, James A.
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- Comparison of homogeneous and heterogeneous catalysts for glucose-to-fructose isomerization in aqueous media
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Herein, the first comparison of the mechanisms of glucose-to-fructose isomerization in aqueous media enabled by homogeneous (CrCl3 and AlCl3) and heterogeneous catalysts (Sn-beta) by using isotopic-labeling studies is reported. A pronounced kinetic isotope effect (KIE) was observed if the deuterium label was at the C2 position, thus suggesting that a hydrogen shift from the C2 to C1 positions was the rate-limiting step with the three catalysts. 13C and 1HNMR spectroscopic investigations confirmed that an intra-hydride-transfer reaction pathway was the predominant reaction channel for all three catalysts in aqueous media. Furthermore, the deuterium atom in the labeled glucose could be mapped onto hydroxymethylfurfural and formic acid through reactions that followed the isomerization step in the presence of Br?nsted acids. In all three catalysts, the active site appeared to be a bifunctional Lewis-acidic/ Br?nsted-basic site, based on a speciation model and first-principles calculations. For the first time, a mechanistic similarities between the homogeneous and heterogeneous catalysis of aldose-to-ketose isomerization is established and it is suggested that learning from homogeneous catalysis could assist in the development of improved heterogeneous catalysts. Different strokes: Isotopic-labeling experiments reveal mechanistic similarities between homogeneous and heterogeneous catalysts for the aldose-to-ketose isomerization reaction in aqueous media. An intra-hydride transfer is the dominant reaction channel for the isomerization and a Lewis acid-Br?nsted base bifunctional site is the most active site for all three catalysts. Copyright
- Choudhary, Vinit,Pinar, Ana B.,Lobo, Raul F.,Vlachos, Dionisios G.,Sandler, Stanley I.
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- Titanium hydrogenphosphate: An efficient dual acidic catalyst for 5-hydroxymethylfurfural (HMF) production
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Dual Br?nsted and Lewis acidity of solid acid catalysts enhances selective production of 5-hydroxymethylfurfural (HMF). This report describes a simple template-free synthetic approach for the preparation of titanium hydrogenphosphate (TiHP) material containing Lewis and Br?nsted acid sites. As-synthesized material has been thoroughly analyzed by several analytical methods for elucidating its structural properties, including determination of the presence of Br?nsted acidic phosphate group and measurement of total acid density. NH3-TPD data reveals high surface acidity (1.43 mmol g-1) of the TiHP, which is indeed reflects to its catalytic effectiveness for the conversion of fructose, giving 55% HMF in biphasic solvent. Glucose conversion gives better yield (35%) when the reaction was carried out in a larger reactor (2L Parr reactor), which might be due to better mechanical stirring and hence higher mixing efficiency of the reactants. Br?nsted acid sites in the catalyst facilitated the formation of furan ring opening product, levulinic acid, at higher temperatures. The catalyst shows excellent recyclability and the recovered catalyst after the 3rd cycles retained XRD and TGA characteristics.
- Alam, Md. Imteyaz,De, Sudipta,Singh, Bhagat,Saha, Basudeb,Abu-Omar, Mahdi M.
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- Conversion of hemicellulose sugars catalyzed by formic acid: Kinetics of the dehydration of D -xylose, L -arabinose, and D -glucose
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The pre-treatment of lignocellulosic biomass produces a liquid stream of hemicellulose-based sugars, which can be further converted to high-value chemicals. Formosolv pulping and the Milox process use formic acid as the fractionating agent, which can be used as the catalyst for the valorisation of hemicellulose sugars to platform chemicals. The objective of this study was to investigate the reaction kinetics of major components in the hemicelluloses fraction of biomass, that is, D-xylose, L-arabinose and D-glucose. The kinetics experiments for each sugar were performed at temperatures between 130 and 170 °C in various formic acid concentrations (10-64wt %). The implications of these kinetic models on the selectivity of each sugar to the desired products are discussed. The models were used to predict the reaction kinetics of solutions that resemble the liquid stream obtained from the fractionation process of biomass using formic acid.
- Dussan, Karla,Girisuta, Buana,Lopes, Marystela,Leahy, James J.,Hayes, Michael H. B.
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- Fructose dehydration to 5-hydroxymethylfurfural over solid acid catalysts in a biphasic system
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Different acidic heterogeneous catalysts like alumina, aluminosilicate, zirconium phosphate, niobic acid, ion-exchange resin Amberlyst-15, and zeolite MOR have been studied in fructose dehydration to 5-hydroxymethylfurfural (HMF). The acidity of these materials was characterized using temperature-programmed desorption of NH3 and IR spectroscopy of adsorbed pyridine. The nature and strength of acid sites was shown to play a crucial role in the selectivity towards HMF. Bronsted acid sites in the case of zeolites and ion-exchange resin led to high selectivities in the dehydration of fructose with an increase in selectivity with the addition of an organic phase. Lewis acidity in the case of phosphate and oxides resulted in the intensive production of humins from fructose at the initial stages of the process, whereas organic phase addition did not affect selectivity. Copyright
- Ordomsky, Vitaly V.,Van Der Schaaf, John,Schouten, Jaap C.,Nijhuis, T. Alexander
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- Oxidation of cyclohexanone and/or cyclohexanol catalyzed by Dawson-type polyoxometalates using hydrogen peroxide
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The oxidation of cyclohexanone, cyclohexanol or cyclohexanone/cyclohexanol mixture using as catalyst, Dawson-type polyoxometalates (POMs) of formula, α- and β-K6P2W18O62, α-K6P2Mo6W12O62 and α1-K7P2Mo5VW12O62 and hydrogen peroxide, carried out at 90 °C with a reaction time of 20 h, led to a high number of mono- and di-acids which were identified by GC-MS. Levulinic, 6-hydroxyhexanoic, adipic, glutaric and succinic acids, major products were evaluated by HPLC. Regardless of the substrate nature, all POMs exhibited high catalytic activity with 94–99% of conversion, whereas the formation of the different products is sensitively related to both the composition and symmetry of the POMs and the substrate nature. The main products are adipic acid in the presence of α-K6P2Mo6W12O62 and α1-K7P2Mo5VW12O62, levulinic acid in the presence of α1-K7P2Mo5VW12O62 and β-K6P2W18O62 and 6-hydroxyhexanoic acid in the presence of α- and β-K6P2W18O62. Graphical abstract: High catalytic activity was observed with?α- and?β-K6P2W18O62, α-K6P2Mo6W12O62 and α1-K7P2Mo5VW12O62 Dawson-type for the oxidation of cyclohexanone, cyclohexanol or cyclohexanone/cyclohexanol mixture, in the hydrogen peroxide presence, to several oxygenated products. Adipic, levulinic and 6-hydroxyhexanoic acids are the main products. The peroxo- species formed in situ could be the active sites.[Figure not available: see fulltext.]
- Dermeche, Leila,Idrissou, Yasmina,Mazari, Tassadit,Moudjahed, Mohammed,Rabia, Cherifa
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- Visible Light-Driven, Copper-Catalyzed Aerobic Oxidative Cleavage of Cycloalkanones
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A visible light-driven, copper-catalyzed aerobic oxidative cleavage of cycloalkanones has been presented. A variety of cycloalkanones with varying ring sizes and various α-substituents reacted well to give the distal keto acids or dicarboxylic acids with moderate to good yields.
- Xin, Hong,Duan, Xin-Hua,Yang, Mingyu,Zhang, Yiwen,Guo, Li-Na
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p. 8263 - 8273
(2021/06/30)
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- Selective C-C Bond Cleavage of Cycloalkanones by NaNO2/HCl
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A novel selective fragmentation of cycloalkanones by NaNO2/HCl has been established. The C-C bond cleavage reaction proceeds smoothly under mild conditions, selectively affording versatile keto acids or oxime acids. The methodology can streamline the synthesis of valuable chiral molecules and isocoumarins from readily available feedstocks.
- He, Tianyu,Chen, Dengfeng,Qian, Shencheng,Zheng, Yu,Huang, Shenlin
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supporting information
p. 6525 - 6529
(2021/09/02)
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- Activation of H2O2over Zr(IV). Insights from Model Studies on Zr-Monosubstituted Lindqvist Tungstates
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Zr-monosubstituted Lindqvist-type polyoxometalates (Zr-POMs), (Bu4N)2[W5O18Zr(H2O)3] (1) and (Bu4N)6[{W5O18Zr(μ-OH)}2] (2), have been employed as molecular models to unravel the mechanism of hydrogen peroxide activation over Zr(IV) sites. Compounds 1 and 2 are hydrolytically stable and catalyze the epoxidation of C?C bonds in unfunctionalized alkenes and α,β-unsaturated ketones, as well as sulfoxidation of thioethers. Monomer 1 is more active than dimer 2. Acid additives greatly accelerate the oxygenation reactions and increase oxidant utilization efficiency up to >99%. Product distributions are indicative of a heterolytic oxygen transfer mechanism that involves electrophilic oxidizing species formed upon the interaction of Zr-POM and H2O2. The interaction of 1 and 2 with H2O2 and the resulting peroxo derivatives have been investigated by UV-vis, FTIR, Raman spectroscopy, HR-ESI-MS, and combined HPLC-ICP-atomic emission spectroscopy techniques. The interaction between an 17O-enriched dimer, (Bu4N)6[{W5O18Zr(μ-OCH3)}2] (2′), and H2O2 was also analyzed by 17O NMR spectroscopy. Combining these experimental studies with DFT calculations suggested the existence of dimeric peroxo species [(μ-?2:?2-O2){ZrW5O18}2]6- as well as monomeric Zr-hydroperoxo [W5O18Zr(?2-OOH)]3- and Zr-peroxo [HW5O18Zr(?2-O2)]3- species. Reactivity studies revealed that the dimeric peroxo is inert toward alkenes but is able to transfer oxygen atoms to thioethers, while the monomeric peroxo intermediate is capable of epoxidizing C?C bonds. DFT analysis of the reaction mechanism identifies the monomeric Zr-hydroperoxo intermediate as the real epoxidizing species and the corresponding α-oxygen transfer to the substrate as the rate-determining step. The calculations also showed that protonation of Zr-POM significantly reduces the free-energy barrier of the key oxygen-transfer step because of the greater electrophilicity of the catalyst and that dimeric species hampers the approach of alkene substrates due to steric repulsions reducing its reactivity. The improved performance of the Zr(IV) catalyst relative to Ti(IV) and Nb(V) catalysts is respectively due to a flexible coordination environment and a low tendency to form energy deep-well and low-reactive Zr-peroxo intermediates.
- Abramov, Pavel A.,Carbó, Jorge J.,Chesalov, Yuriy A.,Eltsov, Ilia V.,Errington, R. John,Evtushok, Vasilii Yu.,Glazneva, Tatyana S.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Maksimchuk, Nataliya V.,Maksimov, Gennadii M.,Poblet, Josep M.,Solé-Daura, Albert,Yanshole, Vadim V.,Zalomaeva, Olga V.
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p. 10589 - 10603
(2021/09/02)
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- New syntheses of haloketo acid methyl esters and their transformation to halolactones by reductive cyclization
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A new method for haloketo acid methyl ester synthesis on the basis of the ring-opening of cyclic α,β-unsaturated ketones followed by halogenation under mild conditions is reported. Di- and tri-haloketo acid methyl esters are conveniently synthesized via the hydrolytic ring-opening reaction through this method. Halolactones were readily obtained from these haloketo acid methyl esters by reductive cyclization employing NaBH4 and trifluoroacetic acid. Derivatizations of the obtained halolactone utilizing the exo-halomethylene moiety were also demonstrated.
- China, H.,Dohi, T.,Fujitake, M.,Kageyama, N.,Kikushima, K.,Yatabe, H.
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p. 1804 - 1810
(2020/10/16)
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- CONTROLLED-RELEASE TYROSINE KINASE INHIBITOR COMPOUNDS WITH LOCALIZED PK PROPERTIES
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The present invention relates to a water-insoluble controlled-release tyrosine kinase inhibitor ( TKI ) compound for use in the treatment of a cell-proliferation disorder, wherein said water-insoluble controlled-release TKI compound releases one or more TKI drug, wherein the water-insoluble controlled-release TKI compound is administered by intra-tissue administration and wherein the total amount of TKI moieties and TKI drug molecules remaining locally in such tissue 3 days after said intra-tissue administration is at least 25% of the amount of TKI moieties or TKI drug molecules administered by said intra-tissue administration; and to related aspects.
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Page/Page column 252-253
(2021/01/22)
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- Heterogeneous epoxidation of menadione with hydrogen peroxide over the zeolite imidazolate framework ZIF-8
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The zeolite imidazolate framework ZIF-8 exhibits superior catalytic performance in the epoxidation of the electron-deficient CC bond in menadione using aqueous hydrogen peroxide as the oxidant. The catalysis has a truly heterogeneous nature and the framework structure remains intact. This is the first example of oxidation catalysis with ZIF-8.
- Evtushok, Vasilii Yu.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Kolokolov, Danil I.,Stepanov, Alexander G.,Zalomaeva, Olga V.
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supporting information
p. 12546 - 12549
(2020/10/05)
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- Nucleophilic versus Electrophilic Activation of Hydrogen Peroxide over Zr-Based Metal-Organic Frameworks
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Zr-based metal-organic frameworks (Zr-MOF) UiO-66 and UiO-67 catalyze thioether oxidation in nonprotic solvents with unprecedentedly high selectivity toward corresponding sulfones (96-99% at ca. 50% sulfide conversion with only 1 equiv of H2O2). The reaction mechanism has been investigated using test substrates, kinetic, adsorption, isotopic (18O) labeling, and spectroscopic tools. The following facts point out a nucleophilic character of the peroxo species responsible for the superior formation of sulfones: (1) nucleophilic parameter XNu = 0.92 in the oxidation of thianthrene 5-oxide and its decrease upon addition of acid; (2) sulfone to sulfoxide ratio of 24 in the competitive oxidation of methyl phenyl sulfoxide and p-Br-methyl phenyl sulfide; (3) significantly lower initial rates of methyl phenyl sulfide oxidation relative to methyl phenyl sulfoxide (kS/kSO = 0.05); and (4) positive slope ρ = +0.42 of the Hammett plot for competitive oxidation of p-substituted aryl methyl sulfoxides. Nucleophilic activation of H2O2 on Zr-MOF is also manifested by their capability of catalyzing epoxidation of electron-deficient C═C bonds in α,β-unsaturated ketones accompanied by oxidation of acetonitrile solvent. Kinetic modeling on methyl phenyl sulfoxide oxidation coupled with adsorption studies supports a mechanism that involves the interaction of H2O2 with Zr sites with the formation of a nucleophilic oxidizing species and release of water followed by oxygen atom transfer from the nucleophilic oxidant to sulfoxide that competes with water for Zr sites. The nucleophilic peroxo species coexists with an electrophilic one, ZrOOH, capable of oxygen atom transfer to nucleophilic sulfides. The predominance of nucleophilic activation of H2O2 over electrophilic one is, most likely, ensured by the presence of weak basic sites in Zr-MOFs identified by FTIR spectroscopy of adsorbed CDCl3 and quantified by adsorption of isobutyric acid.
- Chesalov, Yuriy A.,Evtushok, Vasiliy Yu.,Glazneva, Tatyana S.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Larionov, Kirill P.,Skobelev, Igor Y.,Zalomaeva, Olga V.
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- Palladium-Catalyzed Aerobic Anti-Markovnikov Oxidation of Aliphatic Alkenes to Terminal Acetals
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Terminal acetals were selectively synthesized from various unbiased aliphatic terminal alkenes and 1,2-, 1,3-, or 1,4-diols using a PdCl2(MeCN)2/CuCl catalyst system in the presence of p-toluquinone under 1 atm of O2 and mild reaction conditions. The slow addition of terminal alkenes suppressed the isomerization to internal alkenes successfully. Electron-deficient cyclic alkenes, such as p-toluquinone, were key additives to enhance the catalytic activity and the anti-Markovnikov selectivity. The halogen groups in the alkenes were found to operate as directing groups, suppressing isomerization and increasing the selectivity efficiently.
- Komori, Saki,Yamaguchi, Yoshiko,Kataoka, Yasutaka,Ura, Yasuyuki
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p. 3093 - 3099
(2019/03/29)
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- Insights into β-ketoacyl-chain recognition for β-ketoacyl-ACP utilizing AHL synthases
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Beta-ketoacyl-ACP utilizing enzymes in fatty acid, polyketide and acyl-homoserine lactone biosynthetic pathways are important targets for developing antimicrobial, anticancer and antiparasitic compounds. Published reports on successful isolation of beta-ketoacyl-ACPs in a laboratory remain scarce to date and thus most beta-ketoacyl-ACP utilizing enzymes are routinely characterized using small molecule substrates in lieu of the bonafide 3-oxoacyl-ACPs. We report the systematic investigation into the electronic, geometric and spatial aspects of beta-ketoacyl-chain recognition to develop 3-oxoacyl-ACP substrate mimics for two beta-ketoacyl-ACP utilizing quorum signal synthases.
- Nhu Lam, Mila,Dudekula, Dastagiri,Durham, Bri,Collingwood, Noah,Brown, Eric C.,Nagarajan, Rajesh
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supporting information
p. 8838 - 8841
(2018/08/17)
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- Impregnated palladium on magnetite as a water compatible catalyst for the cycloisomerization of alkynoic acid derivatives
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This work describes the catalytic activity of palladium(ii) species in the cycloisomerization of alkynoic acids and their derivatives in aqueous media as well as in Deep Eutectic Solvents (DESs), with one of the lowest metal catalyst loadings reported so far in the literature. Different substrates such as terminal and internal alkynes or alkynyl sulfonylimides were studied, obtaining selectivity either to the cyclic compound or the hydrolysed keto derivative. This new system avoids the use of harmful solvents and employs very efficient and recoverable heterogeneous catalysts.
- Saavedra, Beatriz,Pérez, Juana M.,Rodríguez-álvarez, María J.,García-álvarez, Joaquín,Ramón, Diego J.
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p. 2151 - 2157
(2018/05/23)
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- An efficient method for retro-Claisen-type C-C bond cleavage of diketones with tropylium catalyst
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The retro-Claisen reaction is frequently used in organic synthesis to access ester derivatives from 1,3-dicarbonyl precursors. The C-C bond cleavage in this reaction is usually promoted by a number of transition-metal Lewis acid catalysts or organic Br?nsted acids/bases. Herein we report a new convenient and efficient method utilizing the tropylium ion as a mild and environmentally friendly organocatalyst to mediate retro-Claisen-type reactions. Using this method, a range of synthetically valuable substances can be accessed via solvolysis of 1,3-dicarbonyl compounds.
- Hussein,Huynh,Hommelsheim,Koenigs,Nguyen
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supporting information
p. 12970 - 12973
(2018/11/23)
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- Mechanism for the formation and growth of carbonaceous spheres from sucrose by hydrothermal carbonization
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We report a new three-step mechanism for the formation and growth of carbonaceous spheres by hydrothermal carbonization of saccharides using sucrose as a precursor material. Carbonaceous spheres with small diameters and narrow size distribution were synthesized via a rapid heating route, and a notable phenomenon of a sudden drop in the mean diameter of the carbonaceous spheres at low concentration with the extension of time was observed. The morphology, chemical structure of carbonaceous spheres and the chemical composition of residual solutions were analysed by field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FT-IR) and solution 13C nuclear magnetic resonance (NMR) respectively. Based on these results, evolution of solid products is clearly revealed. The formation contains two stages, and oversaturation of primary particles attributed to autocatalysis of fructose by the yielded acid (formic acid) results in the appearance of large amounts of carbonaceous spheres in the second stage of formation, which accounts for the sudden drop in mean diameter.
- Qi, Yujie,Zhang, Mu,Qi, Lin,Qi, Yang
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p. 20814 - 20823
(2016/03/04)
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- Ruthenium(II)-Catalyzed Hydration of Terminal Alkynes in PEG-400
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The ruthenium(II)-catalyzed hydration of terminal alkynes in PEG-400 to yield methyl ketones through Markovnikov addition of water across alkyne is reported.
- Mainkar, Prathama S.,Chippala, Venkataraju,Chegondi, Rambabu,Chandrasekhar, Srivari
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supporting information
p. 1969 - 1972
(2016/08/10)
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- Hypervalent Iodine as a Terminal Oxidant in Wacker-Type Oxidation of Terminal Olefins to Methyl Ketones
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A mimic of the Wacker process for C=O bond formation in terminal olefins can be initiated by a combination of the Pd(II) and hypervalent iodine reagent, Dess-Martin periodinane to generate methyl ketones. This operationally simple and scalable method offers Markovnikov selectivity, has good functional group compatibility, and is mild and high yielding.
- Chaudhari, Dipali A.,Fernandes, Rodney A.
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p. 2113 - 2121
(2016/03/15)
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- Discovery and synthesis of cyclohexenyl derivatives as modulators of CC chemokine receptor 2 activity
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A novel cyclohexenyl series of CCR2 antagonists has been discovered. This series of small, rigid compounds exhibits submicromolar binding affinity for CCR2. Modification of the substituents on the cyclohexene ring led to the identification of potent CCR2 antagonists. Progress from initial lead 5 (IC50 = 700 nM) to (-)-38 (IC50 = 9.0 nM) is discussed.
- Brown, Gregory D.,Shi, Qing,Delucca, George V.,Batt, Douglas G.,Galella, Michael A.,Cvijic, Mary-Ellen,Liu, Rui-Qin,Qiu, Feng,Zhao, Qihong,Barrish, Joel C.,Carter, Percy H.
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p. 662 - 666
(2016/01/09)
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- METHODS OF MAKING ALKYL LACTATES AND ALKYL LEVULINATES FROM SACCHARIDES
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Unique methods have been developed to convert saccharides into value-added products such as alkyl lactates, lactic acid, alkyl levulinates, levulinic acid, and optionally alkyl formate esters and/or hydroxymethylfurfural (HMF). Useful catalysts include Lewis acid catalysts and Br?nsted acid catalysts including mineral acids, metal halides, immobilized heterogeneous catalysts functionalized with a Br?nsted acid group or a Lewis acid group, or combinations thereof. The saccharides are contacted with the catalyst in the presence of various alcohols.
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Page/Page column 8
(2015/02/25)
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- Fructose conversion in the presence of Sn(iv) catalysts exhibiting high selectivity to lactic acid
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The catalytic performance of a series of Sn(iv)-based organometallic complexes in fructose conversion was studied under several reaction conditions, and the conversion, yields, and selectivity measurements of this transformation have been evaluated. The results were compared to those obtained from non-catalysed reactions and those in the presence of a conventional catalyst (H2SO4). These organometallic Sn(iv)-based catalysts demonstrated the ability to fully convert fructose into valuable chemicals. Under particular reaction conditions, lactic acid is obtained in good yields and selectivity.
- Dos Santos, Jailma Barros,De Albuquerque, Nilson José Araújo,De Paiva E Silva Zanta, Carmen Lúcia,Meneghetti, Mario Roberto,Meneghetti, Simoni Margareti Plentz
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p. 90952 - 90959
(2015/11/11)
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- Catalytic upgrading of α-angelica lactone to levulinic acid esters under mild conditions over heterogeneous catalysts
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Butyl levulinate was prepared starting from α-angelica lactone and butanol over Amberlyst 36. Different reaction conditions were optimized, which resulted in full conversion and 94% selectivity toward the ester at 75°C. A reaction network analysis reveals pseudo-butyl levulinate and levulinic acid as intermediates in the preparation of butyl levulinate. The mild protocol was successfully applied for different alcohols and compared with the esterification of levulinic acid. Overall, this study identifies α-angelica lactone as a better candidate than levulinic acid for the heterogeneously catalysed preparation of levulinic acid esters. A catalyst screening shows that also zeolites and zirconia-based catalysts are able to catalyse the reaction. However, the transformation of the intermediate pseudo-butyl levulinate into butyl levulinate requires acid sites of sufficient strength to proceed.
- Al-Shaal, Mohammad G.,Ciptonugroho, Wirawan,Holzh?user, Fabian J.,Mensah, Joel B.,Hausoul, Peter J. C.,Palkovits, Regina
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p. 5168 - 5173
(2015/11/27)
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- One step synthesis of ethyl levulinate biofuel by ethanolysis of renewable furfuryl alcohol over hierarchical zeolite catalyst
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Ethanolysis of renewable furfuryl alcohol (FAL) to ethyl levulinate (EL) biofuel over various zeolites viz. H-ZSM-5 (microporous, medium pore), Hierarchical-HZ-5 (combination of micro- and meso pore), H-Beta (microporous, large pore) and Ultra Stable Y (USY, microporous, large pore) was studied in detail. To the best of our knowledge, probably for the first time, Hierarchical-HZ-5 synthesized by desilication post-treatment has been employed as a heterogeneous catalyst for ethanolysis of FAL. The synthesized catalysts were characterized by powder X-ray diffraction (PXRD), temperature programmed NH3 desorption (TPAD), Energy dispersive X-ray analysis (EDAX), etc. Response surface methodology (RSM) with Box-Behnken experimental design (BBD) was used to investigate the influence of three crucial process variables of ethanolysis such as ethanol to FAL molar ratio, percent catalyst loading and reaction temperature on EL yield. The optimization tool of design expert software was employed to obtain the optimum reaction parameters for FAL ethanolysis over Hierarchical-HZ-5 catalyst. Three intermediates of FAL ethanolysis reaction such as, ethoxymethylfuran (EMF), 4,5,5-triethoxypentan-2-one and diethyl ether (DEE) have been identified and quantified from the product mixture with the aid of Gas Chromatography-Mass Spectroscopy (GC-MS). Hierarchical-HZ-5 was found to be a potential catalyst for ethanolysis of FAL with 73% EL yield and 26% EMF yield at optimized process parameters.
- Nandiwale, Kakasaheb Y.,Pande, Ashwini M.,Bokade, Vijay V.
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p. 79224 - 79231
(2015/10/05)
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- From lignocellulosic biomass to lactic- and glycolic-acid oligomers: A gram-scale microwave-assisted protocol
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The conversion of lignocellulosic biomass into platform chemicals is the key step in the valorization of agricultural waste. Of the biomass-derived platform chemicals currently produced, lactic acid plays a particularly pivotal role in modern biorefineries as it is a versatile commodity chemical and building block for the synthesis of biodegradable polymers. Microwave-assisted processes that furnish lactic acid avoid harsh depolymerization conditions while cutting down reaction time and energy consumption. We herein report a flash catalytic conversion (2 min) of lignocellulosic biomass into lactic and glycolic acids under microwave irradiation. The batch procedure was successfully adapted to a microwave-assisted flow process (35 mL min-1), with the aim of designing a scalable process with higher productivity. The C2 and C4 units recovered from the depolymerization were directly used as the starting material for a solvent and catalyst-free microwave-assisted polycondensation that afforded oligomers in good yields.
- Carnaroglio, Diego,Tabasso, Silvia,Kwasek, Beata,Bogdal, Dariusz,Gaudino, Emanuela Calcio,Cravotto, Giancarlo
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p. 1342 - 1349
(2015/05/05)
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- Physical and chemical studies of tungsten carbide catalysts: Effects of Ni promotion and sulphonated carbon
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Ni promoted tungsten carbides have been shown to be an effective catalyst for cellulose conversion reaction. With the use of both in situ and ex situ techniques an investigation into the physical and chemical aspects of the Ni-promoted tungsten carbide catalyst supported on activated carbon either in pure form or functionalized with sulfuric acid was conducted. In situ XRD analysis performed during the carburization process showed that non-promoted samples formed a mixture of nanosized W2C, WC1-x and WC carbide phases. In the case of Ni promoted catalysts, in situ XRD, XANES, XPS and TEM analysis revealed that Ni aids in lowering the carburization temperature by 50 °C but also assisted in the deposition of polymeric carbon onto the catalyst surface which reduced cellulose conversion. However, the results indicate beneficial effects caused by the high carbon coverage by stopping the W2C to WC carbide phase transition. Thus, carburization of Ni promoted samples produced only W2C phase, which is stable up to 800°C. The functionalization of activated-carbon with -SO3H not only increases the hydrolysis of cellulose but also lead to a greater dispersion of Ni over the catalyst. The resulting improvement in the interaction between Ni/W/C increases the cellulose transformation in a one-pot synthesis towards the production of ethylene glycol.
- Rodella, Cristiane B.,Barrett, Dean H.,Moya, Silvia F.,Figueroa, Santiago J.A.,Pimenta, Maria T. B.,Curvelo, Antonio Aprígio S.,Teixeira Da Silva, Victor
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p. 23874 - 23885
(2015/04/14)
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- ACID-FUNCTIONALIZED POLYOLEFIN MATERIALS AND THEIR USE IN ACID-PROMOTED CHEMICAL REACTIONS
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An acid-functionalized polyolefin material that can be used as an acid catalyst in a wide range of acid-promoted chemical reactions, wherein the acid-functionalized polyolefin material includes a polyolefin backbone on which acid groups are appended. Also described is a method for the preparation of the acid catalyst in which a precursor polyolefin is subjected to ionizing radiation (e.g., electron beam irradiation) of sufficient power and the irradiated precursor polyolefin reacted with at least one vinyl monomer having an acid group thereon. Further described is a method for conducting an acid-promoted chemical reaction, wherein an acid-reactive organic precursor is contacted in liquid form with a solid heterogeneous acid catalyst comprising a polyolefin backbone of at least 1 micron in one dimension and having carboxylic acid groups and either sulfonic acid or phosphonic acid groups appended thereto.
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Paragraph 0062
(2015/03/31)
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- High-yield production of levulinic acid from cellulose and its upgrading to γ-valerolactone
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Direct catalytic conversion of cellulose to levulinic acid (LA) by niobium-based solid acids and further upgrading to γ-valerolactone (GVL) on a Ru/C catalyst were realized through sequential reactions in a reactor. Firstly, using aluminium-modified mesoporous niobium phosphate as a catalyst, cellulose can be directly converted to LA with as high as 52.9% yield in aqueous solution, even in the presence of the Ru/C catalyst. To the best of our knowledge, this is the best result over a heterogeneous catalyst so far. It was found that the type of acid (Lewis and Bronsted acids) and acid strength had an influence on the yield of LA; the doping of aluminium can enhance the strong Lewis and Bronsted acids, especially the strong Lewis acid, thus resulting in the increase of LA yield from cellulose as well as from glucose and HMF. Such an enhancement by a Lewis acid on LA yield from HMF was further confirmed by adding lanthanum trifluoroacetate [(TfO)3La], a strong Lewis acid, in the catalytic system (HCl, (TfO)3H, niobium phosphate), indicating that a suitable ratio of Lewis/Bronsted acid is important for higher selectivity to LA from HMF, as well as from cellulose. Then, after replacing N2 with H2, the generated LA in the reaction mixture can be directly converted to γ-valerolactone through hydrogenation over the Ru/C catalyst without further separation of LA. This journal is the Partner Organisations 2014.
- Ding, Daqian,Wang, Jianjian,Xi, Jinxu,Liu, Xiaohui,Lu, Guanzhong,Wang, Yanqin
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p. 3846 - 3853
(2014/08/05)
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- CONVERSION OF CARBOHYDRATES TO LEVULINIC ACID ESTERS
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The present invention relates to the field of converting carbohydrates into levulinic acid, a platform chemical for many chemical end products. More specifically the invention relates to a method for converting carbohydrates such as mono-, di- or polysaccharides, obtained from for example biomass production into a suitable levulinic acid ester in the presence of a zeolite or zeotype catalyst and a suitable alcohol, and the ester may be further converted into levulinic acid if desired.
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Page/Page column 19; 20; 22; 23
(2014/02/16)
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- Towards efficient synthesis of sugar alcohols from mono- and poly-saccharides: Role of metals, supports & promoters
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Biomass derived sugar alcohols (xylitol, arabitol) find numerous uses in the food, oral hygiene and pharmaceutical industries. Their direct synthesis from poly-saccharides, however, still remains an immense challenge. In this study, we demonstrate in detail the effects of metals, supports and promoters in enhancing the yields of sugar alcohols from mono- and poly-saccharides. We undertook synthesis of bimetallic catalysts, M-M′/S (M, metal = Pt, Ru; M′, promoter = Sn, Ga, Fe; S, support = γ-Al2O3 (AL), SiO2-Al2O3 (SA), carbon (C)) with varying metal loadings (Pt/Ru = 2, 3.5 wt%; Sn = 0.22, 0.43, 0.87, 1.5, 3.5 wt%; Ga/Fe = 0.25 wt%) by a co-impregnation method. The catalytic activities of these catalysts were evaluated in the synthesis of sugar alcohols from xylose (mono-saccharide) and hemicellulose (xylan, poly-saccharide) at 130-190 °C. Among all of the bimetallic catalysts, the Pt(3.5)Sn(0.43)/AL catalyst (50%) showed 2.8 times improvement in the yield of sugar alcohols compared to a monometallic Pt(3.5)/AL catalyst (18%). Similarly, in the xylose reaction a 2.4 times enhancement in the yield of sugar alcohols over Pt(3.5)Sn(0.43)/AL (79%) was observed compared to the 33% yield obtained with Pt(3.5)/AL. By conducting several experiments it is confirmed that the residual Cl-, which remained on the catalyst even after calcinations and reductions carried out at 400 °C, does not play any role in catalysis. The stability of the Pt(3.5)Sn(0.43)/AL catalyst confirmed by XRD and ICP analysis was responsible for achieving reproducible activity in at least 5 consecutive runs. Formation of electron deficient Sn confirmed by XPS analysis helped to polarize the carbonyl group, which in turn enhanced the sugar alcohols' yields. Formation of PtSn and Pt3Sn species was observed when Sn loading was more than 0.87%.
- Tathod, Anup P.,Dhepe, Paresh L.
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p. 4944 - 4954
(2015/01/08)
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- ALDEHYDE-SELECTIVE WACKER-TYPE OXIDATION OF UNBIASED ALKENES
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This disclosure is directed to methods of preparing organic aldehydes, each method comprising contacting a terminal olefin with an oxidizing mixture comprising: (a) a dichloro-palladium complex; (b) a copper complex; (c) a source of nitrite; under aerobic reaction conditions sufficient to convert at least a portion of the terminal olefin to an aldehyde.
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Page/Page column 0140-0149; 0155-0164; 0166-0168; 0171
(2014/10/29)
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- Metalloenzyme-mimicking supramolecular catalyst for highly active and selective intramolecular alkyne carboxylation
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Creation of synthetic catalysts with enzyme-like behavior is challenging despite strong interest in such systems. Extraction of tetrachloroaurate into the hydrophilic core of an interfacially cross-linked reverse micelle (ICRM) produced an artificial "metalloenzyme" with highly unusual catalytic properties. The ICRM pulled the substrate toward the catalytic metal, which converted it efficiently to the product that was rapidly ejected. These features enabled greatly reduced catalyst loading (30-100 times lower than typical levels used in literature examples), constant high reaction rate throughout the course of the reaction, lack of the hydrolyzed side product, and substrate selectivity unobserved in conventional gold catalysts.
- Lee, Li-Chen,Zhao, Yan
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p. 5579 - 5582
(2014/05/06)
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- Iron(III) sulfate as terminal oxidant in the synthesis of methyl ketones via wacker oxidation
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An efficient and environmentally benign method using Fe(III) sulfate as a terminal oxidant in the synthesis of methyl ketones from terminal olefins via the Wacker process is developed. The methodology offers high selectivity for a Markonikov product, shows good functional group compatibility, involves mild reaction conditions, and is operationally simple. Fe2(SO 4)3 is the sole terminal oxidant in this process. The method holds potential for future applications in organic synthesis.
- Fernandes, Rodney A.,Chaudhari, Dipali A.
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p. 5787 - 5793
(2014/07/08)
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- Synthesis of methyl ketones from terminal olefins using PdCl 2/CrO3 system mimicking the Wacker process
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An efficient synthesis of methyl ketones from terminal olefins using PdCl2/CrO3 system mimicking the Wacker process is developed. The method shows good functional groups compatibility, no aldehyde by-products and is operationally simple. CrO3 is the sole oxidant and replaces both Cu-salts and molecular oxygen, traditionally used in this process. The method holds potential for future applications in organic synthesis.
- Fernandes, Rodney A.,Bethi, Venkati
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p. 4760 - 4767
(2014/06/24)
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- B-TUD-1: A versatile mesoporous catalyst
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Novel amorphous mesoporous borosilicate, B-TUD-1, was prepared to test its performance for different sustainable reactions. The structure of the material, the effective incorporation of boron into the framework as well as the nature of incorporated boron were verified by N2-sorption, XRD, ICP-OES, TEM, NH3-desorption, MAS NMR and FTIR. The potential of these materials as catalysts was tested in two reactions under different conditions. They showed an apparently good activity and recycling potential for HMF (5-hydroxymethyl- furfural) synthesis. However leaching of boron occurred during this aqueous reaction. We could demonstrate that the leached boron was actually the catalyst of the reaction. In a second reaction, this time in organic solvent, the B-TUD-1 materials were tested for the Prins cyclisation of citronellal. A very promising activity was obtained. The catalyst could be recycled and no boron leached, as demonstrated by hot filtration experiments. The Royal Society of Chemistry 2013.
- Ranoux, Adeline,Djanashvili, Kristina,Arends, Isabel W.C.E.,Hanefeld, Ulf
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p. 21524 - 21534
(2013/11/06)
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- Aldehyde-selective wacker-type oxidation of unbiased alkenes enabled by a nitrite co-catalyst
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Breaking the rules: Reversal of the high Markovnikov selectivity of Wacker-type oxidations was accomplished using a nitrite co-catalyst. Unbiased aliphatic alkenes can be oxidized with high yield and aldehyde selectivity, and several functional groups are tolerated. 18O-labeling experiments indicate that the aldehydic O atom is derived from the nitrite salt. Copyright
- Wickens, Zachary K.,Morandi, Bill,Grubbs, Robert H.
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supporting information
p. 11257 - 11260
(2013/11/06)
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- Aqueous phase catalytic conversion of agarose to 5-hydroxymethylfurfural by metal chlorides
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The production of 5-hydroxymethylfurfural (5-HMF) from agarose catalyzed by metal chlorides was studied in aqueous phase. A series of metal chlorides, including NaCl, CaCl2, MgCl2, ZnCl2, CrCl 3, CuCl2 and FeCl3, were comparatively investigated to catalyze agarose degradation for the production of 5-HMF at temperatures of 180°C, 200 °C and 220 °C, catalyst concentration of 0.5% (w/w), 1% (w/w) and 5% (w/w), time of 0-50 min, and substrate concentration of 2% (w/w). Results revealed that alkali and alkaline earth metal chlorides, including NaCl, CaCl2 and MgCl2, resulted in higher 5-HMF yields from agarose with negligible amount of byproducts, such as levulinic acid and lactic acid, derived from further degradation reactions. 1% (w/w) MgCl 2 was the most efficient catalyst among the tested metal chlorides for 5-HMF production from agarose and resulted in both the highest yield of 40.7% and highest selectivity of 49.1% at 200 °C for 35 min. The cleavage of C-O-C bond in agarose with subsequent isomerization of galactose to its ketose was considered as a possible mechanism for formation of 5-HMF under MgCl 2 catalyzed conditions.
- Yan, Lishi,Laskar, Dhrubojyoti D.,Lee, Suh-Jane,Yang, Bin
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p. 24090 - 24098
(2013/11/19)
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- Cellulose conversion with tungstated-alumina-based catalysts: Influence of the presence of platinum and mechanistic studies
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The performances of platinum supported on tungstated alumina (Pt/AlW) in the hydrothermal conversion of cellulose at 190 °C under H2 pressure were evaluated and compared to that of Pt-free tungstated alumina (AlW). We show that the presence of Pt significantly increased the extent of conversion and led to a different product distribution with the formation of acetol and propylene glycol as the main products and a global yield of up to 40 %. Based on previous reports, we propose the formation of pyruvaldehyde on the Lewis acid sites of the tungstated alumina as a key intermediate. Pyruvaldehyde can then be transformed to acetol and propylene glycol or lactic acid depending on the presence or absence of supported Pt. Copyright
- Chambon, Flora,Rataboul, Franck,Pinel, Catherine,Cabiac, Amandine,Guillon, Emmanuelle,Essayem, Nadine
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p. 500 - 507
(2013/04/24)
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- Mediating acid-catalyzed conversion of levoglucosan into platform chemicals with various solvents
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Acid-catalyzed conversions of levoglucosan have been investigated in mono-alcohols, poly-alcohols, water, chloroform, toluene, acetone, N,N-dimethyl formamide, dimethyl sulfoxide and some mixed solvents, aiming to mediate conversion of sugars into platform chemicals with solvents. The mono-alcohols can stabilize soluble polymers and thus suppress formation of insoluble polymers. Water does not have such an effect, leading to lower yields of levulinic acid. Chloroform cannot effectively dissolve levoglucosan, leading to dissolving of levoglucosan in the catalyst and the consequent rapid polymerization. Acetone reacted with sugars, forming substantial amounts of polymer. N,N-Dimethyl formamide poisoned the acid resin catalyst, leading to negligible conversion of levoglucosan. Dimethyl sulfoxide (DMSO) mainly catalyzed the conversion of levoglucosan into 5-(hydroxymethyl)furfural (HMF), 2,5-furandicarboxaldehyde, and the sulfur ether of HMF. DMSO has a low ability to transfer protons, which helps to avoid further contact of HMF with catalytic sites and stabilizes HMF.
- Hu, Xun,Wu, Liping,Wang, Yi,Mourant, Daniel,Lievens, Caroline,Gunawan, Richard,Li, Chun-Zhu
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p. 3087 - 3098
(2013/01/15)
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- On the mechanism of selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over supported Pt and Au catalysts
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The mechanism of selective oxidation of aqueous 5-hydroxymethylfurfural (HMF) at high pH was studied over supported Pt and Au catalysts. Results from labeling experiments conducted with 18O2 and H 218O indicated that water was the source of oxygen atoms during the oxidation of HMF to 2-hydroxymethylfurancarboxylic acid (HFCA) and 2,5-furandicarboxylic acid (FDCA), presumably through direct participation of hydroxide in the catalytic cycle. Molecular oxygen was essential for the production of FDCA and played an indirect role during oxidation by removing electrons deposited into the supported metal particles. A reaction path for HMF oxidation to FDCA was proposed.
- Davis, Sara E.,Zope, Bhushan N.,Davis, Robert J.
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body text
p. 143 - 147
(2012/03/27)
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