- High-stable CuPd-Cu2O/Ti-powder catalyst for low-temperature gas-phase selective oxidation of alcohols
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Abstract The oxidation of alcohols to carbonyl compounds in gas-phase is of great importance in organic chemistry and industrial process. Herein, the catalyst CuPd-Cu2O/Ti-powder is prepared by depositing Cu(NO3)2 and Pd(NO3)2 on Ti powder support followed by in-situ activation in reaction stream, which delivers high-performance for the gas-phase oxidation of alcohols. Compared with Cu/Ti-powder and Pd/Ti-powder, CuPd-Cu2O/Ti-powder exhibits higher stability and activity in alcohol oxidation reaction. The catalyst is characterized by XRD, XPS, TEM and ICP. The results indicate that CuPd(alloy)-Cu2O formed during the reaction contributes to the high activity and stability.
- Liu, Kun,Chen, Zhaoxiang,Zou, Peipei,Wang, Yuanyuan,Dai, Liyi
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- Flash Photolysis Study of the UV Spectrum and Kinetics of Reactions of the Acetonylperoxy Radical
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The flash-photolysis-UV-absorption method was used to study the UV spectrum and the kinetics of the CH3C(O)CH2O2 radical formed in the presence of oxygen via the reaction between Cl atoms and acetone.Results were analysed in the light of the results of th
- Bridier, Isabelle,Veyret, Bernard,Lesclaux, Robert,Jenkin, Michael E.
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- High-pressure fast-pyrolysis, fast-hydropyrolysis and catalytic hydrodeoxygenation of cellulose: Production of liquid fuel from biomass
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A lab-scale, high-pressure, continuous-flow fast-hydropyrolysis and vapor-phase catalytic hydrodeoxygenation (HDO) reactor has been successfully designed, built and tested with cellulose as a model biomass feedstock. We investigated the effects of pyrolysis temperature on high-pressure cellulose fast-pyrolysis, hydrogen on high-pressure cellulose fast-hydropyrolysis, reaction pressure (27 bar and 54 bar) on our reactor performance and candidate catalysts for downstream catalytic HDO of cellulose fast-hydropyrolysis vapors. In this work, a liquid chromatography-mass spectrometry (LC-MS) method has been developed and utilized for quantitative characterization of the liquid products. The major compounds in the liquid from cellulose fast-pyrolysis (27 bar, 520 °C) are levoglucosan and its isomers, formic acid, glycolaldehyde, and water, constituting 51 wt%, 11 wt%, 8 wt% and 24 wt% of liquid respectively. Our results show that high pressures of hydrogen do not have a significant effect on the fast-hydropyrolysis of cellulose at 480 °C but suppress the formation of reactive light oxygenate species like glycolaldehyde and formic acid at 580 °C. The formation of permanent gases (CO, CO2, CH4) and glycolaldehyde and formic acid increased with increasing pyrolysis temperature in the range of 480 °C-580 °C in high-pressure cellulose fast-pyrolysis, in the absence of hydrogen. Candidate HDO catalysts Al 2O3, 2% Ru/Al2O3 and 2% Pt/Al 2O3 resulted in extents of deoxygenation of 20%, 22% and 27%, respectively, but led to carbon loss to gas phase as CO and CH4. These catalysts provide useful insights for other candidate HDO catalysts for improving the extent of deoxygenation with higher carbon recovery in the liquid product.
- Venkatakrishnan, Vinod Kumar,Degenstein, John C.,Smeltz, Andrew D.,Delgass, W. Nicholas,Agrawal, Rakesh,Ribeiro, Fabio H.
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- Catalytic performance of Pt/AlPO4 catalysts for selective hydrogenolysis of glycerol to 1,3-propanediol in the vapour phase
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Hydrogenolysis of glycerol to 1,3-propanediol was investigated in the vapour phase over a series of Pt/AlPO4 catalysts with platinum loadings ranging from 0.5 to 3 wt%. The catalysts were prepared by a wet impregnation method and characterized by various techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), BET surface area, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and CO-chemisorption methods. Ex situ pyridine adsorbed FTIR analysis and temperature programmed desorption (TPD) of NH3 were employed to investigate the acidic properties of the catalysts. Further, the effect of reaction temperature, hydrogen flow rate, glycerol concentration and various contents of platinum (0.5 to 3 wt%) have been investigated to find the optimum reaction conditions. Superior performance with almost 100% conversion of glycerol and above 35% selectivity to 1,3-propanediol was obtained over 2 wt% Pt/AlPO4 at 260 °C and atmospheric pressure. The influence of acidity of the catalyst and its correlation to the catalytic performance (selectivity and conversion) has been studied. The high strength of weak acidic sites and Bronsted acidity of the catalyst measured by NH3-TPD and Pyr-FTIR were concluded to play a key role in selective formation of 1,3-propanediol. XRD, TEM and CO-chemisorption studies revealed that platinum was well dispersed on AlPO4 which further contributed to higher catalytic activity for glycerol hydrogenolysis. This journal is
- Priya, Samudrala Shanthi,Kumar, Vanama Pavan,Kantam, Mannepalli Lakshmi,Bhargava, Suresh K.,Chary, Komandur V. R.
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- Selective transformation of glycerol into 1,2-propanediol on several Pt/ZnO solids: Further insight into the role and origin of catalyst acidity
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Microemulsion technique allowed us to synthesize different ZnO solids with similar particle sizes and textural properties. Platinum was subsequently incorporated by deposition-precipitation and impregnation methods and solids tested for glycerol selective transformation into 1,2-PDO. Incorporation of platinum led to the creation of new (mainly Lewis) acid sites. A good correlation between conversion and acidity of Pt/ZnO solids was obtained. Interestingly, despite exhibiting some acidity, supports alone were inactive in the process which evidenced the role of the metal in dehydration of glycerol into acetol. Furthermore, as the reaction proceeded some chlorine coming from the precursor (H2PtCl6) was leached which led to the disappearance of the strongest acid sites, associated to side reactions (catalytic cracking) thus resulting in an increase in selectivity to 1,2-PDO. Eventual formation of Pt-Zn alloy upon reduction of the systems at ca. 400°C was beneficial to 1,2-PDO selectivity.
- Montes,Boutonnet,J?r?s,Marinas,Marinas,Urbano
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- The selective continuous flow synthesis of lower alcohols from polyols-a mechanistic interpretation of the results
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In an endeavour to understand the hydrogenolysis pathway of glycerol to lower alcohols over Ni on Al2O3 and SiO2 catalysts, the role of the intermediates (1,2-propanediol (1,2-PDO), 1,3-propanediol (1,3-PDO), ethylene glycol (EG) and ethanol) was investigated. Under the reaction conditions employed in this study, it was clear that the hydrogenolysis of the C-C and C-O bonds of glycerol takes place to a lesser extent as compared to dehydrogenation and dehydration which are seen as the dominating initial steps. Ethanol was produced in high selectivities (~67%) with 1,2-propanediol as feed and 1-propanol (1-PO, ~80%) was the main product obtained when 1,3-propanediol was used as feed. Ethylene glycol gave methanol and methane as products, whereas ethanol gave methane and CO2 as major products.
- Van Ryneveld, Esti,Mahomed, Abdul S.,Van Heerden, Pieter S.,Green, Mike J.,Holzapfel, Cedric,Friedrich, Holger B.
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- Double-cuvette ISES: In situ estimation of enantioselectivity and relative rate for catalyst screening
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Described is a new method for the screening of an array of catalysts, in situ, to estimate enantioselectivity and relative rates. We term this approach "double-cuvette ISES (in situ enzymatic screening)". The Co(III)-salen mediated hydrolytic kinetic resolution (HKR) of (±)-propylene oxide is used as a model reaction to demonstrate proof of principle. In two parallel cuvettes, a lower CHCl3-based organic layer is loaded with the epoxide and the chiral salen catalyst. Aqueous reporting layers, containing distinct "reporting enzymes" and their nicotinamide cofactors, are layered above the organic layers. The 1,2-propanediol enantiomers formed by the chiral catalyst diffuse into the aqueous layer and are oxidized there by the reporting enzymes at rates dependent upon the diol concentration, the R:S ratio of the diol, and the enantioselectivity of the reporting enzymes. A focused chiral salen library was constructed from seven chiral 1,2-diamines, derived from amino acid, terpenoid, and carbohydrates skeletons, and seven salicylaldehyde derivatives. Double-cuvette ISES identified a couple of interesting combinatorial hits in this salen array, wherein either the sense or magnitude of enantioselection for a given chiral diamine depends significantly upon the choice of "salicylaldehyde" partner. A comparison of predicted ee's and relative rates using this new screening tool with those independently measured is provided. Copyright
- Dey, Sangeeta,Karukurichi, Kannan R.,Shen, Weijun,Berkowitz, David B.
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- Two radical-dependent mechanisms for anaerobic degradation of the globally abundant organosulfur compound dihydroxypropanesulfonate
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2(S)-dihydroxypropanesulfonate (DHPS) is a microbial degradation product of 6-deoxy-6-sulfo-d-glucopyranose (sulfoquinovose), a component of plant sulfolipid with an estimated annual production of 1010 tons. DHPS is also at millimolar levels in highly abundant marine phytoplankton. Its degradation and sulfur recycling by microbes, thus, play important roles in the biogeochemical sulfur cycle. However, DHPS degradative pathways in the anaerobic biosphere are not well understood. Here, we report the discovery and characterization of two O2-sensitive glycyl radical enzymes that use distinct mechanisms for DHPS degradation. DHPS-sulfolyase (HpsG) in sulfate- and sulfite-reducing bacteria catalyzes C–S cleavage to release sulfite for use as a terminal electron acceptor in respiration, producing H2S. DHPS-dehydratase (HpfG), in fermenting bacteria, catalyzes C–O cleavage to generate 3-sulfopropionaldehyde, subsequently reduced by the NADH-dependent sulfopropionaldehyde reductase (HpfD). Both enzymes are present in bacteria from diverse environments including human gut, suggesting the contribution of enzymatic radical chemistry to sulfur flux in various anaerobic niches.
- Ang, Ee Lui,Cao, Peng,Chen, Jiawei,Li, Yaxin,Lin, Lianyun,Liu, Jiayi,Liu, Yangping,Liu, Yanhong,Lu, Qiang,Teng, Lin,Wei, Yifeng,Xu, Runyao,Yin, Jinyu,Yuchi, Zhiguang,Zhai, Weixiang,Zhang, Yan,Zhao, Huimin,Zheng, Yuchun
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- Chemoselective aerobic oxidation of unprotected diols catalyzed by Pd-(NHC) (NHC = N-heterocyclic carbene) complexes
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Neutral Pd(X)(η3-allyl) (X = Cl, OAc (acetate)) complexes bearing mono-coordinating NHC ligands have been synthesized, characterized and employed to catalyze the aerobic oxidation of unprotected 1,2- and 1,3-diols selectively to hydroxy ketones. A comparison of the catalytic performance of these precursors with a reference system has shown that the precursor with the ligands N,N′-bis(adamantyl)imidazol-2-ylidene and chloride is the most efficient for the chemoselective oxidation of 1,2-diols is concerned. High-pressure 1H NMR (HPNMR) experiments in combination with catalytic batch reactions have provided valuable information on the activation of the precursor as well as on the stability of the catalysts.
- Bettucci, Lorenzo,Bianchini, Claudio,Oberhauser, Werner,Hsiao, Tsun-Hung,Lee, Hon Man
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- Influence of the carrier and composition of active phase on physicochemical and catalytic properties of CuAg/ oxide catalysts for selective hydrogenolysis of glycerol
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The aim of the present study is to investigate the influence of the support and composition of the active bimetallic phase on both the physicochemical and catalytic properties of catalysts for use in glycerol hydrogenolysis reaction. Two series of catalysts with different amounts of copper oxide and/or silver supported on Al2O3 or TiO2 oxides were prepared. To determine the physicochemical properties of the catalysts, the following techniques were used: Brunauer-Emmett-Teller, reactive N2O adsorption, X-ray diffraction, and temperature-programmed reduction TPR-H2. Physicochemical characterization revealed that addition of silver modifies the redox properties of the catalysts containing copper oxide and influences their specific surface area. It was found that the type of carrier determines the catalytic activity and selectivities for desired products, strongly influencing their distribution. The Al2O3-supported catalysts were much more selective for 1,2-propanediol, whereas 1-propanol was the main reaction product for the titania-supported catalysts. The best catalysts (6Cu/Al and 2Cu/Ti) achieved 38 % glycerol conversion with 71 % selectivity for 1,2-propanediol and 44 % conversion with 62 % selectivity for 1-propanol, respectively.
- Samson,Zelazny,Grabowski,Ruggiero-Mikolajczyk,liwa,Pamin,Kornas,Lachowska
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- Chemo-enzymatic preparation of hydroxymethyl ketones
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A series of hydroxymethyl ketones 4a-g were obtained from the corresponding halogenomethyl ketones 2a-g via their transformation into acetoxymethyl ketones 3a-g by 18-crown-6 catalysed substitution with NaOAc followed by Novozyme 435 catalysed ethanolysis. This convenient chemo-enzymatic route provides a mild, heavy-metal-free alternative to the direct α-hydroxylations of methyl ketones 1a-g.
- Paizs, Csaba,Tosa, Monica,Majdik, Cornelia,Bodai, Viktoria,Novak, Lajos,Irimie, Florin-Dan,Poppe, Laszlo
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- Synthesis of different ZnO-supported metal systems through microemulsion technique and application to catalytic transformation of glycerol to acetol and 1,2-propanediol
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Different systems consisting of diverse metals (Au, Pt, Pd, Rh) supported on ZnO (5% by weight) were synthesized through the microemulsion technique (ME) and tested for glycerol hydrogenolysis, the main products being hydroxyacetone (acetol) and 1,2-propanediol (1,2-PDO). The solids synthesized using sodium borohydride as the reducing agent (B series) had smaller particle sizes as compared to the use of hydrazine (H series) which, in turn, resulted in a better catalytic performance. This synthetic method allowed us to obtain similar metal particle sizes (2-4 nm) for Pt, Pd and Rh solids in B series, whereas average gold metal particle was higher (>8 nm) which probably accounts for Au-containing systems being inactive under our experimental conditions. Reactivity order followed the sequence Rh > Pt > Pd. A comparison of the systems synthesized in the present paper through ME technique with those obtained in a previous work through the deposition-precipitation process revealed a higher activity and selectivity to acetol for the former solids which could be related to the presence of surfactant. Moreover, results suggested that metal sites could participate not only in hydrogenation of acetol to 1,2-propanediol but also in the previous dehydration step of glycerol to acetol.
- Montes,Checa,Marinas,Boutonnet,Marinas,Urbano,J?ras,Pinel
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- Hydrogenolysis through catalytic transfer hydrogenation: Glycerol conversion to 1,2-propanediol
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Important biorefinery processes imply hydrogenolysis reactions where high hydrogen pressures are required. As most of the nowadays available hydrogen gas is produced from fossil fuels there are great incentives to develop alternative technologies able to both substitute non-renewable reactants and operate at lower severity conditions. The use of hydrogen donor molecules from renewable origin can be a promising alternative to tackle simultaneously with both objectives. In the present study the use of methanol, 2-propanol and formic acid in the glycerol hydrogenolysis process to obtain 1,2-propanediol was investigated using a Ni-Cu/Al2O3 catalyst, prepared by sol-gel method, and under N2 atmosphere. A semi-continuous set-up was designed in which the donor solution was continuously fed into the autoclave reactor containing the glycerol aqueous phase. The best results in terms of glycerol conversion and 1,2-propanediol selectivity were obtained with formic acid.
- Gandarias, Inaki,Arias, Pedro Luis,Fernández, Sara G.,Requies, Jesús,El Doukkali, Mohammed,Güemez, María Belén
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- Pyrolysis of some (13)C-labeled glucans: A mechanistic study
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An isotopic labeling study has been conducted to investigate the chemical mechanisms involved in the formation of certain pyrolysis products of glucans, specifically glycolaldehyde (GA), acetol (hydroxypropanone), acetic acid, and formic acid, which are the major non-aqueous components of the distillate fraction (-60 deg C condensate) of the pyrolyzate. (13)C labels at C-1, C-2, and C-6 of the glucose rings in synthetic glucans were used to reveal the origins of this compounds.In general, the results show that each compound is formed by several different mechanisms, but suggest that only a few mechanisms predominate in each case.Glycolaldehyde derives predominantly from the C-1-C-2 segment of the glucose monomers, with C-5-C-6 also contributing significantly.Evidence is presented supporting heterolytic mechanisms which require a reducing end-group and base catalysis.Acetol derives mostly from three contiguous carbons that include a terminal carbon (C-1 or C-6), most often C-6 and most often appearing as the methyl carbon in the acetol.Acetic acid also arises most often from terminal carbons, the C-5-C-6 segment being the major source, with the methyl carbon usually deriving from C-1 or C-6.About half of the formic acid produced arises from C-1.Mechanisms derived from the chemistry of alkaline degradation and involving acylformylcarbinol intermediates are proposed.
- Ponder, Glenn R.,Richards, Geoffrey N.
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- Liquid-phase glycerol hydrogenolysis to 1,2-propanediol under nitrogen pressure using 2-propanol as hydrogen source
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2-Propanol was studied as a hydrogen donor molecule in the transfer hydrogenation process to selectively convert glycerol into 1,2-propanediol under N2 pressure and using Ni or/and Cu supported on Al2O 3 catalysts. The results were compared to those obtained under the same operating conditions but under H2 pressure. The results of the activity tests and catalyst characterization techniques (N2- physisorption, H2-chemisorption, TPD of NH3, TPR, TPO and XPS) suggest that glycerol hydrogenolysis to yield 1,2-propanediol occurred through a different mechanism regarding the origin of the hydrogen species. When atomic hydrogen came from dissolved molecular hydrogen dissociation, glycerol was first dehydrated to acetol and then hydrogenated to 1,2-propanediol. On the other hand, when the hydrogen atoms were produced from 2-propanol dehydrogenation, glycerol was directly converted to 1,2-propanediol through intermediate alkoxide formation.
- Gandarias,Arias,Requies,El Doukkali,Gueemez
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- Vapor phase hydrogenolysis of glycerol to 1,2-propanediol at atmospheric pressure over copper catalysts supported on mesoporous alumina
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The present work explores the hydrogenolysis of glycerol to produce 1,2-propanediol in vapor phase at atmospheric pressure over copper catalysts supported on mesoporous alumina. Catalysts were prepared by alumina impregnation varying CuO loading between 3 wt% and 30 wt%. The textural and structural characteristics of the catalysts were determined by N2 sorptometry (BET), powder X-ray diffraction (PXRD), temperature programmed reduction (TPR) and N2O chemisorption (copper metallic area). The characterization showed that all catalysts present textural properties characteristic of mesoporous solids, such as the adsorption isotherms which are type IV. Based both on characterization and activity results, it was possible to conclude that the yield to 1,2-propanediol presented a non-monotonic dependence on total copper metallic area. In addition, it was proved that 1,2-propanediol production is associated with the presence of highly dispersed CuO phase in the solids. Promising results were obtained with CuO(15)Al catalysts, taking into account that the performance can be improved by increasing residence time.
- Dieuzeide,de Urtiaga,Jobbagy,Amadeo
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- Selective conversion of glycerol into 1,2-propanediol at ambient hydrogen pressure
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The vapor-phase reaction of glycerol was performed over a copper-alumina catalyst at ambient hydrogen pressure. Glycerol was converted into 1,2-propanediol (PDO) through dehydrationhydrogenation via hydroxyacetone (HA). We also found that 1,2-PDO was produced at the selectivity higher than 93 mol % in hydrogen flow at gradient temperatures: the dehydrogenation into HA was catalyzed at around 180-200 °C, while the following hydrogenation into 1,2-PDO was catalyzed by Cu-alumina catalyst at around 145-160°C. Copyright
- Sato, Satoshi,Akiyama, Masaki,Inui, Kanichiro,Yokota, Masahiro
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- Chemoselective aerobic diol oxidation by palladium(II)-pyridine catalysis
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Neutral and cationic palladium complexes that bear pyridine ligands [i.e., pyridine (Py), 4-ethylpyridine (4-EtPy) and 2,4,6-trimethylpyridine (2,4,6-Me3Py)] have been isolated and characterized in solution by 1H and 13C{1H} NMR spectroscopy, cyclic voltammetry (CV) and in the solid state by elemental analysis and single-crystal structure analysis. All palladium compounds have been scrutinized as a precursor to catalyze the aerobic oxidation of diols either in the presence or in the absence of an external base (i.e., K2CO3). As a result, the chemoselective production of the corresponding hydroxy ketones has been achieved. The bis-cationic palladium complex of the formula [Pd(4-EtPy)4](OTs)2 (OTs = p-toluenesulfonate) [5b(OTs)2] emerged as the most promising precursor; it outperformed the neutral precursor that consisted of trans-[Pd(OAc)2(4-EtPy) 2] (OAc = acetate) and 4-EtPy [3b/2(4-EtPy)] (2 mol-equiv.). An operando high-pressure (HPNMR) spectroscopic study with the precursor 5b(OTs)2 combined with the results obtained from catalytic reactions has provided insight into the catalytic mechanism that is operative in 5b(OTs)2-catalyzed aerobic diol oxidation reactions. Neutral and cationic palladium(II) complexes with pyridine ligands were synthesized and employed as catalyst precursors for the aerobic K2CO 3-assisted oxidation of unprotected diols to chemoselectivelygive hydroxy ketones. Within the series of catalyst precursors studied, the bis-cationic compound [Pd(4-EtPy)4](OTs)2 (Py = pyridine, OTs = p-toluenesulfonate) emerged as the most promising.
- Bettucci, Lorenzo,Bianchini, Claudio,Filippi, Jonathan,Lavacchi, Alessandro,Oberhauser, Werner
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- Synergetic effect between Cu0 and Cu+ in the Cu-Cr catalysts for hydrogenolysis of glycerol
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Active species of Cu-Cr catalysts, prepared by an epoxide-assisted sol-gel route, were investigated for the hydrogenolysis of glycerol to 1,2-propanediol. Structural characterization of the catalysts was performed by means of N 2 physisorption, X-ray diffraction, H2-temperature programmed reduction, high-resolution X-ray photoelectron spectroscopy, NH 3-temperature programmed desorption, and N2O titration. On the basis of the characterizations, the copper species on the calcined Cu-Cr catalysts and the reduced Cu-Cr catalysts were assigned. Combined with reaction results, it was found that there was not similar trend in copper metal surface area and glycerol conversion, indicating that a two-site (Cu0 and Cu+) mechanism existed in the hydrogenolysis of glycerol over Cu-Cr catalysts. Besides, the maximum conversion of glycerol was obtained when the surface Cu0/Cu+ ratio increased from 3.1 to 6.6, whereas decreased with increasing sequentially to 15.7, demonstrating that the appropriate surface Cu0/Cu+ ratio was required for optimum hydrogenation activity. Thus, the synergetic effect between the Cu0 and Cu+ was considered to be responsible for the high catalytic activity in the hydrogenolysis of glycerol, and that CuCr2O 4 played a critical role in the glycerol hydrogenolysis reaction since it could function as a "hydrogen delivery bridge".
- Xiao, Zihui,Wang, Xinkui,Xiu, Jinghai,Wang, Yuemin,Williams, Christopher T.,Liang, Changhai
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- Propylene glycol oxidation with tert-butyl hydroperoxide over Cr-containing metal-organic frameworks MIL-101 and MIL-100
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Chromium-based metal-organic frameworks MIL-101 and MIL-100 catalyzed oxidation of propylene glycol (PG) using tert-butyl hydroperoxide (TBHP) as oxidant. The main oxidation product was hydroxyacetone (HA) while minor oxidation products were acetaldehyde and acetic acid. The best results (88% selectivity toward HA at ca. 10% PG conversion) were achieved over MIL-101 using acetonitrile as solvent. In water, C[sbnd]C bond cleavage products predominated. MIL-101 and MIL-100 revealed different behavior toward adsorption of PG from MeCN solution, which affected their catalytic performances. Additives of radical chain scavengers produced a strong rate-inhibiting effect whereas the presence of molecular oxygen accelerated the reaction, suggesting radical chain mechanism of the oxidation process. The oxidation of PG over MIL-101 at 50?°C proceeded without leaching of the active metal into solution and the catalysis had the truly heterogeneous nature. The MIL-101 catalyst could be recycled without significant loss of activity and selectivity and preserved its structure during, at least three, catalytic cycles.
- Torbina, Viktoriia V.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Skobelev, Igor Y.,Vodyankina, Olga V.
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- The influence of H/D kinetic isotope effect on radiation-induced transformations of hydroxyl-containing compounds in aqueous solutions
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Vicinal diols and its derivatives can be exploited as model compounds for the investigation of radiation-induced free-radical transformations of hydroxyl-containing biomolecules such as carbohydrates, phospholipids, ribonucleotides, amino acids, and peptides. In this paper, for the first time, the prospects of isotope reinforcement approach in inhibiting free-radical transformations of hydroxyl-containing compounds in aqueous solutions are investigated on the example of radiolysis of 1,2-propanediol and 1,2-propanediol-2-d1 aqueous solutions. At an absorbed dose rate of 0.110 ± 0.003 Gy·s?1 a profound kinetic isotope effect (KIE) is observed for the non-branched chain formation of acetone, which is a final dehydration product of predominant carbon-centred radicals CH3·C(OH)CH2OH. In 0.1 and 1 M deaerated solutions at pH 7.00 ± 0.01, the values of KIE are 8.9 ± 1.7 and 15.3 ± 3.1, respectively. A rationale for the fact that a strong KIE takes place only in the case of chain processes, which may occur during free-radical transformations of vicinal diols, is also provided herein based on the results of 2-propanol and 2-propanol-2-d1 indirect radiolysis. Lastly, the lack of KIE is shown in the case of 2-butanone formation from 2,3-butanediol or 2,3-butanediol-2,3-d2. This indicates that the type (primary, secondary) of the β-carbonyl radicals formed as a result of CH3·C(OH)CH(OH)R (R = H, CH3) dehydration determines the manifestation of the effect.
- Bekish, Andrei V.,Nepachalovich, Palina S.,Shadyro, Oleg I.,Shmanai, Vadim V.
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- Gas phase dehydration of lactic acid to acrylic acid over alkaline-earth phosphates catalysts
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A series of alkaline-earth phosphates were prepared by co-precipitation method using sodium free or sodium containing precursors and evaluated for gas phase dehydration of lactic acid. The catalysts were characterized by BET measurements, X-ray diffraction, chemical analysis, XPS spectroscopy and both NH3 and CO2-TPD. After checking the stability of catalysts under feed, it was shown that selectivity to acrylic acid strongly depended on reaction temperature but not on contact time. At temperature of 380 C, values ranging from 19 to 49% were measured for the different prepared catalysts. The highest value was reached with Ba3(PO4)2 (55% for C3 products) but selectivities rather close were obtained with different other phosphates suggesting kinetic limitation. Acid-base properties measurements revealed that alkaline-earth phosphates exhibited high proportion of acidic and basic sites with same weak strength. Furthermore, correlation between acrylic selectivity of alkaline earth phosphates and the acid-base balance were clearly established for the first time: selectivity was 50% for balance close to 1 and decreased by factor two increasing this parameter to 2. Finally, FTIR spectra of spent catalysts showed alkaline-earth lactates adsorbed over the catalysts which could be reaction intermediates for dehydration of lactic acid.
- Blanco,Delichere,Millet,Loridant
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- Studies on continuous selective hydrogenolysis of glycerol over supported Cu-Co bimetallic catalysts
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Alumina supported copper-cobalt catalysts were made and screened for continuous hydrogenolysis of glycerol to 1,2-propanediol at atmospheric pressure. BET surface area, temperature-programmed reduction, X-ray diffraction, pulse N2O chemisorption, transmission electron microscopy and X-ray photoelectron spectroscopy techniques were used to derive the characteristics of the catalysts. The presence of Co in Cu/alumina significantly increased the reducibility of CuO species and also the metallic Cu surface area. The catalyst with 10%Cu-7%Co on Al2O3 afforded complete glycerol conversion with 77% selectivity to 1,2-propanediol. The catalysts activity was found to be mainly due to the existence of Cu in a highly dispersed state with a high metal surface area and synergistic interactions between the Cu-Co moieties. The influence of the reaction parameters was investigated and the best possible parameters were determined. The most active catalyst showed high stability during the time on stream analysis.
- Raju, Narsinga,Rekha, Voggu,Abhishek, Burri,Kumar, Peddagolla Mahesh,Sumana, Chenna,Lingaiah, Nakka
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- SELECTIVE OXIDATION OF ALCOHOLS BY CHROMIA-PILLARED MONTMORILLONITE CATALYST
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Selective oxidation of alcohols to the carbonyl compounds was achieved using catalytic amounts of chromia-pillared montmorillonite in the presence of tert-butyl hydroperoxide.Further, secondary hydroxy groups selectively were oxidised in presence of primary hydroxy groups in diols to give hydroxy ketones in quantitative yields.
- Choudary, B. M.,Durgaprasad, A.,Valli, V. L. K.
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- Gas-phase sugar formation using hydroxymethylene as the reactive formaldehyde isomer
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Carbohydrates (CH2O)n are the formal adducts of carbon (atoms) to water with a repeating unit that structurally resembles H–C?–OH (hydroxymethylene). Although hydroxymethylene has been suggested as a building block for sugar formation, it is a reactive species that had escaped detection until recently. Here we demonstrate that formaldehyde reacts with its isomer hydroxymethylene to give glycolaldehyde in a nearly barrierless reaction. This carbonyl–ene-type transformation operates in the absence of base and solvent at cryogenic temperatures similar to those found in extraterrestrial environments or interstellar clouds. Hydroxymethylene acts as a building block for an iterative sugar synthesis, as we demonstrate through the formation of the triose glyceraldehyde. The thermodynamically preferred ketose dihydroxyacetone does not form, and the formation of further branched sugars in the iterative synthesis presented here is unlikely. The results therefore provide a link between the well-known formose (Butlerow) reaction and sugar formation under non-aqueous conditions.
- Eckhardt, André K.,Linden, Michael M.,Wende, Raffael C.,Bernhardt, Bastian,Schreiner, Peter R.
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- Catalytic routes and oxidation mechanisms in photoreforming of polyols
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Photocatalytic reforming of biomass-derived oxygenates leads to H2 generation and evolution of CO2 via parallel formation of organic intermediates through anodic oxidations on a Rh/TiO2 photocatalyst. The reaction pathways and kinetics in the photoreforming of C3–C6 polyols were explored. Polyols are converted via direct and indirect hole transfer pathways resulting in (i) oxidative rupture of C–C bonds, (ii) oxidation to α-oxygen functionalized aldoses and ketoses (carbonyl group formation) and (iii) light-driven dehydration. Direct hole transfer to chemisorbed oxygenates on terminal Ti(IV)-OH groups, generating alkoxy-radicals that undergo ?-C–C-cleavage, is proposed for the oxidative C–C rupture. Carbonyl group formation and dehydration are attributed to indirect hole transfer at surface lattice oxygen sites [Ti?O?Ti] followed by the generation of carbon-centered radicals. Polyol chain length impacts the contribution of the oxidation mechanisms favoring the C–C bond cleavage (internal preferred over terminal) as the dominant pathway with higher polyol carbon number.
- Sanwald, Kai E.,Berto, Tobias F.,Eisenreich, Wolfgang,Gutiérrez, Oliver Y.,Lercher, Johannes A.
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- Hydrogen-free synthesis of 1,2-propanediol from glycerol over Cu-Mg-Al catalysts
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Hydrogen-free synthesis of 1,2-propanediol (1,2-PDO) from glycerol was carried out over a series of Cu-Mg-Al catalysts with different (Cu + Mg)/Al ratios. Several hydrogen donors were tested and it was found that ethanol was the best donor for this process, the efficiency of the ethanol donor reached 79.8%. Cu0.4/Mg6.28Al1.32O8.26 showed the best performance among these tested catalysts. The conversion of glycerol and selectivity of 1,2-PDO reached 95.1% and 92.2%, respectively, at 210 °C. Characterizations indicated that the activity of Cu-Mg-Al for this hydrogen-free synthesis of 1,2-PDO depended mainly on the basicity of the catalysts. Both the conversion of glycerol and selectivity to 1,2-PDO could be improved with prolonged time, reaction temperature and the amount of hydrogen donor. The reaction mechanism was proposed. The Royal Society of Chemistry 2013.
- Xia, Shuixin,Zheng, Liping,Wang, Lina,Chen, Ping,Hou, Zhaoyin
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- Enhancement of glycerol conversion to acetol in high-temperature liquid water by high-pressure carbon dioxide
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Dehydration of glycerol to acetol proceeded in high-temperature liquid water at 573 K in a batch reactor. The acetol formation rate increased with an addition of high-pressure carbon dioxide. Copyright
- Yamaguchi, Aritomo,Hiyoshi, Norihito,Sato, Osamu,Rode, Chandrashekhar V.,Shirai, Masayuki
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- The chlorination of acetone: a complex kinetic analysis
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Rate constants are reported for all of the major steps followed in the chlorination of acetone, including the chlorination of mono- and 1,1-dichloroacetone, the chlorination of hydroxyacetone, the chlorination and hydroxide-catalyzed rearrangement of 1,1-dihydroxyacetone, and the haloform cleavage of trichloroacetone. pKa values are reported for hydroxyacetone and monochloroacetone.Rate constants for the hydrolyses of chloroacetone and 1,1-dichloroacetone are reported; these reactions are probably not SN2 displacements but proceed by addition of hydroxide and intramolecular displacement.
- Guthrie, Peter J.,Cossar, John
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- OH-initiated photooxidations of 1-pentene and 2-methyl-2-propen-1-ol: Mechanism and yields of the primary carbonyl products
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The products of the gas-phase reactions of OH radicals with 1- pentene and 2-methyl-2-propen-1-ol (221MPO) at T=298±2 K and atmospheric pressure were investigated by using a 4500 L atmospheric simulation chamber that was built especially for this work. The molar yield of butyraldehyde was 0.74± 0.12 mol for the reaction of 1-pentene. This work provides the first product molar yield determination of formaldehyde (0.82±0.12 mol), 1-hydroxypropan-2-one (0.84±0.13 mol), and methacrolein (0.078±0.012 mol) from the reaction of 221MPO with OH radicals. The mechanism of this reaction is discussed in relation to the experimental results. Additionally, taking into consideration the complex mechanism, the rate coefficients of the reactions of OH with formaldehyde, 1-hydroxypropan-2- one, and methacrolein were derived at atmospheric pressure and T=298±2 K.; the obtained values were (8.9±1.6)×10-12, (2.4±1.4)×10-12, and (22.9±2.3)×10-12 cm3 molecule-1 s-1, respectively.
- Peirone, Silvina A.,Cometto, Pablo M.,Lane, Silvia I.
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- New Stereoselective Biocatalysts for Carboligation and Retro-Aldol Cleavage Reactions Derived from d-Fructose 6-Phosphate Aldolase
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d-Fructose 6-phosphate aldolase (FSA) catalyzes the asymmetric cross-aldol addition of phenylacetaldehyde and hydroxyacetone. We conducted structure-guided saturation mutagenesis of noncatalytic active-site residues to produce new FSA variants, with the goal of widening the substrate scope of the wild-type enzyme toward a range of para- A nd meta-substituted arylated aldehydes. After a single generation of mutagenesis and selection, enzymes with diverse substrate selectivity scopes were identified. The kinetic parameters and stereoselectivities for a subset of enzyme/substrate combinations were determined for the reactions in both the aldol addition and cleavage reaction directions. The achieved collection of new aldolase enzymes provides new tools for controlled asymmetric synthesis of substituted aldols.
- Ma, Huan,Engel, Sarah,Enugala, Thilak Reddy,Al-Smadi, Derar,Gautier, Candice,Widersten, Mikael
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- Catalytic performance of Ni/La2O3 materials in glycerol valorization for acetol and syngas production
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The current global tendency is to increase the use of biofuels. This tendency has generated an oversupply of glycerol, which is the primary byproduct that is formed during the production of biodiesel. An alternative use for glycerol is based on chemical transformation to high-added-value derivatives at the industrial and/or energy level. During the decomposition of gaseous glycerol, polymers, alcohols and other oxygenated compounds can be generated with a selectivity that depends on the characteristics of the catalyst used. Accordingly, in this work, the acid and base characteristics of the catalyst support and the nickel in the Ni/La2O3 were investigated, as well as their influence on selectivity toward acetol at 400 °C and syngas at 700 °C. Generally, it was determined that the use of a basic catalyst support favors glycerol dehydration with respect to the formation of acetol. Moreover, it was found that the nickel particles present in the catalyst increased yield gas fraction at high reaction temperatures with a high selectivity to the syngas.
- Hernández, Diana,López, Diana,Fernández, Jhon J.
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- Active sites in modified copper catalysts for selective liquid phase dehydration of aqueous glycerol to acetol
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We report here the influence of oxides of various metals viz. Ba, Mg, Zr, Zn, Al, and Cr in modified copper catalysts, on the formation of different copper species and acid sites responsible for dehydration of aqueous glycerol to acetol. These catalysts were prepared by a co-precipitation method, among which the catalysts having higher acid strength and predominant Bronsted acidity (Cu-Mg, Cu-Zr and Cu-Al) gave the highest acetol selectivity (76-92%), while the catalysts with lower acidity such as Cu-Zn showed very poor (25%) selectivity to acetol in spite of the highest conversion of 68%. Nevertheless, catalysts exhibiting higher activity and acetol selectivity also showed the presence of metallic Cu confirmed by XRD and XANES-EXAFS characterization. Based on these results, two different catalytic pathways have been proposed highlighting the role of Lewis and Bronsted acidity along with the metal sites in individual steps of glycerol dehydration reaction. The Royal Society of Chemistry 2013.
- Mane, Rasika B.,Yamaguchi, Aritomo,Malawadkar, Atul,Shirai, Masayuki,Rode, Chandrashekhar V.
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- Conversion of glycerol to hydroxyacetone over Cu and Ni catalysts
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The conversion of glycerol to hydroxyacetone, in gas phase and atmospheric pressure, was investigated over γ-Al2O3 and TiO2 supported copper and nickel catalysts. The catalysts were prepared by co-impregnation and pre-treated with hydrogen at 450 °C. It was studied eight different catalysts at 280 °C under nitrogen atmosphere. The higher glycerol conversion and selectivity to hydroxyacetone were obtained with the monometallic Cu/γ-Al2O3 and Cu/TiO2 catalysts. Furthermore, high selectivity to lactic acid was obtained over Cu/TiO2. These catalysts were characterized by XRD, SEM, EDS, TEM, N2-physisoption, and NH3-TPD. Furthermore, the Cu/γ-Al2O3 catalyst was studied on different reaction temperature and gas flow conditions. It was obtained that the selectivity to hydroxyacetone is favors at lower temperatures. However, the catalyst suffer deactivation. Carbonaceous deposits over the used sample were not revealed by Raman and FTIR. Finally, a regeneration treatment by oxidation–reduction reactivated the Cu/γ-Al2O3 catalyst successfully.
- Morales, Bárbara C. Miranda,Quesada, Braulio Andrés Ortega
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- Promoting effect of boron oxide on Cu/SiO2 catalyst for glycerol hydrogenolysis to 1,2-propanediol
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Cu/SiO2 catalyst has been extensively applied in glycerol hydrogenolysis for its high selectivity to 1,2-propanediol, while suffering from severe deactivation easily. B2O3 is frequently used as an additive for stabilizing active species. Thus, a series of Cu/SiO2 catalysts with various B2O3 loadings for glycerol hydrogenolysis were prepared via precipitation-gel method followed by impregnation with boric acid. These catalysts were fully characterized by ICP, BET, XRD (in situ XRD), N2O chemisorption, H2-TPR, NH 3-TPD, IR, Raman, XPS, and TEM. Addition of B2O 3 to Cu/SiO2 can greatly restrain the growth of copper particles and promote the dispersion of copper species upon calcination, reduction and reaction, which resulted in the enhanced catalytic activity and stability. The optimal 3CuB/SiO2 reached complete conversion with 98.0% 1,2-propanediol selectivity. The strong correlation between 1,2-propanediol yield and Cu surface area gave direct evidence that the active Cu species were the primary active sites for glycerol hydrogenolysis.
- Zhu, Shanhui,Gao, Xiaoqing,Zhu, Yulei,Zhu, Yifeng,Zheng, Hongyan,Li, Yongwang
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- Formation of furans upon electron-beam heating of cellulose
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Similarity between cotton cellulose and sulfate and sulfite pine celluloses in degradation during electron-beam distillation has been shown. The yield of the distillate liquid slightly depends on the type of cellulose and makes up ~60 wt %. The product liquid contains organic compounds with molecular masses of 32 to 128, of which furfural and its derivatives prevail. Electron-beam distillation can be used as an effective method for the manufacturing of furfural and other furan derivatives from cellulose (along with the traditional pentosan conversion processes). It has been shown that grinding and preheating of cellulose lead to an increase in the proportion of furfural and other furans in the condensates. Pleiades Publishing, Inc., 2011.
- Kholodkova,Ponomarev
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- Selective Cross-Acyloin Condensation Catalyzed by Thiazolium Salt. Formation of 1-Hydroxy 2-Ones from Formaldehyde and Other Aldehydes
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The condensation of formaldehyde with another aldehyde catalyzed by 3-ethylbenzothiazolium bromide in the presence of triethylamine gives selectively 1-hydroxy 2-ones.This selective cross-acyloin condensation indicates an inverse selectivity in the reactions of the conjugate base of thiazolium salt 17 and of the carbanion bound to thiazolium ring 19 toward aldehyde.
- Matsumoto, Toshihiko,Ohishi, Masafumi,Inoue, Shohei
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- Gas phase reaction of the hydroxyl radical with the unsaturated peroxyacyl nitrate CH2 = C(CH3)C(O)OONO2
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The gas phase reaction of the hydroxyl radical with the unsaturated peroxyacyl nitrate CH2C(CH3)C(O)OONO2 (MPAN) has been studied at 298 ± 2 K and atmospheric pressure. The OH-MPAN reaction rate constant relative to that of OH+ n-butyl nitrate is 2. 08 ± 0.25. This ratio, together with a literature rate constant of 1.74 ×10-12cm3molecule-1s-1 for the OH+ n-butyl nitrate reaction at 298 K, yields a rate constant of (3.6 ± 0.4) × 10-12cm3 molecule-1S-1 for the OH-MPAN reaction at 298 ± 2 K. Hydroxyacetone and formaldehyde are the major carbonyl products. The yield of hydroxyacetone, 0.59 ± 0.12, is consistent with preferential addition of OH at the unsubstituted carbon atom. Atmospheric persistence and removal processes for MPAN are briefly discussed.
- Grosjean,Williams,Grosjean
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- Stopped-Flow Studies of the Mechanisms of Ozone-Alkene Reactions in the Gas Phase: Tetramethylethylene
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The reaction of ozone with tetramethylethylene (TME) has been studied in the gas phase at 294 K and 530 Pa (4 Torr) with a stopped-flow reactor coupled to a photoionization mass spectrometer.The concentration of reactants and products were determined as a function of reaction time.The major products were (CH3)2CO, H2CO, CH3C(O)CH2OH (hydroxyacetone), and CH3C(O)C(O)H (methylglyoxal).Computer simulations of the experimentally observed temporal profiles supports the mechanism shown in the Scheme I.The "hot" ester channel R'C(O)OR''* -> products> available to the H2COO formed by ozonolysis of terminal olefins R'R''C=CH2 is not available for alkyl substituted R'R''COO.Thus the secondary chemistry for R'R''COO is substantially different from that for H2COO.
- Martinez, Richard I.,Herron, John T.
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- Palladium-Catalyzed (3+3) Annulation of Allenylethylene Carbonates with Nitrile Oxides
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In this paper, we designed and synthesized a new type of cyclic carbonates, allenylethylene carbonates (AECs). With AECs as reactive precursors, we developed palladium-catalyzed (3+3) annulation of AECs with nitrile oxides. Various AECs worked well in this reaction under mild reaction conditions. A variety of 5,6-dihydro-1,4,2-dioxazine derivatives with allenyl quaternary stereocenters can be accessed in a facile manner in high yields (≤98%).
- Pan, Ting,Gao, Xing,Yang, Sen,Wang, Lan,Hu, Yimin,Liu, Min,Wang, Wei,Wu, Yongjun,Zheng, Bing,Guo, Hongchao
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- Selective hydrogenolysis of glycerol to 1,2-propanediol using heterogeneous copper nanoparticle catalyst derived from CuAl hydrotalcite
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The copper nanoparticle catalyst prepared from CuAl hydrotalcite gives an excellent yield of 1,2-propanediol in the hydrogenolysis of glycerol. The copper nanoparticle catalyst also exhibits high durability against sintering during the hydrogenolysis reaction and can be reused without appreciable loss of activity or selectivity.
- Mizugaki, Tomoo,Arundhathi, Racha,Mitsudome, Takato,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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- Continuous catalytic process for the selective dehydration of glycerol over Cu-based mixed oxide
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The selective dehydration of glycerol to hydroxyacetone (acetol) was studied with Cu-based mixed oxides derived from hydrotalcite as catalysts in a continuous flow fix-bed reactor. Catalysts were prepared by co-precipitation and characterized by ICP, N2 adsorption, XRD, NH3-TPD, CO2-TPD, TPR and TEM. Different parameters were investigated to develop the most appropriate material as well as to determine the function of every metallic species. The optimized Cu-Mg-AlOx offered ≈60% acetol selectivity at >90% glycerol conversion (≈80% liquid yield, up to TOS = 9 h). The catalyst could be regenerated by calcination, achieving full activity recovery after five re-cycles. “In-situ” FTIR and XPS measurements evidenced that the presence of Cu, specially the most active Cu1+ species, was essential to carry out the dehydration to acetol with high reaction rates, and to form the preferred intermediate (with C[dbnd]O group); although a minor contribution from Cu0 and Cu2+ species could not be discarded.
- Concepción, Patricia,Domine, Marcelo E.,Mazarío, Jaime,Ventura, María
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- Synthesis and performance evaluation of silica-supported copper chromite catalyst for glycerol dehydration to acetol
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Abstract: Sol-gel technique was used to prepare silica-supported copper chromite catalyst from acid hydrolysis of sodium silicate. The catalyst was characterized by BET surface area, FESEM, XRD, H2-TPR and pyridine adsorption by FTIR. The catalyst was activated in a hydrogen atmosphere based on H2-TPR result. The surface acidity of the catalyst was evaluated by NH3-TPD and pyridine adsorption. XRD result of reduced catalyst showed the presence of Cu0, Cu1+ and Cr2O3 in the catalyst. Glycerol dehydration was carried out at different temperature (180?°C to 240?°C) from aqueous glycerol solution with the reduced catalyst in a batch reactor. The glycerol conversion was reached 100% with maximum acetol selectivity of 70% for highest Copper chromite loaded (40?wt%) on silica at 220?°C in atmospheric pressure. The distilled liquid product was analyzed by high-performance liquid chromatography. Oxidized catalyst and spent catalyst showed lower glycerol conversion with low acetol selectivity than the reduced form of the catalyst. This is due to the cuprous ion in the reduced form of the catalyst, which acts as Lewis acid sites in glycerol dehydration. Graphic abstract: Glycerol dehydration to acetol with reduced form of silica-supported copper chromite catalyst is reported. The reduced form of copper chromite (cuprous oxide) on silica surface acts as a lewis acid in glycerol dehydration. Cuprous oxide coordinates with terminal hydroxyl group of glycerol and forms low energy six-membered transition state in the dehydration reactions.[Figure not available: see fulltext.].
- Basu,Sen,Mukherjee
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- Hydration of Alkynes to Ketones with an Efficient and Practical Polyoxomolybdate-based Cobalt Catalyst
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Hydration of alkynes to ketones is one of the most atom economical and universal methods for the synthesis of carbonyl compounds. However, the basic reaction usually requires organic ligand catalysts or harsh reaction conditions to insert oxygen into the C≡C bond. Here, we report an inorganic ligand supported cobalt (III) catalyst, (NH4)3[CoMo6O18(OH)6], which is supported by a central cobalt (III) mononucleus and a ring-shaped pure inorganic ligand composed of six MoVIO6 octahedrons to avoid the disadvantages of expensive and unrecyclable organic ligand catalysts or noble metal catalysts. Under mild conditions, the cobalt (III) catalyst can be used for the hydration of alkynes to ketones. The catalyst is non-toxic, green, and environment friendly. The catalyst can be recycled at least six times with high activity. According to control experiments, a reasonable mechanism is provided.
- Xie, Ya,Wang, Jingjing,Wang, Yunyun,Han, Sheng,Yu, Han
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p. 4985 - 4989
(2021/10/12)
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- Selectivity Switch in the Aerobic 1,2-Propandiol Oxidation Catalyzed by Diamine-Stabilized Palladium Nanoparticles
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Palladium nanoparticles stabilized by a sterically demanding secondary diamine ligand have been synthesized by hydrogen reduction of a palladium acetate complex bearing the corresponding diimine ligand. The obtained nanoparticles were used to catalyze the aerobic oxidation of 1,2-propandiol in n-hexane, and after their heterogenization onto a high surface area carbon, in water. In n-hexane (2,4-dimethyl-1,3-dioxolan-2-yl) methanol has been obtained as major product, whereas in water acetic acid with a selectivity of >85 % has been achieved. The selectivity switch observed was a clear induced by water. The robustness of diamine-stabilized palladium nanoparticles under real aerobic oxidation conditions has been proved by recycling experiments, TEM measurements of the recovered catalysts and by comparison of its performance with that of palladium nanoparticles generated by the metal vapor synthesis technique and supported onto the same carbon in the absence of the stabilizing diamine ligand.
- Oberhauser, Werner,Evangelisti, Claudio,Capozzoli, Laura,Manca, Gabriele,Casaletto, Maria Pia,Vizza, Francesco
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p. 2896 - 2906
(2021/05/06)
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- Mesoporous silica supported phosphotungstic acid catalyst for glycerol dehydration to acrolein
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Conversion of glycerol to acrolein is a useful reaction for value-added application of biodiesel-derived glycerol and bioenergy development. The high-performance solid acid catalyst is essential to this dehydration reaction. In this paper, tungsten-based heteropolyacids (HPA) were supported on non-ordered mesoporous silica (MSU-x) to increase their dispersion and used as catalysts for glycerol dehydration to acrolein. Aiming to reveal the surface structure of HPA and resulting acidic properties, as well as the relationship between acidic properties and dehydration activity, different loadings of H3PW12O40 were supported on MSU-x (10–50 wt%) and the catalysts were characterized by X-ray diffraction (XRD), BET, SEM/TEM, UV–vis diffuse reflectance spectra (DRS), Raman and FT-IR techniques. Their acidic properties were studied by NH3-Temperature Programmed Desorption (NH3-TPD) and Pyridine adsorption methods. The molecular structure and dispersion of H3PW12O40 supported on the catalysts was revealed. The Keggin unit preserved well but with different hydration level for various loadings. The total acid concentration and respective Br?nsted/Lewis acid identification were calculated. The acrolein yield increased with H3PW12O40 loading until 30 wt% and showed less change with higher loadings. Based on the correlation of acrolein formation rate with acidic properties, the active role of Br?nsted acid and the cooperative role of Br?nsted/Lewis acid sites for glycerol dehydration to acrolein were discussed. This work provides new insight into the structure evolution of heteropolyacids and the catalyst design for the glycerol to acrolein.
- Wang, Zhiheng,Liu, Licheng
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- Citric acid modified Ni3P as a catalyst for aqueous phase reforming and hydrogenolysis of glycerol to 1,2-PDO
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Citric acid (CA) modified Ni3P catalysts with small particle sizes were prepared by H2 temperature-programmed reduction (H2-TPR) of the precursors, which were prepared by co-precipitation with Ni(NO3)2·6H2O and (NH4)2HPO4, using citric acid as the chelating agent and calcining under a N2 atmosphere. The catalytic activity of the prepared catalysts was tested in the aqueous phase reforming (APR) and hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). The effects of the CA/Ni molar ratio and reaction conditions (temperature, pressure, and time) on APR and hydrogenolysis of glycerol were investigated. The CA(1)-Ni3P catalyst exhibited the best performance at 220 °C, 0.5 MPa N2, and 8 h with 74.6% glycerol conversion and 43.2% selectivity of 1,2-PDO. The prepared CA(x)-Ni3P catalysts were characterized by XRD, N2 adsorption, Raman spectroscopy, CO-chemisorption and TEM. The addition of CA significantly enhanced the dispersion of Ni species in the precursors and enlarged the surface area of the catalyst. The residual carbonaceous species after calcination in N2 prevented the aggregation of Ni3P particles and promoted the reduction of the precursors. Compared with the unmodified Ni3P and CA(x)-Ni3P calcined in air, the CA(x)-Ni3P calcined in N2 with a smaller average particle size exhibited higher catalytic activities.
- Hu, Tianyu,Liu, Bingyu,Liu, Shan,Liu, Ying-Ya,Sun, Zhichao,Wang, Anjie,Wang, Yao,Yu, Zhiquan
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p. 21725 - 21731
(2021/12/13)
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- Superior CNT-supported bimetallic RuCu catalyst for the highly selective hydrogenolysis of glycerol to 1,2-propanediol
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Selective hydrogenation of glycerol to 1,2-propanediol (1,2-PD) is a promising route for sustainable production of platform chemicals. Herein, a bimetallic RuCu catalyst supported on multiwall carbon nanotubes (RuCu/MWCNT) is reported that shows superior catalytic performance leading to 93.4% 1,2-PD selectivity under mild reactions conditions.
- Albert, Jakob,Bukowski, Anna,Fiedler, Bodo,Sherbi, Magdy,Velichkova, Hristiana,Wesner, Anne,Wisniewski, Valea Kim
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p. 6649 - 6653
(2021/10/25)
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- PROCESSES FOR PREPARING C-4 SUGARS AND KETOSE SUGARS
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Various processes for preparing C4 aldoses and/or ketones thereof are described. Various processes are described for preparing C4 aldoses and/or ketones thereof from feed compositions comprising glycolaldehyde. Also, various processes for preparing useful downstream products and intermediates, such as erythritol and erythronic acid, from the C4 aldoses and/or ketones thereof are described.
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Page/Page column 19-21
(2021/11/20)
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- PROCESSES FOR THE PYROLYSIS OF CARBOHYDRATES
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Various processes for the pyrolysis of carbohydrates to prepare products such as glycolaldehyde are described. Also, various catalysts and processes for preparing catalysts useful for carbohydrate pyrolysis are described.
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Page/Page column 13-15
(2021/11/20)
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- Gas Phase Glycerol Valorization over Ceria Nanostructures with Well-Defined Morphologies
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Glycerol solutions were vaporized and reacted over ceria catalysts with different morphologies to investigate the relationship of product distribution to the surface facets exposed, particularly, the yield of bio-renewable methanol. Ceria was prepared with cubic, rodlike, and polyhedral morphologies via hydrothermal synthesis by altering the concentration of the precipitating agent or synthesis temperature. Glycerol conversion was found to be low over the ceria with a cubic morphology, and this was ascribed to both a low surface area and relatively high acidity. Density functional theory calculations also showed that the (100) surface is likely to be hydroxylated under reaction conditions which could limit the availability of basic sites. Methanol space-time-yields over the polyhedral ceria samples were more than four times that for the cubic material at 400 °C, where 201 g of methanol was produced per hour per kilogram of the catalyst. Under comparable glycerol conversions, we show that the rodlike and polyhedral catalysts produce a major intermediate to methanol, hydroxyacetone (HA), with a selectivity of ca. 45%, but that over the cubic sample, this was found to be 15%. This equates to a 13-fold increase in the space-time-yield of HA over the polyhedral samples compared to the cubes at 320 °C. The implications of this difference are discussed with respect to the reaction mechanism, suggesting that a different mechanism dominates over the cubic catalysts to that for rodlike and polyhedral catalysts. The strong association between exposed surface facets of ceria to high methanol yields is an important consideration for future catalyst design in this area.
- Smith, Louise R.,Sainna, Mala A.,Douthwaite, Mark,Davies, Thomas E.,Dummer, Nicholas F.,Willock, David J.,Knight, David W.,Catlow, C. Richard A.,Taylor, Stuart H.,Hutchings, Graham J.
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p. 4893 - 4907
(2021/05/04)
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- CO2 role on the glycerol conversion over catalyst containing CaO-SiO2 doped with Ag and Pt
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Solids with strong base sites of calcium-silica mixed oxides (CaO-SiO2), and zirconia (ZrO2), both doped with platinum (Pt) or argentum (Ag), were synthesized and catalytically evaluated in the dehydration of glycerol for valuable chemical intermediates production. The samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDS), Basicity measurements by CO2 temperature programmed desorption (CO2-TPD), thermal analyses (TG/DTA) and N2 adsorption–desorption isotherms. The effect of two different carrier gas, inert (N2) or a soft oxidant (CO2) over the activity and selectivity were evaluated in glycerol dehydration for all the samples. The high affinity between Ca and glycerol has effect over the product selectivity, which shows CO2 effect. The promotion with Ag or Pt (0.2 wt%) increase the glycerol conversion and change the product selectivity. The data points out to the hydrogen transfer improving due to the Pt presence. Both, Pt or Ag doping or CO2 addition as the carrier gas may inhibit the acetic acid production, over calcium containing catalyst. The promotion of ZrO2 with Ag or Pt play a less marked effect over the glycerol conversion, under CO2 or N2.
- Costa, José de Ribamar M.,Santos, Regina C.R.,Coutinho, Lucas P.,Silva, Oderlando R.,Barros, Helenilson O.,Freire, Valder N.,Valentini, Antoninho
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p. 199 - 211
(2019/02/20)
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- Vibrational Spectroscopic Characterization of Glycerol Reaction Pathways over Metal-Modified Molybdenum Carbide Surfaces
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As the production of biodiesel increases, it is economically preferable to upgrade the excess by-product, glycerol, into value-added products. Metal-modified molybdenum carbide (Mo2C) is a class of promising catalysts for this application due to their promising hydrodeoxygenation (HDO) activity. In this work, Pt, Fe and Cu were used to modify the Mo2C surface and tune the product selectivity of glycerol. Pt/Mo2C showed reforming activity to produce syngas, Fe/Mo2C cleaved all the C?O bonds of glycerol to produce propylene, while Cu/Mo2C broke only one C?O bond of glycerol to form acetol. Consecutive temperature-programmed desorption (TPD) experiments demonstrated an enhanced stability of all surfaces when compared to Mo2C. High-resolution electron energy loss spectroscopy (HREELS) characterization indicated that the Fe/Mo2C surface weakened the C?O bonds of glycerol, while the Pt/Mo2C surface showed no activity towards C?O bond cleavage. This study demonstrated that the Pt/Mo2C, Fe/Mo2C and Cu/Mo2C surfaces were active, selective and stable for converting glycerol into syngas, propylene, and acetol, respectively. The combination of TPD and HREELS also served as an example of utilizing surface spectroscopy to identify the reaction pathways and intermediates on model catalyst surfaces. This should, in turn, provide insights to guide the design of metal-modified carbide catalysts for the upgrading of biomass-derived oxygenates.
- Wan, Weiming,Lin, Zhexi,Chen, Jingguang G.
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p. 281 - 286
(2019/12/15)
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- Identification of the dehydration active sites in glycerol hydrogenolysis to 1,2-propanediol over Cu/SiO2 catalysts
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Metal–support interaction is a hot topic in catalysis, but attention has seldom been drawn to the promotional effect of metal–irreducible SiO2 interfaces. Here, Cu/SBA-15 catalysts with Cu[sbnd]O[sbnd]Si[sbnd]O[sbnd] interface structures were prepared by simple grinding, and showed high activity and selectivity to 1,2-propanediol above 97% in liquid-phase glycerol hydrogenolysis. Glycerol conversion of ground Cu/SBA-15 with 10% Cu loading was about seven times that of its impregnation counterpart. The linear relationship between turnover frequency and (Cu[sbnd]O[sbnd]Si[sbnd]O[sbnd] induced Lewis acid sites)/Cu0 ratio indicated that Cu[sbnd]O[sbnd]Si[sbnd]O[sbnd] structures were crucial for achieving excellent hydrogenolysis performance. More importantly, in situ Fourier transform infrared spectroscopy of glycerol adsorption and density functional theory calculation results confirmed that Cu[sbnd]O[sbnd]Si[sbnd]O[sbnd] species were the dominant active dehydration sites of glycerol hydrogenolysis, while the adjacent Cu sites were involved in subsequent hydrogenation of the generated hydroxyacetone.
- Shan, Jianfeng,Liu, Huan,Lu, Kuan,Zhu, Shanhui,Li, Junfen,Wang, Jianguo,Fan, Weibin
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- METHOD OF PRODUCING PROPYLENE GLYCOL
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Disclosed herein is a method useful in the process of producing propylene glycol in high purity.
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Paragraph 0009; 0081
(2020/07/31)
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- Preparation method of 1-hydroxyl-2-alkanone
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The invention discloses a preparation method of 1-hydroxyl-2-alkanone. According to the preparation method, dihydric alcohol is converted into 1-hydroxy-2-alkanone in the presence of a copper-based catalyst (a conversion step). The reaction conditions of the conversion step are as follows: the reaction temperature is 200-400 DEG C, the reaction pressure is 0.01-0.5 MPa, and the liquid hour space velocity is 0.1-10 h. The method has a high dihydric alcohol conversion rate and 1-hydroxyl-2-alkanone selectivity, and is easy for industrial implementation.
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Paragraph 0022; 0024-0025; 0027-0028; 0030-0037; 0041
(2020/07/12)
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- Gas-Phase Dehydration of Glycerol into Acrolein in the Presence of Polyoxometalates
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Abstract: The activity of catalytic systems based on polyoxometalates in the gas-phase dehydration of glycerol into acrolein has been investigated. The catalysts synthesized have been characterized using FTIR spectroscopy, X-ray phase analysis, scanning electron microscopy, and low-temperature nitrogen adsorption/desorption (BET method). It has been shown that the nature of the surface acid sites of catalysts has a significant effect on the direction of glycerol transformation. An increase in the fraction of Br?nsted acid sites in the catalyst leads to an increase in the yield of acrolein. At the same time, an increase in the fraction of Lewis acid sites in the catalyst leads to an increase to the yield of acetol, which is formed through a competing route. Among the catalytic systems considered, the best results have been obtained with the silicomolybdic acid anion supported onto alumina (SiMo/A). The main patterns of the gas-phase glycerol dehydration have been studied using SiMo/A as a catalyst, and the conditions responsible for the highest yield of acrolein have been determined.
- Belousov, A. S.,Esipovich, A. L.,Kanakov, E. A.,Otopkova, K. V.,Shishulina, A. V.,Uvarova, V. D.,Vorotyntsev, A. V.
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p. 595 - 602
(2020/08/05)
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- Catalyst for dehydration of glycerin, preparation method thereof, and production method of acrolein using the catalyst
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The present disclosure relates to a catalyst for dehydration of glycerin, a preparation method thereof, and a production method of acrolein using the catalyst. Particularly, the catalyst according to an embodiment of the present disclosure is used in a dehydration reaction of glycerin to exhibit high catalytic activity, a high yield, and high selectivity to acrolein and acrylic acid, and has a longer lifetime compared to the conventional catalysts due to a characteristic that coke carbon cannot be easily deposited on the surface of the catalyst.
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Page/Page column 13-18
(2020/03/14)
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- One-step synthesis of ethanol from glycerol in a gas phase packed bed reactor over hierarchical alkali-treated zeolite catalyst materials
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The gas-phase conversion of glycerol into ethanol in a "green" one-step synthesis over a cesium metal-promoted zeolite catalyst has been reported for the first time. To our knowledge, the CsZSM-5 based catalyst presented in this work showed one of the best yields of ethanol in the gas-phase glycerol conversion. The catalyst sample's structure, texture, and acid-base properties were characterized using numerous materials characterization techniques. The catalytic evaluation was carried out in a packed-bed continuous flow reactor. The highest ethanol yield achieved was 99.6 mol% over a 20 wt% CsZSM-5 catalyst with SiO2/Al2O3 = 1500, 10 wt% glycerol feed concentration, 350 °C reaction temperature, and GHSVtotal = 625 h-1. It was demonstrated that the best catalytic performance was related to the ample amount of surface basic sites, synergistic interaction between Cs species and the HZSM-5 zeolite and to its smaller crystallite size obtained from XRD analysis. The achieved results exhibit great potential of utilizing the alkali-treated CsZSM-5 catalyst for the gas-phase conversion of glycerol into bio-based ethanol. The possible reaction route from glycerol to renewable ethanol was proposed based on direct glycerol conversion to ethanol via the thermal monodehydration, radical fragmentation, methylation and transfer hydrogenation reactions. Finally, for the first time, methanol was directly converted into ethanol in the gas-phase continuous flow packed-bed reactor over a 20 wt% CsZSM-5 catalyst.
- Kostyniuk, Andrii,Bajec, David,Likozar, Bla?
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p. 753 - 765
(2020/02/27)
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- PtRu/Zn3Ce1Oxcatalysts with Lewis acid-base pairs show synergistic performances for the conversion of glycerol in the absence of externally added H2
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Previous studies revealed that tandem dehydration, dehydrogenation and hydrogenation, promoted by metal-support interfacial catalysis, play a critical role in determining the intrinsic kinetics of transfer hydrogenolysis of bio-oxygenates. However, the synergism of metal and acid-base pairs for tunable C-H, O-H and C-O cleavage and metal-H strength is under debate in this area. Herein, we present a series of bimetallic PtRu/Zn3Ce1-LDO catalysts, with abundant Lewis acid-base pairs and heterojunction structures at the metal-support interface, exhibiting enhanced performances of transfer hydrogenolysis of glycerol. The key finding is that the incorporation of ZnO unexpectedly induced the formation of large amounts of oxygen vacant sites and surface hydroxyl sites on the CeOx support, leading to abundant Lewis acid-base pairs. The strong electron coupling effect of PtRu and Lewis acid-base pairs results in weakened PtRu-H bonding, facilitating a hydrogen transfer reaction. Synergism between enhanced Lewis acid-base pairs and weaker PtRu-H hydride bonding is critical for remarkable catalytic activity (TOF: 526 h-1) and selectivity towards glycols (70.8percent), and results in one of the best performances in the current literature. Moreover, the influence of hydrogen donors, reaction temperature and time on conversion and product distribution was further investigated in detail. An alternative reaction pathway for the transfer hydrogenolysis of glycerol over the proposed acid-base pair catalysts was proposed and validated with experimental data. The outcome of this work will provide new insights into the rational design of efficient catalytic materials for energy and environmental applications.
- Chen, Xiaobo,Cheng, Yinlei,Feng, Xiang,Jin, Xin,Liu, Yibin,Yang, Chaohe,Zhang, Guangyu,Zhang, Quanxing
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p. 4386 - 4395
(2020/07/30)
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- Stanosilicates based on Sn-magadiites applied in conversion of fructose at moderate temperatures
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Sn-Magadiite stanosilicates were successfully synthesized by the hydrothermal method. They were found to be efficient in fructose conversion, particularly at 130, 150 and 170 °C. The temperature of 150 °C was ideal for the formation of retro-aldol fragmen
- Dos Santos, Tiago Gomes,Da Silva, Antonio Osimar Sousa,Plentz Meneghetti, Simoni Margareti
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p. 6111 - 6115
(2020/11/03)
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- Reduction of carbon dioxide at a plasmonically active copper-silver cathode
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Electrochemically deposited copper nanostructures were coated with silver to create a plasmonically active cathode for carbon dioxide (CO2) reduction. Illumination with 365 nm light, close to the peak plasmon resonance of silver, selectively enhanced 5 of the 14 typically observed copper CO2 reduction products while simultaneously suppressing hydrogen evolution. At low overpotentials, carbon monoxide was promoted in the light and at high overpotentials ethylene, methane, formate, and allyl alcohol were enhanced upon illumination; generally C1 products and C2/C3 products containing a double carbon bond were selectively promoted under illumination. Temperature-dependent product analysis in the dark showed that local heating is not the cause of these selectivity changes. While the exact plasmonic mechanism is still unknown, these results demonstrate the potential for enhancing CO2 reduction selectivity at copper electrodes using plasmonics.
- Corson, Elizabeth R.,Subramani, Ananya,Cooper, Jason K.,Kostecki, Robert,Urban, Jeffrey J.,McCloskey, Bryan D.
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supporting information
p. 9970 - 9973
(2020/09/23)
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- Direct Transformation of Glycerol to Propanal using Zirconium Phosphate-Supported Bimetallic Catalysts
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Selective transformation of glycerol to propanal (PA) provides a feasible route towards the sustainable synthesis of high value-added chemicals. In this work, zirconium phosphate (ZrP) was studied as support and Ru and Co as metal sites for glycerol hydrogenolysis in a continuous-flow reactor. It was found that ZrP-supported Co?O species had a moderate selectivity to PA (49.5 %) in glycerol hydrogenolysis. Notably, once Ru species were doped into CoO/ZrP, the resulting catalyst exhibited not only an outstanding catalytic performance for glycerol hydrogenolysis to PA (a selectivity of 80.2 % at full conversion), but also a high stability at least a 50 h long-term performance. The spent catalyst could be regenerated by calcining in air to remove carbonaceous deposits. Characterization indicated that the acid sites on ZrP played a very critical role in the dehydration of glycerol into acrolein (AE), that the distribution of Co was uniform, basically consistent with that of Zr, P and Ru, and that an especially close contact between Co?O and Ru species was formed on Ru/CoO/ZrP catalyst. The further activity tests and characterizations confirmed that there was a strong interaction between the dispersed Co?O species and Ru0 nanoparticles, which endowed Ru sites with high electronic density. This effect could play a role in facilitating the dissociation of H2, and thus in promoting the hydrogenation reaction. Besides, DFT calculations suggested that the Co?O species can adsorb more strongly the C=C bond of the intermediate AE on a highly coordinatively unsaturated Co (Cocus) site and thus lead to preferential hydrogenation at the C=C bond of AE to PA.
- Gong, Honghui,Zhou, Chuan,Cui, Yan,Dai, Sheng,Zhao, Xiuge,Luo, Ruihan,An, Pengfei,Li, Huan,Wang, Haifeng,Hou, Zhenshan
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p. 4954 - 4966
(2020/08/21)
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- A bifunctional catalyst based on Nb and v oxides over alumina: Oxidative cleavage of crude glycerol to green formic acid
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A bimetallic vanadium and niobium oxide catalyst using alumina as support was developed for the conversion of crude glycerol from biodiesel production into formic acid. The high dispersion of the active oxide phase combined with the presence of acid and redox active centers resulted in a high glycerol conversion (>90% for 25 h) with a good selectivity for formic acid (~55%). This process is the first example of a heterogeneous liquid-phase process for the conversion of crude glycerol to formic acid, which is an important chemical intermediate currently derived from petroleum feedstock.
- Chagas, Poliane,Figueiredo, Marcio P.,Hensen, Emiel J. M.,Oliveira, Henrique S.,Oliveira, Luiz Carlos A.,Sangiorge, Daniel L.,Siqueira, Kisla P. F.
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p. 8538 - 8544
(2020/06/19)
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- Preparation of alumina with different precipitants for the gas phase dehydration of glycerol and their characterization by thermal analysis
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Mesoporous aluminas were prepared using different precipitants at different pH of precipitation and evaluated in the gas phase dehydration of glycerol. Samples were characterized by thermal analysis techniques (TGA, NH3-TPD and TPO), specific surface area measurements, XRD and SEM. The gas phase dehydration of glycerol was performed in a fixed bed quartz tubular reactor at 773?K using a 10% glycerol aqueous solution. Thermogravimetric analysis has revealed the temperature regions of decomposition for the prepared alumina catalyst precursors. The specific surface area and the crystallinity of the samples were dependent on both the pH and the used precipitating agent. Samples precipitated with NaOH presented higher density of acid sites than the samples prepared with Na2CO3, regardless of precipitation pH. The catalytic properties of the prepared aluminas are mainly related to the specific surface area and to acidic characteristics. Conversions of glycerol above 85% were obtained for all samples. The selectivity for glycerol dehydration was strongly related to the amount and strength of acid sites. The best result for dehydration was obtained for samples prepared with NaOH and precipitated at pH = 5. These results are related to the higher specific surface area, greater amount of acid sites and the higher ratio of weak acid sites. TPO revealed the amount of carbon deposited on the catalysts. Samples that showed higher carbon formation also showed a higher production of light olefins, indicating that the formation of carbon is related to the formation of these byproducts. NH3-TPD has shown the ratio of different acid sites on the surface of alumina samples that makes possible to estimate the correlation between the acidity and the catalytic properties.
- Lima, Dirleia S.,Perez-Lopez, Oscar W.
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p. 1387 - 1398
(2020/01/28)
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- Method for preparing acetol from saccharides
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The invention discloses a method for preparing acetol from saccharides. According to the method, supported Co-Sn bimetal is used as a catalyst, water is used as a solvent, the saccharides are catalyzed to selectively prepare acetol, the catalyst is low in price, has high catalytic activity and selectivity, has good activity for various saccharides, can realize direct one-step conversion of saccharides such as cellulose to prepare acetol with high additional value, and has a good application prospect.
- -
-
Paragraph 0022-0025; 0031-0049
(2020/01/25)
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- Catalytic Dehydration of Glycerol to Acrolein over Aluminum Phosphate Catalysts
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Gas phase conversion of glycerol to acrolein over a variety of aluminum phosphate (AlP) catalysts synthesized by a simple replacement reaction method with a variation in calcination temperature (300-700 °C, AlP-300, AlP-400, AlP-500, AlP-600, and AlP-700, respectively) has been investigated. The textural properties, acidities and coke contents of the samples were also determined. The catalysts were presented in an amorphous state when the AlP sample was calcined below 500 °C. Further increasing the calcination temperature promoted the formation of orthorhombic α-AlPO4 crystal. The weak acid sites increased when the calcination temperature was raised from 300 to 500 °C. However, the weak acid sites decreased when the AlP was calcined above 500 °C. The acidity of the catalyst played a crucial role in the glycerol dehydration reaction. The maximum acrolein selectivity of 66% at 98% glycerol conversion was obtained over AlP-500 catalyst, due to the largest number of acid sites and appropriate textural properties. AlP-700 exhibited the lowest glycerol conversion, owing to the formation of orthorhombic α-AlPO4 crystalline phase and the lowest amount of acid sites under high calcination temperature. The significant reduction in the acidity of the used sample led to a decrease of glycerol conversion.
- Ding, Jianfei,Liu, Xueli,Ma, Tianlin,Yun, Zhi,Zheng, Jiandong
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p. 1597 - 1604
(2020/10/09)
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- Method for preparing monoisopropanolamine
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The invention discloses a method for preparing monoisopropanolamine. The method comprises the steps of (a) reacting 1,2-propylene glycol under the action of a dehydrogenation catalyst to obtain 2-hydroxy propionaldehyde; and (b) reacting the 2-hydroxy propionaldehyde obtained in the step (1) with liquid ammonia and hydrogen under the action of a hydrogenation catalyst to prepare monoisopropanolamine. The dehydrogenation catalyst is prepared from a modified gamma-Al2O3 carrier and active components of CuO, PdO, Bi2O3 and In2O3. The hydrogenation catalyst comprises a modified gamma-Al2O3 carrierand active components NiO, V2O5 and Y2O3. Different catalysts and two-step reaction processes are adopted, and the reaction processes of dehydrogenation, imidization and hydrogenation of 1,2-propanediol are controlled to inhibit the generation of by-products such as hydroxyacetone in the dehydrogenation process and by-products such as secondary amine in the amination process, thereby greatly enhancing the yield and selectivity of the monoisopropyl alcohol product.
- -
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Paragraph 0078; 0080-0081; 0096; 0100-0101
(2021/01/04)
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- Method for preparing hydroxyacetone by glycerol dehydration
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The invention discloses a method for preparing hydroxyacetone by glycerol dehydration. A supported Cr2Cu2O5/SAPO-11 catalyst is used, SAPO-11 is fully used as a carrier, the prepared supported nano copper chromite catalyst is high in activity and good in stability, a pure glycerol feed can be used for replacing glycerol solution feed, the conversion rate of glycerol is 97% or above, and the selectivity of the hydroxyacetone is 95% or above.
- -
-
Paragraph 0033-0051; 0054
(2019/05/02)
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- Effect of solvent nature on propylene glycol oxidation with: Tert-butyl hydroperoxide over metal-organic framework Cr-MIL-101
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The effect of solvent nature on conversion, product yields and reaction kinetics of selective propylene glycol oxidation with tert-butyl hydroperoxide over porous chromium terephthalate Cr-MIL-101 used as a heterogeneous catalyst is considered. Differences in hydrogen bonding of propylene glycol molecules in different solvents and adsorption of components of the reaction mixture on the active sites of the catalyst are studied by Fourier-transformed infrared spectroscopy. The characteristics of the solvent are shown to play a key role in the process under consideration. In the case of aprotic solvents, the oxidant utilization efficiency, the propylene glycol conversion and the product yields are significantly higher in comparison with those in protic solvents. The protic solvents can adsorb on the active sites of the catalyst which leads to a decrease of their accessibility for the reagents. The initial rate of propylene glycol oxidation decreases linearly with the increasing of the diameter of molecules of the protic solvents. DFT calculations support the competitive adsorption of the molecules of protic solvents on Cr active sites of MIL-101. In the aprotic solvents, the reactivity and distribution of propylene glycol molecules in the solution are determined by the involvement of hydroxyl groups of the substrate into the intermolecular interactions. The ability of the aprotic solvents to break the hydrogen bond network in the associates of propylene glycol is responsible for the concentration of the substrate molecules in the pores of Cr-MIL-101. The highest selectivities towards hydroxyacetone for Cr-MIL-101 catalyst are obtained in solvents, where the initial rates of propylene glycol oxidation are the lowest ones.
- Torbina, Viktoriia,Salaev, Mikhail,Vodyankina, Olga
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p. 25981 - 25986
(2019/09/13)
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- Nucleophilic Isomerization of Epoxides by Pincer-Rhodium Catalysts: Activity Increase and Mechanistic Insights
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Herein, we present the efficient isomerization of epoxides into methyl ketones with a novel pincer-rhodium complex under very mild conditions. The catalyst system has an excellent functional group tolerance and a wide array of epoxides was tested. The corresponding methyl ketones were obtained in very high yields with excellent chemo- and regioselectivity. In addition, we investigated mechanistic details like the isomerization of the catalyst, and we obtained evidence that the catalytic cycle follows a β-hydride elimination-reductive elimination pathway after the nucleophilic ring opening of the epoxide.
- Tian, Yingying,Jürgens, Eva,Mill, Katharina,Jordan, Ronja,Maulbetsch, Theo,Kunz, Doris
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p. 4028 - 4035
(2019/06/25)
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- New insights for the valorisation of glycerol over MgO catalysts in the gas-phase
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Aqueous glycerol solutions of up to 50 wt% were reacted over magnesium oxide catalysts at temperatures greater than 300 °C, the reactivity of which was compared to catalyst-free reactions. Under catalyst-free conditions, modest levels of dehydration to hydroxyacetone were observed at temperatures >400 °C in a steel reactor tube and >320 °C over silicon carbide. For reactions over MgO, the product distribution becomes more diverse, resulting in the formation of methanol, acetaldehyde, ethylene glycol, 1,2-propanediol and acetic acid. The methanol space-time-yield over MgO catalyst samples (0.5 g) was found to be highest at 400 °C (205 g h-1 kgcat-1) with a 50 wt% solution of glycerol, or with a glycerol concentration of 10 wt%; 255 g h-1 kgcat-1 over 0.1 g of catalyst. Despite the high glycerol conversion achieved, the MgO catalyst was found to be stable over 48 h, following a modest decrease in glycerol conversion during the initial 2 h of reaction. Post-reaction characterisation revealed that the level of coking at high glycerol conversions (>90%) was ≥120 mg gcat-1. The carbon mass balance determined by GC analysis for a typical reaction was 75% and so the carbon lost from catalyst coking only represents a modest quantity of the missing carbon; typically 10%. MgO was also found to promote the formation of high molecular weight products via condensation reactions, which were responsible for the remainder of the missing carbon; ca. 15%. Therefore, the total organic content of the post-reaction mixture and coke was calculated to be 94% of the starting solution. We conclude that the catalyst surface directs the formation of methanol, however, the results indicate that the reaction conditions are crucial to obtain optimum yields.
- Smith, Louise R.,Smith, Paul J.,Mugford, Karl S.,Douthwaite, Mark,Dummer, Nicholas F.,Willock, David J.,Howard, Mark,Knight, David W.,Taylor, Stuart H.,Hutchings, Graham J.
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p. 1464 - 1475
(2019/03/26)
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- Glycerin and the laevulinic acid one-step process for preparing 1, 3 - propylene glycol and γ - e lactone method
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The invention relates to a method for preparing 1,3-propylene glycol and gamma-valerolactone from glycerin and acetylpropionic acid by a one-step method. According to the method, a stainless steel high-pressure reactor with a volume of 50 ml is adopted; a catalyst used in the invention is Ru/C with its catalytic amount of 0.04g and with its composition by weight of Ru%=5%; and the rest is a carrier, namely activated carbon. A reaction material is a glycerin-acetylpropionic acid solution (concentration of acetylpropionic acid is 20 wt% and concentration ratio of acetylpropionic acid to glycerin is 1:1-10:1), and volume of the solution is 5 ml. A reaction solvent is water. Reaction temperature is 120-200 DEG C; reaction H2 pressure is 2-4 MPa; and reaction time is 0.5-12 h. In comparison with existing technologies for preparing 1,3-propylene glycol from glycerin, the invention is different in the following aspects: an acid reactant is added into the glycerin system; and by the utilization of a metal catalyst, the catalyst can cooperate with the acid reactant to selectively convert glycerin to 1,3-propylene glycol on one hand, and the acid reactant is simultaneously converted to a more valuable product on the other hand. The method provided by the invention has a wide application prospect.
- -
-
Paragraph 0019; 0020; 0038-0040
(2019/06/14)
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- Propylene glycol oxidation with hydrogen peroxide over Zr-containing metal-organic framework UiO-66
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Zirconium-based metal–organic framework UiO-66 catalyzes oxidation of propylene glycol (PG) using hydrogen peroxide as green oxidant. Hydroxyacetone (HA) is the main oxidation product, while the main side product is acetic acid (AcA). The nature of the solvent drastically affects PG adsorption, oxidant utilization efficiency and product yields. The best catalytic performance (85% selectivity towards HA at ca. 10% PG conversion) was achieved with water–acetonitrile (3/7 (v/v)) mixture as a solvent. Additives of radical chain scavengers produce a rate-inhibiting effect, suggesting radical chain mechanism of the oxidation process. The PG oxidation over UiO-66 proceeds without leaching of the active metal into solution, and the catalysis has a truly heterogeneous nature. The catalyst can be recycled without significant loss of activity and selectivity and retains its structure during at least five reuses.
- Torbina, Viktoriia V.,Nedoseykina, Nadezhda S.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Vodyankina, Olga V.
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- Highly efficient catalytic conversion of cellulose into acetol over Ni-Sn supported on nanosilica and the mechanism study
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Selective conversion of cellulose into high value-added C3 chemicals is a great challenge in biorefinery due to the complicated reaction process. In this work, 61.6% yield of acetol was obtained by one pot conversion of cellulose using Ni-Sn/SiO2 catalysts. A series of characterization methods including TEM, STEM-HAADF, EDS, AAS, XRD, XPS, H2-TPR, Py-FTIR, and CO2-TPD were carried out to explore the structure-activity relationship. The strong basicity of the catalysts was a key factor affecting the production of acetol. In addition, catalysts with the hydrothermally stable L-acid sites and no B-acid sites inhibited side reactions and ensured efficient conversion of cellulose into small molecules. Further studies showed that the formation of the Ni3Sn4 alloy significantly promoted the acetol production, and its weak hydrogenation activity inhibited further conversion of acetol. Noninteger valence tin species (Snδ+ and SnOx) were formed both in Ni3Sn4 and Sn/SiO2. These Sn species were the source of basic sites and the active sites for catalyzing cellulose to acetol. Under the synergistic catalysis of Sn/SiO2 and the Ni3Sn4 alloy, cellulose was efficiently converted into acetol. This work provides guidance for the selective conversion of cellulose into C3 products.
- Liu, Xiaohao,Liu, Xiaodong,Xu, Guangyue,Zhang, Ying,Wang, Chenguang,Lu, Qiang,Ma, Longlong
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p. 5647 - 5656
(2019/11/05)
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- Selective Conversion of Cellulose to Hydroxyacetone and 1-Hydroxy-2-Butanone with Sn–Ni Bimetallic Catalysts
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The high-value-added chemicals hydroxyacetone (HA) and 1-hydroxy-2-butanone (HB) were produced from agricultural waste over a Ni3Sn4-SnOx catalyst. The Sn–Ni intermetallic compound and SnOx acted as the active sites for HA and HB production by selectively cleaving the target C?C and C?O bonds. Approximately 70 % of the total HA and HB yield was obtained by selective hydrogenolysis of cellulose. This strategy expands the application of cellulose towards renewable production of high-value C3 and C4 keto-alcohols from cellulosic biomass.
- Wang, Haiyong,Zhu, Changhui,Liu, Qiying,Tan, Jin,Wang, Chenguang,Liang, Zheng,Ma, Longlong
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p. 2154 - 2160
(2019/03/21)
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- Well-dispersed nickel nanoparticles on the external and internal surfaces of SBA-15 for hydrocracking of pyrolyzed α-cellulose
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Catalysts comprising nickel supported on SBA-15 were prepared by wet impregnation and co-impregnation methods. Wet impregnation was performed by directly dispersing an Ni(NO3)2·6H2O aqueous solution into SBA-15, whereas in co-impregnation, ethylene glycol (EG) was added to nickel nitrate aqueous solution prior to dispersion into SBA-15. After drying and calcination, NiO/SBA-15w and NiO/SBA-15c were produced. Later, after the reduction process, Ni/SBA-15w and Ni/SBA-15c were obtained. The prepared catalysts were evaluated for the hydrocracking of pyrolyzed α-cellulose. The TEM images revealed that the catalysts prepared by wet impregnation showed inhomogeneous distribution of nickel loading, whereas catalysts prepared by co-impregnation using EG exhibited homogeneous distribution and formed no nickel aggregates. During hydrocracking of pyrolyzed α-cellulose, Ni/SBA-15c with total acidity, nickel loading, particle size, and specific surface area of 7.27 m mol g?1, 5.20 wt%, 3.17 nm, and 310.0 m2 g?1, respectively, exhibited the best catalytic performance compared to other prepared catalysts with 67.35 wt% conversion of liquid product with maximum selectivity in producing 13.09 wt% of 3-methyl-pentane. Moreover, Ni/SBA-15w with total acidity, nickel loading, particle size, and specific surface area of 10.87 m mol g?1, 8.15 wt%, 7.01 nm, and 628.0 m2 g?1, respectively, produced 69.89 wt% liquid product without hydrocarbons. Study of selectivity towards the formation of liquid hydrocarbons was carried out via double step hydrocracking using Ni/SBA-15w, and 18.55 wt% of n-hexane was produced in the liquid product.
- Trisunaryanti, Wega,Suarsih, Endah,Triyono,Falah, Iip Izul
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p. 1230 - 1237
(2019/01/23)
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- CeO2 promoting allyl alcohol synthesis from glycerol direct conversion over MoFe/CeO2 oxide catalysts: morphology and particle sizes dependent
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MoFe-N, MoFe/c–CeO2, MoFe/p1–CeO2, and MoFe/p2–CeO2 (where N, c, and p stand for non-supported, nanocube, and nanoparticle) oxide catalysts were designed for gas-glycerol direct catalytic conversion into allyl alcohol. The catalysts also were characterized by XRD, TEM, BET, H2-TPR, and NH3-TPD. Mo–Fe oxides were highly dispersed on the surface of c-CeO2 and p-CeO2 supports, different with the MoFe-N consist of crystalline Fe2(MoO4)3 and Fe2O3 crystalline phase. The support effect and special natural property of CeO2 significantly improve the allyl alcohol selectivity from gas-glycerol over MoFe/CeO2. The p-CeO2 with low particle sizes and crystalline degree was superior to high-crystalline nanocube c-CeO2 to promote its interaction with the MoFe oxide active components, and improve the surface acid site concentration and reducibility of MoFe/CeO2 as well as catalytic activity and stability for allyl alcohol synthesis from gas-glycerol without any extra hydrogen donors. Over the MoFe/p2–CeO2, the glycerol conversion reached 97.1%, and the selectivity of allyl alcohol, enthanal, propanoic acid, and acrylic acid were 23.3%, 8.6%, 12.6%, and 7.8%, respectively, yielding allyl alcohol of 22.6%.
- Lan, Hai,Zeng, Jia,Zhang, Biao,Jiang, Yi
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p. 1565 - 1580
(2018/12/13)
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- The influence of SiO2 doping on the Ni/ZrO2 supported catalyst for hydrogen production through the glycerol steam reforming reaction
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The glycerol steam reforming (GSR) reaction for H2 production was studied comparing the performance of Ni supported on ZrO2 and SiO2-ZrO2 catalysts. The surface and bulk properties were determined by ICP, BET, XRD, TPD, TPR, TPO, XPS, SEM and STEM-HAADF. It was suggested that the addition of SiO2 stabilizes the ZrO2 monoclinic structure, restricts the sintering of nickel particles and strengthens the interaction between Ni2+ species and support. It also removes the weak acidic sites and increases the amount of the strong acidic sites, whereas it decreases the amount of the basic sites. Furthermore, it influences the gaseous products’ distribution by increasing H2 yield and not favouring the transformation of CO2 in CO. Thus, a high H2/CO ratio can be achieved accompanying by negligible value for CO/CO2. From the liquid products quantitative analysis, it was suggested that acetone and acetaldehyde were the main products for the Ni/Zr catalyst, for 750 °C, whereas for the Ni/SiZr catalyst allyl alcohol was the only liquid product for the same temperature. It was also concluded that the Ni/SiZr sample seems to be more resistant to deactivation however, for both catalysts a substantial amount of carbon exists on the catalytic surface in the shape of carbon nanotubes and amorphous carbon.
- Charisiou,Papageridis,Siakavelas,Sebastian,Hinder,Baker,Polychronopoulou,Goula
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p. 206 - 219
(2018/05/08)
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- Comparative study of vapour phase glycerol dehydration over different tungstated metal phosphate acid catalysts
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Tungstated metal phosphate (WOx/MP; M = Al, Zr and Ti) solid acid catalysts were examined for vapor phase glycerol dehydration to acrolein and hydroxyacetone. The physico-chemical characteristics of the samples were explored using X-ray diffraction (XRD), N2 sorption, Fourier-transform infrared spectroscopy (FT-IR), UV-visible diffuse reflectance spectroscopy (UV-DRS), and ex situ FT-IR investigation of the adsorbed pyridine and ammonia temperature programmed desorption (NH3-TPD) analysis to gain an understanding of the impact of the structural and acidic nature of the catalysts upon changing the metal component. The catalytic activity and selectivity functionalities were interpreted in terms of the acidity and structural properties of the WOx/MP catalysts. The outcomes demonstrated that WOx/TiP was the most selective and stable catalyst during the catalytic dehydration of glycerol owing to the acceptable amount of surface acidity and the substantial number of pores available on its surface. A detailed study on WOx/TiP was also performed to understand the interaction between the tungsten and the TiP support.
- Ginjupalli, Srinivasarao,Balla, Putrakumar,Shaik, Hussain,Nekkala, Nagaraju,Ponnala, Bhanuchander,Mitta, Harishekar
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p. 16860 - 16869
(2019/11/14)
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- Diversity-Orientated Stereoselective Synthesis through Pd-Catalyzed Switchable Decarboxylative C?N/C?S Bond Formation in Allylic Surrogates
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Switchable catalytic transformation of reactants can be a powerful approach towards diversity-orientated synthesis from easily available molecular synthons. Herein, an endogenous ligand-controlled, Pd-catalyzed allylic substitution allowing for either selective C?N or C?S bond formation using vinylethylene carbonates (VECs) and N-sulfonylhydrazones as coupling partners has been developed. This versatile methodology provides a facile, divergent route for the highly chemo- and stereoselective synthesis of functional allylic sulfones or sulfonohydrazides. The newly developed protocol features wide substrate scope (nearly 80 examples), broad functional group tolerance, and potential for the late-stage functionalization of bioactive compounds. The isolation and crystallographic analysis of a catalytically competent π-allyl Pd complex suggests that the pathway leading to the allylic products proceeds through a different manifold as previously proposed for the functionalization of VECs with nucleophiles.
- Deng, Lei,Kleij, Arjan W.,Yang, Weibo
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supporting information
p. 19156 - 19161
(2018/11/30)
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- Hydrogenolysis of glycerol over silica-supported copper-nanocatalyst: Effect of precipitating-agent and copper metal-loading
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Preparation of various silica-supported copper-nanocatalysts (Cu/SiO2) by deposition precipitation and impregnation methods was demonstrated. These catalysts were prepared using urea and sodium hydroxide as the precipitating-agents. All the catalysts were systematically characterized by various analytical, spectroscopic and imaging techniques including XRD, N2 sorption analysis, N2O chemisorption, TPD, TPR, DRUV-VIS XPS and TEM. The Cu/SiO2 catalyst prepared using urea as the precipitating-agent exhibited uniform and narrow size distribution copper-nanoparticles to that prepared using sodium hydroxide as well as impregnation method. The performance of the catalyst with different metal loading is analyzed and a Cu-loading of 15 wt% was found to be optimum for the maximum yield. Thus, the catalytic activity of 15 wt% Cu/SiO2 was systematically examined for the hydrogenolysis of glycerol reaction. The influence of reaction conditions and structure activity correlation were also elucidated in this work.
- Suthagar,Shanthi,Selvam
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p. 307 - 316
(2018/04/05)
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- Pd-Catalyzed Aerobic Oxidation Reactions: Strategies to Increase Catalyst Lifetimes
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The palladium complex [(neocuproine)Pd(μ-OAc)]2[OTf]2 (1, neocuproine = 2,9-dimethyl-1,10-phenanthroline) is an effective catalyst precursor for the selective oxidation of primary and secondary alcohols, vicinal diols, polyols, and carbohydrates. Both air and benzoquinone can be used as terminal oxidants, but aerobic oxidations are accompanied by oxidative degradation of the neocuproine ligand, thus necessitating high Pd loadings. Several strategies to improve aerobic catalyst lifetimes were devised, guided by mechanistic studies of catalyst deactivation. These studies implicate a radical autoxidation mechanism initiated by H atom abstraction from the neocuproine ligand. Ligand modifications designed to retard H atom abstractions as well as the addition of sacrificial H atom donors increase catalyst lifetimes and lead to higher turnover numbers (TON) under aerobic conditions. Additional investigations revealed that the addition of benzylic hydroperoxides or styrene leads to significant increases in TON as well. Mechanistic studies suggest that benzylic hydroperoxides function as H atom donors and that styrene is effective at intercepting Pd hydrides. These strategies enabled the selective aerobic oxidation of polyols on preparative scales using as little as 0.25 mol % of Pd, a major improvement over previous work.
- Ho, Wilson C.,Chung, Kevin,Ingram, Andrew J.,Waymouth, Robert M.
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supporting information
p. 748 - 757
(2018/01/26)
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- Regio- and chemoselective rearrangement of terminal epoxides into methyl alkyl and aryl ketones
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The development of the highly active pincer-type rhodium catalyst 2 for the nucleophilic Meinwald rearrangement of functionalised terminal epoxides into methyl ketones under mild conditions is presented. An excellent regio- and chemoselectivity is obtained for the first time for aryl oxiranes.
- Tian, Yingying,Jürgens, Eva,Kunz, Doris
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supporting information
p. 11340 - 11343
(2018/10/31)
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- The Role of Metallic Copper in the Selective Hydrodeoxygenation of Glycerol to 1,2-Propanediol over Cu/ZrO2
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A series of Cu/ZrO2 catalysts with nominal CuO loadings of 5, 10, 18 and 31 wt.% was synthesized by co-precipitation, characterized and applied in the hydrodeoxygenation of glycerol under mild reaction conditions (200 °C, 25 bar H2). These catalysts were highly selective for the cleavage of C?O bonds while preserving C?C bonds leading to 95 % selectivity to 1,2-propanediol. The conversion of glycerol was observed to be linearly correlated with the specific copper surface area derived from N2O frontal chromatography. The reaction was found to occur through the dehydration of glycerol to acetol followed by its hydrogenation to 1,2-propanediol. Metallic copper was identified as the active site for both reactions suggesting the acid ZrO2 sites to be blocked by water. Reusability studies showed that the catalyst was relatively stable and the conversion decreased by only 18 % after three cycles.
- Gabrysch, Thomas,Peng, Baoxiang,Bunea, Sorin,Dyker, Gerald,Muhler, Martin
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p. 1344 - 1350
(2018/02/23)
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- Catalyst for glycerin dehydration, preparation method therefor, and acrolein preparation method using catalyst
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The present invention relates to: a catalyst for glycerin dehydration; a preparation method therefor; and an acrolein preparation method using the catalyst. According to one embodiment of the present invention, the catalyst is used in glycerin dehydration so as to exhibit high catalytic activity, a high yield and high acrolein selectivity, and has a characteristic in which carbon is not readily deposited, thereby having a long lifetime compared with that of a conventional catalyst.
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Page/Page column 10-12
(2018/09/02)
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