- Continuous transfer hydrogenation of sugars to alditols with bioderived donors over Cu-Ni-Al catalysts
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The transfer hydrogenation of sugars to alditols with biobased alcohol donors was studied over hydrotalcite-derived Cu6-xNixAl2 catalysts prepared by coprecipitation at different pH and featuring variable Cu/Ni ratios. Their evaluation, after in situ activation in pure H2 at 773 K, in the ethanol-assisted upgrading of glucose in a continuous-flow fixed-bed reactor identified the solid synthesized at pH 9-10 and with Cu/Ni=1 as the best performer. Based on textural, structural, and redox analyses, this is related to an enhanced intermetallic interaction. Upon screening alternative donors, a sorbitol yield as high as 67 % was achieved with 1,4-butanediol. The catalytic system displayed a stable behavior during 48 h on stream and proved suitable to hydrogenate also fructose, mannose, xylose, and arabinose to the corresponding polyols (yields up to 65 %), thus standing as a more sustainable and economical alternative to Ru-based catalysts for sugar reductive upgrading. Finding the right partner: Hydrotalcite-derived Cu-Ni-Al materials efficiently catalyze the continuous transfer hydrogenation of C6 and C5 sugars with biobased alcohols as hydrogen donors with yields of up to 67 %. This technology comprises a safer and cheaper alternative to direct hydrogenation over Ru catalysts.
- Scholz, David,Aellig, Christof,Mondelli, Cecilia,Pérez-Ramírez, Javier
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- Efficient Synthesis of Sugar Alcohols over a Synergistic and Sustainable Catalyst
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A series of catalysts were prepared for sugar alcohols production to overcome the deficiencies of the previous reported catalysts, such as low yield of sugar alcohols, single function, instability, and controversial role of active sites. The role of each metal and their synergistic-cooperation was discussed in detail with a combination of conditional experiments and characterizations. The results indicated that bifunctional Ni6.66Fe1Al1.55 catalyst has unique structure with superparamagnetism and excellent activity. The (111) and (200) planes of metallic Ni are the hydrogenation active phases and preferentially exposed on Ni-Al-Ox spinel. The desired arabitol or mannitol was obtained by tuning the ratio of Br?nsted and Lewis acid sites. The recycling tests indicated that the unique structure of the prepared Ni-based catalyst can suppress leaching and poisoning, which has high textural stability and activity.
- Lin, Lu,Qiu, Jiarong,Sun, Yong,Tang, Xing,Zeng, Xianhai,Zhang, Liangqing
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- Room temperature versatile conversion of biomass-derived compounds by means of supported TiO2 photocatalysts
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The selective oxidation of glucose and degradation of phenol in liquid phase were studied in the presence of supported TiO2 photocatalysts. Photocatalysts were synthesized by a modified ultrasound-assisted sol-gel method. The fact of supporting TiO2 on zeolite type Y is giving more selective photocatalyst in glucose oxidation toward glucaric acid (GUA) and gluconic acid (GA) (total selectivity approx. 68%, after 10 min illumination time and 50%H2O/50%acetonitrile solvent composition) than the unsupported TiO2 and the commercially available photocatalyst Evonik P-25. Photocatalysts worked at room temperature, atmospheric pressure and very short reaction times (up to 15 min). Additionally, these photocatalysts were investigated in the mineralization of phenol as a cellulosic industries water contaminant. It was observed that fumed silica is a better option than zeolite as titania support in phenol aqueous degradation. Ultrasound-promoted sol-gel methodology is giving promising supported TiO2 photocatalysts for water purification and solar chemicals production.
- Colmenares, Juan C.,Magdziarz, Agnieszka
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- Ruthenium nanoparticles supported on zeolite y as an efficient catalyst for selective hydrogenation of xylose to xylitol
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Zeolite Y (HYZ) supported ruthenium (Ru) nanoparticles catalysts are prepared by simple impregnation method and characterized by using different techniques such as TEM, TEM-EDX, SEM, XRD, FT-IR, surface area analysis and CO chemisorption. HYZ (different ratio of Si/Al) supported ruthenium catalysts are evaluated in hydrogenation of xylose to xylitol under green aqueous phase system. The reaction conditions are optimized by varying the stirring rate, ruthenium percent loading, xylose concentration, hydrogen partial pressure, reaction temperature and amount of catalyst to achieve the maximum conversion of xylose and selectivity to hydrogenated product xylitol. The activity of Ru/HYZ is also compared with that of conventional Ru/C catalyst at optimum reaction condition (120 C and 5.5 MPa pressure of H2 in 2 h). The reusability test of catalyst is carried out four times by recovering the catalyst from product solution.
- Mishra, Dinesh Kumar,Dabbawala, Aasif Asharaf,Hwang, Jin-Soo
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- Elucidating the effect of solid base on the hydrogenation of C5 and C6 sugars over Pt–Sn bimetallic catalyst at room temperature
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Conversion of sugars into sugar alcohols at room temperature with exceedingly high yields are achieved over Pt–Sn/γ-Al2O3 catalyst in the presence of calcined hydrotalcite. pH of the reaction mixture significantly affects the conversion and selectivity for sugar alcohols. Selection of a suitable base is the key to achieve optimum yields. Various solid bases in combination with Pt–Sn/γ-Al2O3 catalysts were evaluated for hydrogenation of sugars. Amongst all combinations, the mixture (1:1 wt/wt) of Pt–Sn/γ-Al2O3 and calcined hydrotalcite showed the best results. Hydrotalcite helps to make the pH of reaction mixture alkaline at which sugar molecules undergo ring opening. The sugar molecule in open chain form has carbonyl group which can be polarized by Sn in Pt–Sn/γ-Al2O3 and Pt facilitates the hydrogenation. In the current work, effect of both; solid base and Sn as a promoter has been studied to improve the yields of sugar alcohols from various C5 and C6 sugars at very mild reaction conditions.
- Tathod, Anup P.,Dhepe, Paresh L.
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Read Online
- Unexpected reactivity related to support effects during xylose hydrogenation over ruthenium catalysts
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Xylose is a major component of hemicelluloses. In this paper, its hydrogenation to xylitol in aqueous medium was investigated with two Ru/TiO2catalysts prepared with two commercial TiO2supports. A strong impact of the support on catalytic performance was evidenced. Ru/TiO2-R led to fast and selective conversion of xylose (100% conversion in 2 h at 120 °C with 99% selectivity) whereas Ru/TiO2-A gave a slower and much less selective transformation (58% conversion in 4 h at 120 °C with 17% selectivity) with the formation of several by-products. Detailed characterization of the catalysts with ICP, XRD, FTIR, TEM, H2chemisorption, N2porosimetry, TPR and acid-base titration was performed to elucidate the role of each support. TiO2-R has a small specific surface area with large ruthenium nanoparticles in weak interaction with the TiO2support and no acidity, whereas TiO2-A is a mesoporous material with a large specific surface area that is mildly acidic, and bears small ruthenium particles in strong interaction with the TiO2support. The former was very active and selective for xylose hydrogenation to xylitol whereas the latter was less active and poorly selective. Moreover, careful analysis of the reaction products also revealed that anatase TiO2can catalyze undesired side-reactions such as xylose isomerisation to various pentoses, and therefore the corresponding unexpected polyols (arabitol, ribitol) were produced during xylose conversion by hydrogenation. In a first kinetic approach, a simplified kinetic model was built to compare quantitatively intrinsic reaction rates of both catalysts. The kinetic constant for hydrogenation was 20 times higher for Ru/TiO2-R at 120 °C.
- Fongarland, Pascal,Freitas, Victoria D. S.,Paez, Ana,Philippe, Régis,Veyre, Laurent,Vilcocq, Léa
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p. 39387 - 39398
(2021/12/27)
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- Hydrogenolysis of sorbitol into valuable C3-C2 alcohols at low H2 pressure promoted by the heterogeneous Pd/Fe3O4 catalyst
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The hydrogenolysis of sorbitol and various C5-C3 polyols (xylitol; erythritol; 1,2- 1,4- and 2,3-butandiol; 1,2-propandiol; glycerol) have been investigated at low molecular hydrogen pressure (5 bar) by using Pd/Fe3O4, as heterogeneous catalyst and water as the reaction medium. Catalytic experiments show that the carbon chain of polyols is initially shortened through dehydrogenation/decarbonylation and dehydrogenation/retro-aldol mechanisms followed by a series of cascade reactions that include dehydrogenation/decarbonylation and dehydration/hydrogenation processes. At 240 °C, sorbitol is fully converted into lower alcohols with ethanol being the main reaction product in liquid phase.
- Gumina, Bianca,Mauriello, Francesco,Pietropaolo, Rosario,Galvagno, Signorino,Espro, Claudia
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p. 152 - 160
(2018/02/17)
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- Preparation method of gamma-acetyl n-propanol
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The invention discloses a preparation method of gamma-acetyl n-propanol. The method includes the steps of (1) adding the hydrolysate of plant fiber or xylose and other raw materials into a reaction still, adding a two-phase reactive solvent and a catalyst, inletting hydrogen, and heating the reaction still to react for several hours; (2) carrying out standing, liquid separation and then solid-liquid separation on reaction materials in the reaction still, obtaining water phase, oil phase and the catalyst, and recycling the catalyst for reutilization; (3) concentrating water phase products, extracting 1, 4-pentanediol in the oil phase, mixing with the concentrated solution, and carrying out further separation to obtain a crude product of 1, 4-pentanediol; (4) pumping the crude product of 1, 4-pentanediol obtained from the water phase and the oil phase in step (3) to a fixed bed reactor, carrying out dehydrogenation to produce gamma-acetyl n-propanol under the action of a catalytic dehydrogenation catalyst or an oxydehydrogenation catalyst. According to the preparation method, raw materials have extensive sources, the production cost is low, no inorganic acid system is used, and the reaction process is environment-friendly.
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Paragraph 0036; 0037
(2017/12/09)
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- CTAB-assisted sol-microwave method for fast synthesis of mesoporous TiO2 photocatalysts for photocatalytic conversion of glucose to value-added sugars
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Fabrication technique is an important factor for development of catalysts. Titanium dioxide (TiO2) is one of efficient photocatalysts. In this work, we firstly report the fabrication of TiO2 nanoparticles by sol-microwave method with cetyltrimethylammonium bromide (CTAB) surfactant. Absence of surfactant, microwave treatment significantly reduced the cluster sizes of TiO2, but high aggregations of TiO2 particles were observed. CTAB has great impact on morphology, cluster size and mesoporous structure of TiO2. Therefore, surface area of TiO2 synthesized by sol-microwave method with 0.108 M CTAB increased from 15.97 to 37.60 m2/g. Photocatalytic activity of TiO2 was tested via the glucose conversion to produce value-added chemicals (gluconic acid, xylitol, arabinose and formic acid). It was found that surface area, mesoporous structure and pore size of TiO2 are crucial properties for glucose conversion and product distribution. From the reaction test, 0.108 M CTAB/MW-TiO2 achieved the highest glucose conversion (62.28%).
- Payormhorm, Jiraporn,Chuangchote, Surawut,Laosiripojana, Navadol
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p. 546 - 555
(2017/09/01)
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- Selective C?O Bond Cleavage of Sugars with Hydrosilanes Catalyzed by Piers’ Borane Generated In Situ
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Described herein is the selective reduction of sugars with hydrosilanes catalyzed by using Piers’ borane [(C6F5)2BH] generated in situ. The hydrosilylative C?O bond cleavage of silyl-protected mono- and disaccharides in the presence of a (C6F5)2BH catalyst, generated in situ from (C6F5)2BOH, takes place with excellent chemo- and regioselectivities to provide a range of polyols. A study of the substituent effects of sugars on the catalytic activity and selectivity revealed that the steric environment around the anomeric carbon (C1) is crucial.
- Zhang, Jianbo,Park, Sehoon,Chang, Sukbok
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supporting information
p. 13757 - 13761
(2017/10/09)
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- Hormonemate Derivatives from Dothiora sp., an Endophytic Fungus
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A search for cytotoxic agents from cultures of the endophytic fungus Dothiora sp., isolated from the endemic plant Launaea arborescens, led to the isolation of six new compounds structurally related to hormonemate, with moderate cytotoxic activity against different cancer cell lines. By using a bioassay-guided fractionation approach, hormonemates A-D (1-4), hormonemate (5), and hormonemates E (6) and F (7) were obtained from the acetone extract of this fungus. Their structures were determined using a combination of HRMS, ESI-qTOF-MS/MS, 1D and 2D NMR experiments, and chemical degradation. The cytotoxic activities of these compounds were evaluated by microdilution colorimetric assays against human breast adenocarcinoma (MCF-7), human liver cancer cells (HepG2), and pancreatic cancer cells (MiaPaca_2). Most of the compounds displayed cytotoxic activity against this panel.
- Pérez-Bonilla, Mercedes,González-Menéndez, Víctor,Pérez-Victoria, Ignacio,De Pedro, Nuria,Martín, Jesús,Molero-Mesa, Joaquín,Casares-Porcel, Manuel,González-Tejero, María Reyes,Vicente, Francisca,Genilloud, Olga,Tormo, José R.,Reyes, Fernando
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p. 845 - 853
(2017/05/05)
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- Kinetic insight into the effect of the catalytic functions on selective conversion of cellulose to polyols on carbon-supported WO3 and Ru catalysts
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Efficient conversion of cellulose, the most abundant biomass on Earth, to chemicals in high yields remains a formidable challenge. Here, we report the marked change in the distribution of polyol products in the cellulose reaction on Ru/C and WO3/C, strongly depending on the competitive reactions of the glucose intermediate. WO3 crystallites not only promote, as a solid acid, the efficient hydrolysis of cellulose to glucose, but also catalyze the selective cleavage of the C-C bonds in glucose and other C6 sugar intermediates, leading to the formation of ethylene glycol and propylene glycol, in competition with the sugar hydrogenation to the corresponding C6 polyols (e.g. sorbitol) on Ru/C. The basic C support, behaving similar to other solid bases (i.e. MgO), catalyzes the isomerization of glucose into fructose, leading to the favored formation of propylene glycol instead of ethylene glycol. Such strong dependence of the product distribution on the catalytic functions is clarified by the kinetic analysis of the three competitive reactions of glucose, including its hydrogenation, isomerization and C-C bond cleavage. Importantly, such kinetic analysis can predict the maximum selectivity ratio of propylene glycol to ethylene glycol, which is 2.5, for example, at 478 K under the reaction conditions in this work, corresponding to a maximum yield of propylene glycol of ~71%. These understandings shed new insights into the selective conversion of cellulose, which provides guidance for the rational design of catalyst functions and tuning of reaction parameters towards the controllable synthesis of specific products from cellulose.
- Liu, Yue,Liu, Haichao
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- Production of xylitol from glucose by a recombinant strain
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The present invention relates to a recombinant microbial host for the production of xylitol, the recombinant microbial host containing a nucleic acid sequence encoding a NAD+-specific D-arabitol 4-oxidoreductase (EC 1.1.1.11) using D-arabitol as substrate and producing D-xylulose as product, and a nucleic acid sequence encoding a NADPH-specific xylitol dehydrogenase using D-xylulose as substrate and producing xylitol as product.
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Paragraph 0091-0106
(2016/01/11)
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- Arabinogalactan hydrolysis and hydrolytic hydrogenation using functionalized carbon materials
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Hydrolysis of the hemicellulose arabinogalactan was studied in this work over several functionalized carbon materials, which were specifically treated to increase their acidities. Hydrolytic hydrogenation of arabinogalactan was investigated using the same materials in a mechanical mixture with ruthenium supported on active carbon. Application of these mixtures resulted in formation of polyols, suppressing simultaneously the generation of side products hydroxymethylfurfural (HMF) and furfural. Formation of high molecular weight compounds (aggregates of sugars and humins) was still quite substantial with a mechanical mixture of Ru/C and a carbon material prepared from sucrose by activation with zinc chloride to increase porosity. Post-treatment of this carbonaceous material with sulphuric acid significantly influenced kinetics of high molecular weight products formation resulting also in elevation of sugar alcohols yields.
- Murzin, D.Yu.,Murzina,Tokarev,Shcherban,W?rn?,Salmi
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p. 169 - 176
(2015/02/19)
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- Unravelling the Ru-Catalyzed Hydrogenolysis of Biomass-Based Polyols under Neutral and Acidic Conditions
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The aqueous Ru/C-catalyzed hydrogenolysis of biomass-based polyols such as erythritol, xylitol, sorbitol, and cellobitol is studied under neutral and acidic conditions. For the first time, the complete product spectrum of C2-C6 polyols is identified and, based on a thorough analysis of the reaction mixtures, a comprehensive reaction mechanism is proposed, which consists of (de)hydrogenation, epimerization, decarbonylation, and deoxygenation reactions. The data reveal that the Ru-catalyzed deoxygenation reaction is highly selective for the cleavage of terminal hydroxyl groups. Changing from neutral to acidic conditions suppresses decarbonylation, consequently increasing the selectivity towards deoxygenation.
- Hausoul, Peter J. C.,Negahdar, Leila,Schute, Kai,Palkovits, Regina
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p. 3323 - 3330
(2015/10/19)
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- Conversion of glucose and sorbitol in the presence of Ru/C and Pt/C catalysts
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The conversion of glucose and sorbitol in the presence of Ru and Pt catalysts supported on carbon was carried out at different pressure and temperature conditions, using a batch and a semi-batch reactor. Attempts were made to improve the selectivity of glycols and alcohols (ethanol), introducing a promoter and inhibiter of the hydrogenolysis in the reactant mixture. On the basis of these results, which confirm the higher activity of Ru with respect to Pt, and the important role of an inhibitor like sulphur, the mechanism driving these reactions and the promising thermocatalytic conditions are clearer. This journal is
- Tronci, Stefania,Pittau, Barbara
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p. 23086 - 23093
(2015/06/02)
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- Direct conversion of cellulose into acetol on bimetallic Ni-SnO x/Al2O3 catalysts
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The direct conversion of cellulose into acetol was studied on SnO x-modified Ni/Al2O3 catalysts with different Sn/Ni atomic ratios in the range of 0-2.0. The selectivity to acetol strongly depended on the Sn/Ni ratios, which reached the highest value of 53.9% at the ratio of 0.5, compared at similar cellulose conversions (~20%). On Ni-SnOx/Al2O3 (Sn/Ni = 0.5), cellulose, glucose and fructose converted to acetol in high yields of approximately 35%, 53% and 73%, respectively, at 210 °C and 6 MPa H2. The effects of the Sn/Ni ratios on the acetol selectivity appear to be related to their effects on the hydrogenation activity of the Ni-SnOx/Al2O3 catalysts that decreased with increase of the Sn/Ni ratios, and to the relative rate between the hydrogenation of C6 sugar intermediates (e.g. glucose and fructose) and their degradation intermediates (e.g. glyceraldeyde and dihydroxyacetone) involved in the cellulose reaction on the Ni particles and the isomerization of glucose to fructose and their CC bond cleavage by retro-aldol condensation on the SnOx domains. Comparison of SnO x with CeOx, ZnOx and AlOx supported on Al2O3 with different basicity suggested that the larger concentration of stronger basic sites on SnOx facilitated the isomerizaiton of glucose to fructose and its subsequent CC bond cleavage. These results and their understanding provide guidance for improving the acetol production from cellulose by tuning the catalytic functions required for the involved reactions of hydrogenation on the metal surfaces, and isomerization and CC bond cleavage on the basic sites.
- Deng, Tianyin,Liu, Haichao
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- Conversion of sugars to ethylene glycol with nickel tungsten carbide in a fed-batch reactor: High productivity and reaction network elucidation
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Bifunctional nickel tungsten carbide catalysis was used for the conversion of aqueous sugar solutions into short-chain polyols such as ethylene glycol. It is shown that very concentrated sugar solutions, viz. up to 0.2 kg L -1, can be converted without loss of ethylene glycol selectivity by gradually feeding the sugar solution. Detailed investigation of the reaction network shows that, under the applied reaction conditions, glucose is converted via a retro-aldol reaction into glycol aldehyde, which is further transformed into ethylene glycol by hydrogenation. The main byproducts are sorbitol, erythritol, glycerol and 1,2-propanediol. They are formed through a series of unwanted side reactions including hydrogenation, isomerisation, hydrogenolysis and dehydration. Hydrogenolysis of sorbitol is only a minor source of ethylene glycol. To assess the relevance of the fed-batch system in biomass conversions, both the influence of the catalyst composition and the reactor setup parameters like temperature, pressure and glucose addition rate were optimized, culminating in ethylene glycol yields up to 66% and separately, volume productivities of nearly 300 gEG L-1 h-1.
- Ooms, Roselinde,Dusselier, Michiel,Geboers, Jan A.,Op De Beeck, Beau,Verhaeven, Rick,Gobechiya, Elena,Martens, Johan A.,Redl, Andreas,Sels, Bert F.
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p. 695 - 707
(2014/02/14)
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- Selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol on Ni/C and basic oxide-promoted Ni/C catalysts
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The selective hydrogenolysis of xylitol to ethylene glycol and propylene glycol was examined on Ni/C catalysts in the presence of solid bases, e.g. Ca(OH)2 and CeO2, physically mixed with or co-supported with Ni on C. Compared with Ru/C, the Ni/C catalysts were more selective to the two target glycols under identical conditions, apparently as a result of their lower hydrogenation activity and consequently favored the CC cleavage of xylose intermediate by the base catalyst over its competitive hydrogenation on the Ni particles. Noticeably, the presence of the solid bases rendered the Ni particles resistant to leaching and sintering, and thus stable in the xylitol hydrogenolysis. Supporting the solid bases, especially CeO2 and CaO, with the Ni particles on C led not only to a reduction in the amount of solid bases required, but also efficient formation of the two glycols with negligible lactic acid. For instance, on Ni-CaO/C (at a CaO/Ni molar ratio of 0.66), the combined selectivity to ethylene glycol and propylene glycol, together with glycerol, reached 69.5% at nearly 100% xylitol conversion at 473 K, 4.0 MPa H2. These features of the basic oxide-promoted Ni catalysts show their promising advantages over the noble Ru catalysts, upon optimization of their compositions and structures, and the reaction parameters, for the efficient hydrogenolysis of xylitol and other lignocellulose-derived polyols to produce the two target glycols.
- Sun, Jiying,Liu, Haichao
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- Aqueous-phase hydrogenation and hydrodeoxygenation of biomass-derived oxygenates with bimetallic catalysts
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The reaction rate on a per site basis for aqueous-phase hydrogenation (APH) of propanal, xylose, and furfural was measured over various alumina-supported bimetallic catalysts (Pd-Ni, Pd-Co, Pd-Fe, Ru-Ni, Ru-Co, Ru-Fe, Pt-Ni, Pt-Co, and Pt-Fe) using a high-throughput reactor (HTR). The results in this paper demonstrate that the activity of bimetallic catalysts for hydrogenation of a carbonyl group can be 110 times higher than monometallic catalysts. The addition of Fe to a Pd catalyst increased the activity for hydrogenation of propanal, xylose, and furfural. The Pd1Fe3 catalyst had the highest reaction rate for APH of propanal among all catalysts tested in the HTR. The addition of Fe to the Pd catalyst increased the reaction rate for xylose hydrogenation by a factor of 51, compared to the monometallic Pd catalyst. However, no bimetallic catalyst tested in this study was more active than the monometallic Ru catalyst for hydrogenation of xylose. The Pd1Fe 3 catalyst had the highest reaction rate for APH of furfural, which was 9 times higher than the rate of the Pd catalyst. The Pd1Fe 3/Zr-P, a bimetallic bifunctional catalyst, was 14 times more active on a per site basis than a Pd/Zr-P catalyst for aqueous-phase hydrodeoxygenation (HDO) of sorbitol in a continuous flow reactor. The addition of Fe to the Pd catalyst increased the rate of C-C cleavage reactions and promoted the conversion of sorbitan and isosorbide in HDO of sorbitol. Pd1Fe 3/Zr-P also had a higher yield of gasoline-range products than the Pd/Zr-P catalyst.
- Lee, Jechan,Kim, Yong Tae,Huber, George W.
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supporting information
p. 708 - 718
(2014/02/14)
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- Towards efficient synthesis of sugar alcohols from mono- and poly-saccharides: Role of metals, supports & promoters
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Biomass derived sugar alcohols (xylitol, arabitol) find numerous uses in the food, oral hygiene and pharmaceutical industries. Their direct synthesis from poly-saccharides, however, still remains an immense challenge. In this study, we demonstrate in detail the effects of metals, supports and promoters in enhancing the yields of sugar alcohols from mono- and poly-saccharides. We undertook synthesis of bimetallic catalysts, M-M′/S (M, metal = Pt, Ru; M′, promoter = Sn, Ga, Fe; S, support = γ-Al2O3 (AL), SiO2-Al2O3 (SA), carbon (C)) with varying metal loadings (Pt/Ru = 2, 3.5 wt%; Sn = 0.22, 0.43, 0.87, 1.5, 3.5 wt%; Ga/Fe = 0.25 wt%) by a co-impregnation method. The catalytic activities of these catalysts were evaluated in the synthesis of sugar alcohols from xylose (mono-saccharide) and hemicellulose (xylan, poly-saccharide) at 130-190 °C. Among all of the bimetallic catalysts, the Pt(3.5)Sn(0.43)/AL catalyst (50%) showed 2.8 times improvement in the yield of sugar alcohols compared to a monometallic Pt(3.5)/AL catalyst (18%). Similarly, in the xylose reaction a 2.4 times enhancement in the yield of sugar alcohols over Pt(3.5)Sn(0.43)/AL (79%) was observed compared to the 33% yield obtained with Pt(3.5)/AL. By conducting several experiments it is confirmed that the residual Cl-, which remained on the catalyst even after calcinations and reductions carried out at 400 °C, does not play any role in catalysis. The stability of the Pt(3.5)Sn(0.43)/AL catalyst confirmed by XRD and ICP analysis was responsible for achieving reproducible activity in at least 5 consecutive runs. Formation of electron deficient Sn confirmed by XPS analysis helped to polarize the carbonyl group, which in turn enhanced the sugar alcohols' yields. Formation of PtSn and Pt3Sn species was observed when Sn loading was more than 0.87%.
- Tathod, Anup P.,Dhepe, Paresh L.
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p. 4944 - 4954
(2015/01/08)
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- Solid base supported metal catalysts for the oxidation and hydrogenation of sugars
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Pt impregnated on γ-Al2O3 (acidic support) and hydrotalcite (basic support) catalysts were synthesized, characterized and used in the oxidation and hydrogenation reactions of C5 and C6 sugars. In the absence of homogeneous base, 83% yield for gluconic acid; an oxidation product of glucose can be achieved over Pt/hydrotalcite (HT) catalyst at 50 °C under atmospheric oxygen pressure. Similarly, 57% yield for xylonic acid, an oxidation product of xylose is also possible over Pt/HT catalyst. Hydrogenation of glucose conducted using Pt/γ-Al2O3 + HT catalytic system showed 68% sugar alcohols (sorbitol + mannitol) formation. The 82% yield for C5 sugar alcohols (xylitol + arabitol) was obtained by subjecting xylose to hydrogenation over Pt/γ-Al2O3 + HT at 60 °C. UV analysis helped to establish the fact that under alkaline conditions sugars prefer to remain in open chain form in the solution and thus exposes CHO group which further undergoes oxidation and hydrogenation reactions to yield acids and alcohols.
- Tathod, Anup,Kane, Tanushree,Sanil,Dhepe, Paresh L.
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- Xylans are a valuable alternative resource: Production of d-xylose, d-lyxose and furfural under microwave irradiation
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The influence of microwave irradiation on hydrolysis of xylan and simultaneous epimerization of the d-xylose to d-lyxose has been studied. An acidic solution of xylan was treated with catalytic amount of sodium molybdate and the composition of the reaction mixture was analyzed. Short reaction times of hydrolysis and subsequent epimerization reaction provided an equilibrium reaction mixture of d-xylose and d-lyxose (1.6:1) without significant formation of undesirable side products. Obtained pentoses can be reduced to the corresponding alditols (d-xylitol and d-lyxitol) in very good yields (88% and 85%) or can be further dehydrated to furfural (53%). Combined use of Mo(VI) catalyst and microwave irradiation allows better conversions and substantial reduction of reaction times (400-fold) compared to that obtained by conventional heating. Studied stereospecific transformation of xylan proceeds with high selectivity, short reaction times and very good yields that makes this approach attractive also for preparative purposes.
- Hricovíniová, Zuzana
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p. 1416 - 1421
(2013/10/08)
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- Promoting effect of SnOx on selective conversion of cellulose to polyols over bimetallic Pt-SnOx/Al2O3 catalysts
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Cellulose is the most abundant source of biomass in nature, and its selective conversion into polyols provides a viable route towards the sustainable synthesis of fuels and chemicals. Here, we report the marked change in the distribution of polyols in the cellulose reaction with the Sn/Pt atomic ratios in a wide range of 0.1-3.8 on the SnOx-modified Pt/Al 2O3 catalysts. Such a change was found to be closely related to the effects of the Sn/Pt ratios on the activity for the hydrogenation of glucose and other C6 sugar intermediates involved in the cellulose reaction as well as to the notable activity of the segregated SnO x species for the selective degradation of the sugar intermediates on the Pt-SnOx/Al2O3 catalysts. At lower Sn/Pt ratios of 0.1-1.0, there existed electron transfer from the SnOx species to the Pt sites and strong interaction between the catalysts, as characterized by temperature-programmed reduction in H2 and infrared spectroscopy for CO adsorption, which led to their superior hydrogenation activity (per exposed Pt atom), and in-parallel higher selectivity to hexitols (e.g. sorbitol) in the cellulose reaction, as compared to Pt/Al 2O3. The hexitol selectivity reached the greatest value of 82.7% at the Sn/Pt ratio of 0.5, nearly two times that of Pt/Al 2O3 at similar cellulose conversions (~20%). As the Sn/Pt ratios exceeded 1.5, the Pt-SnOx/Al2O3 catalysts exhibited inferior hydrogenation activity (per exposed Pt atom), due to the formation of the crystalline Pt-Sn alloy, which led to the preferential conversion of cellulose to C2 and especially C3 products (e.g. acetol) over hexitols, most likely involving the isomerization of glucose to fructose and retro-aldol condensation of these sugars on the segregated SnOx species, apparently in the form of Sn(OH)2. These findings clearly demonstrate the feasibility for rational control of the cellulose conversion into the target polyols (e.g. acetol or propylene glycol), for example, by the design of efficient catalysts based on the catalytic functions of the SnOx species with tunable hydrogenation activity.
- Deng, Tianyin,Liu, Haichao
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p. 116 - 124
(2013/02/26)
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- Substrate binding to Candida tenuis xylose reductase during catalysis
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Candida tenuis xylose reductase (CtXR) is studied by in situ NMR, saturation transfer difference (STD) NMR, and molecular docking with respect to its substrate and coenzyme binding in ternary complexes. The natural substrate Xyl as well as Glc and methyl-glucosides preferentially bind as α-anomers of the pyranose forms. These α-anomers are transformed faster, predominately leading to STD effects in the formed products, and can be better docked into the CtXR active site than the β-anomer. The reduction is initiated by α-Xylp ring opening prior to hydride transfer from NADH. Binding and transformation of unnatural 2,4-dichloroacetophenone is not as good, although it is reduced with very high catalytic efficiency. STD NMR indicates a reasonable amount to leave the ternary complex in unreduced form. The molecular docking calculation confirms this result, as only a couple of the investigated ternary complexes allow reduction of the substrates.
- Vogl, Michael,Brecker, Lothar
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p. 25997 - 26004
(2013/12/04)
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- Probing the ruthenium-catalyzed higher polyol hydrogenolysis reaction through the use of stereoisomers
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Nine polyol stereoisomers ranging from three to six carbons in length were reacted under hydrogenolysis conditions (205-240°C, 100 bar H2) over a Ru-C catalyst to better understand the reaction mechanism. Previous reports have postulated the retro-aldol mechanism as the main pathway leading to C-C scission. However, the retro-aldol mechanism was insufficient in explaining the product distribution of tetritols from pentitols, while the decarbonylation mechanism could explain the selectivity results of terminal C-C scission. Retro-aldol scission of internal C-C bonds was confirmed to occur by the tetritol product distribution from hexitols. Therefore, the presence or role of 3-keto and 4-keto intermediates had a negligible effect on the C-C hydrogenolysis of polyols when compared to aldehyde intermediates. The reaction rates of the polyols depended on the configuration of the polyol stereoisomers. The reactivity of the stereoisomers was correlated to the presence of erythro sequences of hydroxyl groups and was independent of the carbon chain length. The Royal Society of Chemistry.
- Deutsch, Keenan L.,Lahr, Daniel G.,Shanks, Brent H.
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p. 1635 - 1642
(2013/02/23)
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- Two new aromatic compounds and a new D-arabinitol ester from the mushroom Hericium erinaceum
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Two new aromatic compounds (1, 2), new d-arabinitol ester (3), and two known compounds (4, 5) were isolated from mushroom Hericium erinaceum. The structures of 1-5 were elucidated on the basis of spectral data. Compounds 1, 2, 4, and 5 exhibited α-glucosidasae inhibitory activity.
- Miyazawa, Mitsuo,Takahashi, Toshiyuki,Horibe, Isao,Ishikawa, Ryuuzou
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experimental part
p. 2007 - 2010
(2012/03/26)
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- Extraction, purification, characterization and hypoglycemic activity of a polysaccharide isolated from the root of Ophiopogon japonicus
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In this research, a water-soluble polysaccharide (OJP1) extracted with hot water from the roots of Ophiopogon japonicus which is a traditional Chinese medicinal herb was precipitated with 95% ethanol and purified by DEAE-52 cellulose anion-exchange and Sephadex G-100 gel filtration chromatography. The high performance gel permeation chromatography (HPGPC) analysis showed that the average molecular weight (Mw) of OJP1 was 35.2 kDa. Monosaccharides analysis revealed that the OJP1 is composed of Ara, Glc, Gal with a relative molar ratio of 1:16:8. Pharmaceutical experiments showed OJP1 can significantly reduce blood glucose level, increase the insulin level and remediating destruction of pancreatic islets in STZ-induced diabetic rats compared with the diabetic control group. The study shows that OJP1 has an anti-diabetic effect on STZ-induced diabetic rats, and has potential use as an anti-diabetic agent. Copyright
- Chen, Xiaoming,Jin, Jing,Tang, Jia,Wang, Zhongfu,Wang, Junjun,Jin, Liqin,Lu, Jianxin
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experimental part
p. 749 - 754
(2011/06/27)
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- Selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol on supported Ru catalysts
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The selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol was carried out on different catalysts in the presence of Ca(OH)2. The catalysts included Ru supported on activated carbon (C) and, for comparison, on metal oxides, Al2O3, TiO 2, ZrO2 and Mg2AlOx as well as C-supported other noble metals, Rh, Pd and Pt, with similar particle sizes (1.6-2.0 nm). The kinetic effects of H2 pressures (0-10 MPa), temperatures (433-513 K) and solid bases including Ca(OH)2, Mg(OH)2 and CaCO3 were examined on Ru/C. Ru/C exhibited superior activities and glycol selectivities than Ru on TiO2, ZrO2, Al2O3 and Mg2AlOx, and Pt was found to be the most active metal. Such effects of the metals and supports are attributed apparently to their different dehydrogenation/ hydrogenation activities and surface acid-basicities, which consequently influenced the xylitol reaction pathways. The large dependencies of the activities and selectivities on the H2 pressures, reaction temperatures, and pH values showed their effects on the relative rates for the hydrogenation and base-catalyzed reactions involved in xylitol hydrogenolysis, reflecting the bifunctional nature of the xylitol reaction pathways. These results led to the proposition that xylitol hydrogenolysis to ethylene glycol and propylene glycol apparently involves kinetically relevant dehydrogenation of xylitol to xylose on the metal surfaces, and subsequent base-catalyzed retro-aldol condensation of xylose to form glycolaldehyde and glyceraldehyde, followed by direct glycolaldehyde hydrogenation to ethylene glycol and by sequential glyceraldehyde dehydration and hydrogenation to propylene glycol. Clearly, the relative rates between the hydrogenation of the aldehyde intermediates and their competitive reactions with the bases dictate the selectivities to the two glycols. This study provides directions towards efficient synthesis of the two glycols from not only xylitol, but also other lignocellulose-derived polyols, which can be achieved, for example, by optimizing the reaction parameters, as already shown by the observed effects of the catalysts, pH values, and H2 pressures.
- Sun, Jiying,Liu, Haichao
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experimental part
p. 135 - 142
(2011/04/15)
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- Heteropoly acids as efficient acid catalysts in the one-step conversion of cellulose to sugar alcohols
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Cellulose and even spruce can be converted efficiently into valuable platform chemicals via combined hydrolysis and hydrogenation in the aqueous phase. Thereby, heteropoly acids together with supported ruthenium catalysts show not only high activity but also remarkable selectivity to sugar alcohols reaching up to 81% yield of C4 to C6 sugar alcohols in only 7 h at 160 °C.
- Palkovits, Regina,Tajvidi, Kameh,Ruppert, Agnieszka M.,Procelewska, Joanna
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supporting information; experimental part
p. 576 - 578
(2011/03/17)
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- Hydrogenolysis of cellulose combining mineral acids and hydrogenation catalysts
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A catalytic system capable of reaching high performance in the hydrogenolysis of cellulose at low reaction temperature and short reaction times has been developed. Therefore, supported noble metal catalysts based on Pt, Pd and Ru have been combined with dilute mineral acids. A broad variable set in terms of type of noble metal, type of acid, acid concentration and reaction time could be evaluated based on chemical interpretation and supported by a Design of Experiment (DoE) approach. The variables significantly influenced conversion of cellulose, product range and selectivity towards sugar alcohol formation. Thus, at 160 °C, above 60% yield in sugars and sugar alcohols with 84% selectivity at a cellulose conversion of 72% could be reached. Besides, glycerol, propylene glycol, ethylene glycol and methanol were formed as additional valuable by-products leading to an overall carbon utilization above 89%. Furthermore, the concept was successfully transferred to real feedstocks in the form of spruce reaching close to 60% conversion in only one hour reaction time.
- Palkovits, Regina,Tajvidi, Kameh,Procelewska, Joanna,Rinaldi, Roberto,Ruppert, Agnieszka
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scheme or table
p. 972 - 978
(2010/08/19)
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- Rhodium-catalyzed decarbonylation of aldoses
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(Chemical Equation Presented) A catalytic procedure is described for decarbonylation of unprotected aldoses to afford alditols with one less carbon atom. The reaction is performed with the rhodium complex Rh(dppp)2Cl in a refluxing diglyme-DMA solution. A slightly improved catalyst turnover is observed when a catalytic amount of pyridine is added. Under these conditions most hexoses and pentoses undergo decarbonylation into the corresponding pentitols and tetrols in isolated yields around 70%. The reaction has been applied as the key transformation in a five-step synthesis of L-threose from D-glucose.
- Monrad, Rune Nygaard,Madsen, Robert
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p. 9782 - 9785
(2008/03/17)
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- Thioketals and thioethers for inhibiting the expression of VCAM-1
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Thioketals and thioethers are provided that inhibit the expression of VCAM-1, and which can be used in the treatment of VCAM-1 mediated diseases including inflammatory disorders, cardiovascular diseases, occular diseases, autoimmune diseases, neurological disorders, and cancer. The compounds also can be used to treat hyperlipidemia and/or hypercholesterolemia.
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- METHOD FOR PREPARING SUGAR ALCOHOLS BY CATALYTIC HYDROGENATION OF SUGARS
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Disclosed a method of producing sugar alcohols through the hydrogenation of sugars using a catalyst in which ruthenium is supported on a carrier comprising silica, zirconia, or a mixture thereof. The method includes hydrogenating sugar under relatively moderate reaction conditions using a catalyst in which ruthenium is supported on a carrier including silica, zirconia, or a mixture thereof, with the metal dispersion of 10% or more, and in which the chlorine content is less than 100ppm. Sugar alcohol is produced through a continuous process under moderate conditions of low temperature and pressure at a high yield, thereby generating few by products or wastes and producing sugar alcohol without a complicated separation process.
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Page/Page column 13-14
(2008/06/13)
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- Prebiotic carbohydrate synthesis: Zinc-proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
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Zn-proline catalyzed aldolisation of glycoladehyde gave mainly tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose. The Royal Society of Chemistry 2005.
- Kofoed, Jacob,Reymond, Jean-Louis,Darbre, Tamis
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p. 1850 - 1855
(2007/10/03)
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- Multiple Forms of Xylose Reductase in Candida intermedia: Comparison of Their Functional Properties Using Quantitative Structure-Activity Relationships, Steady-State Kinetic Analysis, and pH Studies
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The xylose-fermenting yeast Candida intermedia produces two isoforms of xylose reductase: one is NADPH-dependent (monospecific xylose reductase; msXR), and another is shown here to prefer NADH ≈4-fold over NADPH (dual specific xylose reductase; dsXR). To compare the functional properties of the isozymes, a steady-state kinetic analysis for the reaction D-xylose + NAD(P)H + H + ? xylitol + NAD(P)+ was carried out and specificity constants (kcat/Kaldehyde) were measured for the reduction of a series of aldehydes differing in side-chain size as well as hydrogen-bonding capabilities with the substrate binding pocket of the enzyme. dsXR binds NAD(P)+ (KiNAD+ = 70 μM; KiNADP+ = 55 μM) weakly and NADH (Ki = 8 μM) about as tightly as NADPH (Ki = 14 μM). msXR shows uniform binding of NADPH and NADP + (KiNADP+ ≈ KiNADPH = 20 μM). A quantitative structure-activity relationship analysis was carried out by correlating logarithmic kcat/Kaldehyde values for dsXR with corresponding logarithmic kcat/Kaldehyde values for msXR. This correlation is linear with a slope of ≈1 (r2 = 0.912), indicating that no isozyme-related pattern of substrate specificity prevails and aldehyde-binding modes are identical in both XR forms. Binary complexes of dsXR-NADH and msXR-NADPH show the same macroscopic pK of ≈9.0-9.5, above which the activity is lost in both enzymes. A lower pK of 7.4 is seen for dsXR-NADPH. Specificity for NADH and greater binding affinity for NAD(P)H than NAD(P)+ are thus the main features of enzymic function that distinguish dsXR from msXR.
- Nidetzky, Bernd,Brueggler, Kaspar,Kratzer, Regina,Mayr, Peter
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p. 7930 - 7935
(2007/10/03)
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- Catalytic hydrogenation of arabinonic acid and lactones to arabitol
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Aqueous solutions (20 wt%) of arabinonic acid in equilibrium with arabinonolactones were hydrogenated on ruthenium catalysts at 100°C or lower temperatures in a batch reactor. The highest selectivity to arabitol was 98.9% at 98% conversion, with a reaction rate of 73 mmol h-1 gRu-1 at 80°C. Reaction modeling was achieved by a detailed kinetic analysis of reaction data under various reaction conditions. The conversion of substrate follows a rate equation established with the Horiuti-Polanyi mechanism. The selectivity was higher on small particles supported on carbon supports because of an electron-donating effect of the support on the ruthenium particles, which decreases the rate of dehydroxylation reactions leading to unwanted deoxy products. The most important factor enhancing the selectivity was the presence of anthraquinone-2-sulfonate (A2S), which decreased the formation of deoxy products. With an optimum amount of A2S the selectivity at 100°C was improved from 93.6 to 96.7%. The molecule acted as a permanent surface modifier since the catalyst was recycled with the same selectivity without further addition of A2S. The molecule could act as an electron-donating surface ligand decreasing the rate of dehydroxylation reactions.
- Fabre, Lionel,Gallezot, Pierre,Perrard, Alain
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p. 247 - 254
(2007/10/03)
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- Reaction of sugar allyltins with aldehydes. A remarkable difference in reactivity between furanose and pyranose organometallic derivatives
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The reaction of organometallic derivatives of monosaccharides with aldehydes catalyzed with BF3·OEt2 was studied. A significant difference in reactivity between the pyranosidic and furanosidic and allyltins was noted. The former reacted readily with aldehydes affording precursors of higher carbon sugars with very high stereoselectivity, while the latter underwent rearrangement with elimination of the stannyl moiety prior to reaction with the aldehyde.
- Jarosz, Slawomir,Skora, Stanislaw,Szewczyk, Katarzyna,Ciunik, Zbigniew
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p. 1895 - 1905
(2007/10/03)
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- Production of xylitol
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A method for producing xylitol from D-glucose, D-fructose, D-galactose or mixtures thereof, characterized in that it comprises the steps of: a. oxidation of the starting material to an intermediate that consists mainly of L-xylonic acid, D-arabinonic acid, D-lyxonic acid or a mixture of at least two of said acids, whereby said acids are free or in the form of their salts, lactones or O-formyl derivatives; b. treatment of said intermediate with a hydrogenation catalyst and hydrogen gas in one or several steps to a product consisting mainly of xylitol or a mixture of xylitol, arabinitol and ribitol; c. and, if necessary, separation of xylitol from said product and, if said product consist mainly of said mixture of pentitols, feeding of the fractions of arabinitol and ribitol back to the preceding reaction step b.
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- Stereospecific carbon-carbon bond formation using rabbit muscle aldolase
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Approaches to the enantiospecific syntheses of shikimic acid and immunoactivator FR 900483 utilising Rabbit Muscle Aldolase condensations have been described.
- Sawden, J,Turner, N J
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- Continuous catalytic oxidation of alditols to aldoses
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A process is presented for the continuous oxidation of alditols to aldoses accompanied by under 20 weight percent of aldonic and/or alduronic acids relative to the aldoses that are formed. The use of zerovalent platinum on a support such as theta-alumina and at superatmospheric oxygen partial pressures up to about 1,000 pounds per square inch is partially successful in affording good conversion of alditols with relatively low aldonic and/or alduronic acid formation.
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- Process for manufacturing xylitol and xylitol-rich products
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Process for manufacturing xylitol and xylitol-rich products, characterized in that it consists of: enzymatically isomerizing at M1 D-xylulose syrup into syrup containing D-xylose and D-xylulose then, without extracting the xylose, catalytically hydrogenating this syrup at M2, resulting thus in a xylitol-rich syrup, said xylitol-rich syrup being either dehydrated, or subjected to chromatographic processing or to a treatment of extraction by crystallization at M3.
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- Synthesis of D-erythro-2-pentulose and D-threo-2-pentulose and analysis of the 13C- and 1H-n.m.r. spectra of the 1-13C- and 2-13C-substituted sugars.
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The pentuloses D-erythro-2-pentulose (1) and D-threo-2-pentulose (2) and their 1-13C- and 2-13C-substituted derivatives were prepared by hydrogenating the corresponding isotopically normal and 13C-substituted D-pentos-2-uloses with a Pd-carbon catalyst. The threo isomer and its labeled derivatives were alternatively prepared from isotopically normal and 13C-substituted D-xyloses with immobilized D-xylose (D-glucose) isomerase (E.C.5.3.1.5). The equilibrium compositions of 1 and 2 (furanose anomers and acyclic keto forms) in 2H2O were determined from 13C-n.m.r. spectra (75 MHz) of the 2-13C-labeled derivatives. The conformational properties of the cyclic and acyclic forms in 2H2O were assessed with the use of 1H-1H, 13C-1H, and 13C-13C spin-coupling constants obtained from 1H-n.m.r. (620 MHz) and 13C-n.m.r. (75 MHz) spectra. Compared with the structurally related aldotetrofuranoses the 2-pentulofuranoses more strongly prefer conformations in which the anomeric hydroxyl group is oriented quasi-axially. The strongly dipolarized carbonyl group in the acyclic keto forms of 1 and 2 appears to stabilize chain conformations having O-1 and O-3 eclipsed with the carbonyl oxygen.
- Vuorinen,Serianni
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- (1-13C)alditols: elimination of magnetic equivalence in 1H- and 13C-n.m.r. spectra of symmetric compounds through (13C)-substitution.
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(1-13C)Glycerol, D-(1-13C)arabinitol, D-(1-13C)ribitol, D-(1-13C)xylitol, D-(1-13C)glucitol, D-(1-13C)mannitol, and D-(1-13C)talitol have been prepared by NaBH4 reduction of the corresponding (1-13C)aldoses. A comparison of the 1H- (300 and 620 MHz) and 13C (75 MHz) n.m.r. spectra of natural and (1-13C)-substituted dissymmetric alditols has permitted the unequivocal assignments of their hydroxymethyl proton and carbon signals and the measurement of several 13C-1H and 13C-13C spin-coupling constants. Similar spectra of (1-13C)-substituted symmetric alditols, however, are more difficult to interpret since they are composed of overlapping 13C-coupled and 13C-noncoupled subspectra. In some cases, 1H difference spectra and 1H-coupled 13C spectra may be used to extract the 13C-1H and 13C-13C spin couplings from the 13C-coupled component. These couplings have been examined in light of conformational models previously proposed, permitting a preliminary evaluation of standard 3JCH and 3JCC values for specific coupling pathways in these compounds.
- Garrett,Serianni
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- Metal-mediated decarbonylation and dehydration of ketose sugars
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Ketose sugars can be decarbonylated and/or dehydrated by the action of certain metal complexes. Fructose reacts with 1 equiv of RhCl(PPh3)3 (1) in N-methyl-2-pyrrolidinone (NMP) at 130°C to give furfuryl alcohol, Rh(CO)Cl(PPh3)2 (2), and a small amount of 1-deoxyerythritol. 1,3-Dihydroxyacetone consumes 2 equiv of 1, giving methane and ca. 2 mol of 2. With manno-2-heptulose the primary product is 2,7-anhydromanno-2-heptulopyranose. The mechanisms of these unusual reactions have been studied by using 13C-labeling experiments and model reactions employing Pd(II) and HCl. Attempts to make the reactions catalytic using [Rh(Ph2PCH2CH2CH2PPh 2)2]+[BF4]- in place of 1 were not successful. The use of NMP as a solvent offers some advantages in the acid-catalyzed synthesis of certain carbohydrate dehydration products, as exemplified by the conversion of manno-2-heptulose to its 2,7-anhydride and of 2-deoxyglucose to 1-(2-furanyl)-1,2-ethanediol.
- Andrews, Mark A.
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p. 2703 - 2708
(2008/10/08)
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- Decarbonylation of Unprotected Aldose Sugars by Chlorotris(triphenylphosphine)rhodium(I). A New Descent of Series Approach to Alditols, Deoxyalditols, and Glycosylalditols
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Unprotected Cn aldose sugars are cleanly decarbonylated by 1 equiv of chlorotris(triphenylphosphine)rhodium(I) in 1-24 h at 130 deg C in N-methyl-2-pyrrolidinone solution to give the corresponding Cn-1 alditol in about 75-95percent yields.This technique represents a useful variation on traditional carbohydrate "descent of series" reactions.The procedure is quite general and also works on a number of aldose derivatives, such as deoxy sugars, N-acetylated amino sugars, and disaccharides, providing convenient small-scale syntheses of deoxyalditols, (acetylamino)deoxyalditols, and glycosylalditols, respectively.The reactions proceed with complete retention of stereochemistry, the only side products observed being a few percent of the Cn lactones and the Cn-2 alditol.Attempts to make the reactions catalytic have not yet been very successful.
- Andrews, Mark A.,Gould, George L.,Klaeren, Stephen A.
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p. 5257 - 5264
(2007/10/02)
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- Intermediates for preparing optically active carboxylic acids
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A process is described for preparing optically active alpha-arylalkanoic acids consisting of rearranging an optically active ketal of formula STR1 in which the substituents have the meaning given in the description of the invention.
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- Decarbonylation of Sugars by Chlorotris(triphenylphosphine)rhodium
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Unprotected aldose sugars are smoothly decarbonylated by 1 equiv. of chlorotris(triphenylphosphine)rhodium in N-methylpyrrolidin-2-one at 130 deg C to give he next lower alditol and carbonylchloribis(triphenylphosphine)rhodium; ketose sugars undergo more complex dehydration-decarbonylation reactions.
- Andrews, Mark A.,Klaeren, Stephen A.
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p. 1266 - 1267
(2007/10/02)
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- INTERACTION OF (1->4)- AND (1->6)-LINKED DISSACHARIDES WITH THE FENTON REAGENT UNDER PHYSIOLOGICAL CONDITIONS
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Reactions of (1->4) and (1->6)-linked disaccharides, mainly of maltose and isomaltose, with the Fenton reagent under physiologigal conditions were studied.Chemical characterization of oxidation products was conducted by g.l.c. and g.l.c.-m.s. of their trimethylsilyl derivatives, and the results demonstrated that (1->6)-linked disaccharides are more reactive with the hydroxyl radical (.OH) generated by the Fenton reagent than (1->4)-linked disaccharides.About 35-40percent of (1->6)- and 15-20percent of (1->4)-linked disaccharides were oxydatively degraded to smaller molecules after incubation for 24 h.Of the four disaccharides examined, namely, maltose, isomaltose, cellobiose, and gentiobiose, the α-(1->6)-linked disaccharide isomaltose exhibited the highest reactivity, whereas the β-(1->4)-linked disaccharide cellobiose showed the lowest.These results suggest the exisence of the a relationship between the configuration of the glycosidic linkage and the reactivity with .OH in aqueous solution.
- Uchida, Koji,Kawakishi, Shunro
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