The catalytic epimerization of sugars over immobilized heptamolybdate: comparison of resins, layered double hydroxides and mesoporous silica as support

Stockman, Robert A.; Dekoninck, Jm.; Sels, Bert F.; Jacobs, Pierre

doi:10.1016/s0167-2991(05)80295-2

Cited by 6 publications

(5 citation statements)

References 13 publications

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“…Although binuclear molybdate species were implicated in epimerization reactions catalyzed by water-dissolved MoO 3 , higher structures containing molybdate ions were later shown to also catalyze epimerization reactions, e.g., Keggin structure molybdenum-based polyoxometalates (19), and heptamolybdate species immobilized on anion exchange supports (20). Similarly, we observe the promotion of retro-aldol reactions of fructose by the H 3 PMo 12 O 40 Keggin ion, and by (NH 4 ) 6 Mo 7 O 24 , both as homogeneous catalysts and when immobilized onto an anion exchange support, e.g., Amberlite IRA-400, chloride form.…”

Section: Resultsmentioning

confidence: 99%

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Orazov

Davis

2015

Proc. Natl. Acad. Sci. U.S.A.

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Retro-aldol reactions have been implicated as the limiting steps in catalytic routes to convert biomass-derived hexoses and pentoses into valuable C2, C3, and C4 products such as glycolic acid, lactic acid, 2-hydroxy-3-butenoic acid, 2,4-dihydroxybutanoic acid, and alkyl esters thereof. Due to a lack of efficient retro-aldol catalysts, most previous investigations of catalytic pathways involving these reactions were conducted at high temperatures (≥160 °C). Here, we report moderate-temperature (around 100 °C) retro-aldol reactions of various hexoses in aqueous and alcoholic media with catalysts traditionally known for their capacity to catalyze 1,2-intramolecular carbon shift (1,2-CS) reactions of aldoses, i.e., various molybdenum oxide and molybdate species, nickel(II) diamine complexes, alkali-exchanged stannosilicate molecular sieves, and amorphous TiO2–SiO2 coprecipitates. Solid Lewis acid cocatalysts that are known to catalyze 1,2-intramolecular hydride shift (1,2-HS) reactions that enable the formation of α-hydroxy carboxylic acids from tetroses, trioses, and glycolaldehyde, but cannot readily catalyze retro-aldol reactions of hexoses and pentoses at these moderate temperatures, are shown to be compatible with the aforementioned retro-aldol catalysts. The combination of a distinct retro-aldol catalyst with a 1,2-HS catalyst enables lactic acid and alkyl lactate formation from ketohexoses at moderate temperatures (around 100 °C), with yields comparable to best-reported chemocatalytic examples at high temperature conditions (≥160 °C). The use of moderate temperatures enables numerous desirable features such as lower pressure and significantly less catalyst deactivation.

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Section: Resultsmentioning

confidence: 99%

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Orazov

Davis

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Additionally, the nature of the polyanion might directly influence the hydrolysis reaction, as sugar molecules have been reported to strongly complex with This journal is © The Royal Society of Chemistry 2011 polyoxometalates such as in the epimerization of glucose in mannose. 34 The lower selectivity in the CsPW system can either be attributed to an outbalanced acid vs. redox capacity, 1 i.e. the fast hydrolysis might outpace the hydrogenation reaction, leading to selectivity loss through degradation of accumulated glucose, or to an influence of the polyanion on the hydrogenolysis side reaction.…”

Section: Resultsmentioning

confidence: 99%

Hydrolytic hydrogenation of cellulose with hydrotreated caesium salts of heteropoly acids and Ru/C

et al. 2011

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“…A rare exception to this mechanism was discovered by Bílik, who showed that treatment with catalytic amounts of molybdic acid under acidic conditions will epimerize aldoses via transition states that promote a 1,2 carbon shift 28 . Many catalytic systems based on molybdate chemistry have been investigated 29 30 . The accepted mechanism involves the complex formation of a binuclear molybdate species with four adjacent hydroxyl groups (OH-1 to OH-4) in the sugar 31 32 .…”

Section: Discussionmentioning

confidence: 99%

Sn-Beta zeolites with borate salts catalyse the epimerization of carbohydrates via an intramolecular carbon shift

et al. 2012

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Carbohydrate epimerization is an essential technology for the widespread production of rare sugars. In contrast to other enzymes, most epimerases are only active on sugars substituted with phosphate or nucleotide groups, thus drastically restricting their use. Here we show that Sn-Beta zeolite in the presence of sodium tetraborate catalyses the selective epimerization of aldoses in aqueous media. Specifically, a 5 wt% aldose (for example, glucose, xylose or arabinose) solution with a 4:1 aldose:sodium tetraborate molar ratio reacted with catalytic amounts of Sn-Beta yields near-equilibrium epimerization product distributions. The reaction proceeds by way of a 1,2 carbon shift wherein the bond between C-2 and C-3 is cleaved and a new bond between C-1 and C-3 is formed, with C-1 moving to the C-2 position with an inverted configuration. This work provides a general method of performing carbohydrate epimerizations that surmounts the main disadvantages of current enzymatic and inorganic processes.

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The catalytic epimerization of sugars over immobilized heptamolybdate: comparison of resins, layered double hydroxides and mesoporous silica as support

Cited by 6 publications

References 13 publications

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Hydrolytic hydrogenation of cellulose with hydrotreated caesium salts of heteropoly acids and Ru/C

Sn-Beta zeolites with borate salts catalyse the epimerization of carbohydrates via an intramolecular carbon shift

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