Catalytic Oxidation Of Carbohydrates Research Articles

Stepwise photoassisted decomposition of carbohydrates to H2

Stepwise photoassisted decomposition of carbohydrates to H2

Catalytic oxidation of carbohydrates into organic acids and furan chemicals.

A wide variety of commodity chemicals can be produced from the catalytic oxidation of carbohydrates or carbohydrate derived molecules including formic acid, acetic acid, glycolic acid, gluconic acid, glucaric acid, malonic acid, oxalic acid, 2,5-diformylfuran (DFF), 5-hydroxymethyl-2-furancarboxylic acid (HFCA), 5-formyl-2-furancarboxylic acid (FFCA), and 2,5-furandicarboxylic acid (FDCA). This review will highlight the recent research progress in the development of new routes for the production of organic acids and furan compounds via catalytic oxidation reactions. Particular attention will be paid to these one-pot reactions with the requirements of an acidic site and a metal site. For the one-pot transformation of cellobiose or lignocellulose into gluconic acid, these reactions were performed via a one-step strategy using a single catalyst containing an acidic site and a metal site. However, a two-step strategy was adopted for the oxidative transformation of carbohydrates into DFF or FDCA in order to avoid the oxidation of the carbohydrates. The first step was performed for the dehydration of carbohydrates into 5-hydroxylmethylfuran (HMF) in the presence of an acid catalyst, and the second step was performed for the oxidation of HMF into DFF or FDCA with a metal catalyst.

Electrical energy from carbohydrate oxidation during viologen-catalyzed O2-oxidation: Mechanistic insights

Catalytic oxidation of carbohydrates by oxygen using various viologens under mild conditions was recently shown to occur at high efficiency with formate and carbonate formed as products. However, high efficiency was only achieved at viologen/carbohydrate ratios >10. The use of such high catalyst ratios is undesirable and a mechanistic study was initiated to better understand how catalytic efficiency is influenced by catalyst ratio. The results suggest that the dipositive viologen reacts with the enediol form of the carbohydrate, initiating carbohydrate oxidation with subsequent reduction of the viologen to the radical cation form. The latter is then oxidized by air or by current collecting electrodes when the reaction is conducted in a fuel cell. If the viologen/carbohydrate ratio is low, electron transfer from the carbohydrate to the oxidized form of the viologen becomes limiting and the carbohydrate undergoing oxidation rearranges into unreactive intermediates such as carboxylic acids, and alcohols. However, at high ratios, excess viologen more efficiently oxidizes the carbohydrate and minimizes formation of unreactive intermediates. Viologen polymers were more efficient than an equivalent concentration of monomers, suggesting that the higher localized concentration in polymeric viologen acts to efficiently oxidize carbohydrates and simulates high viologen/carbohydrate ratios. The use of viologen films on electrodes or conducting viologen polymers should facilitate use of carbohydrates for electricity production in fuel cells.

Nickel hydroxide electrodes as amperometric detectors for carbohydrates in flow injection analysis and liquid chromatography

The present paper describes the utilization of nickel hydroxide modified electrodes toward the catalytic oxidation of carbohydrates (glucose, fructose, lactose and sucrose) and their utilization as electrochemical sensor. The modified electrodes were employed as a detector in flow injection analysis for individual carbohydrate detection, and to an ionic column chromatography system for multi-analyte samples aiming a prior separation step. Kinetic studies were performed on a rotating disk electrode (RDE) in order to determine both the heterogeneous rate constant and number of electrons transferred for each carbohydrate. Many advantages were found for the proposed system including fast and easy handling of the electrode modification, low cost procedure, a wide range of linearity (0.5–50 ppm), low detection limits (ppb level) and high sensitivities.

Electrochemical detection of carbohydrates at carbon-nanotube modified glassy-carbon electrodes

This communication reports on the catalytic oxidation of carbohydrates and the sensitive and stable fixed-potential (+0.45 V) amperometric carbohydrate response at glassy-carbon electrodes modified with single-wall carbon-nanotube (CNT) coatings. Variables affecting the electrocatalytic oxidation are assessed and optimized. The oxidation process starts around +0.25 V using a 0.1 M NaOH electrolyte solution. The amperometric response is extremely stable, with no loss in sensitivity over a continuous 2 h operation. The flow-injection response is characterized with a detection limit of 10 μM galactose and a relative standard deviation of 3.45% ( n=20). Such attractive performance characteristics indicate great promise for monitoring sugars in chromatographic effluents.

ChemInform Abstract: Hydrogen Peroxide and Oxygen in Catalytic Oxidation of Carbohydrates and Related Compounds

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Hydrogen Peroxide and Oxygen in Catalytic Oxidation of Carbohydrates and Related Compounds

The state of the art of carbohydrate oxidations with molecular oxygen, hydrogen peroxide and ozone is presented in this review. Catalysed and uncatalysed reactions are described and are related by means of several reaction mechanisms. Several alcohols that are frequently applied as models for carbohydrates are included. Emphasis is given to the selective catalytic reactions. Two summarising reaction schemes conclude the possibilities for oxidations of both reducing and non-reducing sugars.

Liquid-phase catalytic oxidation of carbohydrates by oxygen: Glucose oxidation in alkaline solutions in the presence of copper(II) complexes

Liquid-phase catalytic oxidation of carbohydrates by oxygen: Glucose oxidation in alkaline solutions in the presence of copper(II) complexes

831. Catalytic oxidation of carbohydrates. Some properties of potassium α-D-glucopyranuronate 1-(dipotassium phosphate)

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