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.

Catalytic oxidation of carbohydrates into organic acids and furan chemicals

With the progressive increase in global energy demands and the continuous depletion of worldwide fossil resources, renewable lignocellulosic biomass has attracted more and more attention. As the most abundant component of lignocellulosic biomass, cellulose, which is a linear polymer formed by the repeating connection of glucose units through β-1,4-glycosidic linkages, is considered to be an inexhaustible raw material for the sustainable production of chemicals and fuels. For the effective utilization of cellulose, the primary and essential step is the hydrolysis of cellulose into glucose. Although homogeneous acids and cellulases are the most common catalysts for the hydrolysis of cellulose into glucose, they possess a series of problems such as reactor corrosion, waste treatment and poor recyclability and high cost, low efficiency and long reaction time, respectively. In order to overcome the above-mentioned drawbacks, solid acid catalysts have been increasingly employed for the hydrolysis of cellulose into glucose in recent years. In this review, the state-of-the-art studies on the hydrolysis of cellulose into glucose over various types of solid acid catalysts such as acid resins, metal oxides, H-form zeolites, heteropoly acids, functionalized silicas, supported metals, immobilized ionic liquids, carbonaceous acids and magnetic acids are systematically summarized. Meanwhile, reaction medias, auxiliary methods and neoteric strategies for the hydrolysis of cellulose into glucose are intensively discussed. Furthermore, some potential research trends in the future are also prospected to provide some valuable ideas for the hydrolysis of cellulose into glucose in a more green, simple, efficient and inexpensive way.

Chemocatalytic hydrolysis of cellulose into glucose over solid acid catalysts

Heterogeneous catalysis for bio-based polyester monomers from cellulosic biomass: advances, challenges and prospects

Recent advances in the catalytic production of glucose from lignocellulosic biomass

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Catalytic Approaches to Monomers for Polymers Based on Renewables

A novel facile two-step method for producing glucose from cellulose

Responsive behavior of regenerated cellulose in hydrolysis under microwave radiation.

A novel zinc-stabilized UV-Fenton reaction is created to decompose cellulose under mild, organic solvent-free conditions. Cellulose is successfully decomposed to form a valuable C2 chemical, namely glycolic acid. The zinc ion enhances the yield of glycolic acid via complexation. The whole process is simple, rapid and controllable. This method shows a great commercial potential due to its simplicity and mild reaction conditions.

Direct conversion of cellulose into glycolic acid by a zinc-stabilized UV-Fenton reaction

Glucose preparation method by hydrolyzing cellulose through microwave heating

The invention discloses a method for preparing glycolic acid from glycerinum. Glycerinum used as a raw material and water used as a solvent undergo an oxidative degradation reaction in the presence of an oxidizing agent and a stabilizing agent under the condition of UV-irradiation, so as to obtain glycolic acid. The stabilizing agent is a zinc compound. According to the invention, peroxide is decomposed through ultraviolet light to generate free radical simultaneously with cooperation of the stabilizing agent, so as to realize selective regulation and control of the product. Steps for preparation of the glycolic acid by the above method are simple, heating and compression are not required, and the method is easy to control. The oxidizing agent and the stabilizing agent used in the invention are low-cost, and no organic solvent is needed in the degradation process. Under the mild condition, preparation conversion of the product is realized. In comparison with a present conversion method of a micromolecular raw material from a petroleum-base source, the method provided by the invention has obvious advantages. The method is a green, environmentally-friendly, efficient and economical glycolic acid production method which has huge potential.

She Zhen

Papers

A novel facile two-step method for producing glucose from cellulose

Responsive behavior of regenerated cellulose in hydrolysis under microwave radiation.

Direct conversion of cellulose into glycolic acid by a zinc-stabilized UV-Fenton reaction

Glucose preparation method by hydrolyzing cellulose through microwave heating

Method for preparing glycolic acid from glycerinum