(117f) Selective Oxidation of Sugars and Polyols to Disaccharic Acids on Pt-Based Catalysts in One Pot Process

Catalytic conversion of biomass-based sources to high value chemicals has attracted increasing interest because it provides renewable alternatives to those derived from petrochemical feedstocks. Sugars and polyols, such as glucose, xylose and glycerol are abundantly available from biomass resources. Oxidation of these oxygen functional feedstocks to disaccharic acids such as glucaric acid and tartronic acid shows promising industrial applications, because these acids are valuable pharmaceutical intermediates and food additives. More importantly, disaccharic acids are potential feedstocks for the production of various megaton everyday chemicals such as adipic acid, succinic acid and malonic acid.

Disaccharic acids were conventionally produced from biomass or petroleum crudes via nitroxidation, cyanide and biological routes, which generate large amounts of toxic side products with poor overall productivity and chemoselectivity toward desired products. Catalytic oxidation of biomass in the presence of molecular oxygen on metal catalysts (e.g. Pt, Pd) could potentially yield disaccharic acids in one step without producing any toxics. Selective oxidation of sugars and polyols to disaccharic acids is however challenging because of significant side reactions of feedstocks  to form smaller mono-acids, CO₂ as well as humic substances under reaction conditions (T = 40~80 ^oC in the alkaline medium). In addition, the reaction network of sugars to C_1~6 mono- and di-acids under oxidative conditions is not clearly understood at the current stage. Therefore, design of active and selective oxidation catalysts and fundamental understanding of reaction pathways/mechanism is the key to improve the overall yield of disaccharic acids from biomass. In particular, heterogeneous Pt-based catalysts have been evaluated and characterized for aqueous phase conversion of glucose, xylose and glycerol in the presence of molecular oxygen. Detailed kinetic studies taking into account the effects of Pt particle size, pH, temperature and oxygen pressure on the rate of oxidation, C-C cleavage and dehydration will be presented based on Pt-based catalysts.