Production of Glucaric/Gluconic Acid from Biomass by Chemical Processes Using Heterogeneous Catalysts

Abstract

Gluonic acid is a platform chemical that can be derived from biomass for making plastics and food additives, while glucaric acid is expected to be a sustainable precursor for producing adipic acid. This chapter provides an overview of the chemical processes for the production of gluconic acid and glucaric acid from mono-saccharides and poly-saccharides with a focus on heterogeneous catalysts. Because catalytic conversions of biomass are usually in aqueous solutions, the solid catalysts must be water tolerant. The oxidation of glucose into gluconic acid has been well-investigated using supported noble metals, such as Pt, Pd, and Au catalysts and those bimetallic catalysts, such as PdAu and PtBi. For the heterogeneous catalytic oxidation of glucose in aqueous solutions, three hypotheses can be used to explain catalyst deactivation: (i) poisoning of the catalyst by oxygen or hydrogen, (ii) poisoning of the catalyst by products, and (iii) metal sintering and metal leaching. Bimetallic catalysts with appropriate compositions have higher activity than those of monometallic catalysts to inhibit poisoning of oxygen, hydrogen, and acidic products. Supported Au catalyst also shows high yields of gluconic acid in aqueous solutions even without pH control. On the other hand, compared with oxidation of glucose to gluconic acid, oxidation into glucaric acid is a challenging reaction because an oxidation step from gluconic acid to glucaric acid is slow. Among tested catalysts, supported Pt and PtCu catalysts show relatively high glucaric acid yields. Direct production of gluconic acid from polysaccharides using bifunctional catalysts is also discussed. Bifunctional catalysts, such as sulfonated activated-carbon supported platinum, have acidic active sites and redox actives sites that can provide efficient conversion of gluconic acid and glucaric acid from polysaccharides.