Production of Lactic Acid from Sugars by Homogeneous and Heterogeneous Catalysts

Abstract

Lactic acid (2-hydroxypropionic acid, CH3CHOHCOOH) is one of the platform chemicals derived from biomass. It is used in the food industry and in the manufacture of biodegradable plastics and useful chemicals. Recently, various examinations were carried out not only by fermentation but also by the chemical methods using heterogeneous and homogenous catalysts. This chapter focuses on the chemical processes with heterogeneous catalysts in lactic acid and lactate ester productions from sugars. Bronsted basic catalysts and Lewis acid catalysts gave lactic acid in high yields. In the lactic acid productions from triose, lactic acid ester is obtained with high yields of nearly 100 % in alcohols around 100 °C using Sn-β zeolite, Sn–carbon–silica, and H-USY catalysts. In the lactic acid production from hexose, lactic acid ester or a lactate salts was obtained from glucose, fructose, and sucrose with the comparatively high selectivity of about 50 % by several catalytic processes, that were in water around 50 °C using heterogeneous basic catalysts, such as activated hydrotalcite catalyst, in hydrothermal water around 300 °C using homogeneous basic catalysts, such as NaOH and ZnSO4, and in alcohols around 160 °C using heterogeneous Lewis acid catalysts, such as Sn-β zeolite.