Effect of Redox Properties of LaCoO3 Perovskites on Production of Lactic Acid from Cellulosic Biomass
Xiaokun Yang, Lisha Yang, Hongfei Lin*
Department of Chemical and Materials Engineering, University of Nevada,
1664 N. Virginia St., Reno, NV 89557, USA
Cost-effective conversion of cellulosic biomass to value-added lactic acid with heterogeneous catalysts has attracted much attention recent years. While both solid Lewis acids and bases are extensively studied, which exhibit good catalytic performance but are unfortunately unstable in hydrothermal media, the role of redox catalysts for the production of lactic acid is barely understood. Herein, the LaCoO3 perovskite metal oxides with strong redox properties and a good stability in hydrothermal media were used as the catalyst for the conversion of a variety of cellulosic biomass to lactic acid. Different gas atmosphere including oxidative, inert and reductive gases had the profound effect on the yield of lactic acid. The effects of reaction conditions such as reaction temperature and catalyst loading were also investigated. At the optimum conditions, the yields of ~40%, 38%, and 24% lactic acid were obtained from glucose, xylose and cellulose, respectively. The key intermediates and final products were used as the probe reactants to explore the reaction mechanism. Unlike Lewis acid or base catalysed biomass conversion reaction pathways, our proposed redox reaction pathway has the distinct characteristic that lattice oxygen atoms in the LaCoO3 perovskite structure participate the redox cycles in the sugar conversion to lactic acid. The stability of the LaCoO3 catalyst was also discussed.