Direct Conversion of Cellulosic Biomass to Alkyl Lacatate on Mesoporous Zr-Silicates

Direct Conversion of Cellulosic Biomass to Alkyl Lacatate on Mesoporous Zr-Silicates

Lisha Yang¹, Xiaokun Yang¹, and Hongfei Lin¹*

¹ Department of Chemical and Materials Engineering,

University of Nevada, Reno

1664 N. Virginia St., Reno, NV 89557, USA.

Fax: (+1) 775-327-5059;

*E-mail: HongfeiL@unr.edu

Abstract

Biomass-derived lactic acid esters are "green" solvents that are not only biodegradable but also non-toxic. In this study, a variety of Zr-SBA-15 materials, which possess strong Lewis acid sites and weak Brønsted sites, were synthesized with tunable structures and pore sizes. The optimized Zr-SBA-15 catalyst showed excellent performance for the conversion of sugars to lactic acid esters in a "one-pot" reaction system. The effects of reaction conditions, including temperature, reaction time, and catalyst loading amount, on the conversions of carbohydrates and the corresponding yields of lactate were investigated.  The carbon yields of methyl lactate, up to 41 % and 44%, were produced from pentose and hexose, respectively. The key intermediates such as glyceraldehyde, glycolaldehyde and pyruvaldehyde were used as probe reactants to understand the mechanism.  The role of the catalyst in the retro-aldol condensation of carbohydrates, as well as the catalyst stability, has been discussed.  Furthermore, the carbon yield of ethyl lactate, up to 33% was produced directly from cellulose with the hydrophobic Zr-SBA-15 catalyst in the water-ethanol mixed solvents.