Simultaneous Catalytic Conversion of C6 and C5 Sugars to Methyl Lactate in Near-critical Methanol with Metal Chlorides

Abstract

Cellulose and hemicellulose make up roughly two-thirds of lignocellulose. Currently, research is mainly focused on converting them to different chemicals, which causes low utilization rates and high separation costs. In this work, the simultaneous conversion of C6 and C5 sugars from cellulose and hemicellulose to methyl lactate in near-critical methanol with 15 different types of metal chlorides was studied. The trends of the catalytic conversions of C6 and C5 sugars with different metal chlorides were similar. Methyl lactate yield initially increased and then decreased steadily with an increase in the pKa value of the metal ions, which suggested that medium Lewis acidity was favorable for the production of methyl lactate. A possible reaction mechanism was proposed. The results will provide direction for the preparation of heterogeneous catalysts for simultaneously converting cellulose and hemicellulose to methyl lactate.