Autohydrolysis Pretreatment of Corn Stalk for Improved 5-Hydroxymethylfurfural Production in Molten Salt Hydrate/Acetone

Abstract

Molten salt hydrate (MSH) is unique in cellulose dissolution and performs high efficiency in one-pot conversion of crystalline cellulose into 5-hydroxymethylfurfural (5-HMF).  However, limited 5-HMF yield was obtained when raw biomass was used as substrate in MSHs. For potential industrial applications, this work focused on selective production of 5-HMF from cellulose due to its economic advantages. We showed that the formation of acetic acid from hemicellulose degradation in MSH is the key reason which affected 5-HMF degradation. Based on this discovery, an autohydrolysis pretreatment method was proposed to remove hemicellulose before converting cellulose into 5-HMF. After being pretreated at 180 oC for 40 min, hemicellulose was sufficiently removed from biomass, with 91.8% yield of cellulose isolated in solid part. By eliminating the negative effect of hemicellulose, 5-HMF yield was significantly improved from 40.9% to 64.6%, together with 9.3% yield of glucose in cellulose conversion in MSH/acetone at 180 oC for 20 min.

Keywords: molten salt hydrate, corn stalk, 5-hydroxymethylfurfural, autohydrolysis pretreatment, stepwise conversion.