Tight control of cellulose depolymerization towards glucose in organic electrolyte solutions

Abstract

Organic electrolyte solutions (OES) prepared by combination of an ionic liquid (1-Butyl-3- methylimidadozium chloride) with dimethyl sulfoxide (DMSO) have been tested as reaction media for the controlled hydrolysis of cellulose. The use of these mixtures is justified because of they provide an excellent media for the solubilization of cellulose, while saving a significant fraction of expensive ionic liquids. Cellulose hydrolysis tests performed in presence of these OES media have been used to determine the influence of several important operational reaction variables. These include the determination of the influence of the mineral acid used as catalyst, the reaction temperature, the amount of water as well as the addition rate of the same to the reaction media in the production of glucose. While the presence of mineral acid is mandatory, not only to accomplish cellulose hydrolysis, but to maintain the polysaccharide under solution, the amount of water and its addition rate is crucial to provide a proper control in the hydrolytic cleavage of 1,4-glucoside bondings between glucose units. While low amounts of water hampers the cellulose hydrolysis rate and produces large yields of by products coming from the dehydration of glucose, the opposite leads to the precipitation of the polysaccharide. In both cases a low yield towards glucose is achieved. In this way, the control of the water concentration in the reaction media, together with the use of an appropriate reaction temperature, allows maximizing the production of glucose with an outstanding selectivity towards this monosaccharide, leading to the transformation of more than 90% of the starting dissolved cellulose into glucose. This methodology can be easily adapted to the transformation of other cellulosebased materials, such as biomass-feedstocks like wheat straw or paper-derived materials.