Transformation of wheat straw polysaccharides under dynamic conditions of subcritical autohydrolysis

Abstract

Transformation of wheat straw polysaccharides under dynamic conditions of subcritical autohydrolysis has been examined at a pressure of 30 MPa in a temperature range of 150—290°C. The dependence of the yield of gaseous, liquid, and solid products on the process temperature has been studied. The formation of liquid products occurs mainly due to the hydrolysis of pentosans and partially of cellulose in a range of 150–200°C. The main components of liquid products are oligo- and monosaccharides. Xylose and arabinose comprise more than 65% of monosaccharides. A temperature rise in a range of 200–290°C is accompanied by a decrease in medium pH, cellulose hydrolysis, and intensive gasification. Glucose predominates in monosaccharides of liquid products isolated at 270°C; a portion of pentoses does not exceed 25% of the total of monosaccharides. The maximal yield of sugars is observed at 200°C and then decreases from 29.6 to 5.3% per straw oven-dry weight at 270°C. A decrease in reactivity of straw cellulose treated at 200°C to enzymatic hydrolysis has been found.