Microwave-enhanced sub-critical hydrolysis of rice straw to produce reducing sugar catalyzed by ionic liquid

Abstract

The grain industry produces a great amount of rice straw, one of agricultural wastes. Because cellulose and hemicelluloses are rich in straw, it is also a main renewable biomass resource which can be converted to ethanol fuel. An effective and profitable process at relatively mild temperature under microwave heating with green solvent of ionic liquid ([Amim]Cl) as catalyst to produce reducing sugars from the hydrolysis of straw has both economical and environmental benefit. When the straw was hydrolyzed at relatively mild temperatures ranging from 140 to 220 °C and autogenous pressure by the intensification of microwave heating, the main hydrolysis products were determined to be glucose and xylose. With weight ratio of water/straw 40, weight content of ionic liquid (IL) in IL–water mixture 10%, temperature 180 °C and reaction time 60 min, the yield of glucose and xylose can attain 29.1 and 24.3%, respectively. The new method can not only obtain high yield of reducing sugar owing to their low degradation, but also remain high efficiency with microwave heating intensification and IL [Amin]Cl as catalyst.