Production of reducing sugar from corn stover by dilute acid hydrolysis co-catalyzed with metal salts under microwave radiation

Abstract

Acid hydrolysis of corn stover under microwave radiation by adding four metal salt co-catalysts (ferrous sulfate, copper sulfate, zinc sulfate, and manganese sulfate) to produce reducing sugar was investigated. The influences of microwave power, reaction time, sulfuric acid concentration, and co-catalyst concentration on the yield of reducing sugar were studied. The results show that the catalytic effects of ferrous sulfite and copper sulfate are more obvious for the yield of reducing sugar compared with only dilute acid hydrolysis with microwave radiation. Long-time microwave irradiation resulted in secondary hydrolysis, generating small-molecule compounds and decreasing the yield of reducing sugar. The reducing sugar yield was increased by decreasing the hydrolysis reaction time and microwave radiation power. In terms of reducing sugar yield, the four kinds of metal salt co-catalyst act in the order: ferrous sulfate > copper sulfate > sulfuric acid zinc sulfate > manganese sulfate. At concentration of 3.0 %, the best was ferrous sulfate, producing yield of 35.10 %.