The Exploration Of The Hydrolysis Technology For Cellulose And Hemicellulose

The biomass is composed of cellulose, hemicelluloses and lignin. The celluloseand hemicellulose are both glycans and can be hydrolyzed into monosaccharide,which then can be further converted into some useful chemicals. As a result, it isimportant to the hydrolyze the cellulose and hemicellulose for the utilization ofbiomass. This paper researches the hydrolysis of cellulose and corn cob. Because ofthe large amount of hemicelluloses existing in the corn cob, the hydrolysis of corn cobstands for the hydrolysis of the hemicelluloses.The catalysts for the hydrolysis of cellulose are carbon-based solid acid andphosphotungstic acid.The carbon-based solid acid is prepared by incomplete carbonization of celluloseand the sulfonation of the carbonized cellulose. In this study, the cellulose is firstheated at the temperature of450oC for5h under nitrogen gas flow. As a result,activated-carbon is obtained. Then, the mixture of1.5g activated-carbon and30mlfuming sulphuric acid are heated at150oC for overnight. The resultant sulfonatedsolid is washed repeatedly with hot distilled water (≧80oC) until the sulfate ions areno longer detected in the wash water. At last, the black solid is heated at105oC untilits mass is constant. The results indicate that, under the microwave heating condition,at the temperature of140oC for2h, the glucose yield reaches as high as33%, whichis the most highest among all the results.When the phosphotungstic acid is applied as the catalyst, The results demonstrate that when the microwave heating is applied, the reaction temperature is90oC, thereaction time is3h, the glucose yield reaches as high as84%, and the celluloseconversion yield can reach as high as96%. Furthermore, the phosphotungstic acid canbe recycled by the extraction of diethyl--ether for reuse. The recycle yield is85%.Under the same react conditions, when the phosphotungstic acid is used for thesecond time, the glucose yield is66%, and48%for the third time. In a word, thephosphotungstic acid is an effective catalyst for the hydrolysis of cellulose and can bereused.The formic acid is applied as the catalyst for the research on the hydrolysis ofcorn cob. Because the formic acid as an organic solvent，its boiling point is low andcan be recycled easily for cyclic utilization to lower the cost. The results indicate thatunder the condition of microwave heating, when the concentration of formic acid is60%, the reaction temperature is100oC, the reaction time is120min, the xylose yieldcan reach as high as96%. However, when the traditional oli-bath heating is appliedand under the same reaction conditions, the xylose yield is only75%. So we canconclude that the microwave heating is helpful for shorting the reaction time andpromoting the reaction efficiency. Meantime, when the microwave heating is applied,the concentration of formic acid is60%, the reaction temperature is100oC，thereaction time is150min, the delignin yield can reach as high as72%. However, whenthe traditional oil-bath heating is applied, under the same reaction conditions, thedelignin yield is only as low as32%. So we can infer that the formic acid is useful forthe delignification, and the combination of microwave heating and formic acid cangenerate a better result.This paper researches the hydrolysis technology of cellulose and hemicelluloses.The research is meaningful for the full utilization of biomass resource, energy crisis,environmental pollution and the sustainable development of society.