SPORL Pretreatment For Robust Enzymatic Hydrolysis Of Corn Stover

Ethanol production from lignocellulosic materials has become an inevitable trend of new energy development.The pretreatment is one of the critical steps in the transformation of lignocellulosic materials to ethanol, which would directly influence hydrolysis efficiency of cellulose and cost of ethanol production. At present many pretreatment methods have been researched and developed. However, there are a number of problems, such as, low efficiency, high cost, and high energy consumption in the actual production. Therefore, it is necessary for the industrialization of ethanol to study a pretreatment method with high effectiveness and low investment.In this paper, corn stover was used as raw material for pretreatment. The influences of several process variables, the reaction course of SPORL pretreatment at different holding temperature, pretreatment of integrated SPORL and steam explosion, application of surface active agents to enzymatic hydrolysis were investigated by analyzing dissolution rate of lignin, dissolution/retention rate of pentosan, cellulose conversion and glucose yield.Firstly, the influences of several process variables of SPORL pretreatment were studied. The optimal conditions were at the dose of sodium bisulfite 4.5%, sulfuric acid 1.84%, temperature 165? and holding time 1h. Different types of pretreatment equipment have influence on enzymatic hydrolysis, which the conversion rate of enzymatic hydrolysis is 94.14% when the pre-impregnation condition was 4.5%NaHSO3+1.84%H2SO4 before steam explosion. The conversion rate of enzymatic hydrolysis when substrates were disintegrated and refined was more 20% than which were not mechanically treated.Secondly, the reaction course of SPORL pretreatment was studied at the maximum reaction temperature of 180? and 165?,respectively. When the maximum temperature was 180?, lignin dissolution rate increased with the elevation of the temperature; pentose dissolution rate rose at the beginning, but the rate began to decrease beyond 160?; The trend of conversion rate of enzymatic hydrolysis and glucose yield increased with elevated temperature and extended time, which was little change after 180? When the maximum temperature was 165?, with the exaltation of the temperature and the extension of time, the trend of lignin dissolution rate was up, and the trend of pentose retention rate was down. When the temperature rosed to 165? for holding 30min, pentose dissolution rate reached the highest, and conversion rate of enzymatic hydrolysis was 93.68%.Thirdly, through anylazing the substrate enzyme hydrolysis conversion rate and the chemical components content of substrate, the effect of chemical amount, the saturated vapor pressure and time was also discussed. And then the optimal condition of integrated SPORL and steam explosion process was achieved:chemicals addition amount of 4.5% NaHSO3 and 1.84% H2SO4, saturated vapor pressure 1.92MPa for 5min. In the above condition, the enzymatic conversion rate was up to 95.81%.Finally, the influence of OP series surfactant with different HLB values on enzymatic hydrolysis was investigated for substrates with SPORL pretreatment. When cellulase dosage was 7 FPU/g, surfactant OP-7 had promoting effect on enzymatic hydrolysis. When the dosage of OP-7 is 1.5%, conversion rate of enzymatic hydrolysis reached 95.43%, which is more 21.16% than that of control.