Study Of Dilute Sulfuric Acid Pretreatment Of Corn Stover

Biomass is the most abundant renewable energy resource in the word. It contains plentiful hemicelluloses and can be hydrolyzed as a substrate to produce a wide variety of compounds or fuels by chemical or biotechnological processes. One such compound is xylose which can be converted to xylitol,an important raw material for industry.The dilute-sulfuric-acid pretreatment has been described as one of the most effective methods in hydrolyzing hemicelluloses. The objective of the study was to determine the effects of different hydrolysis conditions on the pretreatment of corn stover by dilute-sulfuric-acid. Response surface methodology(RSM) was adopted to design this study. Second-order model equations of different hydrolysis conditions were achieved. Based on the model equations and statistics software, the optimum hydrolysis conditions were assigned.First,the influential factors of pretreatment of the corn stover by dilute sulfuric acid were studied. The concentration of sulfuric acid,the hydrolyzing temperature, the solid content , the granularity of corn stover and the hydrolyzing time have effects on the hydrolyzing rate.High level of hydrolyzing rates and their corresponding span of the influential factors were attained.Based on the one-factor experiments of the influential factors, the objective of the study was to determine the effects of H2SO4 concentration and reaction time on the production of xylose and the selective coefficient under 121℃. Two second-order model equations for acid concentration and reaction time were achieved. Based on the two models and statistics software, the hydrolysis conditions to attain high levels of xylose yield and selectivity were defined using the following criteria:xylose yield>75% and electivity>4.0g/g. Thus, an optimum hydrolysis condition corresponding to 2.0% of acid concentration and 43min was assigned.Corn stover was hydrolysed using dilute sulfuric acid at variable concentration (2%, 4% and 6%) and reaction time (0min~300min)at 100℃. Kinetic parameters of mathematical models for predicting the concentrations of xylose, glucose and furfural in the hydrolysates were founded. Optimal conditions for hydrolysis were 5.5% H2SO4 at 100℃for 90min, which yielded a solution with 19.91g xylose/l, 7.61g glucose/l and 0.84g furfural/l. Corn stover was hydrolysed using dilute sulfuric acid at variable concentration (2%, 4% and 6%) and reaction time (0min~300min) at 80℃. The concentrations of xylose,glucose and furfural were determined and the kinetic parameters of mathematical models for predicting them in the hydrolysates were obtained. Optimal conditions for hydrolysis were 6% H2SO4 at 80℃for 240min. Using these conditions, 13.54g xylose/l; 5.39g glucose/l and 1.05g furfural/l were obtained.