| With the depletion of fossil fuels, deterioration of haze and the gloomy of the first generation of fuel ethanol with every passing month, the second generation of cellulosic ethanol has become the challenge which the researchers have to solve. Pretreatment process is the key problem converting the lignocellulosic materials into cellulosic ethanol. Many pretreatment methods have been developed in the recent years, but low efficiency, high cost and air pollution still exist in the practical application. Therefore, it will be very significant to develop a kind of high efficiency, low cost and environment friendly pretreatment method of lignocellulsic materials for realizing the industrialization of fuel ethanol.Acid catalytic ethanol pretreatment method was used to treat the wheat straw materials, and the experiment scheme was designed by the model One-Factor in the Design-Expert software. The pretreatment condition was fixed at ethanol concentration 65%(v/v), reaction temperature 175℃,reaction time 54.6 min, catalyst dosage 1.4%(w/odw). Effect of the liquid to solid ratio on the cellulose recovery yield, pentosan content and lignin content of solid residue after pretreatment was studied, and made them as responses to optimize the most feasibility liquid to solid ratio 1:3.The model Box-Behnken in the Design-Expert software was used to design the experiment scheme. Catalyst dosage was fixed at 1.4%(w/odw), liquid to solid ratio was fixed at 1:3.The center point condition was ethanol concentration 65%(v/v), reaction temperature 175℃, reaction time 54.6 min. The effect of ethanol concentration, reaction temperature and reaction time on the chemical and physical characteristics of solid residue after pretreatment was invested respectively. The results indicated that the cellulose recovery yield of solid residue could reach up to 98.82%, pentosan content and lignin content could reach up to 2.44% and 4.96%, respectively; Crystallinity of the solid residue ranked from 69.75% to 79.63% under different pretreatment conditions; Fiber average length concentrated in about 0.88 mm and average width in about 21μm; Pore diameter of fiber concentrated in about 2-50 nm, belong to the category of mesopore, and the biggest BET specific surface area of pulp is 21.29 m2/g under different conditions.Enzyme hydrolysis performance of the substrate pretreated under broad conditions was evaluated. Results indicated that wheat straw pretreated by acid catalytic ethanol pretreatment method possessed excellent enzymatic hydrolysis desirability, enzymatic efficiency could reach up to 96.32% at cellulase dosage of 5 FPU/g substrate and cellubiase dosage of 10 CBU/g substrate. The RSM method with regarding the enzymatic efficiency as response was used to analyze the influence of different pretreatment conditions on enzymatic efficiency. The results indicated that reaction temperature had the greatest influence on enzymatic efficiency, then ethanol concentration. Quadratic polynomial regression is used to fitted enzymatic efficiency, but the Pred R-square of the mathematical model was negative value, and this meant the enzymatic efficiency could not be quantitatively forecast by controlling the pretreatment conditions.In the last part of this thesis, SPSS Statistics was used to analyze the correlation of chemical and physical characteristics of pulp and the enzymatic efficiency, and got a clear understand of relationship between each valarray. The results indicated that SPSS was suitable for analyzing the correlation of valarrays... |
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