Study On Key Problems In Bioethanol Conversion From Steam Explosion Combined With Chemical Method Treated Cotton Stalk

Cotton stalks are valuable biomass resources rich in lignocellulose,which can be used for biotransformation and energy regeneration and are considered to be the main resources for biofuels.Like other biomass materials,cotton stalks are mainly composed of cellulose,hemicellulose and lignin.Due to the high lignin content,cotton stalks are extremely difficult to achieve direct saccharification or biotransformation.Therefore,pretreatment should first be carried out to destroy the structure of lignocellulose,and steam explosion?SE?is a pretreatment method with wide application range,commercialization prospect and environmental friendliness in the conversion of lignocellulosic feedstock.Because it avoids the secondary pollution problem of chemical treatment and solves the problem of low biological treatment efficiency,it is the most promising pretreatment technology in the field of biomass conversion.In this study,the instantaneous ejection steam blasting technology equipment was used to explore the effect of different factors on steam blasting and further to find the optimal blasting parameters and conditions.In addition,seek the best blasting parameters and conditions,find out the main factors affecting the saccharification efficiency of steam blasting straw,and specifically crack its anti-degradation barrier,explore the structural characteristics of lignin,and improve the efficiency of biomass utilization,promote the development of the fiber ethanol industry.The response surface method was used to design the experiment,and the cotton stalk was pretreated under different steam explosion conditions.The effect of steam explosion on hemicellulose,cellulose and enzyme sugar production was observed to evaluate the effect of steam explosion treatment.Analyze the factors affecting steam explosion.The optimized conditions were as follows:steam explosion pressure 1.59 MPa,steam explosion time 186.89s,water content 30.63%;under these conditions,the experimental results were verified to have a cellulose content of 45.26% and a hemicellulose content of 22.46%.The hydrolysis rate was 44.59%,which was in good agreement with the predicted values,indicating that the established model was reasonable and effective.Steam explosion was found to effectively remove hemicellulose and improve hydrolysis efficiency.The lignin content was hardly affected before and after steam explosion.The analysis of lignin monomer?H,G,S?showed that the lignin monomer content increased after steam explosion pretreatment,and the steam explosion pressure increased.The effect on the content of lignin monomer also increases.The single factor experiment showed that the steam detonation cotton rod degraded and released the reducing sugar and the type and content of the substrate,the enzyme interaction,the enzymatic hydrolysis temperature and the enzymatic hydrolysis time were significantly correlated,and the laboratory scale steam explosion cotton rod was optimized by the response surface method.Enzymatic conditions:cellulase percentage 50%,enzymatic temperature45?,solid content 5%,hydrolysis time 72 h.The enzymatic hydrolysis effect of cellulase and xylanase is significantly better than that of single enzyme,which indicates that further xylanase and cellulase have better synergistic effect.Enzymatic hydrolysis can significantly increase lignocellulose.The hydrolysis efficiency of the substrate increases the utilization rate.Based on the steam blasting cotton rod,combined with chemical method for pretreatment,using the synergistic effect of cellulase and xylanase in the hydrolysis of natural lignocellulosic substrate,compared with steam blasting combined with different concentrations of monobasic acid?HCl?),the yield of sugar released by the mixed enzymatic hydrolysis of monobasic weak acid,?CH₃COOH?,monobasic strong base?NaOH?,monobasic weak base?NH₃·H₂O?,and mixed alkali pretreated cotton stalk substrate.It was found that the yield of reducing sugar in SE-2.4MPa-5% NH₃·H₂O pretreated cotton rods was up to 73.22%.Compared with other combined pretreatment methods,steam explosion combined with ammonia pretreatment is a kind of low energy consumption and no pollution.An effective means of high enzymatic efficiency.The hydrolysis process of steam blasting combined with NaOH pretreated cotton stalks in mixed enzymes was also studied.The genetic algorithm was used to optimize the conditions of BP neural network for steam blasting combined with NaOH pretreatment of cotton stalks in mixed enzymes?steam explosion pressure,steam explosion?.Time,sodium hydroxide concentration and enzymatic hydrolysis time were simulated and optimized.The results showed that when the steam explosion pressure,steam explosion time,sodium hydroxide concentration and enzymatic hydrolysis time were 1.6MPa,180s,1%and 72h,respectively,the yield of reducing sugar was the highest,which was 62.75%.After many trainings,it was established.The neural network model?4-15-1?,the MSE of the model is small,R is 0.9148,indicating that the model performance is good;the yield of reducing sugar obtained by the verification experiment is very close to the predicted value of the model equation,indicating that the prediction model is within the experimental range.Reasonable and effective;the influence of various factors on reducing sugar yield is:steam explosion pressure?MPa?>NaOH concentration?%?>steam explosion time?s?>hydrolysis time?h?.Furthermore,the effects of lignin monomer on the hydrolysis of cotton stalks by steam explosion combined chemical treatment were discussed.It was found that there was a strong positive correlation between G monomer and S monomer and enzyme saccharification rate.H monomer content and hydrolysis release There is a certain inhibition between the sugars.