Study On Acid Hydrolysis Of Rice Straw And Biotransformation Manufacturing Fuel Ethanol

With the aggravation of energy crisis,the development and utilization of biomass has become the research hot spots.Rice straw is an important biomass,with wide distribution and enormous amount.It was incinerated uausally,resulting in serious waste of resources and environmental pollution.Due to its high content of lignin,which would easily produce inhibitors to fermentation after treatment,the research work of rice straw has just started.Comprehensive development of biomass energy has strategic significance.The experiments of hydrolysis of rice straw catalysed by dilute sulfuric acid were conducted.The influences of concentration of acid, reaction temperature and reaction time on hydrolysis of rice straw producing reducing sugar were discussed in this thesis.The results showed that hydrolysis of rice straw using dilute sulfuric acid can leave out the progress of pretreatment,with good yield of reducing sugar.The optimum reaction conditions of hydrolysis of rice straw by dilute sulfuric acid were as follows:dilute sulfuric acid mass fraction 20%,reaction temperature 60℃,reaction time 36 h,and the largest yield of reducing sugar can reach 30.41%under these conditions.When the ratio of solid to liquid(W/V) was 1:10,the concentration of reducing sugar can reach 23.835 g/L. Hydrochloric acid and mixed acid contrast test showed that the mixed acid had the highest efficiency to hydrolysis of rice straw,and could significantly shorten the reaction time.For the total progress of hydrolysis of rice straw,we considered that the hydrolysis of hemicellulose was taken at the first 4 hours,and cellulose at 16 hours to 36 hours,the whole progress finished after 36 hours.The detoxification of the obtained acid-hydrolysis solution was studied,and the existing detoxification methods were improved.The rice straw acid-hydrolysis solution was excessive neutralized using calcium hydroxide while pH reached 8-9,accurately regulating to 7.0 using phosphoric acid.Then 3%of volume rate of add activated carbon were added in,after stirring for 30-40 minutes at 60℃,filtered,and concentrated on vacuum.The influence factors of fermentation of rice straw acid-hydrolysis solution after detoxification to produce ethanol were discussed in this thesis,such as concentration of reducing sugar,pH,and concentration of ethanol.The optimum conditions of fermentation were as follows:the concentration of initial sugar was 75 g/L,the inoculation quantity was 8%, the fermentation temperature was 34℃,reaction time was 84 h,and the concentration of ethanol could reach 4.362 g/L under the above conditions. Comparing the fermentation of rice straw acid-hydrolysis solution and glucose,the result showed that the rice straw acid-hydrolysis solution had low utilization ratio of reducing sugar,less decline of pH,and deficiency of posterior ability of fermentation.The possible reasons were that there were less fermentable sugars in rice straw acid-hydrolysis solution and the detoxification of it was incomplete.