Study On Acid-hydrolysis Of Lignocelluloses

With social and economic development, the demand of energy sources grows day and day, limitation and unrenewable of petrochemical and coal resources, these problems must cause lead to insufficient supply. The plant contains abundant cellulose and hemicelluloses, only a little is utilized. With demand of fuel ethanol increasing, a large amount of grain as raw material for fuel ethanol production, lead to strained relationship of supply and demand about grain problem. According to our national conditions, studying and exploitating cellulose resource have important sense. This thesis unfolds around lignocelluloses pretreatment and acid-hydrolysis.Firstly, effect of hydrogen peroxide treatment, ammonia treatment, alkaline treatment to component content and infrared structure and N-O'KI are compared .1) Hydrogen peroxide treatment: the loss rate of cellulose and hemicellulose are increased with concentration increasing, delignification rate exists maximum when concentration is 3%, it is about 39%. The loss rate of cellulose and hemicellulose are increased with time increasing, delignification rate tends to be steady when after 2.5h. 2) Ammonia treatment: delignification rate are increased with ammonia concentration increasing. The loss rate of cellulose exists maximum when concentration is 10%, it is about 6%. 3) Alkaline treatment: the loss rate of cellulose tends to be steady when concentration is above 3%, it is about 4%. Delignification rate and the loss rate of hemicellulose are increased with concentration increasing. Delignification rate and the loss rate of cellulose and hemicellulose are increased with temperature increasing. 4) Comprehensive comparison: the loss rate of cellulose is the highest by hydrogen peroxide treatment, it is above 10%, and the other pretreatment is less than 10%. the loss rate of cellulose is the highest by hydrogen peroxide treatment, it is above 30%, and ammonia pretreatment and alkaline treatment are less, they are one third and one second of hydrogen peroxide respectively. The delignification rate is the highest of all, it is about 50%. The N-O'KI is the highest by alkaline treatment, it is 1.4365, and the increase amplitude is 36% relative to the N-O'KI of untreatment.Secondly, with alkaline treatment presulfided rice stalk powder taking for raw material, study effect of sulfuric acid hydrolysis conditions on hemicellulose hydrolysis rate, xylose yield and cellulose mass loss rate by single factor and orthogonal experiment, the results show that , different importance factors influence of hemicellulose hydrolysis rate: temperature > acid concentration > liquid-solid ratio (mL/g) > time, different importance factors influence of xylose yield: temperature > acid concentration > time> liquid-solid ratio (mL/g), and different importance factors influence of cellulose mass loss rate: acid concentration > liquid-solid ratio> time> temperature. Comprehensive analysis of xylose yield and cellulose mass loss rate during experimental range, hydrolysis process conditions of hemicelluloses is: acid concentration for 1.8%, temperature at 122℃, time in 60min, liquid-solid ratio (mL/g) for14:1. The xylose and glucose are more in hydrolysate.Thirdly, raw material from inorganic acid hydrolytic residues, study effect of citric acid hydrolysis conditions on the cellulose hydrolysis rate and the reduction glucose yield by single factor and orthogonal experiment, the results show that different importance factors influence of cellulose hydrolysis rate: acid concentration > temperature > time> liquid-solid ratio (mL/g), and different importance factors influence of glucose yield: temperature > acid concentration >liquid-solid ratio> time. The optimum condition of glucose yield index is: citric acid concentration for 2.9%, temperature at 190℃, time in 70min, liquid-solid ratio (mL/g) for15:1. The glucose and polydextrose are more in hydrolysate.Finally, study effect of seven resins static adsorption and separation sugar-acid, the results show that influence of resin structure is: vinylpyridines series>epoxy series>acrylic acid series>styrene series. The elution amount and elution rate have no relation with resin structure and exchange capacity. The dissociation constant (pKb value) have no effect on static adsorption amount and elution amount and elution rate.