Research On Ultrasonic Enhance Aqueous Ammonia And Supercritical Carbon Dioxide Pretreatment Of Lignocellulose

This paper studied lignocellulose pretreatment with ultrasonic enhanced, the research mainly focused on using corn cob, corn stalk and sorghum stalk as raw materials, and lignocellulose pretreatment with ultrasound enhanced aqueous ammonia, discusses the effects of relatively high mass concentration and low mass concentration aqueous ammonia on pretreatment; At the same time, lignocellulose pretreatment with scCO2 under low temperature and ultrasonic enhanced was studied, the effects of different factors on the pretreatment were investigated. The reducing sugar yield of pretreated samples which hydrolyzed by enzyme were analyzed and calculated, and evaluate the effect of pretreatment. Finally clarify the mechanism of pretreatment and the microstructure changes of the samples by means of XRD and SEM. The results are as follows:1.Using ultrasound enhanced aqueous ammonia pretreatment corn, sorghum and corn stalks raw materials, under the condition of 7.50?17.5wt% of aqueous ammonia, discussed the effects of the pretreatment temperature, time, substrate concentration and aqueous ammonia mass concentration on the reducing sugar yield after hydrolyzed by enzyme. We obtained the optimum pretreatment conditions and the yield of reducing sugar in different materials. Pretreatment with relative high mass concentration of aqueous ammonia and ultrasonic enhanced, the reducing sugar yields under the optimal conditions of different materials are as follows, corn cob was 40.5%, sorghum stalk was 47.1%, corn straw was 44.1%, compared with enzymatic hydrolysis of raw materials, the reducing sugar yield were increased by 25.7%,25.7%,30.8%.2.Using ultrasound enhanced aqueous ammonia pretreatment corn cob, sorghum and corn stalks raw materials, under the condition of 1?4wt% of aqueous ammonia, discussed the effects of the pretreatment temperature, time and substrate concentration on the reducing sugar yield after hydrolyzed by enzyme. We obtained the optimum pretreatment conditions and the yield of reducing sugar in different materials. Pretreatment with relative low mass concentration of aqueous ammonia and ultrasonic enhanced, the reducing sugar yields under the optimal conditions of different materials are as follows, corn cob was 36.5%, sorghum stalk was 33.2%, corn straw was 31.1%, compared with enzymatic hydrolysis of raw materials, the reducing sugar yield were increased by 21.3%,16.9%,12.7%.3.Corn straw and corn cob raw material pretreatment with ScCO2 under low temperature and ultrasonic enhanced, and evaluate the effect of pretreatment by the reducing sugar yield after hydrolyzed by enzyme, discussed the effects of the pretreatment pressure, time, temperature and ultrasonic time on the reducing sugar yield after hydrolyzed by enzyme. The reducing sugar yield of Corn straw pretreatment with scCO2 under low temperature and ultrasonic enhanced under optimal conditions was 40.3%, the ratio was increased by 21.9% compared with that without pretreatment. The reducing sugar yield of Corn cob pretreatment with ScCO2 under low temperature and ultrasonic enhanced under optimal conditions was33.0%.4.Explored the mechanism and the microstructure changes of corn, sorghum, corn stalks and other raw materials pretreatment with ultrasound enhanced aqueous ammonia and corn stalks pretreatment with ultrasonic enhanced scCO2 under low temperature by means of XRD and SEM characterization technique and the standard paradigm washing. The results show that the relative content of cellulose and relative crystallinity were enhanced after the material pretreatment, from SEM images, it can be seen after pretreatment there are holes and cracks generated in the lignocellulose, and the structures have different degrees of destruction, which is conducive to expose more cellulose, so that the accessibility to the cellulase could be further increased. Finally the reducing sugar yields obtained by enzyme hydrolysis will be increased.