Studies On Hydrolysis Of Rice Straw And Catalytic Performances Of Residue Char Sulfonic Acid

Rice straw is an important biomass, with wide distribution and enormous amount. The bioconversion of rice straw to fuel alcohol through saccharification and fermentation processes is an effective approach to exploit the resources. With the development of catalytic science and the increase of the environment conception, it's more meaningful to develop a reusable, easy separation and low-cost solid acid from renewable raw materials by an environmental friendly method. As a matter of fact, the application of solid acid has been attracted much attentions recently years. In this dissertation, a new kind of inexpensive solid sulfonic acid material which is made from the residues resulting from hydrolyzate of rice straw. Thus, with the help of the method, the full utilization of biomass resources will be effectively realized. The main contents discussed were as follows:(1) The acid hydrolysis process of rice straw was studied under microwaves irradiation. The effects of microwave power, irradiation time, mass fraction of sulfuric acid and solid-liquid ratio on acid hydrolysis process were investigated. Compared with conventional acid hydrolysis, microwave radiation can significantly speed up the rate of hydrolysis and shorten the time of saccharification. By means of orthogonal experiment, the conditions for acid hydrolysis process of rice straw under microwaves irradiation were optimized as follows:microwave power 280 W, irradiation time 30 min, sulfuric acid mass fraction 25%, rice straw amount 30 g/L, and the reducing sugars yield reached to 26.45%.(2) In this paper, utilizing the residues resulting from sulfuric acid hydrolysis of rice straw as raw material, a novel solid sulfonic acid catalyst have been produced after the following production process:decompression carbonizing and sulfonating by oleum. Furthermore, the acid amount of char sulfonic acid influenced by the charring temperature, the charring time and heating rate of carbonization were studied in details. It was found out that the acid amount of sulfonic acid can reach up to 2.418 mmol/g under the optimized conditions. In addition, Some physical properties and structure characterization of the catalysts were characterized with XRD, FT-IR and TG-DTG. The results showed that the obtained char materials have polycyclic aromatic rings with a number of oxygen-groups and the prepared solid sulfonic acid catalyst showed an obvious C-S absorption peak in FT-IR spectrum. At the same time, this catalyst has good thermal stability of which sulfonic acid groups lost weight at 200℃.(3) This work focuses on the catalytic performance of self-condensation of cyclohexanone. On the basis of factors analysis, the optimal operation variables were described through a series of experiment:when catalyst capacity was 1.5 mol%, the cyclohexanone was 30 mmol at 105℃for 3 h, the conversion of cyclohexanone came up to 84.1% and the selectivity toward the desired product was also above 84.9%.(4) The residue char sulfonic acid had shown excellent catalytic activities in condensation reaction of glycerol with cyclohexanone. The factors influencing the yield are discussed and. the best conditions are found out by test. The optimum conditions are as follows:the cyclohexanone was 0.10 mol, glycerol was 0.12 mol, catalyst capacity was 10 mg, water-carrying agent of cyclohexane was 15 mL, the reaction time of 2.5 h, the conversion of cyclohexanone can reach 99.3%. Furthermore, The residue char sulfonic acid could be conveniently recovered for recycled use without significant loss of catalytic activity and selectivity.