| In this paper, the SO3/ClO2 and SO3/HCl methods that have better pretreatment effect were studied on the basis of the SO3 micro-thermal explosion collaborative dilute alkali treatment method. The main conditions of the two methods were optimized, and the mechanism of two joint pretreatment methods were explored preliminary through analysis of FI-TR, SEM and XPS. On this basis, a new method that HCl in-situ saccharification hydrolysis was invented, the main factors that affecting the process were investigated and the HCl treatment process was tracked. Finally, the washing water was used for ethanol production by Angel Yeast fermentation. The main contents of the study were as follows. 1. On the basis of SO3 micro-thermal explosion, the pretreatment effect of SO3 joint four oxidants (NaClO2, NaClO, H2O2, ClO2) were investigated, the result showed that the treatment effect of SO3 micro heat explosion combined ClO2 oxidation solution was best, and the major pretreatment technological conditions were optimized according to the content of main components and the corresponding characterization after treating, the best process route were as follows:1.0% of ClO2 concentration,1:20 of the rice straw and ClO2 solution ratio,3 of ClO2 solution pH,60 ℃ of treatment temperature, 60 min of treatment time, and the cellulose content reached 64.4%, the residual lignin reached 5.3% after treatment.2. The mechanism of SO3/ClO2 joint dilute alkali pretreatment of rice straw was studied preliminary through FI-TR, SEM analysis methods, the results showed that firstly, the SO3 entered into the straw, combined water in the straw to form sulfuric acid, on the one hand sulfate esterification reaction occurred between lignin and sulfuric acid, on the other, the heat generated in the process could burst straw. Secondly, ClO2 solution accessed to the inside of straw more fully, and could oxidize lignin quickly, while the sulfuric acid ester base were not affected during the process, so that the lignin could be peeled sufficiently by the dilute alkali treating subsequently, while these two processes did not react with the holocellulose inside, thus preserving the cellulose and hemicellulose to the maximum extent.3. On the basis of the ClO2 solution, four pretreatment methods of HCl, SO3, SO3/ HCl and HCl/SO3 joint dilute alkali pretreatment were compared and investigated, and pretreatment effects of rice straw first treated by the SO3 micro heat explosion, then HCl treatment, and combined with dilute alkali pretreated was the best. The major pretreatment technological conditions were optimized according to the main ingredients and the corresponding characterization, the best the process route:1.5% of SO3 amount, 50 ℃of SO3 treatment temperature,60 min of SO3 processing time,0.8% of HCl amount,70 ℃of HCl treatment temperature,60 min of HCl treatment time,6.0% of straw moisture content, after treatment, the amount of residual lignin was 6.3%, cellulose content was 61.3%.4. The mechanism of SO3/HCl joint dilute alkali pretreatment of rice straw were studied through analysis of FI-TR, SEM, XPS, the results showed that during the process, firstly, SO3 entered into the straw and combined with water inside the straw to form sulfuric acid, large amounts of heat produced during the process could destroy the structure of the straw, then treated with HCl, HCl could entered into the interior of the straw more completely, although the reaction did not occur with the straw components, but it could cleaves internal linkages between hemicellulose and lignin, and the formation of HCl acid hydrolysis was less due to the fact that SO3 capable of binding the water in the straw, after the combined pretreatment, lignin in the straw could be better removed.5. HCl in-situ saccharification hydrolysis of rice straw was studied, the optimum saccharification hydrolysis conditions for growth and fermentation of microorganism were obtained according to the content of sugar and furfural in the wash water, that were 3% of HCl concentration,100% of placement humidity,60 ℃ of placement temperature, while during the in-situ saccharification process, HCl hydrolysis was tracked by SEM, HPLC for the investigation of cross-sectional shape of the treated rice straw, molecular weight and sugar types of substances in the water, the result showed that in the beginning the wash water was xylose-based mainly, other carbohydrate concentration increasing while the molecular weight of substances decreasing with the time prolonging, indicating that cellulose and hemicellulose could be gradually hydrolyzed to small molecules sugars in the process which could be used by ethanol fermentation of Angel Yeast, when the fermentation time was 16d, the ethanol content could reach 37.8g/L. |
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