| Energy is the driving force of economic and social development. Today, energy is short of all over the world. Fuel ethanol is a clean energy known of not increasing carbon emissions, inexhaustible, renewable and has become a strategic research project put forward by developed and developing countries. Development of fuel ethanol has two difficulties:(1) the raw material pretreatment and saccharification issues; (2) cofermentation of hexose and pentose problem. The work carried out around these two issues, our aim is to find and established a number of new methods and theory to solve these problems.For shortage of grain ethanol feedstock, this work studied the feasibility of using agriculture and forestry cellulose waste and municipal solid waste as raw materials for fuel ethanol production. The result showed that straw and municipal solid waste can be used as fuel ethanol raw materials. Modern city garbage classification collection methods greatly reduces the cost of sorting the garbage. Kitchen waste contains about 50% of the starch material, and ethanol fuel can be obtained after saccharification with glucoamylase and fermentation, and the process is similar to food ethanol production. Cellulose and hemicellulose in waste paper is about 80%, and the hydrolysis, saccharification and fermentation process of wastepaper is quite similar to agriculture and forestry cellulose waste.To solve the problem of raw material pretreatment and saccharification, the study proposed some new pretreatment methods based on the existing acid pretreatment method, which are super-concentrated acid pretreatment method, microwave combined acid pretreatment method and aqueous ionic liquid pretreatment method, and saccharification mechanism and the specific process were discussed. The results showed that total reduced sugar yield of straw was 28.7%, which pretreated by super-concentrated hydrochloric acid as the solvent at room temperature, and digestion rate of the straw is nearly 100%. The total reduced sugar yield of. waste paper heated by microwave in acid increased about 20%, compared to that of waste paper heated in conventional ways, and 88 times the rate of waste paper soaking in deionized water heated under microwave radiation (TRS was only 0.15% pretreated for 40 min). The total reduced sugar yield of kitchen wastes heated by microwave in acid increased about 46.1%, compared to that of kitchen wastes without pretreatment. The results indicated that the microwave radiation combined with acid pretreatment way can effectively promote hydrolysis saccharification process and improve sugar yield. A new method of using aqueous ionic liquid to hydrolyze lignocellulose was put forward. The experimental results show that the reduced sugar yield was 93.69% with the concentration of 25% aqueous ionic liquid solution to pretreat straw, which was better than that of dilute acid solution to pretreat straw (the reducing sugar yield was 26.97%); Further studies showed that hydrolysis activation energy of straw was different in different solvent, which were 157 KJ/mol in dilute acid,116 KJ/mol in super-concentrated hydrochloric acid,107 KJ/mol in ionic liquid and 43 KJ/mol in aqueous ionic liquid, demonstrating that aqueous ionic liquid solvent was more conducive to the straw hydrolysis reaction, and ionic liquid could be used repeatedly and the straw hydrolysis saccharification effect is stable, which showed that ionic liquid was ecomomical. At the same time, the dosage of ionic liquid is reduced using aqueous ionic liquid in pretreatment of straw, and no need to remove water in the process of ionic liquid recycle, which was operation and energy saving and cost reducing.To solve the fermentation inhibition of pentose to hexose, fermentation process with immobilized Saccharomyces cerevisiae and Pachysolen tannophilus was put forward. Static fermentation of hydrolysate from waste straw and municipal solid waste was carried out, and the results showed that the effect of immobilized bacteria on the fermentation of hydrolyzate was significantly better than that of the free ones, and the yield of ethanol is increased by 38.1% than the free strain condition. At the same time, non-isothermal dynamic fermentation way as a new fermentation solution was put forward to improve ethanol production. According to microbial growth and product synthesis temperature is not consistent, in the process of fermentation temperature was changed to ensure the stability of bacterial growth and maximum increase production of ethanol, and the effect of fermentation was well improved, the ethanol concentration was 7.1%, which was increased by 18.3% compared with the static temperature fermentation.Finally zeolite was innovatively used as the medium to separate glucose and ionic liquid mixed system. The results showed that the glucose was adsorbed by zeolite to a certain degree, ionic liquids was almost didn’t adsorbed by zeolite, and the adsorption percentage of glucose from zeolite was up to 99.83%. Therefore, glucose and ionic liquid can be effectively separated on the zeolite media, and the separation rate was up to 68.25%. |
PDF Full Text Request