Study On The Hydrolysis Of Cornstalk And Its Preparation Of Methyl Furan Series Liquid Fuel

With the exhausted of oil reserves, the great fluctuation of oil price, and the greenhouse effect with the consuming of oil–based fuels, so, it has become the hotspot research area in scientific and industry to find a new pathway for the synthesization of renewable woody biomass–based fuel to replace the oil–based energy and food starch–based energy, and it also is a focus problem for the sustainable development of society and caused an attention for the government and public.Woody biomass including straw, wheat straw, cornstalk, and other forest wood for energy, which was the most important renewable resource and composed of cellulose (β–1,4–glucose polymers), hemicelluloses and lignin, cellulose and hemicelluloses polysaccharides accounting for 70%~75% weight of the total woody biomass. It will be a great challenge for the conversion of these carbohydrate resources to high value chemicals and energies in the future era of none oil. At the present time, the majority studies were all focus on the production of ethanol from biomass and used as the liquid fuel. However, the conversion efficiency of ethanol from biomass is low, and one molecule of glucose only can be fermented into two molecules of ethanol or one molecule of butanol, and also generated two molecules of CO2, the theory efficiency to the target product only is 51.11% (ethanol) and 41.11% (butanol), the loss of carbon is 33.33%, furthermore, the oxygen ratio decreasement of the product only is 34.78% (ethanol) and 59.46% (butanol). In addition, the fermentation route from biomass–based sugar to ethanol is long, including the phosphorylation of glucose, the phosphorylation cleavage reaction of fructose, the phosphorylation of glyceraldehyde phosphate, the formation of phosphoric acid, the formation of pyruvate, the decarboxylation of acetone, acetyl coenzyme A reduction reaction, the acetaldehyde reduction, the citric acid cycle and so on; Moreover, ethanol can soluble in water, which caused the difficulty of extraction, separation and purification, and the energy consumption is high. Furthermore, the installation throughout the process is complex and will cause serious environmental pollution problems. Therefore, the industrial application prospect for ethanol derived from woody biomass is uncertain, which also shows that there has a highlighted urgency and critical importance to find a new path to get the high–quality liquid fuels from woody biomass.Biomass can be transformed into methyl furans (MFs). MFs including 2–methyl furan and 2,5–dimethyl furan, it has been used as solvent or polymeric materials previously, and have not been linked with fuel directly. In fact, MFs has a potential large–scale application as fuel. MFs has similar boiling point, higher octane number, and almost insolubleness in water when comparation with ethanol, So, it can be used as an excellent biomass–based fuel to make up for the deficiency of P series fuel, and reducing the dependent on oil, which has an important significance for the transition from non–renewable oil products to renewable biomass–based fuel and realization of the sustainable development for the fuel in our country. MFs also is an important platform chemical, which not only occupy a prominent position for the substitution of energy strategy, but also play an important role in chemical, pharmaceutical, chemical, biological, materials, and other industrial areas in the future. It will be the most important industrial source for liquid fuel through the conversion of woody biomass to product MFs for the long term.This project proposed a path to conversion of cornstalk to methyl furans (CCMF) based on our early studies and some other abroad researches, and including three main steps: the coupling hydrolysis of cornstalk to produce D–xylose and glucose; the catalytic dehydration of D–xylose and glucose to produce furfural and 5–hydroxymethylfurfural; the catalytic hydrogenolysis of furfural and 5–hydroxymethylfurfural to produce MFs (2–methyl furan and 2,5–dimethyl furan). It can be drawn from the comparison of CCMF approach and the approach for the fermentation of carbohydrates from lignocellulose to ethanol or butanol (FCLE or FCLB) that there has less steps for CCMF approach (only has 2~3 steps), and the theory efficiency to the target products is 54.67% (2–methyl furan) and 53.33% (2,5–dimethyl furan), which is higher than the approach of FCLE and FCLB. In particularly, the carbon loss is zero during the CCMF approach and the product yield for carbon is 100%. And also, the oxygen ratio of the product reduces significantly, which decreasing 63.42% (for 2–methyl furan) and 68.74% (for 2,5–dimethyl furan) respectively, indicating that the product has higher energy density for the less oxygen ratio. From the comparation it can be drawn that the energy carrier can be preserved fully for CCMF approach, and also, it has higher conversion efficiency and higher energy density for the unit molecule. During the coupling hydrolysis of cornstalk to produce D–xylose and glucose, the regulation mechanism and dynamics by low or ultra–low acid were studied, and the structure changes for cornstalk before and after the hydrolysis were analyzed by FTIR, XRD and SEM. Meanwhile, the enzyme hydrolysis for the cornstalk residual hydrolyzed with ultra–low acid was also studied in this paper.During the step of catalytic dehydration of D–xylose and glucose to furfural and 5–hydroxymethylfurfural, the catalytic dehydration mechanism of D–xylose was studied with MCM–41 molecular sieve catalyst. And also, a new type of solid acid, SO42–/ZrO2–TiO2, was prepared based on our previous study. The catalytic dehydration dynamic of D–xylose and the regulation mechanism of a mixture sugar which contains D–xylose and glucose were studied based on the SO42–/ZrO2–TiO2 catalysis. Moreover, the structure and character changes of the SO42–/ZrO2–TiO2 catalyst were analyzed by XRD, XPS, NH3–TPD and SEM.During the step of catalytic hydrogenolysis of furfural and 5–hydroxymethylfurfural into 2–methyl furan and 2,5–dimethyl furan, the catalytic hydrogenolysis regulation mechanism of furfural and 5–hydroxymethylfurfural was studied based on the Ruthenium carbon (Ru/C) catalysis, and the surface morphology changes of Ru/C catalyst before and after be used was analyzed by SEM. Meanwhile, the hydrogenolysis dynamic was studied based on the system pressure. And the reaction rate constants of the dynamic model were calculated through the calculation of minimum variance. The results have shown that it can be used as an intuitive parameter index for the guidance of experiment research or industrial production in macroscopic view based on the pressure of the reaction system, which has some theoretical value and certain realistic significance.Based on our study, the technology and technical route for the preparation of methyl furans derived from cornstalk has been formed, and pointed out there have existed some key technical bottleneck during the whole conversion chain, such as the higher energy consumption, the higher preparation cost of the solid acid and Ru/C catalysts, and the less cycle times of the catalyst, which are the key factors for the realizing of CCMF route.