Catalytic Process And Mechanism Analysis In Biomass Liquefaction

Catalytic liquefaction of biomass, which has been considered as one of the most efficient ways for biomass utilization, can be regarded as a process for the thermochemical conversion of biomass into liquid fuel in the presence of solvent and catalyst. The rational use of biomass resources can not only improve the energy structure, but also ease the energy crisis and environmental pollution problems. Moreover, it is very significant for promoting the energy conservation and sustainable development of our society; and it can also afford the very important security to our country in terms of energy, resource, and society.In this dissertation, the selective catalytic liquefaction of biomass into biofuel and platform chemicals including the distribution of products has been investigated intensively. And, based on the distribution of products, the catalytic process and corresponding possible liquefaction mechanism has also been studied in depth. The detailed works are listed as follows:(1) A catalytic system with Na2CO3 catalyst in the hot compressed water has been constructed for liquefaction of cellulose. After analyzing the catalytic processes in depth through doing multi-factors orthogonal tests, it has been found that the optimum conditions consist of 5 g of celluose, 0.15 g of Na2CO3 catalyst, 300 oC of reaction temperature, 30 min of reaction time, and 10:1 of liquid mass ratio. And, at the conditions, the liquefaction of cellulose into biofuel can be realized with more than 90% liquefaction ratio. Furthermore, it has been found that the plaform chemicals in liquefaction products are furfuraldehyde, lactic acid, cyclopentenone and its derivative, and other organic compounds such as phenols, alcohols, and ethers after further analysis of the distribution of products in depth.(2) The perovskite La NiO3 used as the catalyst for liquefaction of bagasse has been investigated intensively. After analyzing the effect of reaction temperature and reaction time on liquefaction of bagasse and the distribution of products in depth, it has been found that the higher reaction temperature and longer reaction time are benefit for producing small molecule compounds. Furthermore, after optimzing the reaction conditions through multi-factors orthogonal tests, the optimal parameters for the liquefaction process are 1.0 g of catalyst, 15:1 of liquid mass ratio at 350 oC reaction temperature and 30 min of reaction time.(3) The possible promotion effect and mechanism of halogen-containing reagent for dehydration of fructose into 5-hydroxymethylfurfural have been investitaged systemically. The results showed that the chloralkane is benefit for conversion of fructose into 5-hydroxymethylfurfural due to the fact that the functional group of-Cl can efficiently decrease the activation energy for the conversion of fructose into 5-hydroxymethylfurfural, resulting in the dehydration of fructose to 5-hydroxymethylfurfural easily at the lower temperature. The foundings of the promotion effect of-Cl group enlarges the scope in utilization of fructosebased carbohydrate.(4) A biphasic system with dihydric phosphate catalyst for dehydration of glucose into 5-hydroxymethylfurfural has been constructed. The process parameters such as the dosage of catalyst, reaction temperautre, reaction time, and the concentraction of substrate have been investigated systemically. The results showed that, the suitable catalyst dosage and substrate concentration is 40% and 45%, resprectively. And, the optimum reaction temperature is 160 oC with the optimized reaction time of 2 h. Under this optimized conditions, the yield of 5-hydroxymethylfurfural can reach up to 52.3%. This biphasic catalytic system is also substratetolerant, and with the sucrose and maltose as the feedstocks, more than 40% of the yield of 5-hydroxymethylfurfural can still be reached. Furthermore, this system is also recyclable, and there is no catalytic activity loss can be found even though after the 9th cycle. At the same time, the possible function of dihydrogen phosphate for dehydration of glucose into 5-hydroxymethylfurfural has also been investigated in depth. The possible catalytic mechanism of dihydrogen phosphate has been proposed as follows:(I) the isomerization of glucose to fructose;(II) subsequent conversion of fructose into 5-hydroxymethylfurfural;(III) as an additive to improve the extraction ratio of extractive solvent for target product(may be the salting out effect). Hence, the application of dihydrogen phosphate catalyst system can provide an important route for catalytic conversion of glucose to 5-hydroxymethylfurfural, and can also act as a important reference for biomass utilization in the future.Therefore, the as-constructed catalytic systems for liquefaction of biomass into biofuel and platform chemicals in the dissertation can act as a guide for utilization of biomass resource, and can also afford the desired pathway for the production of platform chemicals from original biomass.