新型吗啉基离子液体中碳水化合物高效转化为5-羟甲基糠醛

Abstract

The diminishing of fossil fuel reserves has driven people to search sustainable and alternative energy. Recently, much attention has been paid to the conversion of biomass for a sustainable supply of liquid fuels and valuable chemicals. Carbohydrates are an important type of biomass and can be transformed into many value-added chemicals and fuels. Among various chemicals obtained from carbohydrates, 5-hydroxymethylfurfural (HMF) derived from dehydration of carbohydrates is a promising platform molecule. Production of HMF from glucose is very attractive because it can be easily obtained from the hydrolysis of cellulose. Up to now, many efforts have been devoted for the HMF production from dehydration of glucose and various catalysts have been developed, including various Lewis acids, tantalum compounds, boric acid, ion exchange resins, ionic liquids (ILs), Sn-Mont catalyst, etc. Although these catalysts were effective, exploration of efficient and cheap catalytic systems to enhance the efficiency of the reaction is still very attractive and challenging. In the dehydration of glucose, solvents have important effect on the activity and selectivity for the formation of HMF. The dehydration of glucose could be conducted in various solvents, including traditional organic solvents, water, multiphase systems and ILs. Among these solvents, ILs are among the most attractive ones for dehydration of glucose to produce HMF because of their unusual properties. Up to now, several types of ILs have been successfully used as the reaction solvents for HMF production from glucose. However, it is still highly attractive and desirable to develop new and easily prepared ILs as efficient solvents for the dehydration of carbohydrates. In this work, several new morpholine-based ILs with benzene sulfonate (BS) anion were synthesized and used as the solvents for the conversion of carbohydrates into HMF. It was demonstrated that all of the as-prepared ILs were efficient solvents for the dehydration of glucose, fructose, sucrose, inulin, and cellobiose using SnCl4 as the catalyst. The effects of temperature, reaction time and catalyst amount on the dehydration of glucose in SnCl4/[Et-MMP]BS were studied systematically. It was shown that the yield of HMF could reach up to 67.6% from glucose under the optimized reaction conditions. In addition, the SnCl4/[Et-MMP]BS system could be easily separated from the product, and could be reused at least five times without considerably decreasing activity.