Research On The Alcoholysis Of Cellulose To Ethyl Levulinate Catalyzed By Modified USY In Ethanol Medium

Ethyl levulinate(EL) is new energy and chemicals with high value-added. At present, proceed from biomass resources, according to different principles, synthesis pathway of alkyl levulinates mainly divided into three types: esterification of levulinic acid, direct alcoholysis of biomass, alcoholysis of 5-chlorine methyl furfural and alcoholysis of furfuryl alcohol. Among them, direct alcoholysis of biomass(also known as “one-pot method”) with low equipment requirement, simple process,products being easy to separate is very promising in biomass refining. molecular sieve has the advantages of high reaction activity, specific selectivity for products,strong resistance to carbon deposition. Besides, as one kind of solid acid catalysts in biochemical industry, it is also environmental benign, easy recovery and utilization repeatable. Thus, it attracts much attention in recent years.In this paper, the conversion of cellucose to EL catalyzed by modified USY was investigated. Firstly, alcoholysis of cellucose to EL was catalyzed by supported solid super acid; then, the alcoholysis of cellulose to EL using the modification USY zeolite treated with citric acid was explored; finally, the dealuminated USY supported copper was used to catalyze the conversion of cellulose to EL. The main conclusions are as follows:1. Different load quantity of SO2-4/Zr O2-USY were prepared by the precipitation impregnation method, then catalyzed the conversion of cellulose to synthetize EL.The result was that 10% SO2-4/Zr O2-USY showed the highest catalytic activity. The yield of EL reached 38.1 mol% at 200 ℃ for 3 h. The catalyst could be reused at least four times with higher catalytic activity. EL yields of 39.55 mol%,50.77 mol%,44.87 mol% and 43.59 mol% could be obtained from glucose, fructose, sucrose and inulin, respectively. In addition, the catalysts were characterized by XRD, FT-IR, BET,NH3-TPD, Py-IR, TG-DTA. The results showed that: 10% SO2-4/Zr O2-USY could maintain the characteristic peaks of USY. Although some pores had been blocked,strong acid sites appeared, which attributed to enhance the catalytic activity.Additionaly, the catalyst also had good hydrothermal stability.2. The dealumination modified USY were prepared by dealumination of USY molecular sieve in non buffer systems with different concentrations of citric acid. As for catalytic conversion of cellulose to EL, 0.2 mol/L citric acid solution showed the best modification. The effects of cellulose amount, DUSY amount, temperature and time were evaluated. The optimized conditions were: cellulose amount 0.6 g, DUSY amount 0.3 g, temperature 220 ℃, time 3 h. A verification experiment was performed and the productivity of ethyl levulinate was 36.1 mol%, which was almost the same as the model prediction. The solid acid over sieve catalyst could be reused for five times with higher catalytic activity. EL yields of 40.98 mol%, 50.07 mol%,47.62mol% and 42.9 mol% could be obtained from glucose, fructose, sucrose and inulin,respectively. The catalysts were further characterized by XRD, FT-IR, BET,NH3-TPD, Py-IR, TG-DTA. The results showed that the modification of USY molecular sieve with citric acid could enrich the porosity, enhance the Lewis acid site,and improve the catalytic activity. Besides, the catalyst also had better hydrothermal stability.3. Using citric acid dealumination modified USY as the carrier, the supported copper-based catalysts were made, among which 5% Cu-DUSY showed the best catalytic activity. The yield of EL reached 48.2 mol% at 200 ℃ for 3 h. The dealumination modified USY over sieve catalyst could be reused five times with slight decrease in catalytic activity. EL yields of40.40 mol%, 49.38 mol%, 44.91mol% and 44.60 mol% could be obtained from glucose, fructose, sucrose and inulin,respectively. In addition, the catalysts were characterized by XRD, FT-IR, BET,NH3-TPD, Py-IR, TG-DTA. The results showed that the catalyst after modification,had better thermal stability and could maintain the original crystal structure. Although the surface area of zeolite decreased, total acidity increased. Especially, the Lewis acid sites also increased, which contributed to improve the catalytic activity.