Fructose Dehydration Preparation Of 5 - (hydroxymethyl) Furfural

With declination of fossil resources and deterioration of environmental pollution resulted from them, seeking and utilizing renewable and degradable resources is an efficient method to solve fuel crises and environmental pollution. Biomass resource, as a renewable and sustainable resource industry, which attracts more and more attention because of extensive distribution in nature and good ecological benefits, so it is expected to a fine substitute for liquid fossil fuel and chemical intermediates. Moreover, in light of scientific, efficient, green and low carbon strategy of energy development, vigorously developing and utilizing renewable energy is a development tendency of energy market in our country.5-hydroxymethylfurfural (HMF) is a versatile platform compound, which is usually synthesized through acid-catalyzed dehydration of glucose, fructose, sucrose, cellulose and among other biomass resources. HMF can derive and synthesize numerous chemicals, including pharmaceutical, pesticide, spices, resin plastic and additives of diesel fuel. So HMF is considered as a bridge between biomass resources and petrochemical.This thesis mainly studied dehydration reaction of fructose to HMF in organic solvents, and investigated dehydration of fructose to HMF by homogeneous Lewis acid catalyst rare earth metal trifluoromethanesulfonates and heterogeneous solid acid catalyst Nb2O5. Using aprotic DMSO as reaction solvent, for it efficiently inhibits formation of byproducts such as levulinic acid and formic acid, and reduces the formation of soluble polymers and humin matter, dramatically increasing the yield of HMF. The main contents in this work are as follows:(1) Dehydration of fructose to HMF by various rare earth metal trifluoromethanesulfonates, that is, Yb(OTf)3, Sc(OTf)3, Ho(OTf)3, Sm(OTf)3, Nd(OTf)3 as catalysts are investigated. The results show the catalytic activity of catalyst increases with decreasing cation ionic radius of the rare earth, because Sc3+has smaller ionic radius, it exhibits higher catalytic activity in the reaction, and then selecting Sc(OTf)3 as catalyst, studying the influences of various reaction factors including reaction solvents, reaction temperature, reaction time, fructose concentration, catalyst dosage on the yield of HMF. The optimum reaction condition is drawn as follows:40 mg fructose, DMSO 2.0 g, fructose/ Sc(OTf)3 (w/w)=10:1,120℃,2 h, a fructose conversion of 100% and HMF yield of 83.3% are obtained.(2) Nb2O5 are prepared from Niobic acid (Nb2O5·nH2O) calcined under various temperatures (300～700℃), and the catalysts are characterized by XRD, BET, NH3-TPD and FTIR of adsorbed pyridine. The catalytic activities of Nb2O5 calcined under various temperatures in the dehydration reaction of fructose to HMF are studied. The experiment results show the niobic acid calcined under 400℃exhibits the higher catalytic activity among all the catalysts. In addition, the influences of various reaction factors on the dehydration of fructose to HMF are investigated, and it is found that under the reaction condition of a fructose concentration of 2 wt%, fructose/catalyst (w/w)=10:1, reaction temperature of 120℃for 2 h, the fructose is converted completely, and a maximum yield HMF of 86.2% is obtained. The Nb2O5 solid acid catalyst can be recycled at least five times without severe loss of catalytic activity.