Study On Esterification Reaction Catalyzed By Modified Bentonite

Bentonite(Bent) is the main component of montmorillonite, for its special structure, unique chemical composition, larger specific surface area and high thermal stability. It have larger specific surface area and higher thermal stability for specific structure and chemical composition. It needs to remove impurities of natural bentonite with high content of montmorillonite, and then obtained different types of solid catalysts through loading and so on. Compared with the traditional liquid phase catalytic, bentonite as the carrier of catalyst has low cost, high catalytic activity, easy separation and can be recycled many times. At the same time is a green catalyst and it has wide application prospect. The article uses purified bentonite as the carrier, after acidification the catalysts were load phosphotungstic acid, titanium crosslinking and hydroxy aluminium iron column. The obtained supported catalysts were charactered by fourier transforminfrared absorption spectra(FTIR), thermal analyzer(TG) and X-ray diffraction(XRD), scanning electron microscope(SEM), surface analysis(BET), then studied its catalytic properties in esterification reaction. The works are listed as following:1. To purify acidic bentonite as the carrier, Ti(n-C4H9O) 4 as titanium source, using the sol-gel method to titanium dioxide and montmorillonite crosslinking, the specific surface area of 243.3094 m2.g-1, total pore volume of 0.20296 cm3.g-1, and the thermal stability of high(640℃ structure does not change), titanium crosslinked catalyst(Ti-PILC). At the same time, the catalyst of γ-benzyl ester of L-glutamic acid yield were studied. The results show that the Ti-PILC has a relatively good catalytic performance in esterification. The L-glutamic acid/benzyl alcohol molar ratio is 1:6, the reaction temperature is 60℃, the reaction time is 2 h, the total mass of the catalyst 8% of the raw material, γ-benzyl ester of L-glutamic acid yield achieved 77.9%. The method provides a reference for application in the field of solid acid catalyst.2. The bentonite(Bent) was treated by acidification and then heteropoly acid(HPW) was supported to the acidified bentonite(AAB) using the method of saturation impregnation. In this study, low-cost carrier bentonite is used as efficient catalytic on synthesis of methyl palmitate, which is an alternative to bio-diesel oil. The results show that the HPW/AABA has the optimal catalytic properties on the esterification reaction with the conditions of reaction temperature 65℃, molar ration of methanol to palmitic 25:1, reaction time 6h and loading of catalysts 20%, and the esterification rate is 87.2%. The catalytic efficiency of six times after repeated is remained 95%.3. The chapter used hydroxy Fe-Al pillared bentonite, and the impact of different conditions on the pillared montmorillonite was investigated. Fe-Al-pillared montmorillonite calcined at 500 ℃ has excellent stability. However, when the temperature is higher than 500℃, the peak d001 become weaker, IR spectra shows some peaks disappear. The results showed that at temperature of 80℃, calcination temperature of 500℃, the total mass of the catalyst 1.5% of the raw material, reaction time of 8 h, the reaction molar ratio of 9:1, the Yield of oleate is maximum 86.7%. The method is simple and easy to get and the raw material is also low.