Study On The Preparation And Catalytic Properties Of Mesoporous Zirconia-based Solid Superacids

Zirconia-based solid superacids possess of many excellences, including its strong acidity, good activity, high selectivity, easily separation from products, no corrosion to equipment, small environmental pollution, good reusability. It is a kind of green, efficient, safe environmental protection new type catalyst. However, the further industrial application of SO₄^2-/ZrO₂ solid superacids is limited, because of existing some defects, such as poorer stability, easily loss of surface active components and pooper reusability. In this paper, the preparation methods of the mesoporous WO3-CeO₂-ZrO₂ solid superacid and the mesoporous SO₄^2-/CeO₂-ZrO₂ solid superacid were studied. Using the esterification of acetic acid with n-butanol as a probe reaction, the catalysts activity were investigated. The phase composition, structure, acid strength and acid amount of the as-prepared catalysts were characterized by X-ray diffraction, Raman spectroscopy, FT-IR, N2 adsorption-desorption, TEM and NH3-TPD. The reusability and regenaration of the as-prepared catalysts were studied. The application research of as-prepared catalysts in catalyzing the syntheses of ester such lactic acid butyl ester and tributyl citrate ester were carried out, too. The main results are as follows:（1） The mesoporous WCZ obtained by optimum condition owned superacidity, phase composition of the as-prepared catalysts possessed of single tetragonal zirconia, its specific surface area, average pore size, pore volume and acetic acid conversion ratio of the catalysts were 176.1 m²/g,3.70 nm,0.20cm³/g,97.28%, respectively. Doping appropriate amounts of rare earth Ce helps to stabilize tetragonal ZrO₂, The stability of catalyst were improved effectively by adding appropriate amounts of WO3 as an active component. The acid strength and acid amount of catalyst were improved significantly by doping appropriate amounts of rare earth Ce, adding appropriate amounts of WO3 and introducing mesoporous structure, so that the acitivity, reusability and stability of zirconia-based solid superacids could improve significantly.（2） The mesoporous SCZ obtained by optimum condition had superacid structure, phase composition of the as-prepared catalysts were composed of single tetragonal zirconia, its specific surface area, average pore size, pore volume and acetic acid conversion ratio of the catalyst were 185.5 m²/g,3.63 nm,0.23 cm³/g,98.86%, respectively. The acid strength and acid amount could be improved observably by doping appropriate amounts of rare earth Ce and introducing mesoporous structure, so that the acitivity, reusability and stability of zirconia-based solid superacids could improve significantly.（3） The as-prepared solid superacids had excellent selectivity, good reusability and regeneration ability. The performance of as-prepared catalysts was good in catalyzing the syntheses of lactic acid butyl ester and tributyl citrate ester.