New solid superacid catalysts for n-butane isomerization: γ-Al2O3 or SiO2 supported sulfated zirconia Original Research Article

Solid superacid catalysts SO42−/ZrO2 (SZ) supported on γ-Al2O3 and SiO2 (named SZ/Al2O3 and SZ/SiO2, respectively) were prepared by an impregnation method. Their catalytic behaviors of for n-butane isomerization at low temperature in steady state system and at high temperature in flow system were studied. Large improvements of catalytic activities were observed on the SZ/Al2O3 catalysts. In the flow system, the steady activity of the most active sample, 60% SZ/Al2O3, is 2.5 times more active than that of the bulk SZ. However, the activities of the SZ/SiO2 catalysts are lower than that of bulk SZ. The texture properties of the catalysts were studied by the methods of XRD and the adsorption of N2. Experimental results of sulfur content analysis and IR of adsorbed pyridine show that the acid strength and amount of strong acid sites on 60% SZ/Al2O3 sample are higher than those on bulk SZ, while the amount of acid sites is lower on 60% SZ/SiO2. The different activities for the SZ/Al2O3 catalysts and the SZ/SiO2 catalysts are due to the differences of superacidity.