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

Solid superacid catalysts SO42-/ZrO2 (SZ) supported on gamma-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 hulk SZ. However, the activities of the SZ/SiO2 catalysts are lower than that of hulk SZ. The texture properties of the catalysts were studied by the methods of XRD and the adsorption of N-2. 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 eSZ/SiO2 catalysts are due to the differences of superacidity. (C) 2000 Elsevier Science B.V. All rights reserved.