New solid superacid catalysts for n-butane isomerization: gamma-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 impregnatio n method. Their catalytic behaviors of for n-butane isomerization at low te mperature in steady state system and at high temperature in flow system wer e studied. Large improvements of catalytic activities were observed on the SZ/Al2O3 catalysts. In the flow system, the steady activity of the most act ive 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 h ulk 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 a nalysis 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 S Z, while the amount of acid sites is lower on 60% SZ/SiO2. The different ac tivities for the SZ/Al2O3 catalysts and the eSZ/SiO2 catalysts are due to t he differences of superacidity. (C) 2000 Elsevier Science B.V. All rights r eserved.