New solid superacid catalysts for n-butane isomerization:#gamma#-Al-2O_3 or SiO_2 supported sulfated sulfated zirconia

摘要

Solid superacid catalysts SO_4~(2-)/ZrO-2(SZ)supported on #gamma#-Al_2O_3 and SiO_2(named SZ/Al_2O_3 and SZ/SiO_2,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/Al_2O_3 catalysts. In the flow system,the steady acivity of the most active sample, 60% SZ/Al_2O_3,is 2.5 times more active than that of the bulk SZ.However, the activities of the SZ/SiO_2 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 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/Al_2O_3 sample are higher than those on bulk SZ,while the amount of acid sites is lower on 60% SZ/SiO_2. The different activities for the SZ/Al_2O_3 catalysts and the SZ/SiO_2 catalysts are due to the differences of superacidity.