Hydroisomerization of Benzene-Containing Gasoline Fractions on a Pt/ SO_4~(2-) —ZrO_2-Al_2O_3 Catalyst: I. Effect of Chemical Composition on the Phase State and Texture Characteristics of SO_4~(2-) —ZrO_2-Al_2O_3 Supports

摘要

A series of SO_4~(2-)-ZrO_2-Al_2O_3 oxide supports containing from 18.8 to 89.1 wt % alumina was prepared by mixing sulfated zirconia hydrate (weight ratio ZrO_2 : H_2SO_4 = 9 : 1) and pseudoboehmite followed by calcination at 650℃. For the subsequent use of the supports to optimize the acid and hydrogenating properties of bifunctional hydroisomerization catalysts of the Pt/SO_4~(2-)-ZrO_2-Al_2O_3 type, the formation of these catalysts in the course of thermal treatment and their texture characteristics and phase composition were studied. It was found by chemical and thermogravimetric analysis that the addition of pseudoboehmite to sulfated zirconia hydrate resulted in a decrease in sulfur losses in the course of support production from 55.0 to 2.0% with respect to its nominal amount. As the alumina content was increased from 18.8 to 89.1 wt %, the specific surface area and the pore volume of the support increased nonadditively with respect to mechanical mixtures of sulfated zirconia and γ-alumina (from 155 to 197 m~2/g and from 0.24 to 0.52 cm~3/g, respectively); in this case, a maximum deviation was 18-21%. The experimental results can be explained by chemical interactions between the initial components of the supports. The results of thermogravimetric and X-ray diffraction analysis suggest that the reaction products are sulfated alumina and a sulfated ZrO_2-Al_2O_3 solid solution.