Skeletal isomerization of 1-butene over sulfate-promoted zirconia with large surface area prepared by an atrane route

Abstract

Thermally stable tetragonal zirconia was prepared with the aid of interactions between zirconium atrane complex and surfactant cetyltrimethylammonium bromide (CTAB). The results of N 2 adsorption–desorption analysis show that this material contained micropores centered at a pore diameter of about 5 Å. When the prepared zirconia after sulfation was applied to skeletal isomerization of 1-butene, high selectivity to isobutene was observed. This feature may be related to the size of micropores which is the same as the pore diameter of FER zeolite. Two major by-products, propene and pentenes, were formed by the dimerization(oligomerization)-cracking reactions. However, hydrocarbons higher than C 6 were not observed in this work. The n-butenes conversion and product selectivities depend on the operating conditions such as the time-on-stream, the space velocity of 1-butene, the partial pressure of 1-butene and the reaction temperature. Especially, the yields of primary products: propene, isobutene and pentenes, were examined under the conditions investigated in this study. The effect of the concentration of sulfuric acid solution utilized in the preparation of the present catalyst was also investigated. On the basis of these results, the mechanism for the skeletal isomerization of 1-butene on the present catalyst was discussed.