Effect of acid strength on the catalytic activity of NiOTiO 2 modified with acids

Abstract

Nickel oxide-silica is known to be effective for the dimerization of ethylene at room temperature. The catalyst is also active for the isomerization of n-butane, the mechanism of which has been proved to be of a proton donor-acceptor type. It has been suggested that the active site for dimerization is formed by an interaction of a low valent nickel ion with an acid site. In the previous papers from this laboratory, it has been shown that the NiO-TiO{sub 2} and NiO-ZrO{sub 2} modified with sulfate ion is very active for ethylene dimerization. High catalytic activities in the reactions were attributed to the enhanced acidic properties of the modified catalysts, which originated from the inductive effect of S{double bond}O bonds of the complex formed by the interaction of oxides with sulfate ion. The dependency of the catlaytic activity on the acid strength was reported by numerous investigators. The acid strength of a solid is the ability of the surface to convert an adsorbed neutral base into its conjugate acid as described by Walling. The present paper is concerned with the preparation of NiO-TiO{sub 2} modified with various acids, H{sub 2}SO{sub 4}, H{sub 3}PO{sub 4}, H{sub 3}BO{sub 3}, and H{sub 2}SeO{sub 4},more » and the dependence of catalytic activity on acid strength. For this purpose, 1-butene isomerization and ethylene dimerization, which is known to be catalyzed by acid catalysts, were chosen as test reactions.« less