The acidic properties of TiO2-SiO2 and its catalytic activities for the amination of phenol, the hydration of ethylene and the isomerization of butene

Abstract

Abstract The generation of strong acid sites was observed on the binary oxide, TiO2-SiO2, which was obtained by a coprecipitation method. The acidity and acid strength of the mixed oxide of a certain composition were estimated to be higher than those of SiO2-Al2O3 containing 20 wt% of Al2O3 by n-butylamine titration and by the adsorption of basic molecules on the surface. The acidity depended both on pretreating temperature and the catalyst composition. The highest acidity per unit weight of catalyst was observed when TiO2-SiO2 (mole ratio = 1) was heated at 500 °C. The binary oxide showed high catalytic activity and selectivity for the amination of phenol with ammonia to produce aniline, but low activity and selectivity for the hydration of ethylene. The isomerizations of butenes were also catalyzed; the products ratio of cis-/trans-2-butene was 1–2. The catalytic action for three reactions is well interpreted in terms of the acidic property. The mechanism of the generation of acid sites by mixing TiO2 with SiO2 is discussed.