Catalytic Transformations of 4-tert-Butylphenol in Hydrogen Peroxide Solutions in the Presence of Titanium Oxide Compounds and Titanosilicates

Abstract

The selective oxidation of 4-tert-butylphenol by H2O2 solutions in the presence of titanosilicate catalysts could become a promising alternative for the 4-tert-butylcatechol production. In this study the catalytic transformations of 4-tert-butylphenol in hydrogen peroxide solutions were investigated in the presence of the titanium oxide samples of different phase composition and the samples of crystalline and amorphous titanosilicates. The primary product of the 4-tert-butylphenol conversion in the presence of both hydrated and amorphous TiO2 forms was 4-tert-butylphenol ether. The maximum selectivity value of the latter was 80 mol.%. The 4-tert-butylcatechol formation selectivity reached its maximum in the presence of the anatase TiO2 form but did not exceed 20 mol.%. The TS-1 microporous crystalline titanosilicate was shown to ehxibit low activity in the 4-tert-butylphenol transformation due to the steric limitations on the diffusion of the substrate molecules towards catalytic active centers. Mesoporous amorphous titanosilicates were more selective in the 4-tert-butylcatechol formation than the titanium oxide compound samples. It was found that the mesoporous titanosilicate content in the reaction mix, temperature and the experiment duration affected both the 4-tert-butylphenol conversion and the 4-tert-butylcatechol formation selectivity. The maximum 53 mol.% formation selectivity value of the 4-tert-butylcatechol was shown to occur over the amorphous mesoporous titanosilicate containing 1.9 wt.% of Ti, the 4-tert-butylphenol conversion value being equal to 42 mol.%.