Shape-selective and acid catalyzed alkylation of phenol with isobutylene over zeolite beta

Abstract

Abstract The shape-selective alkylation of phenol with isobutylene to para-tert-butyl phenol (p-TBP) and 2,4-di-tert-butyl phenol (2,4-DTBP) has been studied over zeolite beta. The influence of reaction parameters as well as thermal treatment and pyridine poisoning of zeolite beta on the tert-butylation of phenol was evaluated. The surface acidity of the catalysts was characterized by means of NH3-TPD and pyridine adsorbed IR (Py-IR) techniques. It revealed that the fresh H-form zeolite beta was highly active and shape-selective in alkylation of phenol with isobutylene. p-TBP and 2,4-DTBP were the predominant alkylation products. Reaction temperature, reactant molar ratio, space velocity and surface acidity showed different impact on the alkylation. High temperature calcination of zeolite beta benefited the selective formation of 2,4-DTBP at the expense of p-TBP. In the present work, adsorption of pyridine on zeolite beta at low content up to 3 wt% resulted in little change in the phenol conversion and the product distribution, while at high content the phenol conversion and the p-TBP selectivity decreased. Medium and weak acid sites were the active centers for the alkylation of phenol with isobutylene. Alumina as bondant at a content up to 30 wt% showed almost no effect on the conversion of phenol.