Alkylation of phenol with tert-butyl alcohol (TBA) as an alkylating agent was studied in presence of different ionic liquid catalysts. The synthesized ionic liquid catalysts were characterized by H-1 NMR and TGA. It was proved that heteropoly anion-based ionic liquid catalyst is potentially promising candidates in production of 2,4-di-tert-butylphenol (2,4-DTBP) and 2,6-di-tert-butylphenol (2,6-DTBP) with high activity and selectivity. Maximum phenol conversion of 93% was achieved at the molar ratio of phenol:TBA:IL is 1:2:1, reaction time of 3 h and reaction temperature of 80 C with 2,4-DTBP and 2,6-DTBP selectivity of 48 and 41%, respectively. (C) 2017 Published by Elsevier B.V.