Alkylation of p-cresol with tert-butyl alcohol using benign Bronsted acidic ionic liquid catalyst

Novel and environmentally benign Bronsted acidic ionic liquids with SO3-H functionality were prepared using N-methyl imidazole, pyridine, triethylamine and 1,4-butanesultone as the source chemicals. The prepared ionic liquid catalysts were characterized by NMR and their catalytic activity in tert-butylation of p-cresol with tert-butyl alcohol (TBA) was investigated. The effects of reaction time, reaction temperature, reactant mole ratio and the recyclability of the catalysts on the conversion of p-cresol and selectivity to 2-tert-butyl-p-cresol (TBC) and 2,6-di-tert-butyl-p-cresol (DTBC) called butylated hydroxytoluene (BHT) were investigated. Lower alcohol to p-cresol mole ratios, lower ionic liquid to p-cresol ratio and temperature as low as 70 degrees C gave 80% conversion of p-cresol. The catalyst activity was found to be almost completely retained even after 5 recycles. Extended Arrhenius equation was used to calculate the rate constants for this reaction. (C) 2010 Elsevier B.V. All rights reserved.