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 °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.

Graphical abstractBronsted acidic ionic liquids with SO3-H functionality were prepared, characterized and their catalytic activity in tert-butylation of p-cresol with tert-butyl alcohol was investigated. Kinetic investigations show lower alcohol to p-cresol mole ratios, lower ionic liquid to p-cresol ratio and temperature as low as 70 °C gave p-cresol conversion. The catalyst activity was retained even after 5 recycles.Figure optionsDownload full-size imageDownload high-quality image (126 K)Download as PowerPoint slide