Alkylation of Phenol and tert-Butyl Alcohol Catalyzed by Deep Eutectic Solvents under Mild Conditions

tert-Butyl phenol is an important intermediate for organic synthesis and the preparation of tert-butyl phenol under mild conditions is of great significance. In our work, five kinds of deep eutectic solvents were synthesized to catalyze the alkylation of phenol and tert-butyl alcohol. The deep eutectic solvent consisting of choline bisulfate (ChBf) and p-toluene sulfonic acid (p-TsOH) was proved to be a better catalyst. By employing the response surface methodology to optimize the reaction conditions, we found that 99.5% conversion of tert-butyl alcohol was obtained at a reaction temperature of 30 °C. The temperature of alkylation reaction was much milder than those in previous reports. The kinetic model for this reaction was established based on the Runge–Kutta–Fehlberg method and the recycle performance for the catalyst was evaluated. Excellent conversion of tert-butyl alcohol can be obtained after recycling eight times. This method provides a potential route for the synthesis of tert-butyl phenol under mild conditions in industry.