Gas-phase hydrogenation of 4-tert-butylphenol over Pt/SiO2

Gas-phase hydrogenation of 4-tert-butylphenol (4-TBP) over 1% Pt/SiO2 to cis and trans 4-tert-butylcyclohexanol (4-TBCHOL), via the intermediate 4-tert-butylcyclohexanone, was studied in a differential reactor at atmospheric pressure and at temperatures between 127 and 227degreesC. The formation of by-products due to hydrogenolysis played an important role in the reaction at temperatures over 200degreesC. The rates of 4-t-butylcyclohexanol and 4-t-butylcyclohexanone formation passed through a maximum at 187degreesC. The catalyst deactivation was also considerable. Being thermodynamically more stable the trans form of the alcohols isomers is produced in separate experiments by epimerization in the presence of hydrogen as an astoichiometric compound. The reaction network for the reaction is proposed. (C) 2004 Elsevier Inc. All rights reserved.