Alkylation of phenols with isobutylene

Abstract

The kinetics of absorption of isobutylene in molten phenol, p-cresol and pyrocatechol were studied in a stirred cell using concentrated sulphuric acid as a catalyst. The absorption of isobutylene in molten phenols was found to conform to pseudo-first-order mechanism. The products of various reactions were analysed by gas-liquid chromatography. The absorption of isobutylene in mono-t-butyl derivatives of phenols was studied in an agitated glass reactor. It was possible to eliminate the effect of diffusion. The values for the rate constant of the second-order reactions between isobutylene and p-t-butylphenol at 104°, isobutylene and 2-t-butyl-p-cresol at 70° and isobutylene and 4-t-butylpyrocatechol at 104° were 49, 40 and 56 ml/g mole/sec, respectively. Mass transfer influenced the rate of alkylation of phenol and p-cresol with isobutylene in a bubble column. However, no significant improvement was observed in the yield of the mono-derivative, which in some cases is the desired product.