Triethylamine-modified Keggin heteropolyacid: a novel phase-transfer catalyst for hydroxylation of benzene with H2O2

Abstract

The Keggin-structured heteropolyacid H4PMo11VO40 and its triethylamine-modified derivative [(C2H5)3NH]4PMo11VO40 were prepared and characterized by FT-IR and UV–visible spectrometry, and elemental analysis. Direct hydroxylation of benzene to phenol by H2O2 over these two catalysts was then compared. The effect of the triethylamine in [(C2H5)3NH]4PMo11VO40 on the catalytic hydroxylation of benzene was investigated in detail. The results showed that although the triethylamine-modified catalyst is not significantly more active than the parent heteropolyacid catalyst, its reaction-controlled phase-transfer characteristics enable easy separation of the catalyst from the reaction medium, and its reuse, suggesting its potential for application to the hydroxylation of benzene to phenol with H2O2.