Liquid-phase p - t -butyltoluene autoxidation enhanced by electrochemistry: Activation of the catalytic effect of cobalt acetate

Abstract

The autoxidation of p-t-butyltoluene (TBT) at 80 °C in the liquid phase is carried out with an initial mixture of cobalt(III) and cobalt(II) acetate in an acetic acid solution. The autoxidation kinetics of TBT is appreciably accelerated by electrolysis with a anodic current density of 62.5 A m−2. The electrolysis increases the concentration of cobalt(III) acetate, the actual catalyst of the autoxidation reaction. The end product of oxidation is p-t-butylbenzoic acid (TBBA). p-t-Butylbenzaldehyde (TBBZ) is an intermediary whose concentration passes through a maximum. The oxidation experiments with TBT were performed with total cobalt acetate concentrations ranging from 0.0188 to 0.169 mol dm−3. An increase in total cobalt acetate concentration favours the electrochemical regeneration of CoIII and slightly improves the TBBZ selectivity. The duration of TBT oxidation into TBBA is reduced by a factor of 5 compared with a reaction without electrolysis.