Selective Synthesis of p-Hydroxybenzaldehyde by Liquid-Phase Catalytic Oxidation of p-Cresol

Liquid-phase oxidation of p-cresol over insoluble cobalt oxide (Co3O4) catalyst under elevated pressure of air gave 95% selectivity to p-hydroxybenzaldehyde, an important flavoring intermediate. The selectivity to p-hydroxybenzaldehyde could be enhanced by manipulating the concentrations of p-cresol, sodium hydroxide, and catalyst and the partial pressure of oxygen in such a way that the byproducts normally encountered in this oxidation process were eliminated or minimized significantly.