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Liquid-phase oxidation of p-cresol over insoluble cobalt oxide (Co 3 O 4 ) 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.

Two steps involving catalytic hydrogenation of nitrobenzene to phenylhydroxylamine (PHA) in acid medium and its rearrangement to p-aminophenol (PAP) were studied separately in a batch reactor, using a well-characterized 3% Pt/C catalyst. The first step of hydrogenation of nitrobenzene to PHA could be carried out at 303 K and a H2 pressure of 0.69 MPa with complete conversion of nitrobenzene, while the achieved selectivity to PHA was higher than 90% with some formation of aniline, even at lower temperature. The second step of PHA rearrangement to PAP could be achieved under a hydrogen atmosphere at elevated temperature of 353 K to give a maximum selectivity to PAP of 74%.