Selective phenol hydrogenation in aqueous phase on Pd-based catalysts supported on hybrid TiO2-carbon materials

TiO2-C materials have been prepared by solvothermal and slurry synthesis and the influence of carbon properties upon the catalytic activity and selectivity of Pd-based catalysts on phenol hydrogenation in aqueous phase under mild reaction conditions has been studied. The nature of the catalysts can be modified to direct the reaction either to cyclohexanol (∼100% yield) or to cyclohexanone (∼96% yield). High selectivity to cyclohexanone is obtained with Pd on more polar TiO2-C supports, while when these are transformed into hydrophobic TiO2-C supports the resultant catalyst becomes selective to cyclohexanol. Thus, product distribution during the selective phenol hydrogenation in aqueous phase is easily controlled by controlling the functionalization of the hybrid support.

Phenol hydrogenation. (A) General reaction steps. (B) General pathway for selective hydrogenation of phenol to cyclohexanone.Figure optionsDownload high-quality image (86 K)Download as PowerPoint slideHighlights
► Selective phenol hydrogenation under green chemistry conditions.
► Pd-based catalysts supported on hybrid TiO2-carbon materials.
► High selectivity to cyclohexanone with Pd on polar TiO2-C supports.
► High selectivity to cyclohexanol with Pd on non-polar TiO2-C supports.
► Control of the functionalization of the hybrid support.