SELECTIVE PHENOL HYDROGENATION IN AQUEOUS PHASE ON PD-BASED CATALYSTS SUPPORTED ON HYBRID TiO2-CARBON MATERIALS

摘要

A reaction in where the interplay between support and metal active phase becomes determinant, is the catalytic hydrogenation of phenol to cyclohexanone. This ketone is of industrial interest for the production of caprolactam and adipic acid [1]. The phenol hydrogenation route is undertaken through either two-step or one-step processes. In the two-step procedure, phenol is first hydrogenated to cyclohexanol, which is in turn dehydrogenated to cyclohexanone. The one-step selective hydrogenation of phenol to cyclohexanone is advantageous from an efficiency standpoint [2], and the reaction can be conducted in gas or liquid phase. The gas-phase phenol hydrogenation is usually performed at high temperatures over supported Pd catalysts and different supports [3]. However, liquid-phase phenol hydrogenation can be of interest since the reaction can be performed at relatively low temperatures [4]. The attainment of high selectivity (>95%) at high phenol conversion (>80%) is a challenge [2] because cyclohexanone can be further hydrogenated to cyclohexanol under the reaction conditions [5]. From the different commercial catalytic support we thought that TiO2-carbon composites could be suitable supports of an active metal (Pd) to catalyze the hydrogenation of phenol to cyclohexanone [6]. Thus, a series of TiO2-carbon composites have been prepared in where the carbon was generated through different routes changing the polarity of the surface [7]. When Pd is supported on TiO2-carbon composites, it is possible to achieve close to 100% yield to cyclohexanone or to cyclohexanol depending on the surface properties of the support.