Selective catalytic hydrogenation of phenol to cyclohexanone over Pd@CN: Role of CN precursor separation mode

Abstract

The one-step hydrogenation of phenol to cyclohexanone is green and sustainable. In this study, the effect of a CN (N-doped carbon) precursor separation mode on the catalytic performance of a Pd@CN catalyst for selective hydrogenation of phenol to cyclohexanone in water was investigated. Three modes, i.e., rotary evaporation, centrifugation, and filtration, were designed to separate the CN precursor while preparing the Pd@CN catalyst. The results highlight that the separation mode significantly affects the phenol hydrogenation performance of the Pd@CN catalyst. The best catalytic performance is obtained when separating the CN precursor by the rotary evaporation mode. Based on a series of characterizations, it is confirmed that the separation mode of rotary evaporation can introduce more N into the mesoporous carbon, improve the Pd dispersion, and enhance the basic sites and Pd loading, leading to higher catalytic activity. Furthermore, the Pd@CN catalyst prepared by rotary evaporation exhibits better catalytic stability. Less Pd leaching is responsible for its slight deactivation. These findings can provide a point of reference for the development of Pd@CN catalysts with high catalytic performance.

Highly Selective Hydrogenation of Phenol Catalyzed by Porous BN Supported Ni−Pd Catalysts

“…Conversion of phenol (%) [a] Selectivity of cyclohexanol (%) [a] 5Ni/p-BN 67. tion product catalyzed by Ni is cyclohexanol. [32,40] Therefore, the selectivity of cyclohexanol first increased and then stabilized, which also proved that there was a synergistic effect between Pd and Ni in this reaction process and the partial product of cyclohexanone will be further catalytic hydrogenation to cyclohexanol. Furthermore, the reaction diagram is demonstrated in Figure 8.…”

“…The results show that the prepared bimetallic catalysts have high catalytic efficiency for phenol. For the hydrogenation of phenol, Pd‐based catalyst can obtain higher cyclohexanone selectivity, while the main hydrogenation product catalyzed by Ni is cyclohexanol [32,40] . Therefore, the selectivity of cyclohexanol first increased and then stabilized, which also proved that there was a synergistic effect between Pd and Ni in this reaction process and the partial product of cyclohexanone will be further catalytic hydrogenation to cyclohexanol.…”

Insights into the Solvent Effect on the Synthesis of Pd@PC-COFs for Phenol Hydrogenation

“…28 Pdbased catalysts have been paid more attention in the selective phenol hydrogenation owing to the high hydrogenation performance and relatively low cost. 29,30 In the selective hydrogenation process of phenol, phenol is first adsorbed on the support, and then the product cyclohexanone is generated by the reaction of the adsorbed phenol with the activated hydrogen by active components. 12 Therefore, the carrier plays an important role in the synthesis of catalysts toward the phenol hydrogenation.…”

“…In view of this, researchers have carried out a lot of studies on catalysts for the selective phenol hydrogenation. − Compared with noble metal catalysts, nonnoble metal catalysts are cheap and widely available, but their phenol conversion and cyclohexanone selectivity are lower. − Noble metals catalysts (Pt, Rh, Ru, and Pd) have good hydrogen absorption and activation ability, leading to high hydrogenation performance even at low temperatures. − However, Pt- and Rh-based catalysts have low selectivity for cyclohexanone. , Although Ru has good hydrogenation capacity and relatively low price, it is easy to leach from the supports and deactivate during the reaction process . Pd-based catalysts have been paid more attention in the selective phenol hydrogenation owing to the high hydrogenation performance and relatively low cost. , …”