Preparation of a Pd/Ni Bimetallic Catalyst and its Application in the Selective Hydrogenation of Phenol

At present, through the coking, gasification and liquefaction of low-rank coal such as lignite and long-flame coal in industry, many low-temperature tar samples containing a high proportion of phenolic compounds can be produced. Notably, phenolic compounds are the main raw materials in the chemical industry and can be used to produce many important materials. In particular, phenolic compounds are 3~4 times more expensive than coal tar. On the basis of the importance and economy of coal tar in the production of phenolic compounds, phenol, a phenolic product of coal tar, was studied. The selective hydrogenation of phenol to cyclohexanone plays an important role in the chemical industry. The performance of phenol hydrogenation is highly correlated with the surface properties of the catalyst carrier, and good carrier selection contributes to excellent catalytic activity and stability, leading to overall process improvement in industrial-scale applications. The diversity of the structure and composition of metal oxides is conducive to the development of high-performance catalysts to promote the selective hydrogenation of phenol. Currently, supported precious metal catalysts have been widely used in the hydrogenation of phenol. Although Pd-based catalysts have improved, the loss of active sites is still an inherent shortcoming of supported catalysts, and the catalyst cost needs to be further considered. After surface modification of the ZrO2 carrier, ascorbic acid (AA) was used to introduce a second metal to reduce the loading capacity of the precious metal Pd. The effects of adding a second metal (Fe, Co, or Ni) on the catalyst activity, hydrogenation product selectivity and stability during phenol hydrogenation were investigated. The surface physicochemical properties of the bimetallic Pd-X/ZrO2 catalysts were investigated via XRD, XPS, NH3-TPD, H2-TPR and other characterization methods. In addition, to optimize the hydrogenation of phenol, the effects of different solvents on the catalytic performance and selectivity of cyclohexanone were further investigated.