Industrial & Engineering Chemistry Research, Vol.60, No.5, 2326-2336, 2021
Identification of Metal/Acid Matching Balance over Bifunctional Pd/H beta toward Benzene Hydroalkylation
Bifunctional Pd/H beta catalysts with uniformly distributed palladium nanoparticles (Pd NPs) were successfully synthesized by a facile methanol-mediated weakly capping growth approach (WCGA). A series of Pd/H beta catalysts with different metal loadings and Si/Al ratios were used for benzene hydro-alkylation, and the identification of metal/acid matching balance over bifunctional Pd/H beta toward benzene hydroalkylation performance was investigated. The obtained characterization and catalytic activity test results demonstrated that the weak acid site and Lewis acid site have greatly affected the benzene conversion, and the strong acid site as well as Bronsted acid site had more of an effect on the alkylation process. The best hydroalkylation performance was achieved by tuning the acid/metal molar ratio at 22.4 mu mol of H+/mu mol of exposed Pd with a high cyclohexylbenzene (CHB) selectivity of 51.7% at a benzene conversion of 63.4%, which is the best CHB yield currently obtained for all we know. In addition, the stability of Pd/H beta catalysts was tested and compared with that prepared by the incipient wetness impregnation (IWI) method, which showed good stability, and no obvious particle aggregation was found. This work provides guidance for exploring the construction of bifunctional catalysts and the balance of metal/acid sites.