Alkylation of Biphenyl CyclohexNE over Oxalic Acid Modified Mcm‐22 Zeolite Catalyst

Abstract 4,4′‐cyclohexylphenyl (4,4′‐DCBP) and 4‐cyclohexylbiphenyl (4‐CBP) were synthesized from biphenyl with cyclohexene over MCM‐22 zeolites. Zeolite samples were prepared using oxalic acid to dealuminize MCM‐22 zeolite, characterized with XRD, BET, NH 3 ‐TPD, Py‐IR, and XRF. Catalytic performance in biphenyl cyclohexylation reaction was conducted to optimize the reaction parameters. The results showed that the crystallinity of the oxalic acid treated MCM‐22 zeolite did not change significantly, but the surface acid amount and acid strength decreased. Concentrations of oxalic acid below 0.6 mol/L was used to remove the non‐skeletal aluminum to a certain extent, thus reducing the number of inactive acidic sites and inhibiting the isomerization reaction, and this in turn enhanced the tendency of alkylation reaction. Under the optimized conditions of 0.5 MPa and 230 °C, the results from 200 min of reaction in micro reactor show that the 0.6 mol/L oxalic acid modified zeolite generated the best performance, with the highest conversion of 57.1%, the highest 4,4′‐DCBP selectivity of 62.0% and the highest yield of 41.1%. After 5 times of reuse, the conversion and selectivity of the catalyst decreased slightly, and the yield level remained above 90.8% of the initial state, showing superior stability of the catalyst.