Study on the high performance catalyst for toluene alkylation to xylene

By comparing the catalytic performance of toluene methanol alkylation over zeolites with different pore structure, it was found that the effective matching of the zeolite pore size with the molecular dynamics size of the target aromatic compounds and the constrained management of the reaction path by pore confinement effect are essential for achieving high performance of alkylation. Combined with XRD, BET, NH₃-TPD and SEM characterization, it has been confirmed that ZSM-5 with Si/Al ratio of 60 modified by successively loading La₂O₃ and P₂O₅ had better hydrothermal stability of the frameworks and most of the strong acidic sites on its internal and external surface were selectively eliminated while the weak and medium strong acidic sites were remained as the active sites of alkylation. The obtained MAT-HZSM-5 exhibited high methanol alkylation efficiency and good stability under nitrogen reaction atmosphere. There was no obvious deactivation during 500 h reaction. The conversion of toluene was maintained at 35%-38%, the selectivity of xylene was 60%-77%, and the methanol alkylation efficiency was higher than 90%.