Synthesis and characterization of ZSM-22 zeolites and their catalytic performance in alkylation reaction

The ZSM-22 molecular sieves with various morphologies were synthesized by different methods. XRD, SEM, BET, MAS NMR, NH₃-TPD and Py-FTIR were used to study the structure, morphology, surface area, Si-Al coordination and acidity of the samples. Furthermore, the toluene-methanol alkylation as probe reaction was used to investigate the effect of ZSM-22 zeolites morphology on catalytic performance. The lattice parameters, surface areas, Si-Al coordination and acidity of all samples are obviously different. As a result, the interaction of each bundle of the bundle-like ZSM-22 zeolites leads to the structure change of Si (4Si) coordination, the increase of T3 and T4 with decrease of T2 location, and thus displays more L acid sites. At 380℃ reaction temperature, the bundle-like ZSM-22 zeolite catalyst shows high selectivity to p-xylene (76.1%) at about 16.7% conversion in the toluene-methanol alkylation.