Methanol to propylene reaction performance and trapped carbonaceous species over zeolites with different topologies

Mesoporous ZSM-5 (MFI), MCM-22 (MWW), ZSM-22 (TON) and SSZ-13 (CHA) zeolites were obtained by TEAOH and NaOH solution treatment. Under the following operating conditions:t=480℃, p=0.1 MPa, m(methanol):m(H₂O)=1:1 and WHSV (methanol)=1.5 h^-1, the catalytic properties of four mesoporous zeolites with different topologies were investigated in the methanol to propylene (MTP) reaction. The fresh and spent samples after 2 h were characterized with XRD, nitrogen adsorption experiments, NH₃-TPD, TG, UV-Rama and GC-MS techniques. It demonstrated that both zeolites exist mesopores after treated by alkali. The mesoporous T-ZSM-5 zeolite had the highest lifetime; the lifetime of T-MCM-22 zeolite with was secondary and deactivation rate was slow; The N-ZSM-22 with one-dimensional channel structure and N-SSZ-13 zeolite with 8-member ring channels both deactivated rapidly. Due to the difference of topology structure and diffusion performance, their coke contents after 2 h increased in the order:T-ZSM-5 < N-ZSM-22 < T-MCM-22 < N-SSZ-13. Moreover, the molecular weight of soluble coke increased with the increasing of coke contents, changed from pentamethylbenzene to polycyclic aromatic hydrocarbons, such as phenanthrene and pyrene.