Comparative Research on the Supercritical Catalytic Cracking of n-Dodecane and Kerosene Using Nanosheet MFI Zeolite

In order to overcome the low catalytic activity and stability of ZSM-5 zeolite due to its microporous and long diffusion path to the substrates and products, a nanosheet MFI (NS-MFI) zeolite with higher activity and stability was synthesized by hydrothermal method, and it was characterized by XRD, BET, SEM, TEM and NH₃-TPD methods. The supercritical catalytic activity of NS-MFI zeolite was studied by cracking n-dodecane and kerosene, and the activity was compared with that of conventional ZSM-5 zeolite. Compared with ZSM-5, NS-MFI showed higher BET surface area, larger volume and ultrathin lamellar structure. During the cracking of n-dodecane, the NS-MFI zeolite showed higher gas generation rate, selectivity of alkenes and heat sinks because of its special morphological structure; during the cracking of kerosene at 550℃, NS-MFI showed equivalent activity to ZSM-5 zeolite, because large amount of cycloalkanes exist in kerosene which is difficult to be cracked. While at 600℃, the NS-MFI zeolite showed better performance. However, the activities of kerosene cracking by the two zeolites were both lower than that of n-dodecane cracking. So, it can be concluded that porous and ultrathin lamellar structure is beneficial to the diffusion of reactants and products, and hence improving the catalytic activity and stability.