Regeneration of deactivated H-ZSM-5 for aromatization by dielectric barrier discharge plasma

Abstract

A dielectric barrier discharge (DBD) plasma regeneration reaction was conducted at atmospheric pressure and temperature. This method was found to be very effective in removing carbon deposits after a non-oxidative aromatization from acetylene. When a fresh H-ZSM-5 catalyst was used for the aromatization, coke was by-produced and it could be ascribed to the primary reason for deactivation. By applying the DBD plasma to the deactivated catalyst bed at ambient temperature and pressure, the removal of carbon deposition with microdischarge and aeration was very effective; therefore, it is believed that additional thermal activation might not be necessary. More amount of coke was removed by supplying higher power to the catalyst bed. According to the results of XRD, physisorption, 27Al MAS NMR, and NH3-TPD analyses, it was confirmed that the structure and the acid site distribution of H-ZSM-5 were successfully retained even after the plasma treatment. Aromatization over the plasma-regenerated catalyst led to mild deactivation at the early stage and afforded comparable BTX selectivity to fresh H-ZSM-5 catalyst. Compared with the results obtained using the thermally regenerated catalyst, the structural stability was found to be higher and the BTX selectivity was kept higher during most of the reaction time for the plasma-regenerated catalyst.