A comparison study of mesoporous Mo/H-ZSM-5 and conventional Mo/H-ZSM-5 catalysts in methane non-oxidative aromatization

Abstract

The mesoporous ZSM-5-S and ZSM-5-M samples were synthesized by using ordered mesoporous carbon (CMK-3) and disordered carbon rods (C-MCM-41) as the hard template, respectively, and for comparison, conventional ZSM-5-C was also synthesized with the same synthesis composition and procedure except for the presence of carbon template. The mesoporous ZSM-5 samples exhibited similar geometrical shape, but different pore properties than the conventional ZSM-5. Moreover, Mo-modified catalysts, Mo-ZSM-5-C, Mo-ZSM-5-S and Mo-ZSM-5-M, were prepared for the non-oxidative aromatization of methane. The physical properties and acidities of the samples were characterized by XRD, SEM, TEM, BET and IR spectroscopy. Compared with Mo-ZSM-5-C, the Mo-ZSM-5-S and Mo-ZSM-5-M catalysts showed similar conversions of methane, but higher yields of aromatics. In addition, Mo-ZSM-5-S and Mo-ZSM-5-M were more stable than Mo-ZSM-5-C. The exceptional catalytic behavior of Mo-modified mesoporous ZSM-5 catalysts may be attributed to the generation of secondary mesoporous systems within the zeolite crystal, which may lead to easier access to the active sites for reactants and be favorable for the diffusion of larger molecule product formed in the microporous channels during the methane aromatization reaction.