Coke Mechanism of Hollow Capsule Mo/HZSM-5 During Methane Dehydroaromatization

Abstract

Purposes Methane dehydroaromatization (MDA) is a frontier topic in the field of natural gas chemical industry. Methods Mo/commercial-HZSM-5, Mo/nano-HZSM-5, and Mo/hollow capsule HZSM-5 were synthesized by using a conventional wet impregnation strategy. The samples were characterized by ICP, XRD, BET, SEM, TEM, NH3-TPD, and XPS, and tested in MDA reaction. The properties of carbonaceous species were measured by TG and TPO techniques. The carbon cycle path was investigated through periodic 12CH4/13CH4 isotope switch pulse experiment over Mo/hollow capsule HZSM-5 catalyst during MDA reaction. Findings The active carbonaceous species located inside the pores could take part in the formation of benzene. Among these three Mo-based catalysts, the Mo/hollow capsule HZSM-5 showed higher CH4 conversion and aromatic yield, as well as superior catalytic lifespan. Compared to Mo/nano-HZSM-5 in zeolite particle size and acidity, Mo/hollow capsule HZSM-5 with lower deactivation rate is attributed enhanced gas molecules diffusion in its hollow capsule structure.

Keywords

• methane dehydroaromatization
• hollow capsule zeolite
• coking
• deactivation
• isotope labelling