A hollow Mo/HZSM-5 zeolite capsule catalyst: preparation and enhanced catalytic properties in methane dehydroaromatization

A hollow Silicalite-1-HZSM-5 zeolite capsule structure (H-S-Z) embedded with Mo nanoparticles was designed and prepared. The H-S-Z was obtained by a dual-layer hydrothermal synthesis method using activated carbon (AC) as a hard template via self-assembly combined hydrothermal crystallization. One layer of Silicalite-1 zeolite shell was first synthesized on the AC core under neutral-like synthesis conditions. Then, a HZSM-5 zeolite shell was synthesized on this Silicalite-1 zeolite shell enveloping the AC core, followed by calcination in air to remove the core AC. After being loaded with Mo, this hollow zeolite capsule catalyst was tested in a methane dehydroaromatization (MDA) reaction. Compared with the conventional solid catalyst, the Mo/H-S-Z catalyst significantly improved the methane conversion, formation rate of the benzene product, and catalytic stability, and inhibited the carbon deposition, due to the accelerated mass-transfer rate in the hollow structure. Furthermore, the catalyst deactivation derived from the side reactions such as poly-aromatics or coke formation at the inner zeolite could be eliminated.