Gallium-Immobilized Carbon Nanotubes as Solid Templates for the Synthesis of Hierarchical Ga/ZSM-5 in Methanol Aromatization

Hierarchical Ga/ZSM-5 was synthesized by using a combinative method of steam-assisted crystallization (SAC) and hard templating. Ga-immobilized carbon nanotubes (GaCNTs) were used as hard templates. Compared with Ga-doped ZSM-5 catalysts made by impregnation and by sequential CNT templating and impregnation, hierarchical Ga/ZSM-5 had a moderate mesoporosity and possibly a high concentration of (GaO) + -Brønsted acid site. The moderate mesoporosity shortens residence times of products in the ZSM-5 matrix, while the high concentration of (GaO) + -Brønsted acid enhances aromatization activity. These advantages are critical to improve catalytic performance and durability of hierarchical Ga/ZSM-5 in methanol aromatization.