The direct synthesis of Zn-incorporated nanosized H-ZSM-5 zeolites using ZIF-8 as a template for enhanced catalytic performance

Abstract

Zn-incorporated nanosized H-ZSM-5 zeolites were synthesized via a novel and facile route using zeolitic imidazolate framework-8 (ZIF-8) as the template in a steam-assisted conversion process. The prepared zeolites were characterized using various techniques including XRD, nitrogen adsorption–desorption, SEM, TEM, TGA, NH₃-TPD and pyridine-FT-IR spectroscopy. The crystallization time and ZIF-8 loading were extensively investigated to elucidate the crystallization process, morphology and structural characteristics of the prepared zeolites. The results show that the formation of Zn-incorporated nanosized H-ZSM-5 zeolites involves two stages: dissolution-impregnation and crystallization. The increased amount of ZIF-8 helps to increase the number of active metal Zn sites. Furthermore, the incorporation of ZIF-8 effectively facilitates the formation of Lewis acid sites and increases the acidity. Thus, the Zn-incorporated nanosized H-ZSM-5 zeolites showed a high catalytic activity and H₂ yield as well as excellent catalytic stability when used in dimethyl ether steam reforming.