Influence of zinc state on the catalyst properties of Zn/HZSM-5 zeolite in 1-hexene aromatization and cyclohexane dehydrogenation

Abstract

• A two-step wetness impregnation method is beneficial to increase ZnOH + species. • Increasing the amount of ZnOH + species is beneficial to 1-hexene aromatization. • Hydrogen-transfer capability increases linearly with the amount of ZnOH + species. • Dehydrogenation capability increases linearly with the amount of ZnOH + species. Rational design of Zn-containing HZSM-5 zeolite (Zn/HZSM-5) with high reactivity and excellent aromatization performance for olefin aromatization is crucially desired. We develop a new and uncomplicated method to synthesize Zn/HZSM-5 (IMX/Z5) with superior aromatization performance in the paper. Compared to incipient wetness impregnation (IMP/Z5) and mechanical mixing (MIX/Z5), the as-prepared IMX/Z5 presents a higher amount of surface ZnOH + species (2.87%) while keeping identical bulk zinc content. As a result, more surface ZnOH + favor both the aromatization of 1-hexene and cyclohexane dehydrogenation. For the two olefin aromatization pathways (hydrogen transfer and dehydrogenation), it is the first time found both the hydrogen transfer ability and the dehydrogenation ability increase linearly with the amount of surface ZnOH + species while keeping identical bulk zinc content. We believe that the linear relationships are essential to design next generation olefin aromatization catalysts.