Influence of Zn species in MWW zeolite on the ethane dehydroaromatization with the assistance of propane co-dehydroaromatization and CO2 reduction

Abstract

The Zn-containing HMCM-22 samples with different zinc species were prepared and characterized to discriminate the influence of zinc species on the ethane activation by the initial C-H bond cleavage or the β-H cleavage dehydrogenation step of alkyl zinc species (Zn-C2H5) through the propane co-dehydroaromatization and CO2 reduction process. The synergistic effect of zinc species types with the Brønsted acid sites (BAS) of the parent zeolite HMCM-22 had a significant effect on the ethane dehydroaromatization. The synergistic effect between ZnO species and BAS had better ethane conversion and aromatics selectivity in ethane dehydrogenation, while the poor synergistic effect between ZnOH+ species and BAS was not conducive to the formation of aromatics, and ZnOH+ species was more conducive to ethane dehydrogenation. The ZnOH+ has better catalytic performance in CO2 activated ethane and promote the β-H desorption of Zn-C2H5 in ethane dehydrogenation. The synergetic effect of ZnO species and BAS in the zeolite facilitates the hydride transfer activation of ethane by propylene carbenium ions thus enhancing the ethane conversion through ethane-propane co-aromatization.