Zn‐HZSM‐5 catalysts for methane dehydroaromatization

The nature of the active species in Zn‐containing HZSM‐5 catalysts was investigated by preparing Zn‐HZSM‐5 via three different synthetic approaches: wet ion exchange, wet impregnation, and core–shell synthesis. By investigating the impact of the preparation methods on the distribution of Zn species, and studying the catalytic performance of the resulting materials in methane dehydroaromatization (DHA), it was shown that metallic Zn0 nanoclusters inside the zeolite micropore constituted the most active species for DHA, but get irreversible loss from the catalyst via evaporation at the high‐temperature conditions of DHA. In contrast, Zn2+ anchored at the exchange sites of the zeolite were the most stable species, but provided little to no aromatization activity. As a result, and counter to previous reports in the literature, it was concluded that Zn/HZSM‐5 was not a suitable catalyst for non‐oxidative methane dehydroaromatization. Nonetheless, the study confirmed that well‐dispersed metal species inside the zeolitic micropores were critical for aromatization activity of zeolite‐based catalysts. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 334–344, 2016