Syngas to Aromatics on Cu–Zn–Zr and HZSM-5: Modulating the Capability of Oxygenated Intermediate Formation to Improve Durene Selectivity

The maximum durene selectivity can be obtained by the cofeeding approach in the syngas to aromatics (STA) process. In this study, the capability of oxygenated intermediate formation was modulated via simple adjustment of Cu, Zn, and Zr molar ratios, maximizing the durene selectivity and CO conversion. The incorporation of the Zr element enhanced the adsorption for CO and the Zn element accelerated the depletion of active hydrogen from zeolites, which suppressed the excessive hydrogenation of intermediates to alkanes. Meanwhile, the synchronization between oxygenated intermediate formation and aromatization was accomplished through optimization of the active sites of zeolites, bifunctional catalyst coupling approaches, and process parameters. Under optimal conditions, a maximum durene space time yield (STY) of 232.0 μmol/gCat/h at a CO conversion of 90.1% was achieved by CuZnZr642/HZSM-5. Furthermore, the deactivation mechanisms of bifunctional catalysts were primarily attributed to the thermal instability of Cu-based catalysts at high temperatures, wherein carbon deposition elimination of spent zeolites was achieved via calcination under an air atmosphere. This study offers experimental support and theoretical insight into optimizing the STA catalytic system.