Enhanced conversion of CO2 to aromatics over spinel Mg3-XCrXO4 coupled HZSM-11 nanosheets bifunctional catalyst

Abstract

CO₂ and green hydrogen for aromatics production are effective methods to mitigate CO₂ emissions. Herein, Mg_3-XCr_XO₄ spinel oxide was constructed via co-precipitation of Mg and Cr, followed by physical mixing with HZSM-11 to form a metal oxide-zeolite (OX-ZEO) bifunctional catalyst. The catalytic performance of this system in CO₂ aromatization was systematically evaluated. Notably, the designed catalysts followed a methanol-mediated pathway, overcoming limitations of the Anderson-Schulze-Flory distribution in aromatic hydrocarbon products. At varying Mg/Cr molar ratios, MgCr₂O₄/HZSM-11 exhibited the highest single-pass CO₂ conversion of 19.2 % and the highest aromatic selectivity of 75.2 % (excluding CO). Additionally, the optimal reaction conditions were determined for MgCr₂O₄/HZSM-11, achieving an excellent aromatic selectivity of 82.4 % and a CO₂ conversion of 22.6 % at 320 °C, a gas hourly space velocity (GHSV) of 1200 mL·gat⁻¹·h⁻¹ and a pressure of 3.5 MPa. After 100 h, the MgCr₂O₄/HZSM-11 tandem catalyst maintained substantial catalytic activity, with aromatic selectivity and CO₂ conversion of 79.3 % and 21.1 %, respectively. This strategy offers valuable insights for designing OX-ZEO bifunctional catalysts.