Direct Synthesis of Ethylene and Hydrogen from CO₂ and Ethane over a Bifunctional Structured CaO/Cr₂O₃‑V₂O₅/ZSM‑5 Adsorbent/Catalyst Monolith

In this study, we synthesized bifunctional adsorbent/catalyst materials (BFMs) consisting of a CaO adsorbent admixed with Cr2O3-V2O5/ZSM-5 catalysts. The obtained BFMs were further formulated, processed, and shaped through additive manufacturing (3D printing) method. The physical and chemical properties of structured CaO/Cr2O3-V2O5/ZSM-5 adsorbent/catalyst monoliths were thoroughly characterized and evaluated. The effects of operating conditions including reaction temperature, ethane composition, and space velocity on single-bed CO2 capture and selective formation of ethylene and hydrogen were systematically investigated. The adsorption–reaction experiments revealed that Cr-based BFMs, in particular, CaO/Cr4/ZSM-5 monoliths undergo the oxidative dehydrogenation pathway with high C2H4 selectivity, whereas increasing the content of V leads to enhanced catalytic activity for the reforming pathway to produce hydrogen. The best adsorption/catalyst BFM performance was observed for CaO/Cr1-V3/ZSM-5, which was balanced between the two reaction pathways and resulted in 1.72 mmol/g CO2 capture capacity, 63.95% CO2 conversion, 22.4% C2H6 conversion, 42% C2H4 selectivity, and 45% syngas (31% hydrogen) selectivity. Furthermore, the cyclic test results revealed excellent catalytic stability across the initial two cycles over CaO/Cr1-V3/ZSM-5 monolith, highlighting the synergetic effect of bimetallic catalyst constituents on maintaining high catalytic durability. This novel formulation and processing method can pave the way toward formulation of various structured BFM monoliths with cooperative CO2 adsorptive removal and catalytic performance for one-pot CO2 capture–utilization and simultaneous production of light olefins and hydrogen