Steering the Aspects of MgO-Induced Structure Sensitivity in Cu-Based Catalysts for CO2-Rich Syngas Conversion to Dimethyl Ether: Cu/Zn Ratio and Lattice Parameters

The present work reports the crucial effect of the Cu/Zn ratio and MgO content (10-30%) on lattice parameters as well as the metal surface area of the co-precipitated Cu-ZnO-MgO/gamma-Al2O3 bifunctional catalyst for direct dimethyl ether (DME) synthesis from CO2-rich syngas (H-2/CO = 2). X-ray diffraction analysis of the as-synthesized catalysts showed a prominent structural identity belonging to the malachite-rosasite [(Cu,Zn)(2)(CO3)(OH)(2)] group of minerals. Progressive addition of MgO into the Cu-based catalysts (Cu/Zn ratio = 2-4) exhibited an overall decrease in the cell volume, providing it the required stability. The catalyst possessing the lowest unit cell volume (V-m) exhibited the highest metal surface area, enhanced Cu dispersion, and improved DME synthesis with a negligible decrease in activity over 72 h on stream. The catalytic functionalities, such as total carbon (CO + CO2) conversion (45.6%), CO2 conversion (12.8%), and DME selectivity (90.9%), showed their maxima on the optimized bifunctional catalyst CZ[2]-M(20). Also, the hydrocarbon selectivity was found to be least for this catalyst.

Automated summary

The Cu/Zn ratio and MgO content have a crucial effect on the performance of the Cu-ZnO-MgO/gamma-Al2O3 bifunctional catalyst for DME synthesis. The addition of MgO improves the stability and efficiency of the catalyst.