Highly dispersed Cu catalyst based on the layer confinement effect of Cu/Zn/Ga-LDH for methanol synthesis

The small amount of promoter has shown increase in the methanol formation rate by several folds. Hence, hydrotalcite having sufficient trivalent cations are preferred; however, traditional coprecipitation route often leads to poor Cu dispersion owing to higher cationic charge in the layered structure that result in aggregation of the sheets. The present paper reports synthesis of porous, nanostructured Cu/ZnO/Ga2O3 catalysts from pure phase hydrotalcite precursors by using aqueous miscible organic solvent treatment method. The 20% Ga containing catalyst showed ca. 2.5-fold increase in both surface area and % dispersion of the exposed Cu as compared to that prepared from standard coprecipitation method with similar composition. The stabilization induced by mutual dispersion of Cu, Zn and Ga components in the exfoliated sheets resulted in confinement of the Cu particle size up to 5 nm in the spent catalyst. The best performing catalyst of the series, Cu0.4Zn0.4Ga0.2-LDO exhibited STY of 762 mg•gCat−1•h−1 for methanol formation from syngas which was decreased by only 8.6% during 50 h of the reaction on stream. Further, it was revealed that, Ga is more conductive to stabilization of Cu as compared to Al, resulting in 23% higher methanol formation rate as compared to the Al containing catalyst.