Effect of calcination temperature on K modified Ag-Fe/ZnO-ZrO₂ catalyst structure and its performance for higher alcohols and DME synthesis from CO hydrogenation

A series of K modified Ag-Fe/ZnO-ZrO₂ catalysts were prepared by co-precipitation method under different calcination temperatures. The effect of calcination temperature on the catalytic performance for higher alcohols and dimethyl ether(DME) synthesis from CO hydrogenation was investigated. The catalysts were characterized by nitrogen adsorption, XRD, H₂-TPR and CO-TPD. The results showed that the catalyst calcined at 250 ℃ could not reach the optimal performance due to insufficient active sites formed at the lower calcination temperature. The catalyst calcined at 300 ℃ exhibited highest CO conversion and higher selectivity of higher alcohols and DME and highest space time yield of higher alcohols and DME reached. As the calcination temperature increased further, the CO conversion decreased, while the selectivity of higher alcohols decreased at first and then increased, the selectivity of DME increased. The catalytic performance of the catalyst was mainly related with its specific surface area, reduction capacity, the dispersion of the σ-AgFeO₂ species and CO adsorption-desorption properties. It was proved that the catalyst with larger specific surface area, being easily reduced, higher dispersion of σ-AgFeO₂ specie and more CO adsorption active sites, would be helpful for CO hydrogenation conversion. The decrease of the non-dissociative adsorption strength for CO on the surface active sites of the catalyst is favorable for the generation of higher alcohols and DME, while the increase of the dissociative adsorption strength for CO is not favorable for the formation of hydrocarbons.