Performance of Co–Cu bimetallic catalysts for catalytic syngas to produce higher alcohols: Influence of the preparation methods, CoCu ratios, and carriers

Higher alcohols (C₂₊ mixed alcohols) have attracted much attention due to their high application value in the fuel, chemical industry, and the environment. Producing higher alcohols from syngas accords with the atomic economy, whereas the performance of related catalysts is not acceptable. To enhance the catalyst reactivity, stability, and product selectivity, the influence of the preparation methods, Co–Cu ratios, and carriers on the performance of Co–Cu bimetallic catalysts are investigated. First, the bimetallic catalysts with different Co/Cu molar ratio (Co_xCu₁/SiO₂) were prepared by the impregnation method. The results show that the Co₂Cu₁/SiO₂ catalyst showed the best performance with a selectivity of 51.9 % for ROH and 35.5 wt % yield for C₂₊ alcohol. This is because the Cu and Co nanoparticles are uniformly and tightly distributed in the Co₂Cu₁/SiO₂ catalyst. For further improving the performance of the catalyst, the Co₂Cu₁-Z@SiO₂ catalyst was prepared by in situ synthesis method. This Co₂Cu₁-Z@SiO₂ catalyst provides high dispersion and abundant active sites, strong synergetic of Co and Cu species, thus significantly improving the CO conversion rate and ROH selectivity to 75.6 % and 61.3 %, respectively. Besides, compared to Co₂Cu₁/SiO₂ catalyst, the Co₂Cu₁-Z@SiO₂ catalyst promoted synergistic catalysis between the CO dissociation and CO insertion, leading to the better catalyst performance. In addition, the channel limitation of the carrier enables the Co₂Cu₁-Z@SiO₂ catalyst to maintain good stability within 200 h. This provides a new exploration for further development of bimetallic catalysts with better performance, more stability and higher selectivity in syngas conversion to higher alcohols.