Preparation And Structure-Performance Research Of Cu/CeO₂ Based Catalyst For Higher Alcohols From Syngas

Higher alcohols synthesised from syngas play an important role in chemical energy. How to improve the selectivity and yield of higher alcohols is one of the most significant issues for the catalyst development. In this work, Cu/CeO₂ based catalysts were prepared by coprecipitation and the effects of different promoters, such as Fe、 Mo、 Ni、 Cs、 Zn and La on catalytic performance were studied. The results showed that Fe made CO conversion and hydrocarbon selectivity improved significantly. The effect of Mo was similar with Fe but relativily milder. The introduction of Ni decreased methanol selectivity, while CO conversion and C²⁺ alcohols selectivity were increased. Cs decreased CO conversion and increased ethanol and propanol selectivities. Zn improved the selectivity of methanol, but it had no positive effect on the selectivity of higher alcohols. La increased the selectivity of iso-butanol. Among all four catalysts with two kinds of metal promoters, only LaMo-Cu/CeO₂ catalyst didn’t show superior catalytic performance compared with individual metal promoter. With the synergy effect of Ni-Mo and the interaction between La and Ni, NiMo-Cu/CeO₂ and LaNi-Cu/CeO₂ catalysts exhibited higher CO conversion and STY of C²⁺ alcohols. In addition, NiMo-Cu/CeO₂ catalyst shared a more uniform distribution of alcohols. The addition of pyrogallol in preparing of NiMo-Cu/CeO₂ catalyst was benefit to the formation of metal ion compound on catalyst surface with Cu+, which resulted in the decrease of methanol selectivity. In general, pyrogallol introduced by coprecipitation gave a better catalytic performance than by impregnation. Finally, the effects of process parameters on catalytic performance over NiMo-Cu/CeO₂ catalyst were investigated. The results revealed that NiMo-Cu/CeO₂ performed better when catalyst was prepared by coprecipitation than by sol-gel method. Besides, the optimal calcination and reaction temperature is 450 ℃ and 310 ℃, respectively. The optimal feed mole ratio of H₂/CO is between 1.5 to 2.0.