Study On Hydrogenation Of Carbon Dioxide Catalyzed By Transition Metal Complex Catalyst

Owing to the increasing emissions of carbon dioxide, human life and the ecological environment have been affected by global warming and climate changes. In order to reduce the concentration of carbon dioxide in the atmosphere, various strategies have been implemented such as separation, storage, and utilization of CO2, Especially in the field of carbon dioxide catalytic hydrogenation, it has become a hot research topic to realize the economic efficiency of chemical conversion of carbon dioxide.In this paper, a series of transition metal Kx/Cu-Fe-Zn catalysts were prepared, the impact of potassium promoter on product distribution for CO2 hydrogenation over Cu-Fe-Zn catalyst was investigated.In addition, we also prepared bimetallic catalysts Ni-Cr/γ-Al2O3 for CO2 methanation. The main works are introduced as follows:(1) Kx/Cu-Fe-Zn catalysts were prepared by a combination co-precipitation and impregnation method. The physiochemical characterizations of these catalysts were performed by using BET, H2-TPR, XRD, TEM and XPS techniques to study the effect of potassium on the textural properties, reduction behaviour, structural and morphological change. The effect of addition of potassium promoter on CO2-conversion, product distribution and deactivation were study for CO2 hydrogenation in a fixed bed reactor. The maximum catalytic activity was obtained from K0.1/Cu-Fe-Zn catalyst and its catalytic activity decreased slightly thereafter. The CO2 conversion reached the highest value of 68.7% over K0.1/Cu-Fe-Zn at 350℃. In addition, the results revealed that addition of potassium promoter shifted selectivity to high molecular weight compounds and facilitated the formation of higher alcohols and oxygen containing compounds in the products. The possible mechanism in the presence of potassium was discussed.(2) Bimetallic catalysts Ni-Cr/γ-Al2O3 were prepared by a co-impregnation method. The structure and surface property of the catalysts were investigated by BET、 H2-TPR、XRD、XPS characterization. Methanation activities of the catalysts were determined in a fixed bed reactor. The results showed that Ni-Cr/γ-Al2O3 exhibited higher catalytic activity than Ni/γ-Al2O3 and Cr/γ-Al2O3.