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Catalytic hydrogenation of CO2into fuels and chemicals is regarded as one of the most promising alternatives to reduce the concentration of CO2in the atmosphere. In this study, double-promoted Cu/ZnO catalysts were prepared on Al2O3and CNTs supports via impregnation method. The physicochemical properties of the catalysts were characterized by XPS, TEM, N2adsorption, H2-TPR and CO2-TPD analyses. Introduction of Nb and Zr promoters into the Cu-based catalysts on CNTs support resulted in smaller Cu nanoparticles and improved reducibility compared to those of the Al2O3-supported catalyst. The catalyst activity was evaluated in a fixed-bed stainless steel reactor operated at 22.5 bar and 523K. Conversion of CO2higher than 20% was achieved and product distribution was influenced by the type of catalyst supports.

Hydrogenation of CO2 into methanol is one of the most economical process to reduce CO2 concentration in the atmosphere. Since methanol is an industrial commodity used in chemical products as well as transportation fuel, this process has gained considerable interest, which enables the effective utilization of CO2. Nevertheless, the efficiency of direct CO2 hydrogenation to produce methanol is strongly reliant on the activity of the catalyst. In this regard, the present work highlights the synthesis of methanol, catalytic evaluation and characterization of catalysts Cu/ZnO supported on Al2O3 and SBA-15 pellets with the addition of group IV, V and VII metal oxides mixture as promoters. The catalysts were systematically prepared via impregnation technique with fixed Cu:Zn and promoter ratio from group VII:V:IV. The synthesized catalysts were characterized by H2-temperature-programmed reduction (H2-TPR), field emission scanning electron microscopy (FESEM), X-ray fluorescence (XRF), N2 adsorption-desorption and N2O pulse chemisorption method. The crushing strength of the pellets were also tested. Catalytic performances were evaluated for methanol synthesis from CO2 hydrogenation in a tubular, stainless steel fixed-bed reactor at 250 °C, 2 MPa, gas hourly space velocity (GHSV) 4000 ml/g.h and H2/CO2 ratio of 3:1. The tri-promoted Cu/ZnO supported on Al2O3 pellet resulted in CO2 conversion of 13.3 % compared to 11.61 % from that of SBA-15-supported catalyst. However, the catalyst supported on SBA-15 pellet exhibited 54.59% methanol selectivity, whereas Al2O3-supported catalyst only resulted in 46.73 % methanol selectivity.

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