An experimental and thermodynamic study for conversion of CO2 to CO and methane over Cu-K/Al2O3

• Cu-K/Al2O3 was prepared by wet impregnation method and used for conversion of CO2 to CH4 and CO.
• Thermodynamic analysis based on Gibbs free energy minimization was used to predict CO2 conversion and product yield and selectivity.
• Carbon dioxide conversion has decreased with increasing temperature up to 850 K then increased at higher temperature values.
• Increasing reactor pressure lead to increase conversion and selectivity of CH4.
• Increasing H2/CO2 molar ratio lead to increase both CO2 conversion and CH4 selectivity.

Catalytic hydrogenation of CO2 to CO and hydrocarbons is carried out over a wide range of catalysts. Group of VIIIB transition metals proved high conversion and selectively for CO and methane, however, low cost and effective catalysts are preferable especially in large industrial scale. In this work an experimental and thermodynamic analysis was carried out for conversion of CO2 to CO and methane over K-Cu/Al2O3 catalyst. Wet impregnation technique was employed to introduce different loadings of copper on the surface of K/Al2O3. The obtained catalysts were characterized for their crystalline phase, surface area, and morphology and pore size distribution. XRD and EDXS illustrated the presence of both K and Cu where a maximum loading of 1.62 wt% of Cu was achieved on a catalyst surface having 0.46 wt% potassium. BET analysis showed a slit mesoporous surface with average size of 0.255 cm3/g and a total surface area of 114.98 m2/g.The obtained catalysts were tested for hydrogenation of CO2 at different reaction conditions and the results of conversion and selectivity were compared with the theoretical values. It was found that at a given molar ratio of H2/CO2(4:1) the increase in reaction temperature from 500 K to 850 K resulted in decreasing both the conversion (from 98% to 64.5%) and selectivity of CH4 (from 100% to 66%). This decrease was noticeable at lower pressure. Further the increase in temperature above 850 K, increased CO2 conversion and CO selectivity.

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