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

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.