Turning CO2 into an alternative energy source: Study on methanation reaction optimization

Abstract

Carbon dioxide (CO₂) methanation is an effective technology for mitigating CO₂ emissions, major contributor to global warming, by converting CO₂ into methane (CH₄). This work describes use of CO₂ (feedstock) using molecular hydrogen to produce CH₄ using mono-metallic Ni/γ-Al₂O₃ catalyst in continuous flow fixed bed downflow reactor. The catalyst was characterized by XRD, SEM, BET, H₂-TPD, H₂-TPR, TPO, and Raman techniques. The influence of temperature, gas hourly space velocity (GHSV), pressure, H₂/feed, nickel content and calcination temperature were studied. Optimal conditions using Taguchi method yielded maximum CH₄ selectivity (100 %) at T = 350 ºC, GHSV = 5000 mL g_cat⁻¹ h⁻¹_, P = 15 bar, and H₂/feed = 5. Under industrial reduced conditions (300 °C, 4000 mL g_cat⁻¹ h⁻¹, 1 bar, and 4.5), CO₂ conversion improved from 73.67 % to 92.84 % using optimum 15 wt% Ni catalyst and 600 °C calcination temperature. The catalyst maintained ∼90 % CO₂ conversion over 100 h without deactivation.