Catalytic reduction of SO₂ to elemental sulfur with methane over CuO_x/γ-Al₂O₃ catalysts

Copper oxide catalysts (CuOx) supported on gamma alumina (γ-Al₂O₃) were employed for the catalytic reduction of sulfur dioxide (SO₂) to elemental sulfur by methane (CH₄). The catalysts were synthesized using a straightforward sol-gel method. Initially, alumina was obtained through a precipitation technique. X-ray diffraction (XRD) analysis was conducted to confirm the formation of γ-Al₂O₃. This study aimed to investigate the impact of reaction temperature (T = 600-800 °C) and Cu loading (0-15 wt%) on SO₂ conversion and sulfur selectivity. Under the reaction conditions of 800 °C, 1 bar, SO₂ = 5000 ppm, CH₄ = 2500 ppm, gas hourly space velocity (GHSV) = 12,000 1/h, and 10 wt% Cu, the SO₂ conversion and sulfur selectivity were determined to be 95% and 94.5%, respectively. The influence of the molar feed ratio of SO₂/CH₄ = R = 0.5-3 on the 10 wt% Cu catalyst was also investigated in the temperature range of 600-800 °C. The findings revealed that when R < 2, the conversion rate increased due to higher SO₂ reduction with an excess of CH₄, but sulfur selectivity slightly decreased as a result of the formation of unwanted byproducts such as H₂S and COS. Conversely, when R > 2, SO₂ conversion significantly declined, while sulfur selectivity was enhanced due to increased consumption of CH₄.