Catalytic formation of carbonyl sulfide during warm gas clean-up of simulated coal-derived fuel gas with Pd/γ-Al2O3 sorbents

Coal gasification processes, such as the Integrated Gasification Combined Cycle (IGCC), will increase in importance due to the expanding concern over CO₂ emissions and global climate change. During the development of a Pd/γ-Al₂O₃ sorbent for warm (200 °C) fuel gas cleanup, the catalytic formation of carbonyl sulfide (COS), was observed. This is attributed to a heterogeneous reaction involving fuel gas components (CO/CO₂/H₂/H₂S/H₂O) and Pd/γ-Al₂O₃. The concentration of COS increases 200-fold when exposed to the Pd/γ-Al₂O₃ sorbent. A Langmuir–Hinshelwood reaction mechanism is proposed and a kinetic model is developed based on experimental results. The effect of γ-Al₂O₃, a common catalyst for hydrolysis of COS, and H₂O on the COS concentration is discussed.