Study On CoMo Hydrodesulfurization Catalyst For The Claus Tail Gas

The industrial method for sulfur recovery is Claus process, kinds of sulfide species are contained in the Claus tail gas, which can not meet the national emission standard until it is treated. So, hydrodesulfurization for the Claus tail gas is an important topic in petroleum chemical industry. SCOT process is employed to treat the gas for converting sulfur dioxide into hydrogen sulfide in most of Chinese sulfur recovery factories. In such process ,the reported operating temperature for the hydrogenation catalyst is 250-300℃, though actual temperature is 300℃ . The temperature of the tail gas from sulfur recovery device is usually 120-130℃. So the Claus tail gas has to be heated to reach the catalytic reaction temperature before hydrogenation reaction. When the catalytic reaction is completed, the tail gas should be cooled below 42℃ before ihtaking the absorption unite. Therefore, it is of realistic importance to reduce the operating temperature of such hydrodesulfurization catalyst.CoMo/Al₂O₃ catalyst is common in sulfur dioxide hydrodesulfurization reaction. â‘ In present work we designed and built a catalyst evaluation system and studied the influence of the main active components, their best amount, supports, preparing skill on catalytic activity. We obtained the catalyst with operating temperature below 300℃.â‘¡The experiment shows that MoS₂ is the main active component. Co sulfide species also have some activity, but are mainly responsible for better dispersion of Mo species on the alumina surface, as a result, more active centers can be formed. â‘¢ The prior formation of MoS₂ can enhance the catalytic activity with the same CoO and MoO₃ amount. The optimum catalyst in our work contains 10-15 % MoO₃ and 1-5 % CoO, which can convert 100% SO₂ into H₂S in 280℃. â‘£ Al₂O₃, TiO₂ and SiO₂ as catalyst supports are also investgated. The result shows that CoMo/TiO₂ catalyst has a lower catalytic activity than COMO/Al₂O₃, and then CoMo/SiO₂ catalyst has a low SO₂ conversion but a excellent H₂S selectivity at low temperature.As-prepared catalysts was characterized by XRD technique. The result shows that MoO₃ can disperse well when its loading capacity is below 13.5 %, but the aggregation of MoO₃ cause obvious reduction of catalytic activity once beyond 13.5 %. The addition of CoO is beneficial to the better dispersion of MoO₃ .