Catalytic Hydro-conversion Of Carbonyl Sulfide In Coal Gas

The removal of sulfur specises is crucial in Integrated Gasification Combined Cycle (IGCC) technology which is regarded to be the most promising technology due to the high efficiency and low pollution features.The sulfur-containing compounds in the coal gas mainly include hydrogen sulfide and organic sulfur,such as carbonyl sulfides,carbon bisulfide and so on.However,organic sulfur removal is not so easy,which is difficult to reach the requirements of fine desulfurization.Hydrodesulfurization is thought of the most appropriate method on removal of carbonyl sulfide because it not only has high desulfurization precision,simple operation,but also H₂ in the gas can be used directly without additional gas source.Transition metal nickel and molybdenum are both effective active components for carbonyl sulfide hydrodesulfurization reaction andγ-Al₂O₃ exclusively act as carrier.Because there is strong intercation betweenγ-Al₂O₃ and metal oxides,it is easy to form Al-O-Mo phase which is not propitious to presulfurize and reduces the conversion of COS.This problem can be solved using sulfide as precursor to prepare catalyst.Due to the diversity of coal and the difference in the process of caol gasification,the composition of the product of coal gasification will be correspondingly changes;The impact of the gas atmosphere composition on the removal of COS is less reported.In order to develop the technology to remove organic sulfur,it is necessary to study the impact of the coal gas composition on catalytic hydro-conversion of carbonyl sulfide in coal gas.(1) Metal sulfides catalysts are prepared by incipient-wetness impregnation method using ammonium tetrathiomolybdate(ATTM) as precursor and commercial coconut shell activated carbon as catalyst carrier and applied to hydro-conversion behaviors study of carbonyl sulfide in coal gas to find out the most suitable active component for catalytic hydro-conversion of carbonyl sulfide.(2) Select MoS₂ as active component to study the relationship between the supports' characteristic and the activities of catalyst for COS removal.(3) Catalytic hydrogenation conversion of carbonyl sulfide(COS) in coal gas to hydrogen sulfide(H₂S) on MoS₂/Al₂O₃ was systematically investigated with transient response method in the present work.In order to understand the conditions of mutual transformation between COS and H₂S. It is found that MoS₂ has a high catalytic activity for organic sulfur hydrogenation conversion,and Ni-doping could promote the dispersion of MoS₂ on carbon surface,it is easy to generate more active sites for catalytic hydro-conversion of carbonyl sulfide.In the scope of supports we studied,we find that the activated carbon with high area as a carrier is helpful to disperse the active component and has a high conversion of COS,followed by metal oxides, molecular sieves less;It is also found that the coal gas composition affected the catalytic hydrogenation remarkably.The increasing of CO concentration could decrease the hydro-conversion efficiency of COS enormously,especially at low temperature,resulting from chemical equilibrium shift and the reaction between MoS₂ and CO;Under the hydrogenation condition,H₂ reacted with MoS₂ leading to partial S loss.Mutual conversion of CO and H₂S facilely took place on MoS₂ and the conversion were highly dependent on the reaction temperature employed:in the temperature range of 120-250℃,H₂S reacted with CO to form COS,with maximum conversion at 220℃,when the temperature was over 250℃,the transformation of COS to H₂S began to occur,and the complete catalytic hydro-conversion was achieved approximately at 320℃.