GB1332337A - Reducing total sulphur content of claus offgases - Google Patents

Abstract

1332337 Gas separation; sulphur content reduction SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 15 Dec 1970 [21 Sept 1970]. 59501/70 Heading C1A The total sulphur content of Claus off gases containing H 2 S, SO 2 and also CS 2 and/or COS is reduced by (1) passing the off gases, together with H 2 and/or CO containing gas at a temperature above 175‹ C. over a Group VI and/or Group VIII metal catalyst supported on an inorganic oxide; (2) subsequently or simultaneously contacting the off gases with a solid catalyst to convert CS 2 and/or COS to H 2 S; (3) removing H 2 S by contacting with an absorbent or adsorbent. The H 2 and/or CO containing gas, e.g. town gas, water gas, synthesis gas, H 2 -rich off-gases, preferably contains at least 20 vol. per cent of H 2 and is used in an amount such that the H 2 : SO 2 ratio in the gas mixture is 3 to 15 : 1, The reduction catalyst (a Group VI and/or VIII metal) may be used in oxidic or sulphided form. Sulphiding may be effected by an H 2 /H 2 S mixture or in situ by means of the Claus off-gases. Specified CS 2 and/or COS conversion catalysts are alumina, bauxite, activated clay, aluminium phosphate, thoria and MgCl 2 . The alumina may be impregnated with alkali metal phosphate. The two catalysts may be used at substantially the same temperature. Simultaneous contacting of the Claus off-gases with the two catalysts may be carried out using a mixture of catalysts in a fixed acceptor bed, or by arranging two or more separate beds of single catalysts on a single reactor. The H 2 S absorbent may be solid, e.g. carbon, metal oxides or liquid e.g. alkanolamines, amines, ammonia, metal carbonate solutions. The liquid absorbent may contain an oxidant and/or a catalyst (many specified) to form elemental S. In an example, Claus off-gas mixed with H 2 is passed over sulphided Co/Mo/Al 2 O 3 at 222‹ C., then over activated alumina at 223‹ C. and finally over active carbon at 130‹ C.