GB760955A - Production of hydrogen - Google Patents

Abstract

In the production of hydrogen by reacting a hydrocarbon in the gaseous state with steam in a first reactor to form a mixture of hydrogen, carbon monoxide and carbon dioxide, with further steam in a second reactor to convert the carbon monoxide to dioxide, and then removing the carbon dioxide, a C1-C4 hydrocarbon gas containing olefins and sulphur compounds is purified for use in the process by adding hydrogen, hydrogenating in the presence of a sulphur resistant hydrogenation catalyst, whereby the olefins are at least partially saturated and the sulphur is at least partially converted to hydrogen sulphide, and removing the hydrogen sulphide. The hydrocarbon gas may be refinery waste gas, may consist entirely of olefins and may contain any amount of sulphur. The hydrogen added may be a portion of the hydrogen product or a tail gas, e.g. from a hydrofining or hydrodesulphurization unit in an oil refinery process. The amount of hydrogen added should preferably be at least stoichiometrically equivalent to the olefins present, more preferably in 50 per cent or more excess. Hydrogenation catalysts specified are the oxides and sulphides of iron, nickel, cobalt, chromium, molybdenum, copper, manganese and tungsten, molybdates, thiomolybdates and thiotungstates. The preferred catalyst is 3-25 per cent cobalt molybdate supported on alumina. The catalyst may be mixed with bauxite, zinc oxide, clay balls or fuller's earth. The temperature of hydrogenation should be between 550 and 850 DEG F., a temperature of 600-800 DEG F. being suitable. The pressure may be atmospheric to 100 p.s.i.g., preferably 25-50 p.s.i.g. The gases may be passed alternately through 2 chambers each containing 3 beds in series, cooling water being injected between each bed. The product gases may be passed in heat exchange with the cold feed gases. The fluidized bed technique may be employed and inert heat transfer solids such as mullite, corundum and alundum may be circulated through the bed. The hydrogen sulphide produced may be removed by washing with caustic soda. Alternatively or in addition the hydrogen sulphide may be moved by the use of zinc oxide in admixture with the hydrogenation catalyst. The resulting hydrocarbon may be reacted with steam in the presence of nickel oxide first at 1000 DEG F. and then at 1600 DEG F. In the first stage of the catalytic reforming process the gas may be passed through a plurality of annular catalytic reaction zones comprising inner and outer tubes heated in furnace (the Fig., not shown), the gases being passed into the annular space and out through the inner tube. The resulting gas mixture, consisting of hydrogen, steam, carbon monoxide, and carbon dioxide may be passed over iron oxide at 750 DEG C. for the interaction of steam and carbon monoxide to produce carbon dioxide. The resulting gas may be cooled to remove water vapour, and scrubbed with 10-20 per cent mono-ethanolamine solution to remove carbon dioxide.