Method for catalytic binding of free oxygen in gases containing free hydrogen and hydrogen sulphide

摘要

Oxygen is removed from gases containing free hydrogen in an amount at least equivalent to the amount of free oxygen and also containing hydrogen sulphide and possibly hydrocarbons or carbon dioxide, by bringing the gas at a temperature below 450 DEG C. into contact with a catalyst comprising at least one of the metals Cr, Mo or W, a promoter consisting of at least one metal Fe, Co, Ni, Cr, U, V (different from the catalyst) and a carrier consisting of at least one of alumina, silica gel, synthetic and natural aluminium silicate and magnesium oxide, the catalyst and promoter being predominantly in the form of their sulphur compounds and the atomic ratio of metals of the catalyst, metals of the promoter and metals (including silicon) of the carrier being 0.5-1.5: 0.5-1.5: 10. In Fig. 1, the gas to be freed of oxygen is led in at 1 through preheaters 2 and 3 and enters catalyst chambers 5a, 5b, 5c, by valves 4a, 4b, 4c. Preferably two of the chambers are employed in series whilst the third is being regenerated. The oxygen freed gas leaves by valves 16a, b, c, through heat exchanger 2 and pipe 17. The chamber undergoing regeneration, say 5c, is first purged with nitrogen, flue gas or steam introduced by valve 19c from line 18 which leaves through line 21. Air is then introduced from line 22, passed through a combustion chamber 25 where gas entering at 26 is burnt to give a mixture of air and flue gas at 300-550 DEG C. This mixture is introduced into chamber 5c to burn off carbonaceous deposits, the gas leaving by line 21, until combustion has started when the off gas is recycled by line 30 through the combustion chamber 25. Finally the air is shut off and the purge gas from line 18 recommenced. The regenerated chamber 5c is then put back into operation. The catalyst may be prepared in the manner shown in the following examples: (1) Aluminium grains are activated with mercury nitrate and dissolved in acetic acid and the decanted solution is mixed with a cobalt nitrate solution, after which a mixed solution of ammonium molybdate and ammonia in water are added slowly with stirring. The precipitate is washed dried, pelleted and calcined in air, after which the catalyst is activated in the reactor by the passage of hydrogen at 100-450 DEG C. to reduce the metal oxides followed by a gas containing hydrogen sulphide to form metal sulphides. The catalyst is pyrophoric. (2) an ammoniated solution of ammonium molybdate is added to a solution of aluminium and cobalt nitrates and the precipitate treated as in (1) above. (3) Similar to (2) except that sodium tungstate replaces the ammonium molybdate. (5) As in (2) except that uranium nitrate is present in the aluminium and cobalt nitrate solutions. (6) Magnesium nitrate replaces the aluminium nitrate of (2). (7) A synthetic alumina silica cracking catalyst prepared from aluminium nitrate and waterglass in known manner is employed as carrier and is treated with ammonium molybdate solution to form a homogeneous mass. The mass is air dried, and impregnated with a cobalt nitrate solution dried, shaped and treated as in (1) above. The catalyst can also be employed in an apparatus for determining the oxygen content of the gases of the present kind as shown in Fig. 3. Gas enters at 41, is dried in towers 44-46 and passes to a cooling coil 47 to remove heavier hydrocarbons which might affect the catalyst. The gas then passes to reactor unit 52 which consists of a steel tube 53 containing the catalyst, surrounded by a jacket 54 containing a liquid having a suitable boiling point to maintain the reactor at 75-250 DEG C. The gas, preheated in coil 58 passes through the tube 53 and leaves by line 60 to enter a metal coil 66 and psychrometer 67 before finally leaving via flow meter 43. The coil and psychrometer are maintained in an electrically controlled water bath 61. The psychrometer is shown in Fig. 4. Gas is lead to a container 68 having a pocket 69 containing a thermocouple. The gas then passes to container 70 to which an inner container 71, connected to a water vessel 72, is joined. Gas enters inner container 71 through holes 73, to contact a porous fabric stocking 75 dipping into the water in 72. A thermocouple is also placed in inner container 71 and the terminals connected to a millivoltmeter which may be calibrated to read the moisture content (and hence the oxygen content) of the gas. Alternatively the water produced may be measured gravimetrically, by a dew point hydrometer, or by measuring the electric conducting capacity of an electrolyte in contact with p the gas. If hydrogen is absent from the gas to be analysed it is added by line 78 (Fig. 3). Specification 587,070 is referred to.