Chemistry of inorganic compounds – Sulfur or compound thereof – Elemental sulfur
Patent
1997-11-19
2000-07-04
Griffin, Steven P.
Chemistry of inorganic compounds
Sulfur or compound thereof
Elemental sulfur
4235741, 4235762, 4235768, 502300, 502305, 502324, 502344, 502517, C01B 1704, B01D 5352, B01J 27224
Patent
active
060834714
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for oxidizing the H.sub.2 S present at a low concentration in a gas directly to sulphur by a catalytic route. It also relates to a catalyst for making use of this process.
In order to recover H.sub.2 S present at a low concentration, namely a concentration of less than 20% by volume and more particularly-,between 0.001% and 20% and very especially ranging from 0.001% to 10% by volume, in gases of various origins, it is possible to make use, in particular, of processes involving a direct catalytic oxidation of the H.sub.2 S to sulphur according to the reaction H.sub.2 S+1/2O.sub.2 .fwdarw.S+H.sub.2 O.
In such processes, the gas to be treated, containing the H.sub.2 S mixed with an appropriate quantity of a gas containing free oxygen, for example air, oxygen or else oxygen-enriched air, is passed in contact with a catalyst for oxidizing H.sub.2 S to sulphur, this contact being brought about at temperatures which are either higher than the dew point of the sulphur formed, in which case the sulphur formed is present in the vapour state in the reaction mixture resulting from the reaction, or else at temperatures which are lower than the dew point of the sulphur formed, in which case the said sulphur is deposited on the catalyst, and this requires a regeneration of the sulphur-laden catalyst at regular intervals by purging with a non-oxidizing gas which is at a temperature of between 200.degree. C. and 500.degree. C.
In particular, oxidation of H.sub.2 S to sulphur at temperatures above the dew point of sulphur, that is to say at temperatures above approximately 180.degree. C., can be carried out in contact with a catalyst consisting of titanium oxide (EP-A-0078690), of titanium oxide containing an alkaline-earth metal sulphate (WO-A-8302068), of titanium oxide containing nickel oxide and optionally aluminium oxide (EP-A-0140045), of an oxide of the titanium oxide, zirconium oxide or silica type used in combination with one or more compounds of transition metals chosen from Fe, Cu, Zn, Cd, Cr, Mo, W, Co and Ni, preferably Fe, and optionally with one or more compounds of precious metals chosen from Pd, Pt, Ir and Rh, preferably Pd (FR-A-2511663), or else of a thermally stabilized alumina used in combination with one or more compounds of transition metals such as the abovementioned, especially Fe, and optionally with one or more compounds of precious metals chosen from Pd, Pt, Ir and Rh (FR-A-2540092).
Oxidation of H.sub.2 S to sulphur, the operation being carried out at temperatures such that the sulphur formed is deposited on the catalyst, can, for its part, be performed in contact with a catalyst consisting, for example, of one or more compounds such as salts, oxides or sulphides of transition metals, for example Fe, Cu, Cr, Mo, W, V, Co, Ni, Ag and Mn, in combination with a support of the activated alumina, bauxite, silica/alumina or zeolite type (FR-A-2277877). This oxidation of H.sub.2 S with deposition of sulphur on the catalyst can also be carried out in contact with a catalyst consisting of a catalytic phase chosen from the oxides, salts or sulphides of the metals V, Mo, W, Ni and Co used in combination with an active charcoal support (French Patent Application No. 9302996 of 16.03.1993).
The catalysts such as the abovementioned, consisting of a catalytic phase based on at least one oxide, salt or sulphide of a transition metal, which phase is used in combination with a support consisting of at least one material chosen from alumina, titanium oxide, zirconium oxide, silica, zeolites, silica/alumina mixtures, silica/titanium oxide mixtures and active charcoal, which are used for the catalytic oxidation of H.sub.2 S to sulphur, still exhibit certain shortcomings on prolonged use. In particular, the catalysts in which the support is based on alumina are capable of changing with time by sulphation. As regards the catalysts in which the support consists of active charcoal, precautions must be taken during their use in order to avoid combustion of the support. Moreover, for th
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Crouzet Claude
Ledoux Marc
Nougayrede Jean
Pham Huu Cuong
Philippe Andre
Elf Exploration Production
Griffin Steven P.
Vanoy Timothy C
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