Chemistry of inorganic compounds – Sulfur or compound thereof – Elemental sulfur
Patent
1994-04-14
1996-08-13
Langel, Wayne
Chemistry of inorganic compounds
Sulfur or compound thereof
Elemental sulfur
423587, C01B 1702, C01B 15022
Patent
active
055453910
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the removal of hydrogen sulphide from a gaseous stream containing it and in a development thereof to the incorporation of that process as one stage of a process for generating hydrogen peroxide from hydrogen sulphide and oxygen.
Hydrogen sulphide is produced as a by-product or present as an impurity in feedstocks on a significant scale in a number of important industries, including the petroleum, natural gas, electricity generating and chemical synthesis industries. It is not only a foul smelling gas, but it is also poisonous so that it must be removed from effluent streams before they can discharged to atmosphere or into watercourses. Accordingly, the generation of hydrogen sulphide imposes upon the afore-mentioned industries additional costs of treating the gaseous effluents. It would be desirable to obtain a vendible product from the hydrogen sulphide, thereby transforming a cost-incurring waste material into a valuable feedstock.
In U.S. Pat. No. 3,311,453, to George R Lusby, hydrogen sulphide is caused to react with an aqueous alkaline solution of a salt of an anthraquinone disulphonic acid, generating solid sulphur and a reduced anthraquinone compound which is subsequently oxidised to regenerate the anthraquinone sulphonic acid and form hydrogen peroxide in solution. Recovery of sulphur from the solution can be effected easily by conventional centrifugation or filtration techniques, but recovery of hydrogen peroxide from the process is rendered more complicated because both hydrogen peroxide and the anthraquinone salt are water soluble. The proposed solution, namely conversion of soluble hydrogen peroxide to calcium peroxide, a poorly water-soluble compound, though possible, is cumbersome and requires an additional reaction step as well as the provision of lime. Moreover, the process is reported to suffer from further less apparent disadvantages, including a significant loss of anthraquinone by carry-out with precipitated calcium peroxide.
In U.S. Pat. No. 3,923,966, Lawrence G Vaughan, assigned to Du Pont has described a process in which in a first step, hydrogen sulphide is caused to react with an alkyl-substituted anthraquinone or hydrogenated derivative thereof in the presence of an amine catalyst, thereby reducing the anthraquinone to the corresponding anthra-hydroquinone and generating solid sulphur and in a second step the anthrahydroquinone is reacted with oxygen, forming hydrogen peroxide and regenerating the anthraquinone. The reaction is carried out in an organic hydrocarbon-based solvent system from which the product, hydrogen peroxide can be recovered by water-washing. It will be recognised that the Vaughan process employs the compounds which are currently employed commercially for the generation of nearly all the world's hydrogen peroxide, namely alkyl substituted anthraquinones or their hydrogenated derivatives in cyclic autoxidation (AO) processes based upon hydrogen as reductant to the exclusion of other quinones.
According to the present invention, there is provided a process for the production of elemental sulphur from hydrogen sulphide in which hydrogen sulphide is brought into contact with a reducible quinone compound dissolved in a non-aqueous solvent system in the presence of an organic amine catalyst and maintained in contact until at least some sulphur precipitates out of solution characterised in that the reducible quinone compound comprises a 2,3-dialkyl substituted naphthoquinone.
By appropriate selection of the alkyl substituents it is possible to reduce the naphthoquinone compound at a faster rate with hydrogen sulphide than using the known anthraquinone or anthrahydroquinone compounds under the same conditions.
In a related second aspect of the present invention there is provided a cyclic process for the generation of hydrogen peroxide in which in the first step hydrogen sulphide is brought into contact with a reducible quinone compound dissolved in a non-aqueous solvent system in the presence of an organic amine catalyst a
REFERENCES:
patent: 3923966 (1975-12-01), Vaughan
patent: 4581128 (1986-04-01), Plummer et al.
patent: 4592905 (1986-06-01), Plummer et al.
patent: 5180572 (1993-01-01), Plummer
Clapp Phillip A.
Evans, deceased Dennis F.
McKenna, executrix Antonia F. E.
Langel Wayne
Solvay Interox Limited
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