Oxidation of hydrogen sulfide

Sulfur, another inorganic petrochemical, is obtained by the oxidation of hydrogen sulfide 2H2S + O2 — 2H2 0 + 2S. Hydrogen sulfide is a constituent of natural gas and also of the majority of refinery gas streams, especially those off-gases from hydrodesulfurization processes. A majority of the sulfur is converted to sulfuric acid for the manufacture of fertilizers and other chemicals. Other uses for sulfur include the production of carbon disulfide, refined sulfur, and pulp and paper industry chemicals. 

Certain of the above reactions are of practical importance. The oxidation of hydrogen sulfide in a flame is one means for producing the sulfur dioxide required for a sulfuric acid plant. Oxidation of hydrogen sulfide by sulfur dioxide is the basis of the Claus process for sulfur recovery. The Claus reaction can also take place under mil der conditions in the presence of water, which catalyzes the reaction. However, the oxidation of hydrogen sulfide by sulfur dioxide in water is a complex process leading to the formation of sulfur and polythionic acids, the mixture known as Wackenroeder s Hquid (105). 

A derivative of the Claus process is the Recycle Selectox process, developed by Parsons and Unocal and Hcensed through UOP. Once-Thm Selectox is suitable for very lean acid gas streams (1—5 mol % hydrogen sulfide), which cannot be effectively processed in a Claus unit. As shown in Figure 9, the process is similar to a standard Claus plant, except that the thermal combustor and waste heat boiler have been replaced with a catalytic reactor. The Selectox catalyst promotes the selective oxidation of hydrogen sulfide to sulfur dioxide, ie, hydrocarbons in the feed are not oxidized. These plants typically employ two Claus catalytic stages downstream of the Selectox reactor, to achieve an overall sulfur recovery of 90—95%. 

This process is used to treat gas streams containing high concentrations of H2S. The chemistry of the units involves partial oxidation of hydrogen sulfide to sulfur dioxide and the catalytically promoted reaction of hh.S and SO2 to produce elemental sulfur. The reactions are staged and arc. is lollows ... 

Currently, sulfur is mainly produced by the partial oxidation of hydrogen sulfide through the Claus process. The major sources of hydrogen sulfide are natural gas and petroleum refinery streams treatment operations. It has been estimated that 90-95% of the world s recovered sulfur is produced through the Claus process. Typical sulfur recovery ranges from 90% for a lean acid gas feed to 97% for a rich acid gas feed. ... 

Trace amounts of disulfane have been obtained in the gas phase by recombination of HS radicals generated by oxidation of hydrogen sulfide by oxygen atoms which in turn are produced from molecular oxygen in a microwave discharge [25] ... 

Finally, it should be mentioned that polysulfides are formed on oxidation of hydrogen sulfide ions in water, either electrochemically [111] or by oxidation with molecular oxygen ... 

Selective oxidation of hydrogen sulfide to elemental surfur and ammonium thiosulfate using VO, /Ti02 catalysts... 

The Iodometric method has also been utilized in analyzing hydrogen sulfide in the air (EPA 1978). The method is based on the oxidation of hydrogen sulfide by absorption of the gas sample in an impinger containing a standardized solution of iodine and potassium iodide. This solution will also oxidize sulfur dioxide. The Iodometric method is suitable for occupational settings. The accuracy of the method is approximately 0.50 ppm hydrogen sulfide for a 30-L air sample (EPA 1978). 

Chiu G, Meehan EJ. 1977. Monodisperse sulfur sols from the air oxidation of hydrogen sulfide solutions. Journal of Colloid and Interface Science 62 1-7. 

Kotronarou A, Mills G, Hoffmann MR. 1992. Oxidation of hydrogen sulfide in aqueous solution by ultrasonic irradiation. Environ Sci Technol 26 2420-2428. 

Millero FJ, LeFerriere A, Fernandez M, et al. 1989. Oxidation of hydrogen sulfide with H202 in natural waters. Environ Sci Technol 23(2) 209-213. 

Sharma VK, Smith JO, Millero FJ. 1997. Ferrate(VI) oxidation of hydrogen sulfide. Environmental Sciences and Technology 31 2486-2491. 

Katasulf A process for removing hydrogen sulfide and ammonia from coke-oven gas, developed by IG Farbenindustrie in Germany in the 1920s. The basic reaction involved is the catalyzed oxidation of hydrogen sulfide to sulfur dioxide and water at approximately 420°C ... 

The aerobic bacteria responsible for this oxidation of hydrogen sulfide to sulfuric acid belong to the aerobic and autotrophic Thiobacillus family (Sand, 1987 Milde et al., 1983). These bacteria may be active at rather low pH values. Thiobacillus concretivorus is active at pH values between about 0.5 and 5 and may produce solutions of sulfuric acid up to about 7%. To be active, it requires that other species of the Thiobacillus family bring down the pH value. 

Bandosz TJ. On the adsorption/oxidation of hydrogen sulfide on unmodified activated carbons at ambient temperatures,/. Coll. Interface. 2002, 246,1-20. 

The need to remove sulfur compounds from petroleum arises not only from the objectionable odor that the thiols impart to petroleum products but also from the instability which sulfur compounds appear to promote in petroleum products. For example, free sulfur, which can be formed in a product by the oxidation of hydrogen sulfide ... 

Fume, J. et al., Oxidation of hydrogen sulfide and methanethiol to thiosulfate by rat tissues a specialized function of the colonic mucosa, Biochem. Pharmacol., 62, 255-259, 2001. 

A layer of coexistence of oxygen and hydrogen sulfide (C-layer) was observed in the earliest hydro chemical studies in the Black Sea, and it was assumed that oxidation of hydrogen sulfide takes place mainly by oxygen reaction within this layer [23-26]. During the RV Knorr 1988 expedition, it was found that oxygen concentrations measured with the Winkler technique were significantly lower than found earlier [16,27]. This fact of absence of... 

The formation of sulfur intermediates is both chemically and biologically mediated. Oxidation of hydrogen sulfide with oxygen and Fe(Mn) oxyhy-droxides and sulfate reduction are the main processes responsible for sulfur intermediates formation in the euxinic water columns, except for elemental sulfur, which is formed only during hydrogen sulfide oxidation. Chemically mediated reactions of thiosulfate formation are elemental sulfur(polysulfides)... 

L.M. Knijff, P.H. Bolt, R. van Yperen, A.J. van Dillen, J.W. Geus, Production of nickel-on-alumina catalysts from preshaped bodies K.P. de Jong, Deposition-precipitation onto preshaped carrier bodies — possibilities and limitations P.J. van den Brink, A. Scholten, A. van Wageningen, M.D.A. Lamers, A.J. van Dillen, J.W. Geus, The use of chelating agents for the preparation of iron oxide catalysts for the selective oxidation of hydrogen sulfide, all in Preparation of Catalysts V, Elsevier, Amsterdam, 1991. 

Results presented in this paper show that differences in the chemical composition of sewage sludge derived adsorbents lead to differences in their performance as adsorbents of acidic gases. It has been demonstrated that however some adsorption centers can be common for both gases, there are surface features on the sample pyrolized at 950 C which favor oxidation of hydrogen sulfide to elemental sulfur. This is likely due to the catalytic action of the iron species. When adsorption of SOj takes part calcium species play a crucial role. Surface chemistry has also its effect on the physical form of sulfur deposited on the surface. It is either rhombic or monoclinic depending on the pyrolysis temperature and chemical changes imposed by heat treatment. 

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