Hydrogen Sulfide Partial Oxidation

Here OTMs may present the opportunity to develop a single stage Claus process. In the well estabUshed Claus process [120], hydrogen sulfide is initially burned in air to give SO2 via  

Additionally, it has been shown that both molybdenum and tungsten disulfides can act as catalytic sites [122] for maintaining this equilibrium. Hence if hydrogen could be selectively oxidized to steam in an OTM, equilibrium (7.42) could be continuously shifted to the right, resulting in the same reaction product in a single step that the Claus process gives in two steps. 

Using insights derived from the above electrochemistry, OTMs have been operated [15] possessing the general composition where B=A1 

Hydrogen sulfide conversions of up to 62 mL min i were obtained at 900 °C with a 40% H2S stream flowing at 200 mL mimL This corresponded to an equivalent current density of 710 mA cm and close to 550% removal beyond that expected from thermodynamic hydrogen sulfide thermal decomposition at this 

An interesting observation was that the presence of metal surface catalysts for the hydrogen oxidation reaction appeared to have little effect upon performance. 

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Hydrogen sulfide partial oxidation is an exothermic process for converting hydrogen sulfide into elemental sulfur and water. A Claus plant (named for London chemist Carl Friedrich Claus) is a typical example of hydrogen... 

Table 10.14 provides some essential information concerning the production of hydrogen by partial oxidation of a VR. By-products are carbon dioxide and hydrogen sulfide. 

The saturated, cleaned raw synthesis gas from a Texaco partial oxidation system is first shifted by use of a sulfur resistant catalyst. Steam required for shifting is already present ia the gas by way of the quench operation ia the generator. The shifted gas is then processed for hydrogen sulfide and carbon dioxide removal followed by Hquid nitrogen scmbbiag. 

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. ... 

This process includes two main sections the burner section with a reaction chamber that does not have a catalyst, and a Claus reactor section. In the burner section, part of the feed containing hydrogen sulfide and some hydrocarbons is burned with a limited amount of air. The two main reactions that occur in this section are the complete oxidation of part of the hydrogen sulfide (feed) to sulfur dioxide and water and the partial oxidation of another part of the hydrogen sulfide to sulfur. The two reactions are exothermic ... 

Slimane, R.B., Lau, F.S., Khinkis, M., Bingue, J.R, Saveliev, A.V., Kennedy, L.A. 2004a. Conversion of hydrogen sulfide to hydrogen by superadiabatic partial oxidation thermodynamic consideration. Int J Hydrogen Energy 29 1471-1477. 

In 1883, the Claus process for producing sulfur from hydrogen sulfide through partial combustion over an iron oxide catalyst was patented. It enjoyed limited success as a method for producing sulfur over the following 50 years, despite a number of process improvements. Its primary use arose with the need for a means to remove the sour component of sour gas for processing reasons and for environmental compatibility. 

Sulfur Plant Acid gas (hydrogen sulfide and carbon dioxide) is fed to a sulfur plant, where the hydrogen sulfide is converted to elemental sulfur by partial oxidation with air. 

Certain catalytic systems based on the use of cobalt and molybdenum offer good resistance to sulfur. On the other hand, they cannot guarantee advanced conversioa of carbon monoxide, of which a few per cent remain in the effluent obtained. Their value resides in the simplification of the purification schemes for effluents produced by the partial oxidation of sulfiir-containing feeds. This is because they do not require prior removal of hydrogen sulfide, which can be removed subsequently in a angle add gas separation. 

The Rectisol process [667], [707], [711]-[715] seems to be the prime choice in partial oxidation plants. The process, invented by Lurgi and developed further by Linde, operates with chilled methanol, a cheap and readily available solvent, in which carbon dioxide, hydrogen sulfide and carbonyl sulfide (COS) are readily soluble at low operating temperatures of below - 30 °C. The Henry absorption coefficient for H2S is about six times higher than for C02-... 

Methanation as final purification for the raw gas from partial oxidation was proposed by Topsoe [739]. In this case the shift conversion is carried out in two stages with a special sulfur-tolerant shift catalyst followed by removal of hydrogen sulfide and carbon dioxide in an acid gas removal unit. Because of the potential danger of a sulfur break-through causing poisoning, the normal copper - zinc - alumina catalyst is usually not applied, which is surprising as the same risk exists in partial oxidation based methanol plants for the similarly composed methanol catalyst. 

Corrosion by hydrogen sulfide in partial oxidation plants can be controlled by the use of austenitic steels, but special care to ensure proper stress relief of welds is advisable to avoid stress corrosion cracking in these plants caused by traces of chlorine sometimes present in the feed oil. 

The nature of the active site in beta-amylase is not unambiguously known for enzymes from different sources. Early experiments on purified barley and on malted barley first indicated, from studies of the modification of the enzyme with nitrous acid and ketene, that free tyrosine and sulfhydryl groups are essential for activity, whereas free a-amino groups are not. The importance of the sulfhydryl groups was emphasized by the partial recovery of activity of the modified or oxidized enzyme (that is, treated with nitrous acid, iodine, phenyl mercuribenzoate, ferricyanide, and cupric ions) when it was treated with hydrogen sulfide or cysteine. Barley feeto-amylase (not highly purified) has been reported to contain 12—15 sulfhydryl groups per molecule by titration with p-chloromercuribenzoate, and the loss of free sulfhydryl content by treatment with L-ascorbic acid in the presence of cupric ions was found to be directly related to the loss of activity. 

Combinations of physical and chemical absorption are also used, as in Shell s Sulfinol process in which a mixture of diisopropanolamine and sulfolane in water is utilized. For the hydrogen sulfide-free gases from the steam-reforming process, chemical scrubbing with activated potassium carbonate solutions or alkanolamines is preferred. In the case of hydrogen sulfide-containing gases from the partial oxidation process, physical absorption alone or in combination with chemical absorption is preferred. 

Steijns, M. and Mars, P. (1974). The role of sulfur trapped in micropores in the catalytic partial oxidation of hydrogen sulfide with oxygen./. Catal, 35, 11-17. 

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