Oxidative desulfurization processes

Oxidative Desulfurization Process. Oxidative desulfurization of finely ground coal, originally developed by The Chemical Constmction Co. (27,28), is achieved by converting the sulfur to a water-soluble form with air oxidation at 150—220°C under 1.5—10.3 MPa (220—1500 psi) pressure. More than 95% of the pyritic sulfur and up to 40% of the organic sulfur can be removed by this process. 

Aida, T., Yamamoto, D., Iwata, M., and Sakata, K. Development of oxidative desulfurization process for diesel fuel. Reviews on Heteroatom Chemistry, 2000, 22, 241. 

Shiraishi, Y., Hirai, T., and Komasawa, I. Oxidative desulfurization process for light oil using titanium silicate molecular sieve catalysts. Journal of Chemical Engineering of Japan, 2002, 35, 1305. 

Figure 15.8. UOP/Eni oxidative desulfurization process scheme. HCBN (hydrocarbon) stands for any suitable hydrocarbon refinery stream. Adapted from Molinari et al. ...

The oxidants used in this reaction are hydrogen peroxide, peracids or organic peroxides, but the high cost of H2O2 or organic hydroperoxides makes the economics unfavourable in comparison with the traditional hydro-desulfurization process. In order to overcome this limitation, Eni/UOP jointly developed a new oxidative desulfurization process in which the hydroperoxide is directly produced in the reaction medium and in this way ULSD production can become economically convenient. A concept scheme of the process is given in Fig. 15.8. 

Shiraishi et al. " explored a new two-stage oxidative desulfurization process of light oil, effected by a combination of photochemical reaction and organic two-phase liquid-liquid extraction. The first consists of the transfer of the sulfur-containing compounds from the light oil to an aqueous-soluble... 

Flex DS An oxidative desulfurization process for decontaminating and upgrading crude oil. The oxidant is an alkyl hydroperoxide and the catalyst an organic titanium complex. Developed from 2007 by Auterra, Malta, NY, formerly called Applied NanoWorks. Funded by a Canadian Oil Sands company, piloted but not yet commercialized. 

Exhaust emissions of CO, unbumed hydrocarbons, and nitrogen oxides reflect combustion conditions rather than fuel properties. The only fuel component that degrades exhaust is sulfur the SO2 concentrations ia emissions are directly proportional to the content of bound sulfur ia the fuel. Sulfur concentrations ia fuel are determined by cmde type and desulfurization processes. Specifications for aircraft fuels impose limits of 3000 —4000 ppm total sulfur but the average is half of these values. Sulfur content ia heavier fuels is determined by legal limits on stack emissions. 

The latter reaction has been studied numerous times because of its relevance for the autoxidation of hydrogen sulfide in seawater and other aqueous systems [112, 113]. 8ince the polysulfide ions can be further oxidized to elemental sulfur which precipitates from the solution, these reactions are the basis for several industrially important desulfurization processes (e.g., the 8tretford, 8ulfolin, Lo-Cat, 8ulFerox, and Bio-8R processes) [114] ... 

This process of aging is believed to be critical in the development of delayed neuropathy, after NTE has been phosphorylated by an OP (see Chapter 10, Section 10.2.4). It is believed that most, if not all, of the B-esterases are sensitive to inhibition by OPs because they, too, have reactive serine at their active sites. It is important to emphasize that the interaction shown in Fignre 2.11 occurs with OPs that contain an oxon group. Phosphorothionates, which contain instead a thion group, do not readily interact in this way. Many OP insecticides are phosphorothionates, but these need to be converted to phosphate (oxon) forms by oxidative desulfuration before inhibition of acetylcholinesterase can proceed to any significant extent (see Section 2.3.2.2). 

Desulfurization processes are absolutely necessary for producing clean fuels. Possible strategies to realize ultradeep suffiirization currently include adsorption, extraction, oxidation, and bioprocesses. Oxidative desulfurization (ODS) combined with extraction is considered one of the most promising of these processes [13]. Ultradeep desulfurization of diesel by selective oxidation with amphiphilic catalyst assembled in emulsion droplets has given results where the sulfur level of desulfurized diesel can be lowered from 500 ppm to about 0.1 ppm without changing the properties of the diesel [12]. 

Sweetening of petroleum products implies the removal of dissolved free sulfur and its compounds like hydrogen sulfide, and mercaptans in order that the product has no bad odour and does not tend to cause corrosion. The removal of these is accomplished by oxidation processes, solvent processes or catalytic desulfurization processes. 

The second type of biological process is a direct treatment process, in which bacteria oxidize the sulfur species. This oxidative desulfurization reaction is carried out in the presence of an electron acceptor (such as nitrate, NOs ), a source of carbon (such as carbon dioxide or I ICO, ), and a source of reduced nitrogen (such as ammonia). The... 

The desulfurization process reported by the authors was a hybrid process, with a biooxidation step followed by a FCC step. The desulfurization apparently occurs in the second step. Thus, the process seems of no value, since it does not remove sulfur prior to the FCC step, but only oxidizes it to sulfoxides, sulfones, or sulfonic acids. The benefit of such an approach is not clearly outlined. The benefit of sulfur conversion can be realized only after its removal, and not via a partial oxidation. Most of the hydrotreatment is carried out prior to the FCC units, partially due to the detrimental effect that sulfur compounds exert on the cracking catalyst. It is widely accepted that the presence of sulfur, during the regeneration stage of the FCC units, causes catalyst deactivation associated with zeolite decay. In general terms, the subject matter of this document has apparent drawbacks. 

The desulfurization process can be carried out either, in a dedicated reactor, or within a simple storage vessel, or during transportation (in pipelines) or intermediate processing vessels. Nutrients addition, pH, and aeration are adjusted as necessary. Multiple stages can be added to the reaction to enhance the sulfur removal process and decrease the reaction time below the probable 300 h required. The produced sulfates are removed by the addition of agents such as alkaline calcium, magnesium, aluminum, barium, and metal compounds such as oxides, hydroxides, and carbonates. 

Bischoff A flue-gas desulfurization process. A slurried mixture of lime and limestone is sprayed into the gas in a spray tower. The calcium sulfite in the product is oxidized by air to calcium sulfate. Used in Europe in the 1980 s. Lurgi Bishoff is a part of the Lurgi group. The process is offered by Lentjes, Germany, a subsidiary of Lurgi. 

ChemicoB-Basic A flue-gas desulfurization process using magnesium oxide slurry. 

Desox A flue-gas desulfurization process in which limestone slurry absorbs the sulfur dioxide, forming calcium sulfite. This is then oxidized to saleable gypsum ... 

Dowa A flue-gas desulfurization process in which the sulfur dioxide is absorbed in a basic aluminum sulfate solution. The product solution is oxidized with air and reacted with limestone to produce gypsum. Developed by the Dowa Mining Company, Japan, in the early 1980s. In 1986 it was in use in nine plants in Japan and the United States. 

Dual Alkali A flue-gas desulfurization process. The sulfur dioxide is absorbed in aqueous sodium hydroxide and partially oxidized, and this liquor is then treated with calcium hydroxide to regenerate the scrubbing solution and precipitate calcium sulfate. Developed by Combustion Equipment Associates and Arthur D. Little. 

ELCOX A flue-gas desulfurization process in which the sulfur dioxide is oxidized elec-trochemically to sulfuric acid, using an organometallic catalyst (e.g., cobalt phthalocyanine) adsorbed on activated carbon. Developed by the Central Laboratory of Electrochemical Power Sources, Sofia, Bulgaria. 

FW-BF [Foster Wheeler-Bergbau-Forschung] A dry flue-gas desulfurization process that combines the sulfur removal system of Bergbau-Forschung, which uses a carbon adsorbent, with the Foster-Wheeler process for oxidizing adsorbed sulfur to sulfuric acid. 

LIMB [Lime/limestone injection into a multi-stage burner] A flue-gas desulfurization process used in Germany and Finland. Dry, ground limestone is injected directly into the combustion chamber. This reacts with the sulfur dioxide, and the dry particulate product is collected downstream together with the ash. The process is suitable only for those systems which limit the maximum combustion temperature by staging, in order to minimize the production of oxides of nitrogen. 

Reinluft A flue-gas desulfurization process using coke. The carbon acts as a catalyst for the oxidation of the sulfur dioxide to sulfur trioxide in the presence of water, and the sulfur trioxide is retained on the coke. The coke is regenerated in another vessel by heating with a hot gas stream, which reduces the sulfur trioxide back to sulfur dioxide and expels it for use in sulfuric acid manufacture. The key to this process is the inexpensive adsorbent. Developed by Reinluft GmbH and Chemiebau Dr. A. Zieren GmbH, and marketed as the Reinluft (Clean Air) Process. Four plants had been built by 1985. 

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