Desulfurization complexes

Other Uses. Other uses include intermediate chemical products. Overall, these uses account for 15—20% of sulfur consumption, largely in the form of sulfuric acid but also some elemental sulfur that is used directly, as in mbber vulcanization. Sulfur is also converted to sulfur trioxide and thiosulfate for use in improving the efficiency of electrostatic precipitators and limestone/lime wet flue-gas desulfurization systems at power stations (68). These miscellaneous uses, especially those involving sulfuric acid, are intimately associated with practically all elements of the industrial and chemical complexes worldwide. 

Tungsten hexachloride and molybdenum pentafluoride desulfurize 2-methylthiirane to propene (72DOK(207)899) and a ruthenium(II) complex desulfurizes thiirane (73JA4758). 

Triazin-5-One, 3-thioxo-alkylation, 3, 408 desulfurization, 3, 416 mass spectra, 3, 397 metal complexes, 3, 456 methylation, 3, 408 reactions... 

Progress and prospects in hydrogenation, hydrogenolysis, and desulfurization of thiophenes with soluble metal complexes 98ACR109. 

It should be noted, however, that this reaction sequence may be different from what may actually be occurring in the reactor. The reactions proceed at different rates depending on the process variables. Hydrodesulfurization of complex sulfur compounds such as dibenzothiophene also occurs under these conditions. The desulfurized product may crack to give two benzene molecules ... 

Desulfurization of FCC feedstocks reduces the sulfur content of FCC products and SOX emissions. In the United States, road diesel sulfur can be 500 ppm (0.05 wt%). In some European countries, for example in Sweden, the sulfur of road diesel is 50 ppm or less. In California, the gasoline sulfur is required to be less than 40 ppm. The EPA s complex model uses sulfur as a controlling parameter to reduce toxic emissions. With hydroprocessed FCC feeds, about 5% of feed sulfur is in the FCC gasoline. For non-hydroprocessed feeds, the FCC gasoline sulfur is typically 10% of the feed sulfur. 

Metal polysulfido complexes have attracted much interest not only from the viewpoint of fundamental chemistry but also because of their potential for applications. Various types of metal polysulfido complexes have been reported as shown in Fig. 1. The diversity of the structures results from the nature of sulfur atoms which can adopt a variety of coordination environments (mainly two- and three-coordination) and form catenated structures with various chain lengths. On the other hand, transition metal polysulfides have attracted interest as catalysts and intermediates in enzymatic processes and in catalytic reactions of industrial importance such as the desulfurization of oil and coal. In addition, there has been much interest in the use of metal polysulfido complexes as precursors for metal-sulfur clusters. The chemistry of metal polysulfido complexes has been studied extensively, and many reviews have been published [1-10]. 

EtsP S = PEt3 Scheme 44 Desulfurization of transition metal polysulfido complexes... 

In addition, it has been reported that the rhenium polysulfido complex [Re(Cp )(S3)(S4)] (Cp =77 -C5Me5) undergoes desulfurization with Ph3P to... 

Reports on a few other desulfurization organisms also exists, including Nocardia [98], S. acidocaldarius [5,99], Arthrobacter [100], R. toruloides, [101], C. elegans [102], Klebsiella spp. [103], and Alcaligenes xylosoxydans strain deposited with the ATCC under PTA-4669 [104], A S. acidocaldarius species was reported to desulfurize DBT and produce sulfate [5], A similar strain was later used to study the DBT desulfurization [99] in complex media using tryptone however, the authors reported that the strain was not active when grown on sucrose. It was apparently inhibited by DBT and also affected by the interface in oil-water mixtures [105],... 

Engineered biocatalysts with altered specificity have been developed. A Rhodococcus strain capable of DBT as well as BT desulfurization has been developed by cloning dsz genes into a strain-containing BT desulfurization pathway. The variety of sulfur compounds in petroleum feedstocks and complexity of the problem may require use of a consortium rather than a single bacterial strain. Alternately, use of multiple bioreactors each with a single dominant strain may be employed to achieve maximum desulfurization [299],... 

Lee, W. C. Ohshiro, T. Matsubara, T., et al., Crystallization and Preliminary X-Ray Analyses of Desulfurization Enzyme DszB and Its C27S Mutant Complexed With Biphenyl-2-Sulfinic Acid. Acta Crystallographica Section D-Biological Crystallography, 2004. 60 pp. 1636-1638. 

Metal sulfides and polysulfides have been extensively studied because of their key role in important catalytic processes such as the hydrodesulfurization of crude oil or the biosynthesis of metalloproteins. The coordination chemistry of polysulfides85 86 has been comprehensively reviewed similar to that of the heavier polychalcogenides.10,12 15 Polysullido complexes are themselves reactive and their exothermic desulfurization can be exploited as a means of... 

CONOSOX A complex flue-gas desulfurization process using potassium carbonate solution as the wet scrubbing medium. The product potassium bisulfite is converted to potassium thiosulfate and then reduced with carbon monoxide to potassium carbonate for re-use. The sulfur is recovered as hydrogen sulfide, which is converted to elemental sulfur by the Claus process. Developed by the Conoco Coal Development Company and piloted in 1986. 

Litol Also called Houdry-Litol. A process for making benzene by dealkylating other aromatic hydrocarbons. It is a complex process which achieves desulfurization, removal of paraffins and naphthenes, and saturation of unsaturated compounds, in addition to dealkylation. The catalyst contains cobalt and molybdenum. Developed by the Houdiy Process and Chemical Company and Bethlehem Steel Corporation. First installed by the Bethlehem Steel Corporation in 1964. Subsequently used at British Steel s benzole refinery, Teesside, England. 

An unusual reductive elimination can ensue from titanacyclobutanes possessing an alkenyl group at the carbon a to the titanium atom. Thus, alkenylcarbene complexes 48, prepared by the desulfurization of (fy-unsaturated thioacetals 49 or l,3-bis(phe-nylthio)propene derivatives 50 with a titanocene(II) reagent, react with terminal olefins to produce alkenylcyclopropanes 51 (Scheme 14.22, Table 14.4) [37]. This facile reductive... 

The carbene complexes generated by desulfurization of thioacetals with the titanoce-ne(II) species react with internal alkynes to produce the conjugated dienes 79 with high stereoselectivity (Scheme 14.34) [77]. The process appears to involve syn-elimination of P-hydride from the alkyl substituent that originates from the carbene complex after the formation of titanacyclobutene 80. 

The enone (137) was allowed to react with MeMgBr—Cu2I2 complex at 0 °C to furnish the keto-ester (138), which was then reduced by NaBH4 to afford the lactone (139). On the other hand, consecutive thioketalization, desulfurization and reduction of the ester (138) gave the alcohol (140), which was allowed to react with pTsCl in pyridine to afford (141) after smooth and concomitant fragmentation. The compound (141) was converted to 5-epi-kessane (142) and dehydrokessane (143) 47). 

In recent years, there have been numerous studies on alternate anode materials. The areas of interest include carbon-tolerant anode materials, sulfur-tolerant anode materials, and redox-stable anode materials. The idea is that by developing alternative anode materials and structure, the reforming and the desulfurization unit could be eliminated, which would reduce the system complexity and cost dramatically. In this section, the studies into these new, alternative anode materials will be briefly touched upon. Because the number of candidate materials studied is quite large, the amount of study on any individual candidate anode material is rather small, and not much work has been done to reproduce the results reported. Therefore, it is not possible to fully evaluate the real potentials of those new materials proposed by different groups of researchers. Therefore, the focus would be on the fundamental issues for these alternative materials, instead of on the processing and properties of a specific candidate material. 

Desulfuration.1 This complex as such or in combination with 2,2 -bipyridyl (bpy) or triphenylphosphine (a NiCRAL) can effect desulfuration of heteroarenes. aryl thioethers, dithioketals, sulfoxides, or sulfones in DME or THF at 63° in 1.5-30 hours. NiCRA is sufficient for aryl thioethers, dithioketals, but NiCRALs are more efficient for desulfuration of heteroarenes. Yields can be comparable with those obtained with Raney nickel. 

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