Desulfurizing agent

Reaction With Sulfur. An important use of calcium carbide has developed in the iron (qv) and steel (qv) industries where the carbide has been found to be an effective desulfurizing agent for blast-furnace iron. Calcium carbide and sulfur present in the molten metal react... 

Thianthrene was inert to (COD)2Ni(0) alone, but treatment with 2 mol equivalents of the nickel species in the presence of 2 mol equivalents of bpy converted it into dibenzothiophen (60%) and diphenyl (10%). The active desulfurizing agent was considered to be (bpy)(COD)Ni(0), the requirement for two metal equivalents being that one coordinates a sulfur the other effects rupture of the ring Scheme 8 illustrates this (77JOM51). 

In the production of ductile iron, calcium carbide is often used as a desulfurizing agent. When added to the iron, it reacts with the sulfides and forms calcium sulfide. This material floats on the surface of the molten iron, where it is skimmed off the surface and placed in a hopper. Since excess carbide is employed to ensure removal of the sulfur, the resulting slag contains high levels of unreactive carbide and must be handled as a reactive waste. 

To eliminate the use of calcium carbide, several major foundries have investigated the use of alternative desulfurization agents (Stephens 1988). One proprietary process employs calcium oxide, calcium fluoride, and two other materials. The foundry reported that not only was the quality of their iron satisfactory, but that the overall process was economically better than carbide desulfurization. 

The desulfurization chemistry appears to depend on the presence of free sulfur in the contacting gas and works in conjunction with organic sulfur pyrolytically released from the coke. Gases that decompose to form free sulfur or react to form free sulfur are suitable desulfurization agents and include, for example, refinery sour gas, pure and dilute S, mercaptans, mixtures of CO and SO2 or COS and H2O. 

Other fused thiiranes are more thermally stable. For example, the compound 45 desulfurizes at 160 °C (Scheme 11) <1987JA3801, 1990JA3029>. The reaction provided alkenes with retention of stereochemistry. In the presence of a desulfurizing agent such as phosphines or phosphites, the desulfurization temperature may be decreased to room temperature (Section 1.06.6.6) <1984CHEC(7)131>. The desulfurization of thiiranes is also subjected to transition metal catalysis. Since the initial step involves coordination of the metal to thiirane sulfur atom, the topic is discussed further in Section 1.06.6.4. 

The reaction of [(bipy)Ni(COD)] in THF with LAH led to [(bipy)NiAlH2]Li /fTHF, a rather efficient desulfurization agent. - During reactions such as the ones given in Scheme 4, the presence of the hydride favored path b. Some of the other reagents prepared in the same way and containing different metal species deserve to be studied further. 

Raney nickel is a stronger desulfurizing agent than nickel boride. On the other hand nickel boride, prepared from nickel(II) chloride and sodium borohydride, is more selective since it does not desulfurize aromatic sulfones. An example of such selectivity is desulfurization of p-phenylsulfonylphenyl p-tolyl sulfide (33), which affords diphenyl sulfone in 91% yield and toluene in 84% yield. In contrast. Raney nickel desulfurizes both the sulfide and the sulfone giving a mixture of benzene and toluene (equation 82). 5... 

Thioacetals, prepared from the corresponding ketones, have also been reduced to alkenes using moderately active Raney nickel as the desulfurization agent (Scheme 37). This form of Raney nickel does not reduce the newly formed alkene or react with other isolated carbon-carbon double bonds. Note that under these conditions the saturated hydrocarbon often observed in Raney nickel desulfurizations is not formed. Similar conditions have been used for the conversion of cyclodecanone to cyclodecene. While thioacetals have also served as intermediates in the analogous conversion of enones into dienes, a mixture of diene products is obtained. For instance, dithiane generation from 17p-hydroxy-A -androsten-3-one, followed by desulfurization affords a 4 1 mixture of 17P-hydroxy-A -androstadiene and 17P-hy-droxy-A -androstadiene, respectively. ... 

The atom abstraction route using PBu, as desulfurization agent has been extended to the preparation of very high molecular weight (My, 50,(K)0-1,000,000) network polymers (Fig. 13) by using [3]ferro-cenophanes with two trisulhdo bridges as monomers (S6). 

At the same time, 2-thioxo-2-(2,4,6-tri-/er/-butylphenyl)-3,3-diphenyl-l,2A5-thia-phosphirane 4c is desulfurized, readily giving the corresponding 1,2/x-thiaphosphirane 17 (Scheme 9) [13,23], Different phosphines were tested as desulfurization agents and tris(dimethylamino)phosphine proved to be the most efficient. 

Aero Desulfurizing Reagents. [Cyanamid Canada] Desulfurizing agents. 

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