Desulfurization, reagents

In the United States calcium carbide-based acetylene is mainly used in the oxyacetylene welding market although some continues to be used for production of such chemicals as vinyl ethers and acetylenic alcohols. Calcium carbide is used extensively as a desulfurizing reagent in steel and ductile iron production allowing steel mills to use high sulfur coke without the penalty of excessive sulfur in the resultant steel (see Sulfurremoval and recovery). Calcium cyanamide production continues in Canada and Europe (see Cyanamides). 

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

The filtered cake produced from the manufacture of dicyandiamide contains about 86% calcium carbonate. American Cyanamid Co. blends the dried waste for the manufacture of calcium carbide-based desulfurized reagents as a gas releasiag agent. 

Desulfogypsum, 4 591-593, 595 Desulfurization, 1 650 10 785 Desulfurizing reagents, calcium carbide application, 4 549-550 Deswelling process, for solvent removal, 28104... 

Photolysis of these benzynes at 266 nm leads to production of 3,6-difluoro- and 3,6-bis(trifluoromethyl)-l,4-benzdiyne which are converted into the corresponding hexatriynes upon further irradiation at 266 nm. 4,8-Diethylbenzo[l,2-r/ 4,5- ]bis[l,2,3]trithiole 86 undergoes photolytic degradation on irradiation with a high-pressure mercury lamp, without the requirement for an additional desulfurization reagent, to produce thianthrene 87 in low yield (Equation 21) <2000TL1801>. 

Other desulfurization reagents are also effective, and the dithiadiazine (149) gives the thiadiazole (150) on treatment with triphenylphosphine (76JCS(P1)38). Triphenylphosphine also converts thiadiazines (144) into pyrazoles (77S485), and 2,1,4-benzothiadiazines (151) into the corresponding benzimidazoles (74BRP1350277). This latter reaction is in marked contrast to that of the isomeric 1,2,4-benzothiadiazines (145), which lose NH rather than S on treatment with triphenylphosphine. 

Desulfurizing reagent -calcium carbide as [CARBIDES - CALCIUM CARBIDE] (Vol 4)... 

A variety of other Lewis acids have been used in conjunction with LAH, including nickel, copper and titanium salts, the resulting reagents being used to reduce sulfides and benzyl ethers to hydrocarbons (equations 46-48). Addition of nickelocene to LAH produces a specific desulfurization reagent which does not reduce ketones and esters. ... 

Aero Desulfurizing Reagents. [Cyanamid Canada] Desulfurizing agents. 

Chan MC, Cheng KM, Ho KM, Ng CT, Yam TM, Wang BSL, Luh TY. Transition-metal-promoted reactions nickelo-cene-lithium aluminum-hydride. 19. A versatile desulfurization reagent. J. Org. Chem. 1988 53(19) 4466-4471. 

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