Carbon sulfides reactions with

Other components in the feed gas may react with and degrade the amine solution. Many of these latter reactions can be reversed by appHcation of heat, as in a reclaimer. Some reaction products cannot be reclaimed, however. Thus to keep the concentration of these materials at an acceptable level, the solution must be purged and fresh amine added periodically. The principal sources of degradation products are the reactions with carbon dioxide, carbonyl sulfide, and carbon disulfide. In refineries, sour gas streams from vacuum distillation or from fluidized catalytic cracking (FCC) units can contain oxygen or sulfur dioxide which form heat-stable salts with the amine solution (see Fluidization Petroleum). 

Hydrogen sulfide and carbon react at 900°C to give a 70% yield of carbon disulfide (102,103). A process for reaction of coke and hydrogen sulfide or sulfur in an electric-resistance-heated fluidized bed has been demonstrated on a laboratory scale (104). Hydrogen sulfide also forms carbon disulfide in reactions with carbon monoxide at 600—1125°C (105) or carbon dioxide at 350—450°C in the presence of catalysts (106). 

It is well established that sulfur compounds even in low parts per million concentrations in fuel gas are detrimental to MCFCs. The principal sulfur compound that has an adverse effect on cell performance is H2S. A nickel anode at anodic potentials reacts with H2S to form nickel sulfide. Chemisorption on Ni surfaces occurs, which can block active electrochemical sites. The tolerance of MCFCs to sulfur compounds is strongly dependent on temperature, pressure, gas composition, cell components, and system operation (i.e., recycle, venting, and gas cleanup). Nickel anode at anodic potentials reacts with H2S to form nickel sulfide. Moreover, oxidation of H2S in a combustion reaction, when recycling system is used, causes subsequent reaction with carbonate ions in the electrolyte [1]. Some researchers have tried to overcome this problem with additional device such as sulfur removal reactor. If the anode itself has a high tolerance to sulfur, the additional device is not required, hence, cutting the capital cost for MCFC plant. To enhance the anode performance on sulfur tolerance, ceria coating on anode is proposed. The main reason is that ceria can react with H2S [2,3] to protect Ni anode. 

Carius (8) replaced the oxygen in phosphoryl chloride by sulfur. This may be somewhat analogous to the replacement of oxygen in a carbonyl group by sulfur using phosphorus pentasulfide. Prinz (8) used thionyl chloride in his reaction with phosphorus sulfide and De Fazi (2) used carbon tetrachloride in a very interesting preparation of this important intermediate. 

Barium hydroxide decomposes to barium oxide when heated to 800°C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkahne, undergoes neutrahzation reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double decomposition reaction when Ba(OH)2 aqueous solution is mixed with many solutions of other metal salts. 

Reaction with carbon dioxide produces barium carbonate and hydrogen sulfide ... 

Exxon s Flexsorb SE solvents achieve high hydrogen sulfide selectivity by virtue of their molecular structure. These solvents are sterically hindered secondary amines. A bulky molecule is used to shield the available hydrogen radical on the nitrogen atom and prevent the insertion of carbon dioxide. The reaction with hydrogen sulfide is not sensitive to the amine s structure, so the steric hinderance affords higher hydrogen sulfide selectivity. 

It would obviously be informative if the release of insulin could be monitored spatially and on a useful time scale. In many microelectrode studies in biology, the substances concerned are easy to reduce or oxidize electrochemically. This is not so with sulfur-containing insulin, and it was not until a suitable (if complex) electrocatalyst was discovered that fast scan cychc voltammetry with microelectrodes could be used to monitor it. The substance that promotes reaction with the sulfide atoms in insulin is a mixed-valent RuOz-cyanoruthenate mixture. The catalyst is prepared in situ and deposited onto the carbon fiber of the microelectrode. The response time of electrodes thus prepared (Kennedy and Huang, 1995) is < 100 ms, and detection limits are as low as 5 pM. 

In cases where neutral or alkaline mine drainage predominates, problems may arise because of elevated concentrations of SO4, iron, manganese, and other solutes that are derived from sulfide oxidation or from reactions with carbonate or aluminosilicate minerals. Dissolved iron and aluminum may precipitate as the pH increases, and these precipitates can act as substrates for adsorption and co-precipitation (Stumm and Sulzberger, 1992 Foos, 1997 Brake et al., 2001). The dissolution of siderite,... 

Sulfur Generation. During the SO2 removal step the gaseous SO2 is converted to nonvolatile sulfuric acid which remains sorbed in the carbon s pores. Conversion of this sulfuric acid to SO2 or elemental sulfur by reaction with hydrogen sulfide has been studied in bench scale. 

Another system that contains both a reactive hydroxy- and amino group is that of the amidoximes (XCV). The preparation of. l. - l, 2,4-thiadiazoline-5-thiones (XCVII) by the reaction with carbon disulfide was first described in 1889 by Tiemann (339), Schubert (310) and Craven (95). The intermediate (XCVI), which changes into (XCVII) with the liberation of hydrogen sulfide on warming, was also isolated. 

If the hydroxy group of a 2-amino alcohol is replaced by a mercapto group (XCIX) the reaction with carbon disulfide yields thiazolidine-2-thiones (C) with liberation of hydrogen sulfide. This method though is practically never used since thiazolidine-2-thiones are more simply obtained from 2-halo amines (see further under Section IV.l) which are themselves starting materials for the 2-amine thiols. 

Isoxazoles possess suitable three-carbon units for conversion to the 1,2-dithiole skeleton. Thus, 5-phenylisoxazole (150) is thionated to 5-phenyl-l,2-dithiole-3-thione (151) <58AC(R)577>, and isoxa-zoline-3-thiones (152) form l,2-dithiole-3-imines by reaction with hydrogen sulfide <80CPB487>. 

Addition of thiocyanogen to r/.v-cyclooctcne affords trans-1,2-dithiocyanocyc o-octane (12), which is converted quantitatively into the imino dithiocarbonate (13) by refluxing for 2 hrs. with 47% hydrobromic acid, followed by neutralization with sodium carbonate. The tra/w-thiocarbonate (14) is produced from this imine by reaction with hydrogen sulfide in ethanol and converted into /rarcs-cyclooctene (15) by heating with triisooctyl phosphite at 135° (41 hrs.), using the entrainment technique to remove product as formed. 

The product alkyl-2-pyridyl sulfides are of synthetic interest by virtue of their ability to form a chelated lithio anion for reaction with carbon electrophiles. Subsequent removal of the sulfide can then be achieved using either nickel boride or tri- -butyl stannane [4] (Scheme 8). 

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