Hydrogen sulfide, dehydrogenation Hydrogenation

Rhenium oxides have been studied as catalyst materials in oxidation reactions of sulfur dioxide to sulfur trioxide, sulfite to sulfate, and nitrite to nitrate. There has been no commercial development in this area. These compounds have also been used as catalysts for reductions, but appear not to have exceptional properties. Rhenium sulfide catalysts have been used for hydrogenations of organic compounds, including benzene and styrene, and for dehydrogenation of alcohols to give aldehydes (qv) and ketones (qv). The significant property of these catalyst systems is that they are not poisoned by sulfur compounds. 

The initial step of the adsorption of cyclic sulfides on a Mo(100) surface is also the formation of adsorbed thiolate groups.395-397 Adsorbed alkyl thiolates decompose to adsorbed sulfur, carbon, and hydrogen on the clean Mo surface, but once the surface is deactivated by adsorbed sulfur, alkanes and alkenes evolve from the surface. Tetrahydrothiophene (34) and trimethylene sulfide decompose on Mo(110) to alkanes and alkenes by way of a common intermediate, which is proposed to be a surface thiolate (33). The thiolate undergoes hydrogenation or dehydrogenation, depending on the surface hydrogen concentration (Scheme 4.115).398 399... 

Fries rearrangement, 18 336, 337 isomerization and transalkylation of alky-laromatics, 18 329 epoxide transformations, 18 351-352 hydration and ammonolysis of ethylene oxide, 18 351, 352 isomerization, 18 351 framework composition, 33 226-228 hydrogenation, dehydrogenation, and related reactions, 18 360-365 dehydrocyclization of s-ethylphenyl using zeolites and carbonyl sulfide, 18 364, 365... 

Another dehydrogenation process was introduced before 1944 for converting methyl-cyclohexane to toluene over a tungsten-nickel sulfide catalyst. Substantially higher hydrogen partial pressures are employed in this process than in hydroforming. 

Metal oxides, sulfides, and hydrides form a transition between acid-base and metal catalysts. They catalyze hydrogenation-dehydrogenation as well as many of the reactions catalyzed by acids such as cracking and isomerization. Their oxidation activity is related to the possibility of two valence states which allow oxygen to be released and reabsorbed alternately. Common examples are oxides of cobalt, iron, zinc, and chromium and hydrides of precious... 

Hydrogenation and dehydrogenation employ catalysts that form unstable surface hydrides. Transition-group and bordering metals such as Ni, Fe, Co, and Pt are suitable, as well as transition group oxides or sulfides. This class of reactions includes the important examples of ammonia and methanol syntheses, the Fischer-Tropsch and oxo and synthol processes and the production of alcohols, aldehydes, ketones, amines, and edible oils. 

Sulfides. In addition In serving as the primary natural source of molybdenum, purified molybdenum disullide MoS is an excellent lubricant when in Ihc form of a dry him. or as an additive to oil or grease. The compound also is used as a filter in nylons, and as an effective catalyst for hydrogenation-dehydrogenation reactions. Molybdenum also combines with sulfur as Ihe sesquisullide Mo Si and the trisulftde MoS.r, uses for which arc under study. 

Hydrogen ligands, 689-711 Hydrogen selenide metal complexes, 663 Hydrogen sulfide metal complexes, 516 Hydrogen telluride metal complexes, 670 Hydroporphyrins, 814-856 basicity, 853 dehydrogenation, 853 demetallation, 854 deuteration, 853 mass spectra, 852 metallation, 854 NMR, 852 non-aromatic, 855 photochemistry, 854 redox chemistry, 855 synthesis, 852... 

Hydrogen sulfide generated by dehydrogenation reactions in the fusion process is absorbed by caustic soda solution. The crude melt is ground and dissolved. Insoluble crude melts are digested with caustic soda or sodium sulfide. From the resulting solution, after clarification, the dye is precipitated by air blowing or acidification, then filtered and dried. 

The process is commonly carried out in jacketed stainless steel vessels with stirrer and reflux condenser. As in dry fusion, dehydrogenation reactions give off hydrogen sulfide, which is absorbed in caustic soda solution. 

As is obvious, hydrogen sulfide active under current conditions is one of the reaction products. Its aggressiveness, the ability to interact with S02 even under natural conditions, promotes sulfur accumulation in the system, affects synthesis of condensation products and can alter their catalytic activity. Therefore, despite high effectiveness, oxidative catalytic dehydrogenation of ethylbenzene by sulfur dioxide may be found unacceptable for production management in relation to ecology and protection of the environment. 

Tungsten sulfide catalyst should accelerate not only the hydrogenation reactions, but also dehydrogenation of hydroaromatics to aromatics. Thermodynamic calculations show that such reactions are probable at about 500°C. at a hydrogen pressure of about 50 atm. Use of the tung-... 

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