Cobalt sulfides, hydrogenation catalyst

The same is true of rhenium catalysts rhenium heptoxide [42], rhenium heptasulfide [5i] and rhenimn heptaselenide [54] all require temperatures of 100-300° and pressures of 100-300 atm. Rhenium heptasulfide is not sensitive to sulfur, and is more active than molybdenum and cobalt sulfides in hydrogenating oxygen-containing functions [55,55]. 

Because of the importance of the promotion effect and because many of the central questions surrounding TMS catalysis are about promotion, it is valuable to review a history of the effect. The first reference to a catalyst based on molybdenum and cobalt sulfides capable of desulfurizing coal oils in the presence of hydrogen was a patent from I. G. Farben Industrie dated May 24, 1928 (5). Before this, M. Pier and his team at BASF (1924-1925)... 

The Alkazid process removes sulfur compounds from gas streams. All the sulfur compounds are first catalytically hydrogenated to hydrogen sulfide (H2S) using a cobalt/molyb-dena catalyst. The H2S is then absorbed in an aqueous solution of a potassium salt of either methylamino propionic acid ( Alkazid M ), or dimethylamino acetic acid ( Alkazid DIK ). This solution is heated to regenerate the hydrogen sulfide as a concentrate. This concentrate is then treated by the Claus process to recover the sulfur.1... 

Platinum catalysts have been shown to be highly selective for the hydrogenation of halonitrobenzenes to haloanilines. A number of effective platinum catalysts or catalyst systems have been described in the literature, mostly in patents.96 Dovell and Greenfield found that the sulfides of the platinum metals and cobalt were highly selective in the hydrogenation of halo-substituted nitrobenzenes.117-119 There was no detectable dechlorination with the sulfides of palladium, platinum, rhodium, ruthenium, and cobalt no detectable debromination occurred with platinum sulfide trace debromination occurred with rhodium sulfide and cobalt sulfide and appreciable debromination occurred with palladium sulfide. Typical hydrogenations with 5% platinum sulfide on carbon catalyst are given in eqs. 9.52 and 9.53 with 2,5-dichloronitrobenzene and p-bromobenzene, respectively.118... 

Removal of sulfur from these complexes remains challenging. Catalysts such as [M(COD)(PPh3)2]+ (M = Rh, Ir) only hydrogenate the C=C bond of benzothio-phene, whereas the hydrogenation with rhodium triphos complexes gives 2-ethyl-thiophenol.148 The addition of Co4(CO)i2 to (21-XXVIII, ML, = Cp Ir), however, leads to partial desulfurization, presumably with formation of cobalt sulfide.149... 

The hydroformylation of alkenes is commonly run using soluble metal carbonyl complexes as catalysts but there are some reports of heterogeneously catalyzed reactions of olefins with hydrogen and carbon monoxide. Almost all of these are vapor phase reactions of ethylene or propylene with hydrogen and carbon monoxide catalyzed by rhodium, " 20 ruthenium,nickel, 22,123 cobalt, 23,124 and cobalt-molybdenum 23 catalysts as well as various sulfided metal catalysts. 23,125,126... 

Iron-chromium oxide catalysts, reduced with hydrogen-containing in the conversion plants, permit reactions temperatures of 350 to 380°C (high temperature conversion), the carbon monoxide content in the reaction gas is thereby reduced to ca. 3 to 4% by volume. Since, these catalysts are sensitive to impurities, cobalt- and molybdenum-(sulfide)-containing catalysts are used for gas mixtures with high sulfur contents. With copper oxide/zinc oxide catalysts the reaction proceeds at 200 to 250°C (low temperature conversion) and carbon monoxide contents of below 0.3% by volume are attained. This catalyst, in contrast to the iron oxide/chromium oxide high temperature conversion catalyst, is, however, very sensitive to sulfur compounds, which must be present in concentrations of less than 0.1 ppm. 

Strongly Acidic Catalysts with Mild Hydrogenation Activity. Reaction Mechanism. Typical catalysts with strongly acidic properties and relatively mild hydrogenation activity are metal sulfides such as nickel, tungsten, or cobalt sulfide on supports such as silica-alumina. 

We selectively hydrogenated 6-chloro-2(IH)-hydroxyquinoxaline-4-oxides to 6-chloro-2(IH)-quinoxalinone, using sulfided and non-sulfided catalysts. The catalyst of choice is platinum sulfide. Our catalyst studies included sulfided and non-sulfided platinum, palladium, rhodium, ruthenium, sulfided nickel, Raney nickel, and cobalt. 

An interesting variation of the hydrogenation process involves the use of a special cobalt sulfide catalyst to produce 1-deoxy-l-mercaptosorbitol (37) (thiosorbitol) from glucose. 

The element cobalt is inclined to form complexes and to bind different ligands to these complexes. This makes the metal suitable as a catalyst An important industrial process using cobalt as a catalyst is the removal of sulfur from oil by hydrodesulfurization. In this case the catalyst is composed of an inert carrier material, alumina, and a mixture of cobalt and molybdenum oxides. The organically bound sulfur is removed as hydrogen sulfide, which is neutralized. The oil can then be delivered with very low sulfur content. This has been of great importance for the environment in our populahon centers. 

The predominant process for manufacture of aniline is the catalytic reduction of nitroben2ene [98-95-3] ixh. hydrogen. The reduction is carried out in the vapor phase (50—55) or Hquid phase (56—60). A fixed-bed reactor is commonly used for the vapor-phase process and the reactor is operated under pressure. A number of catalysts have been cited and include copper, copper on siHca, copper oxide, sulfides of nickel, molybdenum, tungsten, and palladium—vanadium on alumina or Htbium—aluminum spinels. Catalysts cited for the Hquid-phase processes include nickel, copper or cobalt supported on a suitable inert carrier, and palladium or platinum or their mixtures supported on carbon. 

Alternative means for removal of carbonyl sulfide for gas streams iavolve hydrogenation. For example, the Beavon process for removal of sulfur compounds remaining ia Claus unit tail gases iavolves hydrolysis and hydrogenation over cobalt molybdate catalyst resulting ia the conversion of carbonyl sulfide, carbon disulfide, and other sulfur compounds to hydrogen sulfide (25). 

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