Catalysts molybdenum disulfide

T T ydroformylation of olefins to aldehydes over cobalt carbonyl catalysts is the first step in the industrial synthesis of oxo alcohols (1, 2). Reaction conditions require temperatures above 150 °C and pressures up to 3000 psig. Subsequent aldehyde hydrogenation occurs over supported cobalt or molybdenum disulfide catalysts. 

In this section we describe INS studies of molybdenum trioxide, a precmsor of molybdenum disulfide catalysts ( 7.5), and transition metal oxides which catalyse complete or partial oxidation of hydrocarbons, and copper zinc oxide catalysts, which catalyse methanol synthesis from carbon monoxide and dihydrogen ( 7.3.3). 

Molybdenum disulfide catalysts, promoted by cobalt or nickel, are used to remove organosulfur compoimds from crude petroleum by hydrogenolysis— hydrodesulfurisation or HDS [124,125,126], These compounds are imdesirable because they poison motor vehicle autoexhaust catalysts and bum to sulfur dioxide, an environmental pollutant. The most difficult compounds to desulfurise are sulfur heterocyclics thiophene, benzothiophene, dibenzothiophene and their methyl substituted derivatives. A typical reaction is the removal of sulfiir from thiophene ... 

P.C.H. Mitchell, D.A. Green, E. Payen, J. Tomkinson S.F. Parker (1999). Phys. Chem. Chem. Phys., 1, 3357-3363. Interaction of thiophene with a molybdenum disulfide catalyst—an inelastic neutron scattering study. 

One of the first radiotracer studies on sulfur uptake was that on a molybdenum disulfide catalyst.M0S2 was exposed to p S]H2S, admitted at 623K into the evacuated vessel containing the catalyst. ([ S]H2S in the following will be denoted for simplicity by H2 S, indicating labelled,... 

Yields may be increased and formation of by-products suppressed by addition of a small quantity of thiophene. F. e. s. K. Hata and K. Watanabe, Bull. Chem. Soc. Japan 32, 861 (1959) hydrocarbons from nitriles with molybdenum disulfide catalyst cf. K. Itabashi, Yuki Gosei Kagaku Kyokai Shi 17, 330 (1959) G, A. 53,17978a,... 

Catalysts based on molybdenum disulfide, M0S2, and cobalt or nickel as promoters are used for the hydrodesulfurization (HDS) and hydrodenitrogenadon (HDN) of heavy oil fractions [48,49]. The catalyst, containing at least five elements (Mo, S, Co or Ni, as well as O and A1 or Si of the support), is rather complex and represents a real challenge for the spectroscopist. Nevertheless, owing largely to research in the last twenty years, the sulfided C0-M0/AI2O3 system is one of the few industrial catalysts for which we know the structure in almost atomic detail [49, 50],... 

Molybdenum disulfide occurs in nature as mineral molybdenite. It is the principal ore from which molybdenum metal is recovered commercially. The compound is used as a dry lubricant and as an additive to lubricant. It also is used as a catalyst. 

Metal sulfides play an important role in catalyzing a wide variety of hydrogenations (e.g., of fats, coal, or olefins) and also desulfurization reactions, which are used in pretreatment of fossil fuels to reduce the emission of sulfur oxides during combustion (Section 8.5). Molybdenum disulfide, an important defect catalyst, can be made to function as an n-type (Moi+xS2) or p-type (Mo1 xS2) semiconductor by exposure to an appropriate mixture of H2S and hydrogen at temperatures on the order of 600 °C. The equilibrium... 

Tungsten Disulfide and Molybdenum Disulfide. Arrhenius parameters reported for reactions on both these catalysts (222- 225) were close to two compensation lines, characteristic of cracking and exchange processes (Table II, O and P). Since the reactants studied in this work were different from those used in kinetic measurements on tungsten metal, no direct comparison of activities is appropriate. Data for reactions of thiophene did not correlate with either line. 

The specific reaction ( activation ) conditions for the conversion of catalyst precursors to unsupported catalysts have a direct effect on the catalytic activity and dispersion. The importance of reaction intermediates in decomposition of ammonium heptamolybdate and ammonium tetrathiomolybdate, and the sensitivity of these intermediates to reaction conditions, were studied in coal liquefaction systems. Recent results indicate that optimization of activation conditions facilitates the formation of a highly dispersed and active form of molybdenum disulfide for coal liquefaction. The use of the catalyst precursors ammonium heptamolybdate, ammonium tetrathiomolybdate, and molybdenum trisulflde for the conversion of coal to soluble products will be discussed. 

Disulfides can also be produced by passing mixtures of the mercaptan and air (or dilute oxygen in an inert gas) over copper or cobalt oxide/molybdenum oxide catalysts at elevated temperatures. 

The Transition Metal Sulfides are a group of solids which form the basis for an extremely useful class of industrial hydrotreating and hydroprocessing catalysts. Solid state chemistry plays an important role in understanding and controlling the catalytic properties of these sulfide catalysts. This report discusses the preparation of sulfide catalysts, the role of disorder and anisotropy in governing catalytic properties, and the role of structure in the promotion of molybdenum disulfide by cobalt. 

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