Hydrogenation of carbon monoxide by ruthenium complexes with iodide promoters: catalytic and mechanistic investigations

Carbon monoxide and hydrogen are converted into organic products, including methanol, ethylene glycol, and ethanol, by halide-promoted ruthenium catalysts in organic solvents. Iodide salts are exceptionally good promoters for this system. Spectroscopic and reaction studies have shown that two ruthenium complexes, HRu₃(CO)₁₁^? and Ru(CO)₃I₃^?, are present during catalysis and essential for optimum activity. Possible roles for the involvement of these complexes in catalysis are considered.     

Hydrogenation of carbon monoxide over technetium catalysts

Supported Tc catalysts are active in CO hydrogenation, their activity depending on the nature of the support. The reaction proceeds predominantly toward methane formation. All catalysts studied yielded very little C₂ and C₃ hydrocarbons. The thermal desorption data indicate that the CO strongly bound to the substrate is responsible for CH₄ formation.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1507–1511, July, 1992.     

The effects of promoters in carbon monoxide hydrogenation on cobalt foil model catalysts

Carbon monoxide hydrogenation has been studied on polycrystalline cobalt foils, using a combination of UHV studies and atmospheric pressure reactions at 525 and 575 K and the effects of different promoters (K and Mg) have been investigated. The selectivity towards methane was decreased due to both promoters. The main effect with potassium was, however, the suppression of carbon deposition at higher reaction temperatures.     

Hydrogenation of carbon dioxide in the presence of rhodium catalysts

The results of CO₂ hydrogenation in the presence of the Wilkinson complexes, viz., RhCl₃ and acacRh(CO)₂, at room temperature and excess PPh₃ are presented. The influence of different ions on the catalytic properties of the Rh complexes was studied. Methanol and methyl formate are formed along with formic acid in the presence of an inorganic salt. Ions that are the most active in the formation of formic acid are the least active in methanol formation.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2436–2439, November, 2004.     

In situ formation of ruthenium catalysts for the homogeneous hydrogenation of carbon dioxide

A total of 44 different phosphines were tested, in combination with [RuCl(2)(C(6)H(6))](2) and three other Ru(II) precursors, for their ability to form active catalysts for the hydrogenation of CO(2) to formic acid. Half (22) of the ligands formed catalysts of significant activity, and only 6 resulted in very high rates of production of formic acid. These were PMe(3), PPhMe(2), dppm, dppe, and cis- and trans-Ph(2)PCH=CHPPh(2). The in situ catalysts prepared from [RuCl(2)(C(6)H(6))](2) and any of these 6 phosphine ligands were found to be at least as efficient as the isolated catalyst RuCl(O(2)CMe)(PMe(3))(4). There was no correlation between the basicity of monophosphines (PR(3)) and the activity of the catalysts formed from them. However, weakly basic diphosphines formed highly active catalysts only if their bite angles were small, while more strongly basic diphosphines had the opposite trend. In situ (31)P NMR spectroscopy showed that trans-Ru(H)(2)(dppm)(2), trans-RuCl(2)(dppm)(2), trans-RuHCl(dppm)(2), cis-Ru(H)(O(2)CH)(dppm)(2), and cis-Ru(O(2)CH)(2)(dppm)(2) are produced as the major metal-containing species in reactions of dppm with [RuCl(2)(C(6)H(6))](2) under catalytic conditions at 50 degrees C.     

Selective synthesis of acetic acid from hydrogen and carbon monoxide by homogeneous bimetallic catalysts

Alcohols which are the main products of the reaction of hydrogen and carbon monoxide in onium halide promoted ruthenium systems, are changed to acetic acid with the addition of cobalt carbonyl as the second catalyst component. Among Group VIa-VIIIa transition metal complexes, cobalt carbonyl is the only compound which promoted acetic acid formation when combined with ruthenium carbonyl under the conditions studied. The selectivity to acetic acid varied appreciably with the combinations of solvents and promoters, and exceeded 80% with optimal catalyst composition. The effects of solvents and promoters were investigated together with ¹³C tracer experiments from which the roles of halide anions of onium salts were determined.     

Hydrogenation of carbon monoxide on platinum metals

Together with methane, methanol is the main product of the hydrogenation of CO in the presence of platinum, palladium, and iridium, applied to Y-Al₂O₃, at atmospheric pressure and temperatures of 473–573 K. Dimethyl ether is also formed on platinum and palladium, while small amounts of ethanol and acetaldehyde are formed on iridium. The hydrogenation of CO in the presence of Rh and Ru leads to the formation of normal C₁-C₅ alcohols and C₂-C₅ aldehydes. Reduction of the energy of the metal-carbon bond in the platinum metals (Pd, Ir, Pt, Rh, Ru) increases their specific catalytic activity with respect to the formation of methane and oxygenated organic compounds, and increases the selectivity for higher alcohols and aldehydes.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 75–81, January–February, 1988.     

New catalysts for the oxidation of carbon monoxide

Catalytic activity of binary and multicomponent semiconductors of the ZnSe-CdTe system prepared in a form of powders and nanofilms in CO oxidation was studied by pulsed flow and circulation flow methods. The conditions of maximal CO conversion were determined from the results of investigation of individual and joint adsorption of the reactants in a broad temperature range, and the specific activity of the catalysts was determined by the specific reaction rate at the specified temperature and composition of the reaction mixture. A noticeable catalytic transformation of CO on the semiconductors under study (up to 78.5%) was noted as low as room temperature. It was concluded that the oxidation of CO and adsorption of the CO + O₂ mixture proceeds mainly by the collisional mechanism. It was noted that the high activity of studied catalysts already at room temperature (the (ZnSe)_0.05(CdTe)_0.95 solid solution possessed the highest activity) and the absence of high-cost metals in their composition allow us to recommend them as low-temperature, relatively low-cost catalysts for the neutralization of CO (carbon monoxide).     

Hydrogenation of benzene on sulfide catalysts in the presence of thiophene

The principles of benzene hydrogenation have been studied with sulfide catalysts NI/MS₂, Ni/SiO₂, M/SiO₂ and (Ni, M)/SiO₂ (M=Mo, W) obtained via metal complex precursors or by impregnation. In bimetallic catalysts active sites of benzene hydrogenation are formed upon reduction of the active component for thiophene hydrogenolysis.

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Ni/MS₂, Ni/SiO₂, M/SiO₂, (Ni,M)/SiO₂, M=Mo W, , . , .

     

Upon the mechanism of the homogeneous hydrogenation of carbon monoxide

Model studies on isolable complexes of ruthenium and osmium suggest that homogeneously catalysed carbon monoxide hydrogenation occurs via successive intermolecular additions of H⁻ and H⁺ to coordinated carbon monoxide.