Hydrogenation of carbon oxides

Iron has a rich surface coordination chemistry that forms the basis of its important catalytic properties. There are many catalytic applications in which metallic iron or its oxides play a vital part, and the best known are associated with the synthesis of ammonia from hydrogen and nitrogen at high pressure (Haber-Bosch Process), and in hydrocarbon synthesis from CO/C02/hydrogen mixtures (Fischer-Tropsch synthesis). The surface species present in the former includes hydrides and nitrides as well as NH, NH2, and coordinated NH3 itself. Many intermediates have been proposed for hydrogenation of carbon oxides during Fischer-Tropsch synthesis that include growing hydrocarbon chains. 

Although other methods of preparation, involving the hydrogenation of carbon oxides, the pyrolytic decomposition of formates etc, have been patented, ihey do not appear to have achieved commercial importance... 

Spectroscopic techniques, namely, in situ IR investigations and vibrational spectroscopies, allowed investigators to acquire information of the adsorbed species involved in the hydrogenation of carbon oxides.8,35 Although different interpretations exist with respect to the role of surface formates, there is agreement that a bifunctional mechanism is operative namely, C02 adsorbs mainly on Zr02 and hydrogen adsorbs and dissociates on Cu. 

Hydrogenation of carbon oxides to give mixtures of hydrocarbons, alcohols, esters, and acids... 

Hydrogenation of carbon oxides with iron, cobalt, or nickel catalysts (Fischer-Tropsch process). Hydrocarbons are the main products Recovery and separation of oxygenated products obtained from CO and H2 Partial oxidation of nonaromatic hydrocarbon mixtures, e.g., petroleum, paraffins, and natural gas, to produce a mixture of products, such as esters, acids, aldehydes, ketones, and alcohols. This also includes higher fatty acids from petroleum and patents on formaldehyde production... 

Other important endothermic transformations are those involving C02 (reactions 10 and 11). The Boudouard reaction occurs between carbon and carbon dioxide to increase the yield of carbon monoxide (reaction 10). Finally, some methanation reactions by hydrogenation of carbon oxides also take place (reactions 12 and 13), which may lead to a significant decrease in the H2 concentration of the final synthesis gas. The overall energy requirement of gasification can be balanced by a suitable combination of exothermic and endothermic reactions, mainly through the control of the 02/H20 ratio in the reaction medium. 

The hydrogenation of carbon oxides to methane is widely used in gas chromatography for their trace determination in monomers [22, 115], air [116], mine methane [117] and other substances. 

Elattar, A., W.E. Wallace and R.S. Craig, 1978, Intermetallic compounds as catalysts for hydrogenation of carbon oxides, in Rare Earths in Modem Science and Technology, eds G.J. McCarthy and J.J. Rhyne (Plenum, New York) p. 87. 

The relative inertness of the carbon surface is of paramount importance when carbon materials are going to be used as supports for hydrogenation catalysts. These systems usually consist of more than one metallic phase (bimetallic systems) and even by metals promoted by metal oxides. The carbon inertness facilitates interaction between the metals and/or between the metals and the promoters, yielding more active and selective catalysts than those supported on other common supports. These aspects will be illustrated by examples of the application of carbon-supported catalysts to the hydrogenation of carbon oxides. 

Carbon-supported catalysts have been studied extensively in the hydrogenation of carbon oxides (CO and CO2) to yield methane and hydrocarbons. Different phases (e.g., metals, metal alloys, carbides) have been prepared by a variety of techniques and precursors. Also, although the early studies used activated carbons as support, more recent studies analyze the possibilities of other carbon materials, such as nanofibers and nanotubes. 

Fischer-Tropsch synthesis, FTS, is, roughly speaking, the hydrogenation of carbon oxides to produce hydrocarbons or alcohols with elimination of water [1]. Special cases are the methanation reaction,... 

Scheme 6.113 Reactions and intermediates originaiiy assumed in cobait-cataiyzed hydrogenation of carbon oxide.

Figure 23.6 Integrated process scheme combining OCM and hydrogenation of carbon oxides. Adapted from Ref. [47].

Albrecht, M., Rodemerck, U., and Kondratenko, E.V. (2014) Higher hydrocarbon production through oxidative coupling of methane combined with hydrogenation of carbon oxides. Chem. 

The catalytic hydrogenation of carbon oxides produces a large variety of products ranging from Ci containing molecules (CH4 and CH3OH) to higher molecular weight paraffins, olefins, and alcohols, a process that requires C-C bond formation... 

Borodko, Y. and Somoijai, G.A. Catalytic hydrogenation of carbon oxides. Appl. 

Fierro, J.L.G. Hydrogenation of carbon oxides over perovskite-type oxides. Catal Rev. Set Eng. 1992, 34, 321-336. 

Chapter 18 Hydrogenation of Carbon Oxides on Metal Oxides J.L.G. Fierro... 

T. Herranz, S. Rojas, F. J. Perez-Alonso, M. Ojeda, P. Terreros, and J. L. G. Fierro, Hydrogenation of carbon oxides over promoted Fe-Mn catalysts prepared by the microemulsion methodology, Applied Catalysis A, vol. 311, no. 

K. E. Larsen, J. K. Norskov and J. Sehested, Process and Catalyst For Hydrogenation of Carbon Oxides , US Patent US7790776 B2 (2010). 

Toda , formaldehyde is manufactured principally from methanol limited amoimts are also produced by the oxidation of natural gas and the lower petroleum hydrocarbons. Although other methods of preparation im oh ing the hydrogenation of carbon oxides, the pyrolytic decomposixion of foiTuates, etc., ha e been patented, they do not appear to have achieved commercial importance. In connection with the reduction of carbon oxides, Xeu ton and Dodg determined the equilibriiun constant for the reaction,... 

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