Reductions of Carbon Monoxide

Since carbon monoxide has recently been found as a main product of C02 reduction in many systems, it would be important to convert CO into further reduced products such as methanol this is feasible because CO is much more reactive than C02 and is thus one of the starting materials of Cx chemistry.176 

Uribe et al.117 examined the reduction of CO in liquid NH3-0.1 M KI at -50°C, using various working electrodes such as Pt, Ni, C, and Hg. The reaction of CO with electrogenerated solvated electrons produced dimeric species, which precipitated as K2C202. Electrochemical reduction of CO in an aqueous solution at porous gas-diffusion and wet-proof electrodes of Co, Ni, and Fe was carried out,178 and Cj to C3 hydrocarbons and ethylene were reported to be the products. 

1 mM Ni-cyclam, a catalyst135 for C02 reduction to CO, methanol was obtained189 by electrolysis of an aqueous C02-saturated 0.1 M Et4NC104 solution at -1.5 V versus SCE using a Cu electrode, although the current efficiency was rather low (ca. 5%) the main reduction product of C02 was CO. 

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Goal Upgrading via Fischer-Tropsch. The synthesis of methane by the catalytic reduction of carbon monoxide and hydrogen over nickel and cobalt catalysts at atmospheric pressure was reported in 1902 (11). 

Thermal cracking tends to deposit carbon on the catalyst surface which can be removed by steaming. Carbon deposition by this mechanism tends to occur near the entrance of the catalyst tubes before sufficient hydrogen has been produced by the reforming reactions to suppress the right hand side of the reaction. Promoters, such as potash, are used to help suppress cracking in natural gas feedstocks containing heavier hydrocarbons. Carbon may also be formed by both the disproportionation and the reduction of carbon monoxide... 

The first demonstration of catalytic conversion of synthesis gas to hydrocarbons was accompHshed ia 1902 usiag a nickel catalyst (42). The fundamental research and process development on the catalytic reduction of carbon monoxide was carried out by Fischer, Tropsch, and Pichler (43). Whereas the chemistry of the Fischer-Tropsch synthesis is complex, generalized stoichiometric relationships are often used to represent the fundamental aspects ... 

Modified Fischer-Tropsch reduction of carbon monoxide with hydrogen. ... 

Until the 1920s, the major source of methanol was as a byproduct in the production of charcoal from wood—hence, the name wood alcohol. Now, most of the more than 10 billion lb of methanol used annually in the United States is synthetic, prepared by reduction of carbon monoxide with hydrogen. 

Lems Acid and Proton Induced Reduction of Carbon Monoxide... 

Metal hydrides and acyl-like CO insertion products are two types of species likely to be present in any homogeneous or heterogeneous process for the catalytic reduction of carbon monoxide. The discovery and understanding of new types of reactivity patterns between such species are of fundamental interest. As discussed elsewhere (11,22,54-57), bis(pentamethylcyclo-pentadienyl) actinide hydrides (58) are highly active catalysts for olefin hydrogenation as well as H-H and C-H activation. 

Formation of Hydrocarbons by Hydridic Reduction of Carbon Monoxide on Cp2Fe2(CO)4... 

Mechanistic Aspects of the Electrochemical Reduction of Carbon Monoxide and Methanol to Methane at Ruthenium and Copper Electrodes... 

The reduction of carbon monoxide also suffers deactivation by a surface species similar to that for carbon dioxide reduction but which forms at lower temperatures. The reduction of carbon monoxide does appear to proceed via a path similar to that which the reduction of carbon dioxide follows. Rates for methanol reduction are extremely variable. Methanol reduction, like carbon dioxide reduction, both increases in rate with decreasing pH until the surface becomes blocked with surface hydrogen and is also deactivated by increased temperature. For methanol, deactivation does not occur by the formation of the same surface species. 

The electrochemical reduction of carbon monoxide also offers a route for the production of fuels from inorganic sources. For example, carbon monoxide is formed from coal in gasification... 

The electrochemical reductions of carbon monoxide and methanol to methane (Equations 1 and 2) have potentials, under standard conditions, of +0.019 and +0.390 V vs SCE respectively (or a... 

Figure 2. Auger electron spectrum of the surface of two Ru electrodes after deactivation by reduction of carbon monoxide and methanol at higher temperatures (75 and 90 °C respectively in 0.2 M Na2SC>4 at pH 4 and -0.545 V vs SCE ). The presence of K on the surface must result from the adsorption of K+ ions present as an impurity in the electrolyte.

Scheme 105 Catalytic cycle for the reduction of carbon monoxide to methanol.

Production of Various Organic Substances by the Catalytic Reduction of Carbon Monoxide with Hydrogen under Pressure... 

Our initial studies in this area were based on the reasoning that, since the reduction of carbon monoxide to C2 products is a complex, multi-step process, the use of appropriate combinations of metals could generate synergistic effects which might prove more effective (in terms of both catalytic activity and selectivity) than simply the sum of the individual metal components. In... 

Electrochemical reduction of carbon monoxide in dry nonaqueous media at moderate to low pressures leads to the formation of the 1,3-cyclobutanedione dianion (squarate) at current efficiencies, up to about 45% depending on the cathode material [1,2]. In aqueous solution, electroreduction can lead to the formation of methane and other hydrocarbon products. The role of the metal/adatom in determining the extent of CO and hence hydrocarbon formation during the reduction of carbon dioxide is related to the ability of the electrode material to favor CO formation (Cu, Au, Ag, Zn, Pd, Ga, Ni, and Pt) and stabilize HCCO [3, 4]. 

The mass of data and material published during the past twenty-five years on the general subject of the synthesis of hydrocarbons by the catalytic reduction of carbon monoxide with hydrogen has been reviewed adequately by others (18). The object of this paper is to describe the highlights of the development of the Fischer-Tropsch type synthesis, prior to World War II, which have contributed to the present synthesis of liquid fuels from natural gas process and to dwell at greater length on certain of the work done by Hydrocarbon Research, Inc., in this field since the war. 

A systematic attempt to correlate the catalytic effect of different surfaces with their adsorptive capacity was made by Taylor and his collaborators. Taylor and Burns, for example, investigated the adsorption of hydrogen, carbon dioxide, and ethylene by the six metals nickel, cobalt, palladium, platinum, iron, and copper. All these metals are able to catalyse the hydrogenation of ethylene to ethane, while nickel, cobalt, and palladium also catalyse the reduction of carbon monoxide and of carbon dioxide to methane. 

Alcohols are among the most important and commonly encountered of all organic chemicals. Methanol (CH3OH), the simplest member of the family, was once known as wood alcohol because it was prepared by heating wood in the absence of air. Approximately 1.6 billion gallons of methanol are manufactured each year in the United States by catalytic reduction of carbon monoxide with hydrogen gas ... 

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