Hydrogenation of carbon monoxide

Carbon monoxide hydrogenation catalyzed by a solid base was first observed on MgO in a TPD study of interaction of adsorbed CO with molecular hydrogen. The TPD profiles indicating interaction of adsorbed CO with Hz are shown in Fig. 4.30. Admission of hydrogen to preadsorbed CO on MgO results in a decrease in CO peaks and the appearance of new CO peak at 700 K. The new peak of CO accompanies hydrogen evolution. 

IR measurement shows that the surface species resulting from the reaction of adsorbed CO with Hz are in the form of formate. Hie reaction is sug ested to proceed by the following mechanism. 

The negatively charged adsorbed species of CO react with H to form [CHO] groups which are adsorbed on surface oxygen ions. The [CHO] group adsorbed on oxygen ion becomes the same structure as the formate group, hence the IR spectra tire the same as those for formate. 

Essentially the same type of reaction as that of adsorbed CO with Hz takes place over other types of solid base catalysts such as LazOj, ZrOz, and ThOz.  

The dotted line denotes the evolution of CO when Hj was not admitted. (Reproduced with permission by H. Hattori,y. Chtm. Soe. Faraday Trans. I, 80, 

The catalytic reduction of carbon monoxide producing hydrocarbons, olefins, and oxygenated compounds generally known as Fischer-Tropsh chemistry is of great industrial and economical interest. The possibility of substituting petroleum by other carbonaceous sources such as coal in the production of organic 

Metal clusters have also proved to have great possibilities as homogeneous catalysts for the reaction of the reduction of carbon monoxide. Selected examples of catalytic hydrogenation of carbon monoxide by metal clusters are shown in Table 2.32. 

Rhodium species as Rh6(CO)i6 and [Rh5(CO)i5] catalyze the reduction of carbon monoxide to light alcohols, specially to ethylene glycol. 

OS3(CO)i2 CH4 (29%) C2H6 (4%) C3H8 (20%) CHaBr (51%) CjHjBr (13%) 180°C, 2atm H2 CO-3 l solvent liq-BBr3 sealed glass tube rate ca. 20 tumover/h 1 

RhJCO),6 [Rh,(CO)i5]-[RhaQCO),] -[Rh,P(CO)2.] -[Rh,282(00)32]= - Polyols, primarily ethylene glicol. MeOH, EtOH, as side products. 200-290 °C 500-1000 atm H2 CO =1 1. Activity is lower for compounds with heteroatoms. High-nuclearity species appear to be stable under catalysis conditions. 2, 3 

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Fischer-Tropsch Process. The Hterature on the hydrogenation of carbon monoxide dates back to 1902 when the synthesis of methane from synthesis gas over a nickel catalyst was reported (17). In 1923, F. Fischer and H. Tropsch reported the formation of a mixture of organic compounds they called synthol by reaction of synthesis gas over alkalized iron turnings at 10—15 MPa (99—150 atm) and 400—450°C (18). This mixture contained mostly oxygenated compounds, but also contained a small amount of alkanes and alkenes. Further study of the reaction at 0.7 MPa (6.9 atm) revealed that low pressure favored olefinic and paraffinic hydrocarbons and minimized oxygenates, but at this pressure the reaction rate was very low. Because of their pioneering work on catalytic hydrocarbon synthesis, this class of reactions became known as the Fischer-Tropsch (FT) synthesis. 

Some catalysts are ha2ardous materials, or they react to form ha2ardous substances. For example, catalysts used for hydrogenation of carbon monoxide form volatile metal carbonyl compounds such as nickel carbonyl, which are highly toxic. Many catalysts contain heavy metals and other ha2ardous components, and environmentally safe disposal has become an increasing concern and expense. 

Only recently has a mechanism been proposed for the copper-cataly2ed reaction that is completely satisfactory (58). It had been known for many years that a small amount of carbon dioxide in the feed to the reactor is necessary for optimum yield, but most workers in the field beHeved that the main reaction in the formation of methanol was the hydrogenation of carbon monoxide. Now, convincing evidence has been assembled to indicate that methanol is actually formed with >99% selectivity by the reaction of dissociated, adsorbed hydrogen and carbon dioxide on the metallic copper surface in two steps ... 

There have been a number of investigations on the hydrogenation of carbon monoxide and carbon dioxide together, (6, 7, 8) it was concluded that C02 is not hydrogenated in the presence of carbon monoxide. Such... 

The Fischer-Tropsch and Related Processes for Synthesis of Hydrocarbons by Hydrogenation of Carbon Monoxide H. H. Storch... 

In a later publication, Kolbel et al. (K16) have proposed a less empirical model based on the assumption that the rate-determining steps for a slurry process are the catalytic reaction and the mass transfer across the gas-liquid interface. When used for the hydrogenation of carbon monoxide to methane, the process rate is expressed as moles carbon monoxide consumed per hour and per cubic meter of slurry ... 

Ruthenium is a known active catalyst for the hydrogenation of carbon monoxide to hydrocarbons (the Fischer-Tropsch synthesis). It was shown that on rathenized electrodes, methane can form in the electroreduction of carbon dioxide as weU. At temperatures of 45 to 80°C in acidihed solutions of Na2S04 (pH 3 to 4), faradaic yields for methane formation up to 40% were reported. On a molybdenium electrode in a similar solution, a yield of 50% for methanol formation was observed, but the yield dropped sharply during electrolysis, due to progressive poisoning of the electrode. 

The synthesis of metal nanoparticles via the controlled decomposition of pre-prepared organometallic complexes or metal carbonyls where the metals are already in the zero valent or low-valent state has been known since 1970. The first examples were Pd- and Pt-dibenzylideneacetone complexes where the coordinated ligands detached using either hydrogen of carbon monoxide under mild conditions to give the respective metal nanoparticles [310]. 

Fe/Ir catalysts In situ Fe and Ir Mossbauer spectroscopy of silica-supported Fe/Ir catalysts with different iron to iridium ratios following pretreatment in hydrogen show that the reduction of the Fe component is enhanced by the presence of Ir metal. The presence of Ir was found to increase the catalytic activity in hydrogenation of carbon monoxide and also to influence selectivity... 

The catalytic hydrogenation of carbon monoxide to produce CQ petroleum is reported by Fischer and Tropsch [5,6]... 

Storch HH, Anderson RB, Hofer LJE, Hawk CO, Anderson HC, GolumbicN (1948) Synthetic liquid fuels from hydrogenation of carbon monoxide, Part 1 review of literature. Technical paper 709. United States Department of the Interior, Washington, DC... 

At one time, most methanol was produced by the destructive distillation of wood (i.e., heating wood to a high temperature in the absence of air) => wood alcohol . 1) Today, most methanol is prepared by the catalytic hydrogenation of carbon monoxide. 

One of the most important, and perhaps the best studied, applications of three-phase fluidization is for the hydrogenation of carbon monoxide by the Fischer-Tropsch (F-T) process in the liquid phase. In this process, synthesis gas of relatively low hydrogen to carbon monoxide ratio (0.6 0.7) is bubbled through a slurry of precipitated catalyst suspended in a heavy oil medium. The F-T synthesis forms saturated and unsaturated hydrocarbon compounds ranging from methane to high-melting paraffin waxes (MW > 20,000) via the following two-step reaction ... 

A search for alternative energy supplies has triggered efforts to develop efficient homogeneous catalysts for Fischer-Tropsch-type syntheses via hydrogenation of carbon monoxide, a likely future key material available, for example, through oxidation of coal (33, 327, 328, 417, 418). Metal cluster systems have been used in attempts to emulate the presently used heterogeneous catalysts. The important reactions are methanation,... 

In related studies, Cp2ZrCl2 has been found to catalyze at room temperature an aluminum hydride (i-Bu2AlH) reduction of CO to linear Ci-C5 alcohols (430). The system involves reaction of complex 55 with CO, which precipitates the starting zirconium(IV) complex and leaves a yellow solution, that on hydrolysis yields the alcohols. Toluene solutions of Cp2Ti(CO)2 complex under H2/CO effect Eq.(69), i.e., a homogeneous stoichiometric hydrogenation of carbon monoxide to methane (426). 

Homogeneous catalysts have now been reported for hydrogenation of carbon monoxide, a combustion product of coal (see Section VI,B). More effective catalysts will undoubtedly be discovered in the near future. Polynuclear or, at least, binuclear sites are favored for reduction of the triple bond in carbon monoxide (see Section VI,B), and this together with the popular parallelism to heterogeneous systems, has renewed interest in metal clusters as catalysts (see Section VI). A nickel cluster is the first catalyst reported for mild (and selective) hydrogenation of the triple bond in isocyanide (see Section VI,A). The use of carbon monoxide and water as an alternative hydrogen source is reattracting interest (see Section VI,C). 

Hydrogenation of Carbon Monoxide on Alumina-Supported Metals... 

Hydrogenation of Carbon Monoxide to Methanol and Ethylene Glycol by Homogeneous Ruthenium Catalysts... 

Table I. Hydrogenation of carbon monoxide with ruthenium catalysts. All reactions performed in a glass-lined rocker bomb with 2.35 mmol Ru (charged as RU3CO) 2), at 230°C under 340 atm 1 1 H2/CO for 2 h, unless noted otherwise.

Solutions of Ru3(CO)i2 in carboxylic acids are active catalysts for hydrogenation of carbon monoxide at low pressures (below 340 atm). Methanol is the major product (obtained as its ester), and smaller amounts of ethylene glycol diester are also formed. At 340 atm and 260°C a combined rate to these products of 8.3 x 10 3 turnovers s-1 was observed in acetic acid solvent. Similar rates to methanol are obtainable in other polar solvents, but ethylene glycol is not observed under these conditions except in the presence of carboxylic acids. Studies of this reaction, including infrared measurements under reaction conditions, were carried out to determine the nature of the catalyst and the mechanism of glycol formation. A reaction scheme is proposed in which the function of the carboxylic acid is to assist in converting a coordinated formaldehyde intermediate into a glycol precursor. 

The potential importance of homogeneous catalytic reactions in synthesis gas transformations (i.e., hydrogenation of carbon monoxide) has been widely recognized in recent years. In the first place, such systems could provide structural and mechanistic models for the currently more important, but more difficult to study, heterogeneous catalysts. Secondly, product selectivity is generally more readily achievable with homogeneous catalysts, and this would be an obviously desirable feature in an efficient process converting synthesis gas to useful chemicals and fuels. 

The use of Ru(acac)3 under very high temperature (268 °C) and pressure (1300 bar of H2/CO) in THF provides a catalyst for the hydrogenation of carbon monoxide to methanol and methyl formate [73]. The active species is derived from Ru(CO)5. 

F. Fischer and H. Tropsch, Reduction and hydrogenation of carbon monoxide, Brennst-ojf-Chem., 1926, 7, 299-300. 

Methanol, CHgOH, also known as wood spirit , was produced by destructive distillation of wood. Today, most of the methanol is produced by catalytic hydrogenation of carbon monoxide at high pressure and temperature and in the presence of ZnO - CraOg catalyst. 

Catalytic Hydrogenation of Carbon Monoxide to Methane, and of Unsaturated Organic Compounds... 

One of the simplest examples for such effects is the oxidation of ammonia with iron oxide-bismuth oxide as a catalyst. Here, the addition of bismuth oxide results in the formation of nitrous oxides as the main product whereas an iron oxide catalyst without bismuth oxide yields nitrogen almost exlcusively. Selectively guiding catalysts become increasingly important in the synthesis of organic compounds, e.g., in the hydrogenation of carbon monoxide where the type of obtainable product can be varied, within wide limits, by the kinds of catalysts and promoters which are employed. 

The direct conversion deals with the straight hydrogenation of carbon monoxide to paraffins, olefins and heteroatom (oxygen, nitrogen) containing products. The indirect conversion invokes intermediates such as methanol, methyl formate and formaldehyde. The latter ones in a consecutive reaction can yield a variety of desired chemicals. For instance, acetic acid can be synthesized directly from CO/H2, but for reasons of selectivity the carbonylation of methanol is by far the best commercial process. 

Table I. Effect of the Addition of Cesium Ions on the Catalytic Activity and Selectivity of the Ru/Rh/HOAc System for the Hydrogenation of Carbon Monoxide ...

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