Carbon monoxide nickel-copper catalysts

J.J. Prinsloo and P.C. Gravelle, Volumetric and calorimetric study of the adsorption of hydrogen, at 296 K, on supported nickel and nickel-copper catalysts containing preadsorbed carbon monoxide, J. Chem. Soc., Faraday Trans. I, 1980, 76, 512. 

Klouz investigated ethanol steam reforming and autothermal reforming over a nickel/copper catalyst on a silica carrier in the temperature range between 300 and 600 °C [197]. While the catalyst suffered from coke formation under steam reforming conditions, the addition of oxygen to the feed reduced both coke formation and carbon monoxide selectivity. By-products such as ethylene and acetaldehyde were not reported by these workers. 

Ammonia production from natural gas includes the following processes desulfurization of the feedstock primary and secondary reforming carbon monoxide shift conversion and removal of carbon dioxide, which can be used for urea manufacture methanation and ammonia synthesis. Catalysts used in the process may include cobalt, molybdenum, nickel, iron oxide/chromium oxide, copper oxide/zinc oxide, and iron. 

Five main types of CNFs, platelet (P-CNF), tubular (T-CNF), thick herringbone (thick FI-CNF), thin herringbone (thin H-CNF) and very thin herringbone (very thin FI-CNF) vere selectively prepared and examined as supports of anode catalysts for DMFCs. P-CNF was synthesized from carbon monoxide over a pure iron catalyst at 600 °C, whereas thick H-CNF was obtained from ethylene over a copper-nickel catalyst [Cu-Ni (2 8 w/w)]. An Fe-Ni alloy (6 4 w/w) was used for the selective synthesis of T-CNFs from carbon monoxide gas at 650 °C [15, 16]. 

The activity of the usual metallic hydrogenation catalysts (nickel, cobalt, palladium, and platinum) for the hydrogenation of ethylenic substances is impaired by carbon monoxide. Carbon monoxide also has been shown to inhibit the catalytic activity of a copper hydrogenation catalyst (Pease and Stewart, 6). 

The pairing of copper with platinum and nickel with palladium was reminiscent of the work of Taylor and McKinney (3) who pointed out that copper and platinum were relatively poor catalysts for the hydrogenation of carbon monoxide to methane, while nickel and palladium were active catalysts for this reaction. Although this pattern could be coincidental, it is more reasonable and productive to assume a relationship between the spectroscopic results and the catalytic activities and to conclude that metals which chemisorb carbon monoxide in... 

The idea is not new that dissolved hydrogen can modify the activity of metal catalysts. Hall and Emmett (9) list a large number of workers who have supplied supporting evidence. Emmett, Kokes, and Hall showed that the behavior of dissolved hydrogen can be quantitatively related to the behavior Of copper-nickel alloys. This important contribution bears directly on the present discussion because the effect of adding copper to nickel is also amenable to study by means of the spectra of chemisorbed carbon monoxide. 

This is shown by the facts that the aldehyde-hydrogen ratio is only 35.7 per cent and the gas composition shows 60 per cent hydrogen, 20 per cent carbon monoxide, and 15-17 per cent methane. The presence of 8 per cent water in the ethanol apparently has no protective effect on the aldehyde as it does in the presence of copper catalysts." Because of this undesirable activity in promoting aldehyde decomposition, nickel catalysts are not applicable to the dehydrogenation of ethanol or alcohols in general. 

Normal propyl alcohol is readily dehydrogenated to the corresponding aldehyde at temperatures of 230° to 300° C. in the presence of copper catalysts. At temperatures of 400° C. as much as 25 per cent may be destroyed, however, by decomposition to carbon monoxide and ethane. In the presence of nickel 75 per cent of the aldehyde may be decomposed at a temperature as low as 260° C. Although the alcohol is dehydrogenated very readily over platinum at 280°, the aldehyde is completely destroyed at 300° C ... 

Since methanol is a direct reaction product of hydrogen and carbon monoxide, it is theoretically possible by using an excess of carbon monoxide in the original water gas mixture to form first methanol and then acetic acid or ester in one operation. With this end in view, catalysts composed of metals or their compounds, i.e. of nickel, chromium, cobalt, copper, cadmium, or manganese, have been patented.1"4 Catalysts similar to those proposed for the carbon monoxide-methanol reaction and comprising the oxides of copper, tin, lead, the acetate of copper, or tire methylates of aluminum or tin, or mixtures have been claimed for the same reaction at pressures of 150 to 200 atmospheres and at about 300° C.1 4e... 

The best catalyst was found to consist of zinc oxide and copper (or copper oxide) with an admixture of compounds of chromium. The success of the operation depended upon (a) the absence of alkali, which would cause decomposition of the methanol and the production of higher alcohols and oily products, and (b) the complete elimination of all metals except copper, aluminum and tin from those parts of the apparatus which come in contact with the reacting gases. Contact of carbon monoxide with iron, nickel, or cobalt had to be avoided since they formed volatile carbonyls winch deposited metal, by decomposition, on the active catalyst surface and thereby acted as poisons to destroy activity. 

The reduction can be carried out in batches or continuously at about 9,000 psig and 125 C in an ammonia atmosphere, over a cobalt-copper catalyst, in yields of over 90 per cent of theory. A number of other catalysts have been described for this reaction, including Raney nickel, cobalt on silica, and cobalt-silver-magnesium. The starting nitrile must be quite pure to avoid poisoning the catalyst. It is claimed that the presence of carbon monoxide, in addition to hydrogen and ammonia, extends the life of the cobalt catalysts normally used. ... 

Catalytic reductions have been carried out under an extremely wide range of reaction conditions. Temperatures of 20 C to over 300 C have been described. Pressures from atmospheric to several thousand pounds have been used. Catal3rsts have included nickel, copper, cobalt, chromium, iron, tin, silver, platinum, palladium, rhodium, molybdenum, tungsten, titanium and many others. They have been used as free metals, in finely divided form for enhanced activity, or as compounds (such as oxides or sulfides). Catalysts have been used singly and in combination, also on carriers, such as alumina, magnesia, carbon, silica, pumice, clays, earths, barium sulfate, etc., or in unsupported form. Reactions have been carried out with organic solvents, without solvents, and in water dispersion. Finally, various additives, such as sodium acetate, sodium hydroxide, sulfuric acid, ammonia, carbon monoxide, and others, have been used for special purposes. It is obvious that conditions must be varied from case to case to obtain optimum economics, yield, and quality. 

Synthesis of Liquid Hydrocarbons by the Reduction of Carbon Mon-dxide. When carbon monoxide-hydrogen mixtures are passed over cobalt, iron, nickel, and some copper catalysts that are promoted with certain metallic oxides, particularly oxides of the alkali mietals, at temperatures in the range frmn about 200-300°C and pressures from about 1-25 atm, various hydrocarbons are formed according to the following type of reactions ... 

Investigations into these topics are presented in this volume. Iron, nickel, copper, cobalt, and rhodium are among the metals studied as Fischer-Tropsch catalysts results are reported over several alloys as well as single-crystal and doped metals. Ruthenium zeolites and even meteo-ritic iron have been used to catalyze carbon monoxide hydrogenation, and these findings are also included. One chapter discusses the prediction of product distribution using a computer to simulate Fischer-Tropsch chain growth. 

Another Important concept introduced by Taylor was that of heterogeneity of surface-active centers.(25-26) This stemmed from observation of R. N. Pease that minute amounts of carbon monoxide, much smaller than the amount necessary to cover the surface, were sufficient to poison the surface of a copper catalyst. Taylor proposed that there were active centers on the surface while others argued that nickel impurities segregated preferentially on the surface and acted as catalyst. The variation of the heats of adsorption with surface coverage as determined by R. Beebe was used as evidence supporting the concept of active centers. In spite of the contradictory interpretation of the same experimental data, the concept of active centers has been a fruitful one. It inspired Imaginative research in the field of metal and oxide catalysis and has its present day expression in sophisticated surface physics studies. Subsequent work by coworkers of Turkevich at Princeton refined the nature of active centers in monodisperse metal particles and crystalline oxide catalysts. 

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