Group 8 VIII copper

Hydrogenation Catalysts. The key to catalytic hydrogenation is the catalyst, which promotes a reaction which otherwise would occur too slowly to be useful. Catalysts for the hydrogenation of nitro compounds and nitriles are generally based on one or more of the group VIII metals. The metals most commonly used are cobalt, nickel, palladium, platinum, rhodium, and mthenium, but others, including copper (16), iron (17), and tellurium... 

The oxidation reaction between butadiene and oxygen and water in the presence of CO2 or SO2 produces 1,4-butenediol. The catalysts consist of iron acetylacetonate and LiOH (99). The same reaction was also observed at 90°C with Group (VIII) transition metals such as Pd in the presence of I2 or iodides (100). The butenediol can then be hydrogenated to butanediol [110-63-4]. In the presence of copper compounds and at pH 2, hydrogenation leads to furan (101). 

We plan to make studies on palladium-copper, iridium-copper, and platinum-copper catalysts to extend our investigation of the effect of varying miscibility of the components on the structural features of the bimetallic clusters present. With these additional systems, the whole range from complete immiscibility to total miscibility of copper with the Group VIII metal will be encompassed. 

The dominant role of copper catalysts has been challenged by the introduction of powerful group VIII metal catalysts. From a systematic screening, palladium(II) and rhodium(II) derivatives, especially the respective carboxylates62)63)64-, have emerged as catalysts of choice. In addition, rhodium and ruthenium carbonyl clusters, Rh COJjg 65> and Ru3(CO)12 e6), seem to work well. Tables 3 and 4 present a comparison of the efficiency of different catalysts in cyclopropanation reactions with ethyl diazoacetate under standardized conditions. 

Most Group VIII metals adsorb carbon monoxide dissociatively, and, consequently, they are good Fischer-Tropsch catalysts.240 In contrast, Pd, Pt, Ir, and Cu do not dissociate carbon monoxide. Of these metals, copper and more recently palladium were found to be excellent methanol-forming catalysts. 

One of the characteristic features of the metal-catalysed reaction of acetylene with hydrogen is that, in addition to ethylene and ethane, hydrocarbons containing more than two carbon atoms are frequently observed in appreciable yields. The hydropolymerisation of acetylene over nickel—pumice catalysts was investigated in some detail by Sheridan [169] who found that, between 200 and 250°C, extensive polymerisation to yield predominantly C4 - and C6 -polymers occurred, although small amounts of all polymers up to Cn, where n > 31, were also observed. It was also shown that the polymeric products were aliphatic hydrocarbons, although subsequent studies with nickel—alumina [176] revealed that, whilst the main products were aliphatic hydrocarbons, small amounts of cyclohexene, cyclohexane and aromatic hydrocarbons were also formed. The extent of polymerisation appears to be greater with the first row metals, iron, cobalt, nickel and copper, where up to 60% of the acetylene may polymerise, than with the second and third row noble Group VIII metals. With alumina-supported noble metals, the polymerisation prod-... 

The hydrogenation of but-2-yne in the gas phase has been investigated using alumina-supported Group VIII metals, other than palladium, and over copper—alumina [200,201], With the exception of copper, which was 100% stereoselective for c/s-but-2-ene formation, the distribution of the initial reaction products, as shown in Table 20, are more complex than was observed with palladium. 

Takezawa N, Iwasa N. Steam reforming and dehydrogenation of methanol difference in the catalytic functions of copper and group VIII metals. Catal Today. 1997 36(l) 45-56. 

Imaizumi et al. studied the hydrogenation of l,4-dialkyl-l,3-cyclohexadienes over the nine group VIII (groups 8-10) metals and copper in ethanol at room temperature and atmospheric pressure.122 The selectivity for monoenes formation at 50% conversion increased in the order Os-C, Ir-C < Ru-C, Rh-C, Pt < Pd-C, Raney Fe, Raney Co, Raney Ni, Raney Cu (= 100%). The selectivity for 1,4-addition product increased in the order Os-C, Ir-C < Ru-C, Rh-C, Raney Cu, Raney Fe, Raney Ni < Raney Co, Pd-C, Pt. Extensive formation of 1,4-dialkylbenzenes (more than 50% with the 1,3-dimethyl derivative) was observed over Raney Ni and Pd-C, while they were not formed over Raney Cu, Os-C, and Ir-C. In the hydrogenation of 4-methyl-1,3-pen -tadiene (39) (Scheme 3.15) over group VIII metals in cyclohexane at room temperature and atmospheric pressure, high selectivity to monoenes was obtained with iron, nickel, cobalt, and palladium catalysts where the amounts of the saturate 2-methylpen-... 

The most appropriate position for nickel in the Periodic Table is, as explained in Chapter I, the end of the first horizontal series of triads in Group VIII. An atomic weight greater than that of cobalt, namely, 58-97, but less than that of copper, namely, 63-57, is thus to be expected. 

The inclusion of iron, cobalt, nickel, and certain other metals in Group VIII.4 enables the alkali-metals lithium, sodium, potassium, rubidium, and caesium to be placed in their natural position as a subgroup of Group I. of the periodic system, in juxtaposition to the related sub-group containing copper, silver, and gold (p. 3). This arrangement... 

Copper and gold have oxidation numbers that exceed the group number. Most group VIII elements have maximum oxidation numbers that are not as large as the group number. 

A detailed stu of over 45 catalysts, primarily from Group VIII metal salts and complexes, showed palladium(II) compounds to be the most effective in the dehydrogenation of a variety of aldehydes and ketones. Soluble palladium(II) salts and complexes such as dichloro(tTiphenylphosphine)palladium(II) and palladium(II) acetylacetonate have been shown to be optimal, with the salts of rhodium, osmium, iridium and platinum having reduced efficacy. Since the d ydrogenation reaction is accompanied by reduction of the palladium(II) catalyst to palladium(0), oxygen and a cooxidant are required to effect reoxidadon. Copper(II) salts are favored cooxidants, but quinones, and especially p-benzoquinone, are also effective (Scheme 24). - ... 

Iron, cobalt, and nickel, with atomic numbers 26, 27, and 28, lie in the center of the first long period, and are described, with their congeners, the platinum metals, as group VIII of the periodic table. They show a. trend in their chemical properties, forming a transition from the metals chromium and manganese, which may assume several oxidation states, and whose higher oxides are acidic, to the more basic and less chemically versatile metals copper and zinc. 

Ammonium salts on treatment with alkali liberate ammonia, which can be detected by its odor and the fact that it will turn red litmus, blue. A more sensitive test utilizes the copper(II) ion, which is blue in the presence of ammonia [see Group VIII a(i)]. Ammonium salts will not give a positive hydroxamic acid test (Ih) as given by amides. 

The hydrogenation of 2-butyne has been studied over the other metals of Group VIII and over copper (84, 95) using a static system and alumina-supported catalysts in the temperature range 100 to 200°. Under these conditions more complex distributions of products have been observed than was the case for palladium at room temperature. 

To summarize, it may be said that the addition of hydrogen to 1,3-butadiene in gas phase reactions occurs partly by a 1-2-inechanism over all metal catalysts giving 1-butene in the gas phase. 2-Butene is either produced directly by a simultaneous 1-4-addition process as in the cobalt- and palladium-catalyzed reactions, or it is produced indirectly by the isomerization of 1-butene after its initial formation on the surface as is the case with the remaining metals of Group VIII and copper. The fraction of adsorbed olefin which is hydrogenated to w-butane depends upon the manner in which the thermodynamic and mechanistic factors, discussed previously, operate in each particular reaction. 

To test the hypothesis that the catalytic activity of a Group VIII metal is associated with an unfilled (/-band, various workers determined reaction rates on alloys such as nickel-copper and palladium-gold as a function of composition. It was reasoned that the extent of filling of the (/-band would be determined by the composition of the alloy hence it should be possible to relate catalytic activity to (/-band vacancies. 

This review is followed by a consideration of some of the features characteristic of hydrocarbon reactions on catalysts comprising individual metals from Groups VIII and IB of the periodic table. Finally, the activities of a series of unsupported nickel-copper alloys for hydrogenolysis and dehydrogenation reactions are discussed. These latter studies were made to obtain information on the selectivity phenomenon with bimetallic catalysts of known structure. The nickel-copper alloys were characterized by a variety of chemical and physical probes. 

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