Formic acid, nickel catalyzed

Compensation trends found for decomposition of formic acid on metal (and other) catalysts are represented diagrammatically in Fig. 7. Line I (Table III, Q) refers to reactions over nickel and copper (3, 190, 194, 236), gold (5,189,237), cobalt (137,194), and iron (194) the observations included in this group were obtained by selection, since other metals, which showed large deviations, were omitted [see also (5), p. 422], Line I is close to that calculated for the reaction catalyzed by nickel metal (Table III, R) (3, 137, 189-194, 238). Lines II (19,233) and III (3, 234, 235) (Table III, O and P) refer to decomposition on silver. The other lines were found for the same rate process on IV, copper-nickel alloys (190) V, oxides (47, 137), VI, tungsten bronzes (239) and VII, Cu3Au (Table III, S) (240a). 

Trillo et al. (47,137) have reported compensation behavior in oxide-catalyzed decomposition of formic acid and the Arrhenius parameters for the same reactions on cobalt and nickel metals are close to the same line, Table V, K. Since the values of E for the dehydration of this reactant on titania and on chromia were not influenced by doping or sintering, it was concluded (47) that the rate-limiting step here was not controlled by the semiconducting properties of the oxide. In contrast, the compensation effect found for the dehydrogenation reaction was ascribed to a dependence of the Arrhenius parameters on the ease of transfer of the electrons to the solid. The possibility that the compensation behavior arises through changes in the mobility of surface intermediates is also mentioned (137). 

Selective reduction to hydroxylamine can be achieved in a variety of ways the most widely applicable systems utilize zinc and ammonium chloride in an aqueous or alcoholic medium. The overreduction to amines can be prevented by using a two-phase solvent system. Hydroxylamines have also been obtained from nitro compounds using molecular hydrogen and iridium catalysts. A rapid metal-catalyzed transfer reduction of aromatic nitroarenes to N-substituted hydroxylamines has also been developed the method employs palladium and rhodium on charcoal as catalyst and a variety of hydrogen donors such as cyclohexene, hydrazine, formic acid and phosphinic acid. The reduction of nitroarenes to arylhydroxyl-amines can also be achieved using hydrazine in the presence of Raney nickel or iron(III) oxide. ... 

The acid-catalyzed hydrocarboxylation of alkenes (the Koch reaction) can be performed in a number of ways. In one method, the alkene is treated with carbon monoxide and water at 100-350°C and 500-1000-atm pressure with a mineral acid catalyst. However, the reaction can also be performed under milder conditions. If the alkene is first treated with CO and catalyst and then water added, the reaction can be accomplished at 0-50°C and 1-100 atm. If formic acid is used as the source of both the CO and the water, the reaction can be carried out at room temperature and atmospheric pressure.The formic acid procedure is called the Koch-Haaf reaction (the Koch-Haaf reaction can also be applied to alcohols, see 10-77). Nearly all alkenes can be hydrocarboxylated by one or more of these procedures. However, conjugated dienes are polymerized instead. Hydrocarboxylation can also be accomplished under mild conditions (160°C and 50 atm) by the use of nickel carbonyl as catalyst. Acid catalysts are used along with the nickel carbonyl, but basic catalysts can also be employed. Other metallic salts and complexes can be used, sometimes with variations in the reaction procedure, including palladium, platinum, and rhodium catalysts. The Ni(CO)4-catalyzed oxidative carbonylation with CO and water as a nucleophile is often called Reppe carbonylationP The toxic nature of nickel... 

For example, Fahrenfort et al. [42] considered the possible role of the intermediate formation of nickel formate in the nickel catalyzed decomposition of formic acid. They showed that when the volatile reaction products were rapidly removed, the carbon monoxide concentration was greater than that expected from the water-gas equihbriiun. When the gaseous products remained in contact with the residual solid, containing catalytically active nickel metal, the [C0]/[C02] ratio was that expected from the water-gas equilibrium. The composition of the primary products thus... 

Nitriles [1, 725-726, after citation of ref. 23]. The original method of Backeberg and Staskun23 for conversion of a nitrile to an aldehyde does not proceed well with hindered nitriles in this case, use of moist Raney nickel in formic acid is recommended.233 The formic acid serves as a source of hydrogen, and the nickel catalyzes both decomposition of the acid and reduction of the nitrile. 

Several experimental results support the adsorption mechanism for stationary conditions of the passive layer. Even the stationary passive current density depends on the composition of the electrolyte. For iron in 0.5 M H2SO4, the passive current density is 7 pA cm , whereas less than lpAcm is detected in 1 M HCIO4. From these observations, a catalysis for the transfer of Fe + from the passive layer to the electrolyte by S04 ions was concluded [55, 56]. Similarly, the dissolution Ni + from passive nickel and nickel base alloys is accelerated by organic acids hke formic acid and leads to a removal of NiO from the passive layer [57]. Additions of citrate to the electrolyte cause the thinning of passive layers on stainless steel and increase its Cr content [58]. Apparently Fe and Ni ions are complexed at the surface of the passive film, which causes an enhancement of their dissolution into the electrolyte. It should be mentioned that the dissolution of Cr " " apparently is not catalyzed by these anions and remains... 

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