Nickel formate decomposition

Bircumshaw and Edwards [1029] showed that the rate of nickel formate decomposition was sensitive to reactant disposition, being relatively greater for the spread reactant, a—Time curves were sigmoid and obeyed the Prout—Tompkins equation [eqn. (9)] with values of E for spread and aggregated powder samples of 95 and 110 kJ mole-1, respectively. These values are somewhat smaller than those subsequently found [375]. The decreased rate observed for packed reactant was ascribed to an inhibiting effect of water vapour which was most pronounced during the early stages. 

References to a number of other kinetic studies of the decomposition of Ni(HC02)2 have been given [375]. Erofe evet al. [1026] observed that doping altered the rate of reaction of this solid and, from conductivity data, concluded that the initial step involves electron transfer (HCOO- - HCOO +e-). Fox et al. [118], using particles of homogeneous size, showed that both the reaction rate and the shape of a time curves were sensitive to the mean particle diameter. However, since the reported measurements refer to reactions at different temperatures, it is at least possible that some part of the effects described could be temperature effects. Decomposition of nickel formate in oxygen [60] yielded NiO and C02 only the shapes of the a—time curves were comparable in some respects with those for reaction in vacuum and E = 160 15 kJ mole-1. Criado et al. [1031] used the Prout—Tompkins equation [eqn. (9)] in a non-isothermal kinetic analysis of nickel formate decomposition and obtained E = 100 4 kJ mole-1. 

The kinetics of the decomposition [17] of thorium tetraformate to ThOj can be described by the Prout-Tompkins equation with = 150 kJ mol" from 498 to 553 K. The autocatalytic process was ascribed to participation of the oxide in breakdown of the carboxyl groups at the reaction interface to yield ThOj, formaldehyde and carbon dioxide as the primary products of reaction. The volatile products could, however, react further on the surface of the active solid to yield a number of secondary products amongst which the following gases were identified Hj, CO, HjO, CHjOH, HCOOCHj, HCOOH and (CHj). Addition of nickel formate to the reactant not only accelerated decomposition but also influenced the composition of the gases evolved, yielding predominantly CO, COj and H2 (which are the main products of nickel formate decomposition). 

Nickel formate dihydrate [15694-70-9] Ni(HCOO)2 is a green monoclinic crystalline compound which melts with decomposition to nickel... 

There have been many instances of examination of the effect of additive product on the initiation of nucleation and growth processes. In early work on the dehydration of crystalline hydrates, reaction was initiated on all surfaces by rubbing with the anhydrous material [400]. An interesting application of the opposite effect was used by Franklin and Flanagan [62] to inhibit reaction at selected crystal faces of uranyl nitrate hexa-hydrate by coating with an impermeable material. In other reactions, the product does not so readily interact with reactant surfaces, e.g. nickel metal (having oxidized boundaries) does not detectably catalyze the decomposition of nickel formate [222],... 

The addition of nickel formate to magnesium formate significantly reduced the decomposition temperature [1151]. The acceleratory period characteristic of the decomposition of pure Mg(HC02)2 was eliminated and the value of E was substantially diminished. For the double (Zn,Ba) and (Cu,Ba) formates, the rate of decomposition [1152] of the less stable component (Zn or Cu) was slower and that of the more stable component (Ba) more rapid than the values characteristic of pure preparations of these substances. 

RNi Raney nickel DNi catalyst prepared by the thermal decomposition of nickel formate HNi powder prepared by the hydrogenolysis of nickel oxide. 

An explanation for this difference in selectivity of the Ni catalysts is suggested by the studies of Okamoto et al. who correlated the difference in the X-ray photoelectron spectra of various nickel catalysts with their activity and selectivity in hydrogenations (ref. 28,29). They find that in individual as well as competitive hydrogenations of cyclohexene and cyclooctene on Ni-B, cyclooctene is the more reactive while the reverse situation occurs on nickel prepared by the decomposition of nickel formate (D-Ni). On all the nickel catalysts the kinetically derived relative association constant favors cyclooctene (ref. 29). The boron of Brown s P-2 nickel donates electrons to the nickel metal relative to the metal in D-Ni. The association of the alkene with the metal is diminished which indicates that, in these hydrocarbons, the electron donation from the HOMO of the alkene to an empty orbital of the metal is more important than the reverse transfer of electron density from an occupied d-orbital of the metal into the alkene s pi orbital. 

Various active nickel catalysts obtained not via reduction of nickel oxide with hydrogen have been described in the literature. Among these are the catalysts obtained by the decomposition of nickel carbonyl 10 by thermal decomposition of nickel formate or oxalate 11 by treating Ni-Si alloy or, more commonly, Ni-Al alloy with caustic alkali (or with heated water or steam) (Raney Ni) 12 by reducing nickel salts with a more electropositive metal,13 particularly by zinc dust followed by activation with an alkali or acid (Urushibara Ni) 14-16 and by reducing nickel salts with sodium boro-hydride (Ni boride catalyst)17-19 or other reducing agents.20-24... 

Thus an active nickel catalyst may be prepared simply by heating the formate in oil at around 240°C for about 1 h this method has been employed in the oil-hardening industry for the preparation of a wet-reduced catalyst,42 although the decomposition temperature is too high for normal oil-hardening and the catalyst may not be prepared directly in a hydrogenation tank, particularly for edible purposes. Nickel formate is prepared by the reaction between nickel sulfate and sodium formate,43 or the direct reaction of basic nickel carbonate44 or nickel hydroxide with formic acid.31... 

Ni Catalyst from Ni Formate (byAllisson et al.)45 In this method 100 g of nickel formate with 100 g of paraffin and 20 g of paraffin oil are heated in a vacuum of water-stream pump. At 170-180°C the water of crystallization is evolved out first (in 1 h). About 4 h at 245-255°C is required for complete decomposition. The end of the decomposition can best be found by the pressure drop to 20 mmHg. The still hot mass is poured on a plate after solidification, the upper paraffin layer is removed as much as possible. The remaining deep black mass is washed with hot water until most of the paraffin is removed off with melt the remaining powder is washed with alcohol, and then many times with petroleum ether until no paraffin remains. 

Ni Catalyst from Ni Formate (by Sasa).41 A mixture of 2.6 g of nickel formate dihydrate (0.81 g Ni) and 20 g of freshly distilled diphenyl ether (or biphenyl or a mixture of diphenyl ether and biphenyl) is heated under stirring. The water of crystallization is removed with diphenyl ether. At 250°C, when diphenyl ether starts to boil, the mixture becomes black. After the decomposition for 2 h in boiling diphenyl ether, the nickel catalyst is filtered off at 40-50°C. The catalyst may be used immediately or after washing with alcohol or benzene. 

Sasa prepared an effective nickel catalyst for the hydrogenation of phenol by decomposition of nickel formate in a high boiling solvent such as diphenyl ether and diphenyl. The catalyst thus prepared proved more active than Ni-kieselguhr in the hydrogenation phenol (eq. 11.12) and could be used repeatedly more than six times.71... 

X-ray photoelectron (XPS) studies of nickel boride, nickel phosphide, Raney nickel and Urushibara nickel showed that the electron density on the nickel was a function of the other metal present in these catalysts. 28J29 Boron, aluminum (Raney nickel) and zinc (Urushibara nickel) all increased the electron density on the nickel while phosphorous was an electron acceptor. Comparing the electron densities on the nickel in these catalysts with that on a nickel black prepared by the thermal decomposition of nickel formate (D-Ni) gave the series Ni-B > Ni-Al > Ni-Zn > D-Ni > Ni-P. 

An electronic effect was also used to explain the difference in 1,3-butadiene hydrogenation selectivity observed over various types of nickel catalysts such as Ni(B), Raney nickel, nickel powder from the decomposition of nickel formate, Ni(P), and Ni(S). As discussed in Chapter 12, chemical shifts in XPS binding energies (Aq) for the various nickel species were compared with that of the decomposed nickel catalyst to determine the extent of 1-butene formation as related to the electron density on the metal. The higher the electron density, the more 1-butene formation was favored. 

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... 

Nickel formate has been the subject of particular attention partly because of the suggestion that surface-bonded formate is formed during the nickel catalysed decomposition of formic acid. The role of this intermediate has been discussed in... 

The kinetics of decomposition of nickel formate [6,7] are sensitive both to the experimental conditions [8] and the reactant structure, ar-time curves for the isothermal decomposition (about 450 K) are usually [8], though not invariably [9], sigmoid and there is microscopic evidence [6] that reaction proceeds through nucleation and growth. The induction period [6] and the shape of the subsequent acceleratory process [8] are influenced by the rapidity with which product water vapour is removed from the vicinity of the reactant. Data fit the Prout-Tompkins equation with , about 100 kJ mol". ... 

Decomposition of nickel formate may be represented by the concurrent reactions [6,8,9] ... 

The role of the formate ion as an essential intermediate in the decomposition of formic acid on nickel metal [1-5] has not been quantitatively characterized, but its participation is consistent with the observations. It is probable, therefore, that the rate limiting steps for the catalytic reaction and the solid state decomposition of nickel formate are comparable. Further work is required to clarify the details of both reaction mechanisms. 

A comparative study of the thermal reactions in oxygen of the above three reactants [118], together with nickel formate, showed that the shapes of the ar-time curves were comparable with those for vacuum decompositions. The magnitudes of the Anhenius parameters (with the exception of the decomposition of the formate which does not give carbide product) were diminished. It was concluded that the initiation of reaction was unaffected by the presence of oxygen, so that the geometry of each rate process was unchanged. In the presence of Oj, interfacial reactions on the nickel oxide product (-+ COj + HjO) proceeded appreciably more rapidly by a common mechanism and all values of E, were close to 150 kJ mol. ... 

The decomposition products identified following reaction are not necessarily the primary compounds which result directly from the rate limiting step. Particularly reactive entities may rapidly rearrange before leaving the reaction interface and secondary processes may occur on the surfaces of the residual material which often possesses catalytic properties. The volatile products identified [144] from the decomposition of nickel formate were changed when these were rapidly removed from the site of reaction. The primary products of decomposition of thorium formate were identified [17] as formaldehyde and carbon dioxide, but secondary processes occurring on the residual thoria yielded several additional compounds. The oxide product similarly catalysed interactions between the primary products of decomposition of zinc acetate [145]. During the decomposition of rare earth oxalates, carbon monoxide disproportionates extensively to carbon dioxide and carbon [81,82]. 

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