Skeletal Nickel Catalyst Research Articles

Investigation of the selectivity and stereospecificity in the hydrogenation of butyne-2-diol-1,4 on skeletal palladium, nickel, and cobalt catalysts

1. In the presence of Pd/C, Ni, and Co skeletal catalysts, the hydrogenation of butyne-2-diol-1,4 proceeds with a high degree of selectivity (94–96%) and stereospecificity (95–97%). The main reaction product is cis-butenediol. 2. The formation of small amounts of butanediol and trans-butenediol is due to the mechanism of addition of hydrogen to butynediol and not to conversion of the butenediol formed. 3. Factors reducing the activity of the catalyst: aging, use of water as a solvent, introduction of alkali, and poisoning of the catalyst with pyridine, had no effect upon the selectivity and stereospecificity of the hydrogenation of butynediol. 4. Hydrogenation of cis-butenediol is accompanied by its stereoisomeric transformation. Transbutenediol is not isomerized under these conditions.

Influence of amines on the activity and selectivity of a skeletal nickel catalyst

1. The influence of amines and heterocyclic compounds containing nitrogen on the rate and selectivity of the hydrogenation of cyclopentadiene, tolane, and dimethylvinylethynylcarbinol was studied in the presence of a skeletal nickel catalyst. 2. In the presence of methylamine, butylamine, ethylenediamine, hexamethylenediamine, piperidine, 4-ethylpyridine, benzotriazole, and quinoline methiodide, cyclopentadiene, tolane, and dimethylvinylethynylcarbinol are selectively hydrogenated on a skeletal nickel catalyst to the corresponding monoolefinic compounds. Such selectivity may be explained by the reversible adsorption poisoning of the catalyst. 3. In the presence of α-naphthylamine, diethylamine, diphenylamine, and 2-ethylpyridine, the hydrogenation of cyclopentadiene, tolane, and dimethylvinylethynylcarbinol is nonselective; the monoolefinic compounds formed are hydrogenated further, forming the fully hydrogenated compounds.

Reduction of esters of substituted ?-nitroacrylic acids on skeletal nickel catalyst

1. A study was made of the reduction of esters of substituted α-nitroacrylic acids on skeletal nickel in methanol medium. 2. Together with reduction, in the case of the ester of α-nitrocrotonic acid the addition of methyl alcohol also takes place. 3. The reduction of the methyl esters of the α-nitro-β-isopropyl-and α-nitro-β,β-dimethylacrylic acids goes in a normal manner, giving, after hydrolysis, DL-leucine and DL-valine, respectively.

Liquid-phase hydrogenation and irreversible catalysis of cyclohexene on a skeletal nickel catalyst

1. In the presence of a skeletal nickel catalyst, the rate of hydrogenation of cyclohexene in dilute alcohol solutions depends on the concentration. At concentrations of 0.5–5.0 millimoles/ml, the reaction proceeds at a constant rate. In the absence of a solvent, the reaction does not proceed. 2. Liquid-phase hydrogenation of cyclohexene on skeletal nickel at 20–60° is accompanied by a reaction of irreversible catalysis. Redistribution of hydrogen also occurs when the cyclohexene is in contact with the catalyst in an atmosphere of nitrogen. 3. The benzene and cyclohexane formed in the process of conversion of cyclohexene lower the reaction rate of the hydrogenation of cyclohexene.

Directed change in the selectivity of the action of catalysts in the process of hydrogenation of the dienone group Report 1. Hydrogenation of 6-methylheptadiene-3, 5-one-2 on nickel catalysts

1. The possibility of changing the selectivity of the action of a nickel catalyst in the process of hydrogenation of 6-methylheptadiene-3,5-one-2 was studied. 2. The hydrogenation proceeds nonselectively on skeletal nickel catalysts and in the presence of nickel catalysts on carriers: during the process of absorption of one mole of hydrogen two unsaturated ketones and a saturated ketone are formed. 3. It was proposed that the selective hydrogenation of the 3,4-double bond is accomplished by selective adsorption of dienone with the C=C-C=O group: by 1, 4-addition of hydrogen, or by direct hydrogenation of the 3, 4-double bond, in both cases with the participation of the C=O group. Considering this mechanism of hydrogenation and the catalytic peculiarities of zinc and cadmium, a composition of a Ni-ZnO-Cd catalyst was developed, in the presence of which the process occurs selectively: the 5,6-double bond is not hydrogenated. 4. The optimum conditions of the process, under which the yield of methylheptenone reaches 90% of the theoretical, were established. The proposed method of selective hydrogenation of dienone was checked on a continuous-action model setup.

Mechanism and kinetics of catalytic hydrogenation in liquid phase: Some of the principles of hydrogenation of unsaturated hydrocarbons over a skeletal nickel catalyst

Mechanism and kinetics of catalytic hydrogenation in liquid phase: Some of the principles of hydrogenation of unsaturated hydrocarbons over a skeletal nickel catalyst

Hydrogenation of isoprene and binary mixtures of isopentenes on a skeletal nickel catalyst

Hydrogenation of isoprene and binary mixtures of isopentenes on a skeletal nickel catalyst

Reaction sequence in hydrogenation of piperylene over skeletal nickel catalyst

The reaction mechanisms operating in the chain growth to C3+ primary alcohols and in the formation of ketones, secondary alcohols, methyl esters, ethers, and hydrocarbons during higher alcohol synthesis (HAS) over high-temperature modified methanol catalysts have been investigated by the temperature-programmed surface reaction (TPSR) technique. Experiments with linear and branched C4 alcohols, aldehydes, and acids over an unpromoted ZnCr oxide sample have indicated a series of major catalyst functions, namely aldol-like condensation (also with oxygen retention reversal), decarboxylation and decarboxylative condensations, hydrogenation-dehydrogenation, dehydration and hydrolysis, along with isomerization and cracking. TPSR experiments with linear C4 molecules over K-promoted ZnCr oxide have demonstrated the effects of alkali addition on the catalyst functions. The relevance of these functions and of the associated chemical reactions during HAS has been discussed in the light of catalytic tests performed under real synthesis conditions. The results are supportive of a mechanism of chain growth to C3+ primary alcohols based on a sequence of aldolic condensations of aldehydes, which do not operate over 2-methyl species. Formation of ketones under TPSR conditions is explained by decarboxylative condensation reactions of aldehydic and carboxylate species, as well as by aldol-like condensation reactions with oxygen retention reversal. Secondary alcohols detected in the products of the synthesis are formed by hydrogenation of ketones. Methyl esters and ethers are produced in the synthesis by alcoholysis of carboxylate and alkoxide species, respectively. Decarboxylation of carboxylate species, along with dehydration, may also play a role in the formation of hydrocarbons during HAS.

Investigation of the hydrogenation of ?-, ?-, and ?-acetylenic hydrocarbons in their binary mixtures over a skeletal nickel catalyst

1. In binary mixtures of normal α-acetylenic hydrocarbons (C5-C7), β-acetylenic hydrocarbons (C5-C6), and of β- and γ-acetylenic hydrocarbons (C5-C6), over a skeletal nickel catalyst the components of the mixture are hydrogenated simultaneously at identical rates. 2. In the first stage of the hydrogenation of binary mixtures of α- and β- and of α- and γ-acetylenic hydrocarbons, the α-acetylenic hydrocarbons are hydrogenated preferentially. 3. The C5-C7 acetylenic hydrocarbons studied and the olefins formed from them are hydrogenated in the following order, characterizing their relative adsorbabilities by a nickel catalyst: α-acetylenic hydrocarbons, β- and γ-acetylenic hydrocarbons, α-olefins, β- and γ-olefins.

A study of the selectivity and stereospecificity of the hydrogenation of n-pentynes on a skeletal nickel catalyst

THERE are no data in the literature on the catalytic hydrogenation ofpent1-yne. In papers [1-3] it is shown that the hydrogenation of pent-2-yne on a Pd catalyst gives cis-pent-2-ene. In a preceding investigation [4] we established that hex-l-yne hydrogenates on a skeletal nickel catalyst non-selectively. On the other hand, hex-2-yne and hex-3-yne, under analogous conditions, hydrogenate with a high degree of selectivity and stercospecificity. Similar results were obtained in the hydrogenation of a triple bond on Pd catalysts [5-7]. In the present work, the influence of the nature of the solvent, the concentration of the acetylenic hydrocarbon, and the amount of catalyst on the rate of selectivity, and stereospecificity of the hydrogenation of pent1-yne and pent-2-yne has been studied.

Effect of the nature of the solvent and the amount of skeletal nickel catalyst on the direction of addition of hydrogen to trans-piperylene

1. 1. It has been established that the direction and selectivity of hydrogenation on a skeletal nickel catalyst depends on the nature of the solvent and the amount of catalyst. 2. 2. The activity of the catlyst in iso-ocatane, decalin, and dimethylformide is lower than methyl alcohol, but rises with an increase in the amount of catalyst. 3. 3. It has been found that an increase of the specific activity of the catalyst leads to an increase in the seclectivity of the process and an increase in the yield of the thermodynamically less stable olefin- pent-1-ene.

Addition of alkoxysila nehydrides to unsaturated nitriles and hydrogenation of the ?-cyanoalkylalkoxysilanes obtained

1. The alkoxysilanehydrides add to CH2=CHCH2CN and CH2=CHCH2OCH2CH2CN at the double bond in the presence of platinum catalysts at atmospheric pressure. 2. The order of addition (according to Farmer's rule) of triethoxysilane and trichlorosilane to CH2=CHCH2CN and CH2=CHCH2OCH2CH2CN in the presence of platinum catalysts has been demonstrated. 3. The conditions for the hydrogenation of ω-cyanoalkylalkoxysilanes on skeletal nickel and cobalt catalysts to the corresponding ω-aminoalkylalkoxysilanes have been worked out.

The selectivity of the hydrogenation of 2-ethylanthraquinone over nickel catalyst

1. The selectivity of the hydrogenation of 2-ethylanthraqulnone on skeletal nickel catalyst in dioxane solution is practically independent of both the amount of catalyst and the temperature in the interval 20–80°. 2. Steam-treated nickel catalyst selectively catalyzes the hydrogenation of 2-ethylanthraquinone to the hydroquinone.

Selective reduction of adiponitrile to ?-aminocapronitrile on a nickel boride catalyst

1. The hydrogenation of adiponitrile to e -aminocapronitrile on a nickel boride catalyst and on skeletal nickel with titanium added was investigated. With an increase in the amount of titanium in the skeletal nickel catalyst, the selectivity of the latter increased. 2. The dinitrile was hydrogenated selectively to the aminonitrile on the nickel boride catalyst: 50–60% of the aminonitrile and only 2–5% of the diamine were formed under the optimal conditions. 3. The reason for the incomplete conversion of the dinitrile to the aminonitrile under half-hydrogenation conditions is adsorption displacement of the dinitrile by the aminonitrile. 4. In the hydrogenation of the dinitrile, cyclohexamethyleneimine is formed during the second stage of the process, while the formation of bishexamethylenetriamine increases appreciably when the dinitrile is hydrogenated in a mixture with hexamethylenediamine. As with other catalysts, ammonia suppresses the formation of both secondary amines. These facts confirm the aldimine mechanism for the hydrogenation of the dinitrile

Rate of hydrogenation of vinyl and allyl compounds of carbon, silicon, germanium, and tin on skeletal nickel

1. The rate of hydrogenation of compounds of the type (CH3)3MCH=CH2 and (CH3)3MCH2CH=CH2, where M is C, Si, Ge, and Sn, on a skeletal nickel catalyst falls in approximately the same order as the reactivity of these compounds in radical polymerization: Si > Ge > C > Sn.

Stability of skeletal nickel catalyst at elevated temperature

1. An investigation has been made of the thermal deactivation of a skeletal nickel catalyst in a current of nitrogen and in a vacuum. 2. It has been shown that a skeletal nickel catalyst is of good stability, to baking in a current of nitrogen in absence of organic substances. Its activity is not reduced by a two-hour baking at 300%; deactivation and dehydrogenation of the catalyst become appreciable only at 400° and higher, and they then become more and more marked as the temperature is raised. 3. When the catalyst is heated in a vacuum, its activity falls more rapidly than when treatment is carried out in a current of nitrogen. 4. The results obtained support our hypothesis that the most important cause of the loss in the activity of skeletal nickel catalyst under the usual conditions of hydrogenation is not recrystallization, but destruction of the active surface by chemical dehydrogenation and blocking.

Chemical method of investigating the metal-hydrogen nature of a skeletal nickel catalyst

1. A chemical method for the removal of hydrogen from a skeletal nickel catalyst is described; it serves at the same time as a method for the determination of the amount of chemically active hydrogen contained in the metal. 2. The method makes it possible to establish a relationship between the activity of a skeletal catalyst and its hydrogen content. 3. The effect of the amount of catalyst, the amplitude of the shake, and the dimensions of the flask on the reaction rate is also investigated.

Activity of a skeletal iron catalyst in hydrogenation reactions

1. A study has been made of the activity of skeletal iron catalyst in hydrogenation reactions. 2. It has been established that this catalyst has a considerable activity in hydrogenation reactions at 20° and normal pressure. 3. The activity of an iron catalyst for the hydrogenation of an ethylene bond is two to three times less than that of a skeletal nickel catalyst. 4. Compounds containing a triple bond are hydrogenated at a somewhat lower rate than compounds containing an ethylene bond. A carbonyl group is hydrogenated still more slowly.