Modified Nickel Catalyst Research Articles

Electron microscopic study of the structure of nickel catalysts modified with heteropoly compounds

The state of the active phase on the surface of low-percentage nickel catalysts on carbon supports in the presence of new modifiers, mixed series 12 heteropoly compounds (HPC), was investigated. The presence of a modifier causes an increase in the dispersion of the nickel, formation of nickel-HPC associates on the surface of the support, and determines the high dispersion and thermal stability of the Ni particles in reducing medium. Modified nickel catalysts have higher selectivity for coal oils during liquid-phase hydrogenation of coal, and the process takes place with less gas formation.

ChemInform Abstract: Enantio‐Differentiating Hydrogenation of 2‐Alkanones over Asymmetrically Modified Nickel Catalyst and Its Application to the Preparation of Optically Pure 2‐Alkanols.

Abstract2‐Alkanones such as (I) (used in most experiments) are stereospecifically hydrogenated over modified Raney‐Ni with an average optical yield of about 80% (optimum conditions).

Kinetics of liquid phase hydrogenation of cottonseed oil with nickel catalysts

AbstractThe hydrogenation of cottonseed oil has been carried out in a batch reactor using both unmodified and chromia modified nickel catalysts. The process variables include chromium to nickel atomic ratio (0.00–0.35), catalyst particle size (200–400 micron), temperature (120–140°C) and pressure (5–10 bar). Chromia was found to suppress the stearate formation completely, although it retarded the overall hydrogenation activity of nickel. Its optimum content in the catalyst was found to be 0.17 Cr/Ni atomic ratio; the data corresponded to 5 hr reaction time. The kinetics of the process was tested and found to follow a first order reaction with respect to linoleate and half order with respect to hydrogen. The activation energy was found to be 11.8 kcal/mole.

Enantio-differentiating Hydrogenation of 2-Alkanones over asymmetrically modified nickel catalyst and its application to the preparation of optically pure 2-alkanols

Enantio-differentiating hydrogenation of 2-alkanones over asymmetrically modified nickel catalyst was carried out with an average optical yield of about 80%. The factors affecting the optical yield of the reaction and their functions are discussed. A practical method for the optical enrichment of products of hydrogenation to optically pure 2-alkanols is also presented.

Electrohydrogenation of ethyl acetoacetate on a modified nickel catalyst

The enantioselective electrohydrogenation of ethyl acetoacetate in the region of the anodic and cathodic potentials of the Ni electrode-catalyst, in relation to the reversible hydrogen electrode, proceeds with the enantioselectivity of ∼10%.

The Preparation of Optically Pure 3-Hydeoxybutanoic Acid and Its Homologues as the Dibenzylammonium Salt

Abstract Optically pure (R)- and (S)-3-hydroxybutanoic acid and its homologues are prepared by the method consisting of the enantioface differentiating hydrogenation of methyl 3-oxoalkanoate to methyl 3-hydroxyalkanoate(80–90% e.e.) over asymmetrically modified nickel catalyst and the preferential crystallization of optically pure 3-hydroxyalkanoic acids from the hydrogenation products as the dibenzylammonium salts.

ChemInform Abstract: Preparation of an allo‐Threonine Derivative by Catalytic Hydrogenation of an α‐Acetylamino‐β‐ketobutyric Acid Ester on Modified Catalysts.

AbstractHydrogenation of the N‐acetyl amino ketobutyrate (II), prepared from the derivative (I), in the presence of a modified nickel catalyst leads to the stereoselective formation of N‐acetyl‐allo‐threonine (III).

The role of alkali halides in the enantioselective hydrogenation of a prochiral keto compound over modified nickel catalysts

Influences of alkali halides on the catalysis of tartrate-modified nickel in the asymmetric hydrogenation of a prochiral keto compound have been studied. The effects are shown to be dependent on the concentration of these salts in the reaction mixture. At low concentrations of Na or K halides the selectivity is enhanced, but at higher concentrations it drops below the value found in the absence of alkali halides. The concentration required for the selectivity maximum is two orders of magnitude higher for NaBr than for NaI, in accordance with the much stronger adsorption of the latter, found by direct determination of the adsorbed quantities. For a given anion, the effects on the selectivity strongly depend on the nature of the cation. The results are rationalized tentatively by assuming that alkali ions, by coordination with tartrate and substrate oxygens, modify the stereochemistry of the product-determining surface complex.

State of components in group IV A metal modified nickel catalysts prepared via decomposition of metal complexes

The dispersity and state of components in (M+Ni)/SiO2 catalysts (M=Ge, Sn, Pb), prepared via the reduction of anchored complexes, have been studied by chemisorption and electron microscopy. High dispersity of metallic particles (≈6A) has been revealed. According to Mossbauer spectroscopy, in (Ni+Sn)/SiO2 catalysts reduced at 873 K, a partial reduction of Sn to the metallic state is observed.

Asymmetric synthesis of 4-vinylcyclohexene using modified nickel catalysts

Optically active phosphines and cyclic phosphonites are used in the catalytic system Ni(O)/ligand/butadiene. The formation of 4-vinylcyclohexene as the only chiral dimer is monitored by the induced optical activity, and widely depends on the relative concentration and the nature of the ligands. The highest induction (35% e.e.) is found at 20 °C with 2-t-butyl-4,5-dicarbethoxy-1,3,2-dioxaphospholane.

The Enantioface-differentiating (Asymmetric) Hydrogenation of the C=O Double Bond with Modified Raney Nickel. XXXVI. The Development of Modified Nickel Catalysts with High Enantioface-differentiating Abilities

Abstract Various types of modified nickel catalysts were prepared and their enantioface-differentiating (asymmetric) abilities were examined. It was found that the presence of aluminum or related metal compounds in the catalyst was unfavorable for the effective enantioface-differentiating catalyst. The modification with a solution containing tartaric acid and inorganic salt gave a high enantioface-differentiating ability to Raney nickel and reduced nickel catalyst. Among the modified nickel catalysts examined, the Raney nickel modified with tartaric acid and sodium bromide gave the best result with respect to the hydrogenation activity and enantioface-differentiating ability (optical yield 88%). NaBr adsorbed on Raney nickel was found to inhibit the nonenantioface-differentiating hydrogenation.

The Effect of Crystallite Size of Nickel on the Enantioselectivity of Modified Nickel Catalysts

Abstract Enantioselective hydrogenation of methyl acetoacetate to methyl 3-hydroxybutyrate with various unsupported nickel catalysts modified by (2R,3R)-tartaric acid was studied under mild conditions in order to elucidate the dependence of the selectivity upon the surface states of the catalysts. The catalyst with the larger crystallite size has the higher enantioselectivity, presumably because of the higher probability to obtain large ensembles of regularlyarranged nickel atoms in the catalyst surface for the modifier to adsorb strongly and regularly. The nickel boride catalyst has very low enantioselectivity, mainly due to its amorphous structure. The detrimental effect of additives (B, P, and Al in Ni–B, Ni–P, and R–Ni catalysts) was explained as the effect of their lowering the crystallinity of the catalysts.

The Stereo-differentiating (Asymmetric) Hydrogenation of the C=O Double Bond with a Modified Nickel Catalyst. XXXV. A Facile Method for the Preparation of Optically Pure β-Diols

Abstract The hydrogenation of RCOCH2COR over a Raney nickel catalyst modified with a mixture of tartaric acid and NaBr gave (R*, R*-RCH(OH)CH2CH(OH)R selectively with a high optical purity. The substrates with R=CH3–, CH3CH2–, CH3CH2CH2–, CH3(CH2)4CH2–, and Ph– were employed in this study. In all cases, the recrystallization of the hydrogenation product gave an optically pure (R*,R*)-isomer which was free from the (R*,S*)-isomer.

The production of synthetic organic liquids from wood using a modified nickel catalyst

AbstractExtended batch reactions show that fast‐growing hybrid poplar suspended in water is completely converted to oil and some gas when stirred at 340°C in the presence of Raney nickel. The oil is less viscous when hydrogen is present at sufficiently high pressure. The catalyst is stable up to the maximum time studied (14 hours). The oils typically contain 77% carbon, 7.5‐8.5% hydrogen, and 12‐13% oxygen, have viscosities in the range 5000‐8000 mPa.s and higher heating values of around 35 MJ.kg−1. Nickel produced by reduction of nickel carbonate in situ is also an effective and more practical catalyst.

Asymmetrically Modified Nickel Catalyst Its Application to the Preparation of Optically Active 3-Hydroxyacid

Asymmetrically Modified Nickel Catalyst Its Application to the Preparation of Optically Active 3-Hydroxyacid

Enantioface-differentiating (Asymmetric) Hydrogenation of Keto Ester with Modified Nickel Catalyst. XXXII. Structural Requirements of Modifying Reagent and Substrate

Abstract The enantioface-differentiating hydrogenation of α-, β-, γ-, and δ-keto esters over α-, β-, and γ-amino acid–MRNi has been conducted. The optimum enantio-differentiating power of α-amino acid-MRNi has been found in the hydrogenation of the β-keto ester and that of β-amino acid-MRNi found in the hydrogenation of the γ-keto ester. The results have been explained in terms of the intermolecular recognition between substrate and modifying reagent through the functional groups.

Stereochemical Studies of the Hydrogenation with Asymmetrically Modified Nickel Catalysts; The Hydrogenation of Methyl 2-Alkyl-3-oxobutyrate

Abstract The hydrogenation of methyl 2-methyl-3-oxobutyrate (I) to methyl 3-hydroxy-2-methylbutyrate (III) was carried out with various types of asymmetrically modified nickel catalysts (MNi). The use of MNi always resulted in the deviation of the ratio, 2S/2R=((2S,3R)-III+(2S,3S)-III)/((2R,3R)-III+(2R,3S)-III, from 1/1, in spite of the use of racemic I. A catalyst giving a larger 2S/2R value always gave a larger 3R/3S value. These results led to the conclusion that the configurations at the C-2 and C-3 positions of the product were determined in the process of the formation of the complex between the substrate and the modifying reagent (the absorption step), not at the step of the hydrogen addition to the adsorbed substrate (the rate-determining step). The best optical yield and the highest ratio of erythro-III/threo-III were obtained when (R,R)-tartaric acid-MNi was used as a catalyst. The amounts of the isomers produced were in the following order: 2S,3R>>2R,3R≈2R,3S>2S,3S. Stereochemical models are proposed to account for the formation of the 2S,3R-isomer in a large excess.

Mechanism of asymmetric hydrogenation on modified nickel catalysts

Mechanism of asymmetric hydrogenation on modified nickel catalysts

The Catalytic Dehydrogenation, Dehydroxylation, and Dehydroxymethylation of Benzyl Alcohol. III. The Effect of Metal Chlorides as Additives

Abstract This paper will describe the reaction of benzyl alcohol in the presence of various kinds of modified stabilized nickel catalysts, which had been prepared from the mother catalyst by treating it with solutions of appropriate metal chlorides. The catalytic activities of each modified catalyst for the formation of benzene, toluene, and benzaldehyde were compared in terms of the fH,fCH3, and fCHO values; the selectivities for the formation of benzene and toluene against that of benzaldehyde, SH and SCH3, were also evaluated. In general, the formation of toluene and benzene was greatly affected both by the kind and by the amount of metal chlorides used as additives. The reaction was promoted by the addition of a proper quantity of alkali metal chloride. In the cases of the reactions by lowlymodified catalysts, the decreasing order of the fH and fCH3 values according to the kind of metal ion adsorbed on the catalyst was as follows: Na+≥K+>Co2+>Ca2+>Cd2+>Ba2+>Hg2+>Cu2+. On the other hand, in the higher degrees of modification, the corresponding order of the fH and fCH3 values was altered to be as follows: K+>Na+>Co2+>Cd2+>Ba2+≥Ca2+>Cu2+>Hg2+. With regard to the modified nickel catalysts treated with 0.08 n solutions, it was found that the sequence of the fH and fCH3 values due to the kind of metal ion was roughly correlated with that of the atomic numbers of the corresponding metals. The results are discussed in connection with the general concept of catalytic chemistry.