Raney Cobalt Research Articles

Continuous Hydrogenation of Nitriles to Primary Amines with High Selectivity in Flow by Using Raney Cobalt

AbstractPrimary amines produced by selective catalytic hydrogenation of cyano compounds are widely used as basic chemicals, but due to the complexity of the hydrogenation mechanism and the inefficient mass transfer of the intermittent reaction, the process tends to produce secondary and tertiary amines as undesirable by‐products. In this research, a continuous hydrogenation system employing a micropacked‐bed reactor (μPBR) was established for the catalytic hydrogenation of 3‐ethylaminopropionitrile (3‐EAPN) to synthesize N‐ethyl‐1,3‐propanediamine (3‐EAPA). Under optimal experimental conditions using Raney cobalt as a catalyst, complete conversion of 3‐EAPN was achieved, and a high selectivity of 99.6 % for the primary amine (3‐EAPA) was obtained. On this basis, the system was extended with other cyano compounds of different structures as hydrogenation substrates, demonstrating the general applicability of this continuous hydrogenation system by using Raney cobalt as a catalyst in a μPBR for the hydrogenation of various nitriles.

Preparation of Raney cobalt and identification of surface structures responsible for catalytic activity in the Fischer–Tropsch process

AbstractA method for leaching Co2Al9 alloy was developed and optimized to produce nonpyrophoric Raney cobalt, which is used as a component of a highly efficient granular Fischer–Tropsch synthesis catalyst. A comparative study of the laboratory‐produced Raney cobalt with commercially available analog was done using the methods of low‐temperature nitrogen sorption, thermoprogrammed reduction (TPR), thermoprogrammed ammonia desorption, thermal analysis, thermal conductivity, and scanning and transmission electron microscopy. Partial dissolution of cobalt with the formation of Co2+ and Co3+ ions was detected during aluminum leaching. It was found that incomplete purification of commercial Raney cobalt from aluminum hydroxide impurity may lead to overestimation of specific surface area. It was also found that the acidity of the molded catalyst is mainly determined not by Raney cobalt, but by elements of the composite catalyst carrier. For the first time, a linear dependence between the content of structures in a Fischer–Tropsch synthesis catalyst with TPR‐AR maxima of 500–800°C and the amount of synthesized liquid hydrocarbons has been established. It is concluded that metal nanoparticles with partial charge transfer (Coδ+) are active centers of selective formation of C5+ hydrocarbons. Obtaining the maximum number of these centers and reaching a high thermal conductivity of the composite with a developed system of transport pores is a criterion for creating an effective cobalt catalyst for low‐temperature synthesis of hydrocarbons.

Playing with Fire? A Safe and Effective Deactivation of Raney Cobalt using Aqueous Sodium Nitrate

Sponge or skeletal metal catalysts (such as Raney-type hydrogenation catalysts) are ubiquitous and extensively used in large-scale industrial hydrogenation processes, including petrochemical refini...

Selective Synthesis of Furfurylamine by Reductive Amination of Furfural over Raney Cobalt

AbstractEffect of metal nature on reductive amination was investigated with biomass‐based furfural as a typical substrate. Among the tested heterogeneous metal catalysts, cobalt proved to be the most effective metal for the synthesis of the corresponding primary amine. Under a relatively mild reaction condition, 98.9 % yield of furfurylamine was obtained over Raney Co and it can be reused more than eight times without a significant decrease in the catalytic performance. By extensively studying the catalytic pathways and reaction mechanism, it is found that the selectivity to primary amine and secondary amine was governed by the relative rate of hydrogenolysis and hydrogenation of the Schiff base intermediate. The superiority of Raney Co in furfurylamine synthesis can be ascribed to its high efficiency on hydrogenolysis of the Schiff base intermediate and its low performance in the hydrogenation of the Schiff base, carbonyl group and furan ring. Furthermore, ammonia greatly promoted the catalytic hydrogenolysis of the Schiff base intermediate over Raney Co without clear deactivation of the metal active sites.

Preparation and application of a novel Raney nickel catalyst for fix-bed reactions

A unique cage-like structured carbon-composed Raney Nickel catalyst reinforced with in-situ grown carbon nanotubes is reported in this paper. Phenol formaldehyde resin was selected as carbon precursor to prepare this catalyst. NiAl alloy powder (48 wt% Ni) and powdery phenol formaldehyde resin were mixed firstly, and then the mixture was compressed, cured and carbonized, followed by alkaline leaching. The prepared carbon-composed catalyst possesses high stiffness, good hydrogen adsorption capacity, and perfect catalytic property. Hydrogenation of n-butyraldehyde to n-butanol was selected as a probe reaction. Compared with commercial catalyst, this cage-like carbon-composed Raney Nickel catalyst exhibits much higher selectivity and similar catalytic activity. It is believed that the use of carbon composing method will make a series of Raney metal catalysts, including but not limited to Raney nickel, Raney cobalt, and Raney copper, very important fix-bed catalysts for chemical industry.

The Palladium-Catalyzed Ullmann Cross-Coupling Reaction: A Modern Variant on a Time-Honored Process.

Cross-coupling reactions, especially those that are catalyzed by palladium, have revolutionized the way in which carbon-carbon bonds can be formed. The most commonly deployed variants of such processes are the Suzuki-Miyaura, Mizoroki-Heck, Stille, and Negishi cross-coupling reactions, and these normally involve the linking of an organohalide or pseudohalide (such as a triflate or nonaflate) with an organo-metallic or -metalloid such as an organo-boron, -magnesium, -tin, or -zinc species. Since the latter type of coupling partner is often prepared from the corresponding halide, methods that allow for the direct cross-coupling of two distinct halogen-containing compounds would provide valuable and more atom-economical capacities for the formation of carbon-carbon bonds. While the venerable Ullmann reaction can in principle achieve this, it has a number of drawbacks, the most significant of which is that homocoupling of the reaction partners is a competitive, if not the dominant, process. Furthermore, such reactions normally occur only under forcing conditions (viz., often at temperatures in excess of 250 °C). As such, the Ullmann reaction has seen only limited application in this regard, especially as a mid- to late-stage feature of complex natural product synthesis. This Account details the development of the palladium-catalyzed Ullmann cross-coupling reaction as a useful method for the assembly of a range of heterocyclic systems relevant to medicinal and/or natural products chemistry. These couplings normally proceed under relatively mild conditions (<100 °C) over short periods of time and, usually, to the exclusion of (unwanted) homocoupling events. The keys to success are the appropriate choice of coupling partners, the form of the copper metal employed, and the choice of reaction solvent. At the present time, the cross-coupling partners capable of engaging in the title reaction are confined to halogenated and otherwise electron-deficient arenes and, as complementary reactants, α- or β-halogenated, α,β-unsaturated aldehydes, ketones, esters, lactones, lactams, and cycloimides. Nitro-substituted (and halogenated) arenes, in particular, serve as effective participants in these reactions, and the products of their coupling with the above-mentioned carbonyl-containing systems can be manipulated in a number of different ways. Depending on the positional relationship between the nitro and carbonyl groups in the cross-coupling product, the reduction of the former group, which can be achieved under a range of different conditions, provides, through intramolecular nucleophilic addition reactions, including Schiff base condensations, access to a diverse range of heterocyclic systems. These include indoles, quinolines, quinolones, isoquinolines, carbazoles, and carbolines. Tandem variants of such cyclization processes, in which Raney cobalt is used as a catalyst for the chemoselective reduction (by dihydrogen) of nitro and nitrile groups (but not olefins), allow for the assembly of a range of structurally challenging natural products, including marinoquinoline A, (±)-1-acetylaspidoalbidine, and (±)-gilbertine.

Continuous Selective Hydrogenation of Refametinib Iodo-nitroaniline Key Intermediate DIM-NA over Raney Cobalt Catalyst at kg/day Scale with Online UV–Visible Conversion Control

The continuous selective hydrogenation of the iodo-nitroaromatic refametinib active pharmaceutical ingredient (API) intermediate (2,3-difluoro-5-methoxy-6-nitro-phenyl)-(2-fluoro-4-iodo-phenyl)-amine (DIM-NA) to the corresponding iodo-aniline 3,4-difluoro-N2-(2-fluoro-4-iodo-phenyl)-6-methoxy-benzene-1,2-diamine (DIM-DAB) was investigated using a conventional Raney cobalt catalyst in a cocurrent trickle-bed reactor. Suitable reaction conditions targeting full conversion and high selectivity, that is, low degrees of hydro-dehalogenation of the labile iodine substituent, were evaluated in investigations employing a short 4 mL screening reactor. The process was then transferred to a longer 40 mL reactor. Raney cobalt was found to be a highly selective catalyst, yielding only very small amounts of the desiodinated aniline desiodo-DIM-DAB or other side products. Productivities up to 144 g/h crude DIM-DAB were achieved operating the 40 mL reactor with a 0.2 M reactant solution in the presence of 3.4 equiv of H2 at 60 °C. Inlet pressure resulting from the flow rate increase was identified as a key parameter for successful throughput maximization. One kilogram of starting material was eventually converted to DIM-DAB in high yield and excellent quality within 8 h runtime. Online monitoring of the UV–vis absorption of the product stream allowed for conversion control and fast detection of process variations. Compared to the available DIM-NA batch reduction procedures, processing in continuous flow proves convincing by the safe implementation and reusability of the Raney type catalyst within a strongly intensified and highly selective process.

Synthesis of Renewable High-Density Fuel with Cyclopentanone Derived from Hemicellulose

1-(3-Cyclopentyl)cyclopentyl-2-cyclopentylcyclopentane, a renewable high-density fuel, was first produced in a high overall carbon yield (∼70%) with cyclopenanone that can be derived from hemicellulose. The synthetic route used in this work contains three steps. In the first step, 2-cyclopentyl cyclopentanone was synthesized for the first time by a one-pot reaction of cyclopentanone and hydrogen under the catalysis of Raney metal and alkali hydroxides. Over the optimized catalyst (Raney cobalt + KOH), a high carbon yield (83.3%) of 2-cyclopentyl cyclopentanone was achieved at 353 K. In the second step, 2-cyclopentyl-5-(2-cyclopentylcyclopentylidene)cyclopentanone was produced in a high carbon yield (95.4%) by the solvent-free self-aldol condensation of 2-cyclopentyl cyclopentanone under the vacuum conditions. In the third step, the 2-cyclopentyl-5-(2-cyclopentylcyclopentylidene)cyclopentanone was hydrodeoxygenated over the Ni-SiO2 catalyst under solvent-free conditions. High carbon yields of 1-(3-cyclopen...

A Raney Cobalt Mediated Reductive Cyclization Route to the Uleine Alkaloid Gilbertine.

Reductive cyclization of the 2,4,5-trisubstituted cyclohexenone 16 using dihydogen in the presence of Raney cobalt afforded compound 17 (60%) that could be elaborated over a further five steps, including one involving a cationic cyclization process, into the racemic modification of the unusual uleine alkaloid gilbertine. Single-crystal X-ray analyses of compounds (±)-1, 16, and a derivative of 17 are reported.

Palladium-Catalyzed Ullmann Cross-Coupling/Tandem Reductive Cyclization Route to Key Members of the Uleine Alkaloid Family.

The trisubstituted cyclohexenone 12, generated through a palladium-catalyzed Ullmann cross-coupling reaction between o-iodonitrobenzene and a 4,5-trans-disubstituted 2-iodo-2-cyclohexen-1-one, engaged in a tandem reductive cyclization process upon exposure to hydrogen gas in the presence of Raney cobalt. As a result, the 1,5-methanoazocino[4,3-b]indole 13 was obtained and this could be readily elaborated to the racemic modifications of the alkaloids uleine, dasycarpidone, noruleine, and nordasycarpidone (1-4, respectively).

Effective Conversion of Heteroaromatic Ketones into Primary Amines via Hydrogenation of Intermediate Ketoximes

A process to access heteroaromatic primary amines from the corresponding heteroaromatic ketones has been developed. A broad range of previously reported methods to convert ketones to primary amines was examined on heterocyclic ketones without success, including Leuckart–Wallach conditions, borane reductions, and transition-metal-catalyzed hydrogenations. Unique among the catalysts examined, Raney cobalt produced the desired primary heterocyclic amine. Raney cobalt hydrogenation of structurally varied heterocyclic ketoximes was demonstrated to form primary amines in good selectivity under mild conditions, and the products are easily isolated in high yield. Additionally, this is the first report of a systematic evaluation of the capabilities of Raney cobalt as an oxime hydrogenation catalyst.

Development of Raney cobalt catalysts for the hydrogenation of squalene type compounds

Raney™ cobalt catalysts were synthesized from an aluminum–cobalt alloy by leaching with sodium hydroxide solution at ~41 and 100 °C with and without the addition of ammonium molybdate. For the products synthesized at 100 °C, the surface areas of the catalysts were lower and the pore sizes were correspondingly larger. The surface areas were higher and average pore openings smaller when molybdate was included in the preparation. The X-ray diffraction measurements indicated that the Mo promoted catalysts have smaller average crystallite size than the unpromoted ones. The SEM micrographs confirmed that the surface morphology at low temperature synthesis is finer than at higher temperature. The NEXAFS spectra showed the ratio of elemental cobalt to cobalt oxide on the surface increases during the addition of molybdenum precursor, suggesting the Mo addition stabilizes the metallic cobalt from coarsening. The NEXAFS spectra also suggested that the cobalt oxide causes the blocking of small pores. Molybdenum(IV) species act by adsorption on the surface of the catalysts inhibiting the dissolution of the cobalt and subsequent re-precipitation as an oxide. Catalytic testing was conducted using squalene as a model compound for bio-oil from the algae Botryococcus braunii. A better hydrogenation yield is achieved when Raney™ cobalt catalyst is modified with molybdenum.

Glycerol dehydroxylation in hydrogen on a Raney cobalt catalyst

Glycerol dehydroxylation on a Raney cobalt catalyst in hydrogen was studied. It was found that with an increase in temperature from 140 to 200°C at a hydrogen pressure of 30 MPa, glycerol conversion increases from 14 to 97%. The glycerol is completely converted in 20 h, and the yield of 1,2-propanediol is 40%. With an increase in H2 pressure from 3 to 8 MPa, the glycerol conversion increases from 34 to 95%, and the yield of 1,2-propanediol increases from 18 to 38%. The maximum yield of 1,2-propanediol is 44% at 200°C and a hydrogen pressure of 3 MPa. The glycerol dehydroxylation in hydrogen on heterogeneous catalysts can be considered a promising method of glycerol conversion when glycerol is a byproduct of biodiesel manufacture from vegetable oil and animal fats.

Leaching process in the preparation of Raney cobalt catalyst

Raney metal type Co–Al alloy consisting of 36 wt% Co and 64 wt% Al was prepared by melting cobalt and aluminum metals in argon atmosphere, and then by solidification the resultant intermetallic compound. Raney Co catalyst was prepared by leaching out aluminum from Co–Al alloy with sodium hydroxide solution. The effects of reaction temperature (10, 25 and 40 °C), concentration of sodium hydroxide (2, 4 and 6 M), solid to liquid ratio (2, 3 and 4 g/L) on the leaching were investigated by following the increase of the amount of aluminum in the reaction mixture. The structural properties of the alloy and the catalyst were examined by XRF, SEM, XRD and BET analysis. The kinetic model best fitting the experimental results among various models was determined.

Effect of Chromate Addition on the Structure and Kinetics of Leaching for the Formation of Promoted Skeletal (Raney) Cobalt Catalysts

The internal porous structure of a chromia-promoted skeletal cobalt catalyst was directly and clearly imaged for the first time. The structure was made finer by the addition of sodium chromate to the leaching solution during preparation, and this resulted in a higher BET (Brunauer, Emmett, and Teller) surface area. Leaching proceeded with a sharp reaction front and followed an Avrami-Erofe'ev kinetic equation. A full quantitative model including parameters for particle size, chromate concentration, and temperature was derived. The activation energy of 75 kJ mol-1 was not significantly different from that for unpromoted cobalt. The mechanism of producing the finer structure in light of the kinetic information is discussed in terms of the exposed aluminum surface area.

Raney Cobalt: An Effective and Recyclable Catalyst for the Pauson—Khand Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Raney Cobalt Catalyzed Pauson-Khand Reaction

Commercially available Raney cobalt was applied to the intra- and intermolecular Pauson-Khand reaction. Thus, the reaction of 1a was performed with Raney cobalt under CO atmosphere in THF to give 2a in 94.5% conversion with 96.8% selectivity. The catalyst was reused five times with a slight loss of catalytic activity. Seven examples of the Pauson-Khand reaction were examined under similar conditions [Raney cobalt (6-16 mol%), CO (23-35 bar)] to afford cyclopentenones 2a-g with 54.2-99.5% conversion and 91.5-98.0% selectivity.

Raney Cobalt: An Effective and Recyclable Catalyst for the Pauson–Khand Reaction

AbstractCommercially available Raney cobalt is broadly applicable as a catalyst in intra‐ and intermolecular Pauson–Khand reactions (PKR). The activity of Raney cobalt compares favourably with that of previously described heterogeneous or heterogenised cobalt systems. The major reaction pathway appears to occur at the solid catalyst which can be efficiently separated and reused by filtration and/or exploiting its ferromagnetic properties.

Racemization of R-2-amino-1-butanol catalyzed by a fixed-bed Raney cobalt catalyst

Racemization of R-2-amino-1-butanol proceeded effectively over a fixed-bed Raney cobalt catalyst in a continuous fixed-bed reactor under the hydrogen pressure in the range of 2.0–6.0 MPa. The performance of a fixed-bed Raney cobalt catalyst was compared with that of a pulverous Raney cobalt catalyst. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), environment scanning electron microscopy (ESEM) and N 2 adsorption measurement (BET). The activity and stability of the fixed-bed Raney cobalt catalyst and the effects of concentration, temperature and hydrogen pressure were examined. Racemic 2-amino-1-butanol was obtained with a total yield of over 76% under the optimum reaction conditions. Thus, an effective process for the racemization of R-2-amino-1-butanol has been established.

Structure-selectivity relationship in the chemoselective hydrogenation of unsaturated nitriles

Several unsaturated nitriles of various structures (cinnamonitrile, cyclohex-1-enyl-acetonitrile, acrylonitrile, 3,3-dimethyl-acrylonitrile, geranylnitrile, and 2- and 3-pentenenitrile) with different substituents at the double bond were hydrogenated over Cr-doped Raney cobalt and nickel and over their undoped equivalents. The substitution and the position of the double bond relative to the nitrile group are crucial in determining the chemoselectivity for the unsaturated amine. The double bond is not hydrogenated when it is sterically hindered or if it is too far from the nitrile group (cyclohex-1-enyl-acetonitrile, double bond at C-6 in geranylnitrile). In conjugated systems, such as acrylonitrile or 2-pentenylnitrile, the activated double bond is hydrogenated before the nitrile. An additional methyl substituent at the double bond enhances the selectivity for unsaturated amines and, thus, 3,3-dimethyl-acrylonitrile and geranylnitrile were hydrogenated with selectivity up to 40%. The highest selectivities for unsaturated amines (up to 90%) were reached during the hydrogenation of nonconjugated systems, such as cyclohex-1-enyl-acetonitrile and 3-pentenylnitrile.