Raney Type Research Articles

Recycling of Spent Hydrodehalogenation Catalysts – Problems Dealing with Separation of Aluminium

Our study is focused on utilization and recycling of copper and nickel applicable for reductive degradation of tetrabromobisphenolA (TBBPA), the high use brominated flame retardant for printed circuit boards. Deactivated and/or poisoned hydrodebrominationcatalysts are produced by reductive destruction of brominated phenol (TBBPA) dissolved in alkaline aqueous solution using RaneyAl-Ni and/or Devarda´s Al-Cu-Zn alloys. Spent metallic slurry is treated with aqueous sulfuric acid to dissolve residual aluminiumand/or zinc and decanted residual metal is subsequently treated under oxidation conditions and dissolved in excess of mineralacid by co-action of oxidant. The corresponding metal salt is separated from corresponding leachates containing excess of acid byevaporation and recycling of volatile components. Obtained copper or nickel salts were used as sources of Raney type hydrodebrominationcatalysts produced for in-situ by action of NaBH4.

Microstructure Characterization of Ni-75 at.% Al Raney Type Alloy as a Result of Cooling Rate and Chromium Doping

The effect of cooling rate on the phase composition of gas atomized Raney type catalysts was studied using the Ni-75 at.% Al composition. The resulting particles were sieved into 3 standard size fractions and analysed using XRD with Rietveld refinement: as expected the three phases, Al3Ni2, Al3Ni, and Al-Al3Ni eutectic were identified. Differing phase compositions in the 3 size ranges were identified offering a possible explanation for varying catalytic activity with cooling rate, the higher cooling rates experienced by the smaller droplets allow less time for the peritectic conversion of Al3Ni2 to Al3Ni to proceed. This in turn results in a more Al-rich residual liquid, increasing the volume fraction of eutectic. This was further confirmed when analysing the microstructure using SEM backscatter imaging. Al3Ni2 was found to be encased in a shell of Al3Ni characteristic of peritectic reactions. The remainder of the alloy was found to consist of Al-Al3Ni eutectic. The SEM backscatter imaging also indicated that the larger particles displayed and a more globular structure than smaller particles. Similar Raney type Ni-75 at.% Al doped with 1.5 at.% Cr were synthesised using the same method and sieved into the same 3 standard size fractions. It was found that the Cr doped alloys exhibited a more dendritic character than the undoped samples in the corresponding size fraction, although the material still displayed an increasingly dendritic character with increasing cooling rate. The phase composition found by Rietveld refinement also followed a similar trend to the undoped samples with decreasing amounts of Al3Ni formed at the higher cooling rates. However, significant amounts of an additional phase, Al13Cr2, were also observed. Rietveld refinement found that a larger amount of Al13Cr2 was present than could be accounted for by the addition of 1.5 at.% Cr . This can be explained by the substitution of Ni onto the Cr lattice, as confirmed by Rietveld refinement. Al13Cr2 was found to be located mostly at the boundary of the Al3Ni and Al-Al3Ni eutectic phases during elemental mapping and quantitative image analysis of backscattered electron micrographs. This indicates that precipitation of Al13Cr2 is towards the end of the solidification process. The relatively large amounts of the Al-rich Al13Cr2 may explain the enhanced catalytic activity observed following leaching of Cr-doped Raney catalysts.

Effect of cooling rate and chromium doping on the microstructure of Al-25 at.% Ni Raney type alloy

Al-25 at.% Ni and Al-23.5 at.% Ni-1.5 at.% Cr alloys were synthesised via gas atomisation to study the effect of rapid cooling on the microstructure and phase composition of Raney type catalyst precursor powders. In the undoped powders, the three phases, Al₃Ni₂, Al₃Ni, and Al-Al₃Ni eutectic were identified, while in the Cr-doped powders the additional phase Al₁₃Cr₂ was also identified. Extensive substitution of Ni onto the Cr lattice sites is observed, which generates the observed phase fraction of Al₁₃Cr₂. Elemental mapping and quantitative image analysis of backscattered electron micrographs indicates that the Al₁₃Cr₂ phase precipitates late in solidification, probably direct from the melt, during the final stages of Al₃Ni growth. As such, this explains previous observations that Cr is found on the surface of the activated catalyst without the need to invoke migration of Cr. Leaching of such an Al-rich compound offers a plausible explanation for the enhanced catalytic activity observed in Cr-doped Raney catalysts.

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.

Heterogeneous Catalytic Reductive Amination of Carbonyl Compounds with Ni-Al Alloy in Water as Solvent and Hydrogen Source

The heterogeneous catalytic reductive amination of carbonyl compounds has been achieved by reactions of ammonium hydroxide and various amines with ketones and aldehydes. The process is based on the application of Raney type Ni-Al alloy in an aqueous medium. The reaction of the carbonyl compounds with the amine provided the corresponding Schiff bases that immediately underwent a reduction to provide primary and secondary amines as products. The controlled reaction of the Al content of the alloy with the solvent water generates hydrogen, and the in situ formed Raney Ni^® serves as a hydrogenation catalyst. The method is a simple and efficient way of preparing a broad variety of primary and secondary amines.

A microstructural investigation of gas atomized Raney type Al-27.5 at.% Ni catalyst precursor alloys

Quantitative image analysis has been used to investigate the phase composition of gas atomized powders of a Raney type Ni catalyst precursor alloys of composition Al-27.5 at.% Ni in the powder size range 150–212 μm. We find that there are considerable variations in phase composition both between powders from the same batch and as a function distance from the particle surface within individual particles. Such variations may have significant implications for the future production and uptake of such catalysts, including the necessity for post-production crushing of gas atomized powders. Models are proposed to account for both variations.

Catalysis by Unsupported Skeletal Gold Catalysts

Catalysis is one of the key technologies for the 21st century for achieving the required sustainability of chemical processes. Critical improvements are based on the development of new catalysts and catalytic concepts. In this context, gold holds great promise because it is more active and selective than other precious metal catalysts at low temperatures. However, gold becomes only chemically and catalytically active when it is nanostructured. Since the 1970s and 1980s, the first type of gold catalysts that chemists studied were small nanoparticles on oxidic supports. With the later onset of nanotechnology, a variety of nanostructured materials not requiring a support or organic stabilizers became available within about the last 10 years. Among these are gold nanofoams generated by combustion of gold compounds, nanotube membranes prepared by electroless deposition of gold inside a template, and corrosion-derived nanoporous gold. Even though these materials are macroscopic in their geometric dimensions (e.g., disks, cubes, and membranes with dimensions of millimeters), they are comprised of gold nanostructures, for example, in the form of ligaments as small as 15 nm in diameter (nanoporous gold, npAu). The nanostructure brings about a high surface to volume ratio and a large fraction of low coordinated surface atoms. In this Account, we discuss how unsupported materials are active catalysts for aerobic oxidation reaction in gas phase (oxidation of CO and primary alcohols), as well as liquid phase oxidation and reduction reactions. It turns out that the bonding and activation of molecular oxygen for gas phase oxidations strongly profits from trace amounts of an ad-metal residue such as silver. It is noteworthy that these catalysts still exhibit the special gold type chemistry, characterized by activity at very low temperatures and high selectivity for partial oxidations. For example, we can oxidize CO over these unsupported catalysts (npAu, nanotubes, and powder) at temperatures well below water's freezing point (-30 °C) and with turnover frequencies up to 0.5 s(-1) (at 30 °C). Yet, we can anticipate the surface chemistry of these unsupported and extended gold surfaces based on model experiments under UHV conditions. We have demonstrated this for the selective oxidation of primary alcohols at low temperatures employing npAu catalysts. Chemists have paid growing interest to oxidation and reduction reactions in liquid phase catalysis, most suitable for synthetic organic chemistry. Early work on the aerobic oxidation of d-glucose in 2008 using Raney type npAu already showed the potential of this type of catalyst for liquid phase reactions. Since then, researchers have investigated further oxidation reactions (silanes to silanols) and reduction reactions of alkynes, as well as C-C coupling reactions ([4 + 2] benzannulation) and azo compound decomposition, with likely several more reactions to be reported in the next years. The advantage of this unsupported skeletal type of catalyst is its recyclability and retrievability without leaching of gold into the reaction medium, owing to its monolithic structure. Even though these materials contain nanoscopic structures, they are macroscopic in their geometric dimensions and pose no threat to the environment or health as discussed for other nanomaterials.

Sunflower oil to green diesel over Raney-type Ni-catalyst

There are intensive efforts for reforming triglycerides to fuels. A non-pyrophoric Raney nickel type catalyst was investigated in the hydroconversion of sunflower oil. The catalyst was also tested in the transformation of octanoic acid as a model compound at 21bar in temperature range of 280–340°C. It was found that alumina supported Ni catalysts (one of them is non-pyrophoric Raney type Ni) selectively catalyze the hydrodecarbonylation and decarboxylation of fatty acids being corrosive intermediates of trigliceride deoxygenation process. Beside the main hydrodecarbonylation reaction Ni-containing catalysts are active in disadvantageous side reactions such as CO methanization and hydrogenolysis of paraffins producing methane byproduct in high concentration with extensive hydrogen consumption. Non-pyrophoric Raney nickel catalyst is more active than Ni/Al2O3 samples especially in the side reactions. To eliminate the active sites responsible for the side reactions the catalyst was modified with tin and lead. It turned out that poisoning either with Sn or Pb did not improve selectivity. Finally addition of In2O3 proved to be effective by directing the transformation to a different deoxygenating reaction pathway resulting in high alcohol yields.

Highly selective hydrogenation of C[dbnd]C double bond in unsaturated carbonyl compounds over NiC catalyst

Carbon was deposited over Raney type skeletal nickel catalysts by decomposing methane under controlled way; thereby pyrophoricity of Raney nickel was removed and non-pyrophoric nickel-carbon composite materials (NiC catalysts) were synthesised. XPS and XRD characterizations revealed that the catalysts consisted of nickel in metallic form with superficial oxide layers, carbon and aluminium oxide/hydroxide. The NiC catalysts were observed to be highly selective in hydrogenating CC double bond in unsaturated carbonyl compounds leaving the carbonyl group almost untouched. Crotonaldehyde and isophorone were used as model substrates.

Raney and Catalan

Raney’s lemma is often used in a counting argument to prove the formula for (generalized) Catalan numbers. It ensures the existence of “good” cyclic shifts of certain sequences, i.e. cyclic shifts for which all partial sums are positive. We introduce a simple algorithm that finds these cyclic shifts and also those with a slightly weaker property. Moreover it provides simple proofs of lemma’s of Raney type. A similar clustering procedure is also used in a simple proof of a theorem on probabilities of which many well-known results (e.g. on lattice paths and on generalized Catalan numbers) can be derived as corollaries. The theorem generalizes generalized Catalan numbers. In the end it turns out to be equivalent to a formula of Raney.

Zinc–nickel alloy electrodeposits for water electrolysis

Electrodeposited zinc–nickel alloys of various compositions were prepared. A suitable electrolyte and conditions to produce alloys of various compositions were identified. Alloys produced on electroformed nickel foils were etched in caustic to leach out zinc and to produce the Raney type, porous electro catalytic surface for hydrogen evolution. The electrodes were examined by polarization measurements, to evaluate their Tafel parameters, cyclic voltammetry, to test the change in surface properties on repeated cycling, scanning electron microscopy to identify their microstructure and X-ray diffraction. The catalytic activity as well as the life of the electrode produced from 50% zinc alloy was found to be better than others.

Preparation of iron–nickel catalysts by mechanical alloying

Raney type catalysts were prepared by means of a two-step procedure: (i) mechanical alloying (MA) of the metals and (ii) alkaline aluminum leaching. MA is a novel alternative related to the synthesis of skeletal Ni catalysts. Catalyst characterization was performed by atomic absorption (AA), X-ray diffraction (XRD), and Mössbauer spectroscopy (MS). Textural studies were also carried out. Binary Al–Ni and ternary Al–Ni–Fe alloys were produced by MA from pure metallic powders; in particular, the intermetallic β-(AlNi) phase was formed with a fine microstructure as a non-equilibrium phase; then, aluminum was selectively removed. After aluminum leaching, the β-(AlNi) phase was transformed into the more stable nickel fcc structure.

Raney Type Surfaces Prepared by High Energy Ball Milling: Application to the Synthesis of Electroanalysts for the Sodium Chlorate Industry

Raney Type Surfaces Prepared by High Energy Ball Milling: Application to the Synthesis of Electroanalysts for the Sodium Chlorate Industry

Raney Type Surfaces Prepared by High Energy Ball Milling: Application to the Synthesis of Electroanalysts for the Sodium Chlorate Industry

Raney Type Surfaces Prepared by High Energy Ball Milling: Application to the Synthesis of Electroanalysts for the Sodium Chlorate Industry

Progress in design of new amorphous alloy catalysts

Three new kinds of Ni-based amorphous alloy catalysts, Raney type Ni–P(R–Ni–P), Ni–Co–B, and Ni–B(P)/SiO 2, have been prepared by modification of either the rapid quenching method or chemical reduction. Their amorphous structures have been determined by XRD, EXAFS, and DSC. Their catalytic activities and selectivities have been measured during the hydrogenation of various organic compounds, which demonstrate the great improvement on the catalytic properties in comparison with the corresponding amorphous alloy catalysts prepared by the rapid quenching method or chemical reduction previously reported. These new amorphous catalysts also exhibit superior catalytic properties over the traditional catalysts, such as Raney Ni, Ni/SiO 2, and Pd/C, making them possible to be used in real industrial catalysis. The relationship between the catalytic properties and the structural properties has been discussed according to various characterizations, including ICP, XPS, EXAFS, XRD, TPD, TPR, hydrogen adsorption, IR, SEM, and TEM, etc. The higher hydrogenation activity of R–Ni–P than the Ni–P amorphous catalyst obtained by rapid quenching is mainly ascribed to the increase of the surface area due to the skeleton structure; the higher activity of Ni–Co–B than the Ni–B amorphous catalyst demonstrates a promoting effect of the additive metal(s); while the higher thermal stability of supported Ni–P(B) than the corresponding unsupported catalysts can be explained by considering the stabilizing effect of the silica support on the amorphous structure.

Raney type copper-zinc-aluminium catalyst for water-gas shift reaction

The structure and the catalytic activity in the water-gas shift (WGS ) reaction of a Raney type copper-zinc-alummium catalyst has been studied. It has been established that after leaching of the alloy with alkali solution copper particles are formed, covered by a hydroxycarbonate film containing mainly a hydrotalcite like phase. Most probably this system is the precursor of the active sites, similar to the WGS catalysts obtained by coprecipitation. The Raney type catalysts manifested catalytic activity by an order of magnitude higher than that of the conventional coprecipitated catalysts. This could be explained by the formation of a complex catalytic system, containing a “polyelectrode” of a redox galvanic couple of copper ions, closed via the metal phase.

Activation of Dinitrogen over Various Raney Type Metal Catalysts

Abstract Raney Ni, Rh, Re, and Ir adsorbed molecular nitrogen which was stable up to about 300 K. Raney Fe, Co, Ni, Ru, Rh, Ir, and Pt adsorbed atomic nitrogen which was desorbed around 700 or 800 K. The XPS spectra of atomically adsorbed nitrogen was observed on Co, Ni, and Ru samples. While the per-weight activity of Raney Ru for isotopic equilibration of N2 is much higher than that of 5% Ru–K/AC, those of other Raney metals are lower than those of 5% metal–K/AC.

微小粒子からなる板状Ｒａｎｅｙ銅触媒の活性と構造

A Raney type copper catalyst was prepared from a layer of Cu-Al alloy produced along the boundary of a copper plate and aluminum plates by hot-rolling. The fine particle catalyst of.0.03-0.09 pm diameter with the specific surface area of 317 BET m2/m2 attained the rate of 10.0 mol/h·m2 for 2-propanol dehydrogenation at 300°C, whereas a cleaned copper plate catalyst gave only 0.5 mol/h·m2. The catalyst structure and activity were changed by sintering and oxidation-reduction pretreatments (Table 1), which was compared with the thermogravity change for the representative catalysts (Fig.4).

Fibrous hydrogenation catalysts derived from NiAl eutectic alloys

The directional solidification (DS) of eutectic Ni-Al alloys was investigated as a new route for the synthesis of catalytic materials of the Raney (trade-mark) type with improved properties. Critical surface properties of the caustic-activated alloys, such as specific surface area, pore structure and available catalytic nickel surface area for active nickel derived from DS precursor alloys, were found to be superior to those of commercial bulk-cast Raney alloys activated in the same manner. Microporosites derived from low temperature nitrogen adsorption isotherms on caustic-activated alloys are significantly greater and pore distributions occur not only in both the small pore sizes with radii of less than about 10 Å and the sizes with radii of about 40–70 Å, which typical of Raney nickles, but also in the coarse pore sizes, with radii of about 90 Å, which are not typical of commercial activated Raney nickels. The enhanced pore structure of these DS caustic-activated alloys was demonstrated to be quite stable toward sintering by air oxidation at temperatures of about 500 °C. The Brunauer-Emmett-Teller surface area and available nickel metal surface area were found also to provide promising stability toward sintering in hot (about 350 °C) reducing atmospheres typical for methanation catalysis. The catalytic performance of caustic-activated DS Ni-Al eutectic alloys, compared with commercial Raney alloys, was found to be consistently superior by factors of 1.14–12.9 for initial reaction rates at low temperature (22 and 80 °C) for six selected liquid phase hydrogenation reactions, i.e. hydrogenation of acetone to isopropanol, nitrobenzene to aniline, toluene to methyl cyclohexane, butyronitrile to butylamine, itaconic acid to methyl succinic acid and dextrose to sorbitol. This superiority was due principally to the greater available catalytic nickel surface but in two instances (butyronitrile and nitrobenzene) the hydrogenation rates on a specific area basis are superior by factors of about 7 and 3 respectively, indicating that selectivity also plays a role.

Stationary catalysts for the continuous hydrogenation of fats

AbstractHydrogenation characteristics of a wide variety of stationary catalysts were studied with an aim to explore their possible use in the continuous hydrogenation of fats. Refined soybean oil was hydrogenated continuously in a vertical flow‐through reactor over a fixed bed of catalyst. Catalysts investigated were pelleted products containing Raney nickel, reduced nickel, reduced palladium, and copper chromite, as well as granulated alloys of the Raney type, such as Ni‐Al, Cu‐Al, Pd‐Al, and Cu‐Cr‐Al, which were activated with alkali. These catalysts offered a wide choice of activity, selectivity, and ability to form geometrical isomers. Pelleted copper chromite and granular Raney copper‐chromium were found to be highly selective toward the linolenate moiety of soybean oil, whereas pelleted palladium on carrier, as well as granular Raney nickel, Raney copper, and Raney palladium, though moderately selective, exhibited very high activity even at relatively low temperatures. A unique feature of most of the stationary catalysts was the remarkably high rate of hydrogenation. With most catalysts, the iodine value of soybean oil was reduced by 40–60 units within a reaction period of 2–4 min. The hydrogenated fat was practically free of catalyst particles.