Presence Of Nickel Catalyst Research Articles

Nickel-Catalyzed Addition of Alkynylboranes to Alkynes

Alkynylboration has been achieved in the reaction of alkynyl(pinacol)boranes with alkynes in the presence of nickel catalysts, giving cis-1-borylbut-1-en-3-yne derivatives. 1-Aryl-1-alkynes underwent the alkynylboration regioselectively with the selective introduction of the alkynyl groups at their 1-positions, where the aryl groups were attached. The boryl-substituted enynes were reacted with sp2 halides under the Suzuki−Miyaura coupling conditions, giving highly conjugated enynes in high yields.

Nickel-Catalyzed Addition of Alkynylboranes to Alkynes

Alkynylboration has been achieved in the reaction of alkynyl(pinacol)boranes with alkynes in the presence of nickel catalysts, giving cis-1-borylbut-1-en-3-yne derivatives. 1-Aryl-1-alkynes underwent the alkynylboration regioselectively with the selective introduction of the alkynyl groups at their 1-positions, where the aryl groups were attached. The boryl-substituted enynes were reacted with sp2 halides under the Suzuki-Miyaura coupling conditions, giving highly conjugated enynes in high yields.

Effect of methanol, ethanol, and formaldehyde addition on the steam conversion of methane in the presence of nickel catalysts of various porous structure

The effect of CH2O, CH3OH, and C2H5OH on the methane conversion and the CO, CO2, and coke yield in the methane steam conversion on commercial nickel catalysts for steam reforming C 11-9-09 (12.8 wt % Ni/α-Al2O3) and hydrogenation (54.0 wt % Ni/kieselguhr) was studied at a temperature of 750°C and an H2O:CH4 ratio of 1.5–2.0. The action of these compounds was studied both individually and for their joint presence in the methane-steam mixture. Their effect on the reaction depends on the pore structure of the catalyst. Using the catalyst C 11-9-09 as an example, it was found that the introduction of formaldehyde into steam suppressed the methane conversion into Cs and high-boiling-point carbon compounds and gave the desired products with a yield close to the equilibrium value. When all three additives were present in the steam, ethanol was responsible for the formation of Cs.

Preparation and Reaction of 2‐Aryl‐3‐silyl‐1,3‐butadiene.

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.

Preparation and Reaction of 2-Aryl-3-silyl-1,3-butadiene

[reaction: see text] A conjugated pi-electron compound, 2-aryl-3-silyl-1,3-butadiene, was easily prepared from 1-benzyloxy-3-silyl-2-propyne, bis(iodozincio)methane, and an aryl halide in the presence of nickel catalyst. A subsequent cross-coupling reaction of the product with another aryl halide gave an unsymmetrical 2,3-diaryl-1,3-butadiene efficiently.

Fabrication of recyclable catalyst supports for synthesis of carbon nanofibers

Carbon nanofiber (CNF) has been synthesized by thermal dissociation of ethylene gas in the presence of nickel catalyst. Catalyst particles of nickel were immobilized on the surface of sintered yttria-stabilized zirconia supports (YSZ support) via either direct sintering of composite compacts or chemical doping into presintered porous YSZ compacts. The effect of support microstructures on the CNF morphology was investigated. In addition, the feasibility of a recyclable support for economical synthesis of CNF was assessed.

Dissociation of vibrationally excited methane on Ni catalyst: Part 1. Application to methane steam reforming

This paper describes extensive experimental research on steam reforming of methane using barrier discharges with/without Ni/SiO 2 catalyst. Nickel catalyst clearly showed chemical activity at 400 °C in the presence of barrier discharge. Methane conversion largely exceeded over equilibrium conversion rate, whereas product selectivity tended to follow equilibrium composition at given temperature: energy cost and energy efficiency achieved 134 MJ/kg H 2 and 69%, respectively. Electric property was unchanged in the presence of nickel catalyst, but at least 400 °C must be maintained in order to derive synergistic effect between barrier discharge and Ni/SiO 2 catalyst. Methane activation mechanism is also discussed based on numerical simulation on streamer propagation in pure methane. Vibrationally excited methane is most abundant (1016 cm −3 at 300 K, 101.3 kPa) and long-lived (∼1 μs) radical species produced by electron impact, and those vibrational species seemed to improve dissociative chemisorption on nickel surface at low temperature, leading to remarkable process improvement.

Dissociation of vibrationally excited methane on Ni catalyst: Part 2. Process diagnostics by emission spectroscopy

Barrier discharge enhanced catalyst bed (BEC) reactor was developed for methane steam reforming. Synergistic effect between barrier discharge and Ni/SiO 2 catalyst was clearly observed when bed temperature exceeded 400 °C, energy cost and energy efficiency achieved 134 MJ/kg H 2 and 26%, respectively. This paper concentrates on two-temperature analysis of BEC reactor for better understanding of reaction mechanism. Catalyst bed temperature and plasma gas temperature were separately analyzed by emission spectroscopy of rotational band of CH(A 2Δ). Gas temperature distribution in packed-bed reactor was also estimated by using empirical correlations, and compared to spectroscopic data. Even though plasma gas temperature reached 400–500 °C, synergistic effect was not observed when catalyst bed temperature was below 400 °C. On the other hand, thermal reforming reaction was dominated over barrier discharges if the bed temperature exceeded 700 °C. As key radical species, reactivity of vibrationally excited methane is discussed based on vibrational temperature of CH(A 2Δ). Vibrational temperature was significantly increased in the presence of nickel catalyst, showing increased reactivity of vibrationally excited species.

Microstructures of PAN-ACF modified by catalytic benzene deposition

Benzene pyrolysis was successfully introduced to modify the pore size distributions (PSD) of polyacrylonitrile based activated carbon fibers (PAN-ACF) into a sharp distribution, at the presence of nickel catalyst. The microstructures of samples were studied by means of nitrogen adsorption, XRD, and SEM. The nitrogen isotherms were analyzed in detail using the routine BET method, α s plot, DR equation, Horvath–Kawazoe (HK) equation, and regularized density functional theory (DFT), by which the surface area, micropore volume, and PSD were obtained. The results showed that the pore size of PAN-ACF can be effectively narrowed by catalytic benzene deposition and the PSD showed a unimodal nature, exhibiting potential behavior as a molecular sieve. A fraction residue of catalyst located in the ultramicropores can be washed by acid, resulting in increased BET surface area and micropore volume, which can also be confirmed by XRD and SEM measurements.

Nickel-Catalyzed Silaboration of Small-Ring Vinylcycloalkanes: Regio- and Stereoselective (E)-Allylsilane Formation via C−C Bond Cleavage

Vinylcyclopropanes and vinylcyclobutanes undergo regio- and stereoselective reaction with silylborane in the presence of nickel catalysts, giving (ω-borylalkyl)-substituted (E)-allylsilanes via cleavage of the carbon−carbon σ-bond in the rings.

Nickel‐catalyzed electrochemical carboxylation of epoxides: mechanistic aspects

The electrochemical incorporation of carbon dioxide into epoxides catalyzed by nickel(II) complexes afforded cyclic carbonates in good yields under very mild conditions (p atm, room temperature). Mechanistic and electrochemical studies revealed the cooperative role of reduced nickel species in the activation of CO2 and the influence of magnesium ions as Lewis acids in the activation of the oxirane ring. Both the presence of nickel catalysts and Mg2+ ions were necessary for the electrocarboxylation of epoxides under mild conditions. Copyright © 2001 John Wiley & Sons, Ltd.

Nickel-catalyzed electrochemical carboxylation of epoxides: mechanistic aspects

The electrochemical incorporation of carbon dioxide into epoxides catalyzed by nickel(II) complexes afforded cyclic carbonates in good yields under very mild conditions (p atm, room temperature). Mechanistic and electrochemical studies revealed the cooperative role of reduced nickel species in the activation of CO2 and the influence of magnesium ions as Lewis acids in the activation of the oxirane ring. Both the presence of nickel catalysts and Mg2+ ions were necessary for the electrocarboxylation of epoxides under mild conditions. Copyright © 2001 John Wiley & Sons, Ltd.

Electrochemical behavior of carbon alloy C N prepared by CVD using a nickel catalyst

Carbon–nitrogen layered compounds, C14N to C62N have been synthesized by thermal decomposition of acetonitrile at 800–1100°C in the presence of nickel catalyst. The CxN samples prepared with nickel had higher crystallinity and less pyridine-type nitrogens existing at the edge of graphene layers than CxN prepared in the absence of nickel. With an increase in the deposition temperature of CxN , the cycleability for electrochemical intercalation–deintercalation of lithium ions was improved and the profile of the charge–discharge curve approached that of natural graphite powder due to an increase in the crystallinity and a decrease in the incorporated nitrogens. Surface oxidation of the CxN by nitric acid solutions gave rise to an increase in the surface oxygens and a slight decrease in nitrogens without any change of crystallinity. The surface modification improved the cycleability for lithium ion intercalation–deintercalation reaction.

Automated refractive index measurement of catalyst‐laden edible oils undergoing partial hydrogenation

AbstractA planar optical waveguide, excited by monochromatic light, becomes a sensor for measuring the refractive index (RI) of edible oils. RI is commonly used to determine iodine value (IV). This process sensor operates in the presence of nickel catalyst and diatomaceous earth (DE) powders. An on‐line refractometer system, incorporating this sensor, demonstrates an accuracy of ±0.0001 RI units (RIU). Resolution is 0.00001 RIU. The waveguide refractometer is based on a loss in light transmission due to a temperature‐induced matching of waveguide and oil RIs. An algorithm adjusts the RI to conform to the temperature and wavelength as specified in AOCS Method Cc 7–25 (Official Methods and Recommended Practices of the American Oil Chemists' Society, edited by D. Firestone, American Oil Chemists' Society, Champaign, 1989), the accepted procedure for RI measurement with an Abbé refractometer. The theory, construction and performance characteristics of a prototype waveguide refractometer are described. Samples of partially hydrogenated soybean oils (IV ranges=106–75) are first examined with the Abbé refractometer, then tested in the prototype waveguide refractometer. Catalyst and DE are subsequently added to each sample, and RI data are taken again with the waveguide refractometer. Results confirm the instrument's ±0.0001 RIU accuracy and its immunity to interference from catalyst and DE. Real‐time operation holds promise for automatic control, improved production efficiency, and better batch‐to‐batch consistency of the hydrogenation process.

ChemInform Abstract: Nickel‐Mediated Cycloaddition of Diynes with Carbon Dioxide to Bicyclic α‐Pyrones.

AbstractThe diynes (Ia), (Ic) ‐ (Ie), and (Ih) undergo cyclization with carbon dioxide in the presence of nickel catalysts, yielding the bicyclic α‐pyrones (II).

Stereoselective synthesis of 1,4-disubstituted 1,3-diene from aldehyde using organotitanium reagent

Organotitanium reagent generated from 1-t-butylthio-3-trimethylsilyl-1-propene condenses with aldehydes to give 1 -t-butylthio-(E,Z)-1,3-alkadienes in a single step via (E)-erythro-β-hydroxysilane in a highly regio- and stereoselective manner. 1,4-Dialkyl-1,3-diene is obtaind from the diene sulfide by cross coupling reaction with Grignard reagent in the presence of nickel catalyst. The utility of the method is illustrated by application to the synthesis of Spilanthol, a naturally occurring insecticide from Spilanthese olerancae in five steps.

A New Convenient Synthesis of α-Arylpropionic Acid Esters and α-Arylpropionitriles

Abstract Various types of α-arylpropionic acid esters were effectively obtained by the coupling reaction of aryl Grignard reagents and α-bromopropionic acid esters in the presence of nickel catalysts. α-Arylpropionitriles, precursors of α-arylpropionic acids, were also synthesized by the reaction of α-methanesulfonyloxypropionitrile and arylcopper reagents prepared from equimolar amount of arylmagnesium halides and copper(I) bromide.

Hydrogasification of bituminous and brown coals at 1273 K: Action of a nickel catalyst

Hydrogasification of a bituminous and a brown coal was carried out at 1273 K in the presence of nickel catalyst. The action of the catalyst during gasification was investigated using a scanning electron microscope. Contrary to what is found with steam gasification, most of the catalyst particles were spherical, due to the higher temperature. Some particles made pits and disappeared into the char matrix and others agglomerated with each other increasing the diameter of the particles significantly. Although the action of the catalyst on a brown coal was essentially similar to that on a bituminous coal, the catalyst was more homogeneously distributed over the char surface from the brown coal.

Continuous slurry hydrogenation of soybean oil with nickel catalysts

AbstractSoybean oil was hydrogenated continuously in the presence of nickel catalysts. The iodine value of the products was varied by changing the oil flow rate and temperature of the reaction. Sulfur‐promoted nickel catalyst increased the selectivity for linolenate hydrogenation, but formed much higher proportions oftrans isomers. Linoleate selectivity improved with temperature with both nickel and sulfur‐promoted nickel catalysts, buttrans isomerization also increased. The feasibility of this continuous reactor system was demonstrated as a practical means to prepare hydrogenated stocks of desired composition and physical characteristics at high throughput.

Reactions of methane with unsaturated hydrocarbons in the presence of nickel catalysts

Methane, when used to activated supported nickel catalysts, react at ca. 300 °C with benzene, cyclopentene, methylenecyclopentane, and simple alkenes to give modest but definite amounts of higher hydrocarbons.