Article

1999 ◽  
Vol 77 (7) ◽  
pp. 1225-1229 ◽  
Author(s):  
Pierre Dabo ◽  
André Cyr ◽  
Jean Lessard ◽  
Louis Brossard ◽  
Hugues Ménard
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Raney Nickel ◽  
Activated Charcoal ◽  
Vitreous Carbon ◽  
Electrocatalytic Hydrogenation ◽  
Reticulated Vitreous Carbon ◽  
Nickel Boride

Electrodes consisting of particles of a transition metal entrapped and dispersed in a reticulated vitreous carbon (RVC) matrix were prepared in situ by stirring the particles in the presence of an RVC cathode. Such electrodes were used for the electrocatalytic hydrogenolysis (ECHsis) of 4-phenoxyphenol, a compound representative of the 4-O-5 type linkage in lignins. The electrolyses were carried out under galvanostatic control in aqueous 1 M NaOH. Raney nickel, nickel boride, and transition metals supported on activated charcoal or alumina were used as catalytic powders. The extent and efficiency of the ECHsis of 4-phenoxyphenol was found to depend on the catalyst and on the temperature.Key words: electrocatalytic hydrogenation, electrocatalytic hydrogenolysis, 4-phenoxyphenol, Raney nickel, palladium on charcoal, palladium on alumina.

Considerations about phenol electrohydrogenation on electrodes made with reticulated vitreous carbon cathode

2003 ◽  
Vol 81 (3) ◽  
pp. 258-264 ◽  
Author(s):  
François Laplante ◽  
Louis Brossard ◽  
Hugues Ménard
Keyword(s):  
Physical Vapor Deposition ◽  
Detrimental Effect ◽  
Aqueous Media ◽  
Vitreous Carbon ◽  
Electrocatalytic Hydrogenation ◽  
Reticulated Vitreous Carbon ◽  
Composite Powders ◽  
Agglomeration Process ◽  
Adsorption Of Organic Molecules

The electrocatalytic hydrogenation (ECH) of phenol was carried out in aqueous media with catalytic powders. The catalytic powders were composed of palladium nanoaggregates deposited on various substrates such as Al2O3, BaSO4, and BaCO3. Composite powders are trapped (upon stirring) into a reticulated vitreous carbon (RVC) matrix, allowing a rapid in situ build-up of the electrode and alleviating the use of a binder, since the latter may have a detrimental effect on the ECH. For a given amount of noble metal (5% palladium by weight), it is observed that the ECH of phenol to cyclohexanol increases in the following order: Pd/BaCO3 < Pd/BaSO4 < Pd/Al2O3. It is deduced that the ECH rate is largely dependent on the adsorption of organic molecules on the nonmetallic substrate, and a model is considered to explain such a behavior. The ECH of phenol is also feasible at a reasonable rate with composite Pd/Al2O3 (0.25% Pd by weight) powders fabricated by physical vapor deposition because the peripheral distribution of Pd nanoaggregates is favorable towards the ECH.Key words: electrocatalytic hydrogenation (ECH) of phenol, reticulated vitreous carbon (RVC), alumina-based catalyst, agglomeration process, adlineation point, adsorption.

scholarly journals Mimicking Transition Metals in Borrowing Hydrogen from Alcohol

2021 ◽  
Author(s):  
Swadhin K Mandal ◽  
Ananya Banik ◽  
Jasimuddin Ahmed ◽  
Swagata Sil
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Borrowing Hydrogen

Borrowing hydrogen from alcohol, storing it on the catalyst and subsequent transfer of the hydrogen from catalyst to an in situ generated imine is the hallmark of a transition metal...

Electrocatalytic hydrogenation of conjugated enones on nickel boride, nickel, and Raney nickel electrodes

1995 ◽  
Vol 73 (6) ◽  
pp. 846-852 ◽  
Author(s):  
Behzad Mahdavi ◽  
Philippe Chambrion ◽  
Julie Binette ◽  
Eric Martel ◽  
Jean Lessard
Keyword(s):  
Double Bond ◽  
Raney Nickel ◽  
Carbonyl Compounds ◽  
Constant Current ◽  
Electrocatalytic Hydrogenation ◽  
Aqueous Methanol ◽  
Nickel Boride ◽  
Unsaturated Ketones ◽  
Nickel Electrodes ◽  
Bond Hydrogenation

The selectivity of the electrocatalytic hydrogenation (ECH) of conjugated enones to the corresponding carbonyl compounds has been investigated in aqueous methanol under constant current at nickel boride, fractal nickel, and Raney nickel electrodes made of pressed powders. The influence of various parameters (water percentage, pH, concentration of substrate, and current density) on the selectivity of the carbon–carbon double bond hydrogenation was studied with cyclohex-2-en-1-one at nickel boride electrodes. Under given electrolysis conditions, fractal nickel electrodes were found to give the highest selectivity. The selectivity of the ECH of a variety of conjugated enones at fractal nickel electrodes was determined under electrolysis conditions that gave the best selectivity with cyclohexenone at nickel boride electrodes. Keywords: electrocatalytic hydrogenation, α,β-unsaturated ketones, selective hydrogenation, nickel based cathodes.

A comparison of nickel boride and Raney nickel electrode activity in the electrocatalytic Hydrogenation of Phenanthrene

1994 ◽  
Vol 72 (11) ◽  
pp. 2268-2277 ◽  
Author(s):  
Behzad Mahdavi ◽  
Przemyslaw Los ◽  
Marie Josée Lessard ◽  
Jean Lessard.
Keyword(s):  
Raney Nickel ◽  
Electrocatalytic Activity ◽  
Surface Characterization ◽  
Mercury Porosimetry ◽  
Ac Impedance ◽  
Intrinsic Activity ◽  
Electrocatalytic Hydrogenation ◽  
Nickel Boride ◽  
Electrode Activity ◽  
Nickel Electrodes

The electrocatalytic activity of nickel boride in the electrocatalytic hydrogenation (ECH) of phenanthrene in ethylene glycol–water at 80 °C has been compared to that of Raney nickel and fractal nickel. The intrinsic activity of the electrode material (real electrode activity) is the same for nickel boride and Raney nickel electrodes and is lower for fractal nickel electrodes. The apparent electrode activity of nickel boride pressed powder electrodes (Ni2B electrodes) is less than that of codeposited Raney nickel (RaNi) electrodes and pressed powder fractal nickel/Raney nickel (Ni/RaNi = 50/50 to 0/100) electrodes. The apparent activity of Ni2B electrodes is improved by adding sodium chloride to the powder and dissolving it after pressing (Ni2B–NaCl electrodes). The Ni2B–NaCl electrodes have the same apparent activity as codeposited RaNi and pressed powder Ni/RaNi (20/80 to 0/100) electrodes. The apparent and real electrode activity of Ni/RaNi electrodes increases with the RaNi content up to a 20/80 ratio. The Tafel and alternating current (ac) impedance parameters were determined for the hydrogen evolution reaction (HER) in 1 M aqueous sodium hydroxide at 25 °C at nickel boride and at codeposited RaNi electrodes. The intrinsic electrocatalytic activity for HER, expressed by the ratio of the exchange current density over the roughness factor (I0/R), is similar for Ni2B, Ni2–NaCl, and codeposited RaNi electrodes. Surface characterization of Ni2B and Ni2B–NaCl electrodes was carried out by BET, ac impedance, scanning electron microscopy, and mercury porosimetry. No direct relation between the apparent electrode activity in ECH and the surface measured by BET and ac impedance was found. The ac impedance measurements were also carried out in the presence of sodium trans-cinnamate.

Experimental and computational investigation of the electrocatalytic hydrogenation of phenol in an electrochemical cell

2004 ◽  
Vol 82 (5) ◽  
pp. 641-648 ◽  
Author(s):  
A Chagnes ◽  
F Laplante ◽  
F Kerdouss ◽  
P Proulx ◽  
H Ménard
Keyword(s):  
Fluidized Bed ◽  
Cathodic Polarization ◽  
Volume Fraction ◽  
Fluid Dynamic ◽  
Aqueous Media ◽  
Vitreous Carbon ◽  
High Porosity ◽  
Electrocatalytic Hydrogenation ◽  
Reticulated Vitreous Carbon ◽  
Fluidized Bed Electrode

The electrocatalytic hydrogenation (ECH) of phenol was carried out in aqueous media with a commercial Pd/Al2O3 (5% w/w) catalyst. A porous matrix of reticulated vitreous carbon (RVC) was used to study the porosity – stirring speed coupling (PSSC) effect on the phenol hydrogenation to form cyclohexanone and cyclohexanol. In accordance with the PSSC, the electrode can act as a fluidized bed electrode or as an agglomerated electrode. Fluidized bed electrodes develop for low porosity matrices (10–30 ppi, ppi = pores per inch) at high stirring speeds (>600 rpm), while agglomerated electrodes are obtained for high porosity matrices (60–100 ppi) with moderate stirring speeds under cathodic polarization. The distribution of the volume fraction of the particles and the agglomeration of the particles have been simulated by computational fluid dynamic (CFD) methods with FLUENT software. For the agglomerated electrode, the numerical simulations demonstrate the beneficial contribution of the cathodic polarization to the agglomeration process. However, at 650 rpm, for the fluidized bed electrode, the volume fraction of the particles in the RVC does not account for the distinction in the ECH efficiency between the 30 ppi matrix and the 100 ppi matrix. For a given amount of Pd/Al2O3 catalyst, it is observed that the ECH rates depend on the PSSC and increase in the following order: 100/650 < 30/650 < 100/200. Key words: electrocatalytic hydrogenation (ECH), CFD, fluid mechanics, porous media, powder, porosity – stirring speed coupling (PSSC), reticulated vitreous carbon (RVC).

Cyanomethylation of alkenes with C–H bond activation of acetonitrile: in situ generated diazonium salts as promoters without transition-metals

RSC Advances ◽  
2016 ◽  
Vol 6 (1) ◽  
pp. 522-526 ◽  
Author(s):  
Zhangqin Ni ◽  
Xin Huang ◽  
Jichao Wang ◽  
Yuanjiang Pan
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Bond Activation ◽  
Diazonium Salts

In situ generated diazonium salts were used as radical promoters for the Csp3–H functionalization of acetonitrile without photocatalyst or transition-metal.

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