The electrocatalytic hydrogenation of fused poly cyclic aromatic compounds at Raney nickel electrodes: the influence of catalyst activation and electrolysis conditions

1990 ◽  
Vol 68 (7) ◽  
pp. 1218-1227 ◽  
Author(s):  
Denis Robin ◽  
Michel Comtois ◽  
Anna Martel ◽  
René Lemieux ◽  
Amoy Kam Cheong ◽  
...  
Keyword(s):  
Raney Nickel ◽  
Supporting Electrolyte ◽  
Aqueous Sodium Hydroxide ◽  
Constant Current ◽  
Electrocatalytic Hydrogenation ◽  
Catalyst Activation ◽  
Nickel Electrodes ◽  
Initial Ph ◽  
Raney Ni ◽  
Tetrabutylammonium Chloride

The electrocatalytic hydrogenation (ECH) of phenanthrene, anthracene, and naphthalene has been investigated under constant current at Raney nickel electrodes in a mixed aqueous organic medium. The influence of various parameters on the efficiency of the process determined by the current efficiency (a measure of the competition between hydrogenation and hydrogen evolution, the only two electrochemical processes occurring), the extent of hydrogenation (yield of octahydro-derivatives), and the conversion rate was studied with phenanthrene. The best conditions were ethylene glycol or propylene glycol as cosolvent containing between 1.5 to 5% of water, a neutral or slightly acidic medium containing boric acid (0.1 M) as buffer (initial pH of 2.6, final pH of 6.0–6.2), sodium chloride or tetrabutylammonium chloride as supporting electrolyte, a temperature of 80° C, and a current density of 42 to 84 mA/cm2. The most active electrodes (consisting of Raney Ni particles dispersed in a nickel matrix and surrounded by a layer of porous nickel) were obtained by leaching the dispersed alloy particles at 75 °C for 7 h in 30% aqueous sodium hydroxide. The electrohydrogenation stopped at derivatives with a single aromatic ring, namely the octahydrophenanthrenes, octahydroanthracenes, and tetralin. In a non-buffered medium, tetrahydrophenanthrene could be obtained with selectivities of 80% or better. Keywords: electrocatalytic hydrogenation, Raney nickel electrodes, phenanthrene, anthracene, naphthalene.

Electrocatalytic hydrogenation of lignin models at Raney nickel and palladium-based electrodes

2000 ◽  
Vol 78 (3) ◽  
pp. 307-315 ◽  
Author(s):  
André Cyr ◽  
Florence Chiltz ◽  
Paul Jeanson ◽  
Anna Martel ◽  
Louis Brossard ◽  
...  
Keyword(s):  
Raney Nickel ◽  
Sodium Hydroxide Solution ◽  
Aqueous Sodium Hydroxide ◽  
Reaction Scheme ◽  
Constant Current ◽  
Electrocatalytic Hydrogenation ◽  
Hydroxymethyl Group ◽  
Lignin Model ◽  
Aryl Ethers ◽  
Methylene Group

The electrocatalytic hydrogenation (ECH) of β-O-4 lignin model compounds has been carried out at constant current at Raney nickel and palladium-based cathodes in aqueous sodium hydroxide solution at temperatures ranging from 25 to 75°C. It was found that the hydrogenolysis of phenolic β-arylethyl-aryl ethers with one β-O-4 linkage takes place at both types of electrodes to give a mixture of phenolic compounds. The ECH of 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-ethanol (model 1) at Raney nickel gives guaiacol (9), acetovanillone (11b), alpha-methylvanillyl alcohol (12b), and products derived from their further hydrogenation. The β-O-4 bond is more difficult to cleave upon replacing one hydrogen of the methylene group of 1 by a hydroxymethyl group (see 2). However, model 4 with two β-O-4 linkages obtained by the introduction of an α-methylvanillyl group at the phenolic position of 1 is hydrogenolysed at the same rate as 1 at Raney nickel. Only the C-O aryl bond attached to the hydroxyethylphenol moiety is cleaved. At palladium, the hydrogenolysis of 1 requires only half of the theoretical amount of electricity due to the generation of chemisorbed hydrogen by dehydrogenation of 1 followed by hydrogenolysis of the resulting ketone. A general reaction scheme is proposed for the ECH of model 1.Key words: Lignins, lignin models, electrocatalytic hydrogenation, Raney nickel electrodes, palladium electrodes.

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.

The electrocatalytic hydrogenation of phenanthrene at Raney nickel electrodes: the influence of an inert gas pressure

1998 ◽  
Vol 43 (12-13) ◽  
pp. 1697-1703 ◽  
Author(s):  
Richard Menini ◽  
Anna Martel ◽  
Hugues Me ́nard ◽  
Jean Lessard ◽  
Olivier Vittori
Keyword(s):  
Raney Nickel ◽  
Gas Pressure ◽  
Inert Gas ◽  
Electrocatalytic Hydrogenation ◽  
Nickel Electrodes

The electrocatalytic hydrogenation of phenanthrene at modified Raney nickel electrodes

1996 ◽  
Vol 93 ◽  
pp. 1252-1261
Author(s):  
JM Chapuzet ◽  
B Mahdavi ◽  
J Lessard
Keyword(s):  
Raney Nickel ◽  
Electrocatalytic Hydrogenation ◽  
Nickel Electrodes

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.

Photo-assisted electrochemical degradation of real textile wastewater

2010 ◽  
Vol 61 (2) ◽  
pp. 491-498 ◽  
Author(s):  
P. A. Alves ◽  
G. R. P. Malpass ◽  
H. D. Johansen ◽  
E. B. Azevedo ◽  
L. M. Gomes ◽  
...  
Keyword(s):  
Supporting Electrolyte ◽  
Oxygen Demand ◽  
Textile Wastewater ◽  
Operating Conditions ◽  
Cod Removal ◽  
Constant Current ◽  
Electrochemical Degradation ◽  
Figures Of Merit ◽  
Before And After ◽  
Initial Ph

In the present study, photo-assisted electrochemical degradation of real textile wastewater was performed. Degradation assays were performed at constant current (40 mA cm−2) in a combined electro/photochemical flow-cell using a Ti/Ru0.3Ti0.7O2 DSA® type electrode. The results show that the method is capable of removing color and chemical oxygen demand (COD) from the effluent. Additionally, the effect of initial pH and type of supporting electrolyte (Na2SO4 or NaCl) was investigated. The principal figures of merit used in this study were COD removal and color removal (605 nm). The results show that up to 72% color and up to 59% COD removal in 120 min is possible under the operating conditions employed. Studies of the phytotoxicity of the wastewater before and after the photo-assisted degradation assays are also presented and the results demonstrate that the toxicity of the effluent is dependent on the length of electrolysis time and the treatment procedure employed.

The influence of surfactants on the electrocatalytic hydrogenation of organic compounds in micellar, emulsified, and hydroorganic solutions at Raney nickel electrodes

1995 ◽  
Vol 73 (6) ◽  
pp. 804-815 ◽  
Author(s):  
Philippe Chambrion ◽  
Laurence Roger ◽  
Jean Lessard ◽  
Valérie Béraud ◽  
Josée Mailhot ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Raney Nickel ◽  
Conversion Rate ◽  
Surfactant Concentration ◽  
Main Product ◽  
Micellar Medium ◽  
Micellar Solutions ◽  
Electrocatalytic Hydrogenation ◽  
Brij 35 ◽  
Nickel Electrodes

The electrocatalytic hydrogenation (ECH) of limonene (1) and carvone (4) at a Raney nickel cathode was studied both in hydroorganic medium (methanol–water) and aqueous micellar and emulsified solutions. In methanol–water, the ECH of 1 stopped at p-menthene (2) and proceeded with low current efficiencies (18–24%). In micellar solutions containing a cationic surfactant (CTAB), the ECH of 1 was more efficient, giving p-menthane (3) as the main product with current efficiencies up to 30%. The pH of the solution (hydroorganic and micellar) had little influence. With anionic (SDS) and nonionic (Brij 35) surfactants, some p-menthane (3) was formed but the conversion rate and current efficiency were much lower. The ECH of carvone (4) was slightly less efficient in methanol–water than in micellar and emulsified solutions. The saturated alcohols neocarvomenthol (8), carvomenthol (9), isocarvomenthol (10), and neoisocarvomenthol (11) were the main products with current efficiencies of 75% (hydroorganic medium) to 90% (micellar solutions). The effect of surfactant concentration and pH on the efficiency and stereochemistry of the ECH of carvone (4) was also studied. Keywords: electrocatalytic hydrogenation, limonene, carvone, Raney nickel, micellar medium.

The influence of a non-micelle-forming surfactant on the electrocatalytic hydrogenation of carvone and limonene in aqueous medium at Raney nickel electrodes

1997 ◽  
Vol 75 (11) ◽  
pp. 1529-1535 ◽  
Author(s):  
Valérie Beraud ◽  
Marc Thomalla ◽  
Jean Lessard
Keyword(s):  
Raney Nickel ◽  
Major Part ◽  
Basic Medium ◽  
Organic Layer ◽  
Electrocatalytic Hydrogenation ◽  
Medium Ph ◽  
Interfacial Film ◽  
Didodecyldimethylammonium Bromide ◽  
Strong Adsorption ◽  
Nickel Electrodes

The electrocatalytic hydrogenation (ECH) of carvone (1) and limonene (8) at a Raney nickel cathode was studied in aqueous solutions containing a non-micelle-forming surfactant (didodecyldimethylammonium bromide, DDAB). The efficiency of ECH of these substrates was markedly increased compared to that observed previously with micelle-forming surfactants, and this for very low DDAB concentrations, as a consequence of the strong adsorption of DDAB on the electrode. For the ECH of 8 in basic medium (pH 10), the major part of organic compounds (60–95%) was shown to be adsorbed on the electrode surface as an organic layer stabilized by an interfacial film of DDAB. Keywords: electrocatalytic hydrogenation, limonene, carvone, surfactant, emulsions, Raney nickel cathodes.

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