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.

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.

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).

Electrocatalytic hydrogenation of catechol on Rh–Al2O3 in different media — pH-Dependent reduction mechanism for intermediate formation

2006 ◽  
Vol 84 (12) ◽  
pp. 1640-1647 ◽  
Author(s):  
Anne Brisach-Wittmeyer ◽  
Nicolas-Alexandre Bouchard ◽  
Raymond Breault ◽  
Hugues Ménard
Keyword(s):  
Cyclic Voltammetry ◽  
Uv Spectroscopy ◽  
Aqueous Media ◽  
Intermediate Formation ◽  
Vitreous Carbon ◽  
Reduction Mechanism ◽  
Electrocatalytic Hydrogenation ◽  
Vis Spectroscopy ◽  
Ph Dependent ◽  
Henry Constants

The electrocatalytic hydrogenation of catechol was carried out in aqueous media in different pH ranges with Rh–Al2O3 powder catalyst. The reactions were conducted in an H-cell used as a dynamic cell, with a reticulated vitreous carbon electrode in contact with the catalyst powder as the working electrode. It was shown that the final product is 1,2-cyclohexanediol (cis and trans isomers) and that several intermediates are detected depending on the pH of the solution. Different media, from pH 5 to 13, were studied. One of the intermediates is 1,2-cyclohexanedione, detected at all pH values. The other is 2-hydroxycyclohexan-1-one, only observed at pH ≤ 7. To determine the mechanism of the reactions involved, the electrocatalytic hydrogenation of these intermediates to form the final 1,2-cyclohexanediol product was also conducted, and their UV spectroscopy and cyclic voltammetry data recorded. The influence of the nature of the solution was screened by measuring the Henry constant of each molecule.Key words: electrocatalytic hydrogenation of catechol, pH-dependent reduction mechanism, UV–vis spectroscopy, cyclic voltammetry, Henry constants.

scholarly journals Recent advances on modified reticulated vitreous carbon for water and wastewater treatment – A mini-review

Chemosphere ◽  
2021 ◽  
pp. 131573
Author(s):  
Vanessa M. Vasconcelos ◽  
Géssica O.S. Santos ◽  
Katlin I.B. Eguiluz ◽  
Giancarlo R. Salazar-Banda ◽  
Iara de Fatima Gimenez
Keyword(s):  
Wastewater Treatment ◽  
Vitreous Carbon ◽  
Reticulated Vitreous Carbon ◽  
Water And Wastewater Treatment ◽  
Recent Advances ◽  
Water And Wastewater

Roughened gold electrode for in situ SERS analysis of structural changes accompanying the doping process of polyaniline in acidic aqueous media

2021 ◽  
Vol 882 ◽  
pp. 115034
Author(s):  
A. El Guerraf ◽  
M. Bouabdallaoui ◽  
Z. Aouzal ◽  
S. Ben Jadi ◽  
N.K. Bakirhan ◽  
...  
Keyword(s):  
Gold Electrode ◽  
Structural Changes ◽  
Aqueous Media

scholarly journals Poly(N-isopropylacrylamide-co-methacrylic acid) microgel stabilized copper nanoparticles for catalytic reduction of nitrobenzene

2015 ◽  
Vol 33 (3) ◽  
pp. 627-634 ◽  
Author(s):  
Zahoor H. Farooqi ◽  
Zonarah Butt ◽  
Robina Begum ◽  
Shanza Rhauf Khan ◽  
Ahsan Sharif ◽  
...  
Keyword(s):  
Copper Nanoparticles ◽  
Methacrylic Acid ◽  
Catalytic Reduction ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Reducing Agent ◽  
Different Temperatures ◽  
Entropy Of Activation ◽  
Micro Reactors

Abstract Poly(N-isopropylacrylamide-co-methacrylic acid) microgels [p(NIPAM-co-MAAc)] were synthesized by precipitation polymerization of N-isopropylacrylamide and methacrylic acid in aqueous medium. These microgels were characterized by dynamic light scattering and Fourier transform infrared spectroscopy. These microgels were used as micro-reactors for in situ synthesis of copper nanoparticles using sodium borohydride (NaBH4) as reducing agent. The hybrid microgels were used as catalysts for the reduction of nitrobenzene in aqueous media. The reaction was performed with different concentrations of cat­alyst and reducing agent. A linear relationship was found between apparent rate constant (kapp) and amount of catalyst. When the amount of catalyst was increased from 0.13 to 0.76 mg/mL then kapp was increased from 0.03 to 0.14 min-1. Activation parameters were also determined by performing reaction at two different temperatures. The catalytic process has been discussed in terms of energy of activation, enthalpy of activation and entropy of activation. The synthesized particles were found to be stable even after 14 weeks and showed catalytic activity for the reduction of nitrobenzene.

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