Electrochemical determination of ferrocene diffusion coefficient in liquid media under high CO2 pressure: Application to DMF–CO2 mixtures

Electrochemical method can be useful for the determination of diffusion coefficients in various media. For low polarity media, ultramicroelectrodes are preferably used. In this work, the electro-oxidation of ferrocene has been studied in dimethylformamide (DMF)–CO2 mixtures under various CO2 pressures, using a 100 lm diameter Pt microelectrode. Tetrabutylammonium perchlorate (TBAP) was chosen as the supporting electrolyte. Cyclic voltammetry was used in order to obtain values of diffusion coefficient of ferrocene, which were determined by using the Randles–Sevcik relation. This method proved to be convenient in such low polarity solvent. In addition, fluid phase equilibria of CO2–DMF mixtures were calculated and pressure–composition phases diagrams were established for the concerned binary mixtures, thanks to commercial Prophy PlusTM software (Prosim S.A., France). So, both liquid phase expansion, due to swelling by high-pressure CO2 and effective bulk concentration of ferrocene were estimated. Nevertheless, electrochemical measurements were problematic when high-pressure single phase conditions of CO2–DMF mixtures were reached

Electrocarboxylation in supercritical CO2 and CO2-expanded liquids

In this study, the electrocarboxylation of benzyl chloride in pressurized CO2, or pressurized mixtures of dimethylformamide (DMF) and CO2, was investigated in order to synthesize phenylacetic acid. A stainless steel cathode was used as the working electrode, whereas a sacrificial massive magnesium rod or a platinized platinum grid was used as the anode, tetrabutylammonium perchlorate (TBAP) or tetrakis(decyl)ammonium tetraphenylborate (TDATPhB) being the supporting electrolyte. The electrocarboxylation was carried out at 40 ◦C, at operating pressures of 1, 6, 7, 8, 9 and 12MPa, using current densities ranging from 0.1 to 150mAcm−2. It was found that a small amount of DMF was necessary to ensure the solubility of the supporting electrolyte, to obtain sufficient electrical conductivity of the medium. The best resultswere obtained using the magnesium sacrificial anode, at 6MPa. After consumption of the theoretical amount of electrical current (2F mol−1), 65.7% benzyl chloride conversion was reached, together with an 82.4% phenylacetic acid selectivity and a 54.2% faradaic yield. Detected by-productswere toluene, bibenzyle, benzyl alcohol and benzaldehyde

Mise au point d'un procédé de carboxylation par électrosynthèse en milieu co2 sous pression et application en chimie fine

Nous proposons ici d'utiliser le co2 sous pression comme solvant et réactif pour réaliser la carboxylation électrochimique du chlorure de benzyle. Un co-solvant, le dimethylformamide (DMF), est nécessaire pour permettre la solubilisation du sel assurant la conductivité du milieu. Le comportement thermodynamique du mélange co2-DMF constituant lco2ilieu électrolytique a été modélisé en utilisant le modèle de Huron-Vidal. Le milieu a été caractérisé en utilisant une microélectrode pour déterminer le coefficient de diffusion d'un composé modèle, le ferrocène, en utilisant comme sel le perchlorate de tétrabutylammonium. La carboxylation du chlorure de benzyle dans de tels milieux a été réalisée en utilisant une anode de magnésium soluble, pour des pressions allant de O.1 MPa à 12 MPa. La suppression du co-solvant et l'emploi d'un sel hydrophobe, le tétraphénylborate de tétrakis(décyl)ammonium, ont été étudiés en vue d'un procédé sous conditions supercritiques du mélange co2-DMF. ABSTRACT : We propose here to use pressurized co2 as a reagent and a solvent to perform electrochemical carboxylation of benzyl chloride. A co-solvent, dimethylformamide (DMF), has to be used to solubilize the ionic salt allowing electrical conductivity of the mixture. Thermodynamics of the mixture co2-DMF were modelled using Huron-Vidal model. with tetrabutylammonium perchlorate as the salt, the medium was characterized using a microelectrode to obtain diffusion coefficient of a model compound, the ferrocene. Carboxylation of benzyl chloride was studied with the sacrificial magnesium anode process. Replacement of DMF by benzyl chloride and use of an hydrophobic salt, tetrakis(decyl)ammonium tetraphenylborate, was also considered to set up the process under supercritical co2-solvent mixture conditions

Mise au point d'un procédé de carboxylation par électrosynthèse en milieu co2 sous pression et application en chimie fine

Nous proposons ici d'utiliser le co2 sous pression comme solvant et réactif pour réaliser la carboxylation électrochimique du chlorure de benzyle. Un co-solvant, le dimethylformamide (DMF), est nécessaire pour permettre la solubilisation du sel assurant la conductivité du milieu. Le comportement thermodynamique du mélange co2-DMF constituant lco2ilieu électrolytique a été modélisé en utilisant le modèle de Huron-Vidal. Le milieu a été caractérisé en utilisant une microélectrode pour déterminer le coefficient de diffusion d'un composé modèle, le ferrocène, en utilisant comme sel le perchlorate de tétrabutylammonium. La carboxylation du chlorure de benzyle dans de tels milieux a été réalisée en utilisant une anode de magnésium soluble, pour des pressions allant de O.1 MPa à 12 MPa. La suppression du co-solvant et l'emploi d'un sel hydrophobe, le tétraphénylborate de tétrakis(décyl)ammonium, ont été étudiés en vue d'un procédé sous conditions supercritiques du mélange co2-DMF

Direct-to-metal UV-cured hybrid coating for the corrosion protection of aircraft aluminium alloy

Finding eco-efficient and environmentally viable alternatives to chromate coatings represents a fundamental milestone in the aerospace industry. Here, we show a chromate-free approach to protective hybrid coatings on aluminium alloy (AA2024-T3) departing from photoinduced sol–gel and cationic polymerizations. Beginning with a film of n-alkyltrimethoxysilane and diepoxy monomer, we rely on photogenerated superacids to induce the single step formation of two inorganic and organic barrier networks. Such system combines the unique aspects of photopolymerization including fast reactions, temporal control, solvent-free composition and temperature independence. Used without chemical conversion coating or anodizing, some films have passed 2000h of salt spray testing

Mise au point d'un procédé de carboxylation par électrosynthèse en milieu CO2 sous pression et application en chimie fine

Nous proposons ici d'utiliser le co2 sous pression comme solvant et réactif pour réaliser la carboxylation électrochimique du chlorure de benzyle. Un co-solvant, le dimethylformamide (DMF), est nécessaire pour permettre la solubilisation du sel assurant la conductivité du milieu. Le comportement thermodynamique du mélange co2-DMF constituant lco2ilieu électrolytique a été modélisé en utilisant le modèle de Huron-Vidal. Le milieu a été caractérisé en utilisant une microélectrode pour déterminer le coefficient de diffusion d'un composé modèle, le ferrocène, en utilisant comme sel le perchlorate de tétrabutylammonium. La carboxylation du chlorure de benzyle dans de tels milieux a été réalisée en utilisant une anode de magnésium soluble, pour des pressions allant de O.1 MPa à 12 MPa. La suppression du co-solvant et l'emploi d'un sel hydrophobe, le tétraphénylborate de tétrakis(décyl)ammonium, ont été étudiés en vue d'un procédé sous conditions supercritiques du mélange co2-DMF.We propose here to use pressurized co2 as a reagent and a solvent to perform electrochemical carboxylation of benzyl chloride. A co-solvent, dimethylformamide (DMF), has to be used to solubilize the ionic salt allowing electrical conductivity of the mixture. Thermodynamics of the mixture co2-DMF were modelled using Huron-Vidal model. with tetrabutylammonium perchlorate as the salt, the medium was characterized using a microelectrode to obtain diffusion coefficient of a model compound, the ferrocene. Carboxylation of benzyl chloride was studied with the sacrificial magnesium anode process. Replacement of DMF by benzyl chloride and use of an hydrophobic salt, tetrakis(decyl)ammonium tetraphenylborate, was also considered to set up the process under supercritical co2-solvent mixture conditions.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF

Electrochemical determination of ferrocene diffusion coefficient in [C6MIM][PF6]–CO2 biphasic system

International audienceDiffusion coefficient is an important property in chemical industry and precise measurements can be achieved by electrochemical techniques. Study of ferrocene diffusion was carried out in 1-hexyl-3-methyl imidazolium hexafluorophosphate-dense CO2 ([C6MIM][PF6–CO2]) biphasic system using microelectrode technique. Diffusion coefficients were determined by cyclic voltammetry and Randles–Ševčík relationship in the temperature and pressure ranging from 303.15 to 333.15 K and 1–10 MPa, respectively. Computed phase simulations were also used. Two-phase system was determined whatever experimental conditions and composition tested. Volumes of heavy and light phase were estimated as well. Both electroanalytical and computed studies showed that [C6MIM][PF6]–CO2 biphasic system containing initial molar fraction of CO2 up to 0.9 can be used without decrease in diffusion coefficient values. The order of magnitude of these diffusion coefficients of ferrocene in greener aprotic media is about 10−6 m2 s−1. Theoretical analysis of ferrocene mass transport was also carried out using Sutherland formula and viscosity model based on Eyring's absolute rate theory. Dramatic decrease in [C6MIM][PF6]-CO2 mixture viscosity with x(CO2) was estimated by calculations