Hydrogen Fluoride–Paraffin Systems

Butler, Erick; Miles, C. B.; Kühn, Christian

doi:10.1021/ie50434a016

Cited by 8 publications

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“…247 with the U. S. Army Engineer Research and Development Laboratories, Fort Belvoir, Virginia, to develop a technology which will facilitate the design and fabrication of practical military fuel cell power plans for operation on ambient air and hydrocarbon fuels. Manuscript received Feb. 18, 1967; revised manuscript received May 3, 1967. This paper was presented at the Cleveland Meeting, May 1-6, 1966.…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…This requires that the product of the concentration of dissolved hydrocarbon and its diffusion coefficient be large enough (and therefore, diffusion fast enough) that the adsorption step is the slower process. It is known that hydrofluoric acid enhances the solubility of saturated hydrocarbons in water (18), and it is expected that the fluoride anion is not adsorbed on platinum electrodes (19,20). For these reasons and because of the fact that fuel cells using hydrofluoric acid electrolyte oxidize saturated hydrocarbons at high current densities, it was decided that a study would be made of the adsorption of a saturated hydrocarbon on platinum in hydrofluoric acid.…”

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The Kinetics of Propane Adsorption on Platinum in Hydrofluoric Acid

Cairns

Breitenstein

1967

J. Electrochem. Soc.

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As a first stage in the investigation of the electrochemical oxidation of saturated hydrocarbons on platinum in acid electrolytes, the rate of adsorption of propane on a smooth platinum electrode was studied at 90~ in 37 mole % HF. Using an all-PTFE apparatus and single linear voltage sweep techniques, the surface coverage by hydrocarbon species was measured as a function of adsorption time and potential. The steady-state coverage resulting from propane adsorption shows a sharp maximum at 0.2v (vs. rhe). The amount of the most electrochemically active species is highest at 0.3v. The adsorption rate follows Langmuir kinetics with a third-order dependence on free surface. The rate constant has been measured for 0.2 and 0.3v at 90~During the last few years there has been an active interest in the direct anodic oxidation of saturated hydrocarbons in fuel cells (1-10). Exploratory fuel cell investigations pointed out the usefulness of strong acid electrolytes in this connection. The acidic electrolytes which have received the most attention in hydrocarbon fuel cells are ,sulfuric acid (1), phosphoric acid (2-4), hydrofluoric acid (5-8), and cesium fluoride-hydrofluoric acid mixtures (5,6,9,10). In order to understand better the kinetics and mechanisms involved in the over-all process of anodic oxidation of hydrocarbons, it is desirable to study the various individual steps in the process, starting with the adsorption of the hydrocarbon on a suitable electrode material in the presence of electrolyte.Some work on the adsorption of methane (11) and ethane (12, 13) on platinum in perchloric acid has been done at temperatures below those where significant reactivity is shown in fuel cells. The results of Gilman (12) on ethane adsorption on platinum in perchloric acid were interpreted in terms of the kinetics of the adsorption process, the adsorption being second order in free surface and first order in ethane concentration. Propane adsorption on platinum in phosphoric acid has been studied (14, 15), but since the adsorption process was diffusion-controlled, no rate expressions could be derived from those results. Butane adsorption on platinum in sulfuric acid has been measured at steady state by tracer methods (16), and under unsteady-state conditions by the use of flow-through porous electrodes (17); neither investigation yielded quantitative kinetic information.In order to study the kinetics of the adsorption process, it is necessary to perform the adsorption experiments under conditions where diffusion is not controlling. This requires that the product of the concentration of dissolved hydrocarbon and its diffusion coefficient be large enough (and therefore, diffusion fast enough) that the adsorption step is the slower process. It is known that hydrofluoric acid enhances the solubility of saturated hydrocarbons in water (18), and it is expected that the fluoride anion is not adsorbed on platinum electrodes (19,20). For these reasons and because of the fact that fuel cells using hydrofluoric acid electrolyte oxidize satu...

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Section: Acknowledgmentsmentioning

confidence: 99%

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confidence: 99%

The Kinetics of Propane Adsorption on Platinum in Hydrofluoric Acid

Cairns

Breitenstein

1967

J. Electrochem. Soc.

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“…Since the solubility of isobutane is only 0.07 weight % in 98.7% sulfuric acid at 13.3°C. (Cupit et al, 1961) and 3.1 weight % in hydrogen fluoride (Butler et al, 1946), it appeared worth while to look for an acid phase that would dissolve more isobutane, yet not favor the side reactions.…”

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confidence: 99%

Isobutane-Olefin Alklation with Inhibited Aluminum Chloride Catalysts

Roebuck¹,

Evering²

1970

Product R&D

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“…With the above results in mind, an attempt was made to increase the solubility of the hydrocarbons in the cesium-salt electrolyte by substituting fluoride anion for a portion of the carbonate anion. This choice was made because H F is known to increase the solubility of hydrocmbons in aqueous solution (9), and because the fluoride anion is not expected to be specifically adsorbed on the electrodes (10,11). The effect of fluoride content of the Cs2COa-CsF-HF-H20 elec-Fig.…”

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Hydrocarbon Fuel Cells with Fluoride Electrolytes

Cairns

1966

J. Electrochem. Soc.

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Fuel cell investigations using saturated hydrocarbon fuels with aqueous cesium salt electrolytes and Teflon bonded platinum electrodes have shown that the acidic system normalCsF‐HF‐H2O comprises a suitable set of electrolytes for high performance hydrocarbon fuel cells. The effects of electrolyte composition and temperature on cell performance were studied with emphasis on propane as the fuel. Cell performance was also determined as a function of the molecular structure of the fuel using the homologous series of normal paraffins from C1 to C16. Maximum performance at 150°C was obtained at the composition F/normalCs=2.0 , H2O=10 normalmole% . The HF‐H2O azeotrope showed good performance at 110 °C on several hydrocarbons. No current or voltage cycling was observed under any conditions, in contrast to other acidic electrolytes.

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Hydrogen Fluoride–Paraffin Systems

Cited by 8 publications

References 0 publications

The Kinetics of Propane Adsorption on Platinum in Hydrofluoric Acid

The Kinetics of Propane Adsorption on Platinum in Hydrofluoric Acid

Isobutane-Olefin Alklation with Inhibited Aluminum Chloride Catalysts

Hydrocarbon Fuel Cells with Fluoride Electrolytes

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