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Electrochemical conversion of anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly or gas diffusion electrodes

a technology of anhydrous hydrogen halide and electrodes, which is applied in the field of electrochemical cells and a process for converting anhydrous hydrogen halide to halogen gas, can solve the problems of increasing the power cost per unit of cl.sub.2, and achieve the effects of reducing operating costs, increasing current density, and reducing capital investmen

Inactive Publication Date: 2001-11-06
UNIVERSITY OF SOUTH CAROLINA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

By employing a membrane-electrode assembly, where particles of electrochemically active material used for an anode and a cathode are applied directly to a membrane, the surface area contact between the electrochemically active material and the membrane is greatly increased, as compared to separate element membrane and electrode arrangements of the prior art. This increased contact enables the cell of the present invention to be run at higher current densities at a given voltage than electrochemical cells of the prior art. And as current density increases, capital investment decreases, making the present invention particularly attractive from a capital investment view point.
The electrochemical cell and process of the present invention also require lower operating costs than the electrochemical conversions of hydrogen chloride of the prior art. This is because, in general, for electrochemical conversions, as voltage increases the power cost per unit of Cl.sub.2 produced increases. The voltage required to carry out the electrochemical conversion of the present invention at a given current density is lower than the voltage at that given current density required by a corresponding electrochemical conversion of the prior art, (provided that the given current density can even be achieved by the prior art). Thus, this advantage can translate directly into lower power costs per pound of say, chlorine, generated than in the aqueous electrochemical processes of the prior art.
Moreover, the electrochemical cell and process of the present invention allow for direct processing of anhydrous hydrogen halide to essentially dry halogen gas. The term "direct" means that the electrochemical cell of the present invention obviates the need to convert essentially anhydrous hydrogen halide to aqueous hydrogen halide before electrochemical treatment or the need to remove water from the halogen gas produced. This direct production of essentially dry halogen gas, when done, for example, for chlorine, is less capital intensive than processes of the prior art, which require separation of water from the chlorine gas.
The electrochemical cell and process of the present invention also provide a process which produces drier chlorine gas with fewer processing steps as compared to that produced by electrochemical or catalytic systems of the prior art, thereby simplifying processing conditions and reducing capital costs.

Problems solved by technology

This is because, in general, for electrochemical conversions, as voltage increases the power cost per unit of Cl.sub.2 produced increases.

Method used

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  • Electrochemical conversion of anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly or gas diffusion electrodes
  • Electrochemical conversion of anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly or gas diffusion electrodes
  • Electrochemical conversion of anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly or gas diffusion electrodes

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Experimental program
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first embodiment

Water is delivered to the cathode through cathode-side inlet 22 as shown in FIG. 1 and through the channels in cathode mass flow field 28 to hydrate the membrane and thereby increase the efficiency of proton transport through the membrane. In the first embodiment, the hydrogen which is evolved at the interface between the cathode and the membrane exits via cathode-side outlet 24. The hydrogen bubbles through the water and is not affected by the electrode. Cathode current distributor 44 collects current from cathode 20, along with cathode diffuser 25, and distributes it to cathode bus 40.

second embodiment

In the second embodiment, a voltage is applied to the anode and the cathode so that the anode is at a higher potential than the cathode, and current flows to the anode bus. Anode current distributor 40 collects current from the anode bus and distributes it, along with anode diffuser 23, to the anode by electronic conduction. Molecules of essentially anhydrous hydrogen chloride are fed to anode-side inlet 14 and are transported through channels of anode mass flow field 26 to the surface of anode 12. An oxygen-containing gas, such as oxygen (O.sub.2 (g)), air or oxygen-enriched air (i.e., greater than 21 mol % oxygen in nitrogen) is introduced through cathode-side inlet 22 and through the channels formed in cathode mass flow field 28. Although air is cheaper to use, cell performance is enhanced when enriched air or oxygen is used. This cathode feed gas may be humidified to aid in the control of moisture in the membrane. Molecules of the hydrogen chloride (HCl(g)) are oxidized under th...

example

Preparation of the Coating Formulation

The coating formulation for an MEA was prepared by adding 15 g of a 50 m.sup.2 / g ruthenium dioxide (RuO.sub.2) catalyst, P-2450, commercially available from Colonial Metals, Inc. of Elkton, Md., to an empty flask which had been purged with dry nitrogen. After additional purging with nitrogen, 200 g of a solution containing a binder polymer, 2.5 wt. % copolymer polymerized from tetrafluoroethylene (TFE) and a vinyl ether which is represented by the formula CF.sub.2.dbd.CF--O--CF.sub.2 CF(CF.sub.3)--O--CF.sub.2 CF.sub.2 SO.sub.2 F dissolved in the solvent FC-40, was added to a flask with constant stirring. The ratio of the catalyst particles to the binder polymer was 3:1.

After the catalyst was fully suspended, the mixture was transferred to a laboratory ball mill and was ground overnight. After the grinding, the particle size of the ruthenium dioxide in the mixture was, on the average, about 5.mu., with many particles being less than 2.mu.. the m...

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Abstract

The present invention relates to an electrochemical cell and a process for converting anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly (MEA) or a separate membrane and electrode arrangement, such as gas diffusion electrodes with a membrane.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to an electrochemical cell and a process for converting anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly or a separate membrane and electrodes, such as gas diffusion electrodes.2. Description of the Related ArtHydrogen chloride (HCl) or hydrochloric acid is a reaction by-product of many manufacturing processes which use chlorine. For example, chlorine is used to manufacture polyvinyl chloride, isocyanates, and chlorinated hydrocarbons / fluorinated hydrocarbons, with hydrogen chloride as a by-product of these processes. Because supply so exceeds demand, hydrogen chloride or the acid produced often cannot be sold or used, even after careful purification. Shipment over long distances is not economically feasible. Discharge of the acid or chloride ions into waste water streams is environmentally unsound. Recovery and feedback of the chlorine for the manufacturing process is the m...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): C25B1/24C25B9/06C25B9/04C25B1/26C25B9/10C25B1/00H01M8/24H01M8/02C25B9/23H01M4/86H01M4/88H01M4/92H01M8/10
CPCB01D61/44C25B1/02C25B1/16C25B1/22C25B1/24C25B1/26C25B15/08H01M4/8605H01M4/881H01M4/8828H01M4/8835H01M4/8882H01M4/8896H01M4/92H01M4/923H01M4/925H01M4/928H01M8/0206H01M8/0208H01M8/0213H01M8/0228H01M8/1004H01M8/247H01M2300/0082Y02E60/50C25B9/65C25B9/23
Inventor ZIMMERMAN, WILLIAM H.TRAINHAM, III, JAMES ARTHURLAW, JR., CLARENCE GARLANNEWMAN, JOHN SCOTT
Owner UNIVERSITY OF SOUTH CAROLINA
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