Anodes cell design using

Fluorine cannot be prepared directly by chemical methods. It is prepared in the laboratory and on an industrial scale by electrolysis. Two methods are employed (a) using fused potassium hydrogen-fluoride, KHFj, ill a cell heated electrically to 520-570 K or (b) using fused electrolyte, of composition KF HF = 1 2, in a cell at 340-370 K which can be electrically or steam heated. Moissan, who first isolated fluorine in 1886, used a method very similar to (b) and it is this process which is commonly used in the laboratory and on an industrial scale today. There have been many cell designs but the cell is usually made from steel, or a copper-nickel alloy ( Monel metal). Steel or copper cathodes and specially made amorphous carbon anodes (to minimise attack by fluorine) are used. Hydrogen is formed at the cathode and fluorine at the anode, and the hydrogen fluoride content of the fused electrolyte is maintained by passing in... 

Other Cell Designs. Although not used in the United States, another important cell is based on designs developed by ICl (90). Cells of this type are used by British Nuclear Fuels pic and differ from the cells shown in Figures 2 and 3 in two ways (/) the anodes used are made of the same hard, nongraphitized carbon, but are more porous and 2) the cathodes are formed from coiled tubes and provide additional cooling (91). 

Ethylene glycol can be produced by an electrohydrodimerization of formaldehyde (16). The process has a number of variables necessary for optimum current efficiency including pH, electrolyte, temperature, methanol concentration, electrode materials, and cell design. Other methods include production of valuable oxidized materials at the electrochemical cell s anode simultaneous with formation of glycol at the cathode (17). The compound formed at the anode maybe used for commercial value direcdy, or coupled as an oxidant in a separate process. 

There have been a number of cell designs tested for this reaction. Undivided cells using sodium bromide electrolyte have been tried (see, for example. Ref. 29). These have had electrode shapes for in-ceU propylene absorption into the electrolyte. The chief advantages of the electrochemical route to propylene oxide are elimination of the need for chlorine and lime, as well as avoidance of calcium chloride disposal (see Calcium compounds, calcium CHLORIDE Lime and limestone). An indirect electrochemical approach meeting these same objectives employs the chlorine produced at the anode of a membrane cell for preparing the propylene chlorohydrin external to the electrolysis system. The caustic made at the cathode is used to convert the chlorohydrin to propylene oxide, reforming a NaCl solution which is recycled. Attractive economics are claimed for this combined chlor-alkali electrolysis and propylene oxide manufacture (135). 

At present, anodes containing platinnm-ratheninm catalyst (with about 50 atom % of Ru) are used in most membrane fnel cells designed for the use of technical hydrogen. 

The situation changed drastically in the mid-1990s in view of the considerable advances made in the development of membrane hydrogen-oxygen (air) fuel cells, which could be put to good use for other types of fuel cells. At present, most work in methanol fuel cells utilizes the design and technical principles known from the membrane fuel cells. Both fuel-cell types use Pt-Ru catalyst at the anode and pure platinum catalyst at the cathode. The membranes are of the same type. 

Contrary to traditional fuel cells, biocatalytic fuel cells are in principle very simple in design [1], Fuel cells are usually made of two half-cell electrodes, the anode and cathode, separated by an electrolyte and a membrane that should avoid mixing of the fuel and oxidant at both electrodes, while allowing the diffusion of ions to/from the electrodes. The electrodes and membrane assembly needs to be sealed and mounted in a case from which plumbing allows the fuel and oxidant delivery to the anode and cathode, respectively, and exhaustion of the reaction products. In contrast, the simplicity of the biocatalytic fuel cell design rests on the specificity of the catalyst brought upon by the use of enzymes. 

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