Chlor alkali process

Chlorine Plant Auxiliaries. Flow diagrams for the three electrolytic chlor—alkali processes are given in Figures 28 and 29. Although they differ somewhat in operation, auxiUary processes such as brine purification and chlorine recovery are common to each. 

Asahi Chemical Membrane Chlor—Alkali Process, Asahi Chemical Industry Co., Ltd., Tokyo, Japan, 1987. 

Y. Sajima, K. Sato, and H. Ukihashi, Recent Progress of Asahi Glass Membrane Chlor—Alkali Process, AICHE Symp. Ser. 82(248), 108 (1985). 

Membrane Chlor—Alkali Process, Oronzio De Nora Technologies, BV Milan, Italy and Houston, Tex., 1988. 

The starting material for all industrial chlorine chemistry is sodium chloride, obtained primarily by evaporation of seawater. The chloride ion is highly stable and must be oxidized electrolytically to produce chlorine gas. This is carried out on an industrial scale using the chlor-alkali process, which is shown schematically in Figure 21-15. The electrochemistry involved in the chlor-alkali process is discussed in Section 19-. As with all electrolytic processes, the energy costs are very high, but the process is economically feasible because it generates three commercially valuable products H2 gas, aqueous NaOH, and CI2 gas. 

Celdecor A process for making paper from straw or bagasse. The fiber is digested in aqueous sodium hydroxide and bleached with chlorine. The essential feature is that the alkali and chlorine are used in the proportions in which they are made by the Chlor-Alkali process. 

Diaphragm cell A family of electrochemical chlor-alkali processes using cells with semi-permiable membranes which minimize diffusion between the electrodes. The overall reaction is 2NaCl + 2H20 = 2NaOH + H2 +C12... 

Glanor A Chlor-Alkali process using a bipolar diaphragm cell. Developed by PPG Industries and Oronzio de Nora Impianti Elettrochimic in the early 1970s. 

SAMEX A process for removing traces of mercury from the waste brine from the chlor-alkali process. 

Tekkosha An electrolytic process for obtaining sodium from the sodium amalgam formed in the chlor-alkali process. The electrolyte is a fused mixture of sodium hydroxide, sodium iodide, and sodium cyanide. The sodium deposits at the iron cathode. Developed by Tekkosha Company, Japan, in the 1960s and commercialized in 1971. 

PCDFs are also found in residual waste from the production of vinyl chloride and the chlor-alkali process for chlorine production. Factors favourable for the formation of PCDD/PCDFs are high temperatures, alkaline media, the presence of ultraviolet light, and the presence of radicals in the reaction mixture/chemical process (Fiedler, 1999 Hutzinger and Fiedler 1993). 

Chlor-alkali cell gas effluent, gas purification, l 618t Chlor-alkali electrolytic process, 13 809 Chlor-alkali processes, 13 775... 

The substitution of conventional hydrogen-evolving cathodes with oxygen-consuming gas-diffusion electrodes (GDE), often referred to as oxygen-depolarised cathodes (ODC), also allows a substantial reduction in the energy consumption of the chlor-alkali process. 

Many other goals lie ahead for the further advancement of the membrane chlor-alkali process and technology. Asahi is dedicated to achieving these goals and to providing new standards of efficiency and performance in the future. 

You have already seen that chlorine gas can be made by the electrolysis of molten sodium chloride. In industry, some chlorine is produced in this way using the Downs cell described earlier. However, more chlorine is produced in Canada using a different method, called the chlor-alkali process. In this process, brine is electrolyzed in a cell like the one shown in Figure 11.32. Brine is a saturated solution of sodium chloride. 

The half-reactions and the overall cell reaction in the chlor-alkali process are as follows. 

The products of the chlor-alkali process are all useful. Sodium hydroxide is used to make soaps and detergents. It is widely used as a base in many other industrial chemical reactions, as well. The hydrogen produced by the chlor-alkali process is used as a fuel. Chlorine has many uses besides water treatment. For example, chlorine is used as a bleach in the pulp and paper industry. Chlorine is also used in the manufacture of chlorinated organic compounds, such as the common plastic polyvinyl chloride (PVC). 

Would you predict the products of the chlor-alkali process to he hydrogen and chlorine Explain. 

The chlor-alkali process,34 in which seawater is electrolyzed to produce Cl2 and NaOH, is the second most important commercial electrolysis, behind production of aluminum. 

Approximately two-thirds of atmospheric mercury comes from human activities, including coal burning, waste incineration, and Cl2 production by the chlor-alkali process (Problem 17-7). 

Mercury is directly below cadmium in the periodic table, but has a considerably more varied and interesting chemistry than cadmium or zinc. Elemental mercury is the only metal that is a liquid at room temperature, and its relatively high vapor pressure contributes to its toxicological hazard. Mercury metal is used in electric discharge tubes (mercury lamps), gauges, pressure-sensing devices, vacuum pumps, valves, and seals. It was formerly widely used as a cathode in the chlor-alkali process for the manufacture of NaOH and Cl2, a process that has been largely discontinued, in part because of the mercury pollution that resulted from it. 

Ion-exchange membranes are currently used not only for more or less conventional separation processes like membrane electrolysis (mainly the chlor-alkali process), electrodialysis, dialysis or electro-ultrafiltration (cf. Table 2.1), but also in various... 

The largest scale synthesis based on electrolysis is the chlor-alkali process. Sodium ions in a salt brine migrate... 

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