Chloralkali processes based

The commercialization of phosgene processes based on hydrogen chloride, rather than dichlorine, would permit, for example, isocyanate plants to be sited at locations not dependant on chloralkali-producing facilities or large chlorine-consuming (e.g. vinyl chloride) plant. However, it is not known for certain whether any of these processes are currently commercially operated. 

A current industrial application of ionomers is their use as permselective membranes for the chloralkali process. The ionomers used in these membranes are based on a poly(tetrafluoroethylene) backbone containing occasional ether linkages with ionic side groups. These are based upon either sulfonate or carboxylate salts. 

A mixture of hydrogen and chlorine gas, eventually in combination with air, can be very explosive if one of the components exceeds certain limits. In chlorine production plants, based on the electrolysis of sodium chloride solutions, there is always a production of hydrogen. It is, therefore, essential to be aware of the actual hydrogen content of chlorine gas process streams at any time. There are several places in the chlorine production process where the hydrogen content in the chlorine gas can accumulate above the explosion limits. Within the chloralkali industry, mainly two types of processes are used for the production of chlorine—the mercury- and the membrane-based electrolysis of sodium chloride solutions (brine). 

Based on samples from museum collections, it was demonstrated that mercury content in feathers from fish-eating birds were comparatively low in the years 1815 through 1940. However, since 1940, or the advent of the chlo-ralkali industry (wherein mercury is used as a catalyst in the process to produce sodium hydroxide and chlorine gas from sodium chloride and water, with significant loss of mercury to the biosphere), mercury concentrations in feathers were eight times higher on average. Mercury levels were also elevated in feathers and tissues of aquatic and fish-eating birds from the vicinity of chloralkali plants these increased levels of mercury were detectable up to 300 km from the chloralkali plant. 

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