Vinyl resins oxychlorination process

Ethylene Dichlonde and Vinyl Chloride. In the United States, all ethylene dichloride [107-60-2] (EDC) is produced from ethylene, either by chlorination or oxychlorination (oxyhydrochlorination). The oxychlorination process is particularly attractive to manufacturers having a supply of by-product HCl, such as from pyrolysis of EDC to vinyl chloride [75-01-4] monomer (VCM), because this by-product HCl can be fed back to the oxychlorination reactor. EDC consumption follows demand for VCM which consumed about 87% of EDC production in 1989. VCM is, in turn, used in the manufacture of PVC resins. Essentially all HCl generated during VCM production is recycled to produce precursor EDC (see Chlorocarbons and Cm OROHYDROCARBONS ViNYLPOLYAffiRS). 

POLYVINYL CHLORIDE (PVC). [CAS 9002-86-2], The manufacture of polyvinyl chloride resins commences with the monomer, vinyl chloride, which is a gas, shipped and stored under pressure to keep it in a liquid state bp —14°C, fp —160°C, density (20°C), 0.91. The monomer is produced by the reaction of hydrochloric acid with acetylene. This reaction can be carried out in eidier a liquid or gaseous state. In another technique, ethylene is reacted with chlorine to produce ethylene dichloride. This is then cataiytically dehydrohalogcnatcd to produce vinyl chloride. The byproduct is hydrogen chloride. A later process, oxychlorination, permits the regeneration of chlorine from HC1 for recycle to the process. 

Chlorine and sodium hydroxide are the main products of the industrial chlor-alkali electrolysis that is described as a process example in Section 6.19. Hydrochloric acid is produced by reaction from the elements H2 and CI2 or by the reaction of chloride salts such as, for example, NaCl or CaCl2, with sulfuric acid. Other important sources of HCl are industrial chlorination processes using CI2 as chlorination agent (e.g., chlorination of benzene to form chlorobenzene and HCl or the chlorination of methane to give chloromethane and HCl) or industrial dehydrochlorination processes (e.g., production of vinyl chloride and HCl from 1,2-dichloroethane). The main uses of hydrochloric acid are addition reactions to unsaturated compounds (by hydrochlorination or oxychlorination), formation of chlorine in the Deacon process, production of chloride salts from amines and other organic bases, dissolution of metals, regeneration of ion exchange resins, and the neutralization of alkaline products. 

The production of many organic compounds requires the chlorination of feedstock chemicals (Table 3.3). This yields untreated wastewater that contains significant amounts of chlorinated methanes, ethanes, propanes, ethylenes, and propylenes. Other related processes such as chlorohydrina-tion and oxychlorination result in similar wastewater products. Furthermore, the use of vinyl chloride in the production of acrylic fibers and polyvinyl chloride resins yields chlorinated ethanes and ethylenes, whereas the production of epoxy resins results in the formation of dichloropropane and dichloropropylene through the use of epichlorohydrin (Wise and Fahrent-hold, 1981). 

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