Published September 2015
Ethylene dichloride (EDC) is used primarily for the production of vinyl chloride monomer (VCM), which is itself used mainly in the polymerization manufacture of polyvinyl chloride (PVC). EDC is also used as an intermediate in the manufacture of chlorinated solvents and as a solvent in the textile, metal cleaning, and adhesive industries.
In 2015, 98% of EDC consumption is for VCM production. Western Europe, China, and the United States have the most significant EDC consumption into non-VCM uses, primarily for chlorinated solvents, ethyleneamines, and vinylidene chloride.
The following pie chart shows world consumption of ethylene dichloride:
VCM can also be made by the hydrochlorination of acetylene, using HCl as a chlorine source. This process is used mainly in China where integrated coal chemical sites are still under development. Even though the acetylene process for VCM production is energy intensive in its first stage¾the production of calcium carbide¾there is strong motivation to pursue this route in provinces with large coal resources. However, with the recent drop in crude oil prices, expansion of acetylene-based technology in China has slowed; the ethylene/EDC route to VCM has become more competitive and is more environmentally friendly and sustainable.
Ethylene dichloride is made principally by the direct chlorination or oxychlorination of ethylene. Most EDC plants are integrated with VCM plants. The VCM process generates considerable quantities of hydrogen chloride (HCl), which is then recycled in the oxychlorination unit to generate more EDC; the cycle continues, allowing the complete conversion of input chlorine. VCM is then purified and sent to storage.
EDC plants are usually integrated upstream to chlor-alkali units and downstream to VCM units. To achieve even better economics, further integration of the vinyls chain into ethylene is desirable. Most vinyl companies follow the ethylene route, using ethylene and chlorine as the main building blocks, and are balanced in chlorine so their direct chlorination capacity is roughly equal to their oxychlorination capacity. Vinyls producers can also oxychlorinate by-product anhydrous HCl from other operations. Producers in the United States, Western Europe, and South Korea oxychlorinate a large volume of by-product HCl streams from isocyanates, fluorocarbon, and silicone operations. By expanding oxychlorination capacity, South Korea has reduced the need for virgin chlorine production for direct chlorination.
Occidental Chemical (Oxy), Formosa Group, and Dow are the top EDC producers in the world, together accounting for nearly one-fourth of the total global capacity in 2015.