Chlorine Reuse in Chemical Manufacturing

The environmental performance of chemical processes is governed not only by the design of the process, but also by the way the process integrates with other processes and material flows. Consider a classic example - the manufacture of vinyl chloride.

Billions of pounds of vinyl chloride are produced annually. Approximately half of this production occurs through the direct chlorination of ethylene. Ethylene reacts with molecular chlorine to produce ethylene dichloride (EDC). The EDC is then pyrolyzed, producing vinyl chloride and hydrochloric acid.

In this synthesis route, one mole of hydrochloric acid is produced for every mole of vinyl chloride. Considered in isolation, this process might be considered wasteful. Half of the original chlorine winds up, not in the desired product, but in a waste acid. But the process is not operated in isolation. The waste hydrochloric acid from the direct chlorina-tion of ethylene can be used as a raw material in the oxychlorination of ethylene. In this process, hydrochloric acid, ethylene and oxygen are used to manufacture vinyl chloride.

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