The majority of organic contaminates are in the crude EDC stream, which is treated with dilute caustic and then distilled. These emerge in the light and heavy ends of the distillation stage and amount to about one percent of the crude EDC fed to the unit. This product totals 200 million pounds per year of chlorocarbon contamination in the United States. In the past, these compounds were sold for recovery of chlorinated solvents, etc., but current regulations on the use of chlorocarbons have restricted this market. The current practice is to destroy the chlorocarbons by thermal incineration or catalytic oxidation.
Incineration requires very high temperatures for efficient combustion.
Catalytic oxidation requires lower temperatures, but conversions do not exceed 98 percent unless extreme processing conditions are practiced. In addition, many of the catalysts used are sensitive to Cl poisoning. Both methods emit large amounts of CO 2 and the only recycle in the process is HCl . Strategies to reduce and control these wastes require forethought and planning, especially since health and regulatory requirements now play a greater part in the overall economics. The catalyst used in the oxychlorination stage has been well developed, and no further refinements in selectivity appear likely.