Phthalic acid diester preparation with waste stream purification and recycle

  • US 4,241,216 A
  • Filed: 01/02/1979
  • Issued: 12/23/1980
  • Est. Priority Date: 01/02/1979
  • Status: Expired due to Term
First Claim
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1. In a continuous process for the esterification of phthalic acid or anhydride with at least one saturated aliphatic alcohol containing about 4 to about 10 carbon atoms, esterification being carried out with recycling of said alcohol used in a stoichiometric excess in the presence or absence of esterification catalysts wherein said esterification results from continuously feeding said phthalic acid or anhydride, said saturated alcohol, and an organic by-product of said process derived from the extraction of the waste water product of said process with an alcohol wherein said alcohol used for the extraction is the same as that used to form said phthalic ester and said esterification is conducted in a reactor stage by reacting said acid or anhydride with said aliphatic alcohol until a level of acid to ester conversion of at least 90 percent is reached, and wherein the water of esterification is removing from the reaction and condensed in a heat exchanger together with a portion of the alcohol used to esterify and the alcohol returned to the process for use in extraction of waste water produced in the process, and wherein neutralization is effected in a neutralizing stage of the resulting diester product also containing, as organic impurities, monoester, unreacted phthalic acid and said aliphatic alcohol, and other impurities with an aqueous alkali solution at a temperature of about 80°

  • C. to 100°

    C., and thereafter forming a first organic phase and a first waste aqueous phase, and wherein said organic phase is separated by decanting and thereafter purified by steam stripping and carbon treatment to produce the desired diester product, the improvement wherein process waste water and said organic by-product of said process is purified and said by-product is recycled to said reactor stage without imparting color to said diester product by the following steps wherein(a) said first waste aqueous phase is filtered to remove solids and passed through activated carbon to remove color bodies, and thereafter(b) said first waste aqueous phase is mixed with an amount of said aliphatic alcohol to extract said organic impurities from the acidified first waste aqueous phase water while maintaining a temperature of about 35°

    C. to about 65°

    C., and(c) a second organic phase is separated from a second waste aqueous phase by decantation,(d) said second organic phase is washed and(e) a third waste aqueous phase is separated from a third organic phase, and(f) said third organic phase is recycled to said reactor stage.

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