Extraction process for removal of impurities from an oxidizer purge stream in the synthesis of carboxylic acid
View Patent ↗Disclosed is a process that relates to the recovery of a metal catalyst from an oxidizer purge stream produced in the synthesis of carboxylic acid, typically terephthalic acid. The process involves the addition of a wash solution to a high temperature molten dispersion to recover the metal catalyst and then subjecting an aqueous mixture or purified aqueous mixture so formed to a single stage extraction to remove organic impurities to produce an extract stream and a raffinate stream comprising the metal catalyst.
1. A process comprising:
(a) subjecting an oxidizer purge stream comprising a carboxylic acid, a metal catalyst, impurities, water and a solvent to evaporation in a first evaporator zone to produce a vapor stream and a concentrated purge slurry; and
(b) subjecting said concentrated purge slurry to evaporation in a second evaporator zone to produce a solvent rich stream and a high temperature molten dispersion; wherein about 95 wt % to about 99 wt % of said solvent and water present in said oxidizer purge stream from step (a) is removed and wherein said second evaporator zone comprises an evaporator operated at a temperature of about 150° C. to about 200° C.;
(c) mixing in a mixing zone a wash solution with said high temperature molten dispersion to form an aqueous mixture;
(d) adding an extraction solvent to said aqueous mixture in an extraction zone to form an extract stream and a raffinate stream; and
(e) separating said extract stream and said solvent rich stream in a separation zone to form a high boiling point organic impurities stream.
2. The process according to claim 1 wherein a wash solution is added to quench said aqueous mixture to a temperature range of about 60° C. to about 95° C.
3. The process according to claim 1 wherein a said wash solution is added to quench said aqueous mixture to a temperature range of 80° C. to about 90° C.
4. The process according to claim 1 wherein said extraction zone comprises a counter current extractor.
5. The process according to claim 1 wherein said extraction zone comprises a single stage extractor.
6. The process according to claim 1 wherein said solvent rich stream comprises a solvent selected from the group consisting of n-propyl acetate, isopropyl acetate, isobutyl acetate, sec-butyl acetate, ethyl acetate, n-butyl acetate and mixtures thereof.
7. The process according to claim 6 wherein said second evaporator zone comprises an evaporator operated at a pressure of 1 atmosphere to about 10 atmospheres.
8. A process comprising:
(a) subjecting an oxidizer purge stream comprising a carboxylic acid, a metal catalyst, impurities, water and a solvent to evaporation in a first evaporator zone to produce a vapor stream and a concentrated purge slurry; and
(b) subjecting said concentrated purge slurry to evaporation in a second evaporator zone to produce a solvent rich stream and a high temperature molten dispersion; wherein about 95 WT % to about 99 wt % of said solvent and water present in said oxidizer purge stream from step (a) is removed; and wherein said second evaporator zone comprises an evaporator operated at a temperature of about 150° C. to about 200° C.;
(c) mixing in a mixing zone a wash solution with said high temperature molten dispersion to form an aqueous mixture;
(d) separating organic impurities from said aqueous mixture in a solid-liquid separation zone to form a purified aqueous mixture;
(e) adding an extraction solvent to purified aqueous mixture in an extraction zone to form an extract stream and a raffinate stream; and
(f) separating said extract stream and said solvent rich stream in a separation zone to form a high boiling point organic impurities stream.
9. The process according to claim 8 wherein said a wash solution is added to quench said aqueous mixture to a temperature range of about 600° C. to about 95° C.
10. The process according to claim 8 wherein a wash solution is added to quench said aqueous mixture to a temperature range of 80° C. to about 90° C.
11. The process according to claim 8 wherein said extraction zone comprises a counter current extractor.
12. The process according to claim 8 wherein said extraction zone comprises a single stage extractor.
13. The process according to claim 8 wherein said solvent rich stream comprises a solvent selected from the group consisting of n-propyl acetate, isopropyl acetate, isobutyl acetate, sec-butyl acetate, ethyl acetate, n-butyl acetate and mixtures thereof.
14. The process according to claim 13 wherein said second evaporator zone comprises an evaporator operated at a pressure of 1 atmosphere to about 10 atmospheres.