Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-04-03
2001-10-09
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S727000
Reexamination Certificate
active
06300528
ABSTRACT:
This application relates to a method for cleaning reactors used for acid-catalyzed production of bisphenols.
BACKGROUND OF THE INVENTION
Bisphenols, and in particular bisphenol A (2,2 bis(p-hydroxyphenyl) propane), have become industrially significant reactants for a number of processes including the preparation of polycarbonates. Bisphenols are prepared on an industrial scale by one of two processes: an acid-catalyzed or HCl process and an ion exchange process, in which an acidic ion exchange resin such as sulfonic acid-substituted polystyrene is employed. In the HCl process, the bisphenol is prepared by condensation of two moles of phenol with one mole of a ketone or aldehyde, for example acetone, in the presence of HCl. Processes for the production and purification of bisphenols are well known, and are described inter alia in U.S. Pat. Nos. 4,107,218; 4,294,994; 5,210,329; 5,243,093; 5,245,088; 5,288,926; 5,368,827; 5,786,522; and 5,874,644.
During the course of producing, bisphenols by this process, the solubility of the product bisphenol is not always high enough for all of the bisphelnol produced to be dissolved. As a result, the bisphenol may crystallize out as a bisphenol-phenol adduct on the inner surface of the reactor. This layer reduces heat exchange efficiency within the reactor, and hence limits reactor temperature control. The result is a lower quality product, and/or reduced plant capacity. Thus, the reactor used in the production of bisphenols needs to be cleaned periodically to remove any build-up of the bisphenol-phenol adduct. In accordance with known methods, this cleaning is done by either filling the reactor with pure phenol or by charging extra water or acid into the reactor. These actions increase the solubility of bisphenol in the mixture and built-up bisphenol-phenol adduct dissolves. Unfortunately, product produced during such cleaning does not meet specifications. This means that the time spent for cleaning is effectively down time for the reactor. There is therefore a need for a method for cleaning reactors used in the production of bisphenols which allows the cleaning to occur without significant production loss, plant instability or quality loss.
SUMMARY OF THE INVENTION
In accordance with the present invention, cleaning of a reactor used in the production of bisphenols is enhanced by heating the reactor wall, for example by the introduction of steam into the shell surrounding the reactor. The steam heats the wall which lies between the shell and the interior reaction chamber, and thus facilitates melting/dissolution of bisphenol:phenol adduct that has formed on the wall on the inside of reaction chamber. The steam is introduced for a period of at least 5 minutes, and preferably for a period of from 5 to 60 minutes.
In a further embodiment of the invention, a solubility-increasing composition is introduced into the reaction chamber to increase the solubility of the bisphenol during the introduction of steam. Suitable solubility-increasing compositions comprise hydrochloric acid and/or water, or a mixture of acetone and phenol.
REFERENCES:
patent: 4107218 (1978-08-01), Konrad et al.
patent: 4294994 (1981-10-01), Li
patent: 5210329 (1993-05-01), Gomes de Matos et al.
patent: 5243093 (1993-09-01), Kissinger et al.
patent: 5245088 (1993-09-01), Fimuro et al.
patent: 5288926 (1994-02-01), Patrascu et al.
patent: 5368827 (1994-11-01), Moriya et al.
patent: 5786522 (1998-07-01), Cipullo
patent: 5856589 (1999-01-01), Cipullo
patent: 5874644 (1999-02-01), Gammill
patent: 6011184 (2000-01-01), Aarssen
patent: 99/51558 (1999-10-01), None
Klaverveld Marcellinus Adrianus
Op Den Dries Gerrit
Schlarmann Eduard Hendricus
Soeters Martin Jaco
Van Dooremal Guido Theodorus Fridiswidus Maria
General Electric Company
Oppedahl & Larson LLP
Shippen Michael L.
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