Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-07-11
2001-06-05
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S868000, C568S867000, C568S852000
Reexamination Certificate
active
06242655
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the preparation of ethylene glycol having reduced aldehyde impurities content and improved ultraviolet transmission characteristics by treatment of already high purity distilled ethylene glycol (99% or higher) with strong acid cation exchange resin.
2. Description of the Prior Art
Ethylene glycol is a very important chemical of commerce which is usually prepared by reaction of ethylene oxide and water. A problem which has existed is that during the preparation procedure impurities such as aldehydes are formed which are difficult to separate from ethylene glycol and which cause problems in applications where very high purity is required, for example in the manufacture of fibers.
Both physical methods as well as chemical methods have been devised for the separation of aldehydes from ethylene glycol. U.S. Pat. No. 4,349,417, for example, proposes distillation in the presence of a alkali metal compounds as a purification procedure. This patent also refers to German Ausligeschrift No. 2,558,039 as teaching ethylene glycol purification using an ion exchange resin.
This German reference in turn refers to Wertschaft patent no. 43911 which teaches that aliphatic alcohols which contain more than 2% formaldehyde can be purified by converting the formaldehyde to formal using an acid catalyst followed by distillation of the impure, formal-containing alcohol. The patent states that at formaldehyde contents of less than 2% the amount of formaldehyde which is converted to the corresponding formal is so small that it is no longer possible to conduct the workup economically. Acid form ion-exchange resins are taught as suitable catalysts.
U.S. Pat. No. 4,358,625 teaches reducing oxygen-containing impurities by treatment with alkali metal borohydride.
U.S. Pat. No. 3,904,656 teaches treating a purge stream from an ethylene oxide stripper with a cation exchange resin Amberlyst A-15, an anion exchange resin Amberlyst A-21, and a carbon bed prior to recycle.
U.S. Pat. No. 4,560,813 teaches hydrolysis of alkylene oxide using a methylate anion—containing natural and recovery of the methylate anion by contact with a solid such as anion exchange resin.
U.S. Pat. No. 5,440,058 mentions treatment of aqueous streams with weakly basic ion exchange resins which have been reacted with a bisulfite salt in order to remove aldehyde impurities.
Despite the efforts of prior workers, further improvements in the removal of impurities such as aldehydes from aqueous ethylene glycol streams is important and desirable.
The presence of even very small amounts of aldehyde impurities ie. 2000 ppm by weight or less, has a deleterious effect on the properties of ethylene glycol and it is very important that economic procedures be provided to remove these materials or to convert them to a non-harmful form.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the invention, a distilled ethylene glycol stream which contains very small amounts aldehyde impurities is contacted with a strong acid cation exchange resin which had been pretreated to remove leachables and a resulting ethylene glycol stream greatly reduced in aldehydes content and having improved ultraviolet transmission is recovered.
DETAILED DESCRIPTION
Strong acid cation exchange resins are used in the process of the invention.
Cation exchange resins containing sulfonic acid functional groups are especially preferred, such as styrene-divingl benzene polymers with sulfonic acid groups. Tulison PTR is illustrative. It is important that the strong acid resin be pretreated, preferably by a hot water followed by vacuum drying pretreatment, until substantially all of the leachable impurities associated with the resin are removed. If this is not done, although the resin is still useful for reduction of aldehyde content actually the ultraviolet transmission characteristics of the treated ethylene glycol is adversely affected.
Ethylene glycol which is purified in accordance with the invention is a distillate derived from ethylene oxide by conventional procedures and contains about 2000 ppm or less of total aldehydes, preferably 5 to 100 ppm aldehydes. Generally the ethylene glycol to be treated contains at most minor amounts of water, 0-1% by weight. Small amounts of unsaturated organic materials may also be present in the glycol to be treated.
The ethylene glycol solution is contacted with the solid strong acid resin at moderate temperatures, eg. about 30 to 50° C. although temperatures outside this range can be used. Atmospheric pressure is preferred but higher pressures can be used. Illustrative flow rates are about 1 to 10 volumes of solution per volume of resin per hour although this can vary widely.
Ion exchange resins which are employed in practice of the invention are strongly acidic cation exchange resins which are well known articles of commerce.
A comprehensive description of strong acid exchange resin suitable for use herein and their preparation can be found in Kirk-Othmer, Encyclopedia of Chemical Technology, 5th Edition, Vol 14 pages 747-749 (1990).
REFERENCES:
patent: 3732320 (1973-05-01), Ford
patent: 4349417 (1982-09-01), Rebsdat et al.
patent: 4358625 (1982-11-01), Paggini et al.
patent: 5294305 (1994-03-01), Craft, Sr. et al.
patent: 2558039 A1 (1975-12-01), None
Long William C.
Price Elvis O.
Richter Johann
Scientific Design Company, Inc.
LandOfFree
Glycol purification does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Glycol purification, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Glycol purification will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2448849