CA1330350C

CA1330350C - Method for purification of ethylene glycol

Info

Publication number: CA1330350C
Application number: CA 547209
Authority: CA
Inventors: Thomas Martin Schmitt; Pauls Davis; George Mark Allen
Original assignee: BASF Corp
Current assignee: BASF Corp
Priority date: 1986-10-07
Filing date: 1987-09-17
Publication date: 1994-06-21
Anticipated expiration: 2011-06-21

Abstract

METHOD FOR PURIFICATION OF ETHYLENE GLYCOL
Abstract of the Disclosure The invention discloses a method for purifying ethylene glycol by using an ion exchange resin. The anion exchange resin adsorbs aldehyde impurities from the ethylene glycol. A basic anion exchange resin is prepared in a bisulfite or a hydroxyl form. The ethylene glycol passed through the column under air or nitrogen gas atmospheric conditions. As a result, aldehydes are absorbed as their bisulfite adducts. Subsequently, the ethylene glycol may be treated by carbon adsorption to improve the UV/visible absorbance. A weakly basic resin such as Amberlte? IR-45 is preferred, but other anion exchange resins are also expected to be effective.

Description

~ 330350 2~15 METHOD FOR PURIFICATION OF ETHYLENE GLYCOL
Background o~ the Invention 1. Fleld of Inventi~n Ethylene glycol is ~sed in a number of commercial applications, particularly to manuacture polyester fiber.
Fiber grade ethylene glycol has stringent specifications and, because of its end use, requires high purity. Many impurities in the ethylene glycol can interfere with the use of the ethylene glycol in subsequent reactions, resulting in product with undesirable properties. Conventional~methods of purification of ethylene glycol are often too costly for use in converting technical grade ethylene glycol to ~iber grade product.
It is an object of this invention to di~close a ~;
process for purifying ethylene glycol which is economical `
and industrially feasible. It is a further objective to reduce the aldehyde impurity level in ethylene glycol to a level within the maximum aldehyde speciEication for poly-, ester grade materials, that is, less than or equal to lO ppm. It is a Eurther object to provide a process for removing impurities with a material which can be regenerated easily and reused. These and other objects which will become apparent to those skilled in the art ~re accomplished ~ : '`.
by the process of the invention. ~

Description of Prior Art The use of ion exchange resins for purification purposes i~ well known in the ar-t. In particular, snion exchange resins are used for purification of ethyl alcohol specific from aldehyde compounds. However, this technology hss not been applied to purification of other substances, in particular ethylene glycol.
Summary of the Invention The invention discloses a method for purifying ethylene glycol by contacting it with an anion exchange resin. The anion exchange resin-~sorbs the aldehyde from the ethylene glycol. This anion exchange resin converted to bisulfite or a hydroxyl form and the impure ethylene glycol is passed through the column (in the latter case, with admixture of bisulfite ion) thereby removing aldehydes. Subsequently, if necessary, the ethylene glycol can be further treated by activated carbon to obtain the desired the UV/visible absorbance values.
Description of the Preferred Embodiment Product specifications for ethylene glycol and polyester fiber grade ethylene glycol are less than or equal '~
to lO ppm of aldehyde impurities. Much of the ethylene glycol commercially manufactured contains levels of aldehyde impurities which, while low are greater than the specifi- -cation for polyester grade ethylene glycol. The conven-~'`` .

tional method of purifying ethylene glycol is by redistilla-tion. However, this adds to the cost and is not an economical option. Until now, if a plant, for whatever reason, produced technical ethylene glycol containing undesirable level of aldehyde impurities, the only option was to divert that product to markets other than manufacture of polyester fibers.
The subject invention as broadly disclosed hereinafter is concerned with a process for purifying ethylene glycol, using an anion exchange resin to do so.
Such a use of an anion exchange resin can effectively reduce the aldehyde impurities level to less than or equal to 10 ppm by adsorbing aldehydes in the form of bisulfite~
adducts. The resulting aldehyde impurity level in ethylene glycol can be then within the specification for polyester grade materials. ~
In the process according to the invention, ~ -ethylene glycol is treated with an anion exchange resin to remove the aldehydes.
In accordance with the invention as claimed hereinafter, the resin that is used is in the hydroxide form and bisulfite ions are added to the ethylene glycol. Thus, the invention as claimed hereinafter is directed to a process for removing impurities from ethylene glycol comprising adding bisulfite ions to said ethylene glycol and contacting the resulting mixture with an anion exchange resin converted to a hydroxyl form, without any other preliminary treatment.
According to another embodiment of the invention disclosed hereinafter but not claimed, the resin may converted to the bisulfite form and ethylene glycol passed through it as such. Conditionlng the column in the bisulfite form with either bisulfite ion in water or with :`` `~ :

bisulfite ion in ethylene glycol are equally effective for reducing the aldehyde le~el.
Subsequently, in both cases, the ethylene glycol can be treated with activated carbon.
The following non restrictive description will better define the invention as disclosed and claimed .

/

3a ,, '~ _ ., A) ~ydroxyl Form 1) An anion exchange resin such as Amberlite~ IR-45, a weakly basic resin, is preswollen with fiber grade ethylene glycol, degassed and transferred into 8 chromatography column. The column i9 prewashed wi~h fiber grade ethylene glycol. Sodium bisulfite dissolved in impure ethylene glycol is applied to the column, followed by impure ethylene glycol without bisulfite.
2) An anion exchange resin such as Amberlite~ IR-45, hydroxyl form, is preswollen with deionized wàter for a period of time, degassed and charged into a liquid chromatography column. After equilibration with fiber grade ethylene glycol, impure ethylene glycol with predissolved sodium bisulfite is passed ;
through the anion exchange column and the flow rate was maintainèd by pressurized oxygen free nitrogen gas. The receiver is evacuated by aspiration. The difference between 1) and 2) is that gravity feed is used in 1) and nitrogen gas pressure is applied in 2).

B) Bisulfite Form 1) An anion exchange resin as in the above example is packed into a column and con~erted to the bisulfite form by washing with deionized water and sodium hydroxide solution, followed by another water rinse, a rinse ~ith 0.5M sodium bisulfite solution 9 another water rinse, and an ethylene glycol rinse. Fiber grade ethylene glycol is applied to the column.
2) The anion exchange column treated as in 1) was washed with fiber grade ethylene glycol. Impure recycle overhead ethylene glycol ~rom an Ethylene Glycol Plant was added to a reservoir and pres-surized with nitrogen gas. The receiver was evacuated and ethylene glycol was collected.

The snion exchange removal of aldehydes is effective in all of the above methods. Treatment of ethylene glycol by resin in the bisulfite form, or treatment of ethylene glycol/sodium bisulfite mixture by resin in the hydroxide form, are equally effective. The process may be carried out at atmospheric pressure or at elevated or reduced pressure, and the u~e of ainert gas bl&nket, such a~
nitrogen, is not obligatory, since good results have been obtained in the presence of air. However, ion exch~nge . .
treatment imparted to the product an unfavorably high ~ ~

: .:' `~.'' UY/visible absorbance, and carbon adsorption was utilized to restore this characteristic to conform to the specifi-cation. This high absorbance is not inherent to the process, but is merely due to som~ impuritieg that contaminated the original ion exchange resin.
The following examples are presented for illustra-tion of the process of the invention and the results obtained thereby.

Example 1 Fifty grams of Amberlite~ IR-45, hydroxyl formr were preswollen in 200 grams of fiber gr~de e~hylene glycol for 24 hourq. The resin was degassed and loaded into an Ace 5888-T~chromatography column. Th~ column W8S prewashed with 100 ml o~ fiber grade ethylene glycol. 0.5 grams of sodium bisulfite was dissolved in 100 grams of impure ethylene glycol and applied to the column followed by 150 grams ethylene glycol without bisulfite. Five fractions of 50 grams each were collected and the aldehyde level deter-mined. The results are as follows.

Aldehyde Concentration Description ppm Ethylene glycol, untreated27.5 Frsction l 5.5 Fraction 2 5.5 Fraction 3 3,3 Fraction 4 4.4 Fraction 5 3.3 .
The impurity level was greatly reduced by the use of the anion exchange process.
Example 2 .;
Seventy-five grams of Amberlite~ IR~45, hydroxyl form, were preswollen with 300 ml oE deionized water for 24 hour~. The resins were degassed and loaded into a liquid - 7 ~

chromatography column. The column was equilibrated with one liter of fiber grade ethylene glycol. 0.5 grams of sodium bisulfite were dissolved in 500 grams of impure ethylene glycol and added to reservoir pressurized with nitrogen gas at 2 psi. The receiver was evacuated by aspiration and ten fractions of 100 gram each were collected. The fractions were sealed under nitrogen gas and the aldehyde~ deter-mined. Fraction 10 was carbon treated and the UV spectrum measured. The results are as follows.

Aldehyde Concentration Description ppm~
Ethylene glycol, untreated 27.5 Fraction 1 3,3 Fraction 3 5.0 Fraction 5 4.4 Fraction 7 4.4 Fraction 9 6.6 % Transmittance Fraction 10 220 nm 275 nm 350 nm Before carbon adsorption 0 85 98 After carbon ~dsorption76 100 96 ;~

As can be readily seen from this example, the ;~
impurity level of aldehydes in ethylene glycol ls greatly reduced. Additional treatment by carbon adsorption results in increased transmittance which meets the fiber grade specification. -1 33035~

Example 3 An anion exchange resin was converted to the bisulfite form by washing with 1 liter deionized water, 1 liter of 1.0 normal sodium hydroxide solution 9 1 . O liter deionized water and 1.0 liter 0.5M sodium bisulfite solution followed by 1.5 liters of deionized water. One liter of impure ethylene glycol was applied to the column. Ten fractions of 100 grams each were collected and the aldehydes determined. Fraction 4 was carbon treated and the UV
spectrum determined. The results are as follows.

Aldehyde Concentration Description ppm Ethylene glycol, untreated 27.5 Fraction 1 5.5 Fraction 3 Fraction 6 8.8 Fraction 9 7,7 :'.,"'~ ~' % Transmittance "`
Fraction 10220 nm 275 nm 350 nm Before carbon adsorption 3 77 98 After carbon adsorption 90 99 92 Again, as illustrated by this example, aldehyde impurity level in the ethylene glycol is greatly reduced by the process of the invention.
~ ~;

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Example 4 An anion exchange column in the bisulfite form was washed with 500 ml fiber grade ethylene glycol. One liter of ethylene glycol was added and pressurized with nitrogen gas at 2 psi. The receiver was evacuated and ten 100 gram fractions were collected. The fractions were se~led under nitrogen ga~ and the aldehydes determined. The re~ults for this example are as follows.

Aldehyde Concentration Description Ppm Ethylene glycol, untreated 13.2 Fraction 2 6.0 Fraction 4 4.5 Fraction 6 5,9 Fraction 8 6.7 ~ -Fraction lO 5.9 Once again, the aldehyde concentration in the ethylene glycol is greatly reduced by the process of the invention.

.s . ,. ,~ "

Claims

1. A process for removing impurities from ethylene glycol comprising adding bisulfite ions to said ethylene glycol and contacting the resulting mixture with an anion exchange resin converted to a hydroxyl form, without any other preliminary treatment.

2. The process of claim 1, wherein ethylene glycol is purified under nitrogen atmospheric conditions.

3. The process of claim 1, wherein said contacting step is conducted in a column.

4. The process of claim 1, 2 or 3, wherein said impurities removed from said ethylene glycol are aldehydes resulting in an ethylene glycol having a aldehyde concentration of less than or equal to 10 ppm in the ethylene glycol.

5. The process of claim 4, wherein the ethylene glycol is subsequently treated with carbon.