Treatment of glycol

Background of invention

1. The scope to which the invention relates.

The present invention relates to the removal of impurities, such as aldehydes from aqueous solutions of ethylene glycol, by treatment with a strongly basic anion-exchange resin is treated with bisulfite.

2. The known technical solutions

Ethylene glycol is a very important industrial chemical which is usually produced by reaction of ethylene oxide with water. The current difficulty is that in the process of obtaining formed impurities such as aldehydes, which are difficult to separate from ethylene glycol and which cause difficulties in its application in cases that require a very high degree of purity, for example in the production of fibers.

For separation of aldehydes from ethylene glycol developed both physical and chemical methods. For example, in U.S. patent No. 4349417 as purification method proposed by distillation in the presence of compounds of alkali metals. This patent also mentions lined Germany application No. 2558039, which describes the purification of ethylene glycol with the use of ion exchange resins.

In U.S. patent No. 4358625 described the restoration of oxygen-containing impurities by treatment with alkali metal borohydride.

In U.S. patent No. 3904656 described processing waste stream is C column Stripping ethylene oxide before returning it to cycle cation exchange resin Amberiyst a-15, anion-exchange resin Amberlyst A-21 and active coal.

In U.S. patent No. 4560813 described the hydrolysis of the oxide alkylene using material containing methylate-anion, and removing the methylate anion by contact with solid material, such as anion-exchange resin.

In U.S. patent No. 5440058 mentioned processing flow of aqueous solutions of weakly basic ion exchange resins, which are pre-enter into reaction with bisulfite, in order to remove impurities aldehydes.

Despite the efforts of previous researchers, further improvements in the field of removal of impurities, such as aldehydes, from streams of aqueous solutions of ethylene glycol are of great importance and are desirable.

Brief description of the invention

In accordance with the present invention, a stream of an aqueous solution of ethylene glycol containing aldehyde impurities, is introduced into contact with a strongly basic anion-exchange resin treated with bisulfite, and receive a stream of an aqueous solution of ethylene glycol, in which the content of aldehydes reduced.

Detailed description

In the method in accordance with the present invention is applied strongly basic anion-exchange resin. Before coming into contact with a stream of an aqueous solution of ethylene glycol that is to be processed, these resins initially transferred to the bisulfite form by introducing contact the CT with a solution of bisulphite, such as aqueous solution of sodium bisulfite. Of course, you can use other bisulfite. When processing bisulfite strongly basic anion-exchange resin enters bisulfite form in accordance with the following reaction scheme:

resin-HE- + the solution of Na⁺SO₃→resin-HSO₃-+the solution of Na⁺OH.

Then enter into contact with the solid resin is treated with bisulfite, aqueous solution of ethylene glycol containing aldehydes, such as formaldehyde or acetaldehyde, and is separated from the solid resin aqueous solution of ethylene glycol with a lower content of aldehydes.

Regardless of theoretical considerations, it is believed that upon contact of the above-mentioned solution with silnooooo anion-exchange resin treated with bisulfite, aldehydes react ion exchange resin according to the following scheme:

resin-HSO₃- + the solution NSNO → resin-NON₂SO₃-,

as a result of which the aldehyde is associated with hard resin and, thus, removed from the solution.

Processing in accordance with the present invention provides an effective method of removing aldehydes from aqueous solution of ethylene glycol. Controlling the content of aldehydes in the output stream of the product, it is easy to determine the moment when it is necessary to regenerate the solid resin. So regenerati is easy to make by introducing the spent resin in contact with an aqueous solution of bisulfite for the reaction according to the following scheme:

resin-NON₂SO₃-+the solution of Na⁺HSO₃-→ solution of Na⁺NON₂SO₃-+resin-HSO₃-.

In the General case of aqueous solutions, processed in accordance with the present invention, contain approximately 0.2% (wt.) up to 20% (wt.) of ethylene glycol, from about 80% (wt.) up to 99.7% (wt.) water and approximately 100 million^-1(wt.) to 1.0% (wt.) aldehydes. Ethylene glycol is introduced into contact with bisulfite treated resin at a moderate temperature, for example from about 30°C to 50°With, although you can use and temperature beyond the specified range. Preference is given to the atmospheric pressure, although you can use and elevated pressure. With regard to flow rate, as examples of values from about 1 to 10 volumes of a solution of one volume of resin per hour, although this figure can vary within wide limits.

Ion-exchange resin used in the implementation of the present invention are strongly basic anion-exchange resin, which is well-known industrial products.

Such strong base resin can be obtained by the reaction between chlorotoluene copolymer of styrene with divinylbenzene and tertiary amines, such as trimethylamine, while receiving the resin, with which containing a series of Quaternary ammonium groups.

Detailed description strong anymoooore resin, suitable for use in accordance with the present invention and its preparation can be found in "Encyclopedia of chemical technology, kirk-Othmer (Kirk-Othmer, Encyclopedia of Chemical Technology, 5^thEdition, Vol.14, pages 747-749 (1990)).

The invention is illustrated by the following examples:

Strongly basic anion-exchange resin were transferred to the bisulfite form by passing through a layer of resin 5% (wt.) solution of sodium bisulfite to the practical adjustment of the concentrations of bisulfite on the input and output layer. Used resin Tulsion A-33 - cross-linked polystyrene containing Quaternary ammonium groups in the hydroxide form. Then the resin was washed with water in an amount of 10-15 volumes of water per 1 volume of resin.

Ethylene glycol solution after synthesis, containing 1% (wt.) formaldehyde, the rest is water, was passed through the bisulfite treated resin at 35°C. After the processing of this resin solution of ethylene glycol in an amount of 5 volumes of a solution of one volume of resin concentration of aldehydes in facing the solution was below 2 million^-1.

The above example was repeated using the process stream monoethylene glycol containing 5% (wt.) monoethylene glycol, 95% (wt.) water and having a total content of aldehydes 150 million^-1. In contactyou the Oia with resin, the total content of aldehydes in facing the flow decreased to 1 million ^-1.

1. The method of reducing the content of aldehydes in an aqueous solution of ethylene glycol containing from about 0.2 to 20 wt.% of ethylene glycol, from about 80 up to 99.7 wt.% water and approximately 100 million^-1(wt.) to 1.0 wt.% aldehydes, including the introduction of this solution into contact with a solid strongly basic anion-exchange resin treated with bisulfite, which before treatment bisulfite containing Quaternary ammonium functional groups in the hydroxide form.

2. The method according to claim 1, where the bisulfite is sodium bisulfite.