JPS647977B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying ethers, and more specifically, the present invention relates to a method for purifying ethers, and more specifically, a crude product obtained by reacting dimethyl ether, mono- or di- or higher polyethylene glycol dimethyl ethers with ethylene oxide (hereinafter referred to as
Abbreviated as crude product. ). The production of mono- or polyethylene glycol dimethyl ether, which has recently become increasingly useful as a polar solvent without active hydrogen, a dissolving agent for metal or non-metallic hydrides, an acidic gas absorbent, or a component of various catalysts, has conventionally been carried out using the Williamson method and its It has been produced by an improved method, the hydrogenolysis of glycol ether formal. However, these conventional methods are not suitable for industrial use because the reactions themselves are complicated and large amounts of by-products are produced. Recently, a method of directly inserting ethylene oxide into dimethyl ether or mono- or polyethylene glycol dimethyl ether in the presence of a catalyst has been proposed as a more rational method (JP-A-53-34709, JP-A No. 56-8338, JP-A No. 56-8338, 56
-164131 publication, 56-166136 publication, 56-
(See Publication No. 166137). These direct insertion methods can produce the above-mentioned glycol dimethyl ethers in a single reaction, and also avoid producing large amounts of by-products such as alkali halides, which are produced stoichiometrically when using the conventional Williamson method. On the other hand, cyclic acetals such as 2-methyldioxolane, chain acetals such as methyl mono(or poly)glycol ether acetal, or hydroxyl group-containing compounds such as mono(or poly)ethylene glycol monomethyl ether, etc. The production of small amounts of by-products is unavoidable, and the treatment of these by-products poses a problem. If these by-products were to be separated simply by distillation, it would be necessary to use a rectification column with an extremely high number of plates, which is practically impossible. It cannot be recovered. Furthermore, it is virtually impossible to separate polyethylene glycol dimethyl ethers such as pentaethylene glycol dimethyl ether, which are useful as acidic gas absorbents, from polyethylene glycol monomethyl ethers by rectification, and a mixture of the two cannot be used for the above purpose. If it is used for gas absorption, its life as a gas absorbent will be significantly shortened. Other separation methods such as extraction, adsorption, and other known physical operations are nearly impossible in practice, and even if they could be performed, they would be extremely complicated. For the reasons mentioned above, the present inventors have conducted intensive studies to eliminate the small amount of the above-mentioned by-products contained in the crude product and to purify mono- or polyethylene glycol dimethyl ethers by a simple and practical method. As a result, (i) without separating the aforementioned acetals, which account for most of the minor by-products, from the crude product, they can easily be converted into glycol monomethyl ethers or glycols when they come into contact with water in the crude product. (ii) If the produced glycol monomethyl ethers or glycols are methylated with a methylating agent without separating them from the target product glycol dimethyl ethers,
Due to the contribution of the solvent effect of glycol dimethyl ethers, it can be converted into glycol dimethyl ethers with high selectivity and quickly; (iii) Therefore, most of the by-products present in the crude product can be separated from the crude product. The present invention was achieved by discovering that it is possible to convert into mono- or polyethylene glycol dimethyl ether, which is the object of the present invention, without having to do so. That is, the present invention
React the ether compounds represented by the following general formula [] with CH ₃ O (-CH ₂ CH ₂ O) - _o CH ₃ - [] (where n is 0 or a natural number from 1 to 10) with ethylene oxide. This is a method for purifying ethers, which is characterized by contacting the crude product with water to hydrolyze coexisting impurities, and then reacting with a methylating agent. The crude product used for purification, which is the object of the present invention, is a reaction product of the compounds represented by the general formula [] and ethylene oxide, and although there is no limitation on the method for producing it, it goes without saying that the acetals The purification method of the present invention should be applied to a crude product containing approximately 0.1 to 10% by weight of Such crude products are often obtained after reaction in the presence of the catalysts described in the above-mentioned publications. When bringing the crude product into contact with water, the amount of water used is required to be at least the equivalent molar amount of the acetals to be decomposed, preferably at least 3 times the molar amount. However, if we consider operational issues, separation after contact, etc.
It is preferably 20 times the mole or less. There are no particular restrictions on the contact temperature with water, but if it is too high, the decomposition of the desired product, glycol dimethyl ether, may be accelerated, which is undesirable and usually at 100°C above room temperature.
The following temperatures are preferred. The method of contacting with water may be any conventionally known method, and may be a continuous method or a batch method. In either method, it is preferable to remove aldehyde generated from the reaction between acetals and water from the system. This is to prevent ethers and aldehyde, which are present in large amounts in the system, from reacting again to form acetal, and to prevent side reactions caused by the aldehyde itself. There is no problem in using known catalysts to accelerate the hydrolysis reaction of acetals upon contact with water.
For example, acidic compounds such as hydrochloric acid, sulfuric acid, phosphoric acid, and p-toluenesulfonic acid can be used. If the above conditions are used, the hydrolysis reaction proceeds quickly and is usually almost completed within one hour, and most of the by-products in the crude product are mono(or) polyethylene glycol monomethyl ether and a small amount of polyethylene glycol monomethyl ether. mono(or) polyethylene glycol. Next, there is no particular limitation on the method for converting the above-mentioned by-product into mono(or) polyethylene glycol dimethyl ether, and a methylating agent capable of converting the terminal hydroxyl group of the above-mentioned by-product into a methoxy group may be used. Examples of the methylating agent include halogenated methane such as monochloromethane and monobromomethane, dimethyl sulfate, diazomethane, methyl orthoformate, methyl nitrite, dimethyl sulfite, dimethyl carbonate, trimethyl orthophosphate, and dimethyl orthosilicate. However, if we consider the removal of the excess water coexisting with the crude product at the end of the hydrolysis reaction mentioned above and the handling of the methylating agent, it is possible to remove the alkaline compound without necessarily removing the excess water coexisting with the crude product. Preference is given to methylation using monochloromethane or monobromomethane.
Another feature of the method of the present invention is that mono(or) polyethylene glycol dimethyl ether, the target compound of the method of the present invention, which accounts for most of the crude product, exhibits an extremely favorable solvent effect in the methylation reaction using this preferred methylating agent. I can do it. The above-mentioned alkaline compounds include simple alkali metals such as sodium, potassium, and lithium;
Examples include their hydrides, hydroxides, oxides, etc. These may be used alone or as a mixture of two or more. The amount of the above-mentioned methylating agent used is usually at least equivalent to the number of hydroxyl group terminals of the by-product present in the crude product after hydrolysis, preferably at least 2 times the equivalent, and 10 It is less than double equivalent. Ten
If the amount used exceeds two equivalents, separation and recovery of unreacted methylating agent will be troublesome, which is not preferable. There is no particular restriction on the reaction temperature, and since the reaction proceeds sufficiently quickly even at a relatively low temperature such as room temperature, a temperature below 100°C is sufficient.
This terminal methylation reaction may be carried out in a continuous manner or in a batch manner, or any combination of these methods may be used. To describe an example of a terminal methylation reaction when using methyl halide as a methylating agent, the above-mentioned crude product after hydrolysis and the above-mentioned alkali compound are placed in a reactor, and methyl halide is added under stirring. The methylation reaction is carried out by adding at once or in small amounts continuously or intermittently. The reaction time varies depending on the amount of the by-product having a hydroxyl group at the end of the reaction, but it is usually completed in about 30 minutes to 2 hours for the crude product shown in the present invention. As described above, according to the method of the present invention, most of the by-products present in the original crude product become mono- or polyethylene glycol dimethyl ether, which is the target compound, and there are virtually no other by-products that are difficult to remove. . As mentioned above, in the case where an alkali compound is added, the unreacted compound and salts generated from the methylation reaction may be separated by a known method such as filtration or separation. Thereafter, by distilling the crude product, each desired compound may be produced individually or in the form of a mixture. By using the method of the present invention, almost all impurities that cannot be separated by physical means such as distillation, extraction, or adsorption can be converted into target compounds by extremely simple operations. Therefore, the two objectives of increasing the purity and yield of target compounds can be achieved at once, which is extremely advantageous industrially. The method of the present invention will be described in detail with reference to Examples below, but the present invention is not limited thereto. Note that "parts" below indicate parts by weight unless otherwise specified. Example 1 The molar ratio of dimethyl ether/ethylene oxide was reduced to 1/1 using a boron trifluoride/water catalyst using the method described in Example 1 of JP-A-56-164131.
The impurities mainly consisting of acetals contained in the obtained crude product were
It was 3.5% by weight. 200 parts of the crude product and 15 parts of water were charged into a reactor equipped with a stirrer and a cooling tube, and the mixture was refluxed for 3 hours under reduced pressure of 700 mmHg. The generated acetaldehyde was removed from the system through a cooling pipe. Next, 20 parts of diisopropyl ether was added to 212 parts of the hydrolyzed solution and dehydrated by a known azeotropic method. After removing diisopropyl ether by distillation, 6 parts of sodium hydroxide was added to the reaction solution and the mixture was heated at 50 to 90°C. Add 7.6 parts of methyl chloride under stirring at a temperature range;
Made it react. After the reaction was completed, the liquid was filtered and the mixture was analyzed by gas chromatography, and it was found that the aforementioned impurities and mono- and polyethylene glycol monomethyl ethers were substantially absent, and the purity of dimethyl ether was 99.5% or more. . This product was rectified by a known method to obtain 99.0% each of mono-, di-, and triethylene glycol dimethyl ether.
% recovery rate and purity of 99.8% or more. The remaining tetraethylene glycol dimethyl ether had a purity of 99% or more. Example 2 A reaction was carried out using dodecatungstosilicic acid as a catalyst at a molar ratio of dimethyl ether/ethylene oxide of 1/1 using the method described in Example 1 of JP-A No. 56-166137, resulting in a reaction mainly consisting of acetals. Impurities were present in the crude product at 4.8% by weight. 200 parts of this crude product, 11 parts of water, and 5 parts of concentrated hydrochloric acid as a catalyst were placed in the same reactor in the same manner as shown in Example 1, and refluxed for 1 hour under a pressure of 700 mmHg. The generated acetaldehyde was collected outside the system through a cooler. Then, 8.2 parts of sodium hydroxide and 13 parts of dimethyl sulfuric acid were added to the reaction solution, which was dehydrated in the same manner as in Example 1 and diisopropyl ether was distilled off, and reacted with heat. After passing this reaction solution,
Analysis by gas chromatography revealed that most of the impurities and mono- or polyethylene glycol monomethyl ethers were converted to dimethyl ethers. When we conducted a distillation test on a portion of this, we were able to obtain mono-, di-, and triethylene glycol dimethyl ethers with a purity of over 99.8%, and the purity of the remaining tetra or higher ethylene glycol dimethyl ethers was also over 99.0%. It was hot. Example 3 A reaction was carried out using trifluoromethanesulfonic acid as a catalyst at a molar ratio of dimethyl ether/ethylene oxide of 1/1 in accordance with the method described in Example 1 of JP-A-56-166136. Impurities consisting of
It contained 4.0% by weight. 200 parts of this crude product and 13 parts of water were hydrolyzed in the same manner as in Example 1. Next, it was dehydrated using diisopropyl ether, and the ether was removed by distillation. To the reaction solution, 8.3 parts of methyl chloride and 7 parts of sodium hydroxide were added and treated in the manner described in Example 1. As a result, the impurities and mono- or polyethylene were removed. Most of the glycol monomethyl ethers were converted to dimethyl ethers, and the purity of the glycol dimethyl ethers was 99.5% or more. Example 4 The molar ratio of dimethyl ether/ethylene oxide was 5/5 by the method described in Example 1 of JP-A No. 53-34709.
1 was reacted using dimethyl ether boron fluoride as a catalyst, and a crude product containing 3.3% by weight of impurities mainly consisting of acetals was obtained. Hydrolysis was carried out using 200 parts of this crude product and 10 parts of water, followed by 9.5 parts of potassium hydroxide and 9.0 parts of methyl bromide.
When methylation was carried out using the method described in Example 1, it was found that there were almost no acetals or mono- or polyethylene glycol monomethyl ethers in the reaction solution, and the purity of glycol dimethyl ethers was 99.6% or more. . Example 5 A reaction was carried out according to the method described in Example 2 of JP-A No. 53-34709 using an ethylene glycol dimethyl ether/ethylene oxide molar ratio of 4/1 and dimethyl ether boron fluoride as a catalyst.
Impurities consisting mainly of acetals were present in the crude product at 3.0% by weight. When 200 parts of this crude product was hydrolyzed and methylated by the method described in Example 1, glycol dimethyl ethers containing almost no acetals and mono- or polyethylene glycol monomethyl ethers were obtained. Its purity was over 99.2%. Examples 6 and 7 The same reaction solution of dimethyl ether and ethylene oxide as in Example 1 was subjected to hydrolysis, dehydration, and isopropyl ether separation in the same manner as in Example 1, and 200 parts of the reaction solution was prepared as shown in the table below. When the reaction was carried out using the methylating agent and conditions specified and analyzed by a conventional method, the results shown in the table below were obtained. 【table】

Claims (1)

[Claims] 1 Ether compounds represented by the following general formula [] and CH ₃ O (-CH ₂ CH ₂ O)- _o CH ₃ - [] (where n is 0 or a natural number from 1 to 10) ) A method for purifying ethers, which comprises contacting a crude product obtained by reacting ethylene oxide with water to hydrolyze coexisting impurities, and then reacting with a methylating agent. 2. Claims in which the methylating agent is a methyl monohalide, and one or more compounds selected from the group consisting of an alkali metal, an alkali metal hydroxide, an alkali metal oxide, or an alkali metal hydride. The purification method according to item 1.