JP3447789B2 - Method for purifying cyclic formal - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a solvent, a pharmaceutical intermediate,
The present invention relates to a method for purifying cyclic formal useful as a resin raw material and the like. More specifically, the present invention relates to an economical purification method for efficiently removing water from a cyclic formal that is difficult to separate from water to form an azeotropic composition to obtain a highly pure cyclic formal having a low water content.

[0002]

Cyclic formal, such as 1,3-dioxolane, 1,4-butanediol formal, diethylene glycol formal, methyl-1,3-dioxolane, etc., undergoes a cyclization reaction between a corresponding glycol and an aldehyde,
It is known to be obtained by the cyclization reaction of the corresponding alkylene oxide and aldehyde. For example, as a method for producing 1,3-dioxolane which is a typical cyclic formal, West German Patent No. 1914209 discloses a method for producing 1,3-dioxolane by reacting glycol and formaldehyde in the presence of an acid catalyst. ． En
g. Chem. , 46,787 (1954) and JP-A-49-62469 disclose a method for producing 1,3-dioxolane by reacting glycol and paraformaldehyde in the presence of an acid catalyst.

[0003]

However, in the process for producing cyclic formal using glycol and aldehyde as raw materials in this way, the produced cyclic formal and azeotrope of water which is a by-product or water brought in the form of an aqueous aldehyde solution are azeotroped. In many cases, it is difficult to separate and remove water only by ordinary distillation.

For example, taking 1,3-dioxolane as an example, the above-mentioned German Patent No. 1914209 shows that the obtained 1,3-dioxolane contains as much as 7% of water. In addition, as a method for obtaining highly pure 1,3-dioxolane by removing water from a mixture containing 1,3-dioxolane and water, the method described in Ind. Eng. Chem. , 4
6,787 (1954), salt was added to a reaction distillate containing 1,3-dioxolane and water to separate into two phases,
A method of rectifying an organic phase is also disclosed in the above-mentioned JP-A-49-62.
Japanese Patent No. 469 discloses a method of purifying by adding cyclohexane to a reaction distillate, but the former method is not suitable as an industrial purification means, and the latter method is not suitable for water separation. There is a problem that it is difficult to obtain sufficient and highly pure 1,3-dioxolane. Such a phenomenon is not limited to 1,3-dioxolane, but is a problem common to cyclic formal that forms an azeotropic composition with water. Therefore, it is eagerly desired to establish an economical purification method for efficiently separating and removing water from a mixture containing cyclic formal and water to obtain a highly purified cyclic formal.

[0005]

In order to solve the above-mentioned problems, the present inventor has noticed that water is azeotroped with various solvents, and the cyclic formal 1,3-dioxola is used.
Emissions, water, the cyclic formal and various properties such as azeotrope of water even in consideration result of the intensive investigations, by supplying the n- hexane when distilling a mixture of the cyclic formal and water, said annular The azeotropic composition of formal and water collapses, and water becomes n
-Effectively distilled off together with hexane,
It was found that 3-dioxolane was obtained, and that this method was also extremely excellent in operation, and the present invention was completed.

That is, the first aspect of the present invention is a cyclic formal.
Upon purifying the cyclic formal a mixture comprising 1,3-dioxolane and water is supplied to a distillation column, purification of the cyclic formal, which comprises distilling while supplying n- hexane to the distillation column It provides a method. The second aspect of the present invention is a cyclic formal 1,
For the amount of water in the mixture containing 3-dioxolane and water,
Special feature is to supply 5 to 20 times by weight of n-hexane.
Of the cyclic formal described in the first aspect of the present invention.
It provides a manufacturing method. The third aspect of the present invention is
The cyclic formal 1,3-dioxolane concentration was 8
Pre-concentrated in the range from 0 wt% to azeotropic composition
The first or the present invention characterized by supplying a mixture;
A second method for purifying the cyclic formal is provided.
It is a thing.

The present invention will be described below with reference to the distillation apparatus shown in FIG. In FIG. 1, 1 is a distillation column, 2 is a condenser, 3 is a reboiler, 4 is a decanter, 5 is 1,3-
A supply part of a mixture containing dioxolane and water, 6 is a supply part of n-hexane, 7 is a top distillate, and 8 is a bottom bottoms. As mentioned above, the cyclic formal 1,3-di
Because oxolane is and water form an azeotrope, it is impossible to purify the cyclic formals or more azeotropic composition in normal distillation operation. However, in the present invention, by supplying an additional n- hexane in the distillation tower, it collapsed azeotropic composition between the cyclic formal and water is formed in the case of conventional distillation, n- hexane, the cyclic formal, Further, when the mixture contains impurities such as formaldehyde and reaction by-products, water is distilled off from the top of the mixture together with these impurities. On the other hand, the cyclic formals which impurities of water and low boiling point highly purified are removed is obtained as liquid exits can from the bottom.

In the present invention, n supplied for such a purpose
As n-hexane, pure n-hexane may be used, but as shown in FIG. 1, after distillate containing n-hexane and water from the top of the column is cooled, it is separated into a solvent phase and an aqueous phase. , It is economical to re-supply the solvent phase mainly composed of n-hexane to the distillation column 1, whereby the objective is sufficiently achieved.

The amount of n-hexane to be supplied is not particularly limited, but if it is small, water will migrate to the bottom side of the column and the purification efficiency of the cyclic formal 1,3-dioxolane will decrease. However, the supply of excess n-hexane requires a large amount of energy for distilling n-hexane from the top of the column, resulting in poor economic efficiency. Therefore, the supply amount of n-hexane is preferably in the range of 5 to 20 times by weight, and particularly preferably in the range of 8 to 12 times by weight of water in the mixture supplied in 5 in the figure. Is.

Supplying n-hexane as described above means that the content of water in the mixture supplied at 5 in the figure is large,
Moreover, when highly purifying 1,3-dioxolane which is a cyclic formal , a large amount of n-hexane is required. Therefore, in the present invention, the mixture of water and a moderately removed in advance by a conventional distillation operation or the like before as the concentration of the cyclic formal 80% by weight or more,
More it is preferably used as the feed solution that increased to become substantially azeotropic composition, thereby it becomes possible to reduce the supply amount of n- hexane, comprehensively also excellent the cyclic formal economical It becomes a purification method.

The cyclic formal of the present invention, 1,3-di
In the purification method of oxolane, for the supply position of the supply position and n- hexane mixture containing a said cyclic formal and water to the distillation column, a large constraint is not the case the supply position of the mixture is low, water and / or n- hexane is easily contained in the purified 1,3-dioxolane is a bottom liquid, when the supply position is high, since the distillate amount from the top of the cyclic formal is likely to increase, the supply position of the mixture As the above, it is preferable to use the middle stage region avoiding the lower 1/4 and the upper 1/4 of the distillation column. The supply form of the mixture may be liquid or gaseous. The supply position of n-hexane is preferably from the tower top to the mixture supply position, particularly preferably the tower top.

In the present invention, the distillation column used for the purification of 1,3-dioxolane is not particularly limited.
For example, bubble cap, sieve tray, uniflux tray, flexible tray, natter float bubble tray, ballast tray, cascade tray, venturi tray, kittel tray, recycling tray, chimney tray, jet tray, turbo grid tray, ripple tray, dual float. Purification is possible in all formats such as trays and baffle trays.

The distillation column may be a packed column. With regard to filling materials, all types such as ring type, saddle type, spray bag, vanaback, Goodroy packing, Stedman packing, Dixon ring, McMahon packing, Canon Brodroided metal packing, helix, cross spiral packing, etc. It can be purified by.

According to the purification method of the present invention, even when the mixture containing 1,3-dioxolane and water supplied to the distillation column further contains unreacted formaldehyde or a reaction by-product, most of them are It can be removed and purified. Further, 1,3-dioxolane obtained as bottoms from the column bottom by the purification method of the present invention is highly purified, but in the case where it is necessary to remove water, impurities, etc. to the utmost limit. It is also possible to further perform operations such as distillation and adsorption. The purification method of the present invention is
It is particularly effective as a method for purifying 3-dioxolane.

[0015]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto.

Example 1 A distillation apparatus (column diameter 50 mm, 45 plates, sieve tray) shown in FIG. 2 was used, and 1,3 at the 25th plate from the bottom of the distillation column.
36% of a mixture of 93% by weight of dioxolane and 7% by weight of water.
Distillation was carried out at a rate of 6 g / hr and n-hexane at a rate of 237 g / hr from the bottom to the 45th stage (column top). Distillate from the top of the column is 405 g / h
The composition of each liquid when the operation was stable at 198 g / hr of the bottom liquid from the tower bottom was as follows.
A highly pure 1,3-dioxolane having a very low water content was obtained. Top distillate: 1,3-dioxolane (34.2 wt
%), Water (6.5 wt%), n-hexane (59.3 w)
t%) Bottoms bottoms: 1,3-dioxolane (99.9 wt% or more), water (71 ppm), n-hexane (20 ppm)

The feed liquid used here is approximately 1,
It has an azeotropic composition of 3-dioxolane and water, and n-
Water cannot be separated and removed by a normal distillation operation without using hexane, and 1,3-dioxolane cannot be purified.

Comparative Example 1 The same operation as in Example 1 was carried out by using cyclohexane instead of n-hexane. In this case, it was difficult to continue stable operation. This is cyclohexane,
It is speculated that this is because the boiling point of the distillate from the top of the column containing water and 1,3-dioxolane is relatively high, and a sufficient temperature difference cannot be obtained between the top and bottom of the column.

Example 2 A distillation apparatus (column diameter 50 mm, 45 stages, sieve tray) shown in FIG. 3 was used, and after distillate from the top of the column was cooled, n-
Distillation was performed in the same manner as in Example 1 except that the hexane phase and the aqueous phase were separated and the n-hexane phase was returned to the distillation column. The flow rate and composition of each liquid when the operation was stable were as shown in Table 1.

[0020]

[Table 1]

[0021]

Industrial Applicability According to the purification method of the present invention, 1,3-dioxolane , which is a cyclic formal which has been difficult to purify in the prior art because it is azeotropic with water, is economically stable and highly purified. It has a high industrial value.

[Brief description of drawings]

1 is a cyclic formal of the present invention, 1,3-dioki
It is a schematic diagram which shows an example of a solan purification method.

FIG. 2 is a schematic view showing an apparatus used in Examples and Comparative Examples of the present invention.

FIG. 3 is a schematic diagram showing an apparatus used in another example of the present invention.

[Explanation of symbols]

1 Distillation column 2 Condenser 3 Reboiler 4 Detanter 5 Mixture containing 1,3-dioxolane and water (feeding part) 6 n-hexane (feeding part) 7 Top distillate 8 Bottom bottoms

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C07D 319/12 C07B 63/00 CA (STN) CASREACT (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. A cyclic formal which is 1,3-dioxo
Run and a mixture containing water is supplied to the distillation column Upon purifying the cyclic formal, purification process of the cyclic formal, which comprises distilling while supplying n- hexane to the distillation column. 2. A cyclic formal , 1,3-dioxo.
5 to 5 by weight ratio to the amount of water in the mixture containing orchid and water
Purification process of the cyclic formal of claim 1, wherein supplying a 20-fold n- hexane. 3. A cyclic formal , 1,3-dioxo.
Purification process of the cyclic formal of claim 1 or 2, wherein supplying the mixture density of the run were pre-concentrated in the range up to the azeotropic composition from 80 wt%.