JPH07179397A - Method for extracting and separating methyl methacrylate - Google Patents

Abstract

PURPOSE:To efficiently obtain high-purity methyl methacrylate without the need for much thermal energy in separating and isolating the methyl methacrylate from a solution containing methanol at high concentrations and also containing both water and the methyl methacrylate. CONSTITUTION:A solution containing >=30wt.% of methanol and also containing both methyl methacrylate and water is brought into contact with an aliphatic saturated hydrocarbon 105-300 deg.C in boiling point to extract the methyl methacrylate, which is then separated by distillation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for separating MMA from a solution containing at least methyl methacrylate (hereinafter abbreviated as MMA), methanol and water. MM
A is transparent and has good gloss, and is excellent in electric insulation, chemical resistance and workability, and therefore has a wide range of applications such as building materials, various appliances, paints and adhesives.

[0002]

2. Description of the Related Art Conventionally, as a method for producing MMA, an acetone cyanohydrin method, a direct oxidation method of a C4 fraction such as isobutylene, and a method for synthesizing methacrylic acid by dehydration hydration reaction of α-hydroxyisobutyric acid amide, Then, a so-called vapor-phase method in which an esterification reaction is performed with methanol in a vapor phase is known.

Of these, in the acetone cyanohydrin method and the direct oxidation method, methanol is added in an amount more than the necessary amount for esterification in order to improve the yield of MMA. The unreacted methanol concentration is 25% by weight or less. Therefore, in order to separate MMA from these reaction liquids, a method of extracting methanol in the reaction liquid with water is usually adopted.

[0004]

However, when MMA is produced by the above-described vapor phase method, the reaction liquid after the esterification reaction of methacrylic acid and methanol usually has a methanol concentration of about 40 to 60% by weight. It is also a high-concentration methanol solution. To separate MMA from such a solution, it becomes difficult to adopt the above method. That is, a large amount of water is required to extract high-concentration methanol in the reaction solution, and as a result,
A great deal of heat energy is required when recovering methanol from the aqueous methanol solution that is the extract.

In addition to the method described above, a method in which the reaction solution is directly distilled to separate and obtain MMA can be considered. However, in this case, since MMA and methanol are azeotropically distilled, it is difficult to separate them simply by an operation by distillation. Further, a method of destroying these azeotropes by adding a solvent to the reaction solution and performing distillation is also conceivable, but in this case as well, it is necessary to add a large amount of solvent, and the heat energy required for distillation and Generally, it is difficult to adopt the above method.

Therefore, in the present invention, MMA, methanol,
When separating MMA from a solution containing water and water,
As described above, it is an object of the present invention to provide a method for a solution having a high concentration of methanol, which does not require a large amount of heat energy and can efficiently separate MMA in a high yield.

[0007]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in order to achieve the above object, the MMA was separated from a solution having a high concentration of methanol by using a specific organic solvent. It was found that it is a particularly effective method to perform extraction and then subject the extract to a distillation operation, and completed the present invention.

That is, the present invention uses 30% by weight of methanol.
The boiling point of a solution containing the above and MMA and water is 1
This is a method for extracting and separating MMA, which comprises contacting an aliphatic saturated hydrocarbon at 05 to 300 ° C. to extract MMA, and then separating MMA by distillation.

According to the present invention, substantially only MMA,
It is possible to extract into an aliphatic saturated hydrocarbon that is an extractant, and since the extractant is hardly distributed to the raffinate side, there is an advantage that the loss of the extractant is small. In particular, when an aliphatic saturated hydrocarbon having a relatively high boiling point is used as the extractant, it is possible to reduce the distribution of the extractant to the raffinate side.

In the method of the present invention, there is no particular limitation on the concentrations of MMA, methanol, and water in the solution from the viewpoint of MMA extraction with an aliphatic saturated hydrocarbon, and in general, a wide range of them may be used. You can However,
In the case of a solution having an extremely low water concentration, methanol easily migrates to the extractant side, and the superiority of extraction with an aliphatic saturated hydrocarbon, and further, considering the distillation operation after the extraction operation, Generally, a solution containing methanol in the range of 30 to 70% by weight, MMA in the range of 5% by weight or more, and water in the range of 10% by weight or more is desirable. When the amount of methanol in the solution is less than 30% by weight, it is generally preferable to adopt a conventional method of extracting methanol with water or another method. Further, in the present invention, the components in the solution are not limited to MMA, methanol, and water, and methacrylic acid, methacrylamide, and the like may be contained in addition to these components.

As the solution having the above-mentioned desirable concentration range, for example, MMA obtained by synthesizing methacrylic acid by dehydration hydration reaction of α-hydroxyisobutyric acid amide and esterifying this with methanol in a gas phase The reaction liquid containing can be mentioned.

In the method of the present invention, an aliphatic saturated hydrocarbon having a boiling point of 105 to 300 ° C., more preferably 120 to 250 ° C. is used as the extractant. If the boiling point of MMA is higher than the boiling point of MMA and lower than 105 ° C, it is possible to extract MMA.
Since the boiling point of A is close to 100 ° C., it becomes difficult to separate MMA from the extract. Further, when the one having a boiling point of higher than 300 ° C. is used, it takes a long time until the two layers are separated in the extraction operation, which is not preferable.

The saturated aliphatic hydrocarbons in the above range which can be used in the method of the present invention include n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n- Examples include tetradecane, n-pentadecane, n-hexadecane, and isomers of these aliphatic saturated hydrocarbons. These can be used alone or in a mixture of two or more kinds. Also,
Some mixed solvents of saturated aliphatic hydrocarbons are generally commercially available, but those having a boiling point in the above range can be used. For example, the starting point is 179
℃, the end point of 212 ℃, such as Soruzol 71 (registered trademark; Shell Japan Co., Ltd.), which is a mixed solvent of aliphatic saturated hydrocarbons having a side chain distilled, should be sufficiently used in the method of the present invention. You can

The amount of the extractant used in the method of the present invention is
Although it is appropriately selected depending on the concentrations of MMA and methanol in the solution, it is usually used in the range of 0.5 to 2 parts by weight of the extractant with respect to 1 part by weight of the solution. If it is less than 0.5 parts by weight, it may be difficult to extract MMA efficiently, and if it exceeds 2 parts by weight, a large amount of heat energy is required for separating MMA after extraction. It is not preferable because it will come.

The temperature for extraction is not particularly limited and can be in a wide range. Generally, room temperature to 70 ° C
It can be performed with a certain degree, and a good effect can be obtained.

By the way, using an aliphatic saturated hydrocarbon, M
When MA is extracted, generally, n-hexane having a lower boiling point than MMA is used as an extractant, which has a larger extraction capacity. However, when the concentration of methanol in the solution is high, a large amount of these extractants is required. For example, FIG. 1 shows an example of a process flow when an extractant having a boiling point lower than that of MMA is used. That is, in FIG. 1, 1 is a solution containing MMA, methanol, and water, which is sent to the extraction tower 3. Reference numeral 2 is an extractant, which is fed into the extraction tower 3 and causes the two liquids to come into contact with each other in the extraction tower 3 for extraction. Then, the extraction residual liquid 4 from the bottom of the extraction tower 3 is sent to the methanol recovery tower 6, where the methanol 7 is recovered and the water 8 is discharged. On the other hand, the extract liquid 5 from the top of the extraction tower 3 is sent to the extractant recovery tower 9, and the extractant 10 is recovered from the top of the extractor 10 and sent to 2 for reuse.
MMA11 is obtained from the bottom of the extractant recovery tower 9. In the actual production of MMA, the reaction liquid contains low-boiling point impurities and high-boiling point impurities, so that in order to remove them, before and after the extractant recovery column 9, a recovery column, a rectification column, etc. MMA purification will be performed by installing auxiliary equipment. In this method, that is, in the process in which an extractant having a lower boiling point than MMA is used, when the extractant and MMA are separated in the extractant recovery column 9, the extractant generally contains as much MMA as possible. It is necessary to increase the reflux ratio in order to prevent it from happening. Therefore, a large amount of energy is required because a large amount of latent heat is used.

In contrast to the above method, a process flow of one embodiment of the present invention, which is a method of using an aliphatic saturated hydrocarbon having a boiling point higher than that of MMA as an extractant, is shown in FIG. The flow and operation in the extraction tower 3 and the methanol recovery tower 6 are the same as the contents of FIG. 1 described above. However, in the method of the present invention, in the extractant recovery tower 9, the extractant 13 is recovered from the tower bottom and recycled to 2. Also, M
MA12 can be obtained from the top of the tower. Even in this case, since the low boiling point impurities and the high boiling point impurities are contained in the reaction liquid in the actual production of MMA,
In order to remove them, auxiliary equipment such as a recovery tower and a rectification tower is provided before and after the extractant recovery tower 9 to purify MMA. In the case of this method, since the MMA having a concentration lower than that of the extractant is distilled in the extractant recovery tower 9, latent heat of the extractant is not required. Therefore, the method of the present invention has an advantage that the thermal energy required for separating MMA and the extractant can be significantly reduced.

In the method of the present invention, the extract obtained after extracting MMA in the solution is obtained as the upper layer liquid as described above. MMA can be separated by separating this liquid and subjecting it to distillation. Distillation is generally carried out under reduced pressure with a polymerization inhibitor added to prevent polymerization of MMA. Further, the solution of methanol and water contained in the solution is obtained as a lower layer liquid in the extraction operation. Methanol is recovered from this solution by subjecting it to a conventional distillation operation.

[0019]

EXAMPLES The present invention will now be described in more detail with reference to examples. In the following, all "%" are based on weight, and the components in the extract and the raffinate after the extraction operation were analyzed by gas chromatography. In addition, "MMA
The “extraction rate” and the “migration rate” are values calculated by the following formula.

[Formula 1] MMA extraction rate (%) = (weight of extracted MMA / weight of MMA in solution) × 100

[Formula 2] Transfer rate (%) = (weight of target component in extract or raffinate / weight of target component in solution) × 100

Example 1 To a separating funnel (volume: 200 ml), 50 g of a solution containing 18.8% MMA, 54.9% methanol and 26.3% water, and 50 g of n-decane (boiling point 174 ° C.) as an extractant were added, After stirring for 5 minutes at room temperature, the solution was allowed to stand for 10 minutes to separate the solution into two layers. The upper layer extract and the lower layer raffinate were separated and analyzed. As a result, the extraction rate of MMA was 65%, and the migration rate of methanol on the extract side was 1.5%. The transfer rate of n-decane to the raffinate side was less than 0.1%.

Examples 2-6 In Example 1, n-octane (boiling point 126
℃), n-dodecane (boiling point 216 ℃), n-tridecane (boiling point)
234 ° C), n-tetradecane (boiling point 254 ° C), or Shellzol 71 (registered trademark; Shell Japan Co., Ltd. [mixed solvent of aliphatic saturated hydrocarbon having side chain, initial boiling point 1
Distilled at 79 ° C and end point of 212 ° C. ]) Was used, and the same procedure was performed. The results are shown in Table 1.

Comparative Examples 1 and 2 In Example 1, n-hexane (boiling point 69
C.) or p-xylene (boiling point 138.degree. C.) was used. The results are shown in Table 1.

[0023]

[Table 1] Note 1: The boiling point of Shellzol 71 is 179-212 ° C.

Example 7 In a continuous extraction column having 8 theoretical plates, a mixed solution having the same composition as the solution used in Example 1 (MMA 18.8%, methanol
54.9%, water 26.3%) 40 g / min, and Shersol 71 (the same as used in Example 6) as an extractant 60 g
Countercurrent extraction was carried out by continuously supplying at a flow rate of 1 / min. The extraction rate of MMA in this continuous extraction was 95%, the transfer rate of methanol to the extract side was 2.9%, and the transfer rate of the extractant to the raffinate side was 0.1% or less. The obtained extract is
A 10-stage extractant recovery tower with a top temperature of 45 ° C and a top pressure of 60
Distillation was carried out by adding 0.2% of hydroquinone under the conditions of Torr, the bottom temperature of 100 ° C., and the bottom pressure of 100 Torr to obtain a liquid containing 97% of MMA. This liquid was further collected in a low boiling point recovery tower with 25 plates, with a top temperature of 70 ° C, a top pressure of 350 Torr, and a bottom temperature.
When methanol was removed at 80 ° C. and a column bottom pressure of 400 Torr, MMA with a yield of 90% and a purity of 99.8% was obtained from the column bottom.

Example 8 In the same extraction tower as in Example 7, MMA 14.9%, methanol 4
Countercurrent extraction was carried out by supplying 50 g / min of a mixed solution of 3.5% and 41.6% of water and 40 g / min of Shellzol 71 (the same as that used in Example 6) as an extractant. The extraction rate of MMA in this continuous extraction was 98%, the transfer rate of methanol to the extract side was 2%, and the transfer rate of the extractant to the raffinate side was 0.1% or less. When the obtained extract was distilled under the same conditions as in Example 7, MMA with a yield of 92% and a purity of 99.8% was obtained from the bottom of the column.

[0026]

EFFECTS OF THE INVENTION According to the method of the present invention, M is more efficient than a solution containing high concentration methanol and containing MMA and water.
It is possible to separate the MA. That is, in Examples 1 to 8 carried out in the method of the present invention, the migration of methanol into the extract was 3% or less, and the migration of the extractant into the raffinate was 0.2% or less. Very few. Therefore, high-purity MMA can be separated, and the extractant can be sufficiently used repeatedly. Furthermore, the heat energy used at that time is also small.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an extraction method when an extractant having a lower boiling point than MMA is used.

FIG. 2 is a specific example illustrating the extraction method of the present invention in which an aliphatic saturated hydrocarbon having a boiling point higher than that of MMA is used as an extractant.

[Explanation of Codes] 1 Solution containing MMA, methanol and water 2 Extractant 3 Extraction tower 4 Extraction liquid 5 Extraction liquid 6 Methanol recovery tower 7 Methanol 8 Water 9 Extractant recovery tower 10 Extractant 11 MMA 12 MMA 13 Extractant

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshiyuki Nakajima 1900 Togo, Mobara-shi, Chiba Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A solution containing 30% by weight or more of methanol, and containing methyl methacrylate and water, having a boiling point of 105 to 30.
A method for extracting and separating methyl methacrylate, which comprises contacting with an aliphatic saturated hydrocarbon at 0 ° C to extract methyl methacrylate, and then separating methyl methacrylate by distillation.