JPH01125353A - Production of methacrylamide crystals - Google Patents

Abstract

PURPOSE:To obtain methacrylamide crystals which is used in coating, adhesive, as a photosetting compound, fiber modifier or resin processor, by crystallizing out the crystals from the methacrylamide aqueous solution formed by using a catalyst from a living body without excessive consumption of energy. CONSTITUTION:The hydration reaction of methacrylonitrile is carried out using a living body catalyst such as Rhodococcus AK32 strain, to give a methacrylamide aqueous solution. Then, the reaction product is combined with a solvent which is capable of cooling other substances such as n-pentane to separate the methacrylamide crystals from the slurry. The mother liquor is recycled to the hydration reaction, while the solvent phase is given cooling ability again. The cooling heat energy from the aqueous methacrylamide is utilized to remove the heat of the hydration reaction. Further, the selection of the solvent of low melting point enables a large temperature difference from the cooling medium whereby the heat transfer area can be minimized, resulting in the size reduction of the facility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a novel production method for obtaining methacrylamide from an aqueous methacrylamide solution by cooling crystallization.

Methacrylamide is used in paints, adhesives, photo-crosslinkable compounds, fiber improvement, paper strength enhancement, resin processing, etc. due to its properties such as moderate hydrophilicity, lipophilicity, heat resistance, and crosslinkability. , and is expected to be used for new applications. According to the present invention, methacrylamide crystals can be produced industrially and advantageously.

(Prior art) Generally, in order to recover crystals from an aqueous solution of a certain substance, first, the water is evaporated to concentrate the aqueous solution, and then the aqueous solution is cooled using a normal refrigerant at a temperature higher than the freezing point of the aqueous solution. The crystals are separated from the slurry liquid and collected. Of course, even when methacryl nitrile is hydrated using a biocatalyst to produce an aqueous methacrylamide solution, it is possible to separate the crystals by the above-mentioned general method. By the way, regarding a method for producing methacrylamide using a biocatalyst, Japanese Patent Publication No. 56-38118 describes a method for producing methacrylamide in an aqueous medium.
A method of hydration in the temperature range from the freezing point to 15°C is also disclosed in Japanese Patent Application Laid-open No. 107792/1983 by the present inventor, in which the reaction temperature in the reaction solution is set in the range from the freezing point to 20°C, and the methacrylate produced is A method using reactive crystallization is disclosed in which the remaining reaction solution from which the amide crystals have been separated is recycled to the reactor.

(Problems to be Solved by the Invention) In order to separate crystals by a general method from an aqueous methacrylamide solution obtained using a biocatalyst, the reaction temperature with the biocatalyst is usually between freezing point and 20°C. Since the humidity is low, a large amount of energy must be used to evaporate water and concentrate the aqueous solution, and there remains the drawback that methacrylamide is easily polymerized by heating. Fortunately, even when a saturated aqueous methacrylamide solution is obtained using a biocatalyst, in order to cool it using the normal surface cooling method, the crystallization humidity is Inevitably, the temperature is low. On the other hand, since the freezing point of an aqueous methacrylamide solution is approximately -2°C, it is impossible to lower the refrigerant temperature below -2°C. The heat transfer area for heat removal became yellowish, and crystals adhered to the wall surface of the crystallization tank, resulting in problems with operability.

(Means for Solving the Problems) The present inventor has developed a method for producing methacrylamide crystals from an aqueous methacrylamide solution obtained using a biocatalyst, in which the heat removal heat transfer area of the crystallization tank is large. As a result of intensive research aimed at solving the industrial problem that it is difficult to recover crystals at low energy, we found that after cooling a hydrophobic organic solvent with a low freezing point, we mixed it with an aqueous methacrylamide solution to produce methacrylamide. The method of cooling and crystallizing organic solvents with a low freezing point is cooled with a refrigerant, which allows for a large temperature difference, making it possible to reduce the heat transfer area of the heat exchanger attached to the crystallization tank. In addition, the cold heat generated by cooling the methacrylamide aqueous solution can be used to remove the heat of hydration reaction of methacrylnitrile, which is an extremely effective method with low energy consumption in terms of the overall process. They discovered this and completed the present invention.

That is, the present invention provides a method for producing methacrylamide crystals by cooling crystallization from an aqueous methacrylamide solution obtained by a hydration reaction of methacrylnitrile using a biocatalyst. There is a method for producing methacrylamide crystals, which comprises separating the methacrylamide crystals from the resulting methacrylamide slurry and recycling the mother liquor in the hydration reaction. In addition, the present invention provides a method for producing methacrylamide crystals by cooling crystallization from an aqueous methacrylamide solution obtained by a hydration reaction of methacrylnitrile using a biocatalyst. After mixing, the methacrylamide crystals are separated from the methacrylamide slurry obtained by two-phase separation, and the Bj liquid is recycled to the hydration reaction, and the organic solvent phase is
This is a method for producing methacrylamide crystals, which is characterized in that the crystals are recycled by providing cooling capacity again.

The method of the present invention will be explained in detail below. As a biocatalyst that can be used in the present invention, any one of microorganisms and enzymes can be used as long as it has the ability to hydrate methacryloni-1-lyl and produce methacrylamide. Alternatively, it may be fixed. Suitable microorganisms include, for example, Rhodococcus AK32 described in JP-A-62-91189.
strain (Feikoken Bibori No. 1046) and 33 strains of Δ (
Examples include Biken Bacteria Serial No. 1047).

The saturated fA g of methacrylamide in the methacrylamide aqueous solution obtained using these biocatalysts varies depending on the reaction humidity, but for example, at 10°C, it is 14.2% by weight,
At 15°C, it is 16.5% by weight, and at 20°C, it is 19% by weight. Of course, it is advantageous that the aqueous methacrylamide solution has a saturated concentration when recovering crystals by cooling crystallization, but it is not an essential condition.

Regarding the physical properties of the organic solvent used in the present invention, the solubility of water and methacrylamide in the organic solvent is preferably 1.0% by weight or less, more preferably 0.2% by weight or less. This is because it can prevent crystals from adhering to heat exchangers, etc. when re-applying cooling capacity to the organic solvent that has separated into two phases after mixing the methacrylamide aqueous solution and the organic solvent. preferable. Further, the solubility of the organic solvent in the methacrylamide aqueous solution is preferably 1.0% by weight or less, more preferably 0.2% by weight.
The following is desirable.

Furthermore, as a physical property of the organic solvent, its freezing point is -20°C.
It is preferably below, more preferably -40°C or below. This is particularly important in order to minimize the temperature difference when cooling an organic solvent with a refrigerant.

Examples of organic solvents exhibiting the above physical properties include aliphatic hydrocarbons such as n-pentane, 2-medylpentane, n-hexane, 2-medylhexane, 3-methylhexane, n-heptane, n-octane, and n-nopune; Examples include ethers such as di-n-butyl ether, di-isobutyl ether, and di-n-pentyl ether.

Next, as for the crystallization method in which an aqueous methacrylamide solution and a hydrophobic organic solvent having a cooling capacity are mixed, either a batch method or a continuous method can be employed. In a batch type, mixing, sedimentation, and extraction are generally carried out intermittently in a tank, while in a continuous type, mixing is carried out continuously using two layers: a mixing tank and a sedimentation and extraction tank. It is. The organic solvent phase that has separated into two phases is given cooling capacity again and recycled. On the other hand, the methacrylamide slurry liquid is subjected to ordinary solid-liquid separation such as filtration or centrifugation to separate methacrylamide crystals, and the mother liquor is recycled to the IC reactor using a biocatalyst. In this way, the methacrylamide reaction and recovery system consisting of reaction, crystallization, and solid-liquid separation is completed, and an industrial production process is constructed.

The type of heat exchanger that provides cooling ability to the organic solvent is not particularly limited, and may be a tubular heat exchanger or a plate heat exchanger. The type of refrigerator may be selected depending on the desired heat mark level and refrigerating capacity, but a turbo type or absorption command refrigerator is preferable.

If a small amount of water or methacrylamide dissolved in the organic solvent gets onto the heat transfer surface of the heat exchanger and lowers the overall heat transfer coefficient, you can wash it with water and circulate the organic solvent. Once dried, the heat exchange ability can be easily restored.

(Effects of the Invention) According to the present invention, methacrylamide crystals can be obtained from an aqueous methacrylamide solution obtained using a biocatalyst without consuming extra energy. In particular, the cold heat used to crystallize methacrylamide is used to remove the reaction heat because the mother liquor is cycled into the reactor.

Additionally, since an organic solvent with a low freezing point is used, a large temperature difference between the refrigerant and the refrigerant can be maintained when providing cooling capacity, which reduces the heat transfer area of the heat exchanger and allows equipment to be made more compact. As described above, the present invention provides an industrially extremely advantageous method for producing methacrylamide crystals.

(Example) Next, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited to the Examples.

Example 1 Glucose 1%, meat extract 0.2%, peptone 0.2%
, isobutyronitrile 0.25%, salt 0.1%, potassium phosphate 0.1%, magnesium sulfate 0.05%
, ferrous sulfate 0.005%, manganese sulfate 0.005%
, AK cultured aerobically in a medium (pH 7.0) containing 0.1% ammonium sulfate and 0.1% potassium nitrate.
30 parts of washed bacterial cells of strain 32m (1185% dry bacterial cells), 9 parts of acrylamide, 1 part of N,N'-methylenebisacrylamide, and 48 parts of physiological saline were mixed to form a uniform suspension. To this were added 6 parts of a 5% β-dimethylaminopropionitrile aqueous solution and 6 parts of a 2.5% potassium belloxonisulfate aqueous solution, and the mixture was kept at 0°C for 30 minutes to polymerize.

The thus obtained lump-like bacterial cell-containing gel was molded into 2 to 3 cubes and thoroughly washed with physiological saline to obtain 100 parts of immobilized bacterial cells.

The reactor consisted of a reactor consisting of three double-tube glass columns with an inner diameter of 8 mm and a length of 1 m, a solid-liquid separator using a double-tube jacketed crystallization tank and a glass filter. The reactor was filled with 90tj of the above immobilized bacterial cells, and 2j
130 g of methacrylonitrile and 840 g of physiological saline were placed in a 1-volume glass bottle, and the aqueous phase was circulated at 130 g/hr for 2 days while controlling the reactor internal temperature at 17°C. As a result, 17% of methacrylamide was dissolved at 17°C. 970 g of 0% by weight aqueous solution were obtained. This methacrylamide aqueous solution was transferred to a crystallization tank with a 3" double tube jacket, and then
Add n-hexane 1420y at 0°C and mix well for 10 minutes at 0°C, then leave the resulting slurry for 10 minutes to allow the crystals to settle sufficiently, then separate the n-hexane phase and concentrate The slurry liquid was drawn out, and crystals were separated using a glass filter.

1? When the crystals were thoroughly air-dried and weighed, the result was 165
It was g. When this crystal was dissolved and subjected to purity analysis using a gas chromatograph, almost no n-hexadi was detected, and it was found to be methacrylamide with almost 100% purity. On the other hand, a predetermined amount of methacrylonitrile and water were added to the mother liquor and recycled to the reactor. The concentrations of methacrylamide and water dissolved in n-hexane were 0.015% by weight and 0.068% by weight, respectively.

Examples 2 to 7, Comparative Examples 1 to 2 Methacrylonitrile 809.0.
Methacrylamide 14°C was obtained in the same manner as in Example 1, except that 05M phosphate buffer (pH 7.5>645g was charged and the reaction was carried out while controlling the reactor internal temperature to 10°C. 725 g of aqueous solution of % by weight,
3j! After transferring to a crystallization tank with double tube jacket, -20℃
640 g of various organic solvents shown in Table 1, which had been cooled to 50%, were added. Thereafter, the slurry was thoroughly mixed for 30 minutes while controlling the temperature at 0°C, and the resulting slurry was allowed to stand for 10 minutes to allow the crystals to settle sufficiently, and the organic solvent phase was separated.
Methacrylamide crystals were obtained in the same manner as above, and the mother liquor was recycled. Dissolve this crystal,
When pure trace analysis was performed using a gas chromatograph, almost no organic solvent was detected, and it was found to be methacrylamide with almost 100% purity.

The concentrations of methacrylamide and water dissolved in the organic solvent, and the concentration of the organic solvent dissolved in the aqueous solution are shown in Table 1.
It was shown to.

Table 1-151 Example 8 90 g of immobilized bacterial cells obtained in the same manner as in Example 1,
After filling the same reactor as in Example 1, 6.6 g of methacrylonitrile was added to 100 g/Hr of a 10.0% by weight aqueous solution of methacrylamide recycled from the solid-liquid separator.
/Hr and 1.8 g/Hr of water were added to the reactor and the reaction was carried out at 17°C. Then 10
0m! ! Pour the reaction solution into a mixing tank with a double tube jacket.
．． 4 g/llr.

N-hexane cooled to −20° C. was fed at a rate of 158 g/Hr, and while thoroughly mixed, the resulting slurry liquid was continuously extracted into a 500 d double-tube jacketed settling tank. The n-hexane phase and slurry aqueous solution phase, which were separated into two phases at 0° C., were each extracted for the next step every hour. The aqueous slurry phase was filtered using a glass filter as a solid-liquid separator to obtain methacrylamide crystals at 8.4 g/Hr.

On the other hand, the filtration mother liquor was fed to the reactor at 100 g/Hr, and the n-hexane phase was cooled again to -20° C. and then recycled to the mixing tank at 158 s/Hr. This experiment was carried out for 5 hours under steady state conditions and 427 methacrylamide crystals were obtained.

Claims (10)

[Claims] (1) When producing methacrylamide crystals by cooling crystallization from an aqueous methacrylamide solution obtained by a hydration reaction of methacrylonitrile using a biocatalyst, the aqueous methacrylamide solution is mixed with an organic solvent having cooling ability. A method for producing methacrylamide crystals, which comprises separating the methacrylamide crystals from the resulting methacrylamide slurry, and recycling the mother liquor for a hydration reaction. (2) The method according to claim 1, wherein the concentration of the methacrylamide aqueous solution is a saturated concentration. (3) The method according to claim 1, wherein the solubility of water and methacrylamide in the organic solvent is 1.0% by weight or less. (4) The method according to claim 1, wherein the organic solvent has a freezing point of -20°C or lower. (5) The method according to claim 1, wherein the organic solvent is an aliphatic hydrocarbon or an ether. (6) When producing methacrylamide crystals by cooling crystallization from an aqueous methacrylamide solution obtained by a hydration reaction of methacrylonitrile using a biocatalyst, the aqueous methacrylamide solution is mixed with an organic solvent having cooling ability. After that, the methacrylamide crystals are separated from the methacrylamide slurry obtained by two-phase separation, and the mother liquor is recycled for the hydration reaction.
A method for producing methacrylamide crystals, characterized in that they are recycled after being given cooling capacity again. (7) The method according to claim 6, wherein the concentration of the methacrylamide aqueous solution is a saturated concentration. (8) The method according to claim 6, wherein the solubility of water and methacrylamide in an organic solvent is 1.0% by weight or less. (9) The method according to claim 6, wherein the organic solvent has a freezing point of -20°C or lower. (10) The method according to claim 6, wherein the organic solvent is an aliphatic hydrocarbon or an ether.