JPH0662490B2 - Separation of oil and water layers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention accelerates the separation rate between an oil layer and an aqueous layer or prevents the formation of an emulsion when methacrylic acid is extracted from an aqueous methacrylic acid solution with an organic solvent. And a method for facilitating the extraction operation.

(Prior Art) When extracting methacrylic acid from a conventional aqueous solution containing methacrylic acid with a solvent, the separation of the oil layer and the aqueous layer is poor, and when it is remarkable, an emulsion may be formed and the extraction tower may become inoperable. .

As a general measure to prevent this, (1) addition of salt (Japanese Patent Publication No. 49-36209), (2) addition of cationic surfactant (JP-A-54-66617), (3) increase in operating temperature, etc. There is.

(Problems to be Solved by the Invention) However, these methods also have disadvantages and do not provide sufficiently satisfactory results. Regarding the method of salt addition, the addition amount is large (0.1 to 5%), and at the same time, polymerization loss is likely to occur. The addition of the cationic surfactant tends to hinder stable operation because the precipitated solid matter adheres to the inside of the tower.
Increasing the operating temperature tends to increase the mutual solubility between the two layers and consequently lower the extraction performance. In any case, there are many problems and no fundamental solution has been reached.

(Means for Solving Problems) As a result of intensive investigations by the present inventors in order to solve such problems, as a result, an oil layer and an aqueous layer were obtained by adding a fatty acid ester-based or polyalkylene glycol-based defoaming agent during extraction. The present invention has been completed by finding that it is possible to speed up the separation rate from or to prevent emulsion formation.

The present invention adds a fatty acid ester-based or polyalkylene glycol-based defoaming agent when extracting methacrylic acid from an aqueous methacrylic acid solution obtained by vapor-phase catalytic oxidation of a compound having 4 carbon atoms using an organic solvent. The method for separating an oil layer and an aqueous layer is characterized by adding the antifoaming agent to increase the separation speed between the oil layer and the aqueous layer or prevent the formation of an emulsion.

A polymer produced from methacrolein and / or methacrylic acid is dissolved in an aqueous solution of methacrylic acid obtained by a gas phase catalytic oxidation reaction of isobutylene, t-butanol, isobutyraldehyde or methacrolein. The amount naturally varies depending on the process, but is usually 0.1 to 5% by weight based on methacrylic acid. In order to separate methacrylic acid from this methacrylic acid aqueous solution, extraction with an organic solvent is usually performed. At this time, as the extraction of methacrylic acid progresses, the polymer that cannot be completely dissolved in the water layer and the oil layer is deposited at the interface between the two layers and other places. The deposited polymer (hereinafter referred to as scum) has an appropriate tackiness, and therefore, when the oil layer and the water layer are completely in contact with each other during the extraction operation, the separation of the two layers may be hindered or an emulsion may be formed in some cases. To do. Therefore, as a result of various experimental studies to solve this problem, the present inventors have found that an oil layer and a water layer can be formed by adding a fatty acid ester-based or polyalkylene glycol-based defoaming agent during the extraction operation of methacrylic acid. It was possible to speed up the separation rate of or to prevent the formation of emulsions.

As the organic solvent used in the present invention, any known organic solvent can be used and is not particularly limited. For example, hexane, heptane, octane, ligroin, cyclohexane, benzene, toluene, xylene and other aliphatic, alicyclic, aromatic hydrocarbons, ethyl acetate, isopropyl acetate,
Esters, ketones such as butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, diisopropyl ether,
Ether or the like can be used.

As the polyalkylene glycol antifoaming agent used in the present invention, Nissan Dishome CC-118 (NOF CORPORATION, average molecular weight 1800, molecular weight distribution 1200 to 3)
000), PEG 400 (average molecular weight 400) and the like, but are not limited thereto.

The addition amount of the defoaming agent depends on the properties of the methacrylic acid aqueous solution, but it is preferably 5 to 500 ppm, and particularly preferably 10 to 100 ppm, in the methacrylic acid aqueous solution.

The addition method is not particularly limited, and may be added at any place to the methacrylic acid aqueous solution of the previous step fed into the extraction tower, or may be added directly to the extraction tower.

(Example) Next, the present invention will be specifically described with reference to examples.

Example 1 The following experiment was conducted using an aqueous methacrylic acid solution obtained by subjecting methacrolein to gas phase catalytic oxidation using a phosphorus-molybdenum-based oxidation catalyst.

The composition of this aqueous solution is as follows.

Methacrylic acid 26 wt% Acetic acid 5 wt% Non-volatile components such as polymer 0.3 wt% Water, other 68.7 wt% Take a 100 ml methacrylic aqueous solution in a 500 ml separating funnel, and add the defoamer in the amount shown in Table 1 to it. To this, 100 g of heptane was added as a solvent, vigorously stirred for 30 seconds, and the time from the standing to the separation of the two layers was measured.

For comparison, a silicone antifoam was also tested.
The results are shown in Table 1, and the effect of the defoaming agent of the present invention was confirmed.

Example 2 With respect to the same aqueous methacrylic acid solution as in Example 1, Nissan Dishome CC-118 was added as an antifoaming agent, and Table 2
An experiment was conducted in the same manner as in Example 1 using the organic solvent shown in.

The results are shown in Table 2. The effect of the defoamer could be regarded as almost independent of the type of organic solvent.

(Effects of the Invention) According to the present invention, when methacrylic acid is extracted from an aqueous methacrylic acid solution using an organic solvent, the separation rate between the oil layer and the aqueous layer is increased, and the formation of an emulsion can be prevented.

Claims (1)

[Claims] 1. When a methacrylic acid is extracted from an aqueous methacrylic acid solution obtained by vapor-phase catalytic oxidation of a compound having 4 carbon atoms using an organic solvent, a polyalkylene glycol antifoaming agent is used in the aqueous methacrylic acid solution. The method for separating an oil layer and an aqueous layer is characterized by adding 5 to 500 ppm.