TW201315715A - Purification method of methyl methacrylate - Google Patents

Abstract

This invention provides a purification method of methyl methacrylate (MMA), comprising: (1) feeding a mixture containing MMA, water and methanol as the extraction residue phase feed from the bottom side of an extraction tower; (2) feeding the extractant water as the extraction phase fed from the top side of the extraction tower; (3) enabling countercurrent extraction of the extraction residue phase and the extraction phase in the extraction tower; (4) obtaining the extraction residue phase discharge mainly comprising MMA from the top of the extraction tower; and (5) obtaining the extraction phase discharge mainly comprising water and methanol from the bottom of the extraction tower.

Description

Method for purifying methyl methacrylate

The invention relates to a method for purifying methyl ethyl methacrylate (MMA), which can be applied to purify the dehydration reaction of methyl 2-hydroxyisobutyrate (MAHIB). Crude MMA.

MMA is produced by MAHIB in the presence of molecular sieves via a dehydration reaction. In this dehydration reaction, in addition to the main product MMA, there is the presence of by-product water, and MMA is easily hydrolyzed in the presence of water, which will hydrolyze MMA to form Methacrylic Acid. MAA) with methanol. In order to avoid the occurrence of the hydrolysis reaction, an appropriate amount of methanol is added during the reaction to suppress the progress of the hydrolysis reaction by using the Le Chatelier principle. Therefore, in the crude MMA after the dehydration reaction, in addition to the MMA formed by the dehydration reaction, water and unreacted MAHIB, methanol added by the additional hydrolysis reaction and the MAA produced by the hydrolysis reaction are contained. Among them, MAHIB and MAA are heavy components, which can be eliminated by simple distillation; while light components MMA, methanol and water form low azeotropes with each other, which cannot be separated and purified by ordinary distillation.

Previous literatures have revealed some methods for purifying MMA from crude MMA obtained by esterification of MAA with methanol, such as: (1) using water as an extractant for methanol, by extractive distillation from crude MMA to methanol Separation (Japanese Patent Publication No. 54-024812); (2) Extraction and separation of MMA from crude MMA using water and a hydrocarbon as an extractant (Japanese Patent Publication No. 54-024814); (3) Hydrocarbon use Forming a lower azeotrope with methanol, and separating methanol from crude MMA by azeotropic distillation (Japanese Patent Publication No. 57-009740, No. 58-180457, and No. 58-203940; U.S. Patent No. 5028735 No. 5435892). However, no one has proposed a method of purifying MMA in crude MMA obtained by the dehydration reaction of MAHIB.

In view of this, it is necessary to develop a method for purifying MMA from crude MMA obtained by the dehydration reaction of MAHIB.

The object of the present invention is to provide a method for purifying MMA from crude MMA obtained by dehydration reaction of MAHIB, which comprises MMA, water and methanol, and contains MAHIB, MAA and formamide (FA). High-boiling impurities of at least one component, wherein the heavy components MAHIB and MAA can be removed by simple general distillation; and the light components MMA, water and methanol are separated by single-agent extraction to purify MMA.

In order to achieve the above object, the method for purifying methyl methacrylate of the present invention comprises purifying MMA from a mixture containing MMA, water and methanol, which comprises the steps of:

(1) feeding a mixture containing MMA, water and methanol as a residual phase from the bottom side of the extraction column;

(2) feeding the extractant water as the extract phase from the top side of the extraction column;

(3) the residual phase and the extract phase are subjected to countercurrent extraction in the extraction column;

(4) extracting the top of the column to obtain the extract of the remaining phase, which comprises MMA and a very small amount of water and methanol;

(5) Extracting the bottom of the column to obtain an extract phase discharge, which mainly comprises water and methanol.

Preferably, the amount of the extractant water is at least equal to 1.3 times the weight of the methanol in the extract and 1.5 times the weight of the MMA in the extract, but not more than 7.3 times the weight of the methanol in the extract and 8.2 times the extract. The weight of the MMA.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the flow chart of the purification plant shown in FIG. 1, but it is merely illustrative and not intended to limit the scope of the present invention.

As shown in Fig. 1, the extract phase containing the main component MMA, water and methanol is introduced into the extraction column 1 from the line 3, and the extract phase feed water is introduced into the extraction column 1 from the line 2. The residual phase feed and the extract phase feed are subjected to countercurrent extraction in the extraction column 1 at normal temperature and normal pressure.

In the extraction column 1, the MMA-rich and a very small amount of the methanol and water supernatant are discharged via the line 4, and the high-purity MMA can be recovered later by a general rectification or other purification method.

On the other hand, in the extraction column 1, water-soluble, methanol-rich, and a very small amount of the underlayer extract of MMA are taken out through the line 5, and then water and methanol are recovered through general distillation.

Table 1 shows the flow and composition of the material delivered via the main line.

1. . . Extraction tower

2. . . Pipeline

3. . . Pipeline

4. . . Pipeline

5. . . Pipeline

1 is a flow chart of a purification plant used in an embodiment of the present invention.

1. . . Extraction tower

2. . . Pipeline

3. . . Pipeline

4. . . Pipeline

5. . . Pipeline

Claims (2)

A method for purifying methyl methacrylate (MMA) by purifying MMA from a mixture containing MMA, water and methanol, comprising the steps of: (1) treating a mixture containing MMA, water and methanol as a residual phase The feed is fed from the bottom side of the extraction column; (2) the extractant water is used as the feed of the extract phase from the top side of the extraction column; (3) the residual phase and the extract phase are countercurrent in the extraction column Extraction; (4) extracting the top of the column to obtain a residual phase discharge, which mainly comprises MMA; and (5) extracting the bottom of the column to obtain an extract phase discharge, which mainly comprises water and methanol. The purification method of claim 1, wherein the extractant water is at least equal to 1.3 times the weight of the methanol in the extract and 1.5 times the weight of the methyl methacrylate in the extract, but not more than 7.3 times. The weight of methanol in the extract is 8.2 times the weight of methyl methacrylate in the extract.