A method for producing high purity acrylic acid from a crude aqueous acrylic acid solution

Abstract

The application discloses a method for preparing high-purity acrylic acid from a crude acrylic acid aqueous solution, and belongs to the technical field of acrylic acid purification. The method extracts the crude acrylic acid aqueous solution by using an extractant composed of isopropyl acetate and benzene or a derivative of benzene (toluene or xylene), so that the extractant is rich in acrylic acid, the types and contents of impurities in the extractant are reduced, and the recovery rate and purity of the acrylic acid are significantly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of acrylic acid purification, and particularly relates to a method for preparing high-purity acrylic acid from a crude aqueous acrylic acid solution. BACKGROUND

[0002] Acrylic acid is an important chemical raw material, and as a monomer of a polymer, it can be used to synthesize thousands of polymers. At present, in the industry, acrylic acid is obtained by using propylene to oxidize in the gas phase under the action of a catalyst, and then using water to cool down to obtain an aqueous acrylic acid solution, and finally purifying the aqueous acrylic acid solution to obtain an acrylic acid product. The mass concentration of acrylic acid in the aqueous acrylic acid solution is between 25% and 50%, and the aqueous acrylic acid solution also contains formaldehyde, acrolein, propionic acid, acetone, maleic acid, acrylic acid dimers, and the like,

[0003] At present, the method for purifying the crude aqueous acrylic acid solution in the industry is an azeotropic method and an extraction method, specifically, toluene is used to azeotrope with water and acetic acid in the crude aqueous acrylic acid solution to separate the water and acetic acid in the aqueous acrylic acid solution. This technology has high energy consumption and still cannot obtain high-purity acrylic acid.

[0004] At present, the extraction of the crude aqueous acrylic acid solution by the extraction method has the following problems:

[0005] 1. The extraction temperature is high, and the extraction is not complete at room temperature, causing great economic loss;

[0006] 2. After extraction, there are still many impurities in the obtained extraction liquid, and high-purity acrylic acid cannot be obtained by using a rectifying tower. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a method for preparing high-purity acrylic acid from a crude aqueous acrylic acid solution, which uses an extractant composed of isopropyl acetate and dimethylbenzene, toluene to extract the crude aqueous acrylic acid solution in an extraction tower, obtains an extraction liquid, and then uses a rectifying tower to rectify the extraction liquid to obtain a high-purity acrylic acid product. The purification process of the present application has low energy consumption and the obtained acrylic acid product has a purity of more than 98%.

[0008] The present application is implemented by using the following technical solutions:

[0009] A method for preparing high-purity acrylic acid from a crude aqueous acrylic acid solution, specifically, using an extractant to extract the crude aqueous acrylic acid solution at room temperature, collecting the organic phase after static stratification to obtain an extraction liquid rich in acrylic acid, and finally passing the extraction liquid into a rectifying tower for rectification to obtain high-purity acrylic acid at the bottom of the rectifying tower;

[0010] The extractant is a mixture of isopropyl acetate and benzene, derivatives of benzene in a volume ratio of 1-6:1-2:0-2, wherein the derivatives of benzene are toluene or dimethylbenzene.

[0011] Preferably, the volume ratio of the extractant to the crude aqueous acrylic acid solution is 0.7-2:1.

[0012] Preferably, the room temperature is 10-20℃.

[0013] Preferably, the extractant contains acrylic acid, extractant and acetic acid.

[0014] Preferably, the purity of the acrylic acid collected after rectification is greater than 98%.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] The present application provides an extractant for purifying an aqueous acrylic acid solution, which is composed of isopropyl acetate and xylene, toluene, which can extract acrylic acid from the aqueous solution, while reducing the types and contents of impurities in the extract phase, and significantly improving the recovery rate of acrylic acid.

[0017] The present application has low energy consumption, is convenient for industrial implementation, and has high economic value. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The figure is a schematic diagram of the structure of the extraction tower of the present application. DETAILED DESCRIPTION

[0019] In order to make the purpose, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Example 1

[0020] A method for preparing high-purity acrylic acid from a crude aqueous acrylic acid solution, the specific steps are as follows:

[0021] The crude aqueous acrylic acid solution (the mass concentration of acrylic acid is 38.9% after detection) and the extractant are respectively introduced into the upper end and the lower end of the extraction tower, wherein the extractant is a mixture of isopropyl acetate and benzene, toluene in a volume ratio of 1.5:1:1;

[0022] The volume ratio of the extractant to the crude aqueous acrylic acid solution in the extraction tower is controlled to be 1.8:1 at the same time.

[0023] The extraction treatment is not more than 50 minutes under room temperature conditions;

[0024] After standing and layering, the upper oil phase, i.e. the extract phase, is collected, and an extract liquid rich in acrylic acid is obtained; the lower aqueous phase is the raffinate phase.

[0025] The extraction liquid is introduced into a rectification tower for rectification, acrylic acid is discharged from the bottom of the rectification tower, and after collection, the purity is detected to be 98.5%, and the acrylic acid recovery rate is 91%. Example 2

[0026] A method for preparing high-purity acrylic acid from a crude aqueous acrylic acid solution, the specific steps are as follows:

[0027] Crude aqueous acrylic acid solution (the mass concentration of acrylic acid is detected to be 38.9%) and extractant are introduced into the upper end and lower end of the extraction tower respectively, wherein the extractant is a mixture of isopropyl acetate and benzene, xylene in a volume ratio of 1:1:2;

[0028] The volume ratio of the extractant to the crude aqueous acrylic acid solution in the extraction tower is controlled to be 0.8:1 at the same time.

[0029] The extraction treatment is not more than 60 minutes under room temperature conditions;

[0030] After standing and layering, the upper oil phase, i.e. the extraction phase, is collected to obtain an extraction liquid rich in acrylic acid; the lower aqueous phase is the raffinate phase.

[0031] The extraction liquid is introduced into a rectification tower for rectification, acrylic acid is discharged from the bottom of the rectification tower, and after collection, the purity is detected to be 98.8%, and the acrylic acid recovery rate is 95%.

[0032] Example 3

[0033] A method for preparing high-purity acrylic acid from a crude aqueous acrylic acid solution, the specific steps are as follows:

[0034] Crude aqueous acrylic acid solution (the mass concentration of acrylic acid is detected to be 38.9%) and extractant are introduced into the upper end and lower end of the extraction tower respectively, wherein the extractant is a mixture of isopropyl acetate and benzene, xylene in a volume ratio of 2:2:1;

[0035] The volume ratio of the extractant to the crude aqueous acrylic acid solution in the extraction tower is controlled to be 1.1:1 at the same time.

[0036] The extraction treatment is not more than 60 minutes under room temperature conditions;

[0037] After standing and layering, the upper oil phase, i.e. the extraction phase, is collected to obtain an extraction liquid rich in acrylic acid; the lower aqueous phase is the raffinate phase.

[0038] The extraction liquid is introduced into a rectification tower for rectification, acrylic acid is discharged from the bottom of the rectification tower, and after collection, the purity is detected to be 99.0%, and the acrylic acid recovery rate is 96%.

[0039] Example 4

[0040] A method for preparing high-purity acrylic acid from a crude aqueous acrylic acid solution, the specific steps are as follows:

[0041] The crude aqueous acrylic acid solution (the mass concentration of acrylic acid is 38.9% after detection) and the extractant are respectively introduced into the upper end and the lower end of the extraction tower, wherein the extractant is a mixture of isopropyl acetate and benzene, toluene in a volume ratio of 2.7:2:1;

[0042] The volume ratio of the extractant to the crude aqueous acrylic acid solution in the extraction tower is controlled to be 1.8:1 at the same time.

[0043] The extraction treatment is performed for not more than 50 min at room temperature;

[0044] After standing and stratification, the upper oil phase, i.e., the extraction phase, is collected to obtain the extraction liquid rich in acrylic acid; and the lower water phase is the raffinate phase.

[0045] The extraction liquid is introduced into the rectification tower for rectification, acrylic acid is discharged from the bottom of the rectification tower, and the purity after collection is 99.2%, and the recovery rate of acrylic acid is 98%.

[0046] Comparative Example 1

[0047] A method for purifying a crude aqueous acrylic acid solution, the specific steps are as follows:

[0048] The crude aqueous acrylic acid solution (the mass concentration of acrylic acid is 38.9% after detection) and the extractant are respectively introduced into the upper end and the lower end of the extraction tower, wherein the extractant is a mixture of isopropyl acetate and xylene in a volume ratio of 9:1;

[0049] The volume ratio of the extractant to the crude aqueous acrylic acid solution in the extraction tower is controlled to be 30:1 at the same time.

[0050] The extraction treatment is performed for 50 min at room temperature;

[0051] After standing and stratification, the upper oil phase, i.e., the extraction phase, is collected to obtain the extraction liquid rich in acrylic acid; and the lower water phase is the raffinate phase.

[0052] The extraction liquid is introduced into the rectification tower for rectification, acrylic acid is discharged from the bottom of the rectification tower, and the purity after collection is 83.2%, and the recovery rate of acrylic acid is 72.9%.

[0053] Comparative Example 2

[0054] A method for purifying a crude aqueous acrylic acid solution, the specific steps are as follows:

[0055] The crude aqueous acrylic acid solution (the mass concentration of acrylic acid is 38.9% after detection) and the extractant are respectively introduced into the upper end and the lower end of the extraction tower, wherein the extractant is a mixture of isopropyl acetate and benzene, toluene in a volume ratio of 2.7:2:1;

[0056] The volume ratio of the extractant to the crude aqueous acrylic acid solution in the extraction tower is controlled to be 30:1 at the same time.

[0057] The extraction treatment is carried out at room temperature for 50 min;

[0058] After standing and layering, the upper oil phase, i.e. the extraction phase, is collected to obtain an extraction liquid containing acrylic acid; the lower water phase is the raffinate phase.

[0059] The extraction liquid is introduced into a rectification tower for rectification, acrylic acid is discharged from the bottom of the rectification tower, and after collection, the purity is detected to be 73.4%, and the acrylic acid recovery rate is 61.5%.

[0060] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for purifying a crude aqueous acrylic acid solution, characterized in that, The crude aqueous acrylic acid solution is extracted at room temperature with an extractant, and after static separation, the organic phase is collected to obtain an extract liquid rich in acrylic acid; finally, the extract liquid is introduced into a rectification tower for rectification, and high-purity acrylic acid is obtained at the bottom of the rectification tower; The extractant is a mixture of isopropyl acetate and benzene, toluene in a volume ratio of 2.7:2:1; The volume ratio of the extractant to the crude aqueous acrylic acid solution in the extraction tower is controlled to be 1.8:

1. The extraction treatment is not more than 50 min at room temperature.

2. The method of purifying a crude aqueous acrylic acid solution according to claim 1, wherein The extract liquid contains acrylic acid, the extractant and acetic acid.

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