KR100741749B1 - Simulated moving bed adsorptive separation process using final product as secondary flush liquid - Google Patents

Abstract

The present invention relates to a separation method such as adsorptive separation of para-xylene from aromatic hydrocarbon mixtures containing other xylene isomers, and more particularly, simulated moving bed (SMB) adsorption chromatography. In a separation method using a chromatography, the present invention relates to a pseudo mobile bed adsorptive separation method capable of improving the purity and yield of the final product by using the final product as a secondary washing liquid.

Similar, moving bed, adsorption, separation, method, product, secondary, washing, liquid

Description

SIMULDED MOVING BED ADSORPTIVE SEPARATION PROCESS USING FINAL PRODUCT AS SECONDARY FLUSH LIQUID}

Figure 1 shows a schematic diagram of one embodiment of a system used in the pseudo mobile bed adsorptive separation process according to the present invention.

FIG. 2 is an enlarged view of portion 11a of FIG. 1 and is a schematic cross-sectional view of a bed in an adsorption chamber of one embodiment system used in the pseudo mobile bed adsorptive separation method according to the present invention.

3 is a plan view of a grid formed in a bed in an adsorption chamber of one embodiment system used in the pseudo moving bed adsorptive separation method according to the present invention.

4 is a graph showing the change over time of the PX concentration in the pipe used for the extract stream in Examples and Comparative Examples of the present invention.

BRIEF DESCRIPTION OF THE MAIN SIGNS IN THE FIGURE

1: adsorption chamber 2: rotary valve

3: raffinate column 4: extract column

5: circulation pump 11: bed

12: grid 13: bed line

14: center pipe 21: multiple access lines

22: fluid mixture inlet port 23: raffinate outlet port

24: Desorbent Inlet Port 25: Extraction Outlet Port

31: First separator 41: Second separator

The present invention relates to a separation method such as adsorptive separation of para-xylene from aromatic hydrocarbon mixtures containing other xylene isomers, and more particularly, simulated moving bed (SMB) adsorption chromatography. In a separation method using a chromatography, the present invention relates to a pseudo mobile bed adsorptive separation method capable of improving the purity and yield of the final product by using the final product as a secondary washing liquid.

Batch type chromatography, which is generally used, is a separation method based on the adsorption mechanism, and is suitable for high purity separation and laboratory analysis. Therefore, it is widely used for separation and purification of high purity biosynthetic compounds, fine chemical compounds, and food additives. It is used. However, this separation method using batch chromatography requires a large consumption of the solvent used as the mobile phase, it is difficult to separate when the adsorption degree of the component to be separated is small, and furthermore, large-capacity separation and continuous separation of raw materials. It has the problem of being inadequate.

As a method for solving this problem, there is a true moving bed (TMB) adsorptive separation method mentioned in Korean Patent Laid-Open Publication No. 2001-51842, and the like, which is effective in various methods such as heat exchanger and extraction. Introduced the concept of counter current flow, which is applied to the stationary phase in the opposite direction to the mobile phase, when the solution of the mixture to be separated is injected into the column, The low-adsorbing component flows out of the column along the mobile phase, so that a pure substance can be obtained if it can be separated only at both ends of the concentration distribution curve of the two substances even if the separation between the two substances is not large. On the other hand, the amount of filler must be increased compared to the conventional fixed separation method, Due to friction and spillage of fillers, steady operation is very difficult.

Developed to overcome the disadvantages of the TMB method is a simulated moving bed (SMB) adsorptive separation method. In the SMB method, the fixed bed adsorbent is packed into a column and fixed, and the port between the columns is moved at regular time to simulate the countercurrent flow of the solid phase, thereby overcoming the problems of the fixed bed flow of the TMB method. The SMB method is currently applied to the purification of para-xylene from a mixture of aromatic hydrocarbons, the separation of ethylbenzene, and the separation of chiral compounds. Representative methods commercially applied among the SMB methods are disclosed in U.S. Pat. Nos. 4,326,092 and 5,382,747, which are commonly referred to as 'Parex processes'.

In the para-xylene separation method by the SMB method, injecting and extracting the raw material and the desorbent, and the discharge of the raffinate are all made through the same pipe. This piping, which connects the adsorption chamber and the rotary valve, exists as many as the number of beds in the adsorption chamber and is called a bed line. According to the operating procedure of the SMB method, any pipe used for raw material injection is used. Certain pipes will be reused for the final product release after a certain period of time. At this time, the initial discharge portion of the final product discharged during the time interval that the rotary valve rotates, that is, the switching time (mixing) of the raw material filled in the pipe is mixed to reduce the purity of the final product, which is currently commercialized The SMB method performs a procedure called line flush and secondary flush as a measure to prevent this.

Line cleaning is a process that involves returning a small amount of liquid in the adsorption chamber from the bed just below the bed into which the desorbent, such as para-diethylbenzene (PDEB), is injected, back into the adsorption chamber through multiple access lines and bed lines. It is a procedure to wash the inside of the pipes of access line and bed line. In addition, since the liquid used to clean the line contains some other liquid component rather than a pure desorbent, an additional line cleaning procedure to wash this pipe once again with pure desorbent is called a secondary wash. That is, the secondary washing refers to a procedure for finally washing the inside of the pipe by injecting pure desorbent into the adsorption chamber through the pipe immediately before discharging the final product. The reason why the second wash is performed with pure desorbent is that even if the desorbent is mixed in the extract, it does not matter because it is easily separated from the final product through the distillation method before extracting the final product.

However, although it is true that the desorbent is easily separated from the final product through the distillation method, when a desorbent such as PDEB is used as the secondary cleaning liquid, the desorbent may actually be removed immediately before the final product inside the adsorption chamber is discharged. There is a problem that the concentration is unnecessarily increased, and therefore, the concentration of the target substance such as para-xylene appears to be greatly reduced at the beginning of the discharge, and thus there is a problem that adversely affects the productivity.

The present invention is to solve the problems of the prior art as described above, the object of the present invention, by using the final product as a secondary washing liquid in the method of similar mobile bed adsorptive separation, compared to the prior art of the final product It is to provide a pseudo moving bed adsorptive separation method that can improve the purity and yield.

According to the invention, one or more adsorption chambers comprising a plurality of beds comprising a grid filled with adsorbent, said adsorption chamber and fluid mixture inlet port, raffinate port, desorbent inlet port and extract outlet port connected to multiple access lines. A rotary valve, a raffinate column separated through the raffinate outlet port, a raffinate column for returning a portion back to the adsorption chamber, an extract extracted through the extract outlet port, and partially And an extract column for returning back to the adsorption chamber, wherein the rotary valve rotates according to a switching time so that the fluid mixture inlet port, raffinate outlet port, extract outlet port, and desorbent inlet port are adjacent to each other. Pseudo-mobile bed adsorption connected to the access line Using a separation system, at least one component of the fluid mixture comprising the desorbent is separated from the fluid mixture by contacting with and adsorbing a solid adsorbent to obtain a similar moving bed that yields a final product mainly comprising the separated component. In the adsorptive separation process, a process is provided characterized in that the final product is used as the second washing liquid of the multiple access lines.

The system used in the pseudo mobile bed adsorptive separation method according to the present invention includes an adsorption chamber, a plurality of beds formed in the adsorption chamber, a grid partitioning the bed and supporting the adsorbent, a fluid mixture inlet port, a raffinate port, a desorbent A rotary valve for connecting the inlet port and the extract outlet port to the multiple access lines, the raffinate drawn out through the raffinate outlet port is separated through a first separator, and a portion of the desorbent inlet port is again used as a desorbent. A raffinate column for returning to, comprising an extract column for separating the extract withdrawn through the extract outlet port through a second separator and returning a portion back to the desorbent inlet port as a desorbent.

In addition, the pseudo mobile bed adsorptive separation method according to the present invention, the adsorbent filled in each bed in the adsorption chamber by introducing the fluid mixture into the adsorption chamber through a multiple access line connected to the rotary valve through the fluid mixture inlet port A relatively low adsorbent raffinate from the bed into a raffinate port, separating the withdrawn raffinate into a high boiling point component and a low component in a raffinate column, and part of the separated raffinate Is supplied as a desorbent to the bed through a desorbent inlet port and the remaining part of the raffinate is drawn out through the first separator, and the extract having a relatively strong adsorbent component and the desorbent in the bed is extracted into the extract port. The extracted extract was extracted from the extract column with high boiling point Separating the lower and lower components, and returning some of the separated extracts as additional desorbents to the desorbent inlet port and withdrawing the remaining portion of the extract from the second separator, the rotary according to a switching time. As the valve rotates, the fluid mixture inlet port, raffinate outlet port, extract outlet port and desorbent inlet port move and connect to adjacent multiple access lines.

In the pseudo mobile bed adsorptive separation method such as the present invention, a small amount of the liquid in the adsorption chamber drawn from the bed immediately below the bed into which the desorbent such as para-diethylbenzene (PDEB) is injected is used. By returning through the inside of the adsorption chamber through the line washing procedure to wash the inside of the pipes of the multiple access line and bed line and the secondary cleaning procedure to additionally wash the primary washed line.

In the pseudo mobile bed adsorptive separation method according to the present invention, the liquid used in the secondary washing procedure is characterized by secondary washing of multiple access lines using the final product of the pseudo mobile bed adsorptive separation method. That is, if the pseudo mobile bed adsorptive separation method according to the present invention is a method for adsorptive separation of para-xylene from an aromatic hydrocarbon mixture containing other xylene isomers to obtain purified para-xylene as a final product, Para-xylene is used as the liquid for secondary washing of multiple access lines.

Hereinafter, with reference to the accompanying drawings the contents of the present invention will be described in detail below.

Figure 1 shows a schematic diagram of one embodiment of a system used in the pseudo mobile bed adsorptive separation process according to the present invention.

According to Fig. 1, in the system usable for the pseudo moving bed adsorptive separation method according to the present invention, the adsorption chamber 1 is composed of a plurality of beds, and each bed is filled with an adsorbent. Each bed in the adsorption chamber 1 of the present invention is connected to the rotary valve 2 via multiple access lines 21. The number of beds is typically 12, but there is no particular limitation.

The rotary valve 2 has multiple accesses to each of the two inlet and two outlet ports, such as fluid mixture inlet port 22, raffinate port 23, desorbent inlet port 24 and extract outlet port 25. To the line 21. The detailed configuration of the rotary valve 2 can be easily implemented by those skilled in the art.

The raffinate column 3 separates the raffinate drawn out through the raffinate outlet port 22 again through the first separator and returns a portion back to the desorbent inlet port 24 as the desorbent.

The extract column 4 separates the extract withdrawn via the extract outlet port 25 again through a second separator and returns a portion back to the desorbent inlet port 24 as the desorbent.

In one embodiment of the system usable for the pseudo mobile bed adsorptive separation method according to the present invention, as shown in FIG. 1, one long adsorption chamber 1 is divided into several beds 11 in series with each other. However, in another embodiment, two long adsorption chambers as shown in FIG. 1 may be used. In the pseudo mobile bed adsorptive separation method such as the present invention, there is practically no flow of the fixed phase, and the position of the ports of the desorbent, the extract, the fluid feed, and the raffinate according to the switching interval of a certain time. If is changed in the direction in which the mobile phase flows, the column is placed in a direction opposite to the direction in which the mobile phase flows relative to each port. In this way, a virtual stationary phase flow can be created to simulate the mobile phase and countercurrent flow. The adsorbent used as the stationary bed is filled in the bed.

The position of each of the ports 22, 23, 24, 25 of the desorbent, extract, feed and raffinate cannot be moved continuously, as shown in FIG. Multiple access lines 21 are installed to provide a constant switching time interval through the rotary valve 2 to periodically move each flow to a neighboring line. The effect can be obtained. Accordingly, the weakly adsorbed material of the material injected through the fluid mixture inlet port exits to the raffinate outlet port along the mobile phase, and the strongly adsorbed material is adsorbed to the adsorbent in each bed 11 of the adsorption chamber 1. Since the column moves relative to the switching of a certain time, it uses the principle to come out to the extract outlet port (25).

Referring to Figure 1 describes the adsorptive separation method of the present invention.

First, inert particles are filled in the upper part of the adsorbent filled in each bed 11 in the adsorption chamber 1. The fluid mixture is introduced into the adsorption chamber 1 through multiple access lines 21 connected to the rotary valve 2 via the fluid mixture inlet port 22 and filled in each bed 11 in the adsorption chamber. Contact with the adsorbent. The relatively low adsorption raffinate from the bed 11 is withdrawn to the raffinate outlet port 23. The drawn raffinate is separated into a high boiling point component and a low component in the raffinate column 3, and a portion of the raffinate is fed back to the bed 11 through the desorbent inlet port 24 as a desorbent. The remaining portion of the raffinate is withdrawn through the first separator 31.

In the bed 11, the extract having the relatively strong adsorptive force and the desorbent is taken out to the extract outlet port 25. The extracted extract is separated into a high boiling point component and a low component in the extract column (4). Some of the separated extract is returned to the desorbent inlet port 24 as a further desorbent and the remaining portion of the extract is withdrawn from the second separator 41. The fluid mixture inlet port, raffinate outlet port, extract outlet port and desorbent inlet port connected to each bed 11 are moved to adjacent multiple access lines by rotating the rotary valve according to the switching time. Is connected.

In addition, for the cleaning of the multiple access lines, a small amount of liquid in the adsorption chamber drawn from the bed immediately below the bed into which the desorbent is injected is returned to the inside of the adsorption chamber through the multiple access lines and the bed line. The inside of the pipe is first washed, and this first washed line is further washed second with a final product such as para-xylene.

FIG. 2 is an enlarged view of part 11a of FIG. 1, which is a schematic cross-sectional view of the bed 11 in the adsorption chamber 1 according to the present invention, and FIG. 3 is a grid 12 formed in the bed 11 of the present invention. ) Is a plan view.

As shown in FIG. 2, the grid 12, which is a space for supporting the adsorbent, is formed inside the bed 11. Fluid movement between the upper and lower beds takes place via a grid 12, with each grid 12 connected to a center pipe distributor 15 and to multiple access lines 21 via a bed line 13. As shown in FIG. 3, the grid 12 of the present invention has a two-ply screen, which acts as a diaphragm of the bed 11 by passing only a liquid fluid, and consists of 24 pieces of pie shapes.

The present invention will be further illustrated by the following examples, which are merely illustrative of the present invention and are not intended to limit or limit the scope of the present invention.

Examples and Comparative Examples

In this Example and Comparative Example, a method of adsorptive separation of para-xylene from an aromatic hydrocarbon mixture containing other xylene isomers was carried out using a pseudo mobile bed adsorptive separation system as shown in FIG. Under the same conditions, except that para-xylene (PX), the final product in the examples, and paradiethylbenzene (PDEB), the desorbent, were used in the examples as secondary washing liquids for multiple access lines. Was performed.

While the method was performed, the concentration of PX in the pipe used for the extract stream was measured and the change over time was shown in FIG. 4, and the yield of the final product and the purity of the final product obtained as a result of adsorptive separation of para-xylene. And production rates are shown in Table 1 below.

TABLE 1

Secondary cleaning liquid yield(%) Purity (% by weight) Production speed (tons / hour) Example PX 99.5 99.75 53.8 Comparative example PDEB 98.9 99.73 53.5

According to Figure 4, in the case of the comparative example using the desorbent PDEB as the secondary washing liquid, it can be seen that the concentration of the initial PX in the effluent stream significantly reduced, from which the desorbent is used as the secondary washing liquid In other words, it was found to be disadvantageous in terms of productivity compared to the case of using the final product. In addition, according to Table 1, it was found that the use of the final product as a secondary cleaning liquid in terms of substantial recovery while securing a certain level of purity is advantageous for increasing PX productivity.

As described above, according to the present invention, the purity and yield of the final product can be improved by a simple method in the pseudo mobile bed adsorptive separation method.

Claims (2)

At least one adsorption chamber comprising a plurality of beds comprising a grid filled with adsorbent, a rotary valve connecting the adsorption chamber and fluid mixture inlet port, raffinate port, desorbent inlet port and extract outlet port to multiple access lines, A raffinate column for separating the drawn raffinate through the raffinate outlet port, returning a portion back to the adsorption chamber, isolating the extract withdrawn through the extract outlet port, and partially back to the adsorption chamber And an extract column for returning to the apparatus, wherein the rotary valve rotates according to a switching time so that the fluid mixture inlet port, raffinate outlet port, extract outlet port, and desorbent inlet port move to adjacent multiple access lines. Connected mobile bed adsorptive separation system In a pseudo moving bed adsorptive separation process in which at least one component of a fluid mixture comprising a desorbent is separated from the fluid mixture by contact with a solid adsorbent for adsorption to obtain a final product comprising the separated component. The method of claim 1, wherein the final product is used as a liquid for secondary washing of the multiple access lines. The method of claim 1 wherein the final product is para-xylene.

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