METHOD OF SEPARATING A-OLEFIN BY A SIMULATED MOVING BED

Abstract

The present disclosure provides a method of separating α-olefin by a simulated moving bed. The method comprises using a coal-based Fischer-Tropsch synthetic oil as a raw material to obtain a target olefin having a carbon number N within a range from 9 to 18, wherein the raw material is subjected to treatment steps including pretreatment, fraction cutting, alkane-alkene separation, and isomer separation, thereby obtaining a high purity α-olefin product. As compared to conventional rectification and extraction processes, the product obtained by the method of the present disclosure has advantages of higher purity, higher yield, lower energy consumption, and significantly reduced production cost.

Claims

1. A method of separating α-olefin by a simulated moving bed, wherein a coal-based Fischer-Tropsch synthetic oil is used as a raw material, and a target olefin has a carbon number N within a range from 4 to 18, the method comprising steps of: (1) fraction cutting: subjecting a pretreated raw material to fraction cutting, to obtain a component having a carbon number of N; (2) alkane-alkene separation: subjecting the component obtained in step (1) to an alkane-alkene separation using a first simulated moving bed, to separate alkanes and alkenes, thereby obtaining an olefin-rich component; and (3) isomer separation: subjecting the olefin-rich component obtained in step (2) to an isomer separation using a second simulated moving bed, to separate a high purity α-olefin product.

2. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the first simulated moving bed in step (2) has process parameters as follows: an operating temperature of 50-110° C., an operating pressure of 0.3-0.8 MPa, and a mass ratio of adsorbent to synthetic oil of 0.5-4:1.

3. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the second simulated moving bed in step (3) has process parameters as follows: an operating temperature of 50-110° C., an operating pressure of 0.3-0.8 MPa, and a mass ratio of adsorbent to synthetic oil of 0.5-4:1.

4. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the adsorbent in the first simulated moving bed is a Series A molecular sieve.

5. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the adsorbent in the second simulated moving bed is a Series X molecular sieve.

6. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the target olefin has a carbon number N within a range from 9 to 18.

7. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the coal-based Fischer-Tropsch synthetic oil has an alkene content of 73-75 wt %, an alkane content of 22-25 wt %, and an oxygen-containing compound content of 3-5 wt %.

8. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the pretreatment step comprises a step of deacidifying the raw material.

9. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein both the first and second simulated moving beds comprise an adsorption bed, a raw material feeding system, a desorbent feeding system, a circulation system, an extract liquid system, a raffinate system, a program-controlled valve group and an automatic control system; wherein the adsorption bed comprises a plurality of adsorption columns and is divided into an adsorption area, a purification area, a desorption area and a buffering area; each of the adsorption columns is provided with a raw material feed valve, a desorbent feed valve, and a circulating fluid feed valve at a top end; each of the adsorption columns is provided with a raffinate discharge valve and a extract liquid discharge valve at a bottom end; a check valve is provided between two adjacent adsorption columns; the raw material feeding system is connected to the raw material feed valve of each of the adsorption columns; the desorbent feeding system is connected to the desorbent feed valve of each of the adsorption columns; the circulation system comprises a circulation pump, and is connected to the circulating fluid feed valve of each of the adsorption columns via the circulation pump; the extract liquid system is connected to the extract liquid discharge valve of each of the adsorption columns; the raffinate system is connected to the raffinate discharge valve of each of the adsorption columns; all of the valves form the program-controlled valve group, and the program-controlled valve group is connected to the automatic control system which is capable of controlling open and close states of each valve of the program-controlled valve group.

10. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the high purity α-olefin product has an α-olefin content of 99.2 wt % or more.

11. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the method does not comprise a step of removing oxygen-containing compound before the step of alkane-alkene separation.

12. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the first simulated moving bed in step (2) has process parameters as follows: an operating temperature of 60-100° C., an operating pressure of 0.4-0.6 MPa, and a mass ratio of adsorbent to synthetic oil of 0.5-2:1.

13. The method of separating α-olefin by a simulated moving bed according to claim 1, wherein the second simulated moving bed in step (3) has process parameters as follows: an operating temperature of 60-100° C., an operating pressure of 0.4-0.6 MPa, and a mass ratio of adsorbent to synthetic oil of 0.5-2:1.

14. The method of separating α-olefin by a simulated moving bed according to claim 4, wherein the Series A molecular sieve is 5A molecular sieve or modified 5A molecular sieve.

15. The method of separating α-olefin by a simulated moving bed according to claim 5, wherein the Series X molecular sieve is 13X molecular sieve or modified 13X molecular sieve.

16. The method of separating α-olefin by a simulated moving bed according to claim 6, wherein the target olefin has a carbon number N within a range from 9 to 16.

17. The method of separating α-olefin by a simulated moving bed according to claim 16, wherein the target olefin has a carbon number N within a range from 10 to 14.

18. The method of separating α-olefin by a simulated moving bed according to claim 17, wherein the target olefin has a carbon number N within a range from 10 to 12.

19. The method of separating α-olefin by a simulated moving bed according to claim 8, wherein after the raw material is subjected to a deacidification pretreatment, the distillate is fed into a light component removal column to separate components with a carbon number less than N from the overhead of the light component removal column, and the bottom components are fed into a heavy component removal column; and in the heavy component removal column, components with a carbon number greater than N are separated from the bottom of the heavy component removal column, and a component with a carbon number of N is separated from the overhead of the heavy component removal column.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0039] FIG. 1 is a schematic diagram of the method of separating α-olefin by a simulated moving bed according to the present invention.

DETAILED DESCRIPTION

[0040] The process flow of the present disclosure is as shown in FIG. 1, wherein the raw material is subjected to a pretreatment, a fraction cutting, an alkane-alkene separation with simulated moving bed I, and a linear alkene-alkene isoforms separation with simulated moving bed II to obtain an α-olefin product.

[0041] After the raw material is subjected to a deacidification pretreatment, the distillate is fed into a light component removal column to separate components with a carbon number less than N from the overhead of the light component removal column, and the bottom components are fed into a heavy component removal column. In the heavy component removal column, components with a carbon number greater than N are separated from the bottom of the heavy component removal column, and a component with a carbon number of N is separated from the overhead of the heavy component removal column. After fraction cutting, the oxygen-containing compound content in the distillate is further reduced.

[0042] In the simulated moving bed, the fixed adsorbent bed is divided into a plurality of sections, wherein the sections are charged with an adsorbent and inter-section liquids cannot be in fluid communication with each other directly. Each section is provided with inlet/outlet pipe(s), and the inflow/outflow is controlled by a valve. Typically, in a simulated moving bed having 8 adsorption columns, 20 inlets/outlets, among total 24 inlets/outlets, only serve for inter-section communication, and the other 4 inlets/outlets serve for the inflow or outflow of four material streams. At a certain moment, depending on the inlets/outlet positions of streams, the whole adsorption bed is divided into four areas with different lengths and different interphase mass transfer from each other. The four inlets/outlets for streams in the simulated moving bed move upwards at a speed synchronized with the change of solid phase concentration, thereby forming a closed loop. The overall result is substantially the same as the case where the solid adsorbent moves from top to bottom in an adsorber with the positions of the inlets/outlets kept unchanged, thereby achieving the separation effect.

[0043] The operating parameters for the simulated moving bed are as follows.

[0044] The first simulated moving bed: 50-110° C., an operating pressure of 0.3-0.8 MPa, a simulated moving bed adsorbent of Series A molecular sieve (for example, 3A, 4A, 5A or modified 5A molecular sieve), and a mass ratio of adsorbent to synthetic oil of 0.5-4:1. The content of olefin component obtained is 99.5 wt % or more.

[0045] The second simulated moving bed: 50-110° C., an operating pressure of 0.3-0.8 MPa, a simulated moving bed adsorbent of Series X molecular sieve (for example, 13X or modified 13X molecular sieve), and a mass ratio of adsorbent to synthetic oil of 0.5-4:1. The content of α-olefin component obtained is 99.6 wt % or more.

[0046] The distillate raw material used in the present disclosure is sourced from the coal-to-oil plant (1.2 million tons per year) from Yitai Chemical Industry Co. Ltd., Inner Mogolia, and the composition thereof is as shown in Table 1.

TABLE-US-00001 TABLE 1 The raw material components of the distillate No. Material type Content/wt % 1 Alkanes (n-alkane/alkane isoforms) 23.17 2 Alkenes (n-alkene/alkene isoforms) 71.83 3 Acids 0.5 4 Alcohols 4 5 Aldehydes, esters and ketones 0.5

[0047] The raw material components in the deacidified distillate are as shown in Table 2.

TABLE-US-00002 TABLE 2 The composition of the deacidified distillate No. Material type Content/wt % 1 Alkanes (n-alkane/alkane isoforms) 23.90 2 Alkenes (n-alkene/alkene isoforms) 74.10 3 Acids — 4 Aldehydes, esters and ketones 2

[0048] The raw material components in the distillate after fraction cutting are as shown in Table 3.

TABLE-US-00003 TABLE 3 The composition of the distillate after fraction cutting No. Material type Content/wt % 1 Alkanes (n-alkane/alkane isoforms) 24.40 2 Alkenes (n-alkene/alkene isoforms) 75.40 3 Acids — 4 Aldehydes, esters and ketones 0.2

Comparative Example 1

[0049] The target carbon number is 9. The raw material was pretreated, subjected to fraction cutting, and then subjected to an alkane-alkene separation by extractive rectification, without separation by a simulated moving bed. Here, for the alkane-alkene separation, the operating temperature was 100-105° C., the overhead temperature was 48-50° C., the reflux ratio was 5, the ratio of agent to oil (a mass ratio of adsorbent to synthetic oil) was 1:1, the extractant was NMP (referring to the 4th extractant in Example 1 of CN 105777467A), and the content of olefin component obtained was 98.08 wt %. No linear hydrocarbon-branched hydrocarbon separation was performed, since the difference in boiling point between the linear hydrocarbon and the branched hydrocarbon was only 3° C., and thus it was very difficult to separate them from each other by a rectification process.

Examples 1-10

[0050] In the treatment methods of Examples 1-10, the pretreatment and fraction cutting steps were the same as those in Comparative Example 1, but the fractions obtained after fraction cutting were fed to a first simulated moving bed for an alkane-alkene separation, and the separated olefin-rich product was fed to a second simulated moving bed for an isomer separation. Specific operating parameters are shown in Table 5. As seen from Table 5, the α-olefin obtained from separation by a simulated moving bed had a purity of not less than 99.2 wt %, and an oxygen-containing compound content of less than 50 ppm.

TABLE-US-00004 TABLE 5 The carbon numbers of target α-olefins and the process parameters for Examples 1-10 Operating Olefin Operating Content of Target parameters for content in parameters for Purity of oxygen- carbon simulated moving olefin-rich simulated moving final containing No. number bed I component bed II product compound Ex. 1 9 60° C., 0.5 MPa, 99.0 wt % 62° C., 0.52 MPa, 99.3 wt % <50 ppm Adsorbent: 4A Adsorbent: 10x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 3.5:1 mass ratio: 2.5:1 Ex. 2 10 67° C., 0.52 MPa, 99.1 wt % 67° C., 0.54 MPa, 99.3 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 1.5:1 mass ratio: 2:1 Ex. 3 11 70° C., 0.6 MPa, 99.2 wt % 73° C., 0.57 MPa, 99.5 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 3:1 mass ratio: 2.5:1 Ex. 4 12 73° C., 0.5 MPa, 99.1 wt % 70° C., 0.5 MPa, 99.4 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 1.8:1 mass ratio: 2:1 Ex. 5 13 88° C., 0.57 MPa, 99.1 wt % 85° C., 0.59 MPa, 99.3 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 2.5:1 mass ratio: 2.5:1 Ex. 6 14 91° C., 0.55 MPa, 99.0 wt % 90° C., 0.52 MPa, 99.2 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 1.6:1 mass ratio: 1.5:1 Ex. 7 15 96° C., 0.52 MPa, 99.0 wt % 98° C., 0.57 MPa, 99.2 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 1.5:1 mass ratio: 1.8:1 Ex. 8 16 100° C., 0.6 MPa, 99.1 wt % 102° C., 0.66 MPa, 99.3 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 2:1 mass ratio: 2:1 Ex. 9 17 105° C., 0.67 MPa, 99.2 wt % 103° C., 0.72 MPa, 99.3 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 2:1 mass ratio: 2.4:1 Ex. 10 18 110° C., 0.73 MPa, 99.2 wt % 106° C., 0.7 MPa, 99.4 wt % <50 ppm Adsorbent: 5A Adsorbent: 13x molecular sieve, molecular sieve, Adsorbent to oil Adsorbent to oil mass ratio: 2:1 mass ratio: 1.6:1