Separation method of ethylene selective tetramerization product

Abstract

The invention provides a separation method of an ethylene selective tetramerization product, which comprises the following steps: (1) feeding the ethylene selective tetramerization product into a rectifying tower for rectification treatment, extracting a light component material flow from the tower top of the rectifying tower, and extracting a heavy component material flow from the tower kettle; (2) carrying out octene tower separation on the light component material flow, extracting a hexene material flow from the tower top, extracting methyl cyclopentane and methylene cyclopentane material flows from the side line, and extracting an octene material flow from the tower kettle; and (3) filtering the heavy component material flow, and carrying out solvent separation in a solvent separation device to obtain a solvent, decene and olefin components with more than C10. According to the separation method provided by the invention, a mode of combining tower separation and membrane separation is adopted, so that the number of rectifying towers is reduced, the investment cost and the separation energy consumption are reduced, and the method has wide industrial application value.

Description

Technical Field

[0001] The invention relates to the technical field of alpha-olefin separation, and in particular to a method for separating ethylene selective tetramerization products. Background Art

[0002] Linear α-olefin is an important chemical raw material, which can be used in the fields of comonomer of linear low-density polyethylene, alcohol for synthetic plasticizer, surfactant intermediate, synthetic lubricant, etc. The linear low-density polyethylene resin produced with 1-octene as comonomer has significantly improved tensile strength, impact strength, tear strength, puncture resistance, environmental stress cracking resistance, etc., and is widely used in packaging films and agricultural covering films for greenhouses, sheds, etc.

[0003] Ethylene tetramerization can produce 1-octene with high selectivity, but the ethylene conversion rate per pass in the reaction is only about 50%, resulting in the product containing a large amount of solvent in addition to hexene, methylcyclopentane, methylenecyclopentane, octene and decene. The presence of solvent will affect the purity of the product, and the solvent needs to be separated from the product. The traditional separation method uses distillation, which greatly increases the investment cost and energy consumption of the device.

[0004] Patent CN116059939A adopts a sequential separation method to achieve ethylene, C6, solvent, C8 and C through four distillation towers. 10 + The separation not only has high investment cost, but also high separation energy consumption.

[0005] Patent CN116571203A uses cyclohexane as the reaction solvent, and the separation unit is through a decene recovery tower (C 10 The solvent, 1-hexene and light components are evaporated to a subsequent solvent recovery tower (C6 tower) to separate the solvent, 1-hexene and light components.

[0006] Patent CN113233951B uses cyclohexane as solvent to evaporate light components below C8 from the top of the tower to the subsequent separation tower, and heavy components above C8 are transported from the bottom of the tower to the heavy component separation tower.

[0007] In patent CN116969809A, toluene as a solvent also needs to be evaporated from the top of the tower and reused after evaporation, which makes the energy consumption of the separation unit higher.

[0008] In patent CN117209350A, cyclohexane is used as the solvent. After the kettle materials from separation towers I and II are separated in tower III, the solvent cyclohexane is taken out from the top of the tower.

[0009] In summary, in the prior art, the ethylene selective tetramerization product is separated by distillation, which requires the solvent to be evaporated from the bottom of the tower to the top of the tower and then enter the subsequent tower to separate the solvent, which will inevitably cause extremely high separation energy consumption, thereby increasing the operating cost of the device. Therefore, it is extremely important to optimize the separation method, reduce the separation energy consumption, and ensure the low-cost operation of the device. Summary of the invention

[0010] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for separating ethylene selective tetramerization products. The separation method adopts a combination of tower separation and membrane separation to reduce the number of distillation towers, reduce investment costs and separation energy consumption, and has broad industrial application value.

[0011] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0012] The present invention provides a method for separating an ethylene selective tetramerization product, the separation method comprising:

[0013] (1) sending the ethylene selective tetramerization product into a distillation tower for distillation treatment, wherein a light component stream is taken out from the top of the distillation tower, and a heavy component stream is taken out from the bottom of the tower;

[0014] (2) After the light component stream is separated in an octene tower, a hexene stream is produced from the tower top, a methylcyclopentane and a methylenecyclopentane stream are produced from the side line, and an octene stream is produced from the tower bottom;

[0015] (3) After the heavy component is filtered, the solvent is separated in a solvent separation device to obtain solvent, decene and C 10 The above olefin components.

[0016] In the separation method of the present invention, the ethylene selective tetramerization product mentioned comprises solvent, methylcyclopentane, methylenecyclopentane, hexene, octene, decene and C 10 In some specific embodiments, based on the sum of the masses of the components in the ethylene selective tetramerization product as 100%, the content of the solvent is 50% to 60%, the content of methylcyclopentane and methylenecyclopentane is 2% to 3%, the content of hexene is 9% to 12%, the content of octene is 25% to 30%, the content of decene and C 10 The content of the above olefin components is 4% to 5%. Specifically, the ethylene selective tetramerization product can be prepared by the method in the prior art, and the preparation method will not be described in detail here.

[0017] In some specific embodiments, in step (1), the operating pressure of the distillation tower is 3 kPaG to 18 kPaG, for example, 8 kPaG, 13 kPaG, 15 kPaG; the bottom temperature of the distillation tower is 122 to 137°C, for example, 128°C, 130°C, 135°C.

[0018] In some specific embodiments, the content of the solvent in the stream extracted from the top of the distillation tower is 0.01 wt% to 0.1 wt%, for example, 0.02 wt%, 0.05 wt%, 0.06 wt%, 0.08 wt%.

[0019] In the separation method provided by the present invention, the solvent in step (1) is selected from cyclic carbon compounds with a boiling point ≥135°C; in some preferred embodiments, the solvent is selected from aromatic compounds or alicyclic compounds; more preferably, the solvent is selected from one or more of xylene, hexahydroindane or 1,3,5-trimethylcyclohexane.

[0020] In the separation method provided by the present invention, the operating pressure of the octene tower in step (2) is 10 kPaG to 30 kPaG, for example, 20 kPaG, 25 kPaG; the bottom temperature of the octene tower is 80 to 90°C, for example, 85°C, 88°C.

[0021] In some specific embodiments, the octene content in the logistics extracted from the top of the octene tower is 0.01wt% to 0.10wt%, for example, 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%; the octene content in the logistics extracted from the side line is 0.05wt% to 0.15wt%, for example, 0.06wt%, 0.08wt%, 0.10wt%, 0.12wt%.

[0022] In the separation method provided by the present invention, the heavy component logistics in step (3) enters the heavy component storage tank for storage, and then the heavy component is transported to the filter for filtration by a delivery pump; in some specific embodiments, the heavy component storage tank is a pressure-resistant storage tank, and its operating pressure is 1.0MPaG-2.0MPaG, and its operating temperature is 30-50°C. In some specific embodiments, the jacket of the heavy component storage tank is passed with warm water at 30°C-50°C.

[0023] In some specific embodiments, the heavy component is filtered in a filter with a filtration accuracy of 1 to 10 μm (eg, 5 μm, 8 μm); in some preferred embodiments, the filter is selected from a quick-release filter bag filter.

[0024] In the separation method provided by the present invention, the solvent separation device adopts membrane separation, and specifically the components passing through the membrane are decene and C 10The above olefin components, the component that does not pass through the membrane is the solvent; the solvent obtained after solvent separation contains decene and C 10 The content of the above olefin component is 0.1wt% to 0.5wt%, for example, 0.2wt%, 0.3wt%, 0.4wt%.

[0025] In the separation method provided by the present invention, the operating pressure in the solvent separation device is 3.0 MPaG to 6.0 MPaG, and the operating temperature is 30° C. to 50° C.

[0026] The above technical solution has the following technical effects:

[0027] The separation method provided by the present invention adopts a combination of tower separation and membrane separation. Light components with a boiling point lower than that of the solvent are separated by a distillation tower, and the solvent and heavy components above the solvent are separated by a membrane. This method reduces the number of distillation towers, reduces investment costs and separation energy consumption, improves product competitiveness, and has broad industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : A specific implementation of the separation method provided by the present invention;

[0029] Figure 2 : Schematic diagram of the separation unit used in Comparative Example 1;

[0030] Figure 3 : Schematic diagram of the separation unit used in Comparative Example 2;

[0031] Among them, 1. distillation tower, 2. octene tower, 3. heavy component storage tank, 4. filter, 5. transfer pump, 6. solvent separation device, 7. circulation pump, 8. heat exchanger, 9. liquid level regulating valve. DETAILED DESCRIPTION

[0032] In order to better understand the technical solution of the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0033] The following embodiments of the present invention use the following method to separate the ethylene selective tetramerization product:

[0034] like Figure 1As shown, the ethylene selective tetramerization product is sent to the distillation tower 1 for distillation separation, the light component logistics extracted from the top of the distillation tower 1, the bottom logistics of the tower is partially extracted to the heavy component storage tank 3 through the circulating pump 7 below the distillation tower 1, and the other part of the heavy component is returned to the bottom of the tower after passing through the heat exchanger 8; the light component logistics enters the octene tower 2 for separation, the hexene logistics is extracted from the top of the tower, the methylcyclopentane and methylenecyclopentane logistics are extracted from the side line, and a part of the bottom logistics of the tower is extracted to octene through the circulating pump 7 below the octene tower 2, and the other part is returned to the bottom of the tower through the heat exchanger 8. In some specific embodiments, a liquid level regulating valve 9 is provided on the pipeline of the bottom logistics of the tower, which is used to interlock and adjust the liquid level in the tower.

[0035] The heavy component flow in the bottom of the distillation tower 1 is transported to the heavy component storage tank 3 through a pipeline, filtered by a filter 4 (the filtering accuracy is 8 μm) after storage, and transported by a delivery pump 5 to a solvent separator 6 for solvent separation, and a solvent is obtained at the bottom of the separator, and decene and above olefin components are obtained in the middle.

[0036] Example 1

[0037] The above method is used to separate the ethylene selective tetramerization product (the solvent is xylene). The specific composition of the ethylene selective tetramerization product is: xylene 60.0%, hexene 9.0%, octene 25.0%, methylcyclopentane and methylenecyclopentane 2.0%, decene and C 10 The above olefin components 4.0%;

[0038] The parameters of the specific separation method are controlled as follows:

[0039] (1) The tower pressure of the distillation tower is 3 kPaG, and the tower bottom temperature is 122° C.; the solvent content in the stream taken out from the top of the distillation tower is 0.03 wt%;

[0040] (2) The tower pressure of the octene tower is 10 kPaG, and the tower bottom temperature is 80° C.; the octene content in the stream taken out from the top of the octene tower is 0.02 wt %, and the octene content in the stream taken out from the side line is 0.09 wt %; the octene content in the octene stream taken out from the tower bottom is 99.97 wt %;

[0041] (3) The pressure in the heavy component storage tank is 2 MPaG and the temperature is 50°C;

[0042] The operating pressure of the membrane separation in the solvent separation device is 3.0 MPaG and the temperature is 30°C; the purity of the obtained solvent is 99.90%, decene and C 10 The purity of the above olefin components is 98.85%.

[0043] Example 2

[0044] The above method is used to separate the ethylene selective tetramerization product (the solvent is hexahydroindane). The specific composition of the ethylene selective tetramerization product is: hexahydroindane 50.0%, hexene 12.0%, octene 30.0%, methylcyclopentane and methylenecyclopentane 3.0%, decene and C 10 The above olefin components 5.0%;

[0045] The parameters of the specific separation method are controlled as follows:

[0046] (1) The tower pressure of the distillation tower is 18 kPaG, and the tower bottom temperature is 137° C.; the solvent content in the stream taken out from the top of the distillation tower is 0.10%wt;

[0047] (2) The tower pressure of the octene tower is 30 kPaG, and the tower bottom temperature is 90° C.; the octene content in the stream taken out from the top of the octene tower is 0.10 wt %, and the octene content in the stream taken out from the side line is 0.15 wt %; the octene content in the octene stream taken out from the tower bottom is 99.90 wt %;

[0048] (3) The pressure in the heavy component storage tank is 1 MPaG and the temperature is 30°C;

[0049] The operating pressure of the membrane separation in the solvent separation device is 6.0MPaG and the temperature is 50℃; the purity of the obtained solvent is 99.95%, decene and C 10 The purity of the above olefin components is 99.58%.

[0050] Example 3

[0051] The above method is used to separate the ethylene selective tetramerization product (solvent is 1,3,5-trimethylcyclohexane). The specific composition of the ethylene selective tetramerization product is: 1,3,5-trimethylcyclohexane 55.0%, hexene 10.5%, octene 27.5%, methylcyclopentane and methylenecyclopentane 2.5%, decene and C 10 The above olefin components 4.5%;

[0052] The parameters of the specific separation method are controlled as follows:

[0053] (1) The tower pressure of the distillation tower is 10 kPaG, and the bottom temperature of the tower is 128° C.; the solvent content in the stream taken out from the top of the distillation tower is 0.07 wt%;

[0054] (2) The tower pressure of the octene tower is 20 kPaG, and the tower bottom temperature is 85° C.; the octene content in the stream taken out from the top of the octene tower is 0.08 wt %, and the octene content in the stream taken out from the side line is 0.12 wt %; the octene content in the octene stream taken out from the tower bottom is 99.93 wt %;

[0055] (3) The pressure in the heavy component storage tank is 1.5 MPaG and the temperature is 40°C;

[0056] The operating pressure of the membrane separation in the solvent separation device is 4.5MPaG and the temperature is 40℃; the purity of the obtained solvent is 99.6%, decene and C 10 The purity of the above olefin components is 98.42%.

[0057] Comparative Example 1

[0058] Toluene was used as solvent, according to the separation process of patent CN116969809A (such as Figure 2 As shown), separation is performed, wherein the ethylene selective tetramerization product comprises: toluene 53.1% hexene 11.4% octene 28.2% methylcyclopentane and methylenecyclopentane 2.6%, decene and C 10 The above olefin components are 4.7%.

[0059] The separation method is as follows:

[0060] (a) introducing the ethylene tetramerization product into a deoctenization tower, wherein the operating pressure of the deoctenization tower is -75 kPa(g) to -65 kPa(g), the bottom temperature of the tower is 140°C to 160°C, and an octene-rich stream (10) is extracted from the top of the deoctenization tower, wherein the toluene content is 40 wt% to 50 wt% and the octene content is 35 wt% to 45 wt%.

[0061] (b) the top stream of the deoctenization tower enters the dehexene tower, the operating pressure of the dehexene tower is 10kPa(g)-20kPa(g), the bottom temperature is 115°C-125°C, the top of the dehexene tower produces a stream containing hexene, methylcyclopentane and methylenecyclopentane, wherein the content of 1-hexene is greater than 85wt%. The bottom of the tower produces a stream containing octene and toluene, wherein the content of toluene is 50wt%-60wt%, and the content of 1-octene is 40wt%-50wt%;

[0062] (c) The logistics extracted from the bottom of the dehexene tower enters the octene distillation tower, the operating pressure of the octene distillation tower is -80kPa(g) to -70kPa(g), the bottom temperature is 80°C to 90°C, the octene logistics extracted from the bottom of the tower has a toluene content of <1ppm(wt), and a 1-octene content of>99.5wt%. The toluene-rich logistics extracted from the top of the tower enters the toluene distillation tower, the toluene content of the toluene-rich logistics is 90wt% to 99wt%, and the 1-octene content is 1wt% to 10wt%.

[0063] (d) The operating pressure of the toluene distillation tower is 10 kPa(g)-20 kPa(g), the bottom temperature is 120°C-130°C, a toluene stream is produced from the top of the tower, and the toluene content is>99.9wt%. The octene-rich stream produced from the bottom of the tower is returned to the octene distillation tower, wherein the octene content is 80wt%-95wt%, and the toluene content is <1wt%.

[0064] Comparative Example 2

[0065] Cyclohexane was used as solvent and the separation process according to patent CN117209350A (such as Figure 3 The ethylene selective tetramerization product consists of 57.5% cyclohexane, 9.6% hexene, 26.4% octene, 2.3% methylcyclopentane and methylenecyclopentane, 2.3% decene and C 10 The above olefin components are 4.2%.

[0066] The separation method is as follows:

[0067] (a) The ethylene selective tetramerization product is sent to separation tower I. The top temperature of separation tower I is 55-57°C and it is operated at normal pressure. The light component containing hexene is extracted from the top of separation tower I and sent to separation tower II. The bottom of separation tower I is directly extracted and sent to separation tower III.

[0068] (b) Separation tower II is operated at normal pressure, and the tower top temperature is 8-12°C. After the light component containing hexene is distilled and separated in separation tower II, the material with a boiling point lower than hexene is taken out from the tower top, and the hexene product (S10) is taken out from the side outlet of the upper part of the tower. The hexene purity is ≥95.90%, and the bottom component enters separation tower III;

[0069] (c) The operating pressure of separation tower III is 2 bar to 3 bar, and the tower top temperature is 106 to 124°C. The bottom materials from separation towers I and II are separated in tower III, and cyclohexane (D3) is produced from the top of the tower. The purity of cyclohexane is ≥98.04%, and the bottom components enter separation tower IV;

[0070] (d) Separation tower IV is operated at normal pressure, and the top temperature is 120-121° C. After the material from separation tower III is separated by separation tower IV, octene (D4) with a purity of ≥99.9% is obtained from the top of the tower, and components above C8 (W4) are obtained from the bottom of the tower.

[0071] It can be seen from the above comparative data that the separation method of the present invention adopts a combination of tower separation and membrane separation, which reduces the number of distillation towers, reduces investment costs and separation energy consumption, and on the other hand, the separation method obtains high-purity products, wherein the purity of octene is ≥99.90%, the purity of solvent is ≥99.90%, and the purity of decene and C 10The purity of the above olefin components reaches above 98.00%. In summary, the separation method of ethylene selective tetramerization product provided by the present invention can reduce investment and energy consumption on the basis of ensuring product purity, and is a green and economical separation method.

Claims

1. A method for separating ethylene selective tetramerization products, characterized in that: The separation method comprises: (1) sending the ethylene selective tetramerization product into a distillation tower for distillation treatment, wherein a light component stream is taken out from the top of the distillation tower, and a heavy component stream is taken out from the bottom of the tower; (2) After the light component stream is separated in an octene tower, a hexene stream is produced from the tower top, a methylcyclopentane and a methylenecyclopentane stream are produced from the side line, and an octene stream is produced from the tower bottom; (3) After the heavy component is filtered, the solvent is separated in a solvent separation device to obtain solvent, decene and C 10 The above olefin components.

2. The separation method according to claim 1, characterized in that In step (1), the ethylene selective tetramerization product comprises solvent, methylcyclopentane, methylenecyclopentane, hexene, octene, decene and C 10 Olefins above; Preferably, the content of the solvent is 50% to 60%, the content of methylcyclopentane and methylenecyclopentane is 2% to 3%, the content of hexene is 9% to 12%, the content of octene is 25% to 30%, the content of decene and C 10 The content of the above olefin components is 4% to 5%.

3. The separation method according to claim 1, characterized in that The operating pressure of the distillation tower is 3kPaG-18kPaG, and the bottom temperature is 122-137°C; Preferably, the content of the solvent in the stream taken out from the top of the distillation tower is 0.01 wt% to 0.1 wt%.

4. The separation method according to any one of claims 1 to 3, characterized in that In step (1), the solvent is selected from cyclic carbon compounds with a boiling point ≥ 135°C; Preferably, the solvent is selected from aromatic compounds or alicyclic compounds; More preferably, the solvent is selected from one or more of xylene, hexahydroindane or 1,3,5-trimethylcyclohexane.

5. The separation method according to claim 4, characterized in that In step (2), the operating pressure of the octenyl tower is 10 kPaG to 30 kPaG, and the bottom temperature of the tower is 80 to 90°C.

6. The separation method according to claim 5, characterized in that The octene content in the stream taken out from the top of the octene tower is 0.01wt% to 0.10wt%; The octene content in the side-line extracted stream is 0.05 wt% to 0.15 wt%.

7. The separation method according to any one of claims 1 to 6, characterized in that In step (3), the heavy component logistics is stored in a heavy component storage tank and then transported to a filter for filtration via a delivery pump.

8. The separation method according to claim 7, characterized in that The pressure in the heavy component storage tank is 1.0-2.0 MPaG, the temperature is 30-50° C., and the jacket of the heavy component storage tank is passed with warm water at 30° C.-50° C.

9. The separation method according to claim 8, characterized in that The heavy component flow is filtered in a filter with a filtration accuracy of 1 to 10 μm; Preferably, the filter is selected from a quick-release filter bag filter.

10. The separation method according to any one of claims 1 to 9, characterized in that The solvent separation device adopts membrane separation, and the decene and C 10 The content of the above olefin components is 0.1wt% to 0.5wt%; Preferably, the operating pressure in the solvent separation device is 3.0 MPaG to 6.0 MPaG, and the operating temperature is 30°C to 50°C.

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