Method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes

Abstract

The present invention relates to the field of chemical separation technology and discloses a method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes, comprising the following steps: S1. contacting the mixture with Cu(BF4)2DPDS to obtain a Cu(BF4)2DPDS material that adsorbs the three-component C2-C4 olefins; S2. desorbing the olefin components adsorbed by the Cu(BF4)2DPDS material to obtain a mixed olefin component; S3. contacting the mixed olefin component obtained in S2 with a porous carbon adsorbent to separate high-purity ethylene gas. The present invention proposes for the first time a two-stage purification method to separate high-purity ethylene gas from the six-component C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 The olefins and alkanes in the mixture are first separated, and then the olefins are subjected to secondary separation and purification, thereby achieving the preparation of ultra-high purity (99.99%) C2H4 products from the six-component mixture.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical separation, and in particular relates to a method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes. Background Art

[0002] Ethylene (C2H4) is an important raw material for the petrochemical industry. It has a relatively active chemical property and is widely used in petrochemicals, energy and other important fields. C2H4 mainly comes from naphtha cracking. The cracking products include ethylene (C2H4), ethane (C2H6), propylene (C3H6), propane (C3H8), n-butene (n-C4H8), n-butane (n-C4H 10 ) and so on. Among them, ethylene is known as the "mother of the petrochemical industry" and is one of the world's largest-produced chemicals. Its downstream products such as polyethylene, styrene, styrene-butadiene rubber, etc. are widely used in the fields of medicine, textiles, machinery, etc.; China's annual production of ethylene (C2H4) has exceeded 170 million tons, but it is still in short supply, and high-purity gas ethylene still relies on imports. At present, the production of ethylene in industry is mainly separated and prepared from the low-carbon hydrocarbon mixture of naphtha cracking. The impurities in the cracking gas will poison the catalyst for polyethylene production, resulting in a decrease in the yield and purity of downstream products. Therefore, the task of separating the six-component mixture of C2-C4 olefins / alkanes and obtaining high-purity ethylene is urgent. At present, the separation of ethylene from low-carbon hydrocarbons is mainly focused on the traditional process of low-temperature distillation. In comparison, adsorption separation technology is an energy-saving and efficient gas separation technology with outstanding advantages such as low energy consumption, high product purity, simple process flow, and small amplification effect. It has good industrial application prospects.

[0003] However, ethylene / ethane, propylene / propane and n-butene / n-butane molecules are different in size, shape (C2H4, C2H6, C3H6, C3H8, n-C4H8, n-C4H 10 , ) and physical properties (the boiling points of C2H4, C2H6, C3H6, C3H8, n-C4H8, and n-C4H8 are 169.4K, 184.4K, 225.3K, 230.94K, 266.9K, and 272.6K, respectively), make the separation of olefins and alkanes a huge challenge in industry. Therefore, for C2H4 / C2H6 (50 / 50), C3H6 / C3H8 (50 / 50), and n-C4H8 / n-C4H 10Under the condition of binary mixture of (50 / 50), it is also very challenging to selectively capture olefins and reject alkanes with high efficiency. Currently, most of the materials reported can only achieve single C2H4 / C2H6 or C3H6 / C3H8 and n-C4H8 / n-C4H 10 There are few adsorption separation materials that can efficiently separate C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 There is no material that can directly purify ultra-high purity ethylene from a six-component mixture of such a multi-component mixture. Summary of the Invention

[0004] The present invention discloses a method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes, which solves the problem in the prior art that no material can directly purify ultra-high-purity ethylene from such a multi-component mixture.

[0005] The method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes specifically comprises the following steps:

[0006] S1. The mixture is contacted with Cu(BF4)2DPDS to obtain a Cu(BF4)2DPDS material adsorbing C2-C4 three-component olefins;

[0007] S2. The olefin component adsorbed by the Cu(BF4)2DPDS material is derived to obtain a mixed olefin component;

[0008] S3. The mixed olefin component obtained in S2 is contacted with a porous carbon adsorbent to separate high-purity ethylene gas.

[0009] Preferably, the preparation method of Cu(BF4)2DPDS is: 2+ , 4,4-bipyridyl disulfide and BF4 - Dissolve in methanol, stir and react at room temperature, filter and wash, and then perform vacuum activation to obtain Cu(BF4)2DPDS.

[0010] Preferably, the porous carbon adsorbent in S3 is a porous carbon adsorbent that is sintered at 700-900° C. using a potassium-containing compound as a pore-forming agent.

[0011] Preferably, the contacting mode of the mixture in S1 and the Cu(BF4)2DPDS is any one of fixed bed adsorption, fluidized bed adsorption and moving bed adsorption.

[0012] Preferably, when the contacting mode of the mixture and the Cu(BF4)2DPDS is fixed bed adsorption, the steps include:

[0013] (1) allowing the mixture to enter a fixed bed adsorption column filled with Cu(BF4)2DPDS to obtain a bed layer enriched with olefin components, and purging and desorbing the bed layer enriched with olefin components to obtain an olefin gas mixture;

[0014] (2) The obtained olefin gas mixture is passed into a fixed bed adsorption column filled with a porous carbon adsorbent, and the gas that preferentially penetrates the bed is collected from the outlet of the adsorption column to obtain ultra-high purity ethylene gas.

[0015] Preferably, the gas used in the purge desorption in (1) is nitrogen or an inert gas.

[0016] Preferably, the mixture is hexavalent C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 Mixed gas.

[0017] Preferably, the mixture is an equal volume ratio of six elements C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 Mixed gas.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention proposes a two-stage purification method for the first time, from six components C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 The olefins and alkanes in the mixture are first separated, and then the olefins are secondary separated and purified in the second step, realizing the separation of six components C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 Ultra-high purity (99.99%) C2H4 product was directly purified from the mixture.

[0020] 2. The adsorbent Cu(BF4)2DPDS uses a bidentate pyridine group with strong aromatic properties as an organic ligand and a new functional anion BF4 - As a pillar, it forms a new type of metal organic framework (MOFs) adsorbent with self-assembly and positioning with copper as a metal node, and has a one-dimensional through-the-hole flexible channel. Its suitable pore size and flexible and controllable pore environment not only show the selective adsorption of olefin molecules through the characteristic of opening the door in response to unsaturated π bonds, but also show the repulsive effect of the framework on alkane molecules. When the olefin opens the internal pores of the adsorbent, the pores reach the appropriate pore size, and with the help of the benzene rings in the pores and the functional pillar BF4 - The olefins were selectively adsorbed, the alkane molecules were repelled inside the pores, the olefins were selectively and efficiently captured, and the olefins were enriched in the adsorption material column, thereby achieving the separation of olefins and alkanes in the six components.

[0021] 3. Adsorbent GBC-900 is a granular carbon adsorbent obtained by burning renewable bamboo. It is a porous material fired at 700-900℃ with K2CO3 as pore-forming agent. Its pore size distribution is After Cu(BF4)2DPDS is saturated with adsorption, GBC-900 is added to the dynamic breakthrough pipeline to act as a second-stage adsorption column. The olefins enriched on the Cu(BF4)2DPDS are purged with He at a certain temperature. The porous carbon GBC-900, due to its different effects on different carbon chain olefins, can separate C2H4, C3H6 and n-C4H8. At the end of the pipeline, C2H4 is preferentially blown out of the pipeline. At the end of the pipeline, ultra-high purity (99.99%) C2H4 can be collected, and the blown C3H6 and n-C4H8 are adsorbed in the GBC-900.

[0022] 4. The present invention has the ability to highly selectively separate olefins / alkanes from a six-component gas mixture, exhibit excellent breakthrough cycle stability, and produce ultra-high-purity ethylene. This represents a novel approach in industrial adsorption separation technologies such as PSA and VS, thereby replacing traditional industrial ethylene separation technologies that require high energy consumption, such as solvent extraction or cryogenic distillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a picture of the actual finished product of the Cu(BF4)2DPDS material obtained in Example 1;

[0024] Figure 2 This is a picture of the physical finished product of the GBC-900 material obtained in Example 1;

[0025] Figure 3 The adsorption isotherms of Cu(BF4)2DPDS material obtained in Example 1 for C2H4 and C2H6 at 298K;

[0026] Figure 4 The adsorption isotherms of Cu(BF4)2DPDS material obtained in Example 1 for C3H6 and C3H8 at 298K;

[0027] Figure 5 The Cu(BF4)2DPDS material obtained in Example 1 was subjected to the reaction of n-C4H8 and n-C4H at 298K. 10 Adsorption isotherm of

[0028] Figure 6 The adsorption isotherms of GBC-900 material obtained in Example 1 for C2H4, C3H6 and n-C4H8 at 298K;

[0029] Figure 7The dynamic penetration and desorption curves of the Cu(BF4)2DPDS material obtained in Example 2 for the hexavalent mixture at 298K (a), and the dynamic penetration and desorption curves of the GBC-900 material for C2H4, C3H6 and n-C4H8 (b);

[0030] Figure 8 A roadmap for the preparation of Cu(BF4)2DPDS materials;

[0031] Figure 9 A roadmap for preparing GBC-900 materials;

[0032] Figure 10 The present invention provides a schematic flow diagram of a method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes. DETAILED DESCRIPTION

[0033] The following will be combined with specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] The experimental methods described in the examples of the present invention are conventional methods unless otherwise specified. The materials and reagents used are all commercially available unless otherwise specified.

[0035] Example 1

[0036] Cu(BF4)2DPDS was synthesized by the method disclosed in Example 1 of Chinese Patent CN 116003809A. The finished product is shown in the figure below. Figure 1 shown.

[0037] A method for preparing a metal organic framework material comprises the following steps:

[0038] 0.2 mmol Cu(BF4)2·xH2O was dissolved in 5 mL H2O, and 0.4 mmol dipyridyl disulfide (DPDS) was dissolved in 20 mL methanol. The two were mixed and stirred at room temperature at 25°C for 48 h. The resulting slurry was filtered and activated under vacuum at 60°C for 24 h to obtain the Cu(BF4)2DPDS metal organic framework material. See the preparation route for details. Figure 8 .

[0039] The porous carbon adsorbent is prepared using potassium compound K2CO3 as a pore-forming agent. The following takes GBC-900 as an example. The actual finished product is shown in the figure below. Figure 2 The preparation route is shown in Figure 9 .

[0040] The specific preparation method is as follows: first, place the bamboo in the air for 1 month until there is no moisture on the surface, then cut the bamboo into 2 cm long bamboo segments, place the bamboo segments in a tube furnace (tube furnace model is BTF-1200C, produced by Anhui Beiyike Equipment Technology Co., Ltd.), introduce Ar into the tube furnace, and heat at a heating rate of 5°C / min, and maintain it at 500°C for 40 minutes. After the sample cools to room temperature, the cooled sample and the pore-forming agent are mixed in a mass ratio of 1:1, and then placed in the tube furnace, heated to 700°C at a heating rate of 5°C / min, and maintained for 1 hour to obtain a carbonized sample, which is washed three times with a 70% sulfuric acid solution, then washed with water until neutral, and finally vacuum dried at 60°C for 12 hours to obtain GBC-900.

[0041] The pore size and pore environment of porous materials can be precisely controlled. When Cu(BF4)2DPDS comes into contact with olefin molecules, the pores automatically open and the pore size increases, allowing olefin molecules to enter and adsorb. The adsorption isotherms of Cu(BF4)2DPDS for ethylene, ethane, propylene, propane, n-butene, and n-butane at 298K are tested. Figures 3-5 As shown; and the adsorption isotherms of GBC-900 for ethylene, propylene and n-butene, as shown Figure 6 shown.

[0042] After the material synthesis, Cu(BF4)2DPDS and GBC-900 were degassed and activated, and the adsorption isotherms of Cu(BF4)2DPDS for ethylene, ethane, propylene, propane, n-butene and n-butane at 298K, as well as the adsorption isotherms of GBC-900 for ethylene, propylene and n-butene were tested using ASAP 3Flex adsorption instrument.

[0043] Example 2

[0044] At 25 °C and 1.0 bar, the hexavalent mixture C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 The mixture flowed through the Cu(BF4)2DPDS adsorption column at a flow rate of 1.0 mL / min, and C2H6 / C3H8 / n-C4H was obtained at the end of the adsorption column. 10The mixed gas, C2H4 / C3H6 / n-C4H8 mixed gas is enriched in the Cu(BF4)2DPDS adsorption column. When the adsorption column reaches adsorption equilibrium, the gas injection is stopped. After the gas injection is stopped, a GBC-900 adsorption column is connected to the rear end of the Cu(BF4)2DPDS adsorption column. At 80°C, the Cu(BF4)2DPDS adsorption column enriched with olefins is purged with helium at a flow rate of 1.0mL / min. The purged olefin mixture flows through the GBC-900 adsorption column, the temperature of which is controlled at 80°C and the adsorption pressure is 1.0bar. Ethylene preferentially penetrates the bed layer. The gas that preferentially flows out from the end of the GBC-900 adsorption column is collected to obtain ultra-high purity ethylene gas (>99.99%). See the flow diagram of the method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes. Figure 10 . Figure 7 Figure 3 shows the dynamic penetration and desorption curves of Cu(BF4)2DPDS material for a hexavalent mixture at 298K (a), and the dynamic penetration and desorption curves of GBC-900 material for C2H4, C3H6 and n-C4H8 (b). It can be seen from the figure that Cu(BF4)2DPDS only has an adsorption effect on the olefin components C2H4 / C3H6 / n-C4H8, and GBC-900 can separate C2H4 from the mixed olefin components C2H4 / C3H6 / n-C4H8.

[0045] Comparative Example 1

[0046] The Cu(BF4)2DPDS material obtained in Example 1 was placed in a 10 cm fixed bed adsorption column:

[0047] At 25 °C and 1.0 bar, the hexavalent mixture C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 The mixture flowed through the Cu(BF4)2DPDS adsorption column at a flow rate of 1.0 mL / min, and C2H6 / C3H8 / n-C4H was obtained at the end of the adsorption column. 10 The mixed gas, C2H4 / C3H6 / n-C4H8 mixed gas is enriched in the Cu(BF4)2DPDS adsorption column, and the gas injection is stopped when the adsorption column reaches adsorption equilibrium.

[0048] Comparative Example 2

[0049] The GBC-900 material obtained in Example 1 was loaded into a 10 cm fixed bed adsorption column:

[0050] At 25 °C and 1.0 bar, the hexavalent mixture C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10The flow rate of 1.0 mL / min was passed through the GBC-900 adsorption column, and the hexavalent mixture C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H was obtained at the end of the adsorption column. 10 When the adsorption column reaches adsorption equilibrium, stop injecting gas.

[0051] From Example 2 and Comparative Examples 1 and 2, it can be seen that Comparative Example 1 only uses Cu(BF4)2DPDS and only obtains C2H6 / C3H8 / n-C4H 10 In the case of mixed gas, olefins could not be separated individually. In Comparative Example 2, only GBC-900 was used, which could not separate the components in the mixed gas.

[0052] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0053] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes, characterized in that The specific steps include: S1. The mixture was contacted with Cu(BF4)2DPDS to obtain Cu(BF4)2DPDS material adsorbing C2-C4 three-component olefins; S2. desorbing the olefin component adsorbed on the Cu(BF4)2DPDS material to obtain a mixed olefin component; S3. The mixed olefin component obtained in S2 is contacted with a porous carbon adsorbent to separate high-purity ethylene gas; The preparation method of Cu(BF4)2DPDS is as follows: 2+ , 4,4-bipyridyl disulfide and BF4 - Dissolve in methanol, stir and react at room temperature, filter and wash, and then perform vacuum activation to obtain Cu(BF4)2DPDS; The preparation method of the porous carbon adsorbent GBC-900 is specifically as follows: first, bamboo is placed in air for 1 month until there is no moisture on the surface, then the bamboo is cut into 2 cm long bamboo segments, the bamboo segments are placed in a tube furnace, Ar is introduced into the tube furnace, and heated at a heating rate of 5°C / min, and then heated to 500°C and maintained for 40 minutes. After the sample is cooled to room temperature, the cooled sample and the pore-forming agent are mixed in a mass ratio of 1:1, and then placed in the tube furnace again, and heated to 700°C at a heating rate of 5°C / min and maintained for 1 hour to obtain a carbonized sample, which is washed three times with a 70% sulfuric acid solution, then washed with water until neutral, and finally vacuum dried at 60°C for 12 hours to obtain the porous carbon adsorbent GBC-900; The contacting mode of the mixture in S1 and the Cu(BF4)2DPDS is any one of fixed bed adsorption, fluidized bed adsorption and moving bed adsorption; The mixture is hexavalent C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 Mixed gas.

2. The method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes according to claim 1, characterized in that: When the contact mode of the mixture and the Cu(BF4)2DPDS is fixed bed adsorption, the method comprises the following steps: (2) The mixture is allowed to enter a fixed bed adsorption column filled with Cu(BF4)2DPDS to obtain a bed layer enriched with olefin components, and the bed layer enriched with olefin components is purged and desorbed to obtain an olefin gas mixture; (2) The obtained olefin gas mixture is passed into a fixed bed adsorption column filled with a porous carbon adsorbent, and the gas that preferentially penetrates the bed is collected from the outlet of the adsorption column to obtain ultra-high purity ethylene gas.

3. The method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes according to claim 2, characterized in that: The gas used for the purge desorption described in (1) is nitrogen or an inert gas.

4. The method for separating ethylene from a six-component mixture of C2-C4 olefins / alkanes according to claim 1, characterized in that: The mixture is an equal volume ratio of six elements C2H4 / C2H6 / C3H6 / C3H8 / n-C4H8 / n-C4H 10 Mixed gas.

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