Process and apparatus for the co-production of alpha-olefins by ethylene oligomerization

Abstract

The application provides a method for ethylene oligomerization to co-produce alpha-olefins, comprising the following steps: step a), first oligomerization of ethylene under the action of a first catalyst to obtain a first material; step b), second oligomerization of the first material under the action of a second catalyst and an oligomerization inhibitor to obtain a second material; and step c), separation of the second material after quenching to obtain 1-butene, 1-hexene and 1-octene. Experimental results show that the process for ethylene dimerization and tetramerization to produce alpha-olefins can greatly improve the catalytic activity of the catalyst and the conversion efficiency of ethylene, the activity of tetramerization is 2500-3700 kg / gCr·h, the activity of dimerization is 60-110 kg / gTi·h, and the conversion efficiency of ethylene is above 95%.

Description

Technical Field

[0001] This invention relates to the field of homogeneous catalysis technology, specifically a method and apparatus for the oligomerization of ethylene to co-produce α-olefins. Background Technology

[0002] Linear α-olefins are the most important comonomers for producing high-performance materials, and their properties and applications vary depending on their carbon chain. 1-Butene, 1-hexene, and 1-octene are representative linear α-olefins, mainly used in copolymerization with ethylene to produce low-density polyethylene (LLDPE) and high-density polyethylene (HDPE), thereby improving the mechanical properties, toughness, and transparency of olefin materials, such as crack resistance, tensile strength, rheological properties, etc.

[0003] Selective oligomerization of ethylene is currently the main production process for linear α-olefins. It uses ethylene as a raw material and produces α-olefins through oligomerization under the action of a catalyst. However, the selective oligomerization process of ethylene still has problems such as large equipment investment and low process efficiency. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method and apparatus for the co-production of α-olefins by ethylene oligomerization. The method provided by the present invention can co-produce 1-butene and 1-octene, with good selectivity, and can reduce costs and improve efficiency.

[0005] This invention provides a method for the oligomerization of ethylene to produce α-olefins, comprising the following steps:

[0006] Step a) Ethylene undergoes a first oligomerization under the action of a first catalyst to obtain a first material; the first catalyst includes a first main catalyst and a first co-catalyst, wherein the first main catalyst is selected from a chromium-based diphosphine amine ligand catalyst and the first co-catalyst is selected from alkylaluminoxane;

[0007] Step b) The first material undergoes a second oligomerization under the action of a second catalyst and a polymerization inhibitor to obtain a second material; the second catalyst includes a second main catalyst and a second co-catalyst, the second main catalyst is selected from titanate compounds, and the second co-catalyst is selected from alkyl aluminum; the polymerization inhibitor is selected from ether compounds;

[0008] Step c) After quenching the second material, separate it to obtain 1-butene, 1-hexene and 1-octene.

[0009] This invention combines ethylene tetramerization and ethylene dimerization processes in series. A combination of chromium-based diphosphine ligand catalysts and alkylaluminoxanes is used as the catalyst for ethylene tetramerization, while a combination of titanate compounds and alkylaluminum compounds is used as the catalyst for ethylene dimerization. Simultaneously, a polymerization inhibitor ether compound is added during the dimerization process. This allows for the simultaneous occurrence of ethylene tetramerization and ethylene dimerization under essentially the same pressure and temperature conditions, significantly improving ethylene conversion efficiency and simultaneously increasing the yield and selectivity of α-olefins (1-butene, 1-hexene, and 1-octene). Furthermore, the polymerization inhibitor effectively suppresses the high polymerization of ethylene to form polyethylene (PE), thus facilitating the subsequent separation of α-olefins.

[0010] In some specific implementations, the first main catalyst is selected from chromium-based bisphosphonium amine ligand (PNP) catalysts, which include PNP ligands and organic reagents of chromium. The ligands include, but are not limited to, one or more of cyclopentylamine-type bisphosphonium amine ligands, cyclohexylamine-type bisphosphonium amine ligands, and isopropylamine-type bisphosphonium amine ligands. The PNP ligands can be prepared by methods well known to those skilled in the art, such as those disclosed in patent CN202011438744.3, or purchased. The organic reagents of chromium include, but are not limited to, one or more of chromium isooctanoate, chromium trichloride, and chromium acetylacetone. The first co-catalyst is selected from methylaluminoxane or modified methylaluminoxane. In some specific implementations, the molar ratio of Cr in the first main catalyst to Al in the first co-catalyst is 1:300–700, preferably 1:(400–600), and more preferably 1:500.

[0011] In some specific implementations, the second catalyst contains, but is not limited to, one or more of tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate; the alkylaluminum contains, but is not limited to, one or more of trimethylaluminum, triethylaluminum, and triethylbutylaluminum; and the ether compound contains, but is not limited to, one or more of furan, pyrrole, and oxane. In some specific implementations, the molar ratio of titanium to the ether compound in the second main catalyst is 1:(2-5), preferably 1:(2.5-4.5), more preferably 1:(3-4); the molar ratio of titanium to aluminum in the second co-catalyst is 1:(3-8), preferably 1:(4-7), more preferably 1:(5-6). Adding a polymerization inhibitor in step b) can suppress the production of polyethylene, reduce the possibility of pipeline and equipment blockage, and thus reduce costs. In this invention, alkylaluminum can change the solid form of ethylene tetramerization, and the ether compound can effectively inhibit the polymerization reaction to produce PE, extending the operating cycle of the equipment.

[0012] Specifically, the present invention connects the reaction equipment of steps a) and b) in series, and simultaneously injects the ethylene raw material into the reaction equipment of step b) through the reaction equipment of step a). Then, a first catalyst, a second catalyst and a polymerization inhibitor are added respectively, and ethylene tetramerization and ethylene dimerization are carried out simultaneously. That is, in the initial reaction, step b) also includes ethylene.

[0013] In some specific implementations, the reaction temperature in step a) is 40℃~65℃, preferably 45℃~60℃, more preferably 50℃~55℃; the pressure is 2~6MPa, preferably 2.8~5.2MPa, more preferably 3.5~5MPa; and the time is 15~65min, preferably 20~50min, more preferably 25~40min. In some specific implementations, the molar ratio of the first catalyst (based on Cr in the main catalyst) to ethylene is 1:900~3600, preferably 1:1000~3500, more preferably 1:1500~3000.

[0014] In some specific implementations, the reaction temperature in step b) is 40℃~65℃, preferably 45℃~60℃, more preferably 50℃~55℃; the pressure is 2~6MPa, preferably 2.8~5.2MPa, more preferably 3.5~5MPa; and the time is 25~75min, preferably 30~60min, more preferably 35~55min. The second catalyst, based on titanium in the main catalyst, has a molar ratio to ethylene of 1:0.5~3.6, preferably 1:0.8~3.5, more preferably 1:1~3.

[0015] In some specific implementations, the solvent for reactions in steps a) and b) is an alkane that has a significant temperature difference with 1-butene, 1-hexene, and 1-octene, including but not limited to one or more of cyclohexane, methylcyclohexane, isooctane, and decane. In some specific implementations, ethylene is pre-mixed with the solvent to obtain a mixture, which is then mixed with a catalyst, etc. The mass ratio of ethylene in the mixture is preferably 0.15–0.45:1, preferably 0.2–0.43:1, and more preferably 0.25–0.4:1.

[0016] After the reaction is complete, the resulting reaction product is quenched. In some specific implementations, the quencher is a high-boiling-point alcohol, including but not limited to one or more of octanol, decanol, glycerol, butanediol, and glycerol. In some specific implementations, the molar ratio of the quencher to the second cocatalyst is 1 to 3:1, preferably 1.5 to 2.5:1.

[0017] After quenching, the obtained materials are sequentially separated to obtain butene, hexene, and octene. Specifically, the obtained materials are first filtered to remove the generated polyethylene; then flash evaporation is performed to separate and recycle the waste catalyst; then distillation is performed to separate and recycle ethylene; then distillation is performed to separate butene; then distillation is performed to separate hexene; then distillation is performed to separate the solvent; and finally distillation is performed to separate octene. This application does not impose special restrictions on the parameters of each distillation step; those skilled in the art can select them according to the different boiling points and other properties of each substance.

[0018] In some specific implementations, each step of the process, such as the transfer of reaction equipment and materials, including pipelines, is kept at a temperature controlled between 45℃ and 65℃ to prevent polymer precipitation. Experimental results show that the process for producing α-olefins through ethylene dimerization and tetramerization provided by this invention can significantly improve the catalytic activity of the catalyst and the conversion efficiency of ethylene. The activity for tetramerization is 2500–3700 kg / gCr·h, and the activity for dimerization is 60–110 kg / gTi·h, with an ethylene conversion efficiency of over 95%. The process provided in this application has a cycle time of over 2200 hours; the selectivity for 1-butene is over 94%, the selectivity for 1-hexene is over 92%, the selectivity for 1-octene is over 68%, and the total PE content is less than 0.05%.

[0019] This application also provides an apparatus for the co-production of α-olefins by ethylene oligomerization, including a reaction unit and a separation unit connected to the outlet of the reaction unit;

[0020] The reaction unit includes a reaction vessel, a buffer vessel connected to the outlet of the reaction vessel, and a quenching vessel connected to the outlet of the buffer vessel; the reaction vessel is provided with an ethylene feedstock inlet, a solvent inlet, a first main catalyst inlet, and a first co-catalyst inlet; the buffer vessel is provided with a solvent inlet, a second main catalyst inlet, a second co-catalyst inlet, and a polymerization inhibitor inlet;

[0021] The first main catalyst and the second main catalyst are different, as are the first co-catalyst and the second co-catalyst.

[0022] The apparatus for the co-production of α-olefins by ethylene oligomerization provided by this invention connects an ethylene tetramerization reactor and a buffer reactor for ethylene tetramerization and dimerization in series, allowing simultaneous ethylene tetramerization and dimerization under essentially the same conditions. This significantly improves the conversion efficiency of ethylene and also enhances the yield and selectivity of α-olefins (1-butene, 1-hexene, and 1-octene). Furthermore, the apparatus provided by this invention enables a continuous process, greatly reducing operating costs.

[0023] In some specific implementations, the ethylene feedstock inlet and solvent inlet in the reactor are combined into one port. The ethylene feedstock and solvent are first mixed, and then fed into the reactor through the same inlet. Similarly, other materials, such as the first main catalyst, the first co-catalyst, the second main catalyst, the second co-catalyst, and polymerization inhibitors, can be mixed with the solvent before entering the reactor or buffer vessel.

[0024] In some specific implementations, the buffer vessel is connected via an overflow pipeline located in the middle of the reactor.

[0025] In some specific implementations, the quenching vessel is connected to the buffer vessel via a discharge pipeline located at the bottom of the buffer vessel.

[0026] In some specific implementations, the reaction unit further includes a raw material purification system connected to the ethylene raw material inlet of the reactor, for purifying the ethylene raw material;

[0027] In some specific implementations, the separation unit includes a filter, a flash evaporation system, an ethylene recovery tower, a butene distillation tower, a hexene distillation tower, a solvent recovery tower, and an octene distillation tower connected in series. Specifically, the separation unit includes:

[0028] A filter connected to the outlet of the quenching vessel;

[0029] A flash tank connected to the outlet of the filter;

[0030] An ethylene recovery tower connected to the outlet of the flash tank;

[0031] A butene distillation column connected to the bottom outlet of the ethylene recovery column;

[0032] A hexene distillation column connected to the bottom outlet of the butene distillation column;

[0033] A solvent recovery tower connected to the bottom outlet of the hexene distillation column;

[0034] An octene distillation column connected to the bottom outlet of the statistical recovery column.

[0035] In the apparatus provided in this application, ethylene dimerization and ethylene tetramerization share a single separation device, reducing equipment investment and separation energy consumption. This application separates spent catalyst using a flash tank, reducing the separation difficulty of the separation system, improving product purity, and collecting catalysts containing metals Ti, Cr, and Al, thus reducing pollution.

[0036] In some specific implementations, a heat preservation device is also included to keep the reaction unit and separation unit warm. In the process provided in this application, the reaction temperatures of ethylene dimerization and ethylene tetramerization are both between 40℃ and 65℃, similar to the temperatures of the reaction unit, separation unit, and connecting pipelines. Heat extraction from the reactor alone is sufficient for pipeline insulation, eliminating the need for additional insulation and thus reducing equipment investment and energy consumption of the public system. Furthermore, this application uses a buffer reactor for ethylene dimerization, utilizing inhibitors to suppress the reaction and produce PE. This makes it easier for the reaction system to enter the separation unit for separation, extending the reaction cycle and reducing the possibility of pipeline and equipment blockage, thereby lowering costs.

[0037] This invention combines ethylene tetramerization and ethylene dimerization processes in series. A combination of chromium-based diphosphine ligand catalysts and alkylaluminoxanes is used as the catalyst for ethylene tetramerization, while a combination of titanate compounds and alkylaluminum compounds is used as the catalyst for ethylene dimerization. Simultaneously, a polymerization inhibitor ether compound is added during dimerization. This allows for the simultaneous occurrence of ethylene tetramerization and dimerization under essentially the same pressure and temperature conditions, significantly improving ethylene conversion efficiency and simultaneously increasing the yield and selectivity of α-olefins (1-butene, 1-hexene, and 1-octene). Furthermore, the polymerization inhibitor effectively suppresses the high-polymerization of ethylene into polyethylene (PE), thus facilitating the subsequent separation of α-olefins. Experimental results show that the ethylene dimerization and tetramerization process for producing α-olefins provided by this invention significantly improves the catalytic activity of the catalyst and the ethylene conversion efficiency. The activity for tetramerization is 2500–3700 kg / gCr·h, and the activity for dimerization is 60–110 kg / gTi·h, with an ethylene conversion efficiency exceeding 95%. The process provided in this application has a running cycle of more than 2200 hours; the selectivity of 1-butene is more than 94%, the selectivity of 1-hexene is more than 92%, the selectivity of 1-octene is more than 68%, and the total PE content is less than 0.05%. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the apparatus for the co-production of α-olefins by ethylene oligomerization, as provided in the embodiments of this application. Detailed Implementation

[0039] The following examples further illustrate the method and apparatus for the co-production of α-olefins by ethylene oligomerization according to the present invention.

[0040] Example 1

[0041] See Figure 1 , Figure 1 This is a schematic diagram of the apparatus for the co-production of α-olefins by ethylene oligomerization, as provided in the embodiments of this application.

[0042] The apparatus for the co-production of α-olefins by ethylene oligomerization provided in this application includes a reaction unit 1 and a separation unit 2 connected to the outlet of the reaction unit 1. The reaction unit 1 is used for selective oligomerization of ethylene to obtain different α-olefins, and the separation unit 2 is used to separate the different α-olefins.

[0043] Reaction unit 1 includes a reactor 11, which is used to catalyze the first oligomerization reaction of ethylene, mainly for ethylene tetramerization. The reactor 11 is equipped with an ethylene feedstock inlet, a solvent inlet, a main catalyst inlet, and a co-catalyst inlet.

[0044] Reaction unit 1 includes a buffer vessel 12 connected in series with the reactor 11, i.e., the inlet of the buffer vessel 12 is connected to the outlet of the reactor 11. It is used to catalyze a second oligomerization reaction of the material after the reaction in reactor 11, including tetramerization and dimerization, thereby obtaining different α-olefins. The buffer vessel 12 is provided with a solvent inlet, a main catalyst inlet, a co-catalyst inlet, and a polymerization inhibitor inlet. In some specific implementations, the buffer vessel 12 is connected to the reactor 11 via an overflow line. In some specific implementations, the overflow line is located in the middle of the reactor 11.

[0045] The reaction unit 1 also includes a quenching vessel 13 connected in series with the buffer vessel 12, i.e., the inlet of the quenching vessel 13 is connected to the outlet of the buffer vessel 12, for quenching reaction products and reducing polymer formation. The quenching vessel 13 is provided with a quenching agent inlet. In some specific implementations, the quenching vessel 13 is connected to the outlet at the bottom of the buffer vessel 12.

[0046] The separation unit 1 includes a filter 21, a flash evaporation system 22, an ethylene recovery tower 23, a butene distillation tower 24, a hexene distillation tower 25, a solvent recovery tower 26, and an octene distillation tower 27 connected in series. The reaction material in the quenching vessel 13 passes through the filter 21, flash evaporation system 22, ethylene recovery tower 23, butene distillation tower 24, hexene distillation tower 25, solvent recovery tower 26, and octene distillation tower 27 in sequence to achieve the recovery and reuse of catalyst, ethylene, and solvent, while obtaining α-olefins such as butene, hexene, and octene.

[0047] In some specific implementations, reaction unit 1 also includes a raw material purification system (not shown in the figure), which is connected to the feed inlets of reaction vessel 11, buffer vessel 12 and quenching vessel 13 respectively, for the purification of raw materials.

[0048] In some specific implementations, the device further includes a heat preservation unit (not shown in the figure) for heat preservation of reaction unit 1 and separation unit 2 to prevent oligomer precipitation.

[0049] The method of using the device is as follows:

[0050] Ethylene feedstock, first solvent, first main catalyst and first co-catalyst are fed into reactor 11 for reaction, and the material obtained after the reaction is completed is fed into buffer reactor 12.

[0051] The second solvent, the second main catalyst, the second co-catalyst, and the polymerization inhibitor are added to the buffer vessel 12 and mixed with the material obtained from the reaction vessel 11. The reaction continues, and after the reaction is completed, the material enters the quenching vessel 13 through the bottom outlet. The material is quenched by the quenching agent and enters the separation unit. The material passes through the filter 21 to remove PE, the flash evaporation system 22 to filter and recover the catalyst, the ethylene recovery tower 23 to recover ethylene, the butene distillation tower 24 to collect butene products, the hexene distillation tower 25 to collect hexene products, the solvent recovery tower 26 to recover the solvent, and the octene distillation tower 27 to collect the octene component.

[0052] Examples 2-6

[0053] Using the apparatus provided in Example 1, the ethylene oligomerization and co-production of α-olefins were carried out according to the parameters shown in Table 1. The specific steps are as follows:

[0054] Ethylene and solvent were introduced into reactor 11 and buffer reactor 12 at a mass ratio of 40%. The pressure in reactor 11 and buffer reactor 12 was stabilized at 4.5 MPa and the temperature at 50°C, with the liquid level in reactor 11 just reaching the overflow port. The first main catalyst and the first co-catalyst were introduced into reactor 11 along with the solvent. The first main catalyst was a chromium-based bisphosphonium amine ligand (PNP) catalyst, with the ligands listed in Table 1, and the organic reagent for chromium being chromium isooctanoate. The second main catalyst, polymerization inhibitor, and second co-catalyst were introduced into buffer reactor 12 along with the solvent. The temperature of the reactor and buffer reactor was controlled by a temperature and pressure insulation unit to carry out ethylene tetramerization and ethylene dimerization reactions under stable temperature and pressure. The residence time of the materials in reactor 11 was 30 min. The overflow line was then opened, and the reaction system entered buffer reactor 12 to continue the reaction. The residence time in buffer reactor 12 was controlled to be 45 min. The mixture after the two reactions entered a quenching reactor for quenching. The quenching agent was decanol, with a molar ratio of 1.2:1 to the co-catalyst Al. After quenching, the mixture enters a filter to remove PE, and then enters a flash evaporation system to flash the product out. The remaining waste catalyst is collected from the bottom of the flash tank for treatment. The product then enters an ethylene recovery tower, a butene distillation tower, a hexene distillation tower, a solvent recovery tower, and an octene distillation tower for component separation to obtain high-purity 1-butene, 1-hexene, and 1-octene. Ethylene and solvent are recovered and reused.

[0055] The device operated continuously for over 2000 hours following the above procedure. The device operated for a long time, was safe and stable, and no special accidents occurred. After shutdown, the pipelines and tanks were removed, and no large amount of solid deposits or blockages were found. Only a small amount of solids were generated in the filter.

[0056] The collected products were subjected to gas phase analysis to calculate the catalytic activity of ethylene dimerization, the catalytic activity of ethylene tetramerization, the selectivity of 1-butene, the selectivity of 1-hexene, the selectivity of 1-octene, and the content of PE. The results are shown in Table 1, which presents the parameters, conditions, and operating effects provided in Examples 2 to 5 of this invention.

[0057] Table 1 shows the parameter conditions and operational effects provided in Examples 2-5 of the present invention.

[0058]

[0059] In Examples 2-5, the first catalyst was prepared according to the following method:

[0060] Diphenylphosphine chloride, cyclopentylamine / isopropylamine / cyclohexylamine, dichloromethane, and triethylamine were mixed and stirred at -20°C, filtered, and recrystallized to obtain a cyclopentylamine / isopropylamine / cyclohexylamine type PNP ligand; chromium isooctanoate and the PNP ligand were mixed in a solvent according to the proportions in Table 1 to obtain the first catalyst.

[0061] Comparative Examples 1-4

[0062] Referring to Table 2, which shows the parameters and operating results of Comparative Examples 1-4 of this invention, continuous ethylene dimerization and tetramerization reactions were carried out using the reaction and separation units of the above-mentioned apparatus. With other process conditions remaining the same, the apparatus operating cycle was less than 1000 hours, exhibiting low reactivity, poor selectivity, and high PE content. Similarly, without the use of polymerization inhibitors, the operating cycle was only 1250 hours, with poor selectivity and high PE content. After disassembling all pipelines, reactors, and tanks, it was found that a large amount of deposited polymer had accumulated, clogging the discharge valves and pipelines. Cleaning the apparatus and pipelines required significant manpower and resources.

[0063] Table 2 shows the parameter conditions and operational effects provided in Comparative Examples 1-4 of this invention.

[0064]

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for the oligomerization of ethylene to produce α-olefins, comprising the following steps: Step a) Ethylene undergoes a first oligomerization under the action of a first catalyst to obtain a first material; the first catalyst includes a first main catalyst and a first co-catalyst, the first main catalyst is selected from a chromium-based diphosphine ligand catalyst, and the first co-catalyst is selected from alkylaluminoxane; in the first main catalyst, the ligand is selected from one or more of cyclopentylamine-type diphosphine ligand, cyclohexylamine-type diphosphine ligand, and isopropylamine-type diphosphine ligand; The first main catalyst is prepared according to the following method: Diphenylphosphine chloride, an amine compound, dichloromethane, and triethylamine were mixed and stirred at -20°C, filtered, and recrystallized to obtain the ligand; the amine compound was selected from cyclopentylamine, isopropylamine, or cyclohexylamine. Chromium isooctanoate is mixed with the ligand in a solvent to obtain a first catalyst; Step b) The first material undergoes a second oligomerization under the action of a second catalyst and a polymerization inhibitor to obtain a second material; the second catalyst includes a second main catalyst and a second co-catalyst, the second main catalyst is selected from titanate compounds, and the second co-catalyst is selected from alkyl aluminum; the polymerization inhibitor is selected from ether compounds; the titanate compound is selected from one or more of tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate; Step c) After quenching the second material, separate it to obtain 1-butene, 1-hexene and 1-octene.

2. The method according to claim 1, characterized in that, The molar concentration of the first catalyst is 2~8 μmol / mL; the molar concentration of the second catalyst is 1000~3500 μmol / mL.

3. The method according to claim 1, characterized in that, The first cocatalyst is selected from methylaluminoxane or modified methylaluminoxane; The molar ratio of Cr in the first main catalyst to Al in the first co-catalyst is 1:300~700; The alkylaluminum is selected from one or more of trimethylaluminum, triethylaluminum, and triethylbutylaluminum; The ether compound is selected from one or more of furans and oxanes; The molar ratio of titanium to ether compound in the second main catalyst is 1:2~5; The molar ratio of titanium in the second main catalyst to aluminum in the second co-catalyst is 1:(3~8).

4. The method according to any one of claims 1 to 3, characterized in that, The solvents used in steps a) and b) are independently selected from one or more of cyclohexane, methylcyclohexane, isooctane, and decane; The quenching agent in step c) is selected from one or more of octanol, decanol, glycerol, butanediol, and glycerol.

5. The method according to claim 4, characterized in that, The molar ratio of the quencher to the second co-catalyst is 1~3:

1.

6. The method according to any one of claims 1 to 3, characterized in that, The reaction temperature in step a) is 40℃~65℃, the pressure is 2~6MPa, and the time is 15~65min; The reaction temperature in step b) is 40℃~65℃, the pressure is 2~6MPa, and the time is 25~75min.

7. The method according to claim 6, characterized in that, Step c) specifically includes: After quenching the second material, polyethylene, catalyst, ethylene, butene, hexene, solvent and octene are separated in sequence.

Images