CN112745441A - Slurry polyethylene and preparation method and device thereof - Google Patents
Slurry polyethylene and preparation method and device thereof Download PDFInfo
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- CN112745441A CN112745441A CN201911043466.9A CN201911043466A CN112745441A CN 112745441 A CN112745441 A CN 112745441A CN 201911043466 A CN201911043466 A CN 201911043466A CN 112745441 A CN112745441 A CN 112745441A
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- -1 polyethylene Polymers 0.000 title claims abstract description 136
- 239000004698 Polyethylene Substances 0.000 title claims abstract description 135
- 229920000573 polyethylene Polymers 0.000 title claims abstract description 135
- 239000002002 slurry Substances 0.000 title claims abstract description 65
- 238000002360 preparation method Methods 0.000 title abstract description 9
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 72
- 239000007790 solid phase Substances 0.000 claims abstract description 63
- 239000000463 material Substances 0.000 claims abstract description 62
- 238000000034 method Methods 0.000 claims abstract description 40
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000005977 Ethylene Substances 0.000 claims abstract description 36
- 239000012071 phase Substances 0.000 claims abstract description 36
- 239000002904 solvent Substances 0.000 claims abstract description 31
- 238000000926 separation method Methods 0.000 claims abstract description 27
- 239000003054 catalyst Substances 0.000 claims abstract description 21
- 239000000178 monomer Substances 0.000 claims abstract description 20
- 238000001704 evaporation Methods 0.000 claims abstract description 17
- 230000008020 evaporation Effects 0.000 claims abstract description 16
- 239000001257 hydrogen Substances 0.000 claims abstract description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 11
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims abstract 2
- 238000007334 copolymerization reaction Methods 0.000 claims description 7
- 150000003384 small molecules Chemical class 0.000 claims description 4
- 238000007613 slurry method Methods 0.000 claims description 3
- 239000004711 α-olefin Substances 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000004821 distillation Methods 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000005265 energy consumption Methods 0.000 abstract description 4
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 description 32
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 10
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 8
- 239000000047 product Substances 0.000 description 8
- 239000007787 solid Substances 0.000 description 8
- 230000001276 controlling effect Effects 0.000 description 7
- 238000010992 reflux Methods 0.000 description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- LIKMAJRDDDTEIG-UHFFFAOYSA-N 1-hexene Chemical compound CCCCC=C LIKMAJRDDDTEIG-UHFFFAOYSA-N 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 239000001282 iso-butane Substances 0.000 description 3
- 239000001294 propane Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- KWKAKUADMBZCLK-UHFFFAOYSA-N 1-octene Chemical compound CCCCCCC=C KWKAKUADMBZCLK-UHFFFAOYSA-N 0.000 description 2
- WSSSPWUEQFSQQG-UHFFFAOYSA-N 4-methyl-1-pentene Chemical compound CC(C)CC=C WSSSPWUEQFSQQG-UHFFFAOYSA-N 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229920001903 high density polyethylene Polymers 0.000 description 2
- 239000004700 high-density polyethylene Substances 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 150000001338 aliphatic hydrocarbons Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- DUEPRVBVGDRKAG-UHFFFAOYSA-N carbofuran Chemical compound CNC(=O)OC1=CC=CC2=C1OC(C)(C)C2 DUEPRVBVGDRKAG-UHFFFAOYSA-N 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- TVMXDCGIABBOFY-UHFFFAOYSA-N n-Octanol Natural products CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- 229920013716 polyethylene resin Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000001577 simple distillation Methods 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F6/00—Post-polymerisation treatments
- C08F6/006—Removal of residual monomers by chemical reaction, e.g. scavenging
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Polymerisation Methods In General (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention relates to the technical field of slurry polyethylene, and discloses slurry polyethylene and a preparation method and a device thereof, wherein the method comprises the following steps: carrying out polymerization reaction on an ethylene monomer and an optional comonomer in the presence of hydrogen, a catalyst and a solvent to obtain polyethylene slurry; and carrying out solid phase concentration treatment on the polyethylene slurry to obtain a dilute phase material flow II and a material flow I rich in a solid phase, removing the solvent and the monomer from the material flow I rich in the solid phase to obtain polyethylene, and separating the dilute phase material flow II to obtain the soluble low-molecular-weight polyethylene. The method provided by the invention can obviously reduce the content of the soluble low molecular weight polyethylene in the polyethylene, effectively improve the purity and the service performance of the polyethylene product, and simultaneously reduce the energy consumption of flash evaporation and the cost of solvent separation.
Description
Technical Field
The invention relates to the technical field of slurry polyethylene, in particular to slurry polyethylene and a preparation method and a preparation device thereof.
Background
Slurry polymerisation processes are the main processes for the preparation of High Density Polyethylene (HDPE) in which ethylene is homopolymerised or copolymerised with other comonomers, usually in the presence of an aliphatic hydrocarbon solvent, under catalyst conditions of temperature and pressure, and in which the molecular weight of the polymer is controlled, usually by hydrogen, and the polyethylene slurry from the reactor is separated to obtain a polyethylene product having as low a moisture content as possible.
Hydrocarbons having 3 to 6 carbon atoms are generally used as solvents in the prior art. For hydrocarbons containing 3-5 carbon atoms, the polyethylene slurry is separated from the polymer by flash separation, i.e., by evaporating the solvent under reduced pressure. However, with this method, on the one hand, a large amount of energy is consumed for the vaporization of the solvent; on the other hand, soluble low molecular weight polymers (such as polyethylene wax) dissolved in the solvent can be separated out from the solvent in the flash evaporation process and attached to the surface of polyethylene particles, so that the polyethylene is easy to agglomerate in subsequent treatment, and meanwhile, the soluble low molecular weight polymers are easy to migrate, thereby affecting the service performance of the final polyethylene product.
Disclosure of Invention
The invention aims to solve the problems that the flash evaporation energy consumption is high, the content of soluble low molecular weight polyethylene in a polyethylene product is high and the use performance of a final product is influenced because the polyethylene slurry is directly subjected to flash evaporation separation in the prior art. A slurry polyethylene and a method and apparatus for making the same are provided.
In order to achieve the above object, a first aspect of the present invention provides a method for treating a slurry polyethylene slurry, the method comprising: carrying out solid phase concentration treatment on polyethylene slurry obtained by slurry polymerization to obtain a dilute phase material flow II and a material flow I rich in a solid phase, removing a solvent and a monomer from the material flow I rich in the solid phase to obtain polyethylene, and separating the dilute phase material flow II to obtain the soluble low-molecular-weight polyethylene.
A second aspect of the present invention provides a process for the preparation of polyethylene by slurry polymerization, the process comprising: carrying out polymerization reaction on an ethylene monomer and an optional comonomer in the presence of hydrogen, a catalyst and a solvent to obtain polyethylene slurry; and
and treating the polyethylene slurry according to the method to obtain the polyethylene.
A third aspect of the invention provides a slurry polyethylene prepared by the foregoing process.
The fourth aspect of the present invention provides an ethylene slurry polymerization apparatus comprising a polymerization reactor and a solid-phase concentration device which are communicated in this order, and a small molecule removal device and a separation device which are communicated with the solid-phase concentration device, wherein,
the polymerization reactor is used for homopolymerization or copolymerization of ethylene by a slurry method;
the solid phase concentration equipment is used for carrying out solid phase concentration treatment on the polyethylene slurry obtained by the polymerization reactor to obtain a dilute phase material flow II and a material flow I rich in a solid phase;
the micromolecule removing equipment is used for removing the solvent and the monomer in the solid-phase-rich material flow I to obtain polyethylene;
the separation equipment is used for separating the dilute phase material flow II to obtain the soluble low molecular weight polyethylene.
Through the technical scheme, the invention has the beneficial effects that:
according to the invention, the solid-phase concentration treatment is carried out on the polyethylene slurry in the process of preparing polyethylene by slurry polymerization, so that the content of soluble low-molecular-weight polyethylene in a polyethylene product is effectively reduced, the purity and the service performance of a final product are improved, and the energy consumption of flash evaporation and the separation cost of a solvent are reduced.
Drawings
FIG. 1 is a process flow diagram of a slurry polymerization process for producing polyethylene according to a preferred embodiment of the present invention.
Description of the reference numerals
1 polymerization reactor 2 solid phase concentration equipment 3 heat exchange equipment
4 flash evaporation equipment and 5 rectification dewaxing equipment
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The inventor of the present invention found in research that the flow ratio of the dilute phase stream II and the solid-rich stream I can be controlled by adjusting the discharge valve, the flow meter adjusting valve and the reflux pump, so as to control the content of the soluble low molecular weight polyethylene entering the solid-rich stream I, significantly reduce the content of the soluble low molecular weight polyethylene in the polyethylene product, and improve the purity and the service performance of the polyethylene product.
A first aspect of the invention provides a process for treating a slurry polyethylene slurry, the process comprising: carrying out solid phase concentration treatment on polyethylene slurry obtained by slurry polymerization to obtain a dilute phase material flow II and a material flow I rich in a solid phase, removing a solvent and a monomer from the material flow I rich in the solid phase to obtain polyethylene, and separating the dilute phase material flow II to obtain the soluble low-molecular-weight polyethylene. The soluble low molecular weight polyethylene is a low molecular weight polyethylene dissolved in a slurry.
Preferably, the flow ratio of the solid-rich stream I to the dilute-phase stream II is (1: 9) - (9: 1), so that the content of soluble low molecular weight polyethylene in the polyethylene is reduced by 10-90 wt% compared to the content of soluble low molecular weight polyethylene in the polyethylene obtained without the solid phase concentration treatment;
more preferably (1: 5) - (5: 1), particularly preferably (1: 2) - (2: 1), which is more advantageous for reducing the content of soluble low molecular weight polyethylene entering the solid-rich stream I to achieve effective removal of soluble low molecular weight polyethylene, if the flow ratio of the solid-rich stream I to the dilute-phase stream II is too high, the solid-rich stream I contains a large amount of soluble low molecular weight polyethylene, which affects the final product properties; if the flow ratio of the solid-phase-rich material flow I to the dilute-phase material flow II is too low, part of polyethylene particles enter the dilute-phase material flow II, so that the top outlet of solid-phase concentration equipment is easily blocked, and the removal of soluble low-molecular-weight polyethylene is not facilitated.
According to the invention, the solid phase concentration treatment is to control the two-phase material flow to a proper flow ratio by adjusting the discharge valve, the flow meter adjusting valve and the reflux pump, so that the content of the soluble low molecular weight polyethylene entering the material flow I rich in the solid phase can be effectively controlled, and the effective removal of the soluble low molecular weight polyethylene is realized.
Preferably, the solid-phase-rich material flow I is subjected to flash separation to remove the solvent and the monomer, so as to obtain polyethylene; and removing the soluble low molecular weight polyethylene from the dilute phase material flow II to obtain the soluble low molecular weight polyethylene, and recovering the solvent and the monomer.
In the invention, the flash separation conditions are selected in a wide range, preferably, the flash temperature is 30-120 ℃, and more preferably 35-100 ℃; the flash pressure is 0.05 to 2MPa, more preferably 0.05 to 1 MPa.
A second aspect of the present invention provides a process for the preparation of polyethylene by slurry polymerization, the process comprising: carrying out polymerization reaction on an ethylene monomer and an optional comonomer in the presence of hydrogen, a catalyst and a solvent to obtain polyethylene slurry; and
the polyethylene slurry is treated as described above to obtain a polyethylene having a soluble low molecular weight polyethylene content of less than 1.1 wt%.
Some embodiments of the invention provide that the polymerization conditions are such that a slurry polymerization of ethylene monomer and optional comonomer is achieved. Preferably, the polymerization conditions include: the polymerization temperature is 50-140 ℃, and more preferably 60-110 ℃; the polymerization pressure is 0.5 to 6MPa, more preferably 0.5 to 4.5 MPa; the reaction time is 0-5 h.
The present invention does not specifically limit the amounts of the materials for polymerization, such as monomers, catalysts and solvents, provided in the examples, and they may be added in the proportions specified in the process conditions for slurry polymerization of ethylene in the art.
According to the invention, the solvent is C3-C5Preferably, the solvent is selected from at least one of propane, n-butane, isobutane, n-pentane and isopentane, more preferably n-pentane.
According to the invention, the optional comonomer comprises an alpha-olefin, preferably comprising C4-C10Such as 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, more preferably 1-butene and 1-hexene, and particularly preferably 1-butene. Wherein the weight ratio of comonomer to ethylene is from 0.1 to 0.2.
In the present invention, the catalyst is not particularly limited, and may be various catalysts conventionally used in slurry polymerization of polyolefin in the art, for example, a titanium-based catalyst, a chromium-based catalyst, a single site catalyst, or the like, and preferably a titanium-based catalyst, for example, a BCE-type catalyst.
In a third aspect of the present invention, there is provided a slurry polyethylene prepared by the foregoing process, wherein the polyethylene has a low content of soluble low molecular weight polyethylene, the purity and performance of the product are greatly improved, and the obtained polyethylene is useful for the preparation of high performance polyethylene resins.
The fourth aspect of the present invention provides an ethylene slurry polymerization apparatus comprising a polymerization reactor and a solid-phase concentration device which are communicated in this order, and a small molecule removal device and a separation device which are communicated with the solid-phase concentration device, wherein,
the polymerization reactor is used for homopolymerization or copolymerization of ethylene by a slurry method;
the solid phase concentration equipment is used for carrying out solid phase concentration treatment on the polyethylene slurry obtained by the polymerization reactor to obtain a dilute phase material flow II and a material flow I rich in a solid phase;
the micromolecule removing equipment is used for removing the solvent and the monomers in the solid-phase-rich material flow I to obtain polyethylene with the content of soluble low-molecular-weight polyethylene being lower than 1.1 weight percent;
the separation equipment is used for separating the dilute phase material flow II to obtain the soluble low molecular weight polyethylene.
Preferably, the small molecule removal equipment is flash evaporation equipment, and the separation equipment is rectification dewaxing equipment.
Specifically, as shown in fig. 1, a raw material is fed from a feed inlet of a polymerization reactor 1, a discharge outlet of the polymerization reactor 1 is connected with a feed inlet of a solid phase concentration device 2 through a pipeline, a bottom outlet of the solid phase concentration device 2 is connected with a feed inlet of a flash evaporation device 4 through a pipeline and a heat exchange device 3, and a top outlet of the solid phase concentration device 2 is connected with a feed inlet of a rectification dewaxing device 5 through a pipeline.
The polymerization reactor is not particularly limited according to the apparatus provided by the present invention, and may be various polymerization reactors and the like conventionally used in the art, such as a continuous stirred tank reactor or a loop reactor.
In the present invention, the solid phase concentration apparatus is not particularly limited, and it may be various apparatuses for performing separation using density difference, which are conventionally used in the art, such as a hydrocyclone, a settling tank, and the like.
In the present invention, the combination of the heat exchange device and the flash evaporation device is not particularly limited, and it may be a section of jacketed flash evaporation pipe or a jacketed flash evaporation tank, i.e. heating and flash separation are performed in one device, or may be a heat exchange device and a flash evaporation device connected in series, i.e. heating and flash separation are performed in two devices, respectively. On the basis of the above disclosure, the person skilled in the art knows how to select a suitable device.
According to the invention, the rectification dewaxing device can be a rectification column or a simple distillation device. Those skilled in the art know that the appropriate selection is made according to the actual situation.
A preferred embodiment of the present invention is provided below in conjunction with the process flow diagram of FIG. 1 to illustrate the slurry polymerization process for producing polyethylene of the present invention.
As shown in fig. 1, in the presence of hydrogen, a catalyst and a solvent, introducing raw materials (including an ethylene monomer and an optional comonomer) into a polymerization reactor 1 to perform a polymerization reaction to obtain a polyethylene slurry, introducing the polyethylene slurry into a solid phase concentration device 2 to perform a solid phase concentration treatment to obtain a dilute phase material flow II and a solid phase-rich material flow I, respectively, introducing the solid phase-rich material flow I into a heat exchange device 3 to perform a heating treatment, then introducing the material flow obtained by the heating treatment into a flash evaporation device 4 to perform flash evaporation separation, and removing the solvent and the monomer to obtain polyethylene; introducing the dilute phase material flow II into a rectification dewaxing device 5 for removing the soluble low molecular weight polyethylene to obtain the soluble low molecular weight polyethylene, and recovering the solvent and the monomer.
The present invention will be described in detail below by way of examples. Unless otherwise specified, various raw materials used below are commercially available.
Ethylene: polymerization grade, Beijing Huayu Jinghui Jingcheng gas technology, Inc.;
comonomer (b): 1-butene, polymerization grade, gas technologies ltd, beijing, cijing hui, kyoto;
solvent: n-pentane, isobutane, propane, analytically pure, carbofuran;
catalyst: BCE type catalyst, beijing alda, a division of chinese petrochemical catalysts;
hydrogen gas: the high-purity hydrogen is obtained after dehydration and deoxidation treatment.
The pressures described herein are all expressed as gauge pressures unless otherwise specified.
In the following examples, the content of soluble low molecular weight polyethylene in the obtained polyethylene was tested according to the standard of GB/T5009.58-2003, specifically:
weighing about 2.00g of sample in a flask of a 250mL reflux condenser, adding 100mL of n-hexane, connecting a condensing tube, heating and refluxing for 2h in a water bath, immediately filtering by using quick qualitative filter paper, washing the filter and the sample by using a small amount of n-hexane, combining the washing liquid and the filtrate, then putting the n-hexane into a vial of a constant concentrator, concentrating and recovering the n-hexane, drying the residue at the temperature of 100 ℃ and 105 ℃ for 2h, cooling in a dryer for 30min, and weighing.
In the following examples, the process flow shown in fig. 1 was used unless otherwise specified.
Example 1
The method for preparing polyethylene by slurry polymerization comprises the following steps:
adding 100mg of BCE catalyst and 50L of n-pentane into a continuous stirring tank type reactor, firstly introducing hydrogen into the reactor, controlling the pressure to be 0.9MPa, continuously introducing ethylene to carry out ethylene homopolymerization, controlling the polymerization temperature to be 90 ℃, the polymerization pressure to be 1.2MPa and the polymerization time to be 3h, then emptying the reactor, continuously introducing mixed gas of ethylene and 1-butene, wherein the weight ratio of the 1-butene to the ethylene is 0.12, carrying out copolymerization reaction of the ethylene and the 1-butene, the polymerization temperature is 84 ℃, the polymerization pressure to be 0.5MPa and the polymerization time to be 1h, and obtaining polyethylene slurry;
and (3) separating the polyethylene slurry by adjusting a discharge valve, a flow meter adjusting valve and a reflux pump to obtain a dilute phase material flow II and a solid phase-rich material flow I, wherein the flow ratio of the solid phase-rich material flow I to the dilute phase material flow II is 1:1, then carrying out flash separation on the solid phase-rich material flow I, wherein the flash temperature is 80 ℃, and the flash pressure is 0.2MPa to obtain polyethylene, wherein the weight content of soluble low molecular weight polyethylene in the polyethylene is shown in Table 1.
Example 2
Example 2 was carried out using the same process flow as in example 1, except that the flow ratio of the solid-rich stream I to the dilute-phase stream II was 1:2, and the weight content of soluble low molecular weight polyethylene in the polyethylene is shown in table 1.
Example 3
Example 3 was carried out using the same process flow as in example 1, except that the flow ratio of the solid-rich stream I to the dilute-phase stream II was 2:1 and the weight content of soluble low molecular weight polyethylene in the polyethylene is given in table 1.
Example 4
The method for preparing polyethylene by slurry polymerization comprises the following steps:
adding 100mg of BCE catalyst and 50L of isobutane into a continuous stirring tank type reactor, firstly introducing hydrogen into the reactor, controlling the pressure to be 1.26MPa, continuously introducing ethylene to perform ethylene homopolymerization, wherein the polymerization temperature is 90 ℃, the polymerization pressure is 4.5MPa, and the polymerization time is 3 hours, then emptying the reactor, continuously introducing mixed gas of ethylene and 1-butene, wherein the weight ratio of the 1-butene to the ethylene is 0.12, performing copolymerization reaction of the ethylene and the 1-butene, the polymerization temperature is 84 ℃, the polymerization pressure is 2.1MPa, and the polymerization time is 1 hour to obtain polyethylene slurry;
and (3) separating the polyethylene slurry by adjusting a discharge valve, a flow meter adjusting valve and a reflux pump to obtain a dilute phase material flow II and a solid phase-rich material flow I, wherein the flow ratio of the solid phase-rich material flow I to the dilute phase material flow II is 1:1, then carrying out flash separation on the solid phase-rich material flow I, wherein the flash temperature is 35 ℃, and the flash pressure is 0.95MPa to obtain polyethylene, wherein the weight content of soluble low molecular weight polyethylene in the polyethylene is shown in Table 1.
Example 5
The method for preparing polyethylene by slurry polymerization comprises the following steps:
adding 100mg of BCE catalyst and 50L of propane into a continuous stirring tank type reactor, firstly introducing hydrogen into the reactor, controlling the pressure to be 2.3MPa, continuously introducing ethylene to carry out ethylene homopolymerization, wherein the polymerization temperature is 95 ℃, the polymerization pressure is 5.6MPa, and the polymerization time is 3h, then emptying the reactor, continuously introducing mixed gas of ethylene and 1-butene, wherein the weight ratio of the 1-butene to the ethylene is 0.12, carrying out copolymerization reaction of the ethylene and the 1-butene, the polymerization temperature is 95 ℃, the polymerization pressure is 5.4MPa, and the polymerization time is 1h, thus obtaining polyethylene slurry;
and (3) separating the polyethylene slurry by adjusting a discharge valve, a flow meter adjusting valve and a reflux pump to obtain a dilute phase material flow II and a solid phase-rich material flow I, wherein the flow ratio of the solid phase-rich material flow I to the dilute phase material flow II is 1:1, then carrying out flash separation on the solid phase-rich material flow I, wherein the flash temperature is 80 ℃, and the flash pressure is 0.3MPa to obtain polyethylene, wherein the weight content of soluble low molecular weight polyethylene in the polyethylene is shown in Table 1.
Comparative example 1
Comparative example 1 was carried out using a similar process flow to that of example 1, except that no solid phase concentration treatment was carried out, and only flash separation was carried out, specifically:
adding 100mg of BCE catalyst and 50L of n-pentane into a continuous stirring tank type reactor, firstly introducing hydrogen into the reactor, controlling the pressure to be 0.9MPa, continuously introducing ethylene to carry out ethylene homopolymerization, controlling the polymerization temperature to be 90 ℃, the polymerization pressure to be 1.2MPa and the polymerization time to be 3h, then emptying the reactor, continuously introducing mixed gas of ethylene and 1-butene, wherein the weight ratio of the 1-butene to the ethylene is 0.12, carrying out copolymerization reaction of the ethylene and the 1-butene, the polymerization temperature is 84 ℃, the polymerization pressure to be 0.5MPa and the polymerization time to be 1h, and obtaining polyethylene slurry;
and (3) carrying out flash separation on the polyethylene slurry at the flash temperature of 80 ℃ and the flash pressure of 0.2MPa to obtain the polyethylene, wherein the weight content of the soluble low molecular weight polyethylene in the polyethylene is shown in Table 1.
TABLE 1
| Content of soluble low molecular weight polyethylene in polyethylene (% by weight) | |
| Example 1 | 0.72 |
| Example 2 | 0.64 |
| Example 3 | 1.05 |
| Example 4 | 0.83 |
| Example 5 | 0.96 |
| Comparative example 1 | 2.19 |
From the results, the invention realizes the effective separation of the dilute phase material flow II and the material flow I rich in the solid phase by carrying out the solid phase concentration treatment on the polyethylene slurry, controls the content of the soluble low molecular weight polyethylene entering the material flow I rich in the solid phase by regulating and controlling the flow ratio of the dilute phase material flow II to the material flow I rich in the solid phase, can obviously reduce the content of the soluble low molecular weight polyethylene in the polyethylene, effectively improves the purity and the service performance of a polyethylene product, and simultaneously reduces the energy consumption of flash evaporation and the cost of solvent separation.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (11)
1. A method of treating a slurry polyethylene slurry, the method comprising: carrying out solid phase concentration treatment on polyethylene slurry obtained by slurry polymerization to obtain a dilute phase material flow II and a material flow I rich in a solid phase, removing a solvent and a monomer from the material flow I rich in the solid phase to obtain polyethylene, and separating the dilute phase material flow II to obtain the soluble low-molecular-weight polyethylene.
2. The process according to claim 1, wherein the flow ratio of the solid phase enriched stream I to the dilute phase stream II is (1: 9) - (9: 1).
3. The process according to claim 2, wherein the flow ratio of the solid phase enriched stream I to the dilute phase stream II is (1: 5) - (5: 1), preferably (1: 2) - (2: 1).
4. A process according to any one of claims 1 to 3, wherein the solid phase enriched stream I is subjected to flash separation to remove solvent and monomers to obtain polyethylene; and removing the soluble low molecular weight polyethylene from the dilute phase material flow II to obtain the soluble low molecular weight polyethylene, and recovering the solvent and the monomer.
5. The method of claim 4, wherein the flash separation conditions comprise: the flash evaporation temperature is 30-120 ℃, and preferably 35-100 ℃; the flash pressure is 0.05-2MPa, preferably 0.05-1 MPa.
6. A process for preparing polyethylene by slurry polymerization, the process comprising: carrying out polymerization reaction on an ethylene monomer and an optional comonomer in the presence of hydrogen, a catalyst and a solvent to obtain polyethylene slurry; and
treating the polyethylene slurry according to the method of any one of claims 1 to 5 to obtain polyethylene.
7. The method of claim 6, wherein the polymerization conditions comprise: the polymerization temperature is 50-140 ℃, preferably 60-110 ℃; the polymerization pressure is 0.5-6MPa, preferably 0.5-4.5 MPa; the reaction time is 0-5 h.
8. The process according to claim 6 or 7, wherein the optional comonomer comprises an alpha-olefin, preferably comprising C4-C10Of alpha-olefins.
9. Slurry polyethylene, characterized in that it is prepared according to the process of any one of claims 1 to 8.
10. An ethylene slurry polymerization device comprises a polymerization reactor and a solid phase concentration device which are communicated in sequence, and a micromolecule removing device and a separation device which are communicated with the solid phase concentration device, wherein,
the polymerization reactor is used for homopolymerization or copolymerization of ethylene by a slurry method;
the solid phase concentration equipment is used for carrying out solid phase concentration treatment on the polyethylene slurry obtained by the polymerization reactor to obtain a dilute phase material flow II and a material flow I rich in a solid phase;
the micromolecule removing equipment is used for removing the solvent and the monomer in the solid-phase-rich material flow I to obtain polyethylene;
the separation equipment is used for separating the dilute phase material flow II to obtain the soluble low molecular weight polyethylene.
11. The apparatus according to claim 10, wherein the small molecule removal device is preferably a flash device and the separation device is preferably a distillation dewaxing device.
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