CN115772241A - Method for controlling activity of metallocene catalyst - Google Patents
Method for controlling activity of metallocene catalyst Download PDFInfo
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- CN115772241A CN115772241A CN202211498954.0A CN202211498954A CN115772241A CN 115772241 A CN115772241 A CN 115772241A CN 202211498954 A CN202211498954 A CN 202211498954A CN 115772241 A CN115772241 A CN 115772241A
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- 239000012968 metallocene catalyst Substances 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 25
- 230000001276 controlling effect Effects 0.000 title description 9
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims abstract description 52
- 239000005977 Ethylene Substances 0.000 claims abstract description 52
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 35
- 230000000694 effects Effects 0.000 claims abstract description 34
- LIKMAJRDDDTEIG-UHFFFAOYSA-N 1-hexene Chemical compound CCCCC=C LIKMAJRDDDTEIG-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000002002 slurry Substances 0.000 claims abstract description 26
- 239000003054 catalyst Substances 0.000 claims abstract description 25
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000000741 silica gel Substances 0.000 claims abstract description 23
- 229910002027 silica gel Inorganic materials 0.000 claims abstract description 23
- 238000007334 copolymerization reaction Methods 0.000 claims abstract description 21
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000001301 oxygen Substances 0.000 claims abstract description 19
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 19
- 239000000843 powder Substances 0.000 claims abstract description 11
- 238000011068 loading method Methods 0.000 claims abstract description 5
- 239000007787 solid Substances 0.000 claims description 35
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 32
- 239000000725 suspension Substances 0.000 claims description 26
- 239000002904 solvent Substances 0.000 claims description 20
- 238000006243 chemical reaction Methods 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 14
- 238000001291 vacuum drying Methods 0.000 claims description 14
- 229920000642 polymer Polymers 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 12
- 238000005406 washing Methods 0.000 claims description 12
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 11
- 239000001257 hydrogen Substances 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 11
- 238000005303 weighing Methods 0.000 claims description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 10
- 239000004698 Polyethylene Substances 0.000 claims description 10
- -1 polyethylene Polymers 0.000 claims description 10
- 229920000573 polyethylene Polymers 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 9
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 9
- 239000000498 cooling water Substances 0.000 claims description 8
- 238000000967 suction filtration Methods 0.000 claims description 8
- 150000001875 compounds Chemical class 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- CPOFMOWDMVWCLF-UHFFFAOYSA-N methyl(oxo)alumane Chemical compound C[Al]=O CPOFMOWDMVWCLF-UHFFFAOYSA-N 0.000 claims description 6
- 238000000926 separation method Methods 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 5
- 229910001873 dinitrogen Inorganic materials 0.000 claims 2
- 239000000243 solution Substances 0.000 description 16
- 239000004712 Metallocene polyethylene (PE-MC) Substances 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 229920006351 engineering plastic Polymers 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229920006257 Heat-shrinkable film Polymers 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000012785 packaging film Substances 0.000 description 1
- 229920006280 packaging film Polymers 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920013716 polyethylene resin Polymers 0.000 description 1
- 239000002685 polymerization catalyst Substances 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000001175 rotational moulding Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Landscapes
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
Abstract
The invention discloses a method for controlling the activity of a metallocene catalyst, which comprises the following steps: the method is characterized in that the load silica gel with different grain diameters is used for loading in the load of the metallocene catalyst, the obtained metallocene catalyst with different activities is used for catalyzing the copolymerization of ethylene and hexene-1 slurry, and a small amount of oxygen is injected when the catalyst with the same activity is used for catalyzing the copolymerization of the ethylene and hexene-1 slurry, so that the polymerization reaction process is more stable, the phenomena of implosion or kettle sticking are avoided, the content of catalyst fine powder is reduced, and the like.
Description
Technical Field
The invention relates to a preparation method of catalyst activity, in particular to a method for controlling the activity of a metallocene catalyst, belonging to the field of petrochemical industry.
Background
Compared with the traditional titanium-based polyethylene and chromium-based polyethylene, the metallocene polyethylene has excellent performances of high mechanical strength, good optical performance, low odor, good temperature resistance and chemical corrosion resistance and the like; the metallocene polymer has been accepted by downstream users in the fields of film, pipe, rotational moulding oil tank and the like, and the performance of part of metallocene polymer has been extended to the performance field of traditional engineering plastics and even special engineering plastics, and has the trend and potential of gradually replacing common polyethylene materials.
In China, with the rapid development of new products such as heat shrinkable films, winding films, composite packaging films and the like, the demand of metallocene polyethylene is rapidly increased, the price of the metallocene polyethylene is 300-1000 yuan higher than that of common polyethylene per ton, and the metallocene polyethylene has considerable economic benefit; however, the domestic metallocene polyethylene yield is less than 20 million tons/year, the existing metallocene polyethylene production process is mainly a gas-phase fluidized bed process, and few enterprises capable of long-period stable production exist, so that the product gap is large, and most of the metallocene polyethylene needs to be imported. The main reason for the insufficient output of metallocene polyethylene in China is that the device can not run stably with long period and high load, and the core factor for restricting the stable running of the metallocene polyethylene device is the series bottleneck problems of low device load, large production control difficulty, frequent shutdown and the like caused by plastic blockage of a circulating gas pipeline and the like due to the phenomena of high activity ratio of a metallocene catalyst, a large amount of produced polyethylene fine powder, high static electricity in a reaction fluidized bed, easy flaking and the like. The research on the method for controlling the activity of the metallocene polyethylene catalyst is beneficial to the popularization of long-period high-load stable operation in the production of industrial metallocene polyethylene.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for controlling the activity of a metallocene catalyst, which has the technical characteristics of enabling the polymerization reaction process to be more stable, avoiding the occurrence of the phenomena of implosion or kettle sticking, reducing the content of fine powder of the catalyst and the like.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a method for controlling the activity of a metallocene catalyst, the method comprising: in the loading of the metallocene catalyst, loading silica gel with different grain diameters is used for loading, so that the metallocene catalyst with different activities is obtained for catalyzing the slurry copolymerization of ethylene and hexene-1, and a trace amount of oxygen is injected when the catalyst with the same activity is used for catalyzing the slurry copolymerization of ethylene and hexene-1.
Preferably, on a 2L-scale batch polymerization device, the system is respectively pressurized to 0.5MPa and 1.0MPa by nitrogen for air tightness, and after no leakage of the system is ensured, nitrogen is used for replacement, and then ethylene pressure replacement is used for 2 times; after replacement, introducing ethylene into a system, controlling the pressure of the system at a set pressure, heating the high-pressure polymerization kettle to a set temperature, slowly stirring and adding quantitative hexane, and then sequentially introducing hexene-1, hydrogen and oxygen into the high-pressure polymerization kettle; stirring and premixing for 3min, quickly adding the supported metallocene catalyst, then increasing the rotating speed to react for 2 hours, cooling, taking out the solid polyethylene powder and weighing.
Preferably, the preparation method of the supported metallocene catalyst comprises the following steps: adding a silica gel carrier into a solvent to form a suspension, then adding a methylaluminoxane solution, heating to 60 ℃, and stirring for reacting for 4 hours to obtain a carrier solid suspension loaded with a cocatalyst; carrying out solid-liquid separation treatment on the solid suspension, washing the separated solid for a plurality of times by using a solvent, and then carrying out vacuum drying to obtain a solid powdery carrier loaded with the cocatalyst; adding a cocatalyst-loaded carrier into a solvent to form a suspension, adding a metallocene compound solution, and reacting at the temperature of 20 ℃ for 1h; and filtering, washing and drying the reacted slurry to obtain the solid powdery supported metallocene catalyst.
Preferably, the supported metallocene catalyst obtained in the above is used for catalyzing the slurry copolymerization of ethylene and hexene-1 on a 2L-scale batch polymerization device, the pressure of a polymerization reaction kettle is controlled to be 1.0MPa, the temperature of the reaction kettle is controlled to be 80 ℃, the ethylene concentration is controlled to be 75 percent, the hydrogen concentration is controlled to be 100ppm, the hexene-1/ethylene concentration ratio is controlled to be 0.006, and the oxygen/ethylene concentration ratio is 2-10ppb; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure of the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate out a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, and weighing the obtained product. The catalyst activity is obtained by dividing by the amount of catalyst added during the polymerization.
Preferably, a silica gel carrier having an average silica gel particle size in the range of 30 to 65 μm is added to a solvent to form a suspension, and a supported metallocene catalyst sample is finally obtained as a solid powder.
Preferably, the obtained supported metallocene catalyst sample is used for catalyzing ethylene and hexene-1 slurry copolymerization reaction on a 2L-scale batch polymerization device, the pressure of a polymerization reaction kettle is controlled to be 1.0MPa, the temperature of the reaction kettle is controlled to be 80 ℃, the ethylene concentration is controlled to be 75%, the hydrogen concentration is controlled to be 100ppm, the hexene-1/ethylene concentration ratio is controlled to be 0.006, and 2ppb, 4ppb, 6ppb, 8ppb and 10ppb are respectively added into the oxygen/ethylene concentration ratio; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure in the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, and weighing the obtained product.
Has the beneficial effects that: the catalyst activity can be selectively reduced according to requirements by adjusting the particle size of the metallocene catalyst loaded silica gel and injecting a trace amount of oxygen in the slurry copolymerization reaction of ethylene and hexene-1, so that the polymerization reaction process is more stable, the phenomena of implosion or kettle sticking are avoided, and the content of fine powder of the catalyst is reduced.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples.
The purpose of the application is as follows: the olefin polymerization catalyst is the core of the development of polyolefin technology, and the carrier is a very critical factor in the innovation of the catalyst. The carrier not only plays a role of carrying and dispersing the active center, but also can possibly play a role as a special ligand and the active center, so that the activity and the selectivity of the catalyst are improved, the phenomena of interface charge transfer, molecular adsorption modulation and the like are often caused by the effect, the activation energy of the metallocene active center is changed, the uniform release of the activity of the catalyst is more facilitated, and the generation of fine powder in a polyethylene product is effectively reduced.
The invention provides a method for controlling the activity of a metallocene catalyst, aiming at selectively reducing the activity of the catalyst according to requirements by adjusting the particle size of metallocene catalyst loaded silica gel and injecting trace oxygen in slurry copolymerization of ethylene and hexene-1, thereby enabling the polymerization reaction process to be more stable, avoiding the occurrence of implosion or kettle sticking phenomenon and reducing the content of fine powder of the catalyst. From the evaluation result of 2L polymerization reaction of the catalyst, the activity of the metallocene catalyst in the copolymerization of ethylene and comonomer catalyzed by the metallocene catalyst, the oxygen/ethylene concentration ratio and other process indexes are regulated, so that large blocks of crystalline polyethylene resin lumps generated by static electricity in the polymerization reaction process can be effectively reduced, and polyethylene powder resin products with uniform distribution can be obtained.
In the load process of the metallocene catalyst, load silica gel with different grain diameters is used for load, the obtained metallocene catalyst with different activities is used for catalyzing slurry copolymerization of ethylene and hexene-1, and trace oxygen is injected when the catalyst with the same activity is used for catalyzing slurry copolymerization of ethylene and hexene-1.
Evaluation of catalyst polymerization: on a 2L-scale intermittent polymerization device, respectively pressurizing the system to 0.5MPa and 1.0MPa by using nitrogen for air tightness, and replacing the system by using nitrogen firstly and then using ethylene for pressure replacement for 2 times after ensuring that the system has no leakage; after replacement, controlling the pressure of the ethylene introduction system at a set pressure, heating the high-pressure polymerization kettle to a set temperature, slowly stirring and adding quantitative hexane, and then sequentially introducing hexene-1, hydrogen and oxygen into the high-pressure polymerization kettle; stirring and premixing for 3min, quickly adding the supported metallocene catalyst, then increasing the rotating speed to react for 2 hours, cooling, taking out the solid polyethylene powder and weighing.
The preparation method of the supported metallocene catalyst comprises the following steps:
adding a silica gel carrier into a solvent to form a suspension, then adding a methylaluminoxane solution, heating to 60 ℃, and stirring for reacting for 4 hours to obtain a carrier solid suspension loaded with a cocatalyst; carrying out solid-liquid separation treatment on the solid suspension, washing the separated solid for a plurality of times by using a solvent, and then carrying out vacuum drying to obtain a solid powdery carrier loaded with the cocatalyst; adding a cocatalyst-loaded carrier into a solvent to form a suspension, adding a metallocene compound solution, and reacting at the temperature of 20 ℃ for 1h; and filtering, washing and drying the reacted slurry to obtain the solid powdery supported metallocene catalyst.
The obtained supported metallocene catalyst is used for catalyzing ethylene and hexene-1 slurry copolymerization reaction on a 2L-scale batch polymerization device, wherein the pressure of a polymerization reaction kettle is controlled to be 1.0MPa, the temperature of the reaction kettle is controlled to be 80 ℃, the ethylene concentration is controlled to be 75%, the hydrogen concentration is controlled to be 100ppm, the hexene-1/ethylene concentration ratio is controlled to be 0.006, and the oxygen/ethylene concentration ratio is 2-10ppb; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure in the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, weighing the obtained product, and dividing the amount of the catalyst added during polymerization to obtain the catalyst activity.
Catalyst evaluation procedure and results:
(1) adding a silica gel carrier with the average silica gel particle size of 30-40 mu m into a solvent to form a suspension, then adding a methylaluminoxane solution, heating to 60 ℃, and stirring for reacting for 4 hours to obtain a carrier solid suspension loaded with a cocatalyst; carrying out solid-liquid separation treatment on the solid suspension, washing the separated solid for a plurality of times by using a solvent, and then carrying out vacuum drying to obtain a solid powdery carrier loaded with the cocatalyst; adding a cocatalyst-loaded carrier into a solvent to form a suspension, adding a metallocene compound solution, and reacting at the temperature of 20 ℃ for 1h; and filtering, washing and drying the reacted slurry to obtain a solid powdery supported metallocene catalyst sample 1.
(2) The supported metallocene catalyst sample 1 obtained in the step (1) is used for catalyzing the slurry copolymerization reaction of ethylene and hexene-1 on a 2L-scale batch polymerization device, the pressure of a polymerization reaction kettle is controlled to be 1.0MPa, the temperature of the reaction kettle is controlled to be 80 ℃, the ethylene concentration is controlled to be 75 percent, the hydrogen concentration is controlled to be 100ppm, the hexene-1/ethylene concentration ratio is controlled to be 0.006, and 2ppb, 4ppb, 6ppb, 8ppb and 10ppb are respectively added into the oxygen/ethylene concentration ratio; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure in the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate out a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, and weighing the obtained product.
(3) Adding a silica gel carrier with the average silica gel particle size of 45-55 mu m into a solvent to form a suspension, then adding a methylaluminoxane solution, heating to 60 ℃, and stirring for reacting for 4 hours to obtain a carrier solid suspension loaded with a cocatalyst; carrying out solid-liquid separation treatment on the solid suspension, washing the separated solid for a plurality of times by using a solvent, and then carrying out vacuum drying to obtain a solid powdery carrier loaded with the cocatalyst; adding a cocatalyst-loaded carrier into a solvent to form a suspension, adding a metallocene compound solution, and reacting at the temperature of 20 ℃ for 1h; and filtering, washing and drying the reacted slurry to obtain a solid powdery supported metallocene catalyst sample 2.
(4) The supported metallocene catalyst sample 2 obtained in (2) was subjected to slurry copolymerization of ethylene and hexene-1 in a 2L-scale batch polymerization apparatus, wherein the polymerization reactor pressure was controlled to 1.0MPa, the reactor temperature was controlled to 80 ℃, the ethylene concentration was controlled to 75%, the hydrogen concentration was controlled to 100ppm, the hexene-1/ethylene concentration ratio was controlled to 0.006, and the oxygen/ethylene concentration ratios were respectively added to 2ppb, 4ppb, 6ppb, 8ppb, and 10ppb; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure of the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate out a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, and weighing the obtained product.
(5) Adding a silica gel carrier with the average silica gel particle size of 55-65 mu m into a solvent to form a suspension, then adding a methylaluminoxane solution, heating to 60 ℃, and stirring for reacting for 4 hours to obtain a carrier solid suspension loaded with a cocatalyst; carrying out solid-liquid separation treatment on the solid suspension, washing the separated solid for a plurality of times by using a solvent, and then carrying out vacuum drying to obtain a solid powdery carrier loaded with the cocatalyst; adding a cocatalyst-loaded carrier into a solvent to form a suspension, adding a metallocene compound solution, and reacting at the temperature of 20 ℃ for 1h; and filtering, washing and drying the reacted slurry to obtain a solid powdery supported metallocene catalyst sample 3.
(6) The supported metallocene catalyst sample 3 obtained in (5) was subjected to slurry copolymerization of ethylene and hexene-1 in a 2L-scale batch polymerization apparatus, wherein the polymerization reactor pressure was controlled at 1.0MPa, the reactor temperature was controlled at 80 ℃, the ethylene concentration was controlled within 75%, the hydrogen concentration was controlled at 100ppm, and the hexene-1/ethylene concentration ratio was controlled at 0.006, and the oxygen/ethylene concentration ratios were respectively added at 2ppb, 4ppb, 6ppb, 8ppb, and 10ppb; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure of the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate out a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, and weighing the obtained product.
The results of the measurements of the supported metallocene catalyst for the slurry copolymerization of ethylene and hexene-1 are as follows:
the specific surface area of the adopted silica gel is 300-450m2/g, the pore volume is 1.05-1.30ml/g, and the particle size distribution range D10:
15-30μm；D50：40-55μm；D90：75-95μm。
(1) when the average particle size of the silica gel is 55-65 μm, the metallocene catalyst activity can be controlled within the following range: 1700-2850kgPE/kgCAT; average particle diameter of polymer: 0.702-0.729mm; sieve size ≦ 3ppm.
(2) When the average particle size of the silica gel is 45-55 μm, the controllable range of the activity of the metallocene catalyst is moderate:
3120-4582kgPE/kgCAT; average particle diameter of polymer: 0.728-0.755mm; screen size ≦ 1ppm.
(3) When the average particle size of the silica gel is 30-40 μm, the metallocene catalyst activity can be controlled within the following range:
5700-6800kgPE/kgCAT; average particle diameter of polymer: 0.776-0.801mm; screen size. Ltoreq.4.5 ppm.
(4) When the metallocene catalyst is used for catalyzing the slurry copolymerization of ethylene and hexene-1 after the injection of a trace amount of oxygen, the average activity of the catalyst can be reduced by 200-1200PE/kgCAT.
Finally, it should be noted that the present invention is not limited to the above embodiments, and many variations are possible. All modifications which can be derived or suggested by the person skilled in the art from the present disclosure are to be considered within the scope of the present invention.
Claims (6)
1. A method for controlling the activity of a metallocene catalyst, characterized in that the preparation method comprises: in the load of the metallocene catalyst, load silica gel with different grain diameters is used for loading, the obtained metallocene catalyst with different activities is used for catalyzing slurry copolymerization of ethylene and hexene-1, and trace oxygen is injected when the catalyst with the same activity is used for catalyzing slurry copolymerization of ethylene and hexene-1.
2. The method of claim 1, wherein the system is hermetically sealed by pressurizing to 0.5MPa and 1.0MPa with nitrogen gas in a 2L-scale batch polymerization apparatus, and after ensuring no leakage, the system is replaced with nitrogen gas and then with ethylene for 2 times; after replacement, introducing ethylene into a system, controlling the pressure of the system at a set pressure, heating the high-pressure polymerization kettle to a set temperature, slowly stirring and adding quantitative hexane, and then sequentially introducing hexene-1, hydrogen and oxygen into the high-pressure polymerization kettle; stirring and premixing for 3min, quickly adding the supported metallocene catalyst, then increasing the rotating speed to react for 2 h, cooling, taking out the solid polyethylene powder and weighing.
3. A method of controlling the activity of a metallocene catalyst according to claim 2, characterized in that: the preparation method of the supported metallocene catalyst comprises the following steps: adding a silica gel carrier into a solvent to form a suspension, then adding a methylaluminoxane solution, heating to 60 ℃, and stirring for reacting for 4 hours to obtain a carrier solid suspension loaded with a cocatalyst; carrying out solid-liquid separation treatment on the solid suspension, washing the separated solid for a plurality of times by using a solvent, and then carrying out vacuum drying to obtain a solid powdery carrier loaded with the cocatalyst; adding a cocatalyst-loaded carrier into a solvent to form a suspension, adding a metallocene compound solution, and reacting at the temperature of 20 ℃ for 1h; and filtering, washing and drying the reacted slurry to obtain the solid powdered supported metallocene catalyst.
4. A method of controlling the activity of a metallocene catalyst according to claim 3, characterized in that: the obtained supported metallocene catalyst is used for catalyzing ethylene and hexene-1 slurry copolymerization reaction on a 2L-scale batch polymerization device, wherein the pressure of a polymerization reaction kettle is controlled to be 1.0MPa, the temperature of the reaction kettle is controlled to be 80 ℃, the ethylene concentration is controlled to be 75 percent, the hydrogen concentration is controlled to be 100ppm, the hexene-1/ethylene concentration ratio is controlled to be 0.006, and the oxygen/ethylene concentration ratio is 2-10ppb; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure in the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate out a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, and weighing the obtained product. The catalyst activity was obtained by dividing by the amount of the catalyst added in the polymerization.
5. A method of controlling the activity of a metallocene catalyst according to claim 3, characterized in that: adding a silica gel carrier with the average silica gel particle size of 30-65 mu m into a solvent to form a suspension, and finally obtaining a solid powdery supported metallocene catalyst sample.
6. A method of controlling the activity of a metallocene catalyst according to claim 3 or 5, characterized in that: the obtained supported metallocene catalyst sample is used for catalyzing ethylene and hexene-1 slurry copolymerization reaction on a 2L-scale batch polymerization device, the pressure of a polymerization reaction kettle is controlled to be 1.0MPa, the temperature of the reaction kettle is controlled to be 80 ℃, the ethylene concentration is controlled to be 75 percent, the hydrogen concentration is controlled to be 100ppm, the hexene-1/ethylene concentration ratio is controlled to be 0.006, and 2ppb, 4ppb, 6ppb, 8ppb and 10ppb are respectively added into the oxygen/ethylene concentration ratio; after reacting for 2 hours, adding acidified ethanol with the mass fraction of 10 percent to terminate the reaction; cooling with cooling water and releasing the pressure of the high-pressure kettle to normal pressure; adding 500ml of acidified ethanol solution to precipitate out a polymer, carrying out suction filtration, drying, carrying out vacuum drying at 70 ℃ for 6 hours, and weighing the obtained product.
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