CN111087500B - Chromium-vanadium bimetallic catalyst and application thereof in catalytic synthesis of high-density polyethylene - Google Patents
Chromium-vanadium bimetallic catalyst and application thereof in catalytic synthesis of high-density polyethylene Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 98
- HBXWYZMULLEJSG-UHFFFAOYSA-N chromium vanadium Chemical compound [V][Cr][V][Cr] HBXWYZMULLEJSG-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 229920001903 high density polyethylene Polymers 0.000 title claims abstract description 26
- 239000004700 high-density polyethylene Substances 0.000 title claims abstract description 26
- 238000007036 catalytic synthesis reaction Methods 0.000 title abstract description 9
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 29
- 239000011347 resin Substances 0.000 claims abstract description 20
- 229920005989 resin Polymers 0.000 claims abstract description 20
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 20
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims abstract description 19
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 10
- 238000002360 preparation method Methods 0.000 claims abstract description 3
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 111
- 239000005977 Ethylene Substances 0.000 claims description 111
- 238000006243 chemical reaction Methods 0.000 claims description 98
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 72
- 239000001257 hydrogen Substances 0.000 claims description 72
- 229910052739 hydrogen Inorganic materials 0.000 claims description 72
- 125000000383 tetramethylene group Chemical group [H]C([H])([*:1])C([H])([H])C([H])([H])C([H])([H])[*:2] 0.000 claims description 52
- 239000011651 chromium Substances 0.000 claims description 24
- 239000000178 monomer Substances 0.000 claims description 22
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 claims description 21
- IAQRGUVFOMOMEM-UHFFFAOYSA-N butene Natural products CC=CC IAQRGUVFOMOMEM-UHFFFAOYSA-N 0.000 claims description 21
- 230000035484 reaction time Effects 0.000 claims description 21
- 229910052804 chromium Inorganic materials 0.000 claims description 20
- 238000006722 reduction reaction Methods 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 17
- 230000009467 reduction Effects 0.000 claims description 15
- 239000012298 atmosphere Substances 0.000 claims description 13
- 239000012018 catalyst precursor Substances 0.000 claims description 13
- 239000000741 silica gel Substances 0.000 claims description 11
- 229910002027 silica gel Inorganic materials 0.000 claims description 11
- 239000011261 inert gas Substances 0.000 claims description 10
- 238000011068 loading method Methods 0.000 claims description 10
- GCPCLEKQVMKXJM-UHFFFAOYSA-N ethoxy(diethyl)alumane Chemical compound CCO[Al](CC)CC GCPCLEKQVMKXJM-UHFFFAOYSA-N 0.000 claims description 8
- 150000003839 salts Chemical class 0.000 claims description 8
- 239000003638 chemical reducing agent Substances 0.000 claims description 7
- WYYQVWLEPYFFLP-UHFFFAOYSA-K chromium(3+);triacetate Chemical compound [Cr+3].CC([O-])=O.CC([O-])=O.CC([O-])=O WYYQVWLEPYFFLP-UHFFFAOYSA-K 0.000 claims description 7
- VOITXYVAKOUIBA-UHFFFAOYSA-N triethylaluminium Chemical compound CC[Al](CC)CC VOITXYVAKOUIBA-UHFFFAOYSA-N 0.000 claims description 7
- 238000010304 firing Methods 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 238000001179 sorption measurement Methods 0.000 claims description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 4
- UNTBPXHCXVWYOI-UHFFFAOYSA-O azanium;oxido(dioxo)vanadium Chemical compound [NH4+].[O-][V](=O)=O UNTBPXHCXVWYOI-UHFFFAOYSA-O 0.000 claims description 4
- 125000002524 organometallic group Chemical group 0.000 claims description 4
- 239000012266 salt solution Substances 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- WGLPBDUCMAPZCE-UHFFFAOYSA-N chromium trioxide Inorganic materials O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 230000000379 polymerizing effect Effects 0.000 claims description 3
- PMJNEQWWZRSFCE-UHFFFAOYSA-N 3-ethoxy-3-oxo-2-(thiophen-2-ylmethyl)propanoic acid Chemical compound CCOC(=O)C(C(O)=O)CC1=CC=CS1 PMJNEQWWZRSFCE-UHFFFAOYSA-N 0.000 claims description 2
- 229940117975 chromium trioxide Drugs 0.000 claims description 2
- GAMDZJFZMJECOS-UHFFFAOYSA-N chromium(6+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Cr+6] GAMDZJFZMJECOS-UHFFFAOYSA-N 0.000 claims description 2
- 229910052809 inorganic oxide Inorganic materials 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- 238000006116 polymerization reaction Methods 0.000 abstract description 75
- 229920013716 polyethylene resin Polymers 0.000 abstract description 35
- 230000000694 effects Effects 0.000 abstract description 19
- 230000015572 biosynthetic process Effects 0.000 abstract description 7
- 238000003786 synthesis reaction Methods 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000003197 catalytic effect Effects 0.000 abstract description 3
- 125000005234 alkyl aluminium group Chemical group 0.000 abstract description 2
- 239000002861 polymer material Substances 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 90
- 229910052757 nitrogen Inorganic materials 0.000 description 45
- 238000012685 gas phase polymerization Methods 0.000 description 36
- 230000000052 comparative effect Effects 0.000 description 19
- 238000010438 heat treatment Methods 0.000 description 17
- 238000005303 weighing Methods 0.000 description 15
- 230000008569 process Effects 0.000 description 13
- 239000000243 solution Substances 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 238000006555 catalytic reaction Methods 0.000 description 10
- 239000004698 Polyethylene Substances 0.000 description 8
- 229920000573 polyethylene Polymers 0.000 description 8
- -1 polyethylenes Polymers 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 238000001816 cooling Methods 0.000 description 6
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 6
- 239000012299 nitrogen atmosphere Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 230000004913 activation Effects 0.000 description 4
- 238000001354 calcination Methods 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 230000037048 polymerization activity Effects 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- PBKONEOXTCPAFI-UHFFFAOYSA-N 1,2,4-trichlorobenzene Chemical compound ClC1=CC=C(Cl)C(Cl)=C1 PBKONEOXTCPAFI-UHFFFAOYSA-N 0.000 description 3
- 238000007598 dipping method Methods 0.000 description 3
- 239000012153 distilled water Substances 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 238000005227 gel permeation chromatography Methods 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 238000011946 reduction process Methods 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000000499 gel Substances 0.000 description 2
- 239000001307 helium Substances 0.000 description 2
- 229910052734 helium Inorganic materials 0.000 description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
- 229920001684 low density polyethylene Polymers 0.000 description 2
- 239000004702 low-density polyethylene Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000012968 metallocene catalyst Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000013519 translation Methods 0.000 description 2
- 229920010126 Linear Low Density Polyethylene (LLDPE) Polymers 0.000 description 1
- 241000203354 Melanophylla Species 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000001844 chromium Chemical class 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000008570 general process Effects 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- 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
- C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F10/02—Ethene
-
- 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
- C08F2410/00—Features related to the catalyst preparation, the catalyst use or to the deactivation of the catalyst
- C08F2410/03—Multinuclear procatalyst, i.e. containing two or more metals, being different or not
-
- 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
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
- Polymerization Catalysts (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention belongs to the technical field of high polymer material synthesis, and particularly relates to a chromium-vanadium bimetallic active center catalyst, and further discloses a preparation method thereof, and application of the catalyst in catalytic synthesis of high-density polyethylene resin. The chromium-vanadium bimetallic active center catalyst is prepared by reducing chromium element and vanadium element by adopting two kinds of distributed alkyl aluminum, has high catalytic activity, is used for catalytic synthesis of polyethylene resin products, and is beneficial to catalytic synthesis of resin products with various density grades. The polymerization process of the method for synthesizing the high-density polyethylene resin carries out polymerization reaction in a mode of adding the comonomer and the molecular weight regulator in stages in the polymerization process, so that the activity of the whole polymerization process is higher, and the effect of adjusting the density of a polyethylene resin product without frequently replacing a catalyst is achieved, so that the synthesis of the polyethylene resin with different density and performance requirements can be completed at one time.
Description
Technical Field
The invention belongs to the technical field of high polymer material synthesis, and particularly relates to a chromium-vanadium bimetallic active center catalyst, and further discloses a preparation method thereof, and application of the catalyst in catalytic synthesis of high-density polyethylene resin.
Background
Polyethylene (PE) resin is a thermoplastic obtained by polymerizing ethylene monomer, and is the most popular plastic product in the world today with the highest output and consumption. Polyethylene resins mainly include Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), high Density Polyethylene (HDPE), and some polyethylenes having special properties.
Among all the polyethylene resin products, HDPE has the highest modulus and the lowest permeability, and is beneficial to being made into containers for medium-sized or large-sized shipping liquid such as barrels, tanks and the like, and the volume of the containers can reach 200 liters or even larger; it can be made into large container for holding chemicals, and also can be made into small container. And because the high-density polyethylene has the advantages of good toughness, low price, easy molding and processing, good chemical corrosion resistance and the like, the application range of the high-density polyethylene in various fields is continuously expanded, and the high-density polyethylene becomes one of general plastics with the largest consumption.
In the synthesis process of polyethylene, the catalyst plays an important role. The catalysts for preparing high density polyethylene are mainly known as Ziegler-Natta catalysts, chromium-based catalysts, metallocene catalysts and other non-metallocene catalysts. For example, both j.p Hogan and r.l.bank reported in patent US2825721 a silica gel supported chromium oxide catalyst, which was an inorganic chromium catalyst that was well known later. Leonard m. Baker and Wayne l. Carrick disclose an organochromium polyethylene catalyst, i.e., an S-2 organochromium catalyst from Union Carbide, in US3324101, US3324095 and CA759121, respectively. The structures of these two catalysts are very similar, but there is a large difference in the reaction for catalyzing the polymerization of polyethylene resins. Because the polymerization activity of the inorganic chromium catalyst is very high, the produced polyethylene product generally has wider molecular weight distribution, and the insertion amount of the polymer monomer is higher, so that the catalyst efficiency is higher; the polymerization activity of the S-2 organic chromium catalyst is low, and the hydrogen response and copolymerization performance are general.
In the polyethylene synthesis process, the catalyst can generate different influences on the characteristics of the density and the like of a polymerization product, so that in the industry, high-density polyethylene resins with different densities are produced, catalyst products with different grades need to be switched, and the process is complicated and a large amount of material consumption is caused.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to provide a chromium-vanadium bimetallic catalyst to solve the problem of material waste caused by frequent catalyst replacement in the prior art for synthesizing polyethylene products with different densities;
the second technical problem to be solved by the present invention is to provide a method for catalytically synthesizing high density polyethylene resin, so as to obtain polyethylene resin products with wider density range.
In order to solve the technical problem, the method for preparing the chromium-vanadium bimetallic catalyst comprises the following steps:
(1) Respectively loading a chromium element and a vanadium element on an inorganic carrier to prepare a first catalyst precursor loaded with a chromium-vanadium bimetallic element;
(2) Roasting the first catalyst precursor to prepare a second catalyst precursor containing an oxidation state chromium vanadium bimetallic element;
(3) And carrying out reduction reaction on the second catalyst precursor to prepare the chromium-vanadium bimetallic catalyst containing the low-oxidation-state chromium-vanadium compound, and drying to obtain the catalyst.
In the step (1), the supporting step includes a step of preparing salt solutions containing chromium and vanadium, respectively, and immersing the inorganic carrier in the salt solutions to perform physical adsorption, and a step of drying the first catalyst precursor after the supporting treatment.
The salt containing chromium element is known chromium-containing salt, including chromium trioxide, chromium acetate, ammonium chromate and/or basic chromium acetate, or other suitable soluble chromium salt and combination thereof; according to one embodiment of the invention, the loading of chromium is generally in the range of from 0.05 to 1wt%, based on the weight of Cr, based on the total weight of the catalyst.
The vanadium-containing salt comprises known vanadium-containing salts, which are usually dissolved in water or other organic solvents, and preferably ammonium metavanadate and ammonium hexafluorovanadate; the vanadium loading is generally from 20 to 300% of the chromium loading (both based on the weight of Cr and V), and generally from 0.05 to 1wt% of the total weight of the catalyst, based on the weight of V.
The inorganic support is selected from the group consisting of particulate, porous inorganic oxide silica gels, as may be mentioned Davison955; the specific surface area of the inorganic carrier is 50-500m 2 Per g, preferably from 100 to 300m 2 Per g, the pore volume of the inorganic carrier is 0.1-5.0cm 3 In g, preferably 0.5 to 3.0cm 3 /g。
The step (1) is to dip the chromium precursor, i.e. the salt containing chromium element, onto the inorganic carrier, wherein the dipping mode is a conventional mode in the prior art, according to one scheme of the invention, one or more chromium-containing salts are prepared into a solution and dipped in the solution within a certain time, the dipping process can be any general process, and the solution can be stirred, preferably continuously stirred, for 1-12h, preferably 4-8h, and the dipping temperature is 5-80 ℃, preferably 10-50 ℃.
The drying step is to dry the catalyst precursor impregnated with the two metal elements, and the drying is usually carried out at a temperature of from room temperature to 200 ℃, preferably from 100 ℃ to 200 ℃. According to one embodiment of the invention, the drying is carried out at about 120 ℃; the drying is carried out for a period of time not particularly limited, and usually for 6 to 20 hours, preferably 8 to 15 hours.
In the step (2), the high-temperature roasting step comprises the steps of low-temperature roasting at 100-300 ℃ and high-temperature roasting at 300-900 ℃ respectively;
the low-temperature roasting step is carried out in the atmosphere of air or inert gas;
the high-temperature roasting step is carried out in the air or oxygen atmosphere.
After the catalyst precursor impregnated with the two metal elements was dried, the obtained sample was calcined. The manner in which the calcination is carried out is not particularly limited, but the calcination is preferably carried out in a fluidized bed. It is generally carried out in two stages, namely a low-temperature stage and a high-temperature stage. The low temperature stage is usually carried out at 100-300 ℃ and the high temperature stage is usually carried out at 300-900 ℃. Physical water adsorbed in the low temperature stage carrier is removed, and a part of hydroxyl groups on the inorganic carrier is removed in the high temperature stage. The low-temperature phase lasts for 1 to 10 hours, preferably 2 to 8 hours. The elevated temperature phase lasts for 1 to 10 hours, preferably 3 to 8 hours. The low temperature stage is carried out under an inert gas or air atmosphere, preferably under an inert gas such as nitrogen, helium, argon, etc., preferably under a nitrogen atmosphere, e.g., high purity nitrogen. The high temperature stage firing is carried out under air or oxygen conditions, preferably under dry air conditions. After the baking, the catalyst obtained is cooled from the high temperature stage. Upon cooling to a temperature of 300-400 ℃ after high temperature firing, the atmosphere may be changed, for example, from air to an inert gas such as high purity nitrogen or the like. According to one embodiment of the invention, the cooling is free cooling. And storing the obtained catalyst under an inert gas atmosphere for later use.
In the step (3), the reduction reaction comprises the step of reducing the chromium element and the vanadium element in sequence in an inert atmosphere in the presence of a suitable organic metal reducing agent;
the elemental chromium-reduced organometallic reducing agent comprises diethylaluminum ethoxide;
the organometallic reducing agent for the reduction of the vanadium element comprises triethylaluminum.
And (3) adding ethoxydiethylaluminum in an inert atmosphere to carry out pre-reduction activation treatment on the catalyst, wherein when carrying out pre-reduction treatment on the chromium-vanadium double-activity center catalyst, the aluminum/chromium molar ratio is controlled to be between 0 and 25, preferably between 0 and 20, the reduction activation treatment temperature is between room temperature and 100 ℃, preferably between room temperature and 70 ℃, and the reduction time is 10 to 25min, and the reduction activation treatment adopts a stirring mode, preferably continuous stirring. And in the pre-reduction process of the second stage of the catalyst precursor, the adopted organic metal reducing agent is triethyl aluminum, and the reduction process is similar to that of the first stage.
And a step of drying the catalyst after the distributed reduction, wherein the drying process is preferably performed at 60-120 ℃ for 10-15 hours, and the drying process is performed under an inert gas atmosphere, for example, under an atmosphere of nitrogen, helium, argon, and the like, preferably under a nitrogen atmosphere, and the drying process can also be performed under a vacuum condition, and a stirring manner can be adopted, preferably continuous stirring. The obtained chromium-vanadium double-active center catalyst after pre-reduction activation is stored under the inert gas atmosphere for later use.
The invention also discloses the chromium-vanadium bimetallic active center catalyst prepared by the method.
The invention also discloses application of the chromium-vanadium bimetallic active center catalyst in catalytic synthesis of high-density polyethylene resin.
The invention also discloses a method for synthesizing high-density polyethylene resin, which comprises the step of polymerizing ethylene monomer in the presence of the chromium-vanadium bimetallic active center catalyst under the protection of inert gas and introducing butylene and hydrogen.
The step of feeding butene and hydrogen comprises a first reaction stage and a second reaction stage which are independent of each other and feed butene and hydrogen in a ratio of butene/ethylene molar ratio of 0.003-0.06 and hydrogen/ethylene molar ratio of 0.01-0.06;
the reaction time ratio of the first reaction stage to the second reaction stage is 1:3-3:1.
specifically, the synthetic process of the polyethylene resin comprises the following steps: firstly, a polymerization kettle is treated under the high-temperature and vacuum state, high-purity nitrogen is used for replacing at least three times and then is supplemented for standby, a dry powder catalyst is added into the polymerization kettle under the protection of the high-purity nitrogen after being measured, the polymerization kettle is stirred after being vacuumized, hot water is introduced into a jacket to raise the temperature of the polymerization kettle to 80-102 ℃, ethylene gas is slowly added until the reaction pressure is 0.8-2.0 MPa, and the polymerization reaction is started. The total reaction time was set to 1 hour, the reaction started in the first stage (which may be 15 minutes, 30 minutes and 45 minutes), and butene and hydrogen were fed to the reactor in a butene/ethylene molar ratio of 0.003 to 0.06 and a hydrogen/ethylene molar ratio of 0.01 to 0.06. In the second stage of the reaction (which may be 15 minutes, 30 minutes and 45 minutes), butene and hydrogen are fed to the reactor in a butene/ethylene molar ratio of 0.003 to 0.06 and in a hydrogen/ethylene molar ratio of 0.01 to 0.06. The polymerization pressure is kept constant by a mass flow meter and a pressure sensor through a control system, and the polymerization temperature is controlled by a combined water bath through a control system adjusting an online heater and a circulating water pump.
The invention also discloses the high-density polyethylene resin synthesized by the method.
The chromium-vanadium bimetallic active center catalyst is prepared by reducing chromium element and vanadium element by adopting two kinds of distributed alkyl aluminum, has high catalytic activity, is used for catalytic synthesis of polyethylene resin products, and is beneficial to catalytic synthesis of resin products with various density grades.
The polymerization process of the method for synthesizing the high-density polyethylene resin carries out polymerization reaction in a mode of adding the comonomer and the molecular weight regulator in stages in the polymerization process, so that the activity of the whole polymerization process is higher, and the effect of adjusting the density of a polyethylene resin product without frequently replacing a catalyst is achieved, so that the synthesis of the polyethylene resin with different density and performance requirements can be completed at one time.
Detailed Description
Example 1
Selecting commercially available Davison955 silica gel as the inorganic carrier; dissolving 1.043g of chromium acetate in 200ml of distilled water at normal temperature (chromium loading is 0.30 wt%), weighing 0.2790g of ammonium metavanadate (vanadium loading is 0.30 wt%) and adding the ammonium metavanadate into the solution, continuously stirring at the stirring speed of 240 revolutions per minute, and heating the solution to 60 ℃; then 40g of silica gel is soaked in the solution, and the solution is soaked for 3 hours at the temperature of 60 ℃ to ensure that the active components are uniformly adsorbed in the silica gel micropores; the whole process belongs to a physical adsorption process. Then drying at 120 ℃ for 20h, transferring to a fluidized bed for roasting, raising the temperature to 200 ℃ in a high-purity nitrogen atmosphere, keeping the temperature for 1h to remove physical water, introducing dry air, keeping the temperature at 600 ℃ for 4h, and naturally cooling under nitrogen for later use.
Weighing the catalyst, adding 800ml of n-hexane as a solvent, adding diethyl aluminum ethoxide for reduction, and controlling the molar ratio of Al to Cr to be 6:1, reducing for 20min; then adding triethyl aluminum for reduction, and controlling the molar ratio of Al to V to be 6:1, reducing for 20min; and heating to 70 ℃ and drying for 12h to obtain the catalyst dry powder with better fluidity.
In the embodiment, the prepared chromium-vanadium double-activity center catalysis is adopted for ethylene gas phase polymerization, firstly, a gas phase polymerization kettle is heated, vacuumized and treated by high-purity nitrogen for 4 hours, 0.6g of the prepared catalyst is weighed and added into the polymerization kettle under the protection of the high-purity nitrogen, the kettle temperature is raised to 92 ℃, ethylene monomer is slowly added until the reaction pressure is 1.2MPa, the polymerization reaction is started, and the pressure and the temperature in the polymerization kettle are kept constant; controlling the reaction time to be 1h, wherein the reaction time of the first stage of the reaction is 30min, and adding butylene (according to the molar ratio of butylene to ethylene of 0.003) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; the time of the second stage of the reaction is 30min, namely after the reaction of the first stage is finished for 30min, adding butylene (according to the molar ratio of butylene/ethylene of 0.003) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) to continue the reaction for 30min to obtain the required polyethylene resin.
Example 2
Adopting the chromium-vanadium double-activity center catalyst prepared in the example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the temperature of the kettle to 92 ℃, slowly adding an ethylene monomer to the reaction pressure of 1.2MPa, starting the polymerization reaction, and keeping the pressure and the temperature in the polymerization kettle constant. Setting the reaction time as 1h, wherein the first stage time of the reaction is 30min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.008) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; the time of the second stage of reaction is 30min, namely, after the first stage of reaction is finished, adding butylene (according to the molar ratio of butylene/ethylene of 0.008) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) to continue the reaction for 30min to obtain the polyethylene resin.
Example 3
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. Controlling the reaction time to be 1h, wherein the first stage of the reaction is 30min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.02) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; the second reaction stage is 30min, namely after the first reaction stage is finished, adding butylene (according to the molar ratio of butylene to ethylene of 0.02) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) to continue reacting for 30min to obtain the polyethylene resin.
Example 4
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the temperature of the kettle to 92 ℃, slowly adding an ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant; the reaction time is set as 1h, wherein the first stage of the reaction is 30min, namely, butene (according to the butene/ethylene molar ratio of 0.04) and hydrogen (according to the hydrogen/ethylene molar ratio of 0.02) are added at the beginning of the reaction; the second reaction stage is 30min, namely after the first reaction stage is finished, adding butylene (according to the molar ratio of butylene to ethylene of 0.04) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) to continue reacting for 30in to obtain the polyethylene resin.
Example 5
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.003) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; the second stage of the reaction is 45min, namely after the reaction in the first stage is finished, adding butylene (according to the molar ratio of butylene/ethylene of 0.06) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) to continue the reaction for 45min to obtain the polyethylene resin.
Example 6
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, namely adding butylene (according to the molar ratio of butylene/ethylene of 0.004) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) at the beginning of the reaction; setting the second stage of the reaction to be 45min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.05) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) to continue the reaction for 45min after the reaction of the first stage is finished, and obtaining the polyethylene resin.
Example 7
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, namely adding butylene (according to the molar ratio of butylene/ethylene of 0.006) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) at the beginning of the reaction; setting the second stage of the reaction to be 45min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.04) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) after the reaction of the first stage, and continuing translation for 45min to obtain the polyethylene resin.
Example 8
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.008) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; setting the second stage of the reaction to be 45min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.03) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) after the reaction of the first stage, and continuing translation for 45min to obtain the polyethylene resin.
Example 9
Selecting commercially available Davison955 silica gel as the inorganic carrier; dissolving 1.043g of chromium acetate in 200ml of distilled water at normal temperature (chromium loading is 0.15 wt%), weighing 0.6013g of ammonium hexafluorovanadate (vanadium loading is 0.35 wt%) and adding the ammonium hexafluorovanadate into the solution, continuously stirring at a stirring speed of 240 revolutions per minute, and heating the solution to 60 ℃; then 40g of silica gel is soaked in the solution, and the solution is soaked for 3 hours at the temperature of 60 ℃ to ensure that the active components are uniformly adsorbed in the silica gel micropores; the whole process belongs to a physical adsorption process. Drying at 120 deg.C for 20 hr, transferring to fluidized bed, calcining, heating to 200 deg.C in high-purity nitrogen atmosphere, maintaining for 1 hr to remove physical water, introducing dry air, maintaining at 600 deg.C for 4 hr, and naturally cooling under nitrogen.
Weighing the catalyst, adding 800ml of n-hexane as a solvent, adding diethyl aluminum ethoxide for reduction, and controlling the molar ratio of Al to Cr to be 6:1, reducing for 20min. Then adding triethyl aluminum for reduction, and controlling the molar ratio of Al/V to be 6:1, reducing for 20min. And heating to 70 ℃ and drying for 12h to obtain the catalyst dry powder with better fluidity.
The gas phase polymerisation of ethylene was carried out using the chromium vanadium dual active site catalyst of example 9, the polymerisation procedure being the same as in example 1.
Examples 10 to 16
The synthesis method of the polyethylene resin in the following examples 10-16 of the present invention is to perform the catalytic polymerization of the polyethylene resin by using the bimetallic active site catalyst prepared in the scheme of example 9, and the synthesis processes are the same as the polymerization processes in examples 2-8, respectively, to obtain the polyethylene resin product. Specific resin properties are referenced in table 2.
Comparative example 1
A single chromium catalyst was prepared by selecting commercially available Davison955 silica gel as the inorganic support; 1.043g of chromium acetate is dissolved in 200ml of distilled water at normal temperature (the chromium loading is 0.30 wt%); then, 40g of silica gel is soaked in the solution for 3 hours to ensure that the active components are uniformly adsorbed in the silica gel micropores; the whole process belongs to a physical adsorption process. Drying at 120 deg.C for 20 hr, transferring to fluidized bed, calcining, heating to 200 deg.C in high-purity nitrogen atmosphere, maintaining for 1 hr to remove physical water, introducing dry air, maintaining at 600 deg.C for 4 hr, and naturally cooling under nitrogen. Weighing the catalyst, adding 800ml of n-hexane as a solvent, adding diethyl aluminum ethoxide for reduction, and controlling the molar ratio of Al to Cr to be 6:1, reducing for 30min. And heating to 70 ℃ and drying for 4 hours to obtain the catalyst dry powder with better fluidity.
The catalyst is adopted to carry out ethylene gas phase polymerization, firstly, a gas phase polymerization kettle is heated, vacuumized and treated by high-purity nitrogen for 4 hours, 0.6g of the prepared catalyst is weighed and added into the polymerization kettle under the protection of the high-purity nitrogen, the temperature of the kettle is raised to 92 ℃, ethylene monomers are slowly added until the reaction pressure is 1.2MPa, the polymerization reaction is started, and the pressure and the temperature in the polymerization kettle are kept constant. Setting the reaction time as 1h, and adding butylene (according to the molar ratio of butylene/ethylene of 0.003) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) at the beginning of the reaction for reaction to obtain the polyethylene resin.
Comparative example 2
The catalyst in the comparative example 1 is adopted to carry out ethylene gas phase polymerization, firstly, a gas phase polymerization kettle is heated, vacuumized and treated by high-purity nitrogen for 4 hours, 0.6g of the prepared catalyst is weighed and added into the polymerization kettle under the protection of the high-purity nitrogen, the kettle is heated to 92 ℃, ethylene monomer is slowly added until the reaction pressure is 1.2MPa, the polymerization reaction is started, and the pressure and the temperature in the polymerization kettle are kept constant. The reaction time was set to 1 hour, and butene (in terms of butene/ethylene molar ratio of 0.008) and hydrogen (in terms of hydrogen/ethylene molar ratio of 0.02) were added at the beginning of the reaction to carry out a reaction, thereby obtaining a polyethylene resin.
Comparative example 3
The catalyst in the comparative example 1 is adopted to carry out ethylene gas phase polymerization, firstly, a gas phase polymerization kettle is heated, vacuumized and treated by high-purity nitrogen for 4 hours, 0.6g of the prepared catalyst is weighed and added into the polymerization kettle under the protection of the high-purity nitrogen, the kettle is heated to 92 ℃, ethylene monomer is slowly added until the reaction pressure is 1.2MPa, the polymerization reaction is started, and the pressure and the temperature in the polymerization kettle are kept constant. The reaction time was set to 1, and butene (in terms of butene/ethylene molar ratio of 0.02) and hydrogen (in terms of hydrogen/ethylene molar ratio of 0.02) were added at the beginning of the reaction to carry out a reaction, thereby obtaining a polyethylene resin.
Comparative example 4
The catalyst in the comparative example 1 is adopted to carry out ethylene gas phase polymerization, firstly, a gas phase polymerization kettle is heated, vacuumized and treated by high-purity nitrogen for 4 hours, 0.6g of the prepared catalyst is weighed and added into the polymerization kettle under the protection of the high-purity nitrogen, the kettle is heated to 92 ℃, ethylene monomer is slowly added until the reaction pressure is 1.2MPa, the polymerization reaction is started, and the pressure and the temperature in the polymerization kettle are kept constant. The reaction time was set to 1 hour, and butene (in terms of butene/ethylene molar ratio of 0.03) and hydrogen (in terms of hydrogen/ethylene molar ratio of 0.02) were added at the beginning of the reaction to carry out a reaction, thereby obtaining a polyethylene resin.
Comparative example 5
The catalyst in comparative example 1 was used for the gas phase polymerization of ethylene, first the gas phase polymerization kettle was heated, evacuated and treated with high purity nitrogen for 4h, 0.6g of the catalyst prepared above was weighed and added to the polymerization kettle under the protection of high purity nitrogen, the kettle temperature was raised to 92 ℃, ethylene monomer was slowly added to the reaction pressure of 1.2MPa, the polymerization was started, and the pressure and temperature in the polymerization kettle were kept constant. Setting the reaction time as 1h, and adding butylene (according to the molar ratio of butylene/ethylene of 0.04) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) at the beginning of the reaction for reaction to obtain the polyethylene resin.
Comparative example 6
The catalyst in comparative example 1 was used for the gas phase polymerization of ethylene, first the gas phase polymerization kettle was heated, evacuated and treated with high purity nitrogen for 4h, 0.6g of the catalyst prepared above was weighed and added to the polymerization kettle under the protection of high purity nitrogen, the kettle temperature was raised to 92 ℃, ethylene monomer was slowly added to the reaction pressure of 1.2MPa, the polymerization was started, and the pressure and temperature in the polymerization kettle were kept constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, and adding butylene (according to the molar ratio of butylene to ethylene of 0.003) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; setting the second stage of the reaction to be 45min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.04) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) to continue the reaction for 45min after the reaction of the first stage is finished, and obtaining the polyethylene resin.
Comparative example 7
The catalyst in the comparative example 1 is adopted to carry out ethylene gas phase polymerization, firstly, a gas phase polymerization kettle is heated, vacuumized and treated by high-purity nitrogen for 4 hours, 0.6g of the prepared catalyst is weighed and added into the polymerization kettle under the protection of the high-purity nitrogen, the kettle is heated to 92 ℃, ethylene monomer is slowly added until the reaction pressure is 1.2MPa, the polymerization reaction is started, and the pressure and the temperature in the polymerization kettle are kept constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, and adding butylene (according to the molar ratio of butylene/ethylene of 0.008) and hydrogen (according to the molar ratio of hydrogen/ethylene of 0.02) at the beginning of the reaction; setting the second stage of the reaction to be 45min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.03) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) after the reaction of the first stage is finished, and continuing to react for 45min to obtain the polyethylene resin.
Comparative example 8
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, and adding butylene (according to the molar ratio of butylene to ethylene of 0.008) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; setting the second stage of the reaction to be 45min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.07) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) to continue the reaction for 45min after the reaction of the first stage is finished, and obtaining the polyethylene resin.
Comparative example 9
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. Setting the reaction time as 1h, wherein the first stage of the reaction is 15min, and adding butylene (according to the molar ratio of butylene to ethylene of 0.002) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) at the beginning of the reaction; setting the second stage of the reaction to be 45min, namely adding butylene (according to the molar ratio of butylene to ethylene of 0.01) and hydrogen (according to the molar ratio of hydrogen to ethylene of 0.02) to continue the reaction for 45min after the reaction of the first stage is finished, and obtaining the polyethylene resin.
Comparative example 10
The catalyst of this example was prepared in the same manner as in example 1, except that during the reduction of the catalyst, the vanadium element was reduced by triethyl aluminum and then the chromium element was reduced by diethyl aluminum ethoxide. The obtained catalyst has low activity in the polymerization process, and the density range of the produced resin product is narrow, so that the diethyl aluminum ethoxide is added firstly, and then the triethyl aluminum is added in the catalyst reduction process.
Comparative example 11
Adopting chromium-vanadium double-activity center catalysis in example 1 to carry out ethylene gas phase polymerization, firstly heating a gas phase polymerization kettle, vacuumizing and treating with high-purity nitrogen for 4 hours, weighing 0.6g of the prepared catalyst, adding the weighed catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the kettle temperature to 92 ℃, slowly adding ethylene monomer to the reaction pressure of 1.2MPa, starting polymerization, and keeping the pressure and the temperature in the polymerization kettle constant. The butene/ethylene molar ratio is controlled to fluctuate between 0.003 and 0.06, the fluctuation period is 5 minutes, and the hydrogen/ethylene molar ratio is controlled to be 0.02. The activity of the catalyst in the reaction process is unstable, the fluctuation of the reaction temperature is large, the process parameters are difficult to control, and the polymer is caked.
Examples of the experiments
The characteristic properties of the polyethylene resin products obtained in examples 1 to 16 and comparative examples 1 to 11 were measured, respectively, by the following methods and conditions:
(1) High temperature gel chromatography (HT-GPC)
The weight average relative molecular mass and the relative molecular mass distribution of the polyethylene product were determined by high temperature gel chromatography: in this experiment, the relative molecular mass of polyethylene and the relative molecular mass distribution thereof were measured by means of a PL-220 type high temperature gel permeation chromatograph (Polymer Laboratories, inc.). In the experiment, 1,2, 4-trichlorobenzene is used as a solvent, and the measurement is carried out at 160 ℃. Processing data by using a universal correction method with narrow-distribution polystyrene as a standard sample;
(2) Melt Mass Flow Rate (MFR)
The melt flow rate meter was used in GB/T3682-2000, from CEAST 6942/000 Italy, at a temperature of 190 ℃.
The properties of the polyethylene resins obtained in examples 1 to 16 and comparative examples 1 to 11 are shown in Table 1.
As can be seen from the data in Table 1 above, the HDPE produced by the method has a wide density range, and basically meets the requirement that resin products of various density grades can be produced by using the same catalyst; the mass ratio of the vanadium raw material to the chromium and the vanadium is replaced, the performance of the catalyst is not influenced, and resin products with wide density range can be produced. Compared with HDPE produced by using traditional single chromium catalyst in the prior art, the HDPE has the advantages of narrow product density range and low polymerization activity; in the polymerization process of the polyethylene resin, when the butene/ethylene molar ratio is lower than 0.003 or exceeds 0.06, the polymerization activity is low, so that the butene/ethylene molar ratio is selected to be 0.003-0.06, the reaction activity is high, and the production is facilitated.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (5)
1. A method for synthesizing high-density polyethylene resin is characterized by comprising the steps of polymerizing ethylene monomer in the presence of a chromium-vanadium bimetallic active center catalyst under the protection of inert gas and introducing butylene and hydrogen;
the step of feeding butene and hydrogen comprises a first reaction stage and a second reaction stage which are independent of each other and feed butene and hydrogen in a butene/ethylene molar ratio of 0.003 to 0.06 and a hydrogen/ethylene molar ratio of 0.01 to 0.02;
the preparation method of the chromium-vanadium bimetallic catalyst comprises the following steps:
(1) Respectively loading a chromium element and a vanadium element on an inorganic carrier to prepare a first catalyst precursor loaded with a chromium-vanadium bimetallic element;
(2) Roasting the first catalyst precursor to prepare a second catalyst precursor containing an oxidation state chromium-vanadium bimetallic element;
(3) Carrying out reduction reaction on the second catalyst precursor to prepare a chromium-vanadium bimetallic catalyst containing a low-oxidation-state chromium-vanadium compound, and drying to obtain the catalyst;
in the step (3), the reduction reaction comprises the step of reducing the chromium element and the vanadium element in sequence in an inert atmosphere in the presence of a suitable organic metal reducing agent;
the elemental chromium-reduced organometallic reducing agent comprises diethylaluminum ethoxide;
the organometallic reducing agent for the reduction of the vanadium element comprises triethylaluminum.
2. The method of synthesizing high density polyethylene resin according to claim 1, wherein the reaction time ratio of the first reaction stage and the second reaction stage is 1:3-3:1.
3. the method for synthesizing a high density polyethylene resin according to claim 1 or 2, wherein in the step (1), the supporting step comprises a step of preparing salt solutions containing chromium element and vanadium element, respectively, and immersing the inorganic carrier in the salt solutions for physical adsorption, and a step of drying the first catalyst precursor after the supporting treatment.
4. The method of synthesizing high density polyethylene resin according to claim 3, characterized in that:
the salt containing chromium element comprises chromium trioxide, chromium acetate, ammonium chromate and/or basic chromium acetate;
the vanadium-containing salt comprises ammonium metavanadate and/or ammonium hexafluorovanadate;
the inorganic carrier is selected from granular porous inorganic oxide silica gel.
5. The method for synthesizing high density polyethylene resin according to claim 1 or 2, wherein in the step (2), the firing step comprises a step of firing at a low temperature of 100 to 300 ℃ and firing at a high temperature of 300 to 900 ℃, respectively;
the low-temperature roasting step is carried out in the atmosphere of air or inert gas;
the high-temperature roasting step is carried out in the air or oxygen atmosphere.
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| CN105294888A (en) * | 2014-06-06 | 2016-02-03 | 中国石油化工股份有限公司 | High-crystallinity broad-peak polyethylene resin and preparation method therefor |
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