CN116063595B - Ethylene polymerization catalyst, polyethylene resin obtained therefrom and process for producing the same - Google Patents
Ethylene polymerization catalyst, polyethylene resin obtained therefrom and process for producing the same Download PDFInfo
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- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 title claims abstract description 30
- 239000005977 Ethylene Substances 0.000 title claims abstract description 30
- 229920013716 polyethylene resin Polymers 0.000 title claims abstract description 17
- 239000002685 polymerization catalyst Substances 0.000 title claims abstract description 14
- 238000000034 method Methods 0.000 title claims description 11
- 230000008569 process Effects 0.000 title claims description 8
- 239000012018 catalyst precursor Substances 0.000 claims abstract description 68
- 239000003054 catalyst Substances 0.000 claims abstract description 65
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 40
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 38
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims abstract description 34
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000001301 oxygen Substances 0.000 claims abstract description 28
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 28
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 238000001035 drying Methods 0.000 claims abstract description 23
- 239000010453 quartz Substances 0.000 claims abstract description 22
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 19
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000001257 hydrogen Substances 0.000 claims abstract description 13
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 13
- 230000003647 oxidation Effects 0.000 claims abstract description 12
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 12
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 8
- 238000002360 preparation method Methods 0.000 claims abstract description 8
- 229910052751 metal Inorganic materials 0.000 claims abstract description 6
- 239000002184 metal Substances 0.000 claims abstract description 6
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 54
- 238000006722 reduction reaction Methods 0.000 claims description 30
- 230000009467 reduction Effects 0.000 claims description 20
- 150000001845 chromium compounds Chemical class 0.000 claims description 10
- GCPCLEKQVMKXJM-UHFFFAOYSA-N ethoxy(diethyl)alumane Chemical group CCO[Al](CC)CC GCPCLEKQVMKXJM-UHFFFAOYSA-N 0.000 claims description 10
- 239000002243 precursor Substances 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 7
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 claims description 5
- IAQRGUVFOMOMEM-UHFFFAOYSA-N butene Natural products CC=CC IAQRGUVFOMOMEM-UHFFFAOYSA-N 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 3
- 125000002524 organometallic group Chemical group 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 12
- 229920001903 high density polyethylene Polymers 0.000 abstract description 12
- 239000004700 high-density polyethylene Substances 0.000 abstract description 12
- 238000009826 distribution Methods 0.000 abstract description 11
- 238000007334 copolymerization reaction Methods 0.000 abstract description 10
- 238000002156 mixing Methods 0.000 abstract description 4
- 239000002994 raw material Substances 0.000 abstract description 3
- 230000001988 toxicity Effects 0.000 abstract description 3
- 231100000419 toxicity Toxicity 0.000 abstract description 3
- 239000011651 chromium Substances 0.000 description 21
- 229910052804 chromium Inorganic materials 0.000 description 21
- 229910052782 aluminium Inorganic materials 0.000 description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 5
- 238000012360 testing method Methods 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
- 239000004698 Polyethylene Substances 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 229920000573 polyethylene Polymers 0.000 description 3
- -1 polyethylenes Polymers 0.000 description 3
- 230000037048 polymerization activity Effects 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000005227 gel permeation chromatography Methods 0.000 description 2
- 229920001684 low density polyethylene Polymers 0.000 description 2
- 239000004702 low-density polyethylene 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
- 239000000843 powder Substances 0.000 description 2
- 239000000741 silica gel Substances 0.000 description 2
- 229910002027 silica gel Inorganic materials 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- HBHVBOUUMCIGMG-UHFFFAOYSA-N 2,6-Dibutyl-p-cresol Natural products CCCCC1=CC(O)=CC(CCCC)=C1O HBHVBOUUMCIGMG-UHFFFAOYSA-N 0.000 description 1
- LZFZQYNTEZSWCP-UHFFFAOYSA-N 2,6-dibutyl-4-methylphenol Chemical compound CCCCC1=CC(C)=CC(CCCC)=C1O LZFZQYNTEZSWCP-UHFFFAOYSA-N 0.000 description 1
- 238000004566 IR spectroscopy Methods 0.000 description 1
- 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
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- ZGHGWHCHTSTQAH-UHFFFAOYSA-N chromium ethene Chemical group [Cr].C=C ZGHGWHCHTSTQAH-UHFFFAOYSA-N 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000012685 gas phase polymerization Methods 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic 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
-
- 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)
Abstract
The invention relates to a preparation method of an ethylene polymerization catalyst, which comprises the following steps: drying the impregnated catalyst precursor in a drying oven, and introducing oxygen into a quartz tube for high-temperature oxidation; then stopping introducing oxygen, maintaining high temperature after nitrogen replacement, introducing normal hexane for prereduction, and adding a smaller amount of organic metal reducing agent to obtain a catalyst which is used in ethylene polymerization, wherein the activity is higher, the hydrogen blending copolymerization performance is excellent, the molecular weight distribution of the prepared polyethylene resin is wider, and meanwhile, the toxicity of the catalyst preparation raw material is low and the activity is high; and can be finally applied to the fields of high-density polyethylene (HDPE) production and the like.
Description
Technical Field
The present invention relates to an ethylene polymerization catalyst, a polyethylene resin (especially high-density polyethylene) obtained therefrom, and a process for producing the same. Compared with the traditional chromium catalyst, the chromium catalyst has high activity, good hydrogen blending copolymerization performance and wider molecular weight distribution of the produced polyethylene resin.
Background
Polyethylene (PE) resin is a thermoplastic polymerized from ethylene monomers and is a popular plastic product with the greatest yield and consumption in the world today, and mainly comprises Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), high Density Polyethylene (HDPE) and some polyethylenes with special properties. The high-density polyethylene has the advantages of good toughness, low price, easy molding and processing, good chemical corrosion resistance, and continuously expanding application range in various fields, and becomes one of the general plastics with the largest consumption. Currently known catalysts for preparing high density polyethylene are mainly Ziegler-Natta catalysts, chromium-based catalysts and metallocene catalysts, as well as other non-metallocene catalysts.
J.P Hogan and R.L.Bank both report silica gel supported chromium oxide catalysts in patent U.S. 2825721, which are inorganic chromium catalysts that are well known later. Leonard m.baker and Wayne l.carrick disclose an organochromium polyethylene catalyst, namely the S-2 organochromium catalyst of Union Carbide company in US3324101, US3324095 and CA 759121. Although the two catalyst structures are very similar, there is a large difference in catalysis and polymerization behavior. The inorganic chromium catalyst has high polymerization activity, the produced polyethylene product has wider molecular weight distribution, the comonomer insertion amount is higher, and the catalyst efficiency is higher; the S-2 organic chromium catalyst has lower polymerization activity, and has general hydrogen response and copolymerization performance. If the product grades are to be switched, the catalyst needs to be replaced, which causes complicated process.
The invention aims to overcome the defects of the prior art, and the impregnated catalyst precursor is dried in a baking oven and then is oxidized at high temperature by introducing oxygen into a quartz tube; and then stopping introducing oxygen, introducing a certain amount of n-hexane at the same temperature for prereduction after nitrogen replacement, and reducing by using a smaller amount of organic metal reducing agent (such as diethyl aluminum ethoxide), wherein the finally obtained catalyst has higher activity and excellent hydrogen blending copolymerization performance in an ethylene polymerization stage, and the prepared polyethylene resin has wider molecular weight distribution.
Disclosure of Invention
The invention relates to a preparation method of an ethylene polymerization catalyst, which comprises the steps of drying a dipped catalyst precursor in an oven, and introducing oxygen into a quartz tube for high-temperature oxidation; then stopping introducing oxygen, maintaining high temperature after nitrogen replacement, introducing normal hexane for prereduction, adding a smaller amount of organic metal reducing agent, and finally obtaining the catalyst which is used in ethylene polymerization, wherein the activity is higher, the hydrogen blending copolymerization performance is excellent, the molecular weight distribution of the prepared polyethylene resin is wider, and meanwhile, the toxicity of the catalyst preparation raw material is low and the activity is high; and can be finally applied to the fields of high-density polyethylene (HDPE) production and the like.
The catalyst is a chromium ethylene catalyst, and comprises an active component and an inorganic carrier, wherein the active component is a chromium metal compound, and the inorganic carrier is an inorganic oxide. The preparation method of the catalyst specifically comprises the following steps: first impregnating a chromium element precursor onto an inorganic support (e.g., silica gel) to obtain a catalyst precursor ①; drying the obtained catalyst precursor ①; then, the catalyst precursor ① is firstly subjected to high-temperature roasting at 300-800 ℃ in a quartz tube under the condition of introducing oxygen to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen and replacing nitrogen, maintaining high temperature, and injecting n-hexane into the quartz tube for pre-reduction to obtain a catalyst precursor ②; adding an organic metal reducing agent into the catalyst precursor ②, performing one-stage reduction reaction, and reducing chromium element to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state; and drying the catalyst ① to obtain the chromium metal active center catalyst.
Preferably, n-hexane is injected into a quartz tube for pre-reduction for 1 to 5 hours, and the flow is set to be 0.3 to 1.5L/min to obtain a catalyst precursor ②;
preferably, wherein the catalyst precursor ① is dried at a treatment temperature of 100 ℃; the catalyst precursor ① is calcined in a quartz tube at high temperature for 2 hours under the condition of introducing oxygen; the organometallic reducing agent is diethylaluminum ethoxide.
An ethylene polymerization catalyst obtained by the above-mentioned method for producing an ethylene polymerization catalyst.
A polyethylene resin prepared using the above ethylene polymerization catalyst.
The polyethylene resins of the invention may be prepared by any conventional ethylene polymerization (copolymerization) reaction. Such conventional ethylene polymerization (copolymerization) reactions include, but are not limited to, gas phase polymerization processes, slurry polymerization processes, liquid phase polymerization processes, and combinations thereof. In particular, the invention is particularly suitable for batch reactors. The temperature in the reactor is 90 ℃, the pressure is 1-3 MPa, the molar ratio of hydrogen to ethylene is 0.008-0.05, and the molar ratio of butene/ethylene is 0.003-0.06.
The invention also provides a special polymerization mode, namely comonomer addition is different from the conventional method, and the specific implementation method is as follows:
Firstly, treating a polymerization kettle at a high temperature under a vacuum state, supplementing high-purity nitrogen for standby, adding a dry powder catalyst into the polymerization kettle under the protection of the high-purity nitrogen after metering, stirring after vacuumizing, introducing hot water into a jacket to raise the temperature of the kettle to a specified temperature, slowly adding ethylene gas to the reaction pressure, and starting the polymerization reaction. The polymerization pressure is kept constant by a mass flowmeter and a pressure sensor through a control system, the polymerization temperature is controlled by a combined water bath through a control system adjusting an on-line heater and a circulating water pump, and the addition of the comonomer and the hydrogen is added through independent pipelines. After the polymerization is started, the reaction is carried out at constant temperature and constant pressure. The polymerization temperature was 90 ℃.
High density polyethylene resin performance test prepared with the catalyst:
Melt Mass Flow Rate (MFR): the test is carried out according to GB/T3682-2000, the test temperature is 190 ℃, and the load is 2.16kg.
Density: testing is performed according to GB/T1033.2-2010.
Molecular weight and molecular weight distribution index: gel Permeation Chromatography (GPC) is used in combination with infrared spectroscopy to measure weight average molecular weight and branching degree, solvent and mobile phase are 1,2, 4-trichlorobenzene (containing 0.025% antioxidant 2, 6-dibutyl-p-cresol), column temperature is 150deg.C, flow rate is 1.0ml/min, and narrow-distribution polystyrene standard sample is used for universal calibration.
The invention has the following beneficial technical effects:
in the preparation process of the catalyst, a certain amount of n-hexane is introduced into a quartz tube for pre-reduction according to a certain range of reduction time, and the obtained catalyst has high activity; the catalyst is used for ethylene polymerization reaction, the activity is high, and the polymerization process uses butene comonomer, so that the copolymerization performance and the hydrogen regulation performance are good; the molecular weight distribution of the prepared polyethylene resin is wider; meanwhile, the toxicity of the raw materials for preparing the catalyst is low, and the activity is high; and can be finally applied to the fields of high-density polyethylene (HDPE) production and the like.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The invention is further described below with reference to the following examples, which are set forth in detail and are illustrative of the methods of testing:
Example 1
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① obtained above was oven dried at a drying temperature of 100 ℃.
(3) Then, roasting the catalyst precursor ① at a high temperature of 600 ℃ for 2 hours under the condition that oxygen is introduced into a quartz tube to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen, maintaining 600 ℃ after nitrogen replacement, introducing n-hexane, and pre-reducing for 1 hour, wherein the flow is set to be 1.5L/min, thus obtaining the catalyst precursor ②.
(4) The catalyst precursor ② is added into diethyl aluminum ethoxide (the molar ratio of aluminum to chromium is 2), a one-stage reduction reaction is carried out for a specific time under a reduction condition, and chromium element is reduced to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state.
(5) And drying the catalyst ① to obtain the chromium metal active center catalyst.
Polymerization stage: (a) Firstly, treating a polymerization kettle at a high temperature under a vacuum state, supplementing high-purity nitrogen for standby, adding a dry powder catalyst into the polymerization kettle under the protection of the high-purity nitrogen after metering, stirring after vacuumizing, introducing hot water into a jacket to raise the temperature of the kettle to a specified temperature, slowly adding ethylene gas to the reaction pressure, and starting the polymerization reaction. The polymerization pressure is kept constant by a mass flowmeter and a pressure sensor through a control system, the polymerization temperature is controlled by a combined water bath through a control system adjusting an on-line heater and a circulating water pump, and the addition of the comonomer and the hydrogen is added through independent pipelines. After the polymerization is started, the reaction is carried out at constant temperature and constant pressure. The polymerization temperature was 90℃and the pressure was 1.2MPa, the molar ratio of hydrogen to ethylene was 0.05 and the molar ratio of butene/ethylene was 0.06.
Example 2
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① obtained above was oven dried at a drying temperature of 100 ℃.
(3) Then, roasting the catalyst precursor ① at a high temperature of 600 ℃ for 4 hours under the condition that oxygen is introduced into a quartz tube to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen, maintaining 600 ℃ after nitrogen replacement, introducing n-hexane, and pre-reducing for 3 hours, wherein the flow is set to be 1.0L/min, thus obtaining the catalyst precursor ②.
(4) The catalyst precursor ② is added into diethyl aluminum ethoxide (the molar ratio of aluminum to chromium is 2), a one-stage reduction reaction is carried out for a specific time under a reduction condition, and chromium element is reduced to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state.
(5) And drying the catalyst ① to obtain the chromium metal active center catalyst. The polymerization stage was the same as in example 1.
Example 3
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① obtained above was oven dried at a drying temperature of 100 ℃.
(3) Then, roasting the catalyst precursor ① at a high temperature of 600 ℃ for 4 hours under the condition that oxygen is introduced into a quartz tube to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen, maintaining 600 ℃ after nitrogen replacement, introducing n-hexane, and pre-reducing for 5 hours, wherein the flow is set to be 0.5L/min, thus obtaining the catalyst precursor ②.
(4) The catalyst precursor ② is added into diethyl aluminum ethoxide (the molar ratio of aluminum to chromium is 2), a one-stage reduction reaction is carried out for a specific time under a reduction condition, and chromium element is reduced to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state.
(5) And drying the catalyst ① to obtain the chromium metal active center catalyst. The polymerization stage was the same as in example 1.
Example 4
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① obtained above was oven dried at a drying temperature of 100 ℃.
(3) Then, roasting the catalyst precursor ① at a high temperature of 600 ℃ for 4 hours under the condition that oxygen is introduced into a quartz tube to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen, maintaining 600 ℃ after nitrogen replacement, introducing n-hexane, and pre-reducing for 5 hours, wherein the flow is set to be 0.3L/min, thus obtaining the catalyst precursor ②.
(4) The catalyst precursor ② is added into diethyl aluminum ethoxide (the molar ratio of aluminum to chromium is 2), a one-stage reduction reaction is carried out for a specific time under a reduction condition, and chromium element is reduced to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state.
(5) And drying the catalyst ① to obtain the chromium metal active center catalyst. The polymerization stage was the same as in example 1.
Example 5
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① obtained above was oven dried at a drying temperature of 100 ℃.
(3) Then, roasting the catalyst precursor ① at a high temperature of 600 ℃ for 4 hours under the condition that oxygen is introduced into a quartz tube to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen, maintaining 600 ℃ after nitrogen replacement, introducing n-hexane, and pre-reducing for 3 hours, wherein the flow is set to be 1.5L/min, so as to obtain the catalyst precursor ②.
(4) The catalyst precursor ② is added with an organic metal reducing agent, and a one-stage reduction reaction is carried out for a specific time under the reduction condition, so as to reduce chromium element, and a pre-reduced catalyst ① containing chromium compound in a low oxidation state is obtained.
(5) And drying the catalyst ① to obtain the chromium metal active center catalyst. The polymerization stage was the same as in example 1.
Comparative example 1
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① was dried in an oven at a drying temperature of 100 ℃.
(3) Then, roasting the catalyst precursor ① at a high temperature of 600 ℃ for 2 hours under the condition that oxygen is introduced into a quartz tube to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen, maintaining 600 ℃ after nitrogen replacement, introducing n-hexane for pre-reduction for 0.5h, and setting the flow to be 0.2L/min to obtain the catalyst precursor ②.
(4) The catalyst precursor ② is added into diethyl aluminum ethoxide (the molar ratio of aluminum to chromium is 2), a one-stage reduction reaction is carried out for a specific time under a reduction condition, and chromium element is reduced to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state.
(5) And drying the catalyst ① to obtain the final product chromium metal active center catalyst with good fluidity.
The polymerization stage was the same as in example 1.
Comparative example 2
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① was dried in an oven at a drying temperature of 100 ℃.
(3) Then, roasting the catalyst precursor ① at a high temperature of 600 ℃ for 2 hours under the condition that oxygen is introduced into a quartz tube to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen, maintaining 600 ℃ after nitrogen replacement, introducing n-hexane for pre-reduction for 6 hours, and setting the flow to be 2.0L/min to obtain a catalyst precursor ②.
(4) The catalyst precursor ② is added into diethyl aluminum ethoxide (the molar ratio of aluminum to chromium is 2), a one-stage reduction reaction is carried out for a specific time under a reduction condition, and chromium element is reduced to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state.
(5) And drying the catalyst ① to obtain the final product chromium metal active center catalyst with good fluidity.
The polymerization stage was the same as in example 1.
Comparative example 3
(1) Impregnating a chromium precursor onto an inorganic support to obtain a catalyst precursor ①
(2) The catalyst precursor ① was dried in an oven at a drying temperature of 100 ℃.
(3) Then, the catalyst precursor ① is roasted for 4 hours at a high temperature of 600 ℃ under the condition that oxygen is introduced into a quartz tube, and then the temperature is reduced, nitrogen is introduced to replace the oxygen, so as to obtain the catalyst precursor ② containing high-valence chromium element.
(4) The catalyst precursor ② is added into diethyl aluminum ethoxide (the molar ratio of aluminum to chromium is 3), a one-stage reduction reaction is carried out for a specific time under a reduction condition, and chromium element is reduced to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state.
(5) And drying the catalyst ① to obtain the final product chromium metal active center catalyst with good fluidity.
The polymerization stage was the same as in example 1.
TABLE 1
TABLE 2
As can be seen from the experimental data of the invention, in the preparation method of the ethylene polymerization catalyst, a certain amount of n-hexane is introduced into a quartz tube for pre-reduction according to a certain range of reduction time at a high temperature of the catalyst, so that the activity of the obtained catalyst is high; the catalyst is used for polymerization reaction, and the polymerization process uses butene comonomer, so that the copolymerization performance and the hydrogen regulation performance are good; as can be seen from the PDI index, the molecular weight distribution of the prepared polyethylene resin is wider. In comparative examples 1 and 2, however, the polymerization activity of the catalyst was low because the pre-reduction time and flow rate setting after the introduction of n-hexane did not fall within the ranges described in the present invention; the molecular weight distribution is narrow as can be seen from the PDI values. In comparative example 3, no quartz tube was charged with n-hexane for the pre-reduction step, and the catalyst activity was low, the copolymerization performance and hydrogen-adjusting performance were poor, and the molecular weight distribution of the prepared polyethylene resin was narrow.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (7)
1. A preparation method of an ethylene polymerization catalyst comprises the steps of firstly impregnating a chromium element precursor on an inorganic carrier to obtain a catalyst precursor ①; drying the obtained catalyst precursor ①; then, the catalyst precursor ① is firstly subjected to high-temperature roasting at 300-800 ℃ in a quartz tube under the condition of introducing oxygen to obtain the catalyst precursor containing high-valence chromium element; then stopping introducing oxygen and replacing nitrogen, maintaining high temperature, and injecting n-hexane into the quartz tube for pre-reduction to obtain a catalyst precursor ②; adding an organic metal reducing agent into the catalyst precursor ②, performing one-stage reduction reaction, and reducing chromium element to obtain a pre-reduced catalyst ① containing chromium compounds in a low oxidation state; drying the catalyst ① to obtain a chromium metal active center catalyst;
wherein, n-hexane is injected into a quartz tube for pre-reduction for 1 to 5 hours, and the flow is set to be 0.3 to 1.5L/min to obtain a catalyst precursor ②.
2. The method for preparing an ethylene polymerization catalyst as claimed in claim 1, wherein the catalyst precursor ① is dried at a temperature of 100 ℃; the catalyst precursor ① is calcined in a quartz tube at high temperature for 2 hours under the condition of introducing oxygen; the organometallic reducing agent is diethylaluminum ethoxide.
3. An ethylene polymerization catalyst obtained by the process for producing an ethylene polymerization catalyst according to claim 1 or 2.
4. A polyethylene resin prepared using the ethylene polymerization catalyst of claim 3.
5. A process for producing the polyethylene resin according to claim 4, which is produced in a batch reactor; the temperature in the reactor is 90 ℃, the pressure is 1-3 MPa, the molar ratio of hydrogen to ethylene is 0.008-0.05, and the molar ratio of butene/ethylene is 0.003-0.06.
6. A process for preparing the polyethylene resin as claimed in claim 4, wherein the polymerization reactor is treated at high temperature and vacuum state, high-purity nitrogen is supplemented for standby, the prepared catalyst is metered and then added into the polymerization reactor under the protection of high-purity nitrogen, the mixture is stirred after vacuumizing, the reactor is heated to a specified temperature by a jacket through hot water, ethylene gas is slowly added to a reaction pressure, and a constant-temperature and constant-pressure polymerization reaction is started.
7. The process for producing a polyethylene resin according to claim 6, wherein the polymerization pressure is kept constant by a mass flow meter and a pressure sensor through a control system, the polymerization temperature is controlled by a combined water bath by adjusting an in-line heater and a circulating water pump through the control system, and the addition of the comonomer and the hydrogen is carried out through separate lines.
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| CN107778387A (en) * | 2016-08-29 | 2018-03-09 | 中国石油化工股份有限公司 | Catalyst for preparing broad peak distribution polyethylene resins and preparation method thereof and the polyvinyl resin prepared |
| CN111087500A (en) * | 2018-10-24 | 2020-05-01 | 中国石油化工股份有限公司 | Chromium-vanadium bimetallic catalyst and application thereof in catalytic synthesis of high-density polyethylene |
| CN112638954A (en) * | 2018-09-17 | 2021-04-09 | 切弗朗菲利浦化学公司 | Light treatment of chromium catalysts and related catalyst preparation systems and polymerization processes |
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| CN106317267B (en) * | 2015-06-16 | 2018-12-28 | 中国石油化工股份有限公司 | A kind of catalytic component and preparation method thereof for vinyl polymerization |
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| CN112638954A (en) * | 2018-09-17 | 2021-04-09 | 切弗朗菲利浦化学公司 | Light treatment of chromium catalysts and related catalyst preparation systems and polymerization processes |
| CN111087500A (en) * | 2018-10-24 | 2020-05-01 | 中国石油化工股份有限公司 | Chromium-vanadium bimetallic catalyst and application thereof in catalytic synthesis of high-density polyethylene |
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