CN108203483B - Preparation method of polyethylene - Google Patents
Preparation method of polyethylene Download PDFInfo
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- CN108203483B CN108203483B CN201611187797.6A CN201611187797A CN108203483B CN 108203483 B CN108203483 B CN 108203483B CN 201611187797 A CN201611187797 A CN 201611187797A CN 108203483 B CN108203483 B CN 108203483B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2410/00—Features related to the catalyst preparation, the catalyst use or to the deactivation of the catalyst
- C08F2410/04—Dual catalyst, i.e. use of two different catalysts, where none of the catalysts is a metallocene
Abstract
The invention relates to a preparation method of polyethylene, wherein a reactor used in the preparation method is a gas-phase fluidized bed, alpha-olefin is used as a comonomer, a supported chromium-molybdenum composite catalyst is adopted, and the preparation method of the supported chromium-molybdenum composite catalyst comprises the following steps: immersing a porous inorganic carrier into an aqueous solution containing an inorganic chromium source, and performing immersion, activation and roasting; continuously immersing into an organic solution containing an organic chromium source and an organic molybdenum source, and performing immersion drying; the inorganic chromium source, the organic chromium source and the organic molybdenum source are active components, and the total loading of Cr and Mo in the active components is 0.01-20 wt% of the total weight of the catalyst; the molar ratio of Cr to Mo is 0.01: 0.99-0.99: 0.01; the molar ratio of the organic chromium source to Cr in the inorganic chromium source is 1: 9-9: 1. The polyethylene product prepared by the invention has the characteristics of high monomer content, excellent comonomer distribution uniformity and the like.
Description
Technical Field
The invention relates to a preparation method of polyethylene, in particular to a preparation method for producing polyethylene by adopting a supported chromium-molybdenum composite catalyst in a gas-phase fluidized bed process.
Background
Chromium-based catalysts were first used in the production of polyethylene as an important class of ethylene polymerization catalysts. From the first on silica gel (SiO)2) Or silica gel-alumina (SiO)2-Al2O3) The research on the supported chromium oxide catalyst has been successful to date, and it has been found that the relative molecular mass (hereinafter referred to simply as molecular weight) of the product can be changed by the preparation method of silica gel and the activation method after supporting the chromium-based catalyst. The supported chromium catalyst is widely applied to PE production processes of a solution method, a slurry method and a gas phase method. Hogan and Banks from Phillips have discovered CrO for ethylene polymerization in 19513/SiO2Catalyst, Unide-Carbide developed the best known Cp on the basis of Phillips2Cr type catalyst, thereby pioneering chromium-based catalysts as ethylene polymerization catalystsA very important field.
USP2825721 is the invention patent of chromium-based polyethylene catalyst first obtained by Phillips oil company in 1958, which first reports that chromium oxide has high ethylene polymerization activity after being supported on the surface of silica gel or alumina, and which was later put into industrial production by Phillips oil company for high-density polyethylene used in slurry loop polyethylene process, and the chromium-supporting amount of the catalyst is 1% (weight percent). After more than 50 years of development, a series of modification and improvement are carried out, and six hundred patents (Phillips oil company owns three hundred patents) exist so far, wherein the patent technologies which are widely applied up to now comprise titanium modified and aluminum modified Phillips chromium catalyst patent technologies.
USP4049896 describes a patented technology of aluminum modified Phillips chromium catalyst, which is first reported by USI/Equistar company in 1977, and is mainly characterized in that a metal aluminum salt (finally converted into aluminum oxide in the baking process) is introduced in the catalyst preparation process to modify the Phillips chromium catalyst, and the aluminum modification can improve the polymerization activity of the catalyst, reduce the molecular weight of a polymer, enhance the molecular weight regulation means, widen the molecular weight distribution, improve the processability and the product physical property, enhance the stress cracking resistance of the polymer and the like. Related improvements are USP4052544 and the like.
USP3780011 introduces a titanium modified Phillips chromium-based catalyst patent technology, which is first reported by Chemplex/Equistar company in 1971, and mainly modifies Phillips chromium-based catalyst by introducing metal titanium salt (finally converted into titanium oxide in the roasting process) in the catalyst preparation process, wherein the titanium modification can improve the polymerization activity of the catalyst, reduce the molecular weight of the polymer so as to enhance the molecular weight regulation means, widen the molecular weight distribution so as to improve the processability and the product physical property, enhance the stress cracking resistance of the polymer, enhance the extrusion expansion and the like. Related improvements are USP4053436 and the like.
EP 56274 describes a fluorine modified chromium based catalyst technology, inorganic fluorine being added to the chromium oxide catalyst prior to activation. The addition of inorganic fluorine (such as HF, (NH4)2SiF6, (NH4)3BF6, etc.) can change the hydrogen response of the chromium oxide catalyst and obtain a HDPE product with narrow molecular weight distribution. Further modification of the titanium impregnated chromia catalyst with fluorine increases the comonomer addition rate and improves the copolymerisation properties of the polymer and as the fluorine content increases both the low molecular weight fraction and the melt index of the copolymer decrease. The promotion of fluorine on chromium catalysts is due to the reaction of fluorine with surface silanol groups to release water, forming surface Si — F bonds. From the CO low-temperature infrared spectrogram, the fluorine treatment reduces the electron cloud density of chromium atoms and changes the distribution of active sites, thereby improving the physical properties of PE products.
USP5032651 discloses a method for compounding a zirconium metallocene catalyst and a chromium-containing catalyst to synthesize a polyethylene resin with high hardness and good environmental stress cracking resistance, wherein the polyethylene resin is particularly suitable for producing film-grade products.
CN1350007A describes a nickel modified ethylene polymerization chromium catalyst and a preparation method thereof, the catalyst prepared by the method has high polymerization activity and better copolymerization performance, and the produced polymer has higher molecular weight.
CN1296020A describes a titanium and nickel modified ethylene polymerization chromium catalyst and its preparation method, the catalyst prepared by the method has high polymerization activity and better copolymerization performance, the produced polymer has higher melt flow rate and wider molecular weight distribution, and the chromium, nickel and titanium exist in oxide form after being activated.
CN1858072 describes a titanium modified supported chromium-based catalyst and a preparation method thereof, wherein the carrier of the catalyst is silica gel, and the titanium compound and the chromium compound are supported on the silica gel carrier, and the prepared catalyst has strong hydrogen regulation capability, can be used for producing polymers with high melt index, has low polymer shear response (HLMI/MI ratio), and is suitable for producing ethylene homopolymers and copolymers with wide molecular weight distribution for producing films and pipes.
The invention relates to a preparation method for producing polyethylene by adopting a bichromium and molybdenum composite catalyst in a gas-phase fluidized bed process, which can improve the copolymerization performance of a polyethylene product and has no related report adopting the method at present.
Disclosure of Invention
The invention aims to provide a method for preparing polyethylene in a gas-phase fluidized bed by adopting a supported chromium-molybdenum composite catalyst, and the polyethylene prepared by adopting the method has the characteristic of good copolymerization performance.
In order to achieve the above purpose, the invention provides a preparation method of polyethylene, the reactor used in the preparation method is a gas phase fluidized bed, alpha-olefin is used as comonomer, a load type chromium-molybdenum composite catalyst is adopted,
the supported chromium-molybdenum composite catalyst comprises an active component and a porous inorganic carrier, wherein the active component comprises a chromium source and an organic molybdenum source, the chromium source comprises an organic chromium source and/or an inorganic chromium source, and the preparation method comprises the following steps:
(1) immersing the porous inorganic carrier into an aqueous solution of an inorganic chromium source for 1-12h at 25-100 ℃, drying at 100-300 ℃ for 5-20h, and then activating and roasting;
(2) immersing the product obtained in the step (1) into an organic solution containing an organic chromium source and an organic molybdenum source for 1-12h at the immersion temperature of 25-100 ℃, and then drying for 5-20h in a nitrogen atmosphere at the temperature of 100-300 ℃;
the total loading amount of Cr and Mo in the active component is 0.01-20 wt%, preferably 0.05-15 wt%, and more preferably 0.1-10 wt% of the total weight of the catalyst; the molar ratio of Cr to Mo is 0.01: 0.99-0.99: 0.01, preferably 0.25: 0.75-0.75: 0.25, more preferably 0.4: 0.6-0.6: 0.4.
Specifically, two chromium sources are selected from the organic chromium source and the inorganic chromium source, and the molar ratio of Cr in the two chromium sources is 1: 9-9: 1, preferably 2: 8-8: 2, more preferably 3: 6-6: 3
In the preparation method of the polyethylene, the inorganic chromium source is preferably one or two of chromium trioxide, chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium chromate, ammonium dichromate and basic chromium acetate.
In the preparation method of the polyethylene, the organic chromium source is preferably one or two selected from bis-triphenylsilyl chromate, chromocene and organosilane chromate.
In the method for producing polyethylene according to the present invention, the organic molybdenum source is preferably one of molybdenum dialkyl dithiophosphate, molybdenum dialkyl dithiophosphate containing nitrogen, molybdenum dialkyl dithiocarbamate, molybdenum amine complex, molybdenum naphthenate, and molybdenum alkyl salicylate.
In the method for preparing polyethylene according to the present invention, preferably, the porous inorganic support is obtained by modifying an inorganic support.
The preparation method of the polyethylene of the present invention is characterized in that the inorganic carrier is preferably at least one selected from the group consisting of silica, alumina, titania, zirconia, magnesia, calcium oxide, inorganic clay and montmorillonite.
The preparation method of the supported polyethylene catalyst comprises the steps of preferably preparing the inorganic carrier with the average particle diameter of 1-100 microns and the pore volume of 0.5cm3/g～10.0cm3A surface area of 50m is preferred2/g～1000m2/g。
The preparation method of the supported polyethylene catalyst is characterized in that the modification is preferably aluminum modification: impregnating the inorganic support with a solution of an aluminium salt, preferably selected from Al (NO)3)3、AlC13And Al2(SO4)3One kind of (1).
The preparation method of the supported polyethylene catalyst is characterized in that the modification is preferably titanium modification, and the modification is carried out by adopting an impregnation method or a Cogel method.
The preparation method of the supported polyethylene catalyst is characterized in that the modification is preferably fluorine modification: the inorganic support is co-impregnated with a fluorine-containing component.
The preparation method of the polyethylene, disclosed by the invention, has the advantage that the reaction temperature in the reactor is preferably 70-100 ℃.
The preparation method of the polyethylene is characterized in that the sum of the mole percentages of water and oxygen in the reactor is preferably less than 1 ppm.
In the method for producing polyethylene according to the present invention, it is preferable that: based on the total mole number of the gas in the reactor as 100%, the mole percentage content of nitrogen is 30-50%, and the mole percentage content of ethylene is 35-55%; the molar ratio of the alpha-olefin to the ethylene is 0.01-0.09: 1, and the molar ratio of the hydrogen to the ethylene is 0.1-0.2: 1.
The preparation method of the polyethylene, disclosed by the invention, is characterized in that the oxygen concentration in the reactor is preferably 10-100 ppb.
The preparation method of the polyethylene is characterized in that the alpha-olefin is preferably any two or three of 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene.
The density of the polyethylene prepared by the preparation method is 0.930-0.950 g/cm3The melt flow rate of the 21.6kg weight is 2.0-50.0 g/10min, the melt flow rate of the 5.0kg weight is 0.1-5.0g/10min, and the ratio of the two ranges from 15 to 30.
The polyethylene prepared by the preparation method can be used for producing film products, hollow products, pipe products and injection products.
Detailed Description
The following examples are intended to further illustrate the process of the present invention but should not be construed as limiting thereof.
In the following examples, the porous inorganic support was obtained by modifying an inorganic support.
The Al modification can adopt a gel method to prepare Al2O3The modified inorganic carrier can also adopt Al which can be realized by dipping the inorganic carrier in an aluminum salt solution2O3Modified, the aluminium salt solution is selected from Al (NO)3)3、AlC13And Al2(SO4)4At least one of (1). The suitable conditions for the process of modifying the inorganic carrier are as follows: preparing an aqueous solution of aluminum salt with the concentration of 10-25 wt%, adding diluted acid to adjust the pH to 1-1.8, heating to 40-60 ℃, and adding SiO2Soaking for 12-24 h under strong stirring, washing with distilled water until the pH is 7,drying and roasting to obtain Al2O3A modified porous inorganic support;
the titanium modified porous inorganic support can be prepared by an impregnation method or a Cogel method. Impregnation method, i.e. impregnating inorganic carrier in titanate or TiC14Titanate or TiC14The titanium is loaded on the surface of the carrier through chemical reaction with hydroxyl on the surface of the carrier, and the titanium modified carrier is prepared after calcination. Typically a hydrocarbon such as hexane or heptane is used as the organic solvent. The Cogel method is to dissolve soluble titanium salt in silicate, such as sodium silicate, and increase the pH of the solution to form the carrier and TiO2Or dissolving silicon ester and titanium ester in alcohol or acetone, adding small amount of water to obtain carrier and TiO2Co-gel of (a);
the fluorine modified porous inorganic carrier can be prepared by impregnation method, and the inorganic carrier is impregnated with (NH)4)2SiF6In solution, (NH)4)2SiF6The concentration is 1 to 10 percent of mole fraction.
When the porous inorganic carrier loads the active component, the active component comprises a chromium source and an organic molybdenum source, the chromium source comprises an organic chromium source and/or an inorganic chromium source, and the following steps of loading the active component are specifically carried out in the following embodiment:
(1) immersing a porous inorganic carrier into an aqueous solution containing an inorganic chromium source, wherein the immersion time is 6 hours, the immersion temperature is 50 ℃, then drying for 15 hours at 200 ℃, and then activating and roasting;
(2) and (2) immersing the product obtained in the step (1) into an organic solution containing an organic chromium source and an organic molybdenum source, wherein the immersion time is 10 hours, the immersion temperature is 75 ℃, and then, drying for 10 hours in a nitrogen atmosphere at the temperature of between 100 ℃ and 300 ℃.
Example 1
Chromium trioxide, chromium nitrate and molybdenum alkyl salicylate are loaded on a porous inorganic carrier (inorganic carrier silicon dioxide), the total loading amount of Cr and Mo metals on the porous inorganic carrier is determined to be 2.7 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.75:0.25, and the molar ratio of chromium trioxide of two chromium sources to Cr in chromium nitrate is 4:6, so that the supported chromium-molybdenum composite catalyst is obtained.
The conditions of the composite catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 90 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage content of the nitrogen is 39 percent, and the mole percentage content of the ethylene in the reactor is 44 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.05, and the molar ratio of hydrogen to ethylene in the reactor was 0.17; the oxygen concentration in the reactor was 50ppb, and the polymerized monomer alpha-olefin was 1-butene and 1-pentene.
The prepared polyethylene had a density of 0.9379g/cm3The melt flow rate of the 21.6kg weight was 30.0g/10min, and the melt flow rate of the 5.0kg weight was 1.7g/10min, with a ratio in the range of 17.6.
Example 2
Chromium chloride, chromocene and molybdenum dialkyl dithiocarbamate are loaded on a porous inorganic carrier (inorganic carrier aluminum oxide), the total loading amount of Cr and Mo metals on the porous inorganic carrier is determined to be 2.1 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.99:0.01, the molar ratio of chromium chloride of two chromium sources to Cr in the chromocene is 5:5, and the supported chromium-molybdenum composite catalyst is obtained.
The conditions of the composite catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 100 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage content of the nitrogen is 30 percent, and the mole percentage content of the ethylene in the reactor is 55 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.03 and the molar ratio of hydrogen to ethylene in the reactor was 0.18; the oxygen concentration in the reactor was 80ppb, and the polymerized monomer alpha-olefin was 1-butene and 1-hexene.
The prepared polyethylene had a density of 0.9392g/cm3The melt flow rate of the 21.6kg weight was 22.0g/10min, and the melt flow rate of the 5.0kg weight was 1.2g/10min, with the ratio ranging from 18.3.
Example 3
Chromium oxide, chromium acetate and nitrogen-containing dialkyl molybdenum dithiophosphate are loaded on a porous inorganic carrier (inorganic carrier zirconia), the total loading amount of Cr and Mo metals on the porous inorganic carrier is determined to be 3.25 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.83:0.17, and the molar ratio of Cr in two chromium sources is 3:7, so that the supported chromium-molybdenum composite catalyst is obtained.
The conditions of the composite catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 85 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; the total mole number of the gas in the reactor is 100 percent, the mole percentage content of the nitrogen is 37 percent, and the mole percentage content of the ethylene in the reactor is 42 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.07, and the molar ratio of hydrogen to ethylene in the reactor was 0.15; the oxygen concentration in the reactor was 10ppb, and the polymerized monomer alpha-olefin was 1-butene and 1-octene.
The prepared polyethylene had a density of 0.9349g/cm3The melt flow rate of the 21.6kg weight was 50.0g/10min, and the melt flow rate of the 5.0kg weight was 3.1g/10min, with a ratio in the range of 16.1.
Example 4
Basic chromium acetate, chromocene and molybdenum alkyl salicylate are loaded on a porous inorganic carrier (inorganic carrier magnesia), the total loading amount of Cr and Mo metals on the porous inorganic carrier is determined to be 5.32 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.36:0.64, and the molar ratio of Cr in the two chromium source basic chromium acetate and chromocene is 9:1, so that the supported chromium-molybdenum composite catalyst is obtained.
The conditions of the composite catalyst for preparing and producing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 70 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage content of the nitrogen is 30 percent, and the mole percentage content of the ethylene in the reactor is 35 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.01, and the molar ratio of hydrogen to ethylene in the reactor was 0.20; the oxygen concentration in the reactor was 100ppb, and the polymerized monomer alpha-olefin was 1-pentene and 1-octene.
The prepared polyethylene had a density of 0.9472g/cm3The melt flow rate of the 21.6kg weight was 43.0g/10min, and the melt flow rate of the 5.0kg weight was 2.7g/10min, with a ratio in the range of 16.0.
Example 5
Basic chromium acetate, chromium sulfate and molybdenum oxydisulfhiophosphate are loaded on a porous inorganic carrier (inorganic carrier titanium dioxide), the total loading amount of Cr and Mo metals on the porous inorganic carrier is determined to be 4.0 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.01:0.99, and the molar ratio of Cr in the two chromium source basic chromium acetate and chromium sulfate is 1:9, so as to obtain the supported chromium-molybdenum composite catalyst.
The conditions of the composite catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 95 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage content of the nitrogen is 50 percent, and the mole percentage content of the ethylene in the reactor is 46 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.09, and the molar ratio of hydrogen to ethylene in the reactor was 0.16; the oxygen concentration in the reactor was 40ppb, and the polymerized monomer alpha-olefin was 1-pentene and 1-decene.
The prepared polyethylene had a density of 0.9357g/cm3The melt flow rate of the 21.6kg weight was 38.0g/10min, and the melt flow rate of the 5.0kg weight was 2.2g/10min, with a ratio in the range of 17.3.
Example 6
Basic chromium acetate, bis-triphenylsilyl chromate and molybdenum dialkyl dithiophosphate are loaded on a porous inorganic carrier (inorganic carrier inorganic clay), the total loading amount of Cr and Mo metals on the porous inorganic carrier is determined to be 4.8 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.42:0.56, and the molar ratio of Cr in the two chromium source basic chromium acetate and the bis-triphenylsilyl chromate is 7:3, so that the supported chromium-molybdenum composite catalyst is obtained.
The conditions of the composite catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 80 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage content of the nitrogen is 45 percent, and the mole percentage content of the ethylene in the reactor is 40 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.06, and the molar ratio of hydrogen to ethylene in the reactor was 0.14; the oxygen concentration in the reactor was 20ppb, and the polymerized monomer alpha-olefin was 1-pentene and 1-hexene.
The prepared polyethylene had a density of 0.9489g/cm3The melt flow rate of the 21.6kg weight was 15.0g/10min, the melt flow rate of the 5.0kg weight was 0.8g/10min, and the ratio of the two ranged from 18.8.
Example 7
Basic chromium acetate, ammonium dichromate and molybdenum naphthenate are loaded on a porous inorganic carrier (inorganic carrier calcium oxide), the total loading of Cr and Mo metals on the porous inorganic carrier is determined to be 9.8 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.72:0.28, and the molar ratio of Cr in the two chromium source basic chromium acetate and the ammonium dichromate is 6:4, so that the supported chromium-molybdenum composite catalyst is obtained.
The conditions of the composite catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 75 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; the mol percentage of nitrogen is 33 percent and the mol percentage of ethylene is 37 percent in the reactor, based on the total mole number of the gas in the reactor as 100 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.04 and the molar ratio of hydrogen to ethylene in the reactor was 0.13; the oxygen concentration in the reactor was 30ppb, and the polymerized monomer alpha-olefin was 1-butene and 1-hexene.
The prepared polyethylene had a density of 0.9454g/cm3The melt flow rate of the 21.6kg weight was 27.0g/10min, and the melt flow rate of the 5.0kg weight was 1.4g/10min, with a ratio in the range of 19.0.
Example 8
Chromium acetate, ammonium chromate and a molybdenum amine complex are loaded on a porous inorganic carrier (inorganic carrier montmorillonite), the total loading of Cr and Mo metals on the porous inorganic carrier is determined to be 12.1 wt% of the total weight of the catalyst, the molar ratio of Cr to Mo is 0.59:0.41, and the molar ratio of Cr in chromium acetate and ammonium chromate of two chromium sources is 8:2, so that the supported chromium-molybdenum composite catalyst is obtained.
The conditions of the composite catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature of the reactor is 85 ℃, and the sum of the mole percentage content of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage of the nitrogen is 42 percent, and the mole percentage of the ethylene in the reactor is 50 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.08 and the molar ratio of hydrogen to ethylene in the reactor was 0.16; the oxygen concentration in the reactor was 60ppb, and the polymerized monomer alpha-olefin was 1-butene and 1-hexene.
The prepared polyethylene had a density of 0.9428g/cm3The melt flow rate of the 21.6kg weight was 3.0g/10min, and the melt flow rate of the 5.0kg weight was 0.14g/10min, with the ratio ranging from 21.5.
Comparative example 1
Chromium trioxide was supported on an inorganic carrier, silica, and the total amount of Cr metal supported on the inorganic carrier was determined to be 2.7 wt% of the total weight of the catalyst, to obtain a catalyst.
The conditions of the catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 90 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage of the nitrogen is 39 percent, and the mole percentage of the ethylene in the reactor is 44 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.05, and the molar ratio of hydrogen to ethylene in the reactor was 0.17; the oxygen concentration in the reactor was 50ppb, and the polymerized monomer alpha-olefin was 1-butene and 1-pentene.
The prepared polyethylene had a density of 0.9397g/cm3The melt flow rate of the 21.6kg weight was 29.0g/10min, and the melt flow rate of the 5.0kg weight was 1.8g/10min, with a ratio in the range of 16.1.
Comparative example 2
Chromium chloride is loaded on the alumina serving as the inorganic carrier, and the total loading amount of Cr metal on the inorganic carrier is determined to be 2.1 wt% of the total weight of the catalyst.
The conditions of the catalyst for preparing polyethylene in a gas-phase fluidized bed are as follows: the reaction temperature in the reactor is 100 ℃, and the sum of the mole percentage of water and oxygen in the reactor is less than 1 ppm; based on the total mole number of the gas in the reactor as 100 percent, the mole percentage of the nitrogen is 30 percent, and the mole percentage of the ethylene in the reactor is 55 percent; the molar ratio of alpha-olefin to ethylene in the reactor was 0.03 and the molar ratio of hydrogen to ethylene in the reactor was 0.18; the oxygen concentration in the reactor was 80ppb, and the polymerized monomer alpha-olefin was 1-butene and 1-hexene.
The prepared polyethylene had a density of 0.9413g/cm3The melt flow rate of the 21.6kg weight was 23.0g/10min, and the melt flow rate of the 5.0kg weight was 1.1g/10min, with the ratio ranging from 20.9.
It can be seen from the above examples and comparative examples that the density of the polyethylene product prepared by the catalyst developed by the present invention is lower under the same loading of the active center, which indicates that the content of the polymerization monomer is higher and the copolymerization performance of the catalyst is good.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore intended that all such changes and modifications as fall within the true spirit and scope of the invention be considered as within the following claims.
Claims (18)
1. A process for preparing polyethylene features that the reactor used in said process is gas-phase fluidized bed, alpha-olefin is used as comonomer, the supported Cr-Mo composite catalyst is used,
the supported chromium-molybdenum composite catalyst comprises an active component and a porous inorganic carrier, wherein the active component comprises a chromium source and an organic molybdenum source, the chromium source comprises an organic chromium source and an inorganic chromium source, and the preparation method comprises the following steps:
(1) immersing the porous inorganic carrier into an aqueous solution of an inorganic chromium source for 1-12h at 25-100 ℃, drying at 100-300 ℃ for 5-20h, and then activating and roasting;
(2) immersing the product obtained in the step (1) into an organic solution containing an organic chromium source and an organic molybdenum source for 1-12h at the immersion temperature of 25-100 ℃, and then drying for 5-20h in a nitrogen atmosphere at the temperature of 100-300 ℃;
the total load of Cr and Mo in the active component is 0.01-20 wt% of the total weight of the catalyst; the molar ratio of Cr to Mo is 0.01: 0.99-0.99: 0.01; the molar ratio of Cr in the organic chromium source to Cr in the inorganic chromium source is 1: 9-9: 1;
wherein the inorganic chromium source is one or two of chromium trioxide, chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium chromate, ammonium dichromate and basic chromium acetate;
wherein the organic chromium source is one or two selected from bis-triphenylsilyl chromate, chromocene and organosilane chromate;
wherein the organic molybdenum source is one of molybdenum dialkyl dithiophosphate, molybdenum dialkyl dithiophosphate containing nitrogen, molybdenum dialkyl dithiocarbamate, molybdenum amine complex, molybdenum naphthenate and molybdenum alkyl salicylate.
2. The method for preparing polyethylene according to claim 1, wherein the molar ratio of Cr in the organic chromium source and the inorganic chromium source is 2:8 to 8: 2.
3. The method for preparing polyethylene according to claim 2, wherein the molar ratio of Cr in the organic chromium source and the inorganic chromium source is 3:6 to 6: 3.
4. The method for preparing polyethylene according to claim 1, wherein the molar ratio of Cr to Mo in the active component is 0.25: 0.75-0.75: 0.25.
5. The method for preparing polyethylene according to claim 4, wherein the molar ratio of Cr to Mo in the active component is 0.4: 0.6-0.6: 0.4.
6. The method for preparing polyethylene according to claim 1, wherein the total loading amount of Cr and Mo in the active components is 0.05-15 wt% of the total weight of the catalyst.
7. The method for preparing polyethylene according to claim 6, wherein the total loading of Cr and Mo in the active components is 0.1-10 wt% of the total weight of the catalyst.
8. The method for preparing polyethylene according to claim 1, wherein the porous inorganic support is obtained by modifying an inorganic support.
9. The method for preparing polyethylene according to claim 8, wherein the inorganic carrier is at least one selected from the group consisting of silica, alumina, titania, zirconia, magnesia, calcia, inorganic clay and montmorillonite.
10. The method for producing polyethylene according to claim 8, wherein the inorganic carrier has an average particle diameter of 1 to 100 μm and a pore volume of 0.5cm3/g～10.0cm3A surface area of 50 m/g2/g～1000m2/g。
11. The process for the preparation of polyethylene according to claim 8, characterized in that the modification is an aluminium modification: impregnating the inorganic support with a solution of an aluminium salt selected from Al (NO)3)3、AlC13And Al2(SO4)3One kind of (1).
12. The method for preparing polyethylene according to claim 8, wherein the modification is titanium modification, and the modification is carried out by a dipping method or a Cogel method.
13. The process for the preparation of polyethylene according to claim 8, characterized in that the modification is a fluorine modification: the inorganic support is co-impregnated with a fluorine-containing component.
14. The method for preparing polyethylene according to claim 1, wherein the reaction temperature in the reactor is 70 to 100 ℃.
15. The method of claim 1, wherein the sum of the mole percentages of water and oxygen in the reactor is less than 1 ppm.
16. The process for the preparation of polyethylene according to claim 1, characterized in that in the reactor: based on the total mole number of the gas in the reactor as 100%, the mole percentage content of nitrogen is 30-50%, and the mole percentage content of ethylene is 35-55%; the molar ratio of the alpha-olefin to the ethylene is 0.01-0.09: 1, and the molar ratio of the hydrogen to the ethylene is 0.1-0.2: 1.
17. The method for producing polyethylene according to claim 1, wherein the oxygen concentration in the reactor is 10 to 100 ppb.
18. The method for preparing polyethylene according to claim 1, wherein the α -olefin is any two or three of 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene.
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| CN103965387A (en) * | 2013-01-30 | 2014-08-06 | 中国石油天然气股份有限公司 | Polyethylene catalyst loaded with chromium and molybdenum oxides and preparation and application thereof |
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| CN103965387A (en) * | 2013-01-30 | 2014-08-06 | 中国石油天然气股份有限公司 | Polyethylene catalyst loaded with chromium and molybdenum oxides and preparation and application thereof |
Non-Patent Citations (2)
| Title |
|---|
| Development of a Hetero-Bimetallic Phillips-Type Catalyst for Ethylene Polymerization;Yanning Zeng et al.;《Macromolecular Reaction Engineering》;20131231;第7卷(第12期);第668-673页 * |
| 负载型铬钼复合聚乙烯催化剂的硅胶载体改性研究;刘丽芳;《中国优秀硕士学位论文全文数据库 工程科技Ⅰ辑》;20111215(第12期);B014-113 * |
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