CN106589178B - Vanadium and metallocene bimetallic catalyst and preparation method thereof - Google Patents
Vanadium and metallocene bimetallic catalyst and preparation method thereof Download PDFInfo
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- CN106589178B CN106589178B CN201510665759.6A CN201510665759A CN106589178B CN 106589178 B CN106589178 B CN 106589178B CN 201510665759 A CN201510665759 A CN 201510665759A CN 106589178 B CN106589178 B CN 106589178B
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Abstract
The invention relates to a vanadium and metallocene bimetallic catalyst and a preparation method thereof. The vanadium and metallocene bimetallic catalyst and the preparation method thereof compound the metallocene catalyst and the vanadium metal catalyst, so that the molecular weight of the high-density polyethylene produced by the catalyst is increased, the distribution is widened, the content and the distribution of the comonomer can be improved, and the catalyst has higher activity, thereby being a high-performance supported vanadium and metallocene bimetallic catalyst and the preparation method thereof, and the catalyst has better hydrogen regulation responsiveness by modifying titanium dioxide.
Description
Technical Field
The invention relates to a catalyst, in particular to a vanadium and metallocene bimetallic catalyst and a preparation method thereof.
Background
Polyethylene (PE) resin is a thermoplastic obtained by polymerizing ethylene monomer, and is one of the most popular plastic products in the world with the largest output and consumption, and mainly includes Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), High Density Polyethylene (HDPE) and some polyethylenes with special properties. Polyethylene has excellent mechanical properties, electrical insulation, chemical resistance, low temperature resistance and excellent processability. Polyethylene products are widely applied to various fields of industry, agriculture, automobiles, communication, daily life and the like. The polyethylene catalysts known at present are mainly Ziegler-Natta catalysts, chromium-based catalysts and metallocene catalysts, as well as other non-metallocene catalysts.
EP339571 discloses a process for the production of polyethylene having a broad molecular weight distribution by using a catalyst system consisting of: a catalyst component (A) comprising a silica support having deposited thereon a titanium or chromium compound; a catalyst component (B) comprising a transition metal compound; and catalyst component (c), an aluminoxane, such as MAO.
Patent application No. 201210118427.2 reports a novel supported chromium/vanadium metal oxide dual-activity center ethylene polymerization catalyst, which is represented by a third generation Phillips catalyst with a chromium/vanadium dual-activity center, and is characterized in that a supported vanadium active component is introduced on the Phillips chromium catalyst to form a chromium-based polyethylene catalyst with two activity centers of chromium and vanadium.
Disclosure of Invention
The invention aims to provide a vanadium and metallocene bimetallic catalyst and a preparation method thereof, wherein the metallocene catalyst and the vanadium metal catalyst are compounded to increase the molecular weight and widen the distribution of the high-density polyethylene produced by the catalyst, the content and the distribution of the comonomer can be improved, and the catalyst has higher activity, so that the catalyst is a high-performance supported vanadium and metallocene bimetallic catalyst and a preparation method thereof, and the catalyst has better hydrogen regulation responsiveness by modifying titanium dioxide.
The invention relates to a vanadium/metallocene bimetallic catalyst, which comprises an inorganic carrier and a loaded active component, wherein the inorganic carrier is an inorganic oxide, and the active component is a vanadium oxide and metallocene composition.
The vanadium oxide is vanadium oxide with a low oxidation state; the inorganic carrier is porous granular inorganic oxide, and the specific surface area of the inorganic carrier is 50-500 m2A concentration of 100 to 300m is preferred2The pore volume of the inorganic carrier is 0.1-5.0 cm3A/g, preferably 0.5 to 3.0cm3(ii)/g; the metallocene is one or more of zirconocene metal, hafnocene metal or titanocene metal; the precursor of the vanadium oxide is vanadium-containing salt which can be dissolved in water or organic solvent, and the vanadium oxideThe precursor is one or more of ammonium hexafluorovanadate, vanadium nitrate, vanadyl oxalate, ammonium metavanadate, vanadyl sulfate hydrate, vanadium sulfate, vanadium oxytrichloride, sodium vanadate, sodium metavanadate, vanadium bisacetylacetonate oxide, vanadium triisopropoxide, vanadium trialkoxide, vanadium acetylacetonate, vanadium triethoxy oxide, vanadyl chloride or trivanadium silicide, and the precursor of the vanadium oxide is more preferably ammonium metavanadate. In the precursor of the vanadium oxide, the supported amount of vanadium is 0.01-10 wt%, preferably 0.05-5 wt% of the total weight of the catalyst, based on the weight of vanadium.
The preparation method of the vanadium/metallocene bimetallic catalyst comprises the following steps:
(1) combining a vanadium oxide precursor to an inorganic support to obtain a catalyst precursor;
(2) roasting the obtained catalyst precursor at high temperature under an oxidation condition to obtain vanadium oxide in an oxidation state;
(3) reacting the sample under a reducing condition to obtain pre-reduced vanadium oxide with a low oxidation state;
(4) the final supported vanadium and metallocene bimetallic catalyst is obtained by contacting the pre-reduced vanadium oxide with the metallocene composition or the catalyst after the metallocene composition is loaded on the inorganic carrier, and the preparation method thereof.
The inorganic carrier in step (1) is any oxide of a metal of groups IIA, IIIB, IVB, IB, IIB, IIIA and IVA.
The inorganic carrier is silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, silica gel or inorganic clay. Preferred are silica gels, especially amorphous porous silica gels, more preferably Davison 955 silica gel, produced by Grace corporation.
The catalyst is further optimized by modifying an inorganic carrier, such as titanium dioxide titanium modification and the like, so that better hydrogen response and copolymerization performance are obtained.
The inorganic carrier is a titanium dioxide modified inorganic carrier; the titanium compound raw material for preparing the titanium dioxide modified inorganic carrier is one or more of acetylacetone titanium oxide, titanium trichloride, titanium tetrachloride, titanium tert-butoxide, tetra-n-butyl titanate, titanyl sulfate, titanium sulfate, ammonium hexafluorotitanate, isopropyl titanate or tetraethyl titanate.
The high-temperature roasting in the step (2) is divided into a low-temperature stage and a high-temperature stage, wherein the low-temperature stage is carried out at 100-300 ℃, and the high-temperature stage is carried out at 300-900 ℃; the low-temperature stage lasts for 1-10 hours, and the high-temperature stage lasts for 1-10 hours. The duration of the low-temperature stage is preferably 2-8 hours. The duration time of the high-temperature stage is preferably 2-9 hours, and more preferably 3-8 hours. 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 stage is carried out in an inert gas or air atmosphere; the high-temperature stage roasting is carried out under the condition of air or oxygen. The low-temperature stage is carried out under an inert gas or air atmosphere, preferably under an inert gas such as nitrogen, helium, argon, and the like, preferably under a nitrogen atmosphere. According to one embodiment, 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. According to one embodiment, the atmosphere is changed, for example, from air to an inert gas such as nitrogen or the like, when cooling to a temperature of 300 to 400 ℃ after high-temperature firing. According to one embodiment, the cooling is free cooling. The obtained catalyst is stored under inert gas atmosphere for standby.
And after high-temperature roasting, cooling to the temperature of 300-400 ℃, and changing the atmosphere from air to inert gas.
The reducing agent in the step (3) is an organic aluminum compound, preferably one or more of trimethyl aluminum, triethyl aluminum, triisopropyl aluminum, triisobutyl aluminum, tri-n-hexyl aluminum, diethyl aluminum chloride, dibutyl aluminum bromide, ethoxy diethyl aluminum, methyl aluminoxane, ethyl aluminoxane and butyl aluminoxane; the use ratio of the reducing agent is controlled to be 1-100: 1, preferably 6-50: 1, and the reducing agent is added for reducing for 1 min-4 h, preferably 0.5-2 h.
The combination of the precursor of the vanadium oxide and the inorganic carrier is called a loading process, and the loading step is as follows: the solution of the precursor component containing vanadium oxide is impregnated on an inorganic support and dried. The solution of the precursor component of the vanadium oxide is prepared by dissolving the precursor of the vanadium oxide in water or an organic solvent, wherein the organic solvent can be any solvent capable of dissolving the precursor of the vanadium oxide, preferably ethanol.
The metallocene in step (4) is preferably a zirconocene, a metallocene compound having the following formula: cp2ZrR′R″。
Wherein Cp represents a cyclopentadienyl group selected from unsubstituted cyclopentadienyl groups; cyclopentadienyl substituted by a group of the group comprising unsubstituted and substituted straight, branched, cyclic or partially cyclic alkyl groups containing from 1 to 20 carbon atoms and fused ring groups; or an unsubstituted and substituted monocyclic or polycyclic aromatic group which may optionally contain heteroatoms; and aralkyl substituted cyclopentadienyl. The substituents on the cyclopentadienyl ring form a fused ring structure containing one or more fused heteroatom-containing benzene, naphthalene or cyclohexane rings. The R 'and R' substituents can be the same or different and include the group of alkyl groups having 1 to 6 carbon atoms, unsubstituted or substituted benzyl groups, and phenoxy groups substituted with alkyl groups having l to 6 carbon atoms. Preferred R 'and R' are in the group comprising methyl, benzyl or phenoxymethyl and combinations thereof. R 'or R' are either halogen, preferably chlorine.
Contacting the catalyst obtained in the step (3) with a metallocene compound or a supported metallocene catalyst, preferably in a dry powder form; and II, carrying out contact under the condition of a solvent, and drying under the inert condition to remove the solvent to obtain the catalyst with better fluidity.
The finally prepared vanadium and metallocene bimetallic catalyst and the preparation method thereof contain two metal active centers vanadium and metallocene, the influence of the low vanadium active center ratio on the resin is not obvious, and the relative molecular mass of the final resin is too high due to the over-high vanadium ratio, so that the processing performance is reduced. The preferred molar ratio of vanadium element to metallocene is from 0.05:1 to 20:1, more preferably from 0.5:1 to 5: 1.
According to the vanadium and metallocene bimetallic catalyst and the preparation method thereof, the titanium loading is 0.1-10 wt%, preferably 0.2-8 wt% of the total weight of the catalyst, based on the weight of Ti.
The olefin polymerization with the catalyst is carried out in reactors of the type commonly used, including batch or continuous reactors, either in slurry or gas phase.
The present invention preferably employs a gas phase polymerizer.
The catalyst has two active centers of vanadium and metallocene, and is used in synthesizing ethylene homopolymer and ethylene- α -olefin copolymer.
A process for the polymerization of ethylene, especially for the preparation of polymers of ethylene having a bimodal or broad distribution. The catalyst composition contains vanadium compound component and metallocene component, which are combined into bimetallic active center catalyst in different modes.
The polyethylene homopolymer and the polyethylene copolymer prepared by the catalyst have MFR (21.6kg) within the range of 0.01-120 g/10min and relative molecular mass distribution of 1-10.
The preparation steps of the catalyst preferably adopt the following steps:
(1) davison 955 silica gel is used as an inorganic carrier, a prepared precursor of vanadium oxide is added into untreated Davison 955 silica gel, the solution is slowly stirred at the temperature of 50-60 ℃ to be uniformly dispersed in the whole system, standing impregnation is carried out for 4-6 hours, active components are fully introduced into micropores of the silica gel, and an impregnated load is dried at the temperature of 120 ℃ to remove physical water in the load, so that dry solid powder with good fluidity is obtained.
(2) And (3) carrying out high-temperature activation at 900 ℃ at 100 ℃ in the presence of air on the dried solid powder to oxidize the vanadium metal into a high-valence state.
(3) Then reducing by adopting alkyl aluminum in an inert environment, and finally removing the solvent by heating and drying to obtain the pre-reduced catalyst of the low oxidation state vanadium oxide with good fluidity.
Davison 955 silica gel is activated at high temperature to remove physical water and partial chemical water from the carrier, and then MAO (methyl aluminoxane) is added to treat the catalyst carrier, and after washing the treated carrier, a metallocene compound (e.g., Cp) is supported2ZrCl2) Then washing to remove the non-loaded metallocene compound, and drying to obtain the supported metallocene catalyst, i.e. the catalyst obtained by loading the metallocene composition on an inorganic carrier.
(4) Under an inert environment, the catalyst finished product is contacted with a supported metallocene catalyst to be mixed or is mixed under the condition of a solvent to prepare vanadium compound/metallocene double-center catalyst slurry, and then the slurry is dried to obtain catalyst dry powder.
The preparation steps of the catalyst preferably adopt the following steps:
(1) davison 955 silica gel is used as an inorganic carrier, a prepared precursor of vanadium oxide is added into untreated Davison 955 silica gel, the solution is slowly stirred at the temperature of 50-60 ℃ to be uniformly dispersed in the whole system, standing impregnation is carried out for 4-6 hours, active components are fully introduced into micropores of the silica gel, and an impregnated load is dried at the temperature of 120 ℃ to remove physical water in the load, so that dry solid powder with good fluidity is obtained.
(2) And (3) carrying out high-temperature activation at 900 ℃ at 100 ℃ in the presence of air on the dried solid powder to oxidize the vanadium metal into a high-valence state.
(3) Then reducing by adopting alkyl aluminum in an inert environment, and finally removing the solvent by heating and drying to obtain the pre-reduced catalyst of the low oxidation state vanadium oxide with good fluidity.
(4) Preparing the pre-reduced catalyst of the low oxidation state vanadium oxide into a slurry state in normal hexane or industrial white oil, dripping a solution of the metallocene catalyst into the catalyst under an inert environment, and stirring to prepare the vanadium compound/metallocene double-center catalyst.
The preparation method of the titanium dioxide modified inorganic carrier comprises the following steps:
i) uniformly mixing a titanium compound and an organic solvent, stirring, adding acid for reflux reaction, adding an inorganic carrier for reaction, and drying a product after the reaction;
ii) roasting the obtained product at the high temperature of 300-900 ℃ to obtain the titanium dioxide modified inorganic carrier.
The gas phase polymerization reaction of the catalyst of the present invention is adopted to prepare the polymer, and the steps are as follows:
firstly, a polymerization kettle is treated under the high-temperature and vacuum state, high-purity nitrogen is supplemented for standby, a dry powder catalyst is added into the polymerization kettle under the protection of the high-purity nitrogen after being metered, the polymerization kettle is vacuumized and stirred, hot water is introduced into a jacket to raise the temperature of the polymerization kettle to a specified temperature, ethylene gas is slowly added to the reaction pressure, and polymerization reaction is started. 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 addition of the comonomer and hydrogen is carried out through independent pipelines or after the gas distribution of a gas distribution tank. After the polymerization is started, the reaction is carried out at constant temperature and pressure.
The gas phase polymerization reaction of the catalyst of the present invention is adopted to prepare the polymer, and the steps are as follows:
firstly, vacuumizing a polymerization kettle, replacing the polymerization kettle with high-purity nitrogen for many times, and then adding a solvent in a vacuum state. Adding alkyl aluminum under the protection of high-purity nitrogen, and stirring. Adding comonomer and hydrogen into the catalyst powder added under the protection of nitrogen, heating to a specified temperature, introducing ethylene to a set polymerization pressure, and starting a polymerization reaction. 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. After the polymerization is started, the reaction is carried out at constant temperature and pressure.
The preparation method is not limited to the above two.
The test method and conditions for the characteristic properties of the polymers obtained are as follows:
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 is measured at 160 ℃. And processing data by adopting a universal correction method with narrow-distribution polystyrene as a standard sample.
2) Melt Mass Flow Rate (MFR)
The melt flow rate instrument from CEAST 6942/000, Italy, was used in accordance with GB/T3682-.
Compared with the prior art, the invention has the following beneficial effects:
the vanadium and metallocene bimetallic catalyst and the preparation method thereof compound the metallocene catalyst and the vanadium metal catalyst, so that the molecular weight of the high-density polyethylene produced by the catalyst is increased, the distribution is widened, the content and the distribution of the comonomer can be improved, and the catalyst has higher activity, thereby being a high-performance supported vanadium and metallocene bimetallic catalyst and the preparation method thereof, and the catalyst has better hydrogen regulation responsiveness by modifying titanium dioxide.
Detailed Description
The present invention will be further described with reference to the following examples.
The method is a conventional method unless otherwise specified. The materials are commercially available unless otherwise specified.
Examples 1 to 1
Selecting commercially available Davison 955 silica gel as the inorganic carrier; 0.11g of ammonium metavanadate is dissolved in 36ml of distilled water at 60 ℃ (the vanadium loading is 0.30 wt%), then 20g of silica gel is soaked in the ammonium metavanadate solution, and the solution is soaked for 1h at 60 ℃ to ensure that the active components are uniformly adsorbed in the micropores of the silica gel, and the whole process belongs to a physical adsorption process. Drying at 120 deg.C for 20 hr, transferring to fluidized bed, roasting at 200 deg.C in nitrogen for 1 hr, maintaining at 600 deg.C in high-purity air for 4 hr, and naturally cooling in nitrogen. N-hexane is used as a solvent, diethyl aluminum ethoxide is added for reduction, the molar ratio of Al to V is 12: 1, and the reduction is carried out for 30 min. And then heating to 70 ℃ and drying for 4h to obtain the pre-reduced catalyst containing the low oxidation state vanadium oxide with better fluidity for later use.
Selecting Davison 955 silica gel as an inorganic carrier; 20ml of toluene are added, stirred homogeneously, 5ml of MAO are added and then Cp is added2ZrCl2Toluene solution with Al/Zr molar ratio of 120: 1, stirring for 4h, washing and drying to obtain the metallocene catalyst.
The vanadium compound catalyst and the metallocene catalyst are mixed in a dry powder manner according to the V/Zr molar ratio of 1:1 to prepare the catalyst.
Gas phase polymerization test was conducted in two ways
The first method comprises the following steps: the three catalysts were weighed for gas phase polymerization test.
Firstly, heating, vacuumizing and treating with high-purity nitrogen for 4 hours in a 1L gas-phase polymerization kettle, weighing 0.1g 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 0.8Mpa, starting the polymerization reaction, and keeping the pressure and the temperature in the polymerization kettle constant. The reaction time was 1 h. Cooling and discharging after the polymerization reaction is finished, weighing, calculating the activity, and testing the performance of the polyethylene resin.
And the second method comprises the following steps: the hydrogen telomerization test was carried out in the gas phase polymerization using the first catalyst. Hydrogen was added at 0.004MPa during the gas phase polymerization.
Examples 1 to 2
This example is the same as example 1 except that the vanadium compound catalyst and the metallocene catalyst were dry-powder mixed at a V/Zr molar ratio of 2:1 to obtain a catalyst.
Examples 1 to 3
This example is the same as example 1 except that the vanadium compound catalyst and the metallocene catalyst were dry-powder mixed at a V/Zr molar ratio of 3:1 to obtain a catalyst.
Examples 1 to 4
This example is the same as example 1 except that the vanadium compound catalyst and the metallocene catalyst were dry-powder mixed at a V/Zr molar ratio of 4:1 to obtain a catalyst.
Example 2
The vanadium catalyst was prepared according to the procedure for the preparation of the vanadium catalyst in example 1, except that the Al/V molar ratio was 16: 1.
The pre-reduced catalyst containing vanadium oxide in a low oxidation state was mixed with the metallocene catalyst of example 1 in a dry powder ratio of 1:1 to prepare a catalyst for use.
An ethylene polymerization test was conducted in the gas phase polymerization manner of example 1.
Example 3
The vanadium catalyst was prepared according to the procedure for the preparation of the vanadium catalyst in example 1, except that the Al/V molar ratio was 20: 1.
The pre-reduced catalyst containing vanadium oxide in a low oxidation state was mixed with the metallocene catalyst of example 1 in a dry powder ratio of 1:1 to prepare a catalyst for use.
An ethylene polymerization test was conducted in the gas phase polymerization manner of example 1.
Example 4
The preparation was carried out according to the vanadium catalyst preparation method of example 1, except that ammonium hexafluorovanadate solution was used as the vanadium source.
The pre-reduced catalyst containing vanadium oxide in a low oxidation state was mixed with the metallocene catalyst of example 1 in a dry powder ratio of 1:1 to prepare a catalyst for use.
An ethylene polymerization test was conducted in the gas phase polymerization manner of example 1.
Example 5
The preparation was carried out according to the vanadium catalyst preparation method of example 1, except that vanadyl oxalate solution was used as the vanadium source.
The pre-reduced catalyst containing vanadium oxide in a low oxidation state was mixed with the metallocene catalyst of example 1 in a dry powder ratio of 1:1 to prepare a catalyst for use.
An ethylene polymerization test was conducted in the gas phase polymerization manner of example 1.
Example 6
The preparation was carried out according to the vanadium catalyst preparation method of example 1, except thatWith Cp2ZrMe2Toluene solution as metallocene active center.
The catalyst was prepared by dry powder mixing the pre-reduced catalyst containing vanadium oxide in a low oxidation state with the vanadium catalyst of example 1 in a ratio of 1: 1.
An ethylene polymerization test was conducted in the gas phase polymerization manner of example 1.
Example 7
The vanadium catalyst formulation of example 1 was followed except that Cp was used2ZrBz2Toluene solution as metallocene active center.
The catalyst was prepared by dry powder mixing the pre-reduced catalyst containing vanadium oxide in a low oxidation state with the vanadium catalyst of example 1 in a ratio of 1: 1.
An ethylene polymerization test was conducted in the gas phase polymerization manner of example 1.
Example 8
The pre-reduced catalyst containing vanadium oxide in low oxidation state of example 1 was suspended in technical white oil to produce a 10% by weight slurry catalyst, the molar ratio of which to the metallocene catalyst of example 1 was 1:1 (example 8-1), 2:1 (example 8-2), 3:1 (example 8-3) the vanadium compound/metallocene double-site catalyst was prepared by adding dropwise a toluene solution of the metallocene catalyst and mixing the solution uniformly.
Polymerization test was carried out in two ways
The first method comprises the following steps: the three catalysts were measured separately for slurry polymerization tests. Firstly, vacuumizing a 2L polymerization kettle, replacing 3 times with high-purity nitrogen, and then adding metered solvent in a vacuum state. Adding 5ml of aluminum alkyl under the protection of high-purity nitrogen, and stirring for a certain time. Under the protection of nitrogen, 2ml of catalyst slurry was added, 10ml of comonomer 1-hexene was added, the temperature was raised to 75 ℃, ethylene was introduced to the set polymerization pressure of 0.8Mpa, and the polymerization was started. 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. After the polymerization was started, the reaction was carried out at constant temperature and pressure for 1 hour. Cooling and discharging after the polymerization reaction is finished, weighing, calculating the activity, and testing the performance of the polyethylene resin.
And the second method comprises the following steps: a hydrogen telomerization test was conducted in the first gas phase polymerization except that 0.004MPa of hydrogen was added during the gas phase polymerization.
Example 9
Soaking an inorganic carrier Davison 955 silica gel in a normal hexane solution of tetra-n-butyl titanate (titanium load is 2 wt%), continuously stirring for 4h, performing oil bath at 80 ℃ for drying for 4h, then performing vacuum drying for 2h to further remove a solvent in a silica gel carrier pore channel, and transferring the silica gel carrier to a forced air drying oven for drying for 8h at 80 ℃; and then roasting and activating the dried sample in a fluidized bed, keeping the temperature of 500 ℃ for 6h under high-purity air, and finally naturally cooling the silica gel under nitrogen to obtain the titanium dioxide modified silica gel prepared by the impregnation method.
0.11g of ammonium metavanadate is dissolved in 36ml of distilled water at 60 ℃ (the vanadium loading is 0.30 wt%), then 20g of silica gel is soaked in the ammonium metavanadate solution, and the solution is soaked for 1h at 60 ℃ to ensure that the active components are uniformly adsorbed in the micropores of the titanium dioxide silica gel, and the whole process belongs to a physical adsorption process. Drying at 120 deg.C for 20 hr, transferring to fluidized bed, roasting at 100 deg.C in nitrogen for 3 hr, maintaining at 600 deg.C in high-purity air for 4 hr, and naturally cooling in nitrogen. N-hexane is used as a solvent, diethyl aluminum ethoxide is added for reduction, the molar ratio of Al to V is 12: 1, and the reduction is carried out for 30 min. And then heating to 70 ℃ and drying for 4h to obtain the vanadium compound catalyst with better fluidity for later use.
Selecting Davison 955 silica gel as an inorganic carrier; 20ml of toluene are added, stirred homogeneously, 5ml of MAO are added and then Cp is added2ZrCl2Toluene solution with Al/Zr molar ratio of 120: 1, stirring for 4h, washing and drying to obtain the metallocene catalyst.
The catalyst is prepared by dry powder mixing of the catalyst according to the V/Zr molar ratio of 1: 1.
The three catalysts were weighed for gas phase polymerization test. Firstly, heating, vacuumizing and treating with high-purity nitrogen for 4 hours in a 1L gas-phase polymerization kettle, weighing about 0.1g of the prepared catalyst, adding the catalyst into the polymerization kettle under the protection of the high-purity nitrogen, raising the temperature of the polymerization kettle to 92 ℃, slowly adding an ethylene monomer to the reaction pressure of 0.8Mpa, starting the polymerization reaction, and keeping the pressure and the temperature in the polymerization kettle constant. The reaction time was 1 h. Cooling and discharging after the polymerization reaction is finished, weighing, calculating the activity, and testing the performance of the polyethylene resin.
Comparative example 1
The pre-reduced vanadium oxide-containing catalyst of example 1 was selected for polymerization testing in the gas phase polymerization mode of example 1.
Comparative example 2
The metallocene catalyst in example 1 was selected to conduct polymerization test in the gas phase polymerization manner of example 1.
Table 1 shows the results of GPC measurements of the catalytic activity and the polymerization product obtained by gas phase polymerization of catalysts of examples 1-1 to examples 1-4 in different compounding ratios. The results show that the larger the vanadium/zirconium ratio, the higher the weight average relative molecular mass and the broader the distribution index. However, when the vanadium ratio is increased to a certain extent, the activity is reduced.
TABLE 1 polymerization of catalysts of examples 1-1 to examples 1-4 with different compounding ratios and GPC results of the products
Table 2 shows the results of gas phase polymerization of the catalysts of examples 2 to 3 under different Al/V conditions. The results show that the larger the Al/V ratio, the lower the activity, the higher the weight average relative molecular mass, and the broader the distribution index.
TABLE 2 examples 2-3 polymerization of catalysts with different Al/V ratios and GPC results for the products
Table 3 shows the results of the properties of the gas-phase polymerization products of the catalysts of examples 4 to 5 under different vanadium source conditions.
Table 3 examples 4-5 properties of gas-phase polymerization products of different vanadium-derived catalysts
Table 4 shows the results of the properties of the gas-phase polymerization products of the catalysts of examples 6 to 7 under different metallocene catalyst conditions.
Table 4 examples 6-7 properties of gas-phase polymerization products of different metallocene catalysts
Table 5 shows the results of GPC measurements of the catalytic activities and polymerization products obtained by slurry polymerization using catalysts of examples 8-1 to 8-3 in different compounding ratios.
TABLE 5 catalyst slurry polymerization and product test results for different compounding ratios of examples 8-1 to 8-3
Table 6 shows the results of the polymerization of the different types of catalysts and the performance tests of the products in comparative example 1, comparative example 2 and examples 1 to 3. The polymerization activity of the composite catalyst is higher than that of single metal, and the relative molecular mass distribution is widest.
TABLE 6 results of tests on polymerization and product properties of different types of catalysts in comparative examples 1 and 2 and examples 1 to 3
Table 7 shows the results of the second polymerization test in examples 9 and 8 and the second polymerization test in examples 1 to 1, which are the hydrogen control data of the titanium-modified catalyst homopolymerization and hydrogen control tests and the unmodified catalyst.
TABLE 7 test results of the second polymerization test of example 9, example 8 and the second polymerization test of example 1-1
As can be seen from the data in Table 7, the molecular weight of the titanium modified catalyst is reduced, the molecular distribution becomes narrow after hydrogen is added, and the titanium modified catalyst has narrower distribution and lower molecular weight than the unmodified catalyst under the same hydrogen adding condition, which indicates that the titanium modified catalyst is more sensitive to hydrogen.
Claims (6)
1. A preparation method of a vanadium and metallocene bimetallic catalyst comprises an inorganic carrier and a loaded active component, wherein the inorganic carrier is an inorganic oxide, and the active component is a vanadium oxide and metallocene composition; the method is characterized by comprising the following steps:
(1) combining a vanadium oxide precursor to an inorganic support to obtain a catalyst precursor;
(2) roasting the obtained catalyst precursor at high temperature under an oxidation condition to obtain vanadium oxide in an oxidation state;
(3) reacting the sample under a reducing condition to obtain pre-reduced vanadium oxide with a low oxidation state;
(4) contacting the pre-reduced vanadium oxide with a metallocene composition or a catalyst obtained by loading the metallocene composition on an inorganic carrier to obtain a final supported vanadium/metallocene composite polyethylene catalyst;
the inorganic carrier is a titanium dioxide modified inorganic carrier; the titanium compound raw material for preparing the titanium dioxide modified inorganic carrier is one or more of acetylacetonato titanium oxide, titanium trichloride, titanium tetrachloride, tert-butyl titanium, tetra-n-butyl titanate, titanyl sulfate, titanium sulfate, ammonium hexafluorotitanate, isopropyl titanate or tetraethyl titanate;
the high-temperature roasting in the step (2) is divided into a low-temperature stage and a high-temperature stage, wherein the low-temperature stage is carried out at 100-300 ℃, and the high-temperature stage is carried out at 300-900 ℃; the low-temperature stage lasts for 1-10 hours, and the high-temperature stage lasts for 1-10 hours;
the reducing agent in the step (3) is one or more of trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diethylaluminum chloride, dibutylaluminum bromide, ethoxydiethylaluminum, methylaluminoxane, ethylaluminoxane and butylaluminoxane; the using ratio of the reducing agent is controlled to be 12-20: 1 of Al/V molar ratio, and the reducing time is 1 min-4 h after the reducing agent is added.
2. The method of claim 1, wherein the vanadium oxide is a low oxidation state vanadium oxide; the inorganic carrier is porous granular inorganic oxide, and the specific surface area of the inorganic carrier is 50-500 m2The pore volume of the inorganic carrier is 0.1-5.0 cm3(ii)/g; the metallocene is one or more of zirconocene metal, hafnocene metal or titanocene metal; the vanadium oxide precursor is one or more of ammonium hexafluorovanadate, vanadium nitrate, vanadyl oxalate, ammonium metavanadate, vanadyl sulfate hydrate, vanadium sulfate, vanadium oxytrichloride, sodium vanadate, sodium metavanadate, vanadium oxide bisacetylacetonate, vanadium oxide tripropanol, vanadium acetylacetonate, triethoxy vanadium oxide, vanadyl chloride or trivanadium silicide; in the precursor of the vanadium oxide, the vanadium loading amount is 0.01-10 wt% of the total weight of the catalyst, based on the weight of vanadium.
3. The method of claim 1, wherein the inorganic support in step (1) is any oxide of a group IIA, IIIB, IVB, IB, IIB, IIIA or IVA metal.
4. The method for preparing a vanadium and metallocene bimetallic catalyst according to claim 1 or 3, characterized in that the inorganic carrier is silica, alumina, titania, zirconia, magnesia, calcia, silica gel or inorganic clay.
5. The method for preparing a vanadium and metallocene bimetallic catalyst according to claim 1, characterized in that the low temperature stage is carried out under an inert gas or air atmosphere; the high-temperature stage roasting is carried out under the condition of air or oxygen.
6. The method for preparing a vanadium and metallocene bimetallic catalyst according to claim 1, wherein the atmosphere is changed from air to inert gas when the catalyst is cooled to a temperature of 300 to 400 ℃ after the high-temperature calcination.
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| CN102627710A (en) * | 2012-04-16 | 2012-08-08 | 华东理工大学 | Preparation method and application of novel supported double-center composite polyethylene catalyst |
| CN106554440A (en) * | 2015-09-30 | 2017-04-05 | 中国石油化工股份有限公司 | For preparing the catalyst of polyvinyl resin and its polyvinyl resin of preparation |
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| CN102627710A (en) * | 2012-04-16 | 2012-08-08 | 华东理工大学 | Preparation method and application of novel supported double-center composite polyethylene catalyst |
| CN106554440A (en) * | 2015-09-30 | 2017-04-05 | 中国石油化工股份有限公司 | For preparing the catalyst of polyvinyl resin and its polyvinyl resin of preparation |
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