CN111072798A - Silica gel and preparation method and application thereof - Google Patents
Silica gel and preparation method and application thereof Download PDFInfo
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- CN111072798A CN111072798A CN201811231807.0A CN201811231807A CN111072798A CN 111072798 A CN111072798 A CN 111072798A CN 201811231807 A CN201811231807 A CN 201811231807A CN 111072798 A CN111072798 A CN 111072798A
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Abstract
A silica gel and its preparing process and application features that the silica gel is activated, and the activating process includes two steps of heating and cooling, in which glycol is introduced to the cooling section. The invention can reduce the stress concentration generated in the cooling process, and the obtained silica gel carrier can better keep the original characteristics (aperture, pore volume, specific surface area and the like) and enrich the surface layer of the silica gel with hydroxyl; not only the thermal activation of the silica gel is completed, but also the chemical treatment of the carrier is completed.
Description
Technical Field
The invention belongs to the technical field of macromolecules, and relates to a silica gel carrier, a preparation method and application thereof, in particular to a silica gel carrier of a metallocene catalyst, a preparation method thereof and application of the silica gel carrier as a carrier of the metallocene catalyst.
Background
The metallocene catalyst is a 3 rd generation olefin polymerization catalyst followed by a Ziegler catalyst, a Ziegler-Natta catalyst. The metallocene catalyst is an organometallic complex catalyst formed by cyclopentadienyl and derivatives thereof and transition metal. Homogeneous metallocene catalysts have many advantages, but problems arise when polyolefin products are produced using existing plants, such as: the particle morphology of the polymer is not good and is difficult to control; large amount of Methylaluminoxane (MAO), high cost, easy kettle adhesion, difficult subsequent treatment and granulation process are required, thereby limiting further application in industry.
The method of use which is common at present is to support metallocene catalysts. Among the many supports, the most commonly used support is SiO2Or SiO physically and chemically modified2Most researchers believe that silica gel relies primarily on free hydroxyl groups on its surface for metallocene catalyst support. Silica gel generally cannot be directly used as a carrier of metallocene catalysts, and free water, a even hydroxyl group, a double hydroxyl group and a free hydroxyl group on the surface of the silica gel are all poisons of catalyst ligands. Therefore, it is common practice that silica gel needs to be thermally activated as well as chemically activated before use.
The common methods for thermal activation of silica gel are: heating the silica gel in an inert atmosphere according to a program temperature control mode, gradually heating to a specified temperature (such as 400-. At present, the influence of technological conditions such as the temperature rise process, the thermal activation time, the final activation temperature and the like of a silica gel carrier on carrier particles in the industry is researched more and is mature. However, the research on the control and influence of the thermal activation and temperature reduction process of the silica gel is few, and basically, the silica gel is cooled naturally or is heated in a closed mode and then continuously cooled under the action of inert atmosphere, and almost no attention is paid to the influence of the silica gel on the silica gel carrier particles.
When the silica gel support is chemically activated, it may be treated with another compound and then treated with MAO, or treated with MAO and then another compound, and then loaded with the metallocene catalyst. At present, the chemical activation method of silica gel is basically to add solvent, silica gel, chemical treatment agent, MAO and other components into the reactor in one step or in multiple steps, and the process is generally carried out in a liquid phase environment.
CN103204509 discloses a food additive silica gel and its production process, comprising: preparing raw materials, reacting to prepare glue, aging to remove iron and enhance activity, washing, instantly drying, crushing and grading granularity. The median value of the obtained silica gel particle size is reasonably controlled, the specific surface area and the pore volume are larger, the effective particle size distribution in the silica gel is concentrated, and the content of particles smaller than 10 mu m is low. The heat activation process of the silica gel carrier for the polyolefin catalyst researches the influence of the temperature rise rate, the silica gel particle size, the silica gel type and the like on the physical adsorption water and the surface hydroxyl removal amount in the heat activation process of the silica gel carrier, and tests show that the silica gel adsorption water can be basically removed at 200 ℃; as the activation treatment temperature increases, decreasing the rate of temperature increase increases the degree of hydroxyl group removal. Before the catalyst is prepared, the silica gel is pretreated by using the combined action of MAO and ethylene glycol (glycerol and bisphenol A), so that the polymerization performance of the obtained metallocene catalyst is improved, the loading capacity of zirconium is improved, and the bulk density of resin is improved. "silica gel supported metallocene catalyst research progress" mentions that polyhydroxy radicals can be used for chemical treatment of silica gel due to the presence of multiple electron deficient centers Al of MAO molecules3+It can act with polyhydroxy containing multiple polar groups to increase the specific surface area of the carrier, thereby increasing the loading of the catalyst. CN101554595B discloses a catalyst carrier for olefin polymerizationThe catalyst is a Ziegler-Natta catalyst, the shape of the carrier of the catalyst is spherical, and the carrier of the catalyst is divided into three layers from inside to outside, wherein the inner layer is made of inert inorganic material, the middle layer is a complex compound of polyalcohol and magnesium halide deposited on the inert inorganic material, and the outer layer is organic polymer containing polar functional groups loaded on the complex compound. When the obtained Ziegler-Natta catalyst is applied to the polymerization of ethylene or propylene, the melt flow ratio of the obtained polymerization product is obviously improved, the processing performance of the polymerization product is improved, and the Ziegler-Natta catalyst has the characteristic of high activity. The prior art does not relate to the procedure cooling control of silica gel thermal activation, the influence of the cooling process on the characteristics of silica collagen, and the treatment with glycol. In the prior art, when silica gel is chemically treated, the treatment is generally carried out under a liquid phase condition, and the treatment is carried out on a silica gel carrier by using polyalcohol and MAO together, so that the influence of singly treating the silica gel by using the polyalcohol is avoided; the above techniques also do not involve the influence of the addition of ethylene glycol on the characteristics of the carrier silica gel during the temperature reduction stage of thermal activation.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a silica gel carrier, which has good particle characteristics and enriches hydroxyl on the surface layer of silica gel; the invention also provides a preparation method of the carrier.
When the silica gel carrier is subjected to thermal activation, the inventor controls a cooling process by a sectional program, and introduces ethylene glycol to the silica gel surface layer in the cooling section of the thermal activation, so that the silica gel carrier with enriched hydroxyl groups on the surface layer and good particle shape and characteristics is obtained, and the original characteristics (pore volume, specific surface area and the like) of the silica gel carrier are well maintained.
The invention also combines the thermal activation process and the chemical activation treatment of the silica gel, completes the ethylene glycol chemical treatment while performing the thermal activation, and completes the ethylene glycol chemical treatment between a gas phase and a solid phase.
The silica gel carrier has the following indexes that the specific surface area is 300-320m2The volume of pores is 1.55-1.75mL/g, the average pore diameter is 21-25nm, the particle diameter is 32-35 μm, and the content of glycol is 1-5 wt%.
The preparation method of the carrier is completed by thermal activation and mainly comprises two steps including a temperature rising section and a temperature reduction section.
The heating-up section process of the silica gel thermal activation is carried out according to the following steps:
(1) silica gel carrier is weighed and loaded into an activator, and the flow of fluidizing gas is adjusted to enable the silica gel carrier to be in a fluidizing state.
(2) The temperature of the activator is increased, and the temperature is increased from room temperature to the designated temperature within a certain period of time and is kept constant.
(3) Continuously heating to the maximum activation temperature T within a certain timeSAnd keeping the temperature constant.
The temperature reduction section of the silica gel thermal activation adopts program control temperature reduction, the introduction of ethylene glycol is also carried out in the temperature reduction section, and the method comprises the following steps:
(4) cooling with an activator by SJ1Time cooling TJ1Constant temperature SH1。
(5) The activator is continuously cooled through SJ2Time cooling TJ2Constant temperature SH2。
(6) Heating and gasifying a certain amount of ethylene glycol (the boiling point of the ethylene glycol is T)F) And enters the activator with the fluidizing gas, the temperature of the carrier being TCControlling the processing time to be SC。
(7) The activator is continuously cooled through SJ3Cooling to room temperature, discharging, sealing and storing.
Wherein:
the fluidizing gas is an inert gas, preferably high purity nitrogen, having a water content of less than 5 ppm.
The loading factor of the silica gel carrier is 0.4-0.8 of the volume of the activator.
In step (3), TSPreferably 400-.
S in step (4)J1Preferably 1.0-4.0 hours, SH1Preferably 0.5-2.0 hours, TJ1Preferably 100 ℃ and 250 ℃.
S in step (5)J2Preferably 0.5-2.0 hours, SH2Preferably 0.5-2.0 hours, TJ2Preferably 100-.
Ethylene glycol in step (6)The dosage of the active component is 1 to 5 percent of the mass of the silica gel carrier, and the processing time S isCPreferably 15-60 minutes. When the cooling program is set, the carrier temperature T is controlledCBelow TFTemperature difference between the two (T)F-TC) Preferably 10-30 ℃.
S in step (7)J3The time is 0.5-2 hours.
The carrier of the invention can be used for preparing a metallocene catalyst, and the method comprises the following steps:
(1) adding the carrier and the hydrocarbon solvent obtained by the method into a reactor, and stirring to form a mixed dispersion reaction system;
(2) adding MAO into the reaction system, reacting for a period of time, and washing with a hydrocarbon solvent;
(3) adding a metallocene compound into a reaction system to carry out loading of an active center;
(4) washing with hydrocarbon solvent, drying to obtain the final catalyst.
The above washing is preferably carried out three times.
The silica gel carrier has an average particle size in the range of 10-1000 μm and a surface area in the range of 1-500m2Between/g, the porosity of the pores with a diameter of less than 10 μm is between 0.1 and 2mL/g (excluding macropores, i.e. pores with a diameter of more than 10 μm); the support pore size, expressed as the average diameter of the pores, ranges between 0.01 and 2 μm.
The hydrocarbon solvent comprises aliphatic or aromatic hydrocarbon compounds, especially C5～C15Aliphatic or aromatic hydrocarbon compounds, such as toluene, benzene, n-pentane, isopentane, hexane, heptane, octane or decane, preferably toluene or n-hexane.
The atomic ratio of the aluminum atom in the MAO to the transition metal of the metallocene compound is 50:1 to 300: 1.
Metallocene compounds generally refer to a class of organometallic complexes consisting of a transition metal element M with at least one cyclopentadiene or cyclopentadiene derivative as ligand. The metallocene compound is the core of the metallocene catalyst and provides an active center for the catalyst.
According to the invention, the silica gel can be various silica gels and porous silica for olefin polymerization catalyst carriers.
The inert gas may be any of various gases that do not chemically interact with the support, MAO, and metallocene compound. For example, the inert gas may be nitrogen or argon.
The transition metal element M is preferably zirconium, titanium or hafnium.
The metallocene compound is selected from but not limited to Cp2MCl2、(Me5Cp)2MCl2、(RCp)2MCl2、(R1R2Cp)2MCl2Or Ind2MCl2。R，R1，R2Preferably C1-C5And (c) one of the alkyl groups of (a), more preferably n-butyl. Cl is chlorine. Cp is cyclopentadienyl or a cyclopentadienyl derivative. Ind is indenyl and Me is methyl.
Said C is1-C5The alkyl group of (a) may be one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl and neopentyl.
The cyclopentadienyl is n-butyl cyclopentadienyl, sec-butyl cyclopentadienyl, isobutyl cyclopentadienyl, tert-butyl cyclopentadienyl, etc.
The metallocene compounds include, but are not limited to: bis (tert-butylcyclopentadienyl) zirconium dichloride, bis (cyclopentadienyl) hafnium dichloride, bis (cyclopentadienyl) zirconium dimethyl, bis (cyclopentadienyl) hafnium dimethyl, bis (n-butylcyclopentadienyl) zirconium dichloride, bis (n-butylcyclopentadienyl) hafnium dichloride, bis (n-butylcyclopentadienyl) zirconium dimethyl, bis (n-butylcyclopentadienyl) zirconium dichloride, bis (dimethylcyclopentadienyl) zirconium dichloride, bis (tetramethylcyclopentadienyl) zirconium dimethyl, bis (tetramethylcyclopentadienyl) zirconium dichloride, bisindenyl zirconium dichloride, methylene bridged bisindenyl zirconium dichloride, and bis (4, 5, 6, 7-tetrahydro-1-indenyl) zirconium dichloride.
The metallocene catalyst of the present invention is particularly suitable for ethylene polymerization.
The method for ethylene polymerization by using the metallocene catalyst comprises the following steps:
(1) heating the reaction kettle, treating for a period of time in a vacuum state, and replacing with high-purity nitrogen for later use;
(2) then adding a metallocene catalyst, stirring, and heating to a certain polymerization temperature;
(3) introducing ethylene gas to the polymerization pressure, keeping the pressure and the temperature in the polymerization kettle constant, and reacting for a certain time;
(4) stopping feeding ethylene, stopping stirring, cooling and discharging to obtain the ethylene polymer.
The invention has the following advantages:
(1) by adopting the preparation method of the invention to carry out thermal activation treatment on the porous carrier, through program control and glycol treatment in the cooling process, stress concentration generated in the cooling process can be reduced, the breakage of carrier particles is reduced, and the obtained silica gel carrier can better keep original characteristics (aperture, pore volume, specific surface area and the like) so as to enrich hydroxyl on the surface layer of the silica gel; not only the thermal activation of the silica gel is completed, but also the chemical treatment of the carrier is completed.
(2) The metallocene catalyst prepared by adopting the carrier of the invention is beneficial to the loading of an active center, the activation efficiency of MAO is high, and the activity of the obtained catalyst is improved.
Detailed Description
The invention is further illustrated below with reference to examples, which are provided only for illustration of the invention, and the test methods therein are as follows.
(1) The form characterization method of the silica gel particles comprises the following steps: the analysis is carried out by a Quantachrome NOVA 4200e full-automatic specific surface area and pore size distribution analyzer. Degassing the sample at 300 ℃ for 3 hours, cooling to room temperature, accurately weighing the mass of the degassed sample, and then carrying out isothermal adsorption and desorption analysis on the sample under the condition of 77K.
(2) The average particle size (D50) of the silica gel particles was characterized by measurement using a Malvern Mastersizer 2000 laser particle sizer, and particle size measurements were performed after wet dispersing the samples.
(3) The content analysis of the ethylene glycol in the silica gel adopts a drying weight loss method.
(4) Calculation of the polymerization Activity of the catalyst: the activity of the catalyst is the ratio of the total weight of polyethylene obtained by polymerization to the amount of catalyst added in 1 hour.
(5) And (3) measuring the contents of aluminum and zirconium elements in the metallocene catalyst: inductively coupled plasma emission spectroscopy (ICP) analysis was used. The instrument model is as follows: agilent Inc. of America (ICP-OES 5100 VDV); the experimental conditions are as follows: BF Power 1.3KW, plasma gas flow 12L/min, pump speed 12rpm, lift time: 15s, axial observation.
Silica SiO in the examples2A commercially available 955 silica gel powder is used. The fluidizing gas was high purity nitrogen.
Example 1
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The temperature of the activator is raised to 200 ℃ within 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step:
(4) the temperature of the activator is reduced to 200 ℃ after 2 hours, and then the temperature is kept for 1 hour.
(5) The temperature of the activator is continuously reduced to 212.5 ℃ after 1 hour, and the temperature is maintained for 1 hour.
(6) Weighing ethylene glycol according to 1 percent of the mass of the silica gel, gasifying the ethylene glycol and introducing the gasified ethylene glycol into an activator along with fluidizing gas, and treating for SCWas 30 minutes.
(7) And continuously cooling the activator, cooling to room temperature after 1 hour, discharging, sealing and storing.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of the carrier was dispersed in 30mL of toluene with stirring, and 25mmol of the carrier was addedThe MAO solution was stirred at 50 ℃ for 1 hour, and the solid particles were washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Example 2
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The temperature of the activator is raised to 200 ℃ within 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step:
(4) the temperature of the activator is reduced to 200 ℃ after 2 hours, and then the temperature is kept for 1 hour.
(5) The temperature of the activator is continuously reduced to 222.5 ℃ after 1 hour, and the temperature is maintained for 1 hour.
(6) Weighing ethylene glycol according to 5 percent of the mass of the silica gel, gasifying the ethylene glycol and introducing the gasified ethylene glycol into an activator along with fluidizing gas, and treating for SCIt was 60 minutes.
(7) And continuously cooling the activator, cooling to room temperature after 1 hour, discharging, sealing and storing.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added and the mixture is stirred at 50 ℃ for 1 hour, and the solid particles are then washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Example 3
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The temperature of the activator is raised to 200 ℃ within 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step:
(4) the temperature of the activator is reduced to 200 ℃ after 2 hours, and then the temperature is kept for 1 hour.
(5) The activator is continuously cooled to 232.5 ℃ after 1 hour, and then the temperature is kept for 1 hour.
(6) Weighing according to 2 percent of the mass of the silica gelTaking ethylene glycol, gasifying the ethylene glycol and introducing the gasified ethylene glycol into an activator along with fluidizing gas, and treating for a time SCWas 15 minutes.
(7) And continuously cooling the activator, cooling to room temperature after 1 hour, discharging, sealing and storing.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added and the mixture is stirred at 50 ℃ for 1 hour, and the solid particles are then washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Example 4
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The temperature of the activator is raised to 200 ℃ within 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step:
(4) the temperature of the activator is reduced to 200 ℃ after 1 hour, and then the temperature is kept for 1 hour.
(5) The temperature of the activator is continuously reduced to 222.5 ℃ after 1 hour, and the temperature is maintained for 1 hour.
(6) Weighing ethylene glycol according to 4 percent of the mass of the silica gel, gasifying the ethylene glycol and introducing the gasified ethylene glycol into an activator along with fluidizing gas, and treating for SCWas 40 minutes.
(7) And continuously cooling the activator, cooling to room temperature after 1 hour, discharging, sealing and storing.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added and the mixture is stirred at 50 ℃ for 1 hour, and the solid particles are then washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Example 5
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The temperature of the activator is raised to 200 ℃ within 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step:
(4) the temperature of the activator is reduced to 200 ℃ after 1 hour, and then the temperature is kept for 1 hour.
(5) The temperature of the activator is continuously reduced to 222.5 ℃ after 1 hour, and the temperature is maintained for 1 hour.
(6) Weighing ethylene glycol according to 3 percent of the mass of the silica gel, gasifying the ethylene glycol and introducing the gasified ethylene glycol into an activator along with fluidizing gas, and treating for SCWas 30 minutes.
(7) And continuously cooling the activator, cooling to room temperature after 1 hour, discharging, sealing and storing.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added and the mixture is stirred at 50 ℃ for 1 hour, and the solid particles are then washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Example 6
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The temperature of the activator is raised to 200 ℃ within 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step:
(4) the temperature of the activator is reduced to 200 ℃ after 1 hour, and then the temperature is kept for 1 hour.
(5) The temperature of the activator is continuously reduced to 222.5 ℃ after 1 hour, and the temperature is maintained for 1 hour.
(6) Weighing ethylene glycol according to 8% of the mass of the silica gel, gasifying the ethylene glycol and introducing the gasified ethylene glycol into an activator along with fluidizing gas, and treating for SCWas 30 minutes.
(7) And continuously cooling the activator, cooling to room temperature after 1 hour, discharging, sealing and storing.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added and the mixture is stirred at 50 ℃ for 1 hour, and the solid particles are then washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Comparative example 1
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The temperature of the activator is raised to 200 ℃ within 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step:
(4) the temperature of the activator is reduced to 200 ℃ after 1 hour, and then the temperature is kept for 1 hour.
(5) The temperature of the activator is continuously reduced to 222.5 ℃ after 1 hour, and the temperature is maintained for 1 hour.
(6) And continuously cooling the activator, cooling to room temperature after 1 hour, discharging, sealing and storing.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added and the mixture is stirred at 50 ℃ for 1 hour, and the solid particles are then washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Comparative example 2
The silica gel treatment process is divided into a temperature rising section and a temperature reduction section, and specifically comprises the following steps:
a temperature rise section step:
(1) and (3) weighing a certain amount of silica gel according to the loading coefficient of 0.6 at room temperature, loading into an activator, and adjusting the flow of fluidizing gas to enable silica gel particles to be in a fluidized state.
(2) The activator is heated to 200 ℃ for 1.5 hours, and the temperature is kept constant for 1 hour.
(3) The activator is continuously heated, the temperature is raised to 600 ℃ for 1.5 hours, and the temperature is kept constant for 2 hours.
A cooling section step: and (4) closing the activator for heating, and cooling at the ambient temperature by using a natural cooling mode.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added and the mixture is stirred at 50 ℃ for 1 hour, and the solid particles are then washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
Comparative example 3
The support was the support prepared in comparative example 1.
The preparation method of the catalyst comprises the following steps:
accurately weighing the treated SiO under the protection of high-purity nitrogen23.0g of support are dispersed with stirring in 30mL of toluene, 25mmol of MAO solution are added, then 0.084g of ethylene glycol are added, stirring is carried out at 50 ℃ for 1 hour, and the solid particles are washed 3 times with 30mL of toluene each time. After the washing, 30mL of toluene is added, then 0.109g of bis (tert-butylcyclopentadienyl) zirconium dichloride is added, the mixture is stirred for 2 hours at 25 ℃, the catalyst particles are washed by n-hexane for 3 times, the amount of n-hexane is 30mL each time, and finally the temperature is raised and the solvent is removed by drying, so that the metallocene catalyst powder is obtained.
The polymerization method comprises the following steps:
heating the reaction kettle, treating for a period of time in a vacuum state, replacing for at least three times by high-purity nitrogen, then adding 0.25g of solid catalyst into the reaction kettle, starting stirring, heating the reaction kettle to 92 ℃, adding ethylene monomer until the reaction pressure is 1.2MPa, keeping the reaction temperature and pressure constant, maintaining the polymerization reaction for 1 hour, cooling, and discharging to obtain the metallocene ethylene polymer. The results of the silica gel pore structure and the ethylene glycol content analysis are shown in table 1, and the results of the catalyst analysis are shown in table 2.
TABLE 1 analysis results of silica gel pore structure and ethylene glycol content
Note: the content means weight percentage.
According to the experimental data and results in table 1, the proper content of ethylene glycol is added, and the content percentage is 1-5%, so that the silica gel carrier can keep the original characteristics, and the characteristics such as specific surface area, pore diameter, pore volume, particle size and the like are not greatly influenced. In example 6, the amount of ethylene glycol was too high to reach 7.8%, and various characteristics of the silica gel carrier were affected to different degrees, so that it is very important to select the amount of ethylene glycol for the preparation of the silica gel carrier. In comparative example 1 and comparative example 2, programmed cooling and natural cooling were respectively used in the cooling stage, and no ethylene glycol was added in the thermal activation process, and it can be known from the experimental results that no matter which cooling method was used, the characteristics of the silica gel carrier were greatly affected in all aspects due to no addition of ethylene glycol.
TABLE 2 catalyst analysis and evaluation results
Note: the content means weight percentage.
According to the experimental results of Table 2, in comparative examples 1-6 and comparative examples 1-3, the silica gel obtained by the preparation method of the present invention maintained high levels of both aluminum content and zirconium content, which was beneficial to the loading of active sites, and the MAO activation efficiency was high, and the activity of the obtained catalyst was improved. In example 6, the catalyst activity improvement was limited due to the excessively high amount of ethylene glycol. In comparative examples 1 and 2, ethylene glycol was not used, and the catalyst activity was significantly weak. In comparative example 3, the catalyst activity was improved compared to comparative examples 1 and 2 by adding ethylene glycol during the preparation of the catalyst, but it was significantly lower than examples 1 to 5 of the present invention and was not as good as example 6 of the present invention.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (8)
1. A process for preparing silica gel includes activating silica gel, and the activating procedure includes two steps of temp raising and temp lowering, in which glycol is introduced.
2. The method according to claim 1, wherein the temperature rising step is carried out by the following steps:
(1) weighing a silica gel carrier, loading the silica gel carrier into an activator, and adjusting the flow of fluidizing gas to enable the silica gel carrier to be in a fluidizing state;
(2) heating the activator, raising the temperature from room temperature to the specified temperature within a certain time, and keeping the temperature constant;
(3) continuously heating to the maximum activation temperature T within a certain timeSAnd keeping the temperature constant.
3. The preparation method according to claim 1, wherein the cooling process of the cooling section comprises the following steps:
(4) cooling with an activator by SJ1Time cooling TJ1Constant temperature time SH1；
(5) The activator is continuously cooled through SJ2Time cooling TJ2Constant temperature time SH2；
(6) Heating a certain quantity of glycol to gasify, and feeding it into activator with fluidizing gas, at the time of carrier temp. TCControlling the processing time to be SC；
(7) The activator is continuously cooled through SJ3Cooling to room temperature, discharging, sealing and storing.
4. The method according to claim 3, wherein S is used in step (4)J11.0 to 4.0 hours, SH10.5-2.0 hours, TJ1At the temperature of 100 ℃ and 250 ℃; s in step (5)J20.5-2.0 hours, SH20.5-2.0 hours, TJ2At the temperature of 100 ℃ and 300 ℃; processing time S in step (6)C15-60 minutes; in the step (6), the dosage of the ethylene glycol is 1-10% of the mass of the silica gel carrier.
5. The method according to claim 3, wherein the temperature T of the carrier is controlled when the cooling program is setCBelow the boiling point T of ethylene glycolFTemperature difference (T) between boiling point of ethylene glycol and temperature of carrierF-TC) Is 10-30 ℃.
6. A silica gel carrier obtained by the production method according to claims 1 to 5.
7. The silica gel carrier as claimed in claim 6, which has a specific surface area of 300-320m2The volume of pores is 1.55-1.75mL/g, the average pore diameter is 21-25nm, the particle diameter is 32-35 μm, and the content of glycol is 1-5 wt%.
8. Use of a silica gel support according to claims 6-7 as a support for a metallocene catalyst.
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| CN102002120A (en) * | 2010-09-20 | 2011-04-06 | 中国海洋石油总公司 | Method for preparing special silica gel carrier with large pore volume and large specific surface area |
| WO2016176189A1 (en) * | 2015-04-29 | 2016-11-03 | Chevron Phillips Chemical Company Lp | Methods of preparing a catalyst |
| CN107286276A (en) * | 2016-04-13 | 2017-10-24 | 中国石油天然气股份有限公司 | Preparation method of catalyst and application of catalyst |
| CN108203479A (en) * | 2016-12-20 | 2018-06-26 | 中国石油天然气股份有限公司 | Preparation method of supported polyethylene catalyst |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102002120A (en) * | 2010-09-20 | 2011-04-06 | 中国海洋石油总公司 | Method for preparing special silica gel carrier with large pore volume and large specific surface area |
| WO2016176189A1 (en) * | 2015-04-29 | 2016-11-03 | Chevron Phillips Chemical Company Lp | Methods of preparing a catalyst |
| CN107286276A (en) * | 2016-04-13 | 2017-10-24 | 中国石油天然气股份有限公司 | Preparation method of catalyst and application of catalyst |
| CN108203479A (en) * | 2016-12-20 | 2018-06-26 | 中国石油天然气股份有限公司 | Preparation method of supported polyethylene catalyst |
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