CN111072798B - Silica gel and preparation method and application thereof - Google Patents
Silica gel and preparation method and application thereof Download PDFInfo
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- CN111072798B CN111072798B CN201811231807.0A CN201811231807A CN111072798B CN 111072798 B CN111072798 B CN 111072798B CN 201811231807 A CN201811231807 A CN 201811231807A CN 111072798 B CN111072798 B CN 111072798B
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Abstract
A silica gel is activated, and the activation process comprises two steps of a temperature rising section and a temperature reducing section, wherein ethylene glycol is introduced into the temperature reducing 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 most commonly used supports is SiO 2 Or SiO physically and chemically modified 2 Most 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 programmed temperature control mode, gradually heating to a specified temperature (such as 400-800 ℃) step by step, activating for a certain time at a high temperature, and then cooling to finish the thermal activation of the silica gel carrier. At present, the influence of process conditions such as a heating process, thermal activation time, 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 basically adds solvent, silica gel, chemical treatment agent, MAO and other components into a 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 andenhancing activity, washing with water, instantly drying, pulverizing and grading particle size. 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. "Advances in the study of silica-supported metallocene catalysts" mention that polyhydroxy radicals can be used in the chemical treatment of silica due to the presence of multiple electron deficient centers Al in the MAO molecule 3+ 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 polymerization, its preparation method and application, wherein the catalyst is a Ziegler-Natta catalyst, the shape of the catalyst carrier is spherical, and the catalyst carrier is divided into three layers from inside to outside, wherein the inner layer is an inert inorganic material, the middle layer is a complex of polyol and magnesium halide deposited on the inert inorganic material, and the outer layer is an organic polymer containing polar functional groups supported on the complex. When the 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 processability of the polymerization product is improved, and the Ziegler-Natta catalyst has the characteristic of high activity. The prior art does not relate to programmed cooling control of silica gel thermal activation, influence of the cooling process on the characteristics of silica collagen, and treatment by using 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; none of the above techniques relate toThe influence of the addition of glycol on the characteristics of the carrier silica gel in 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 300-320m 2 Per gram, pore volume of 1.55-1.75mL/g, average pore diameter of 21-25nm, particle diameter of 32-35 μm, and ethylene glycol content of 1-5wt%.
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 time S And 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 S J1 Time cooling T J1 Constant temperature S H1 。
(5) The activator is continuously cooled through S J2 Time cooling T J2 Constant temperature S H2 。
(6) Heating and gasifying a certain amount of glycol (the boiling point of the glycol is T) F ) And enters the activator with the fluidizing gas, the temperature of the carrier being T C Controlling the processing time to be S C 。
(7) The activator is continuously cooled through S J3 Cooling 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 5ppm.
The charging factor of the silica gel carrier is 0.4-0.8 of the volume of the activator.
In step (3), T S Preferably 400-600 deg.c.
S in step (4) J1 Preferably 1.0-4.0 hours, S H1 Preferably 0.5 to 2.0 hours, T J1 Preferably 100-250 deg.C.
S in step (5) J2 Preferably 0.5-2.0 hours, S H2 Preferably 0.5-2.0 hours, T J2 Preferably 100-300 deg.C.
The dosage of the ethylene glycol in the step (6) is 1-5% of the mass of the silica gel carrier, and the treatment time S is C Preferably 15-60 minutes. When the cooling program is set, the carrier temperature T is controlled C Below T F Temperature difference between the two (T) F -T C ) Preferably 10-30 ℃.
S in step (7) J3 The 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 of 10-1000 μm and a surface area of 1-500m 2 Between/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 C 5 ～C 15 Aliphatic 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 MAO to the transition metal of the metallocene compound is from 50 to 300.
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 a variety of gases that do not chemically interact with the support, MAO, 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 Cp 2 MCl 2 、(Me 5 Cp) 2 MCl 2 、(RCp) 2 MCl 2 、(R 1 R 2 Cp) 2 MCl 2 Or Ind 2 MCl 2 。R，R 1 ，R 2 Preferably C 1 -C 5 More preferably n-butyl. Cl is chlorine. Cp is cyclopentadienyl or a cyclopentadienyl derivative. Ind is indenyl and Me is methyl.
Said C is 1 -C 5 The 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 invention is particularly suitable for ethylene polymerization.
The method for using the metallocene catalyst for ethylene polymerization 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 determined and characterized using a Malvern Mastersizer 2000 laser particle sizer, and particle size measurements were carried out after wet dispersing the samples.
(3) The content analysis of the 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 USA (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 gel SiO in the examples 2 A 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 the specific steps are as follows:
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 for 1 hour.
(3) The activator is heated continuously for 1.5 hours to 600 ℃ and kept at the constant temperature 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 S C Was 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 nitrogen 2 3.0g 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 the reaction 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, the temperature is reduced by 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 S C It 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 nitrogen 2 3.0g 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 the reaction 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 ethylene glycol according to 2 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 S C Was 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 nitrogen 2 3.0g 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 the reaction 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) At room temperature, weighing a certain amount of silica gel according to the charging coefficient of 0.6, loading the silica gel into an activator, and adjusting the flow of fluidizing gas to ensure that silica gel particles are 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 S C Was 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 nitrogen 2 3.0g 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 completion of the washing, 30mL of toluene was added, followed by 0.109g of di (t-butylcyclopentadienyl) was added) And (3) stirring zirconium dichloride for 2 hours at 25 ℃, washing the catalyst particles with n-hexane for 3 times, wherein the amount of n-hexane is 30mL each time, and finally heating and drying to remove the solvent to obtain the metallocene catalyst powder.
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 the reaction 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 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 S C Was 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 nitrogen 2 3.0g of carrier, stirringThen, the mixture was dispersed in 30mL of toluene, 25mmol of MAO solution was added, and the mixture was stirred at 50 ℃ for 1 hour, and then the solid particles were washed with toluene 3 times in an amount of 30mL each. 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, 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 the reaction pressure constant, maintaining the polymerization reaction for 1 hour, cooling, discharging, and obtaining 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 for 1 hour.
(3) The activator is heated continuously for 1.5 hours to 600 ℃ and kept at the constant temperature 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 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 S C Was 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 nitrogen 2 3.0g 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 the reaction 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 nitrogen 2 3.0g 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 the reaction 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 nitrogen 2 3.0g 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, 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 the reaction pressure constant, maintaining the polymerization reaction for 1 hour, cooling, discharging, and obtaining 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 nitrogen 2 3.0g 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 the reaction 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. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications derived therefrom are intended to be within the scope of the invention.
Claims (4)
1. A preparation method of silica gel comprises activating silica gel, wherein the activation process comprises two steps of a temperature rise section and a temperature reduction section, ethylene glycol is introduced into the temperature reduction section, and the dosage of the ethylene glycol is 1-5% of the mass of a silica gel carrier; the temperature rise process of the temperature rise section is carried out according to 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 fluidized state;
(2) The temperature of the activator is raised from room temperature to a certain temperature within a certain time, and the constant temperature is kept;
(3) Continuously heating to the maximum activation temperature T within a certain time S And keeping the temperature constant;
the cooling process of the cooling section is carried out according to the following steps:
(4) Cooling with an activator by S J1 Time cooling T J1 At a constant rateTime of warming S H1 ；
(5) The activator is continuously cooled through S J2 Time cooling T J2 Constant temperature time S H2 ；
(6) Heating a certain quantity of glycol to gasify, and feeding it into activator with fluidizing gas, at the time of carrier temp. T C Controlling the processing time to be S C ；
(7) The activator is continuously cooled through S J3 Cooling to room temperature, discharging, sealing and storing;
s in step (4) J1 1.0 to 4.0 hours, S H1 0.5-2.0 hours, T J1 Is 100-250 ℃; s in step (5) J2 0.5-2.0 hours, S H2 0.5-2.0 hours, T J2 Is 100-300 ℃; processing time S in step (6) C 15-60 minutes; when the temperature reduction program is set, the carrier temperature T is controlled C Below the boiling point T of ethylene glycol F Temperature difference (T) between boiling point of ethylene glycol and temperature of carrier F -T C ) Is 10-30 ℃.
2. A silica gel carrier prepared according to the preparation method of claim 1.
3. The silica gel carrier according to claim 2, having a specific surface area of 300 to 320m 2 Per gram, pore volume of 1.55-1.75mL/g, average pore diameter of 21-25nm, particle diameter of 32-35 μm, and ethylene glycol content of 1-5wt%.
4. Use of a silica gel support according to claim 2 or 3 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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