CN114621369B

CN114621369B - Ethylene gas phase polymerization grade switching agent and preparation method thereof

Info

Publication number: CN114621369B
Application number: CN202011461764.2A
Authority: CN
Inventors: 王登飞; 何书艳; 闫义彬; 郭峰; 任鹤; 赵增辉; 赵铁凯; 王磊; 王玉茹; 李广东
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2020-12-10
Filing date: 2020-12-10
Publication date: 2023-11-28
Anticipated expiration: 2040-12-10
Also published as: CN114621369A

Abstract

The invention relates to an ethylene gas-phase polymerization grade switching agent which is used for switching titanium catalysts into chromium catalysts on line in a gas-phase polyethylene device, wherein the raw materials of the ethylene gas-phase polymerization grade switching agent consist of ammonium fluoride salts, aluminum stearate and inorganic oxide dispersing agents, the total content of the ammonium fluoride salts and the aluminum stearate is 0.1-10.0 wt%, the molar ratio of the ammonium fluoride salts to the aluminum stearate is 1-5:1, and the content of the inorganic oxide dispersing agents is 90.0-99.9 wt%. The invention also relates to a preparation method of the ethylene gas-phase polymerization brand switching agent. The polyethylene gas-phase polymerization grade switching agent can enable the gas-phase polyethylene device to be switched into chromium-series catalysts on line for production, the whole catalyst switching process does not need to add new catalyst feeding equipment, the device is not required to stop and a seedbed is not required to be replaced, the operation is simple, the implementation is easy, and the transition time is short.

Description

Ethylene gas phase polymerization grade switching agent and preparation method thereof

Technical Field

The invention relates to a fluidized bed polyethylene process, in particular to an ethylene gas phase polymerization brand switching agent.

Background

Polyethylene (PE) mainly includes Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), high Density Polyethylene (HDPE) and some products with special properties. Since LLDPE has a molecular structure similar to that of HDPE and is linear, and is produced in the same place as a portion of HDPE, many newly designed devices produce 0.910 to 0.970g/cm by varying the feed composition and process parameters ³ Is a full density polyethylene (LLDPE/HDPE swing units). Most of the full-density polyethylene devices mainly produce LLDPE and can produce HDPE brands, and the full-density polyethylene device has quite great flexibility and market strain capacity, so that the full-density polyethylene device is fast in development and becomes a development trend of PE production devices. Along with the establishment and production of a plurality of PE newly-built or expanded devices, the PE production capacity of China is continuously increased.

The current world advanced and mature full density gas phase process mainly comprises Uniopl process of Unistation company, innovene process of Inoes company, spherilene process of Basell company, evolue process of Sanjing chemical company and North Star (Basar) process of North European chemical company, wherein Unipol process of UCC in the United states accounts for about 50 percent. The catalyst is the core of the olefin polymerization process, and the catalyst system commonly used in the gas phase polyethylene process comprises three main types of Z-N, chromium-based and metallocene catalysts. The three types of catalysts produce products that are each characterized. The production plant generally selects which catalytic system to use for the production of polyethylene depending on the change in demand in the downstream market. This requires the apparatus to switch between catalysts. The three catalyst systems are mutually incompatible, and the activities and process control parameters are greatly different from each other. In general, the titanium catalyst or the metallocene catalyst is a poison of the chromium catalyst in the gas-phase polyethylene process, and the catalyst product is regenerated after the titanium catalyst or the metallocene catalyst product is produced, so that the catalyst or the metallocene catalyst in the bed layer is thoroughly cleaned, and the whole process time is longer.

Zhou Pingdeng in the sixth of the China society of Petroleum, in the 2002, a key description is given of how to realize continuous and stable switching of titanium and chromium products under two different catalyst systems after the 2002 expansion of Dushan petrochemical company, and particularly, the key points of controlling the product performance, the process transfer process and the process parameters in the transfer process of high-density HD5410 brand and chromium brand HD4801 produced by titanium catalysts are analyzed in detail and summarized empirically. However, specific switching processes and operation steps of the titanium-based and chromium-based catalysts are not disclosed.

CN201510774219.1 discloses a gas phase fluidized bed on-line catalyst switching method, which comprises the following steps: closing hydrogen feeding in advance, consuming hydrogen in a reaction system, stopping adding the catalyst during switching, returning the first catalyst in the catalyst feeder, thoroughly purging the whole catalyst feeding and conveying system by refined nitrogen, and then conveying the second catalyst. The first catalyst in the bed is consumed at a lower load maintaining the original process conditions of the reactor. The hydrogen in the reactor was replaced with nitrogen to below 250ppm when venting of the reactor occurred. Small additions of metallocene catalyst to the reactor maintained the reaction at a lower load, displacing the bed. The technology realizes the switching between catalysts of different systems without stopping and changing beds. However, the technology needs to close the hydrogen feeding 2-5 days in advance, so that a large amount of transition materials can be generated, and the profit and benefit of the production device are affected.

CN201580075805.5 discloses a method for conversion between two incompatible catalyst systems, a Z-N catalyst system and a metallocene catalyst, said method comprising: (a) Stopping introducing a first catalyst from a first catalyst feed system into the reactor; (b) Introducing a catalyst deactivator to at least partially deactivate a first catalyst within the reactor; (c) A second catalyst is introduced into the reactor by a second catalyst feed system that is independent of the first catalyst feed system. The technology can realize the back and forth switching of the Z-N catalyst system and the metallocene catalyst on the polyethylene device, but the switching process can be realized by using two independent catalyst feeding systems. Because of patent licensing and cost savings, existing plants rarely design stand-by independent catalyst feed systems. In addition, in a device designed with two sets of independent catalyst aggregate systems, if the catalyst feed system is not treated cleanly in time during the switching process, the previously operated catalyst system can easily cause the blockage of the feed system, increasing the risk of device shutdown.

CN201680082258.8 discloses a process for transitioning from a first continuous polymerization conducted in a gas phase reactor in the presence of a metallocene catalyst to a second polymerization conducted in the gas phase reactor in the presence of a ziegler-natta catalyst, wherein the metallocene catalyst and the ziegler-natta catalyst are incompatible, the process comprising: (a) Discontinuing the introduction of the metallocene catalyst into the gas phase reactor; (b) Introducing an effective amount of cyclohexylamine into the reactor to at least partially deactivate the metallocene catalyst; (c) Introducing an organometallic compound into the reactor and reacting the organometallic compound with cyclohexylamine; (d) Degassing the gaseous composition of the reactor and establishing a new composition within the reactor for the second polymerization using a ziegler-natta catalyst; (e) The Ziegler-Natta catalyst is introduced into the reactor. The technology can be realized by using two independent catalyst feeding systems in the switching process.

CN201210402797.9 discloses a process for switching between gas-phase polyethylene titanium-based and chromium-based catalysts. The process firstly utilizes a terminator CO ₂ Terminating the reaction of the polyethylene titanium catalyst, then carrying out nitrogen substitution, and when the nitrogen substitution is completed, injecting a eliminator H of the titanium catalyst and a cocatalyst thereof into the reactor ₂ O reacts, and finally, after the components of the reactor are regulated, chromium-based catalyst is added for establishing reaction, and the whole catalyst switching process does not need to replace a seed bed. But the workerThe process requires CO injection into the reactor during the switching process ₂ And small molecule polar substances such as water, which are all poisons for catalysts. After the chromium-based catalyst is injected into the reactor, the chromium-based catalyst is firstly adsorbed on a seed bed of the reactor, and N is needed before the reaction is established by injecting the chromium-based catalyst into the reactor again ₂ The polar materials are removed by pressure displacement. In the process, not only the original raw materials such as ethylene and the like in the reactor are required to be emptied, but also a large amount of nitrogen is required to be replaced, so that raw materials are wasted, and the cost is increased; causing the reactor level to be maintained at a low level at the same time to avoid the formation of sheeting in the reactor or blockage of fines entrained in the recycle line, resulting in forced shut down of the production plant.

There is therefore a great need for a fast gas phase polyethylene incompatible catalyst system such as a titanium based and chromium based catalyst, a metallocene catalyst and a chromium based switching technique that does not require replacement of the seedbed nor injection of catalyst poisons into the reactor. According to the ethylene gas-phase polymerization grade switching agent and the switching method, new equipment is not required, the whole catalyst switching process is not required to be stopped or catalyst poison is not required to be injected into the reactor, replacement of a seed bed and nitrogen pressure replacement are avoided, material loss and equipment loss are reduced, operation risks and production cost are reduced, and transition time is shortened. The method is simple to operate and easy to implement.

Disclosure of Invention

Aiming at the current situations that the device is stopped easily or the operation steps are complicated, the transition time is long and the like in the catalyst switching process of different systems in the existing gas phase polyethylene process, the invention provides the ethylene gas phase polymerization grade switching agent, no new equipment is needed, the whole catalyst switching process does not need to stop or inject catalyst poison into a reactor, the replacement of a seedbed and the replacement of nitrogen pressure are avoided, the material loss and the equipment loss are reduced, the operation risk and the production cost are reduced, and the transition time is shortened. The invention has simple operation and easy implementation.

The invention provides an ethylene gas-phase polymerization grade switching agent which is used for switching titanium catalysts into chromium catalysts on line in a gas-phase polyethylene device, wherein the raw materials of the ethylene gas-phase polymerization grade switching agent consist of ammonium fluoride salt, aluminum stearate and inorganic oxide dispersing agents, the total content of the ammonium fluoride salt and the aluminum stearate is 0.1-10.0 wt%, the molar ratio of the ammonium fluoride salt to the aluminum stearate is 1-5:1, and the content of the inorganic oxide dispersing agents is 90.0-99.9 wt%.

The ethylene gas-phase polymerization grade switching agent is preferably at least one of ammonium fluoride salt, tetrabutylammonium fluoride salt, hydrogen fluoride ammonium salt, hexafluorosilicic acid ammonium salt, tetrabutyl difluorotriphenyl ammonium salt and homologs of the ammonium salts.

The ethylene gas-phase polymerization grade switching agent is preferably silicon dioxide subjected to high-temperature activation treatment or chemical activation treatment.

The ethylene gas phase polymerization grade switching agent of the invention, wherein the silicon dioxide has a particle diameter of 1-100 μm and a pore volume of 0.5-3.0 cm ³ Per gram, a specific surface area of 100 to 500m ² /g。

The ethylene gas-phase polymerization grade switching agent disclosed by the invention is preferable in that the high-temperature activation treatment comprises the following steps: firstly drying an inorganic oxide dispersing agent, and then heating and activating, wherein the heating and activating process is to raise the temperature from room temperature to 150-200 ℃ at a heating rate of 5-10 min/DEG C, keep the temperature for 3.0-5.0 h, then raise the temperature to 400-600 ℃ at 1-5 min/DEG C, keep the temperature for 5.0-20.0 h, and finally lower the temperature to room temperature at 5-20 min/DEG C; the whole activation process is protected by nitrogen.

Therefore, the invention also provides a preparation method of the ethylene gas-phase polymerization grade switching agent, which comprises the following steps:

(1) Firstly preparing ammonium fluoride salt and inert alkane into a solution at 20-30 ℃ to form mother solution A;

(2) Adding an inorganic oxide dispersing agent into the mother solution A, stirring and soaking for 1-10 hours, pulping to obtain a mixture B, and performing activation treatment on the mixture B to obtain a solid dispersing agent C;

(3) Preparing aromatic hydrocarbon solution D with aluminum stearate concentration of 1 mol%;

(4) Mixing the aromatic hydrocarbon solution D with the solid dispersing agent C, stirring and reacting for 10-24 hours at 20-30 ℃, and sequentially filtering and drying in an inert gas environment to obtain a finished product.

The preparation method of the ethylene gas-phase polymerization grade switching agent is characterized in that the inert alkane solvent is preferably pentane, hexane, heptane, octane, benzene, toluene, xylene or isomers of the alkanes.

The preparation method of the ethylene gas-phase polymerization grade switching agent is characterized in that the inert gas is preferably nitrogen.

The preparation method of the ethylene gas-phase polymerization grade switching agent is characterized in that the aromatic hydrocarbon solution D is preferably toluene solution.

The specific scheme of the invention is as follows:

the ethylene gas-phase polymerization grade switching agent is used for switching titanium catalysts into chromium catalysts on line in a gas-phase polyethylene device, and consists of ammonium fluoride salt, aluminum stearate and inorganic oxide dispersing agents, wherein the total of the ammonium fluoride salt and the aluminum stearate accounts for 0.1-10.0%, the inorganic oxide dispersing agents account for 90.0-99.9%, and the molar ratio of the ammonium fluoride salt to the aluminum stearate is 1:1; the preparation method comprises (1) preparing ammonium fluoride salt and inert alkane into inert alkane solution at room temperature to form mother solution A; (2) Adding an inorganic oxide dispersing agent into the mother solution A, stirring and soaking for 1-10 hours, pulping to obtain a mixture B, and performing activation treatment on the mixture B to obtain a treated solid dispersing agent C; (3) Preparing aluminum stearate aromatic hydrocarbon solution D according to the molar ratio of ammonium fluoride salt to aluminum stearate of 1:1; (4) Mixing the aluminum stearate aromatic hydrocarbon solution D with the solid dispersing agent C, stirring at room temperature for reaction for 10-24 hours, and sequentially filtering and drying in an inert gas environment to obtain a finished product.

The ethylene gas phase polymerization grade switching agent is characterized in that the particle diameter of the silicon dioxide after high temperature activation is 1-100 mu m, and the pore volume is 0.5-3.0 cm ³ Per gram, a specific surface area of 100 to 500m ² /g。

The ethylene gas phase polymerization grade switching agent is characterized in that the high-temperature activation step is as follows: firstly drying an inorganic oxide dispersing agent, and then heating and activating, wherein the heating and activating process is to raise the temperature from room temperature to 150-200 ℃ at a heating rate of 5-10 min/DEG C, keep the temperature for 3.0-5.0 h, then keep the temperature for 5.0-20.0 h at a temperature of 1-5 min/DEG C to 400-600 ℃, and finally cool the temperature to room temperature at a temperature of 5-20 min/DEG C; the whole activation process is protected by nitrogen.

The preparation method of the ethylene gas-phase polymerization grade switching agent is characterized by comprising the following steps of:

(1) Preparing ammonium fluoride salt into inert alkane solution at room temperature to form mother solution A;

(2) Adding an inorganic oxide dispersing agent into the mother solution A, stirring and soaking for 1-10 hours, pulping to obtain a mixture B, and activating the mixture B to obtain a treated solid dispersing agent C;

(3) Weighing aluminum stearate according to the molar ratio of ammonium fluoride salt to aluminum stearate of 1:1, and preparing an aromatic hydrocarbon solution D containing 1mol% of aluminum stearate;

(4) Mixing the aluminum stearate aromatic hydrocarbon solution D with the solid dispersing agent C, stirring at room temperature for reaction for 10-24 hours, and sequentially filtering and drying in an inert gas environment to obtain a finished product.

The polyethylene gas phase polymerization grade switching is mainly used for switching titanium catalysts into chromium catalysts on line in a gas phase polyethylene device.

The invention has the beneficial effects that:

compared with the prior art, the ethylene gas phase polymerization grade switching agent provided by the invention can enable a gas phase polyethylene device to be rapidly and conveniently switched from a titanium catalyst product to a chromium catalyst for production on line. The whole catalyst switching process does not need to replace a seedbed, does not need to stop the device, avoids nitrogen replacement and a large amount of raw materials to be emptied, and has the advantages of simple operation, easy implementation and short transition time. Meanwhile, when the catalyst is switched, the brand switching agent can also adsorb a large amount of titanium catalysts added into the reactor before, and ammonium fluoride salt in the ethylene gas-phase polymerization brand switching agent can deactivate the active center of titanium, so that the catalyst is prevented from forming a caking in a circulation system in the switching process, the risk of starting and stopping the device is reduced, and the material balance pressure and the device production fluctuation of the upstream and downstream of the polyethylene device can be effectively reduced.

Drawings

FIG. 1 is a schematic view of a gas phase fluidized bed polyethylene reactor according to the present invention

FIG. 2 is a catalyst on-line switching program diagram of the present invention.

Fig. 3 is a typical catalyst switching program diagram of the prior art.

In the figure:

1-a recycle gas compressor;

2-a recycle gas cooler;

3-a discharging intermediate tank;

4-a product bin;

5-a catalyst feeder;

6-a gas phase fluidized bed reactor.

Detailed Description

The following describes embodiments of the present invention in detail: the present example is implemented on the premise of the technical scheme of the present invention, and detailed implementation modes and processes are given, but the protection scope of the present invention is not limited to the following examples, and experimental methods without specific conditions are not noted in the following examples, and generally according to conventional conditions.

Example 1

Preparation of a brand switching agent:

(1) 1kg of ammonium hexafluorosilicate is firstly prepared into a hexane solution at room temperature to form mother solution A;

(2) The mother liquor A was mixed with 50kg 955 type silica carrier (average particle diameter 50 μm, pore volume 1.75 cm) ³ Per g, surface area 300m ² Mixing/g), stirring and soaking for 4 hours, and pulping to obtain a mixture B;

(3) The mixture B is subjected to an activation treatment according to a program: the temperature-rising activation process is that the temperature-rising rate is increased from room temperature to 150 ℃ at 5 min/DEG C, the temperature is kept for 4.0h, then the temperature is kept at 5 min/DEG C to 600 ℃ for 10.0h, and finally the temperature is reduced to the room temperature at 10 min/DEG C; the whole activation process is protected by nitrogen, and a treated solid dispersing agent C is obtained;

(4) Weighing aluminum stearate according to the molar ratio of ammonium fluoride salt to aluminum stearate of 1:1, and preparing an aromatic hydrocarbon solution D containing 1mol% of aluminum stearate;

(5) Mixing the aluminum stearate aromatic hydrocarbon solution D with the solid dispersing agent C, stirring at room temperature for reaction for 20 hours, and sequentially filtering and drying in an inert gas environment to obtain a finished product.

(II) gas phase switching process:

FIG. 1 is a schematic diagram of a gas phase fluidized bed polyethylene reactor according to the present invention. The gas phase polymerization scheme in connection with fig. 1 is: ethylene, hydrogen and high-pressure nitrogen are added into a circulating pipeline before starting, compressed by a circulating gas compressor 1, subjected to heat exchange by a circulating gas cooler 2, and enter the reactor from the bottom of a fluidized bed reactor 6. The full-density polyethylene is produced in a gas-phase fluidized bed reactor 6 under the action of a catalyst, the polyethylene product is free-flowing granules, the index and molecular weight distribution of the resin are controlled by the selection of the catalyst and the adjustment of reaction conditions, and the product density is controlled by controlling the addition amount of a comonomer. The generated polyethylene is discharged into a discharge intermediate tank 3 from the bottom of a gas-phase fluidized bed reactor 6, and the tail gas carried by the polyethylene is discharged into a torch after devolatilization treatment; the polyethylene product is discharged to a product silo 4 for storage.

A method for achieving rapid switching of titanium to chromium catalysts in a 50kg/hr gas phase fluidized bed reactor, comprising the following operative steps, the schematic diagram of which is shown in fig. 2:

(1) titanium catalyst feed unit treatment: maintaining the reaction components unchanged, stopping feeding the titanium catalyst and the reaction materials, discharging the titanium catalyst remained in the catalyst feeder 5 cleanly, and replacing the titanium catalyst with nitrogen pressure of 0.7MPa for more than 10 times, wherein the process takes 1 hour;

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 2:1, terminating the reaction of the titanium catalyst, terminating the reaction after 60 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the catalyst with nitrogen pressure of 0.7MPa for more than 10 times, wherein the process takes 2 hours;

(3) and (3) adjusting the components of the reactor: injecting triethylaluminum as an activity promoter into the gas-phase fluidized bed reactor 6, reintroducing ethylene, hydrogen, nitrogen, comonomers and other reactant materials into the gas-phase fluidized bed reactor 6 after 30 minutes, and starting component adjustment of the gas-phase fluidized bed reactor 6, wherein the process takes 2.5 hours;

(4) The reaction is established again: the chromium-based catalyst was added to the catalyst feeder 5, and after the completion of the adjustment of the composition of the gas-phase fluidized-bed reactor 6, the chromium-based catalyst was charged to establish a reaction, which took 0.5 hour.

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes about 6 hours, and 26 hours are saved compared with the normal switching procedure of the catalyst.

Example 2

Preparation of a brand switching agent:

(1) Preparing 1kg of tetrabutylammonium fluoride into a hexane solution at room temperature to form mother solution A;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount to 5:1, terminating the reaction of the titanium catalyst, terminating the reaction after 30 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the residual ethylene gas phase polymerization grade switching agent for more than 10 times by using nitrogen pressure of 0.7MPa, wherein the process takes 1.5 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes about 5.5 hours, and 26.5 hours are saved compared with the normal switching procedure of the catalyst.

Example 3

Preparation of a brand switching agent:

(1) Preparing 1kg of ammonium bifluoride into a hexane solution at room temperature to form a mother solution A;

(II) gas phase switching process:

A method for achieving rapid switching of titanium to chromium catalysts in a 50kg/hr gas phase fluidized bed reactor 6, comprising the following operative steps, the schematic diagram of which is shown in fig. 2:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount to 8:1, terminating the reaction of the titanium catalyst, terminating the reaction after 30 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the residual ethylene gas phase polymerization grade switching agent for more than 10 times by using nitrogen pressure of 0.7MPa, wherein the process takes 1.5 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes about 5.5 hours, and 27 hours are saved compared with the normal switching procedure of the catalyst.

Example 4

Preparation of a brand switching agent:

(1) Preparing 1kg of ammonium fluoride into a hexane solution at room temperature to form a mother solution A;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 4:1, terminating the reaction of the titanium catalyst, terminating the reaction after 60 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the catalyst with nitrogen pressure of 0.7MPa for more than 10 times, wherein the process takes 2 hours;

Example 5

Preparation of a brand switching agent:

(1) Firstly preparing 1kg of tetrabutyl ammonium difluorotriphenyl silicate into a hexane solution at room temperature to form a mother solution A;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 2:1, terminating the reaction of the titanium catalyst, terminating the reaction after 180 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the catalyst with 0.7MPa nitrogen pressure for more than 10 times, wherein the process takes 4 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes about 8 hours, and is 24 hours less than the normal switching procedure of the catalyst.

Example 6

Preparation of a brand switching agent:

(1) Preparing 0.5kg of ammonium hexafluorosilicate into a hexane solution at room temperature to form a mother solution A;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 6:1, terminating the reaction of the titanium catalyst, terminating the reaction after 60 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the catalyst with nitrogen pressure of 0.7MPa for more than 10 times, wherein the process takes 2 hours;

Example 7

Preparation of a brand switching agent:

(1) 1.5kg of ammonium hexafluorosilicate is firstly prepared into a hexane solution at room temperature to form mother solution A;

(2) The mother liquor A was combined with 50kg 955 type silica support (FlatAverage particle diameter 50 μm and pore volume 1.75cm ³ Per g, surface area 300m ² Mixing/g), stirring and soaking for 4 hours, and pulping to obtain a mixture B;

(II) gas phase switching process:

A method for achieving rapid switching of titanium to chromium based catalysts in a 50kg/hr gas phase fluidized bed reactor 6, comprising the following operational steps, a schematic diagram of which is shown in fig. 2:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 3:1, terminating the reaction of the titanium catalyst, terminating the reaction after 30 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the residual ethylene gas phase polymerization grade switching agent for more than 10 times by using nitrogen pressure of 0.7MPa, wherein the process takes 1.5 hours;

Example 8

Preparation of a brand switching agent:

(1) Preparing 2.0kg of ammonium hexafluorosilicate into a hexane solution at room temperature to form a mother solution A;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 20:1, terminating the reaction of the titanium catalyst, terminating the reaction after 30 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the residual ethylene gas phase polymerization grade switching agent for more than 10 times by using nitrogen pressure of 0.7MPa, wherein the process takes 1.5 hours;

(3) and (3) adjusting the components of the reactor: the gas-phase fluidized bed reactor 6 is injected with the activity promoter triethylaluminum, and after 300 minutes, the reaction material feed such as ethylene, hydrogen, nitrogen, comonomer and the like is reintroduced into the gas-phase fluidized bed reactor 6, and the gas-phase fluidized bed reactor 6 starts component adjustment, and the process takes 7 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes about 10 hours, and is saved by 22 hours compared with the normal switching procedure of the catalyst.

Example 9

Preparation of a brand switching agent:

(1) Preparing 5.0kg of ammonium hexafluorosilicate into a hexane solution at room temperature to form a mother solution A;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 100:1, terminating the reaction of the titanium catalyst, terminating the reaction after 30 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the residual ethylene gas phase polymerization grade switching agent for more than 10 times by using nitrogen pressure of 0.7MPa, wherein the process takes 1.5 hours;

(3) and (3) adjusting the components of the reactor: the gas-phase fluidized bed reactor 6 is injected with the activity promoter triethylaluminum, and after 25 hours, the reaction materials such as ethylene, hydrogen, nitrogen, comonomer and the like are reintroduced into the gas-phase fluidized bed reactor 6 to feed, and the gas-phase fluidized bed reactor 6 starts component adjustment, which takes 27 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes about 30 hours, and is 2 hours less than the normal switching procedure of the catalyst.

Example 10

Preparation of a brand switching agent:

(1) 1.0kg of ammonium hexafluorosilicate is firstly prepared into a hexane solution at room temperature to form mother solution A;

(2) The mother liquor A was reacted with a 50kg W.R.Grace's 957HS type silica support (average particle diameter: 40 μm, pore volume: 1.45 cm) ³ Per g, surface area 300m ² Mixing/g), stirring and soaking for 4 hours, and pulping to obtain a mixture B;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 4:1, terminating the reaction of the titanium catalyst, terminating the reaction after 150 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the residual ethylene gas phase polymerization grade switching agent for more than 10 times by using nitrogen pressure of 0.7MPa, wherein the process takes 3.5 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes 7.5 hours approximately, and 24.5 hours are saved compared with the normal switching procedure of the catalyst.

Example 11

Preparation of a brand switching agent:

(2) The mother liquor A was mixed with 50kg of a PQ 35100 type silica carrier (average particle diameter 90 μm, pore volume 3.02 cm) ³ Per gram, surface area 500m ² Mixing/g), stirring and soaking for 4 hours, and pulping to obtain a mixture B;

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 1:1, terminating the reaction of the titanium catalyst, terminating the reaction after 120 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the catalyst with 0.7MPa nitrogen pressure for more than 10 times, wherein the process takes 3.0 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes 7 hours approximately, and 25 hours are saved compared with the normal switching procedure of the catalyst.

Example 12

Preparation of a brand switching agent:

(2) The mother liquor A was reacted with a 50kg W.R.Grace's 955 type silica support (average particle diameter: 50 μm, pore volume: 1.75 cm) ³ Per g, surface area 300m ² Mixing/g), stirring and soaking for 8 hours, and pulping to obtain a mixture B;

(5) Mixing the aluminum stearate aromatic hydrocarbon solution D with the solid dispersing agent C, stirring at room temperature for reaction for 10 hours, and sequentially filtering and drying in an inert gas environment to obtain a finished product.

(II) gas phase switching process:

(2) treatment of residual catalyst in the reactor: the ethylene gas phase polymerization grade switching agent is added into the catalyst feeder 5 according to the grade switching agent: adding an ethylene gas phase polymerization grade switching agent into a gas phase fluidized bed reactor 6 according to the mass ratio of the raw titanium catalyst feed amount of 2:1, terminating the reaction of the titanium catalyst, terminating the reaction after 30 minutes, stopping feeding the ethylene gas phase polymerization grade switching agent, discharging the residual ethylene gas phase polymerization grade switching agent in a catalyst feeder 5 completely, and replacing the residual ethylene gas phase polymerization grade switching agent for more than 10 times by using nitrogen pressure of 0.7MPa, wherein the process takes 1.5 hours;

(3) and (3) adjusting the components of the reactor: injecting triethylboron as an activity promoter into the gas-phase fluidized bed reactor 6, reintroducing ethylene, hydrogen, nitrogen, comonomers and other reactant materials into the gas-phase fluidized bed reactor 6 after 90 minutes, and starting component adjustment of the gas-phase fluidized bed reactor 6, wherein the process takes 3.5 hours;

The whole catalyst switching process does not need to stop, replace the pressure of the reaction materials and change the seedbed. The whole switching process takes about 6.5 hours, which is 25.5 hours less than the normal switching procedure of the catalyst.

Comparative example 1:

the normal switching procedure of the titanium to chromium catalyst was carried out in a 50kg/hr gas phase fluidized bed reactor, comprising the following steps, a schematic diagram of which is shown in fig. 3:

(1) The titanium catalyst and the reactant are stopped, the residual components in the reactor are replaced by nitrogen, a terminator is injected into the reactor to stop the reaction, meanwhile, the titanium catalyst remained in the catalyst feeder is discharged cleanly, and the titanium catalyst is replaced by nitrogen with the pressure of 0.7MPa for more than 10 times, and the process takes 1 hour.

(2) The discharge procedure was started and the titanium-based polyethylene seed bed in the reactor was completely discharged, which took 1 hour.

(3) The reactor was replaced with 0.7MPa nitrogen, no terminator was detected in the reactor, and the process took 3 hours as judged to be acceptable for the replacement of the device.

(4) The reactor was again fed with the required chromium-based polyethylene seed bed, while the reactor was warmed, nitrogen gas was introduced for replacement, and the dehydration treatment of the seed bed was started, which took 24 hours.

(5) Adding the chromium catalyst into a catalyst feeder, simultaneously reintroducing ethylene, hydrogen, nitrogen, comonomer and other reactant materials into the reactor, starting component adjustment of the reactor, and adding the chromium catalyst to establish a reaction after the component adjustment of the reactor is completed, wherein the process takes 2 hours.

The entire catalyst switching process requires a shutdown, reactant pressure replacement, and replacement of the seedbed, and the catalyst normal switching process takes approximately 32 hours.

Of course, the present invention is capable of other various embodiments and its several details are capable of modification and variation in light of the present invention by one skilled in the art without departing from the spirit and scope of the invention.

Claims

1. The ethylene gas-phase polymerization grade switching agent is used for switching a titanium catalyst into a chromium catalyst on line in a gas-phase polyethylene device, and is characterized in that the raw materials of the ethylene gas-phase polymerization grade switching agent consist of ammonium fluoride salt, aluminum stearate and an inorganic oxide dispersing agent, wherein the total content of the ammonium fluoride salt and the aluminum stearate is 0.1-10.0wt%, the molar ratio of the ammonium fluoride salt to the aluminum stearate is 1-5:1, and the content of the inorganic oxide dispersing agent is 90.0-99.9wt%;

The ammonium fluoride salt is at least one of ammonium fluoride, tetrabutylammonium fluoride, ammonium bifluoride, ammonium hexafluorosilicate, tetrabutylammonium difluorotriphenyl silicate and homologs of the ammonium salts;

the inorganic oxide dispersing agent is silicon dioxide subjected to high-temperature activation treatment or chemical activation treatment;

the preparation method of the ethylene gas-phase polymerization brand switching agent comprises the following steps:

(4) And mixing the aromatic hydrocarbon solution D with the solid dispersing agent C, stirring and reacting for 10-24 hours at 20-30 ℃, and sequentially filtering and drying in an inert gas environment to obtain a finished product.

2. The ethylene gas phase polymerization grade switching agent according to claim 1, wherein the silica has a particle diameter of 1 to 100 μm and a pore volume of 0.5 to 3.0 cm ³ Per gram, a specific surface area of 100-500 m ² /g。

3. The ethylene gas phase polymerization grade switching agent according to claim 1, wherein the step of the high temperature activation treatment is: firstly drying an inorganic oxide dispersing agent, and then heating and activating, wherein the heating and activating process is to raise the temperature from room temperature to 150-200 ℃ at a heating rate of 5-10 min/DEG C, keep the temperature for 3.0-5.0 h, then raise the temperature to 400-600 ℃ at 1-5 min/DEG C, keep the temperature for 5.0-20.0 h, and finally lower the temperature to the room temperature at 5-20 min/DEG C; the whole activation process is protected by nitrogen.

4. A process for preparing the ethylene gas phase polymerization grade switching agent as claimed in claim 1, comprising the steps of:

5. The method for preparing a catalyst for gas-phase polymerization of ethylene according to claim 4, wherein the inert alkane is pentane, hexane, heptane, octane, benzene, toluene, xylene, or isomers of the above alkanes.

6. The method for preparing a gas-phase polymerization grade switching agent for ethylene according to claim 4, wherein the inert gas is nitrogen.

7. The method for preparing a catalyst for gas-phase polymerization of ethylene according to claim 4, wherein the aromatic hydrocarbon solution D is toluene solution.