CN115850549A - Solution polymerization method for olefin ternary polymerization - Google Patents
Solution polymerization method for olefin ternary polymerization Download PDFInfo
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- CN115850549A CN115850549A CN202211425418.8A CN202211425418A CN115850549A CN 115850549 A CN115850549 A CN 115850549A CN 202211425418 A CN202211425418 A CN 202211425418A CN 115850549 A CN115850549 A CN 115850549A
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- 238000006116 polymerization reaction Methods 0.000 title claims abstract description 72
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- 238000010528 free radical solution polymerization reaction Methods 0.000 title claims abstract description 50
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- 229920000642 polymer Polymers 0.000 claims abstract description 95
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- 239000005977 Ethylene Substances 0.000 claims abstract description 50
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- 239000012442 inert solvent Substances 0.000 claims abstract description 33
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- 238000007599 discharging Methods 0.000 claims abstract description 3
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- KWKAKUADMBZCLK-UHFFFAOYSA-N 1-octene Chemical compound CCCCCCC=C KWKAKUADMBZCLK-UHFFFAOYSA-N 0.000 claims description 62
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- 230000008569 process Effects 0.000 claims description 43
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Abstract
The invention discloses a solution polymerization method for olefin ternary polymerization, which comprises the steps of polymerizing ethylene and other two olefins in a reactor in the presence of a catalyst and in the absence of an inert solvent to obtain a ternary polymerization polymer, wherein the other two olefins are respectively represented by the formula CH 2 = CHA and formula CH 2 = CHB, wherein A and B are each a hydrocarbon group having 1 to 8 carbon atoms, and the number of carbons of A and BAdding not less than 5 percent, feeding 75-90 percent of other two olefins in the polymer solution in the reactor, feeding the main catalyst, the cocatalyst, the ethylene and the other two olefins into the reactor, performing polymerization reaction in the reactor, and discharging to obtain the polymer solution; feeding the polymer solution to a solution preheater to obtain a higher temperature polymer solution, and feeding to a separation and recovery unit; alternatively, the polymer solution is fed directly to the separation and recovery unit; and separating the polymer solution entering the separation and recovery unit to obtain a polymer product and a circulating stream containing ethylene and other two olefins.
Description
Technical Field
The invention relates to the technical field of olefin solution polymerization production, in particular to a solution polymerization method for ethylene, 1-butene and 1-hexene ternary polymerization and 1-hexene, 1-hexene and 1-octene ternary polymerization.
Background
Polyolefin products are widely applied to different kinds of products, such as pipelines, automobile parts, films, food packages, electric appliance shells and the like, and the market has different requirements on the performance of polyolefin materials according to application scenes. The copolymer of ethylene and alpha-olefin with high comonomer content is a high-performance thermoplastic elastomer, and compared with common polyolefin plastics, the copolymer has higher comonomer content and lower density in a molecular chain, and is widely applied to the fields of polymer modification, medical treatment and the like. At present, the production of thermoplastic elastomers in industry adopts a solution process, wherein the solution process is a polymerization method for dissolving polymers in a liquid polymerization system, such as an inert solvent, the solution polymerization is a homogeneous liquid polymerization system, and the solution polymerization has the characteristics and advantages of short polymerization time, convenient product grade switching and the like. The process for the solution polymerization of thermoplastic elastomers is carried out at a temperature of between 40 and 160 ℃ and a pressure of less than 20MPa, operating in a polymerization system in the presence of more than 65% by weight of an inert solvent.
Patent CN 10380999B discloses a solution polymerization method of ethylene and α -olefin, which is characterized in that a mixed solvent of two hydrocarbons is adopted, one of the solvents is in a supercritical state under the solution polymerization pressure and temperature, and the method can reduce the viscosity of a reaction system, thereby reducing the difficulty of removing the solvent at the downstream of the polymerization reaction, i.e. the energy consumption of the devolatilization process. Patent CN 1152062C discloses a solution polymerization process using a non-adiabatic loop reactor, in which solvent, monomer and catalyst are circulated in the reaction gas and the heat of the fluid is removed by a heat exchanger. Patent CN 1898275A discloses a process for the slurry or solution polymerization of ethylene and at least one C3-C20 alpha olefin in the presence of a catalyst, a diluent (solvent) and hydrogen, characterized in that the diluent (solvent) is recycled from the outlet line to the hydrogen feed line. It is known in the art that phase stability of olefin solution polymerization is critical and affects process stability. Patent CN 115023448A discloses a method for avoiding phase separation during solution polymerization of ethylene-1-octene copolymer by first modeling the polymer system used for solution polymerization of ethylene-1-octene copolymer and then determining the reaction pressure and temperature conditions to ensure that the polymerized ethylene-1-octene copolymer is completely dissolved in the solvent during the polymerization process. CN 114929763A discloses a method for avoiding phase separation during solution polymerization of ethylene-1-butene copolymer. CN 111630071A proposes to feed inert hydrocarbons satisfying 90 ℃ < boiling point <130 ℃ to the solution polymerization reactor; and/or accumulating inert hydrocarbons meeting 90 ℃ < boiling point <130 ℃ during the polymerization reaction; and/or feeding inert hydrocarbons meeting 90 ℃ < boiling point <130 ℃ into the discharged effluent stream.
The ternary copolymer product of ethylene and two kinds of olefin has unique product performance, and this kind of product is also produced in solution polymerization process widely. Patent CN 107614541B discloses a continuous solution polymerization process for producing ethylene-propylene-diene rubber or propylene-based elastomers, with improved separation efficiency by controlling the temperature at which the polymer solution is heated and controlling the pressure of the separation. Patent CN 105377916B discloses a solution polymerization process for the preparation of copolymers of ethylene- α -olefins-diolefins in the presence of a metallocene and a solvent, comprising a process for removing said solvent and unreacted monomers by means of a gas-liquid separator at a temperature of 150 ℃ to 160 ℃ and at a pressure of 5 to 10 bar.
Although the olefin solution polymerization process adopts more solvents, the selection of the solvents directly influences the stability, operability, product performance and other points of the polymerization reaction, and numerous methods have been proposed in the field, including the adoption of single or multiple hydrocarbons with different proportions as the solvents and the improvement of the separation process to improve the separation efficiency, a new polymerization process for preparing the ethylene-1-butene-1-hexene terpolymer and the ethylene-1-hexene-1-octene terpolymer is still required, so that the diversity of the polymerization products can be realized, the process flow can be simplified, and the energy consumption of the process can be reduced.
Defining:
by "solution polymerization" is meant dissolving the polymer in a liquid polymerization medium, such as an inert solvent or monomer or blends thereof, solution polymerization being homogeneous, meaning wherein the polymer product is dissolved in the polymerization medium. Such systems are preferably not hazy.
"alpha-olefin" means a monoolefin having a double bond at the end of the molecular chain, such as 1-butene, 1-hexene, 1-octene.
Disclosure of Invention
The invention provides a solution polymerization method for olefin terpolymer, which realizes the solution homogeneous polymerization of the olefin terpolymer under the condition of lacking inert solvent from the aspects of the operating pressure of a reactor and polymer products by limiting the types of two olefins except ethylene participating in polymerization and the mass fractions of the two olefins in polymer solution in the reactor and combining the application of a circulating stream.
As is known in the art, polymerization of olefins may occur in the absence of a polymerization inert solvent. Patent application CN 114630844A provides a process for reacting a compound of formula CH in the absence of an inert solvent 2 ＝CHR 1 A first olefin of the formula 2 ＝CHR 2 A second olefin polymerization shown, wherein R 1 Is hydrogen or a hydrocarbon radical having 1 to 8 carbon atoms, R 2 Is a hydrocarbon group having 3 to 8 carbon atoms. Although the above patent application discloses a process for the polymerization of two olefins without inert solvents, it does not relate to terpolymerization nor does it optimize the process conditions for the terpolymerization characteristics. Compared with binary copolymerization, the ternary copolymerization has more complex proportioning condition of different monomers, the property of a polymerization product is directly influenced by the insertion rate of different monomers in a polymer, and the insertion rate is directly influenced by different concentrations of the monomers; furthermore, the phase stability of solution polymerization is critical compared to other polymerization processes, such as gas phase and slurry processes, and both patent applications CN 114929763A and CN 111630071A disclose methods for maintaining the phase stability of solution polymerization in the presence of a solvent. The phase stability of the ternary solution polymerization reactor depends on the temperature (T), pressure (P) and composition (C) in the reactor, expressed as follows:
f(T,P,C)＝0
that is, at a certain temperature and pressure, in order to maintain phase stability, the composition thereof must be limited to a certain range; alternatively, the pressure must be limited to a certain range at a certain temperature and composition. The performance of polymerization catalysts is generally sensitive to temperature, i.e. the catalyst needs to be at a suitable temperature. For a ternary polymerization system, the reasonable reactor pressure and the mass ratio of three different monomers need to be determined to obtain polymer products with different properties under mild reaction conditions, i.e. lower pressure.
The invention provides a solution polymerization method for olefin ternary polymerization, which combines the above contents to polymerize ethylene and other two olefins respectively shown as formula CH in a reactor in the presence of a catalyst and in the absence of an inert solvent to obtain a ternary polymerized polymer 2 = CHA and formula CH 2 = CHB, wherein A and B are respectively hydrocarbon groups with 1-8 carbon atoms, the sum of the carbon numbers of A and B is not less than 5, the total mass fraction of the other two olefins in the polymer solution in the reactor is 75-90%, and the specific steps comprise:
a) Feeding a main catalyst, a cocatalyst, ethylene and the other two olefins into a reactor, carrying out polymerization reaction in the reactor, and discharging to obtain a polymer solution;
b) Feeding the polymer solution to a solution preheater to obtain a higher temperature polymer solution, which is fed to a separation and recovery unit; alternatively, the first and second electrodes may be,
feeding the polymer solution directly to a separation and recovery unit;
c) Separating the polymer solution entering the separation and recovery unit to obtain a polymer product and a recycle stream containing ethylene and the other two olefins;
the inlet of the reactor is provided with feed pipes for feeding into the reactor, including a main catalyst feed pipe, a cocatalyst feed pipe, an ethylene feed pipe and a comonomer feed pipe for feeding the other two olefins, and a recycle line for receiving a recycle stream from the separation and recovery unit, wherein the feed pipes and the recycle line are connected with the reactor separately or partially or totally combined into one feed pipe connected with the reactor.
In a preferred embodiment, the solution polymerization method for olefin terpolymerization is adopted, and the other two olefins are 1-butene and 1-hexene;
in order to achieve polymerization at pressures of less than 250bar and to obtain a polymer product with a mass insertion rate of 1-hexene of greater than 15%, the total mass fraction of 1-hexene in the polymer solution inside said reactor is not less than 5%, preferably greater than 20%, more preferably greater than 40%;
the total content of 1-butene and 1-hexene in the polymer product is from 10 to 50% by weight;
different from binary copolymerization products of ethylene and alpha olefin, in ternary copolymerization, products with different performances can be obtained by the different proportions of two monomers except ethylene; the content of 1-butene and 1-hexene in the polymer product is in the range of 0.1 to 10, preferably 0.2 to 5, more preferably 0.5 to 2.
In a preferred embodiment, in the method for the solution polymerization of olefin terpolymer, the other two olefins are 1-hexene and 1-octene;
in order to achieve polymerization at pressures lower than 70bar and to obtain a polymer product with a mass insertion rate of 1-octene higher than 15%, the total mass fraction of 1-octene in the polymer solution inside the reactor is not lower than 5%, preferably higher than 30%, more preferably higher than 45%;
the total content of 1-hexene and 1-octene in the polymer product is 10-50 wt%;
different from binary copolymerization products of ethylene and alpha olefin, in ternary copolymerization, products with different performances can be obtained by the different proportions of two monomers except ethylene; the content weight ratio of 1-hexene to 1-octene in the polymer product is from 0.1 to 10, preferably from 0.2 to 5, more preferably from 0.5 to 2.
In a preferred embodiment, in the method for the solution polymerization of the olefin terpolymer, the mass fraction of the polymer in the polymer solution in the reactor is 5 to 30%, preferably 10 to 20%.
In a preferred embodiment, the solution polymerization process for the terpolymerization of olefins is carried out at a temperature ranging from 80 to 180 ℃ and a pressure ranging from 30 to 200 bar.
The solution polymerization method for olefin terpolymerization, in the presence of the catalyst and in the absence of the inert solvent, includes the case of not having any inert solvent and the case of using a small amount of the inert solvent and/or diluent, which is inevitable for the need of the main catalyst and/or the co-catalyst.
The solution polymerization process for olefin terpolymerization may be continuous, batch, or semi-continuous.
In a preferred embodiment, the solution polymerization method for olefin terpolymer is a continuous operation, a kettle type reactor is connected with a tubular reactor in series, and the mass fraction of the generated polymer in the tubular reactor is more than 5 percent of the total generated polymer. The combination form of the double reactors can achieve the purposes of adjusting the productivity and controlling the yield by controlling the feed composition and the flow rate of the reactorsFor purposes of the product, e.g. the feed to the tank reactor does not contain CH of the formula 2 An olefin monomer of the formula CHA, a solution withdrawn from the tank reactor and make-up CH 2 The olefin monomer represented by CHA enters a tubular reactor to continue the polymerization reaction. Ethylene and the formula CH 2 The olefin monomer represented by = CHB generates binary polymer, ethylene and the formula CH in the tank reactor 2 = CHA and formula CH 2 The two olefin monomers indicated by = CHB produce a terpolymer within the tubular reactor.
The invention realizes the ternary polymerization of ethylene-1-butene-1-hexene and ethylene-1-hexene-1-octene in the absence of inert solvent for the first time, and the process which is lack of inert solvent and is adopted by the invention is superior to the process which is adopted by solvent aiming at the solution polymerization method of the ternary polymerization of ethylene-1-butene-1-hexene and ethylene-1-hexene-1-octene. As known in the art, ethylene, 1-butene, 1-hexene terpolymers, suitably using an alkane containing 5C as solvent, e.g. pentane C 5 H 14 Or 7C and more than 7C alkanes are used as solvents, the latter has higher polymer solubility, but the energy consumption in the solvent removal process is larger, and 6C alkanes are used as solvents to cause the separation of the solvents and hexene comonomers to be difficult; ethylene, 1-hexene, 1-octene terpolymers, suitably with a comonomer comprising 7 carbons, e.g. n-heptane C 7 H 16 Or 8C and more than 8 hydrocarbons are used as the solvent, and the latter has higher polymer dissolving performance, but the energy consumption of the solvent removal process is larger. The polymerization method without inert solvent avoids the step of separating solvent and comonomer in the separation section, simplifies the process steps and also reduces the energy consumption of devolatilization and separation; meanwhile, the invention adopts a single reactor or a plurality of reactors connected in series, and binary and/or ternary polymerization products can be obtained by polymerization in different reactors, thereby providing product performance and product diversity of the process.
By combining the technical scheme, the scheme of the invention has the following advantages: (1) the separation process is simplified and the energy consumption is reduced; and (2) multiple samples of the product of the process.
Drawings
FIG. 1 and FIG. 2 are schematic diagrams of a solution polymerization process of the present invention using ethylene-1-hexene-1-octene as an example.
Detailed Description
The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.
As shown in figure 1, the invention provides a solution polymerization method, taking copolymerization of ethylene, 1-hexene and 1-octene as an example, a polymerization device used in the method mainly comprises a reaction unit (1) and a separation and recovery unit (2), wherein the reaction unit is provided with a reactor and a feeding pipe, ethylene monomer, 1-hexene and 1-octene comonomer, a main catalyst and a cocatalyst can be combined into one feeding pipe to be connected with the reactor, and can also be connected with the reactor through an independent feeding pipeline, and the reaction unit is also provided with a circulating pipeline for receiving a circulating stream from the separation and recovery unit; and conveying the polymer solution obtained from the outlet of the reactor to a separation and recovery unit, and carrying out series operation on the mixed materials by the separation and recovery unit so as to separate, recover and circulate the materials to finally obtain a polymer product and a circulating stream. It is noted that the method proposed by the present invention is not limited to a single reactor process, but can also be used for a process in which two reactors are connected in series or a process in which more than two reactors are connected. As shown in fig. 2, the polymerization plant mainly comprises a reactor #1 (1), a reactor #2 (3), and a separation and recovery unit (2), wherein the reactor # 1 is provided with a feeding pipe, ethylene monomer, 1-hexene and 1-octene comonomer, main catalyst and cocatalyst can all be combined into one feeding pipe to be connected with the reactor, or can be connected with the reactor through a separate feeding pipeline, and the reactor # 1 is also provided with a circulating pipeline for receiving a circulating stream from the separation and recovery unit; an outlet of the reactor # 1 is connected with an inlet of the reactor # 2, and the first polymer solution obtained from the outlet of the reactor # 1 is mixed with a fresh and/or recycled ethylene monomer, 1-hexene and 1-octene comonomer mixed stream and then enters the reactor # 2 for reaction; the second polymer solution obtained from the outlet of reactor # 2 is sent to a separation and recovery unit which performs a series of operations on the mixed material to separate, recover and recycle the material, finally obtaining a polymer product and a recycle stream.
As is known in the art, a tank reactor is a cylindrical reactor with a low height-to-diameter ratio, and is usually provided with a single-layer or multi-layer stirring (e.g., mechanical stirring) device, a jacket can be arranged at the wall of the reactor, or a heat exchange surface can be arranged in the reactor, or heat exchange can be carried out through external circulation. The tubular reactor is a tubular continuous operation reactor with large length-diameter ratio, belonging to a plug flow reactor. The adiabatic reactor refers to a reactor that does not exchange heat with the outside, and the non-adiabatic reactor refers to a reactor that exchanges heat with the outside.
As known in the art, the polymerization catalyst may be any catalyst capable of copolymerizing ethylene, 1-hexene and 1-octene, including Z-N catalysts, metallocene catalysts, post-metallocene catalysts, such as those wherein the main catalyst is a Constrained Geometry Catalyst (CGC), the cocatalyst is Methylaluminoxane (MAO), and the like. It is also within the scope of the present invention to use inert solvents and/or diluents in systems where it is known in the art that co-feeding of the procatalyst and/or cocatalyst may be necessary, and in such cases small amounts of inert solvent and/or diluent may be unavoidable.
The process of the invention may employ one or more stirred tank reactors or tubular reactors, the tubular reactor being a reactor comprising a static mixer, the reactors being adiabatic and non-adiabatic reactors.
As is known in the art, the polymerization of olefins may take place in the absence of a polymerization inert solvent, patent application CN 114630844A providing a process for reacting a compound of formula CH in the absence of an inert solvent 2 ＝CHR 1 A first olefin of the formula 2 ＝CHR 2 A second olefin polymerization shown, wherein R 1 Is hydrogen or a hydrocarbon radical having 1 to 8 carbon atoms, R 2 Is a hydrocarbon group having 3 to 8 carbon atoms. Although the above patent application discloses a process for the polymerization of two olefins without an inert solvent, it does not relate toThe ternary polymerization also does not aim at the characteristics of the ternary polymerization and optimizes the operation conditions of the process. According to the method provided by the invention, an ethylene monomer, a 1-hexene and 1-octene comonomer, or an ethylene monomer, a 1-butene and 1-hexene comonomer are subjected to a polymerization reaction under the action of a main catalyst and a cocatalyst to obtain a polymer, wherein the polymer is a terpolymer obtained by copolymerizing ethylene, 1-hexene and 1-octene, or ethylene, 1-butene and 1-hexene. The method realizes the purposes that (1) the ternary polymerization solution process can be carried out at lower reaction pressure, (2) the proportion of the components of the comonomer in the reactor can realize the diversification of products, and (3) the solution polymerization method without inert solvent realizes the simplification of the recovery and separation processes by optimizing the material composition in the reactor.
As is known in the art, polymer molecular weight can be reduced by adding small amounts of a substance having a large chain transfer constant, and suitable chain transfer agents are many, such as hydrogen, which can optionally be used in solution polymerization to control the molecular weight of the polymer.
It is known in the art that after obtaining a polymer solution, unreacted monomer, comonomer, hydrogen, and solvent (if present) and other impurity components introduced from the feedstock are removed by a separation and recovery unit to obtain a polymer product. Unreacted monomer, comonomer and solvent (if present) may be recycled via recycle lines.
As known in the art, a "separation and recovery unit" is a system comprising a plurality of recovery and separation operations, and the recovery and separation unit of an olefin solution polymerization process usually comprises a plurality of stages of flash evaporation, devolatilization, rectification separation and the like. For example, patent CN 106414509B and patent CN 108602900B disclose solvent and monomer recovery processes using multi-stage gas-liquid phase separation. "flash separation" is a common method for gas-liquid phase separation, and means a separation step by pressure reduction resulting in phase separation, patent CN 109715675B discloses a method for separating hydrocarbon compounds from polymer solution by using a flash separator, and patent CN 108779194B discloses a method for separating polymer solution which can reduce entrainment of polymer in gas phase by flash separation.
It is known in the art that the recovery and separation of the polymer solution generally requires high temperatures of around 150-220 c, and the heating of the polymer solution is achieved by means of a solution preheater arranged between the reactor outlet and the inlet of the separation system.
It is known in the art that the catalyst, when leaving the polymerization reactor, is generally still active, and that it is necessary to deactivate the catalyst before the polymer solution is subjected to downstream recovery and separation units, avoiding further uncontrolled polymerization or thermal degradation of the polymer during the separation step. As known in the art, injection of a deactivating agent is a method of deactivating the catalyst, such as water, sodium stearate; the catalyst can also be deactivated by increasing the temperature, as in patent TW 202134297A.
The examples and comparative examples used the same procatalyst and cocatalyst and the same procedure, differing primarily in that the comparative example used an inert solvent (n-heptane or n-pentane), whereas the examples did not use an inert solvent, in different examples the feed ratios of 1-hexene to 1-octene were not consistent, and the feed ratios of 1-butene to 1-hexene were not consistent to produce different products. The method of the present invention will be described below by taking examples and comparative examples as examples.
Example 1
According to the method, a single adiabatic kettle type reactor is adopted, a stirring part is arranged in the reactor, the reaction pressure is 57.5bar, and the retention time is 8min; CGC is selected as a main catalyst, MAO is selected as an auxiliary catalyst, hydrogen is selected as a molecular weight regulator, and water is selected as an inactivating agent; the feed composition was as follows: feeding 90.57kg/h of ethylene monomer, 45.75kg/h of 1-hexene and 530.3kg/h of 1-octene, adding 0.0019kg/h of main catalyst and 0.019kg/h of cocatalyst, and introducing 0.01kg/h of hydrogen; the feeding components are completely mixed to form a stream, then the stream is subjected to heat exchange to-5 ℃ and fed into a kettle type reactor, and the outlet temperature of the kettle type reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5wt% of ethylene, 5wt% of 1-hexene, 75wt% of 1-octene and 15wt% of polymer; the separation system adopts a three-stage flash mode, the first stage is medium-pressure flash, a flash tank is provided with 16bar, and the polymer solution is heated to 200 ℃ through a solution preheater before entering the first-stage flash; the second stage is low-pressure flash evaporation, the flash evaporation tank is provided with 3bar, and the separation temperature is 190 ℃; the third stage is also low-pressure flash evaporation, the flash evaporation tank is set at 1bar, and the separation temperature is 190 ℃; the first stage flash vapor phase is cooled to 40 ℃ by a heat exchanger and then directly recycled to the reaction unit, and the second stage flash vapor phase and the third stage flash vapor phase are conveyed to a downstream rectification separation unit after passing through a heat recovery unit so as to separate part of components.
Example 2
The polymerization was carried out as in example 1, with the difference that the reactor feed composition was as follows: feeding 92.62kg/h of ethylene monomer, 523.57kg/h of 1-hexene and 50.47kg/h of 1-octene into the reactor, adding 0.0020kg/h of main catalyst and 0.020kg/h of cocatalyst, and feeding 0.013kg/h of hydrogen; the feeding components are completely mixed to form a stream, then the stream is subjected to heat exchange to-10 ℃ and fed into a kettle type reactor, and the outlet temperature of the kettle type reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5% by weight of ethylene, 75% by weight of 1-hexene, 5% by weight of 1-octene, 15% by weight of polymer and the rest in the same manner as in example 1.
Example 3
The polymerization was carried out as in example 1, with the difference that the reactor feed composition was as follows: 89.50kg/h of ethylene monomer, 189.77kg/h of 1-hexene and 387.40kg/h of 1-octene are fed, 0.0020kg/h of main catalyst and 0.02kg/h of cocatalyst are added, and 0.015kg/h of hydrogen is introduced; the feeding components are completely mixed to form a stream, then the stream is subjected to heat exchange to-5 ℃ and fed into a kettle type reactor, and the outlet temperature of the kettle type reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5% by weight of ethylene, 26% by weight of 1-hexene, 54% by weight of 1-octene, 15% by weight of polymer and the rest in the same manner as in example 1.
Comparative example 1
The polymerization was carried out as in example 1, with the difference that the reactor feed composition was as follows: feeding 96.57kg/h of ethylene monomer, 46.57kg/h of 1-hexene, 56.86kg/h of 1-octene and 466.67kg/h of solvent n-heptane, adding 0.0024kg/h of main catalyst and 0.024kg/h of cocatalyst, and feeding 0.012kg/h of hydrogen; the feeding components are completely mixed to form a stream, then the stream is subjected to heat exchange to-10 ℃ and fed into a kettle type reactor, and the outlet temperature of the kettle type reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5wt% of ethylene, 5wt% of 1-hexene, 5wt% of 1-octene, 70% of n-heptane, 15wt% of polymer and the rest of the procedure was the same as in example 1.
The polymerization process conditions and key index comparisons for example 1, example 2, example 3 and comparative example 1 are shown in table 1, with the reaction pressures determined based on the bubble point pressure of the polymer solution at the exit of the solution preheater, where higher bubble point pressures result in higher reactor pressures. As is apparent from the results shown in Table 1, example 1 can achieve a lower polymer pressure without using an inert solvent, while the energy consumption of the recovery section, i.e., the devolatilization energy consumption, is similar to that of comparative example 1 using n-heptane as a solvent. Compared with example 1, example 2 has higher bubble point pressure of the polymer solution at the outlet of the solution preheater than that of comparative example 1 at higher mass fraction of 1-hexene and lower mass fraction of 1-octene, but has lower energy consumption of the recovery section. Based on example 2, example 3 has the same bubble point pressure of the polymer solution at the outlet of the solution preheater as that of comparative example 1 and has lower energy consumption of the recovery section, while decreasing the mass fraction of 1-hexene in the reactor and increasing the mass fraction of 1-octene in the reactor. Example 1, example 2 and example 3 did not incorporate an inert solvent and therefore no separation equipment, such as a rectification column, for the solvent and comonomer was required in the separation section. As is known in the art, fractionation by rectification is generally a plant with high investment costs and high operating costs (high energy consumption). In addition, examples 1, 2 and 3 can achieve terpolymerization of different comonomer insertion rates by adjusting the feeding amount of 1-hexene and 1-octene.
TABLE 1 polymerization Process conditions and Key index comparison
Example 4
According to the method, a single adiabatic kettle type reactor is adopted, a stirring part is arranged in the reactor, the reaction pressure is 165bar, and the retention time is 10min; CGC is selected as a main catalyst, MAO is selected as an auxiliary catalyst, hydrogen is selected as a molecular weight regulator, and water is selected as an inactivating agent; the feed composition was as follows: feeding 91.5kg/h of ethylene monomer, 148.3kg/h of 1-butene and 426.7kg/h of 1-hexene, adding 0.0021kg/h of main catalyst and 0.021kg/h of cocatalyst, and introducing 0.011kg/h of hydrogen; the feeding components are completely mixed to form a stream, then the stream is subjected to heat exchange to-14 ℃ and fed into a kettle type reactor, and the outlet temperature of the kettle type reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5wt% of ethylene, 20wt% of 1-butene, 60wt% of 1-hexene and 15wt% of polymer; the separation system adopts a three-stage flash mode, the first stage is medium-pressure flash, a flash tank is provided with 16bar, and the polymer solution is heated to 200 ℃ through a solution preheater before entering the first-stage flash; the second stage is low-pressure flash evaporation, the flash evaporation tank is provided with 3bar, and the separation temperature is 190 ℃; the third stage is also low-pressure flash evaporation, the flash evaporation tank is provided with 1bar, and the separation temperature is 190 ℃; the first stage flash vapor phase is cooled to 40 ℃ by a heat exchanger and then directly recycled to the reaction unit, and the second stage flash vapor phase and the third stage flash vapor phase are conveyed to a downstream rectification separation unit after passing through a heat recovery unit so as to separate part of components.
Example 5
The polymerization was carried out as in example 4, with the difference that the reactor feed composition was as follows: feeding 88.0kg/h of ethylene monomer, 281.5kg/h of 1-butene and 291.8kg/h of 1-hexene, adding 0.0020kg/h of main catalyst and 0.020kg/h of cocatalyst, and introducing 0.012kg/h of hydrogen; after all the feeding components are mixed into one stream, exchanging heat to-19 ℃, and feeding the stream into a kettle reactor, wherein the outlet temperature of the kettle reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5% by weight of ethylene, 39% by weight of 1-butene, 41% by weight of 1-hexene, 15% by weight of polymer and the rest in the same manner as in example 1.
Example 6
The polymerization was carried out as in example 4, with the difference that the reactor feed composition was as follows: feeding 92.4kg/h of ethylene monomer, 218.2kg/h of 1-butene and 356.1kg/h of 1-hexene, adding 0.0020kg/h of main catalyst and 0.02kg/h of cocatalyst, and introducing 0.013kg/h of hydrogen; the feeding components are completely mixed to form a stream, then the stream is subjected to heat exchange to 12.5 ℃ and fed into a kettle type reactor, and the outlet temperature of the kettle type reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5wt% of ethylene, 30wt% of 1-butene, 50wt% of 1-hexene, and 15wt% of a polymer, and the remaining steps were the same as in example 1.
Comparative example 2
The polymerization was carried out as in example 4, with the difference that the reactor feed composition was as follows: 94.8kg/h of ethylene monomer feed, 48.7kg/h of 1-butene feed, 56.4kg/h of 1-hexene feed and 466.7kg/h of n-pentane solvent, 0.0025kg/h of main catalyst and 0.025kg/h of cocatalyst are added, and 0.012kg/h of hydrogen is introduced; the feeding components are completely mixed to form a stream, then the stream is subjected to heat exchange to-10 ℃ and fed into a kettle type reactor, and the outlet temperature of the kettle type reactor is 150 ℃; the polymerization conditions (reactor contents) were as follows: 5% by weight of ethylene, 5% by weight of 1-butene, 5% by weight of 1-hexene, 70% by weight of n-pentane and 15% by weight of polymer, the rest being the same as in example 1.
The polymerization process conditions and key index comparisons for example 4, example 5, example 6 and comparative example 2 are shown in table 2, with the reaction pressures determined based on the bubble point pressure of the polymer solution at the exit of the solution preheater, where higher bubble point pressures result in higher reactor pressures. As is apparent from the results shown in Table 2, example 4 can achieve a lower polymer pressure without using an inert solvent, while the energy consumption of the recovery section, i.e., the devolatilization energy consumption, is similar to that of comparative example 2 using n-pentane as a solvent. Compared with example 4, example 5 has lower energy consumption of the recovery section at lower 1-hexene and higher 1-butene mass fraction, and the bubble point pressure of the polymer solution at the outlet of the solution preheater is equal to that of comparative example 2. On the basis of example 5, example 6 also has a lower bubble point pressure of the polymer solution at the outlet of the solution preheater than that of comparative example 2 at a reduced mass fraction of 1-butene in the reactor and an increased mass fraction of 1-hexene in the reactor. Example 4, example 5 and example 6 did not incorporate an inert solvent and therefore no separation equipment, such as a rectification column, for the solvent and comonomer at the separation section was required. As is known in the art, fractionation by rectification is generally a plant with high investment costs and high operating costs (high energy consumption). In addition, examples 4, 5 and 6 can achieve terpolymerization of different comonomer insertion rates by adjusting the 1-butene and 1-hexene feeding amounts.
It is to be noted that if the alkane having a higher number of carbon-containing elements is used as the solvent in comparative example 1 and comparative example 2, although the reaction pressure can be reduced, the devolatilization is more difficult and it is also necessary to provide a device for separating the solvent and the comonomer. Alternatively, based on the process of the present invention, there are also methods that can reduce the reactor pressure by increasing the mass fraction of the comonomer in the polymerization reactor in solution polymerization using an inert solvent, but separation of the inert solvent and the comonomer cannot be avoided, and still requires high capital investment for separation equipment and energy consumption. In summary, the method of the invention is more advantageous.
TABLE 2 polymerization Process conditions and Key index comparison
Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.
Claims (8)
1. A solution polymerization process for the terpolymerization of olefins, characterized in that ethylene and two other olefins, respectively of formula CH, are polymerized in a reactor in the presence of a catalyst and in the absence of an inert solvent to obtain a terpolymerized polymer 2 = CHA and formula CH 2 = CHB, wherein A and B are respectively hydrocarbon groups with 1-8 carbon atoms, the sum of the carbon numbers of A and B is not less than 5, the total mass fraction of the other two olefins in the polymer solution in the reactor is 75-90%, and the concrete steps comprise:
a) Feeding a main catalyst, a cocatalyst, ethylene and the other two olefins into a reactor, carrying out polymerization reaction in the reactor, and discharging to obtain a polymer solution;
b) Feeding the polymer solution to a solution preheater to obtain a higher temperature polymer solution, which is fed to a separation and recovery unit; alternatively, the first and second electrodes may be,
feeding the polymer solution directly to a separation and recovery unit;
c) Separating the polymer solution entering the separation and recovery unit to obtain a polymer product and a recycle stream containing ethylene and the other two olefins;
the inlet of the reactor is provided with feed pipes for feeding into the reactor, including a main catalyst feed pipe, a cocatalyst feed pipe, an ethylene feed pipe and a comonomer feed pipe for feeding the other two olefins, and a recycle line for receiving a recycle stream from the separation and recovery unit, wherein the feed pipes and the recycle line are connected with the reactor separately or partially or totally combined into one feed pipe connected with the reactor.
2. The solution polymerization process for the terpolymerization of olefins according to claim 1, characterized in that said other two olefins are 1-butene and 1-hexene;
the total mass fraction of 1-hexene in the polymer solution inside the reactor is not less than 5%, preferably greater than 20%, more preferably greater than 40%;
the total content of 1-butene and 1-hexene in the polymer product is from 10 to 50% by weight;
the content of 1-butene and 1-hexene in the polymer product is in the range of 0.1 to 10, preferably 0.2 to 5, more preferably 0.5 to 2.
3. The solution polymerization process for the terpolymerization of olefins according to claim 1, characterized in that said other two olefins are 1-hexene and 1-octene;
the total mass fraction of 1-octene in the polymer solution inside the reactor is not less than 5%, preferably greater than 30%, more preferably greater than 45%;
the total content of 1-hexene and 1-octene in the polymer product is 10-50 wt%;
the content weight ratio of 1-hexene to 1-octene in the polymer product is from 0.1 to 10, preferably from 0.2 to 5, more preferably from 0.5 to 2.
4. The method for the solution polymerization of olefin terpolymers according to claim 1, characterized in that the mass fraction of polymer in the polymer solution inside the reactor is between 5 and 30%, preferably between 10 and 20%.
5. The solution polymerization process of an olefin terpolymer according to claim 1, characterized in that the polymerization reaction is operated at a temperature in the range of 80-180 ℃ and a pressure in the range of 30-200 bar.
6. The method for solution polymerization of olefin terpolymerization of claim 1, wherein said case where the catalyst is present and the inert solvent is absent comprises the case where there is no inert solvent and the case where a small amount of inert solvent and/or diluent is inevitably used in order to meet the needs of the main catalyst and/or the co-catalyst.
7. The method of claim 1, wherein the solution polymerization process is a continuous, batch, or semi-continuous process.
8. The method of claim 7, wherein the solution polymerization process is a continuous process using a tank reactor in series with a tubular reactor, and the mass fraction of polymer produced in the tubular reactor is greater than 5% of the total polymer produced.
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