Polyolefin preparation method and device

Abstract

The invention provides a polyolefin preparation method and device. The process device mainly comprises a plurality of stirring reaction kettles connected in series, a gas-liquid separator, a gas compressor, a circulating pump and an external circulation loop heat exchanger. Wherein the stirring reaction kettle can be used for removing heat in a manner of externally arranging a cooling jacket, evaporating a liquid phase and condensing and circulating back to the reaction kettle. According to the invention, solvents of different types and proportions are respectively added according to the mass fraction distribution range characteristics of polyolefin products in the stirring reaction kettles connected in series, so that heat is removed mainly through evaporation of the first inert solvent in the stirring reaction kettles with low polyolefin mass fraction; heat transfer is mainly carried out through evaporation of monomers and hexane in a stirring reaction kettle with high polyolefin mass fraction. Besides, a certain amount of nano-scale graphene particles are added into the stirring reaction kettle with high polyolefin mass fraction so as to strengthen the transmission and mixing effects of a polymerization system, and the preparation method can be used for safely and efficiently preparing polyolefin.

Description

Technical Field

[0001] This invention relates to a method and apparatus for preparing polyolefins, belonging to the field of organic synthesis technology. Background Technology

[0002] Polyethylene is a thermoplastic resin obtained by polymerizing ethylene. Industrially, it also includes copolymers of ethylene and small amounts of α-olefins. Polyethylene has excellent low-temperature resistance, good chemical stability, and can withstand the corrosion of most acids and alkalis. Therefore, it has a wide range of applications, mainly used to manufacture films, packaging materials, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can also be used as a high-frequency insulating material for televisions, radar, etc.

[0003] Solution polymerization is commonly used in the preparation of high-end polyolefins, such as polyolefin elastomers and ultra-high molecular weight drag reducers. In solution polymerization, the polyolefin product dissolves in a liquid mixture. As the mass fraction of polyolefin increases, the viscosity of the reaction mixture gradually increases, leading to a sharp decline in the mixing and transfer efficiency of the polymerization system. This, in turn, limits the precise control of product properties at high polyolefin mass fractions, making it difficult to guarantee process safety. Therefore, the mass fraction of polyolefin in the stirred tank of current solution polymerization processes is generally low, making it difficult to achieve efficient polyolefin production.

[0004] Patent document CN202110470160.2 reports the removal of heat by injecting a certain amount of low-boiling-point inert solvent into the polymerization reactor, mainly utilizing the evaporation and cooling of the low-boiling-point inert solvent; patent document CN110918018A reports the removal of polymerization heat in a polyethylene reactor by solvent evaporation; patent document 202210945593.3 reports the removal of heat by first feeding the reaction mixture from the reactor outlet into a flash tank for flash evaporation, cooling the evaporated light component monomer and solvent, and then recycling them back to the reactor.

[0005] However, when the mass fraction of polyolefins in the reactor is high (greater than 20%), the existing methods can effectively remove the heat of reaction, but the yield of polyolefins is low, the product properties are difficult to control, and the safety of the process cannot be guaranteed.

[0006] Therefore, there is an urgent need to explore efficient polyolefin production methods to meet market demands. Summary of the Invention

[0007] This invention provides a method for preparing polyolefins, which can safely and efficiently prepare polyolefins.

[0008] The present invention also provides an apparatus for preparing polyolefins, which can be used to perform the above-described preparation method to obtain polyolefins.

[0009] This invention provides a method for preparing polyolefins, employing a reaction apparatus comprising N reaction units connected in series, where N≥2. The method includes the following steps:

[0010] A mixture of raw materials, including olefin monomers, comonomers, catalysts, and C5-C9 alkane solvents, undergoes polymerization in the previous reaction unit and then flows sequentially into the next reaction unit to continue the polymerization reaction, and the polyolefin is extracted from at least the Nth reaction unit; during the polymerization reaction, the gas phase escaping from the reaction system is removed from the reaction unit;

[0011] Where N is an even number, the polymerization process further includes inputting a first inert solvent into the preceding N / 2 reaction units and inputting a second inert solvent into the following N / 2 reaction units; or, N is an odd number, the polymerization process further includes inputting a first inert solvent into the preceding (N-1) / 2 reaction units, inputting a second inert solvent into the following (N-1) / 2 reaction units, and inputting a first inert solvent and a second inert solvent into the following (N+1) / 2 reaction units.

[0012] In the preparation method described above, the boiling point of the first inert solvent is not higher than 80°C, and the boiling point of the second inert solvent is not lower than 160°C.

[0013] In the preparation method described above, N is 3-5.

[0014] In the preparation method described above, the boiling point of the first inert solvent is 10-75℃;

[0015] And / or, the boiling point of the second inert solvent is 160-250°C.

[0016] In the preparation method described above, the first inert solvent is a C3-C5 alkane;

[0017] And / or, the second inert solvent is a C15-C18 alkane.

[0018] In the preparation method described above, N is an even number, and the polymerization reaction further includes inputting graphene particles into the next N / 2 reaction units respectively; or, N is an odd number, and the polymerization reaction further includes inputting graphene particles into the (N+1) / 2th reaction unit and the next (N-1) / 2th reaction units respectively.

[0019] In the preparation method described above, the equivalent particle size of the graphene particles is 50-200 nm.

[0020] In the preparation method described above, in each reaction unit, the first inert solvent accounts for 5-25% of the mass percentage of the reaction system;

[0021] And / or, in each reaction unit, the C5-C9 alkane solvent accounts for 20-40% of the mass percentage of the reaction system;

[0022] And / or, in each reaction unit, the second inert solvent accounts for 10-30% of the mass percentage of the reaction system.

[0023] The preparation method described above further includes: subjecting the escaped gas phase to cooling-gas-liquid separation treatment to obtain condensate and separated gas phase; circulating at least a portion of the condensate into each of the reaction units to participate in the polymerization reaction, and circulating at least a portion of the separated gas phase into the first reaction unit to participate in the polymerization reaction.

[0024] In another aspect, the present invention provides an apparatus for preparing polyolefins, the apparatus being used to perform the preparation method described above, the apparatus comprising N reaction units connected end-to-end, where N≥2;

[0025] Wherein, when N is an even number, the first N / 2 reaction units each include a first inert solvent inlet and a gas phase outlet; the last N / 2 reaction units each include a second inert solvent inlet and a gas phase outlet;

[0026] Alternatively, if N is an odd number, the first (N-1) / 2 reaction units each include a first inert solvent inlet and a gas phase outlet, the next (N-1) / 2 reaction units each include a second inert solvent inlet and a gas phase outlet, and the (N+1) / 2 reaction unit includes a first inert solvent inlet, a second inert solvent inlet, and a gas phase outlet.

[0027] The apparatus described above further includes N cooling-gas-liquid separation processing units, which are connected to the reaction units in a one-to-one correspondence; the reaction units also include condensate inlets, and the first reaction unit also includes compressed gas inlets;

[0028] Each cooling-gas-liquid separation processing unit includes a cooling device, a separation device, and a compression device;

[0029] The cooling device includes a gas phase inlet and a cooling gas phase outlet; the separation device includes a cooling gas phase inlet, a separated gas phase outlet, and a condensate outlet; the compression device includes a separated gas phase inlet and a compressed gas outlet; the cooling gas phase outlet and the cooling gas phase inlet are connected, and the separated gas phase outlet and the separated gas phase inlet are connected.

[0030] Among them, N gas phase outlets and N gas phase feed ports are connected in a one-to-one correspondence, N compressed gas outlets and the compressed gas feed port of the first reaction unit are respectively connected, and N condensate outlets and N condensate feed ports are connected in a one-to-one correspondence.

[0031] The preparation method provided by this invention can safely and efficiently prepare polyolefins. According to the characteristics of the mass fraction distribution range of polyolefin products in the series reaction units, different types of solvents are added respectively to achieve the following: in the stirred reactor with low polyolefin mass fraction, heat transfer is mainly carried out by the evaporation of the first inert solvent; in the stirred reactor with high polyolefin mass fraction, heat transfer is mainly carried out by the evaporation of monomer and hexane. Attached Figure Description

[0032] Figure 1 These are schematic diagrams of the process apparatus provided in Embodiments 1-10 and Comparative Examples 1 and 2 of the present invention;

[0033] Figure 2 This is a schematic diagram of the process apparatus provided in Embodiment 11 of the present invention;

[0034] Figure 3 This is a schematic diagram of the process apparatus provided in Embodiment 12 of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] C1 - First gas compressor; C2 - Second gas compressor; C3 - Third gas compressor; E1 - First cooler; E2 - Second cooler; E3 - Third cooler; E4 - Fourth cooler; E5 - Fifth cooler; F1 - Raw material inlet; F2 - First inert solvent inlet; F3 - Second inert solvent inlet; F4 - Graphene particle inlet; G1 - First gas-liquid separator; G2 - Second gas-liquid separator; G3 - Third gas-liquid separator; G4 - Fourth gas-liquid separator; G5 - Fifth gas-liquid separator; L1 - First material conveyor Pumps; L2, second material conveying pump; L3, third material conveying pump; L4, fourth material conveying pump; L5, fifth material conveying pump; P1, discharge stream from the first reactor; P2, discharge stream from the second reactor; P3, discharge stream from the third reactor; P4, discharge stream from the fourth reactor; P5, discharge stream from the fifth reactor; R1, first reactor; R2, second reactor; R3, third reactor; R4, fourth reactor; R5, fifth reactor; S1, first feed separator; S2, second feed separator; S3, third feed separator. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] This invention provides a method for preparing polyolefins, employing a reaction apparatus comprising N reaction units connected in series, where N≥2. The method includes the following steps: a mixture of olefin monomers, comonomers, catalysts, and C5-C9 alkane solvents undergoes polymerization in the previous reaction unit, and then flows sequentially into the next reaction unit to continue polymerization, with polyolefins being extracted from at least the Nth reaction unit; during the polymerization process, the gas phase escaping from the reaction system is removed from the reaction unit; wherein, if N is an even number, the polymerization process further includes introducing a first inert solvent into the preceding N / 2 reaction units and a second inert solvent into the following N / 2 reaction units; or, if N is an odd number, the polymerization process further includes introducing a first inert solvent into the preceding (N-1) / 2 reaction units, a second inert solvent into the following (N-1) / 2 reaction units, and a first inert solvent and a second inert solvent into the following (N+1) / 2 reaction units.

[0039] In detail, a mixture of raw materials, including olefin monomers, comonomers, catalysts, and C5-C9 alkane solvents, is fed into the first reaction unit for polymerization. The gas phase escaping from the reaction system leaves the reaction unit, while the liquid mixture flows into the next reaction unit to continue the polymerization reaction. During polymerization in the next reaction unit, the gas phase will still escape from the reaction system, leaving the reaction unit, while the liquid mixture continues to flow into the next reaction unit to continue the polymerization reaction.

[0040] The escaping gas phase mainly includes olefin monomers, comonomers, and solvents.

[0041] This invention does not limit the specific type of olefin monomer, and a suitable olefin monomer can be selected according to the specific type of the final polyolefin product. For example, the olefin monomer is selected from one or more C2-C6 olefins.

[0042] The present invention does not limit the specific type of comonomer. For example, the comonomer includes, but is not limited to, at least one of C3-C10 olefins.

[0043] Commonly used polymerization catalysts in the art can be selected, for example, at least one of Ziegler-Natta catalysts, metallocene catalysts and Phillips catalysts.

[0044] The present invention does not limit the reaction parameters of each reaction unit, and the reaction parameters of the conventional solvent method for preparing polyolefins in the art can be selected.

[0045] In one specific embodiment, the temperature of each reaction unit of the present invention is 100-160°C, and the pressure of each reaction unit is 2.0-6.0 MPa.

[0046] When the number of reaction units N is even, the first inert solvent is input into the first N / 2 reaction units and the second inert solvent is input into the next N / 2 reaction units.

[0047] In one specific embodiment, N=4, a first inert solvent is introduced into the first reaction unit and the second reaction unit respectively, and a second inert solvent is introduced into the second reaction unit and the third reaction unit respectively.

[0048] When the number of reaction units N is odd, the first inert solvent is introduced into the first (N-1) / 2 reaction units, the second inert solvent is introduced into the next (N-1) / 2 reaction units, and the first inert solvent and the second inert solvent are introduced into the (N+1) / 2 reaction units.

[0049] In one specific embodiment, N=5, a first inert solvent is introduced into the first reaction unit and the second reaction unit respectively, a first inert solvent and a second inert solvent are introduced into the third reaction unit, and a second inert solvent is introduced into the fourth reaction unit and the fifth reaction unit respectively.

[0050] The first inert solvent and the second inert solvent used in this invention refer to solvents that do not participate in the polymerization reaction and will not react with the raw materials or products of the polymerization reaction to generate by-products. The boiling points of the first inert solvent and the second inert solvent are different, wherein the boiling point of the first inert solvent is lower than that of the second inert solvent.

[0051] The preparation method provided by this invention can significantly improve the production efficiency and comonomer content of polyolefins, and reduce the polyolefin dispersion index. The inventors analyzed this and believe the reason may be that by adding different types of inert solvents in different reaction units, not only can the low boiling point of the first inert solvent be utilized to effectively remove heat through evaporation when the mass fraction of polyolefins in the reaction unit is low, but the second inert solvent can be used to make the concentration distribution of the mixed system in the reaction unit more uniform when the mass fraction of polyolefins in the reaction unit is high, reducing the number of bubbles, improving heat transfer efficiency, and thus improving the production efficiency and comonomer content of polyolefins, and reducing the polyolefin dispersion index.

[0052] Furthermore, in one specific embodiment of the present invention, the boiling point of the first inert solvent is not higher than 80°C, and the boiling point of the second inert solvent is not lower than 160°C.

[0053] The boiling points of the first inert solvent and the second inert solvent mentioned in this invention refer to the boiling points under standard atmospheric pressure, which can be obtained by differential scanning calorimetry.

[0054] When the boiling points of the first inert solvent and the second inert solvent are within the above-mentioned ranges, they can better play their roles at different stages and improve the production efficiency of polyolefins.

[0055] Furthermore, in one specific embodiment of the present invention, N is 3-5.

[0056] Specifically, the number of reaction units N can be any of 3, 4, or 5.

[0057] In one specific embodiment, N is 3, and a polymerization reaction is carried out using a reaction apparatus comprising three reaction units connected in series. Specifically, a mixed raw material including olefin monomers, comonomers, catalysts, and C5-C9 alkane solvents is fed into the first reaction unit, along with a first inert solvent. In the first reaction unit, polymerization occurs between the raw materials, yielding a liquid mixture and a gas phase, with the gas phase escaping from the first reaction unit. The liquid mixture flows into the second reaction unit, where a first inert solvent and a second inert solvent are introduced. In the second reaction unit, polymerization continues between the raw materials, yielding a liquid mixture and a gas phase, with the gas phase escaping from the second reaction unit. The liquid mixture continues to flow into the third reaction unit, where a second inert solvent is introduced. In the third reaction unit, polymerization continues between the raw materials, yielding a polyolefin product and a gas phase, with the gas phase escaping from the third reaction unit.

[0058] When polymerization is carried out with 3-5 reaction units, the production efficiency of polyolefins and the content of comonomers can be further improved, and the polyolefin dispersion coefficient can be reduced. This is because each reaction unit can independently optimize reaction conditions, extend the total reaction time, increase the reaction conversion rate, enhance the control of polymer properties, reduce the occurrence of side reactions, and effectively reduce the polyolefin dispersion coefficient through segmented control. These combined advantages make the production of polyolefins more efficient, uniform, and of higher quality.

[0059] Furthermore, in one specific embodiment of the present invention, the boiling point of the first inert solvent is 10-75°C; and / or, the boiling point of the second inert solvent is 160-250°C.

[0060] In detail, the boiling point of the first inert solvent includes, but is not limited to, a range of 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 75°C, or any two of these.

[0061] The boiling point of the second inert solvent includes, but is not limited to, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or any combination thereof.

[0062] When the boiling points of the first inert solvent and / or the second inert solvent are within the above range, the synergistic effect of the first inert solvent and / or the second inert solvent can be better utilized in different reaction units, further improving the production efficiency of polyolefins and the content of comonomers, and significantly reducing the polyolefin dispersion coefficient.

[0063] Furthermore, in one specific embodiment of the present invention, the first inert solvent is a C3-C5 alkane; and / or, the second inert solvent is a C15-C18 alkane.

[0064] Specifically, the first inert solvent includes at least one of propane, butane, and pentane.

[0065] The second inert solvent includes at least one of pentadecane, hexadecane, heptadecanane, and octadecane.

[0066] When the first inert solvent and / or the second inert solvent meet the above-mentioned type, they have more suitable boiling points and structures, which are more beneficial for heat transfer and homogenization of the reaction system.

[0067] Furthermore, in a specific embodiment of the present invention, N is an even number, and the polymerization reaction further includes inputting graphene particles into the next N / 2 reaction units respectively; or, N is an odd number, and the polymerization reaction further includes inputting graphene particles into the (N+1) / 2th reaction unit and the next (N-1) / 2th reaction units respectively.

[0068] For example, when N=4, graphene particles are input into the third and fourth reaction units respectively. Similarly, when N=5, graphene particles are input into the third, fourth, and fifth reaction units respectively.

[0069] When graphene particles are introduced into the reaction unit, the content of comonomers can be significantly increased, the dispersibility index of polyolefins can be reduced, and the production efficiency of polyolefins can be improved to a certain extent. This is because graphene has excellent thermal conductivity. Introducing graphene into the reaction unit can more effectively disperse and dissipate heat, avoiding uneven concentration gradient distribution of the liquid mixture due to gas phase escape.

[0070] Furthermore, in one specific embodiment of the present invention, the equivalent particle size of the graphene particles is 50-200 nm.

[0071] In this invention, the equivalent particle size of graphene particles refers to the average particle size of the graphene particles. The equivalent particle size of graphene particles can be measured using common methods such as transmission electron microscopy and specific surface area measurement.

[0072] In detail, the equivalent particle size of graphene particles includes, but is not limited to, a range of 50 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, or any combination thereof.

[0073] When the equivalent particle size of graphene particles is within the above range, the production efficiency of polyolefins can be further improved. This may be because graphene particles within the above particle size range have a better effect on enhancing the transfer and mixing of the reaction system.

[0074] Furthermore, in one specific embodiment of the present invention, in each reaction unit, the first inert solvent accounts for 5-25% of the mass percentage of the reaction system; and / or, in each reaction unit, the C5-C9 alkane solvent accounts for 20-40% of the mass percentage of the reaction system; and / or, in each reaction unit, the second inert solvent accounts for 10-30% of the mass percentage of the reaction system.

[0075] Specifically, the mass percentage of the first inert solvent in each reaction unit is, but is not limited to, 5%, 10%, 15%, 20%, 25%, or any combination thereof; and / or, the mass percentage of the C5-C9 alkane solvent in each reaction unit is, but is not limited to, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, or any combination thereof; and / or, the mass percentage of the second inert solvent in each reaction unit is, but is not limited to, 10%, 15%, 20%, 25%, 30%, or any combination thereof.

[0076] It is understandable that the mass percentage of various substances in the reaction system can be controlled by controlling the amount added.

[0077] When the mass percentages of the first inert solvent, the C5-C9 alkane solvent, and the second inert solvent in the reaction system are within the above-mentioned range, the synergistic effect of the first inert solvent, the second inert solvent, and the C5-C9 alkane solvent can be better utilized, thereby achieving efficient production of polyolefins.

[0078] Furthermore, in a specific embodiment of the present invention, the preparation process further includes: cooling and separating the escaped gas phase to obtain condensate and separated gas phase; circulating at least a portion of the condensate into each reaction unit to participate in the polymerization reaction, and circulating at least a portion of the separated gas phase into the first reaction unit to participate in the polymerization reaction.

[0079] In detail, the escaping gas phase is sequentially cooled and separated into condensate and separated gas phase. The condensate mainly includes solvent, comonomer, and C5-C9 alkane solvent. For the second reaction unit and subsequent reaction units, the condensate also includes a second inert solvent. The separated gas phase mainly includes olefin monomer and comonomer. For the first reaction unit, the separated gas phase also includes a first inert solvent. Subsequently, at least a portion of the condensate is recycled to the corresponding reaction unit to participate in the polymerization reaction, while at least a portion of the separated gas phase enters the first reaction unit to participate in the polymerization reaction.

[0080] It is understandable that the separated gas phase can be compressed before entering the first reaction unit to further improve the transfer efficiency and concentration of the separated gas phase, thereby increasing the reaction rate and efficiency of the first reaction unit.

[0081] Cooling and separating the escaping gas phase, and then recycling the resulting condensate and the separated gas phase back into the reaction unit to participate in the polymerization reaction, not only improves the utilization rate of materials and reduces production costs, but also further reduces the temperature of the reaction system and improves the production efficiency of polyolefins during the recycling process of the condensate and the separated gas phase back into the reaction unit.

[0082] Furthermore, the present invention also provides an apparatus for preparing polyolefins, the apparatus being used to perform the preparation method described above, the apparatus comprising N reaction units connected end-to-end, where N≥2; wherein, when N is an even number, the first N / 2 reaction units each include a first inert solvent inlet and a gas phase outlet; the last N / 2 reaction units each include a second inert solvent inlet and a gas phase outlet; or, when N is an odd number, the first (N-1) / 2 reaction units each include a first inert solvent inlet and a gas phase outlet, the last (N-1) / 2 reaction units each include a second inert solvent inlet and a gas phase outlet, and the (N+1) / 2th reaction unit includes a first inert solvent inlet, a second inert solvent inlet, and a gas phase outlet.

[0083] In detail, the apparatus provided by the present invention includes N reaction units connected end to end, wherein being connected end to end means that the liquid mixture obtained by the polymerization reaction of the previous reaction unit enters the next reaction unit through the liquid mixture outlet of the previous reaction unit and the liquid mixture inlet of the next reaction unit to continue the polymerization reaction.

[0084] It is understandable that, regardless of whether N is even or odd, the first reaction unit also includes a mixed feed inlet, and at least the last reaction unit also includes a polyolefin product outlet.

[0085] In one specific embodiment, N=2, the first reaction unit includes a first inert solvent inlet and a gas phase outlet, a mixed raw material inlet, and the second reaction unit includes a second inert solvent inlet and a gas phase outlet, as well as a polyolefin product outlet.

[0086] Olefin monomers, comonomers, catalysts, and C5-C9 alkane solvents enter the first reaction unit through the mixed feed inlet. A first inert solvent also enters the first reaction unit through the first inert solvent inlet. In the first reaction unit, the olefin monomers and comonomers undergo polymerization under the action of the catalyst, yielding a liquid mixture and a gas phase. The gas phase exits the first reaction unit through the gas phase outlet. The liquid mixture enters the second reaction unit through the liquid mixture outlet of the first reaction unit and the liquid mixture inlet of the second reaction unit. A second inert solvent enters the second reaction unit through the second inert solvent inlet. In the second reaction unit, the raw materials continue to undergo polymerization, yielding a polyolefin product and a gas phase. The gas phase exits the second reaction unit through the gas phase outlet, and the polyolefin is collected through the polyolefin outlet.

[0087] In another specific embodiment, N=3, the first reaction unit includes a first inert solvent inlet and a gas phase outlet, and a mixed raw material inlet, the second reaction unit includes a first inert solvent inlet, a second inert solvent inlet, and a gas phase outlet, and the third reaction unit includes a second inert solvent inlet, a gas phase outlet, and a polyolefin product outlet.

[0088] Olefin monomers, comonomers, catalysts, and C5-C9 alkane solvents enter the first reaction unit through the mixed feed inlet. A first inert solvent also enters the first reaction unit through its inlet. In the first reaction unit, the olefin monomers and comonomers undergo polymerization under the action of the catalyst, yielding a liquid mixture and a gas phase. The gas phase exits the first reaction unit through its gas phase outlet. The liquid mixture enters the second reaction unit through the liquid mixture outlet of the first reaction unit and the liquid mixture inlet of the second reaction unit. The first and second inert solvents enter the second reaction unit through their respective inlets. An inert solvent feed inlet enters the second reaction unit, where the raw materials continue to undergo polymerization, resulting in a liquid mixture and a gas phase. The gas phase exits the second reaction unit through a gas phase outlet. The liquid mixture enters the third reaction unit through the liquid mixture outlet of the second reaction unit and the liquid mixture feed inlet of the third reaction unit. The second inert solvent enters the third reaction unit through the second inert solvent feed inlet. In the third reaction unit, the raw materials continue to undergo polymerization, resulting in a polyolefin product and a gas phase. The polyolefin product is collected through the polyolefin product outlet, and the gas phase exits the third reaction unit through the gas phase outlet.

[0089] The apparatus provided by this invention can be used to perform the above-described preparation method, thereby effectively improving the production efficiency of polyolefins and the content of comonomers, and reducing the polyolefin dispersity coefficient.

[0090] Furthermore, in a specific embodiment of the present invention, it further includes N cooling-gas-liquid separation processing units, which are connected to the reaction unit in a one-to-one correspondence; the reaction unit further includes a condensate inlet, and the first reaction unit further includes a compressed gas inlet; each cooling-gas-liquid separation processing unit includes a cooling device, a separation device, and a compression device; the cooling device includes a gas phase inlet and a cooling gas phase outlet; the separation device includes a cooling gas phase inlet, a separated gas phase outlet, and a condensate outlet; the compression device includes a separated gas phase inlet and a compressed gas outlet; the cooling gas phase outlet and the cooling gas phase inlet are connected, and the separated gas phase outlet and the separated gas phase inlet are connected; wherein, the N gas phase outlets and the N gas phase inlets are connected in a one-to-one correspondence, the N compressed gas outlets are connected to the compressed gas inlet of the first reaction unit, and the N condensate outlets and the N condensate inlets are connected in a one-to-one correspondence.

[0091] The one-to-one connection between the cooling-gas-liquid separation treatment unit and the reaction unit means that the gas phase outlet of the reaction unit is connected to the gas phase inlet of the cooling-gas-liquid separation treatment unit, and the condensate outlet of the cooling-gas-liquid separation treatment unit is connected to the condensate inlet of the reaction unit.

[0092] For example, the gas phase outlet of the first reaction unit is connected to the gas phase inlet of the first cooling-gas-liquid separation unit, and the condensate outlet of the first cooling-gas-liquid separation unit is connected to the condensate inlet of the first reaction unit; the gas phase outlet of the last reaction unit is connected to the gas phase inlet of the last cooling-gas-liquid separation unit, and the condensate outlet of the last cooling-gas-liquid separation unit is connected to the condensate inlet of the last reaction unit.

[0093] Specifically, taking the second reaction unit as an example, the gas phase escaping from the polymerization reaction in the second reaction unit enters the cooling device through the gas phase outlet of the second reaction unit and the gas phase inlet of the cooling device. In the cooling device, it undergoes cooling treatment to obtain a cooled gas phase. The cooled gas phase enters the separation device through the cooled gas phase outlet and the cooled gas phase inlet. In the separation device, it undergoes gas-liquid separation treatment to obtain a separated gas phase and a condensate. The condensate enters the second reaction unit through the condensate outlet and the condensate inlet. The separated gas phase enters the compression unit through the separated gas phase outlet and the separated gas phase inlet. In the compression unit, it is compressed. The compressed material enters the first reaction unit through the compressed gas outlet and the compressed gas inlet.

[0094] In this invention, the cooling device operates at a temperature of 5-25°C, the gas-liquid separator has a separation efficiency of over 90%, an operating pressure range of 0.5 MPa to 3.0 MPa, and a volumetric flow rate capacity of 100 L / h to 5000 L / h. The compression device has a compression ratio of 1:1 to 10:1, an outlet pressure range of 0.5 MPa to 6.0 MPa, and a power requirement of 10 kW to 500 kW.

[0095] When the device includes a cooling-gas-liquid separation unit, it can not only improve the utilization rate of materials and reduce production costs, but also further reduce the temperature of the reaction system and improve the production efficiency of polyolefins during the process of condensate and the separated gas phase circulating into the reaction unit.

[0096] The preparation method provided by the present invention will be described in detail below through specific embodiments.

[0097] Example 1

[0098] Figure 1 This is a schematic diagram of the apparatus used in this embodiment for preparing polyolefins.

[0099] The device includes a first reaction unit, a second reaction unit, a third reaction unit, a first cooling-gas-liquid separation processing unit, a second cooling-gas-liquid separation processing unit, and a third cooling-gas-liquid separation processing unit.

[0100] The first reaction unit includes a first reactor R1, which includes a raw material inlet F1, a first inert solvent inlet, a first gas phase outlet, a liquid mixture outlet, and a mixed raw material inlet F1; the second reaction unit includes a second reactor R2, which includes a liquid mixture inlet, a first inert solvent inlet, a second inert solvent inlet, a second gas phase outlet, a liquid mixture outlet, and a graphene particle inlet; the third reaction unit includes a third reactor R3, which includes a second liquid mixture inlet, a second inert solvent inlet, a graphene particle inlet, a third gas phase outlet, and a polyethylene product outlet.

[0101] The first cooling-gas-liquid separation processing unit includes a first cooler E1, a first gas-liquid separator G1, a first gas compressor C1, and a first material conveying pump L1; the second cooling-gas-liquid separation processing unit includes a second cooler E2, a second gas-liquid separator G1, a second gas compressor C2, and a second material conveying pump L2; the third cooling-gas-liquid separation processing unit includes a third cooler E3, a third gas-liquid separator G2, a third gas compressor C3, and a third material conveying pump L3.

[0102] It also includes a first feed separator S1, a second feed separator S2, and a third feed separator S3. The first feed separator S1 includes a first inert solvent inlet F2, the second feed separator S2 includes a first inert solvent inlet F3, and the third feed separator S3 includes a graphene particle inlet F4. The first inert solvent enters the first feed separator S1 through the first inert solvent inlet F2, and then enters the first and second reaction units respectively through pipelines via the first inert solvent inlets of the first and second reaction units. The second inert solvent enters the second feed separator S2 through the second inert solvent inlet F3, and then enters the second and third reaction units respectively through pipelines via the second inert solvent inlets of the second and third reaction units. Graphene particles enter the third feed separator S3 through the graphene particle inlet F4, and then enter the second and third reaction units through the graphene particle inlet of the second reaction unit and the graphene particle inlet of the third reaction unit, respectively.

[0103] Olefins, comonomers, C5-C9 alkane solvents, and catalysts enter the first reaction unit through the mixed feed inlet F1. The first reaction unit also contains a first inert solvent that enters through the first inert solvent inlet. In the first reaction unit, polymerization reactions occur between the various raw materials to obtain a liquid mixture and a gas phase. The gas phase enters the first cooling-gas-liquid separation treatment unit through the gas phase outlet and gas phase inlet. After cooling-gas-liquid separation treatment in the first cooling-gas-liquid separation treatment unit, separated gas phase and condensate are obtained. The separated gas phase is compressed to obtain a compressed gas phase, which enters the first reaction unit through the compressed gas inlet. The condensate enters the first reaction unit through the material conveying pump L1 and the condensate inlet.

[0104] The liquid mixture obtained from the first reaction unit enters the second reaction unit. The second reaction unit also contains the first and second inert solvents introduced through the first and second inert solvent inlets, as well as graphene particles introduced through the graphene particle inlet. The polymerization reaction continues in the second reaction unit to obtain a liquid mixture and a gas phase. The gas phase enters the second cooling-gas-liquid separation unit through the gas phase outlet and gas phase inlet. After cooling-gas-liquid separation in the second cooling-gas-liquid separation unit, the separated gas phase and condensate are obtained. The separated gas phase is compressed to obtain a compressed gas phase, which enters the first reaction unit through the compressed gas inlet. The condensate enters the second reaction unit through the material conveying pump L2 and the condensate inlet.

[0105] The liquid mixture obtained from the second reaction unit enters the third reaction unit. The third reaction unit also contains the second inert solvent, which enters through the second inert solvent inlet, and graphene particles, which enter through the graphene particle inlet. In the third reaction unit, the raw materials continue to undergo polymerization to obtain polyolefin products and gas phase. The gas phase enters the third cooling-gas-liquid separation treatment unit through the gas phase outlet and gas phase inlet. After cooling-gas-liquid separation treatment in the third cooling-gas-liquid separation treatment unit, the separated gas phase and condensate are obtained. The separated gas phase is compressed to obtain compressed gas phase, which enters the first reaction unit through the compressed gas inlet. The condensate enters the third reaction unit through the material transfer pump L3 and the condensate inlet. The polyolefin products are collected through the discharge stream P3 of the third reactor.

[0106] The apparatus used in Examples 1-10 and Comparative Examples 1-2 is the same as that in Example 1. The apparatus used in Example 11 is basically the same as that in Example 1, except that, as Figure 2 As shown, the number of reaction units is 4, wherein the first and second reaction units include a first inert solvent, and the third and fourth reaction units include a second inert solvent. The apparatus used in Example 12 is basically the same as that in Example 1, except that, as... Figure 3 As shown, the number of reaction units is 5, wherein the first reaction unit, the second reaction unit, and the third reaction unit include a first inert solvent, and the third reaction unit, the fourth reaction unit, and the fifth reaction unit include a second inert solvent.

[0107] The specific reaction parameters for all embodiments and comparative examples are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111]

[0112]

[0113] Test case

[0114] The liquid mixtures and final polyolefin products from each reactor in all examples and comparative examples were tested, specifically including the following steps:

[0115] Sample collection: Under stable reactor operation, liquid mixture samples were collected from reactors R1, R2, and R3 respectively; samples were also collected from the final polyolefin product to ensure that the samples were representative.

[0116] Mass fraction determination: The mass fraction of polyolefins in each reactor was determined using liquid chromatography; the mass fraction of polyolefins in the liquid mixtures in each reactor (R1, R2, R3) was recorded; the mass fraction of copolymer monomers in the products was determined and recorded.

[0117] Dispersibility index: The dispersibility index of polyolefin products was determined using gel permeation chromatography to assess their flowability and uniformity.

[0118] Production rate determination: Record the polyolefin output per unit time (per hour) during the production process, and calculate and record the polyolefin production rate (kg / h).

[0119] The specific test results are shown in Table 2.

[0120] Table 2

[0121]

[0122]

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of a polyolefin, characterized in that, The method comprises the following steps: The mixed raw material comprising olefin monomer, comonomer, catalyst and C5-C9 alkane solvent is sequentially flowed into the next reaction unit to continue the polymerization reaction after the polymerization reaction in the previous reaction unit, and the polyolefin is extracted from at least the Nth reaction unit; during the polymerization reaction, the gas phase escaping from the reaction system is separated from the reaction unit; Wherein, N is an even number, and the polymerization reaction further comprises inputting a first inert solvent into the front N / 2 reaction units and inputting a second inert solvent into the rear N / 2 reaction units; or, N is an odd number, and the polymerization reaction further comprises inputting a first inert solvent into the front (N-1) / 2 reaction units, inputting a second inert solvent into the rear (N-1) / 2 reaction units, and inputting the first inert solvent and the second inert solvent into the (N+1) / 2 reaction unit.

2. The production method according to claim 1, characterized by, The boiling point of the first inert solvent is not higher than 80℃, and the boiling point of the second inert solvent is not lower than 160℃.

3. The preparation method according to claim 1, characterized in that, N is 3-5.

4. The production method according to any one of claims 1 to 3, characterized by, The boiling point of the first inert solvent is 10-75℃; And / or, the boiling point of the second inert solvent is 160-250℃.

5. The preparation method according to claim 4, characterized in that, The first inert solvent is C3-C5 alkane; And / or, the second inert solvent is C15-C18 alkane.

6. The method of claim 1, wherein, N is an even number, and the polymerization reaction further comprises inputting graphene particles into the rear N / 2 reaction units; or, N is an odd number, and the polymerization reaction further comprises inputting graphene particles into the (N+1) / 2 reaction unit and the rear (N-1) / 2 reaction units.

7. The production method according to claim 6, wherein The equivalent particle diameter of the graphene particles is 50-200nm.

8. The method of claim 1, wherein, In each reaction unit, the mass percentage of the first inert solvent in the reaction system is 5-25%; And / or, in each reaction unit, the mass percentage of the C5-C9 alkane solvent in the reaction system is 20-40%; And / or, in each reaction unit, the mass percentage of the second inert solvent in the reaction system is 10-30%.

9. The production method according to claim 1, characterized by, Further comprising: Cooling and gas-liquid separation treatment is performed on the escaping gas phase to obtain condensed liquid and separated gas phase; At least part of the condensed liquid is circulated into each reaction unit to participate in the polymerization reaction, and at least part of the separated gas phase is circulated into the first reaction unit to participate in the polymerization reaction.

10. An apparatus for producing a polyolefin, characterized by comprising: The device is used to perform the preparation method of any one of claims 1-9, and the device comprises N reaction units connected in series, N≥2; Wherein, when N is an even number, the front N / 2 reaction units each comprise a first inert solvent feeding port and a gas phase outlet; the rear N / 2 reaction units each comprise a second inert solvent feeding port and a gas phase outlet; Or, N is an odd number, the first (N-1) / 2 reaction units each include a first inert solvent feed port and a gas phase outlet, the last (N-1) / 2 reaction units each include a second inert solvent feed port and a gas phase outlet, and the (N+1) / 2 reaction unit includes a first inert solvent feed port, a second inert solvent feed port, and a gas phase outlet.

11. The apparatus of claim 10, wherein, Further comprising N cooling-gas-liquid separation processing units, which are in one-to-one correspondence with the reaction units; the reaction units further comprise a condensed liquid feed port, and the first reaction unit further comprises a compressed gas feed port; Each cooling-gas-liquid separation processing unit comprises a cooling device, a separation device, and a compression device; The cooling device comprises a gas phase feed port and a cooled gas phase outlet; the separation device comprises a cooled gas phase feed port, a separated gas phase outlet, and a condensed liquid outlet; the compression device comprises a separated gas phase feed port and a compressed gas outlet; the cooled gas phase outlet and the cooled gas phase feed port are in communication, and the separated gas phase outlet and the separated gas phase feed port are in communication; Wherein, the N gas phase outlets and the N gas phase feed ports are in one-to-one correspondence, the N compressed gas outlets and the compressed gas feed port of the first reaction unit are in communication, and the N condensed liquid outlets and the N condensed liquid feed ports are in one-to-one correspondence.

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