Process and use for the production of polypropylene by liquid bulk polymerization of propylene, system and use for the production of polypropylene by liquid bulk polymerization of propylene

Abstract

The present application belongs to the technical field of propylene liquid phase bulk polymerization, and particularly relates to a method and application of preparing polypropylene by propylene liquid phase bulk polymerization, and a system and application of preparing polypropylene by propylene liquid phase bulk polymerization. The method comprises the following steps: (1) heating optional hydrogen and liquid phase propylene with a molar quantity of n1 to T1 ℃ to obtain preheated material; (2) adding a catalyst to the preheated material to perform a polymerization reaction at T2 ℃ to obtain a polypropylene product; wherein, by supplementing liquid phase propylene to step (2), the polymerization reaction is under a constant pressure P1; the pressure P1 is greater than the saturated vapor pressure of propylene at the highest temperature in the process of the polymerization reaction. The method and system of the present application can operate under the condition of constant pressure full tank; in the kinetic study, the instantaneous polymerization rate of liquid phase propylene bulk polymerization can be measured, and a continuous propylene polymerization kinetic curve is obtained.

Description

Technical Field

[0001] This invention belongs to the field of propylene liquid-phase bulk polymerization technology, specifically relating to a method and application for preparing polypropylene by propylene liquid-phase bulk polymerization, and a system and application for preparing polypropylene by propylene liquid-phase bulk polymerization. Background Technology

[0002] Propylene polymerization kinetics can quantitatively study the change of polymerization rate with polymerization time, and is an important means of evaluating the polymerization performance of catalysts, as well as an important basis for the basic design of polypropylene plants. Most existing propylene polymerization kinetic evaluations are carried out in slurry systems with inert solvents, or in gas-solid two-phase systems of gaseous propylene and solid polypropylene. Kinetic evaluation devices and methods in propylene liquid bulk systems are rarely reported.

[0003] CN106554441A provides an apparatus and method for studying the bulk polymerization kinetics of propylene. The method is characterized by sampling the liquid-phase propylene and polypropylene slurry at different time points during the polymerization process, and then calculating the change in polymerization conversion rate before the sampling time point based on the change in slurry concentration in the sample. The advantage of this method is that it obtains the average polymerization rate at different polymerization times in a single reaction without interrupting the polymerization reaction. However, the obtained polymerization rate data is limited by the number of samplings, typically averaging over several minutes or tens of minutes, and cannot provide polymerization rate information over a shorter period. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a method and application for preparing polypropylene by liquid-phase bulk polymerization of propylene, as well as a system and application for preparing polypropylene by liquid-phase bulk polymerization of propylene. This invention can operate under constant pressure and full reactor conditions, directly measuring the instantaneous polymerization rate of liquid-phase propylene bulk polymerization, improving data accuracy, and obtaining continuous propylene polymerization kinetic curves.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for preparing polypropylene by liquid-phase bulk polymerization of propylene, the method comprising the following steps:

[0006] (1) Selectively heat hydrogen and liquid propylene with a molar amount of n1 to T1℃ to obtain preheated material;

[0007] (2) A catalyst is added to the preheated material, and a polymerization reaction is carried out at T2℃ to obtain polypropylene product; wherein,

[0008] By adding liquid propylene feed in step (2), the polymerization reaction is kept at a constant pressure P1;

[0009] The pressure P1 is greater than the saturated vapor pressure of propylene at the highest temperature during the polymerization reaction.

[0010] A second aspect of the present invention provides an application of the above-described method in the study of the kinetics of propylene liquid-phase bulk polymerization reaction.

[0011] A third aspect of the present invention provides a system for studying the kinetics of propylene liquid-phase bulk polymerization. The system includes: a propylene storage unit, a conveying and pressure-controlling unit, and a polymerization reaction unit; wherein the conveying and pressure-controlling unit is used to convey propylene stored in the propylene storage unit into the polymerization reaction unit and maintain the polymerization reaction unit at a constant pressure; the conveying and pressure-controlling unit further includes a metering device for measuring the amount of propylene added by the conveying and pressure-controlling unit into the polymerization reaction unit; the polymerization reaction unit includes a temperature control device for controlling the temperature in the polymerization reaction unit.

[0012] The fourth aspect of the present invention provides an application of the system described in the third aspect of the present invention in the liquid-phase bulk polymerization of propylene to prepare polypropylene or in the study of the reaction kinetics of liquid-phase bulk polymerization of propylene.

[0013] Through the above technical solutions, the beneficial effects of the method and application for preparing polypropylene by liquid-phase bulk polymerization of propylene, and the system and application for preparing polypropylene by liquid-phase bulk polymerization of propylene provided by the present invention are as follows:

[0014] Using the method of this invention, the polymerization process can operate stably with a full reactor of liquid propylene. By controlling the initial propylene feed rate and the different initial temperatures within the polymerization reaction before catalyst addition, temperature fluctuations after catalyst addition are reduced, allowing the polymerization reaction to proceed safely under full reactor conditions. In kinetic studies, during the bulk polymerization of propylene, a constant system pressure is maintained by continuously replenishing the reactor with liquid propylene, thereby measuring the instantaneous reaction rate of the bulk polymerization and obtaining continuous propylene polymerization kinetic curves. Attached Figure Description

[0015] Figure 1 The real-time polymerization kinetics curve calculated in Example 1;

[0016] Figure 2 The real-time polymerization kinetics curves calculated in Example 2;

[0017] Figure 3 The real-time polymerization kinetics curves calculated in Example 3;

[0018] Figure 4 The real-time polymerization kinetics curve calculated in Example 4;

[0019] Figure 5 The real-time polymerization kinetics curves calculated for Comparative Example 1 are shown. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of this invention provides a method for preparing polypropylene by liquid-phase bulk polymerization of propylene, the method comprising the following steps:

[0022] (1) Selectively heat hydrogen and liquid propylene with a molar amount of n1 to T1℃ to obtain preheated material;

[0023] (2) A catalyst is added to the preheated material, and a polymerization reaction is carried out at T2℃ to obtain polypropylene product; wherein,

[0024] By adding liquid propylene feed in step (2), the polymerization reaction is kept at a constant pressure P1;

[0025] The pressure P1 is greater than the saturated vapor pressure of propylene at the highest temperature during the polymerization reaction.

[0026] In this invention, the temperature of the polymerization reaction is not specifically limited; for example, any value between 0 and 100°C can be selected. Each temperature point corresponds to a different saturated vapor pressure of propylene, and specific values ​​can be obtained from reference materials. For example, the saturated vapor pressure of propylene at 70°C is 3.095 MPa.

[0027] In this invention, the type of catalyst is not specifically limited, as long as it can be used for propylene polymerization. For example, the main catalyst can be a magnesium chloride-supported Ziegler-Natta titanium catalyst, the co-catalyst can be triethylaluminum, and the external electron donor can be an alkoxysilane. The amount of catalyst used is not particularly limited; it can be added according to conventional amounts used in the art.

[0028] In this invention, hydrogen is used as a molecular weight regulator and has no substantial impact on the results of kinetic studies; its addition is optional. The amount of hydrogen added can be determined according to conventional methods in the field. The initial volume of propylene added to the polymerization reactor at the polymerization temperature is less than the effective volume of the reactor. Here, the effective volume refers to the volume of the polymerization reactor cavity minus the volume of the stirring and other components.

[0029] According to the present invention, T2-T1 is 0-10℃, preferably 1-5℃.

[0030] According to the present invention, the pressure P1 is 1-6 MPa.

[0031] According to the present invention, the method is carried out under stirring conditions, wherein the stirring speed is 100-1000 rpm.

[0032] According to the present invention, in step (1), the ratio of the molar amount n1 of the liquid phase propylene to the total amount n0 of propylene when the container of the polymerization reaction at T2℃ is completely filled with the liquid phase propylene is 1:1.01-1.2.

[0033] Due to the strong exothermic effect of propylene polymerization and the extreme temperature sensitivity of the expansion coefficient of liquid propylene, a full-bottle state of liquid propylene is a must-avoidance situation in conventional batch propylene liquid-phase bulk polymerization units. This is because even slight temperature fluctuations in a full-bottle state can cause drastic changes in system pressure, leading to significant safety risks. Therefore, conducting batch propylene liquid-phase bulk polymerization in a full-bottle state is practically unimaginable for those skilled in the art. This invention overcomes this deficiency in the prior art.

[0034] A second aspect of the present invention provides an application of the above-described method in the study of the kinetics of propylene liquid-phase bulk polymerization reaction.

[0035] Most existing kinetic evaluations of propylene polymerization are carried out in slurry systems with inert solvents or in gas-solid two-phase systems of gaseous propylene and solid polypropylene. There are few reports on kinetic evaluation devices and methods carried out in propylene liquid bulk systems.

[0036] According to the present invention, during the monitoring of the polymerization reaction, the mass flow rate m of the liquid propylene feed at different times is... f The unit is kg / h;

[0037] The instantaneous polymerization rate is:

[0038]

[0039] Where, ρ pr The density of liquid propylene under the conditions of the polymerization reaction, in g / cm³. 3 m cat R represents the amount of catalyst used in the polymerization reaction, expressed in grams. p Represents the instantaneous polymerization rate, in kg. PP ·g cat -1 ·h -1 .

[0040] A third aspect of the present invention provides a system for studying the kinetics of propylene liquid-phase bulk polymerization. The system includes: a propylene storage unit, a conveying and pressure-controlling unit, and a polymerization reaction unit; wherein the conveying and pressure-controlling unit is used to convey propylene stored in the propylene storage unit into the polymerization reaction unit and maintain the polymerization reaction unit at a constant pressure; the conveying and pressure-controlling unit further includes a metering device for measuring the amount of propylene added by the conveying and pressure-controlling unit into the polymerization reaction unit; the polymerization reaction unit includes a temperature control device for controlling the temperature in the polymerization reaction unit.

[0041] The present invention does not impose any special limitations on the specific device used in the polymerization reaction unit, as long as it can provide space for the polymerization reaction. For example, the polymerization reaction unit can be a polymerization reactor with a volume of 0.1-20L, an operating pressure of -0.1MPa to 10MPa, and an operating temperature of -20℃ to 150℃.

[0042] According to the present invention, the conveying pressure control unit includes a propylene conveying unit and a pressure control unit connected in sequence.

[0043] The propylene delivery unit of this invention includes a diaphragm pump. Preferably, the metering device is a flow meter, and the metering device is located between the propylene delivery unit and the pressure control unit.

[0044] When a diaphragm pump is selected for the propylene delivery unit and a flow meter is selected for the metering device, the liquid phase outlet of the propylene storage unit is connected to the inlet of the diaphragm pump. The outlet of the diaphragm pump is divided into two paths. One path is connected to the polymerization reaction unit, and the flow meter is installed between the diaphragm pump and the polymerization reaction unit. The other path flows back to the inlet of the diaphragm pump or the propylene storage unit through at least one of the regulating valve, safety valve and back pressure valve.

[0045] The propylene delivery unit of this invention includes a diaphragm pump. Preferably, the metering device is a balance used to weigh the propylene storage unit.

[0046] When a diaphragm pump is selected for the propylene delivery unit and a balance is selected for the metering device, the propylene storage unit is located on the balance. The liquid phase outlet of the propylene storage unit is connected to the inlet of the diaphragm pump through a flexible pressure-bearing pipe. The outlet of the diaphragm pump is divided into two paths. One path is connected to the polymerization reaction unit, and a flow meter is installed between the diaphragm pump and the polymerization reaction unit. The other path flows back to the inlet of the diaphragm pump or the propylene storage unit through at least one of the regulating valve, safety valve, and back pressure valve.

[0047] According to the present invention, the flow meter has a range of 0-1000 g / min.

[0048] According to the present invention, the error of the flow meter is not greater than 0.5 g / min, preferably not greater than 0.1 g / min.

[0049] According to the present invention, the range of the balance is 0-100000g.

[0050] According to the present invention, the error of the balance is no greater than 0.1g.

[0051] According to the present invention, the delivery and pressure control unit is a plunger pump. When a plunger pump is selected as the delivery and pressure control unit, the plunger pump has a certain storage volume and is equipped with pressure control and flow detection functions, eliminating the need for a separate flow meter. In this case, the liquid phase outlet of the propylene storage unit is connected to the inlet of the plunger pump, and the outlet of the plunger pump is connected to the polymerization reaction unit.

[0052] According to the present invention, the polymerization reaction unit includes a polymerization reactor, and the polymerization reactor is provided with a stirring device.

[0053] According to the present invention, the error of the temperature control device is no greater than 0.5℃, preferably no greater than 0.1℃.

[0054] According to the present invention, the conveying flow rate of the conveying pressure control unit is in the range of 0-1000 g / min.

[0055] The fourth aspect of the present invention provides an application of the system described in the third aspect of the present invention in the liquid-phase bulk polymerization of propylene to prepare polypropylene or in the study of the reaction kinetics of liquid-phase bulk polymerization of propylene.

[0056] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents used in the following examples are commercially available industrial products.

[0057] (1) Plunger pump: Model: 1000D, purchased from ISCO.

[0058] (2) Diaphragm pump: Model: EK1 / M710S, purchased from LEWA, with a flow rate of 0-300g / min.

[0059] (3) The pressure control unit is a regulating valve: Model: 1001-GC-N-36-SV-OS-IEP-36, purchased from Badger;

[0060] (4) NG catalyst: Grade: NG-CRT-09; Purchased from: Sinopec Catalyst Company, Aoda Branch;

[0061] (5) DQ catalyst: grade: DQC401; purchased from: Sinopec Catalyst Company Aoda Branch.

[0062] Example 1

[0063] The polymerization reactor is a 1.6-liter stirred stainless steel vessel with a jacketed oil bath for temperature control; the propylene storage unit is a 2-liter stainless steel tank; the delivery and pressure control unit is a 1-liter plunger pump equipped with a controller that has pressure control and flow display functions.

[0064] At room temperature, after propylene gas purging, 620 g of liquid propylene was added to the polymerization reactor. 0.09 g of hydrogen was added to the reactor using a 500 mL hydrogen metering tank. Stirring was then started at 350 rpm. When the temperature inside the polymerization reactor reached 68°C, the plunger pump outlet pressure was set to 5 MPa. 9.5 mg of NG catalyst, 2.3 mmol of triethylaluminum, and 0.23 mmol of diisopropyldimethoxysilane were then pumped into the polymerization reactor via the plunger pump using liquid propylene. The polymerization reaction began at 70°C. During the polymerization process, the plunger pump continuously fed liquid propylene into the polymerization reactor to maintain the reactor pressure at 5 MPa. After 60 minutes of polymerization, the propylene was recovered and the product was discharged, yielding 187 g of polypropylene powder.

[0065] The ratio of the molar amount of liquid propylene n1 to the total amount of propylene n0 when the polymerization reactor is completely filled with liquid propylene at the polymerization temperature is 1:1.06.

[0066] The real-time polymerization kinetics curve, calculated from the liquid propylene replenishment flow rate detected by the metering device during the polymerization process, is shown below. Figure 1 As shown.

[0067] Example 2

[0068] The polymerization reactor is a 3.4-liter stirred stainless steel reactor with jacketed oil bath temperature control; the propylene storage unit is a 2-liter stainless steel storage tank; the propylene delivery unit uses a diaphragm pump and the metering device uses a flow meter, which is a mass flow meter with a range of 0-100 g / min and an error of 0.1 g / min, in conjunction with a pressure control unit.

[0069] At room temperature, after propylene gas purging, 1200 g of liquid propylene was added to the polymerization reactor without adding hydrogen. Stirring was then started at 500 rpm. When the temperature inside the polymerization reactor reached 66°C, the plunger pump outlet pressure was set to 3.8 MPa. 11.6 mg of DQ catalyst, 2 mmol of triethylaluminum, and 0.2 mmol of diisobutyldimethoxysilane were then pumped into the polymerization reactor using liquid propylene via the plunger pump. The polymerization reaction began at 70°C. During the polymerization reaction, the plunger pump continuously fed liquid propylene into the polymerization reactor to maintain the reactor pressure at 3.8 MPa. After 85 minutes of polymerization, the propylene was recovered and discharged, yielding 117 g of polypropylene powder.

[0070] The ratio of the molar amount of liquid propylene n1 to the total amount of propylene n0 when the polymerization reactor is completely filled with liquid propylene at the polymerization temperature is 1:1.15.

[0071] The real-time polymerization kinetics curve, calculated from the liquid propylene replenishment flow rate detected by the metering device during the polymerization process, is shown below. Figure 2 As shown.

[0072] Example 3

[0073] The polymerization reactor is a 3.4-liter stirred stainless steel reactor with jacketed oil bath temperature control; the propylene storage unit is a 2-liter stainless steel storage tank; the propylene storage unit is placed on an electronic balance with a range of 32,000g and an error of no more than 0.1g; the propylene delivery unit uses a diaphragm pump, in conjunction with a pressure control unit.

[0074] At room temperature, after propylene gas purging, 0.02 g of hydrogen was added to the polymerization reactor using a 500 mL hydrogen metering tank, followed by 1100 g of liquid propylene. Stirring was then started at 500 rpm. When the temperature inside the polymerization reactor reached 68°C, the plunger pump outlet pressure was set to 3.8 MPa. 11.1 mg of DQ catalyst, 2 mmol of triethylaluminum, and 0.2 mmol of diisobutyldimethoxysilane were then pumped into the polymerization reactor using liquid propylene via the plunger pump. The polymerization reaction began at 70°C. During the polymerization process, the plunger pump continuously fed liquid propylene into the polymerization reactor to maintain the reactor pressure at 3.8 MPa. After 85 minutes of polymerization, the propylene was recovered and the product was discharged, yielding 206 g of polypropylene powder.

[0075] The ratio of the molar amount of liquid propylene n1 to the total amount of propylene n0 when the polymerization reactor is completely filled with liquid propylene at the polymerization temperature is 1:1.25.

[0076] The real-time polymerization kinetics curve, calculated from the liquid propylene replenishment flow rate detected by the metering device during the polymerization process, is shown below. Figure 3 As shown.

[0077] Example 4

[0078] The polymerization reactor is a 3.4-liter stirred stainless steel vessel with jacketed oil bath temperature control; the propylene storage unit is a 2-liter stainless steel storage tank; the propylene delivery unit uses a diaphragm pump and the metering device uses a flow meter with a mass flow rate of 0-100 g / min and an error of 0.1 g / min, in conjunction with a pressure control unit.

[0079] At room temperature, after purging the polymerization reactor with propylene gas, 1300 g of liquid propylene was added, and 0.04 g of hydrogen was added using a 500 mL hydrogen metering tank. Stirring was then started at 500 rpm. When the temperature inside the polymerization reactor reached 57°C, the outlet pressure of the plunger pump was set to 3.8 MPa. 11.3 mg of NG catalyst, 2 mmol of triethylaluminum, and 0.2 mmol of diisobutyldimethoxysilane were then pumped into the polymerization reactor using liquid propylene via the plunger pump. The polymerization reaction began at 70°C. During the polymerization reaction, the plunger pump continuously fed liquid propylene into the polymerization reactor to maintain the reactor pressure at 3.8 MPa. After 90 minutes of polymerization, the propylene was recovered and discharged, yielding 286 g of polypropylene powder.

[0080] The ratio of the molar amount of liquid propylene n1 to the total amount of propylene n0 when the polymerization reactor is completely filled with liquid propylene at the polymerization temperature is 1:1.06.

[0081] The real-time polymerization kinetics curve, calculated from the liquid propylene replenishment flow rate detected by the metering device during the polymerization process, is shown below. Figure 4 As shown.

[0082] Comparative Example 1

[0083] The polymerization reactor is a 3.4-liter stirred stainless steel vessel with a jacketed oil bath for temperature control.

[0084] (a) At room temperature, after propylene gas purging, 0.1 g of hydrogen was added to the polymerization reactor using a 500 mL hydrogen metering vessel, followed by 1000 g of liquid propylene. Stirring was then started at 500 rpm. When the temperature inside the polymerization reactor reached 67°C, 11.2 mg of NG catalyst, 2 mmol of triethylaluminum, and 0.2 mmol of diisobutyldimethoxysilane were flushed into the reactor using 300 g of liquid propylene. The polymerization reaction was initiated at 70°C. After 10 minutes of polymerization, the propylene was recovered and the product was discharged, yielding 26 g of polypropylene powder.

[0085] The operation in step (a) was repeated 5 times, with the difference being that the amount of titanium catalyst added each time was 11 mg, 11.1 mg, 10.9 mg, 11.2 mg, and 11 mg, respectively. The polymerization reaction was terminated at 20 minutes, 40 minutes, 60 minutes, 80 minutes, and 100 minutes, respectively, and the resulting polymer powders were 78 g, 146 g, 210 g, 276 g, and 338 g, respectively, with other conditions remaining unchanged.

[0086] The polymerization kinetics curves obtained from the average polymerization rate over various time periods are as follows: Figure 5 As shown.

[0087] Table 1

[0088] Example 1 1.06 2 2.5 Example 2 1.15 4 4.5 Example 3 1.25 2 8 Example 4 1.06 13 14

[0089] As shown in Table 1, by adjusting the ratio of the molar amount of liquid propylene n1 to the total amount of propylene n0 when the polymerization reactor is completely filled with liquid propylene, and further by coordinating the difference between the preheating temperature T1 and the polymerization reaction temperature T2, polymerization kinetic data within the first 5 minutes of the reaction can be obtained. The earliest occurrence of kinetic data in this invention refers to the time corresponding to the leftmost endpoint of the kinetic curve in the attached figures.

[0090] Taking Examples 1 and 3 as examples, although the values ​​of T2-T1 are both 2℃, the value of n1:n0 in Example 1 is 1.06, while the value of n1:n0 in Example 3 is 1.25. The earliest time of kinetic data in Examples 1 and 3 is 2.5 min and 8 min, respectively. The earliest time of kinetic data in Example 1 is 5.5 min earlier than that in Example 3.

[0091] Taking Examples 1 and 4 as examples, the values ​​of n1:n0 are both 1.06. The value of T2-T1 in Example 1 is 2℃, and the value of T2-T1 in Example 4 is 13℃. The earliest time of kinetic data in Examples 1 and 4 is 2.5 min and 14 min, respectively. The earliest time of kinetic data in Example 1 is 11.5 min earlier than that in Example 4.

[0092] By comparison, it can be found that, compared with the comparative example, the present invention can measure real-time kinetic data of propylene liquid-phase bulk polymerization in a single polymerization experiment, and the data is more accurate and detailed.

[0093] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing polypropylene by liquid-phase bulk polymerization of propylene, the method comprising the following steps: (1) Selectively heat hydrogen and liquid propylene with a molar amount of n1 to T1℃ to obtain preheated material; (2) A catalyst is added to the preheated material, and a polymerization reaction is carried out at T2℃ to obtain polypropylene product; wherein, By adding liquid propylene feed in step (2), the polymerization reaction is kept at a constant pressure P1; The pressure P1 is greater than the saturated vapor pressure of propylene at the highest temperature during the polymerization reaction. T2-T1 is 0-10℃; the pressure P1 is 1-6MPa; In step (1), the ratio of the molar amount n1 of the liquid phase propylene to the total amount n0 of propylene when the container for the polymerization reaction at T2℃ is completely filled with the liquid phase propylene is 1:1.01-1.

2.

2. The method according to claim 1, wherein, T2-T1 is 1-5℃.

3. The method according to claim 1 or 2, wherein, The method is carried out under stirring conditions, and the stirring speed is 100-1000 rpm.

4. The application of the method described in any one of claims 1-3 in the kinetic study of propylene liquid-phase bulk polymerization.

5. The application according to claim 4, wherein, During the monitoring of the polymerization reaction, the mass flow rate m of the liquid propylene feed at different times was recorded. f The unit is kg / h; The instantaneous polymerization rate is: Where, ρ pr The density of liquid propylene under the conditions of the polymerization reaction, in g / cm³. 3 m cat R represents the amount of catalyst used in the polymerization reaction, expressed in grams. p Represents the instantaneous polymerization rate, in kg. PP ·g cat -1 ·h -1 .

6. A system for the method of preparing polypropylene by liquid-phase bulk polymerization of propylene according to any one of claims 1-3, the system comprising: The propylene storage unit, the conveying and pressure control unit, and the polymerization reaction unit are provided. The conveying and pressure control unit is used to convey propylene stored in the propylene storage unit into the polymerization reaction unit and maintain the polymerization reaction unit at a constant pressure. The conveying and pressure control unit also includes a metering device for measuring the amount of propylene added by the conveying and pressure control unit into the polymerization reaction unit. The polymerization reaction unit includes a temperature control device for controlling the temperature within the polymerization reaction unit. The conveying and pressure control unit includes a propylene conveying unit and a pressure control unit connected in sequence.

7. The system according to claim 6, wherein, The metering device is a flow meter, and the metering device is located between the propylene conveying unit and the pressure control unit; And / or, the measuring device is a balance used to weigh the propylene storage unit; And / or, the propylene delivery unit includes a diaphragm pump.

8. The system according to claim 7, wherein, The flow meter has a range of 0-1000 g / min; And / or, the error of the flow meter is not greater than 0.5 g / min; And / or, the range of the balance is 0-100000g; And / or, the error of the balance is not greater than 0.1g.

9. The system according to claim 7, wherein, The error of the flow meter is no greater than 0.1 g / min.

10. The system according to claim 6, wherein, The delivery and pressure control unit is a plunger pump.

11. The system according to any one of claims 6-10, wherein, The polymerization reaction unit includes a polymerization reactor, and the polymerization reactor is equipped with a stirring device.

12. The system according to any one of claims 6-10, wherein, The error of the temperature control device is no greater than 0.5℃; And / or, the conveying flow rate of the conveying pressure control unit is in the range of 0-1000g / min.

13. The system according to any one of claims 6-10, wherein, The error of the temperature control device is no greater than 0.1℃.

14. The system according to any one of claims 6-13 is used in the liquid-phase bulk polymerization of propylene to prepare polypropylene or in the study of the reaction kinetics of liquid-phase bulk polymerization of propylene.

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