Method and system for separating boron trifluoride and complex catalyst thereof in olefin polymerization reaction

Abstract

The invention provides a method and a system for separating boron trifluoride and a complex catalyst thereof in olefin polymerization reaction. The method comprises the following steps: carrying out ultrasonic treatment on a mixture after olefin polymerization reaction, and simultaneously carrying out first flash separation to separate out BF3 gas; the separated liquid phase is subjected to liquid-liquid separation, a light liquid phase and a heavy liquid phase are obtained, and the heavy liquid phase comprises a BF3 complex; the light liquid phase is subjected to second flash evaporation separation, BF3 gas is separated out, and an olefin polymerization reaction product is obtained. The system comprises an ultrasonic treatment and first flash evaporation unit, a liquid-liquid separation unit and a second flash evaporation unit. The method and the system provided by the invention are suitable for separating boron trifluoride and a complex catalyst thereof in low-viscosity PAO, and can improve the recycling rate and the separation efficiency of BF3 and a complex thereof.

Description

Technical Field

[0001] This invention relates to a method and system for separating boron trifluoride and its complex catalysts in olefin polymerization reactions, belonging to the field of catalyst separation technology in olefin polymerization. Background Technology

[0002] Polyalphaolefin (PAO) synthetic oil is a high-purity oil produced by oligomerization and hydrogenation saturation of alpha-olefins under the action of a catalyst. Compared with mineral base oils, PAO has advantages such as high viscosity index, low pour point, high oxidation stability, and low volatility. Furthermore, the feedstock composition and degree of polymerization can be adjusted as needed to obtain products with a wide viscosity range.

[0003] The performance of polyalphaolefin (PAO) synthetic oils mainly depends on the degree of polymerization and relative molecular mass distribution of the PAO product. Selecting a suitable catalyst is crucial for improving product quality. Currently, catalyst systems used for the oligomerization of alpha-olefins to prepare lubricating oil base oils include metallocene catalysts, chromium metal catalysts, Lewis acid catalysts, Zn catalysts, and ionic liquid catalysts. Low-viscosity oils are the most widely used in polymerization, accounting for approximately 90% of all PAO usage, primarily in engine oils, hydraulic oils, ATF fluids, gear oils, offshore drilling fluids, and optical fiber filler oils. Due to its high yield and high selectivity in the catalytic synthesis of low-viscosity PAO, BF3 and its complexes remain widely used as traditional catalysts for producing low-viscosity PAO. In the resin, pharmaceutical, and fragrance industries, BF3 is also widely used as a polymerization catalyst, and its usage is increasing year by year.

[0004] The widespread use of this catalyst has brought about a series of post-processing issues. On the one hand, BF3 has a certain degree of toxicity, and its emissions can cause environmental pollution. On the other hand, BF3 is corrosive and can corrode various metals. Therefore, after the olefin polymerization PAO is completed, BF3 and its complex catalysts must be separated, removed, and recovered from the product stream. If BF3 and its complexes are not removed, the residual BF3 will cause equipment corrosion and affect the further processing of the product materials and the quality of subsequent products. In addition, BF3 is costly; achieving BF3 recycling and reuse can improve its efficiency and reduce the catalyst cost of the process.

[0005] Therefore, developing methods and systems for separating boron trifluoride and its complex catalysts from low-viscosity PAO, and reducing the equipment corrosion and catalyst loss problems often encountered in the synthesis of low-viscosity PAO caused by catalyst separation, has become a key challenge in the development of current low-viscosity PAO catalyst separation technology.

[0006] CN1217726A discloses a method for recovering boron trifluoride complexes. By applying a DC and / or AC voltage to a non-conductive fluid in which the boron trifluoride complex is dispersed / dissolved, the complex is caused to settle from the non-conductive fluid, allowing recovery of the complex without changing its molar ratio. However, this technology is costly, the settling process consumes a large amount of electrical energy, and the equipment is complex, making it unsuitable for large-scale engineering.

[0007] CN112299940A discloses a method and apparatus for the continuous preparation of polyalphaolefins. The mixture after polymerization is subjected to gas-liquid separation via atmospheric flash, with the separated gas phase returned to the reactor. The liquid phase is separated into a light liquid phase and a heavy liquid phase by centrifugation. The light liquid phase is post-processed to obtain the polyalphaolefin product, while the heavy liquid phase is returned to the reactor for reuse. This technology has high energy consumption, unsatisfactory catalyst separation efficiency, and significant activity degradation of the reused catalyst.

[0008] CN108251155A discloses a method for preparing low-viscosity polyalphaolefin synthetic oil. The product after polymerization is subjected to flash evaporation followed by sedimentation / centrifugation to recover and recycle the complexing catalyst, and then the oil phase is washed with alkaline water. This technology generates a large amount of boron- and fluoride-containing wastewater, causing new environmental pollution, and also has a low BF3 recovery rate.

[0009] Existing methods and systems for separating boron trifluoride and its complex catalysts suffer from problems such as low boron trifluoride recovery rate, difficulty in separating boron trifluoride complexes, and catalyst corrosion of equipment during the post-processing of polyolefin products. Therefore, there is an urgent need to develop novel methods and systems for separating boron trifluoride and its complex catalysts in olefin polymerization reactions. Summary of the Invention

[0010] To address at least one of the aforementioned technical problems, the present invention aims to provide a method and system for separating boron trifluoride and its complex catalysts in olefin polymerization reactions. The method and system of the present invention are suitable for separating boron trifluoride and its complex catalysts from low-viscosity PAO, and can improve the recovery rate and separation efficiency of BF3 and its complexes.

[0011] To achieve the above objectives, the first aspect of the present invention provides a method for separating boron trifluoride and its complex catalysts in olefin polymerization reactions, comprising the following steps:

[0012] (1) The mixture after the olefin polymerization reaction is subjected to ultrasonic treatment and a first flash separation is performed to obtain a first gas phase and a first liquid phase, wherein the first gas phase includes BF3 gas.

[0013] (2) The first liquid phase is subjected to liquid-liquid separation to obtain a light liquid phase and a heavy liquid phase, wherein the heavy liquid phase includes a BF3 complex;

[0014] (3) The light liquid phase is separated by a second flash evaporation to obtain a second gas phase and a second liquid phase. The second gas phase includes BF3 gas, and the second liquid phase is the product of the olefin polymerization reaction.

[0015] According to a specific embodiment of the present invention, preferably, the ultrasonic treatment time is 10 to 60 minutes.

[0016] According to a specific embodiment of the present invention, preferably, the frequency of the ultrasonic treatment is 10 to 30 kHz.

[0017] According to a specific embodiment of the present invention, preferably, the acoustic intensity of the ultrasonic treatment is 5-60 W / cm. 2 .

[0018] According to a specific embodiment of the present invention, preferably, the first flash evaporation is a flash evaporation at room temperature and pressure.

[0019] According to a specific embodiment of the present invention, preferably, the liquid-liquid separation method includes one or a combination of sedimentation separation, centrifugal separation and membrane separation.

[0020] According to a specific embodiment of the present invention, preferably, the density of the light liquid phase is 0.7–0.9 g / cm³. 3 The density of the heavy liquid phase is greater than 0.9 to 1.2 g / cm³. 3 .

[0021] According to a specific embodiment of the present invention, preferably, the second flash separation is high-temperature atmospheric pressure flash evaporation.

[0022] According to a specific embodiment of the present invention, preferably, the temperature of the second flash separation is 50–180°C.

[0023] According to a specific embodiment of the present invention, preferably, the second flash separation time is 10 to 30 minutes.

[0024] A second aspect of the present invention provides a separation system for boron trifluoride and its complex catalysts in olefin polymerization reactions. The system is used to implement the above-described method for separating boron trifluoride and its complex catalysts in olefin polymerization reactions. The system includes: an ultrasonic treatment and first flash evaporation unit, a liquid-liquid separation unit, and a second flash evaporation unit. The ultrasonic treatment and first flash evaporation unit is provided with at least an inlet, a first gas phase outlet, and a first liquid phase outlet. The liquid-liquid separation unit is provided with at least an inlet, a light liquid phase outlet, and a heavy liquid phase outlet. The second flash evaporation unit is provided with at least an inlet, a second gas phase outlet, and a second liquid phase outlet. The first liquid phase outlet of the ultrasonic treatment and first flash evaporation unit is connected to the inlet of the liquid-liquid separation unit, and the light liquid phase outlet of the liquid-liquid separation unit is connected to the inlet of the second flash evaporation unit.

[0025] According to a specific embodiment of the present invention, preferably, the ultrasonic treatment and first flash evaporation unit includes a flash evaporation tank equipped with an ultrasonic generator.

[0026] According to a specific embodiment of the present invention, preferably, the liquid-liquid separation unit includes one or a combination of several of the following: sedimentation separation device, centrifugal separation device, and membrane separation device.

[0027] The present invention has at least the following beneficial effects:

[0028] This invention employs ultrasonic treatment to break the coordination bonds between metastable BF3 complexes under ultrasonic action. A first flash evaporation separates a portion of the BF3 gas, simultaneously transforming the metastable BF3 complexes into stable BF3 complexes. The stable BF3 complexes exhibit higher interfacial tension with the products of olefin polymerization (e.g., PAO), allowing for relatively easy separation from the olefin polymerization products during liquid-liquid separation. The resulting light liquid phase is then subjected to a second flash evaporation to further separate trace amounts of BF3 from the olefin polymerization products, yielding the final olefin polymerization product. This invention utilizes the synergistic effect between each step to significantly improve the recovery rate and separation efficiency of BF3 and its complexes, particularly achieving highly efficient separation of the BF3 complexes. This avoids waste of BF3 and its complexes, reduces production costs, and prevents catalyst corrosion of equipment during subsequent processing of olefin polymerization products. It is suitable for separating boron trifluoride and its complex catalysts from low-viscosity PAO. This invention has the advantages of simple process, high efficiency, low investment and easy operation. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the mechanism of ultrasonic treatment in a specific embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the separation system for boron trifluoride and its complex catalysts in the olefin polymerization reaction provided in a specific embodiment of the present invention.

[0031] Explanation of icon numbers:

[0032] 1-Ultrasonic treatment and first flash evaporation unit; 2-Liquid-liquid separation unit; 3-Second flash evaporation unit. Detailed Implementation

[0033] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will now be described in detail below, but this should not be construed as limiting the scope of the invention.

[0034] According to a specific embodiment of the first aspect of the present invention, the present invention provides a method for separating boron trifluoride and its complex catalysts in olefin polymerization reactions, comprising the following steps:

[0035] (1) The mixture after the olefin polymerization reaction is subjected to ultrasonic treatment and a first flash separation is performed to obtain a first gas phase and a first liquid phase, wherein the first gas phase includes BF3 gas.

[0036] (2) The first liquid phase is subjected to liquid-liquid separation to obtain a light liquid phase and a heavy liquid phase, wherein the heavy liquid phase includes a BF3 complex;

[0037] (3) The light liquid phase is separated by a second flash evaporation to obtain a second gas phase and a second liquid phase. The second gas phase includes BF3 gas, and the liquid phase is a product of olefin polymerization reaction.

[0038] Boron trifluoride and its complex catalysts generally include BF3 complexes composed of BF3 and ligands (also called coordinators), or mixed systems containing BF3 complexes and BF3. The complexes exhibit different structures depending on the proportion of BF3 complexation.

[0039] Taking BF3-ROH catalyst as an example, when the BF3 content is low, ROH is in excess. Both the F atoms in BF3 and the O atoms in ROH are typical atoms for hydrogen bonding. Under the bridging effect of H atoms in ROH, a large number of hydrogen bonds are formed, such as FHO and OHO. The interaction of these numerous hydrogen bonds makes the structure of the resulting complex BF3:(ROH)n relatively stable. However, when the BF3 content is sufficient, the strong ability of B atoms to accept lone pairs of electrons from O atoms in ROH continuously breaks down the ROH atoms forming hydrogen bonds, ultimately forming a 1:1 complex product, BF3:ROH. The resulting complex BF3:ROH is a metastable product.

[0040] like Figure 1As shown, taking BF3-ROH catalyst as an example, this invention employs ultrasonic treatment to break the BO coordination bonds between the metastable complex BF3 and ROH under ultrasonic action, generating free BF3 gas. A portion of the BF3 gas is then separated through a first flash evaporation. Ultrasonic bond breaking is primarily achieved through the "hot spot" mechanism of cavitation. Ultrasonic energy is concentrated in a small space within the reaction system, and the annihilation of cavitation nuclei generates extreme high temperature and pressure, forming a so-called "hot spot." The high temperature and pressure surrounding the hot spot, along with the accompanying intense mechanical shear force, can break the bonds, initiating a thermal decomposition reaction effect similar to combustion. In addition to cavitation as the primary driving force, the ultrasonic treatment of this invention also has auxiliary effects such as mechanical vibration and thermal action. Due to the significant difference in vibrational velocity between BF3 and ROH particles in the BF3 catalyst, friction occurs, generating heat and causing localized heating, even localized high temperatures, which leads to the breakage of the coordination bonds in the metastable BF3 catalyst.

[0041] Simultaneously, under the ultrasonic treatment of this invention, the structure of the BF3 catalyst forms a large number of hydrogen bonds through the bridging effect of H atoms, causing the metastable BF3:ROH to gradually transform into the stable BF3:(ROH)n structure. This structure exhibits high stability due to the presence of numerous hydrogen bonds, and ultrasonic treatment cannot achieve bond breaking or cleavage. However, the interfacial tension between this stable BF3 complex and the products of olefin polymerization (e.g., PAO) is relatively large, resulting in poor solubility. Only a small portion is dispersed and / or dissolved in the olefin polymerization products, making it relatively easy to separate from the olefin polymerization products during subsequent liquid-liquid separation. The light liquid phase obtained after liquid-liquid separation is further separated by a second flash evaporation to further separate trace amounts of BF3 from the olefin polymerization products, yielding the final olefin polymerization product.

[0042] In some embodiments, the BF3 complex comprises a complex of BF3 and an organic oxygen-containing compound. The organic oxygen-containing compound includes, but is not limited to, at least one of: methanol, dimethyl ether, ethanol, diethyl ether, propanol, isopropanol, acetone, butanol, isobutanol, n-pentanol, n-hexanol, and butanone.

[0043] In some embodiments, the olefin polymerization reaction includes the polymerization reaction of α-olefins, and the product of the olefin polymerization reaction includes polyα-olefins. Specifically, the α-olefins may include C8 to C96 olefins. 12 Long-chain α-olefins.

[0044] In some embodiments, the mixture following the olefin polymerization reaction comprises a low-viscosity PAO containing boron trifluoride and its complex catalyst, having a viscosity of 1.5–6.5 mm. 2 / s.

[0045] In some embodiments, the ultrasonic treatment time is 10 to 60 minutes, preferably 20 to 50 minutes.

[0046] In some embodiments, the frequency of the ultrasonic treatment is 10–30 kHz, preferably 15–25 kHz.

[0047] In some embodiments, the acoustic intensity of the ultrasonic treatment is 5–60 W / cm². 2 Preferably, it is 10–50 W / cm 2 .

[0048] In some embodiments, the first flash evaporation is a flash evaporation at room temperature and pressure. The room temperature is generally 20-30°C, and the pressure is 101.325 kPa.

[0049] In some embodiments, the liquid-liquid separation method includes one or a combination of sedimentation separation, centrifugal separation and membrane separation, with centrifugal separation being preferred.

[0050] In some embodiments, the density of the light liquid phase is 0.7–0.9 g / cm³. 3 The density of the heavy liquid phase is greater than 0.9 to 1.2 g / cm³. 3 .

[0051] In some embodiments, the second flash separation is high-temperature, atmospheric-pressure flash evaporation.

[0052] In some embodiments, the temperature of the second flash separation is 50–180°C.

[0053] In some embodiments, the second flash separation time is 10 to 30 minutes.

[0054] In some embodiments, the second gas phase further includes an organic oxygen-containing compound gas.

[0055] According to a specific embodiment of the second aspect of the present invention, such as Figure 2 As shown, the present invention provides a separation system for boron trifluoride and its complex catalysts in olefin polymerization reactions. The system is used to implement the above-mentioned separation method for boron trifluoride and its complex catalysts in olefin polymerization reactions. The system includes: an ultrasonic treatment and first flash evaporation unit 1, a liquid-liquid separation unit 2, and a second flash evaporation unit 3. The ultrasonic treatment and first flash evaporation unit 1 is provided with at least an inlet, a first gas phase outlet, and a first liquid phase outlet. The liquid-liquid separation unit 2 is provided with at least an inlet, a light liquid phase outlet, and a heavy liquid phase outlet. The second flash evaporation unit 3 is provided with at least an inlet, a second gas phase outlet, and a second liquid phase outlet. The first liquid phase outlet of the ultrasonic treatment and first flash evaporation unit 1 is connected to the inlet of the liquid-liquid separation unit 2, and the light liquid phase outlet of the liquid-liquid separation unit 2 is connected to the inlet of the second flash evaporation unit 3.

[0056] In some embodiments, the ultrasonic treatment and first flash evaporation unit 1 includes a flash evaporation tank equipped with an ultrasonic generator. Specifically, the flash evaporation tank equipped with the ultrasonic generator may also be equipped with temperature and pressure detectors. A condenser may be further provided at the top of the flash evaporation tank equipped with the ultrasonic generator for condensing the first gas phase. The first gas phase outlet is located at the top of the ultrasonic treatment and first flash evaporation unit 1, and the first liquid phase outlet is located at the bottom of the ultrasonic treatment and first flash evaporation unit 1.

[0057] In some embodiments, the liquid-liquid separation unit 2 includes one or a combination of several of the following: sedimentation separation device, centrifugal separation device, and membrane separation device.

[0058] In some embodiments, the second flash unit 3 includes a flash tank. Specifically, the flash tank may also be equipped with temperature and pressure detectors. A condenser may be further provided at the top of the flash tank for condensing the second gas phase. The second gas phase outlet is located at the top of the second flash unit 3, and the second liquid phase outlet is located at the middle or bottom of the second flash unit 3.

[0059] In some embodiments, the first gas phase and the second gas phase containing BF3 gas separated in steps (1) to (3), as well as the heavy liquid phase containing BF3 complex, can be recycled to the olefin polymerization reaction for reuse.

[0060] The present invention is illustrated in detail below by way of examples, but the present invention is not limited to these examples. Of course, various modifications can be made within the scope of the present invention.

[0061] The raw materials used in the following examples and comparative examples include:

[0062] BF3: Industrial grade, Daqing Chemical Research Center;

[0063] C8~C 12 Long-chain alpha-olefins: Industrial grade, Daqing Chemical Research Center;

[0064] Organic oxygen-containing compounds: analytical grade, Tianjin Damao Chemical Reagent Co., Ltd.

[0065] Evaluation and analysis methods:

[0066] The content of BF3 or organic oxygen-containing compounds in the sample was tested by gas chromatography. The BF3 recovery rate in step (1) was calculated using the following formula: the amount of separated BF3 ÷ the amount of BF3 in the crude PAO intermediate product. The BF3 complex separation efficiency in step (2) was calculated using the following formula: the amount of separated organic oxygen-containing compounds ÷ the amount of organic oxygen-containing compounds in the crude PAO intermediate product.

[0067] The preparation of the boron trifluoride complex catalysts used in the following examples and comparative examples:

[0068] Boron trifluoride (99.7% purity) is continuously bubbled into the organic oxygen-containing compound using a bottom-insertion bubbling method, while maintaining the temperature below 0°C until saturation is reached. It should be noted that for organic oxygen-containing compounds that may decompose, a regulator should be used to supply the reaction below their decomposition temperature.

[0069] The following examples and comparative examples illustrate the preparation of crude PAO intermediates containing BF3 and its complex catalysts:

[0070] C8~C 12 Long-chain α-olefins were mixed with the above-mentioned boron trifluoride complex catalyst under stirring conditions, and BF3 gas was introduced at a constant pressure of 0.5 MPa to carry out the reaction. The reaction temperature was 40 °C and the reaction time was 3 h to obtain crude PAO intermediate product (i.e., mixture after olefin polymerization reaction) containing BF3 and its complex catalyst.

[0071] Example 1

[0072] (1) The crude PAO intermediate product (i.e., the mixture after olefin polymerization) containing 2720 ppm BF3 and 1280 ppm methanol and its methanol complex catalyst was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 15 kHz and the ultrasonic intensity to 50 W / cm. 2 After continuous sonication for 20 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1387 ppm, and the BF3 recovery rate in this step was calculated to be 49.0%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0073] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.81 g / cm³. 3 The density of the heavy liquid phase is 1.13 g / cm³. 3 The alcohol content in the light liquid phase is 50 ppm. The calculated separation efficiency of the BF3 complex in this step is 96.1%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0074] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 100°C for 10 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and methanol gas, and the second liquid phase consists of purified PAO product (i.e., the product of olefin polymerization reaction). The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 7.2 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0075] Example 2

[0076] (1) The crude PAO intermediate product containing 2720 ppm BF3 and 1280 ppm methanol, along with its methanol complex catalyst, was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 15 kHz and the ultrasonic intensity to 50 W / cm. 2 After continuous sonication for 20 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1387 ppm, and the BF3 recovery rate in this step was calculated to be 49.0%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0077] (2) The above-mentioned primary purified PAO intermediate product was passed into a settling tank and allowed to settle for 60 minutes. The settled material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and its density was measured to be 0.84 g / cm³. 3 The density of the heavy liquid phase is 1.10 g / cm³. 3 The alcohol content in the light liquid phase is 178 ppm, and the calculated separation efficiency of the BF3 complex in this step is 86.1%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0078] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 100°C for 30 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and methanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 5.7 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0079] Example 3

[0080] (1) The crude PAO intermediate product containing 2720 ppm BF3 and 1280 ppm methanol, along with its methanol complex catalyst, was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 15 kHz and the ultrasonic intensity to 50 W / cm. 2After continuous sonication for 20 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1387 ppm, and the BF3 recovery rate in this step was calculated to be 49.0%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0081] (2) The above-mentioned primary purified PAO intermediate product was passed into a membrane separation device. The membrane was a microfiltration membrane with a pore size of 0.1–1 micrometer. The material after membrane separation was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and its density was measured to be 0.82 g / cm³. 3 The density of the heavy liquid phase is 1.12 g / cm³. 3 The alcohol content in the light liquid phase is 137 ppm, and the calculated separation efficiency of the BF3 complex in this step is 89.3%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0082] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 80°C for 10 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and methanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 5.1 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0083] Example 4

[0084] (1) The crude PAO intermediate product containing 2720 ppm BF3 and 1280 ppm methanol, along with its methanol complex catalyst, was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 15 kHz and the ultrasonic intensity to 50 W / cm. 2 After continuous sonication for 30 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1363 ppm. The BF3 recovery rate in this step was calculated to be 49.8%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0085] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.81 g / cm³. 3 The density of the heavy liquid phase is 1.13 g / cm³. 3The alcohol content in the light liquid phase is 62 ppm. The calculated separation efficiency of the BF3 complex in this step is 95.2%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0086] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 150°C for 10 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and methanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 2.8 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0087] Example 5

[0088] (1) The crude PAO intermediate product containing 2720 ppm BF3 and 1280 ppm methanol, along with its methanol complex catalyst, was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 25 kHz and the ultrasonic intensity to 50 W / cm. 2 After continuous sonication for 50 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1306 ppm, and the BF3 recovery rate in this step was calculated to be 51.9%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0089] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.79 g / cm³. 3 The density of the heavy liquid phase is 1.12 g / cm³. 3 The alcohol content in the light liquid phase is 27 ppm. The calculated separation efficiency of the BF3 complex in this step is 97.8%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0090] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 100°C for 10 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and methanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 4.3 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0091] Example 6

[0092] (1) The crude PAO intermediate product containing 2720 ppm BF3 and 1280 ppm methanol, along with its methanol complex catalyst, was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 18 kHz and the ultrasonic intensity to 60 W / cm. 2 After continuous sonication for 30 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1469 ppm, and the BF3 recovery rate in this step was calculated to be 45.9%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0093] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.83 g / cm³. 3 The density of the heavy liquid phase is 1.15 g / cm³. 3 The alcohol content in the light liquid phase is 102 ppm, and the calculated separation efficiency of the BF3 complex in this step is 92.0%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0094] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 100°C for 20 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and methanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 4.5 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0095] Example 7

[0096] (1) The crude PAO intermediate product containing 2400 ppm BF3 and 1600 ppm ethanol and its ethanol complex catalyst was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 18 kHz and the ultrasonic intensity to 50 W / cm. 2 After continuous sonication for 30 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1272 ppm, and the BF3 recovery rate in this step was calculated to be 47.0%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0097] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.84 g / cm³. 3 The density of the heavy liquid phase is 0.98 g / cm³. 3 The alcohol content in the light liquid phase is 112 ppm, and the calculated separation efficiency of the BF3 complex in this step is 93.0%. The heavy liquid phase is the BF3-ethanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0098] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 100°C for 20 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and ethanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 4.4 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0099] Example 8

[0100] (1) The crude PAO intermediate product containing 2120 ppm BF3 and 1880 ppm n-propanol, along with its n-propanol complex catalyst, was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 10 kHz and the ultrasonic intensity to 10 W / cm. 2 After continuous sonication for 10 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1166 ppm, and the BF3 recovery rate in this step was calculated to be 45.0%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0101] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.78 g / cm³. 3 The density of the heavy liquid phase is 0.95 g / cm³. 3 The alcohol content in the light liquid phase is 169 ppm, and the calculated separation efficiency of the BF3 complex in this step is 91.0%. The heavy liquid phase is the BF3-n-propanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0102] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 180°C for 10 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and n-propanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 8.7 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0103] Example 9

[0104] (1) The crude PAO intermediate product containing 2720 ppm BF3 and 1280 ppm methanol, along with its methanol complex catalyst, was fed into a flash tank equipped with an ultrasonic generator. The ultrasonic frequency was set to 30 kHz and the ultrasonic intensity to 5 W / cm. 2 After continuous sonication for 60 minutes and simultaneous flash evaporation at room temperature and pressure, a first gas phase and a first liquid phase were obtained. The first gas phase mainly consisted of BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 1578 ppm, and the BF3 recovery rate in this step was calculated to be 41.9%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0105] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.81 g / cm³. 3 The density of the heavy liquid phase is 1.13 g / cm³. 3 The alcohol content in the light liquid phase is 154 ppm, and the calculated separation efficiency of the BF3 complex in this step is 87.9%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0106] (3) The above-mentioned secondary purified PAO intermediate product overflows into a hot flash tank and is hot flashed at 50°C for 30 min to obtain a second gas phase and a second liquid phase. The second gas phase consists of BF3 gas and methanol gas, and the second liquid phase is the purified PAO product. The alcohol content in the second liquid phase is measured to be 0 ppm and the BF3 content is 9.3 ppm. The separated second gas phase is recycled back to the olefin polymerization reactor for reuse.

[0107] Comparative Example 1

[0108] This comparative example is compared with Example 1, and is basically the same as Example 1, except that ultrasonic treatment is not used. This comparative example uses a separation method of room temperature and pressure flash evaporation + centrifugation + hot flash evaporation to separate the crude PAO intermediate product containing a BF3-methanol complex catalyst with a BF3 content of 2720 ppm and a methanol content of 1280 ppm; wherein the room temperature and pressure flash evaporation time is 20 min, and the centrifugation and hot flash evaporation conditions are the same as in Example 1.

[0109] Comparative Example 2

[0110] This comparative example is compared with Example 2, and is basically the same as Example 2, except that ultrasonic treatment is not used. This comparative example uses a separation method of room temperature and pressure flash evaporation + sedimentation separation + hot flash evaporation to separate the crude PAO intermediate product containing a BF3-methanol complex catalyst with a BF3 content of 2720 ppm and a methanol content of 1280 ppm; wherein the room temperature and pressure flash evaporation time is 20 min, the sedimentation separation sedimentation time is 120 min, and the hot flash evaporation conditions are the same as in Example 2.

[0111] Comparative Example 3

[0112] This comparative example is compared with Example 1, which is basically the same as Example 1, except that ultrasonic treatment is not used in the flash evaporation step at room temperature and pressure, but in the hot flash evaporation step.

[0113] (1) The crude PAO intermediate product containing BF3 with a content of 2720 ppm and methanol with a content of 1280 ppm was fed into a flash tank for flash evaporation at room temperature and pressure for 20 min to obtain a first gas phase and a first liquid phase. The first gas phase was mainly BF3 gas, and the first liquid phase was the primary purified PAO intermediate product. The BF3 content in the first liquid phase was measured to be 2051 ppm. The BF3 recovery rate in this step was calculated to be 24.6%. The separated first gas phase was recycled back to the olefin polymerization reactor for reuse.

[0114] (2) The above-mentioned primary purified PAO intermediate product was passed into a centrifuge, the centrifugation speed was set to 3000 r / min, and centrifuged for 20 min. The centrifuged material was divided into a light liquid phase and a heavy liquid phase. The light liquid phase was the secondary purified PAO intermediate product, and the density of the light liquid phase was measured to be 0.82 g / cm³. 3 The density of the heavy liquid phase is 1.14 g / cm³. 3 The alcohol content in the light liquid phase is 163 ppm, and the calculated separation efficiency of the BF3 complex in this step is 87.3%. The heavy liquid phase is the BF3-methanol complex, which is recycled back to the olefin polymerization reactor for reuse.

[0115] (3) The above-mentioned secondary purified PAO intermediate product overflows into a flash evaporator equipped with an ultrasonic generator for hot flash evaporation at 100°C, while the ultrasonic frequency is set to 15kHz and the ultrasonic intensity to 50W / cm. 2 After continuous sonication for 20 minutes, a second gas phase and a second liquid phase were obtained. The second gas phase consisted of BF3 gas and methanol gas, and the second liquid phase was the purified PAO product. The alcohol content in the second liquid phase was measured to be 0 ppm, and the BF3 content was 15.6 ppm. The separated second gas phase was recycled back to the olefin polymerization reactor for reuse.

[0116] Comparative Example 4

[0117] This comparative example is compared with Example 1, and is basically the same as Example 1, except that in step (1), the ultrasonic frequency is 5 kHz and the ultrasonic intensity is 3 W / cm. 2 Continuous ultrasound for 20 minutes.

[0118] Comparative Example 5

[0119] This comparative example is compared with Example 1, and is basically the same as Example 1, except that in step (1), the ultrasonic frequency is 35 kHz and the ultrasonic intensity is 65 W / cm. 2 Continuous ultrasound for 20 minutes.

[0120] Comparative Example 6

[0121] This comparative example is compared with Example 1, and is basically the same as Example 1, except that in step (1), the ultrasonic frequency is 5 kHz and the ultrasonic intensity is 65 W / cm. 2 Continuous ultrasound for 20 minutes.

[0122] The BF3 recovery rate in step (1), the BF3 complex separation efficiency in step (2), and the alcohol content and BF3 content in the purified PAO product in step (3) of Examples 1-9 and Comparative Examples 1-6 are shown in Table 1.

[0123] Table 1

[0124]

[0125]

[0126] As can be seen from the data in Table 1, in each embodiment of the present invention, ultrasonic treatment is used in step (1) to break the coordination bonds between the metastable BF3 complexes under the action of ultrasound, and to separate a portion of BF3 gas by flash evaporation at room temperature and pressure, thereby transforming the metastable BF3 complexes into stable BF3 complexes. The interfacial tension between the stable BF3 complexes and the products of olefin polymerization (e.g., PAO) is relatively large, and it can be easily separated from the products of olefin polymerization during the liquid-liquid separation process. The light liquid phase obtained after liquid-liquid separation is further separated by thermal flash evaporation to separate trace amounts of BF3 from the products of olefin polymerization, thus obtaining the final product of olefin polymerization. The embodiments of this invention utilize the synergistic effect between each step to significantly improve the recovery rate of BF3 and the separation efficiency of its complex catalyst, especially the efficient separation of BF3 complexes. The BF3 recovery rate in step (1) is ≥40%, the BF3 complex separation efficiency in step (2) is ≥85%, and the alcohol content in the purified PAO product in step (3) is 0 ppm and the BF3 content is below 10 ppm. This avoids the waste of BF3 and its complexes, reduces production costs, and prevents catalyst corrosion of equipment during subsequent processing of olefin polymerization products. It is suitable for separating boron trifluoride and its complex catalysts in low-viscosity PAO. The embodiments of this invention have the advantages of simple process, high efficiency, low investment, and easy operation.

[0127] Comparative Examples 1 and 2 did not employ ultrasonic treatment in step (1), while Comparative Example 3 employed ultrasonic treatment in step (3). Although the BF3 content in the purified PAO product could reach approximately 10 ppm, it was still significantly higher than that in Examples 1 and 2. Furthermore, the recovery rate and separation efficiency of steps (1) and (2) in Comparative Examples 1-3 were relatively low. BF3 and alcohol were mainly separated during the thermal flash evaporation process in step (3). When reusing them, further separation of BF3 and alcohol is required to control their ratio before they can be reused in the olefin polymerization reaction, increasing subsequent operating costs. The ultrasonic treatment conditions in Comparative Examples 4-6 were not within the scope controlled by this invention, resulting in a significant decrease in the BF3 recovery rate in step (1) and the BF3 complex separation efficiency in step (2) compared to Example 1.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the substantive technical content of the present invention. The substantive technical content of the present invention is broadly defined within the scope of the claims. Any technical entity or method implemented by others that is completely identical to or an equivalent modification of the claims is considered to be covered within the scope of the claims.

Claims

1. A method for separating boron trifluoride and its complex catalysts in an olefin polymerization reaction, characterized by, The method comprises the following steps: (1) subjecting the mixture after the polymerization of the olefin to ultrasonic treatment while performing first flash separation to obtain a first gas phase and a first liquid phase, the first gas phase comprising BF3 gas; (2) subjecting the first liquid phase to liquid-liquid separation to obtain a light liquid phase and a heavy liquid phase, the heavy liquid phase comprising a BF3 complex; (3) subjecting the light liquid phase to second flash separation to obtain a second gas phase and a second liquid phase, the second gas phase comprising BF3 gas, and the second liquid phase being the product of the polymerization of the olefin.

2. The method of separation of boron trifluoride and its complexes catalysts in olefin polymerization reaction according to claim 1, characterized in that, The ultrasonic treatment is performed for 10-60 min.

3. The method of separation of boron trifluoride and its complexes catalysts in olefin polymerization reaction according to claim 1, characterized in that, The ultrasonic treatment is performed at a frequency of 10-30 kHz.

4. The method of separation of boron trifluoride and its complexes catalysts in olefin polymerization reaction according to claim 1, characterized in that, The acoustic intensity of the ultrasonic treatment is 5 to 60 W / cm 2 .

5. The method of claim 1, wherein the catalyst is a boron trifluoride and a complex thereof. The first flash separation is performed at normal temperature and pressure.

6. The method of claim 1, wherein the catalyst is a boron trifluoride and a complex thereof. The liquid-liquid separation is performed by one or a combination of several of the following methods: sedimentation separation, centrifugal separation and membrane separation.

7. The method of separating boron trifluoride and its complexes catalysts in olefin polymerization reaction according to claim 1, characterized in that, The density of the light liquid phase is 0.7 to 0.9 g / cm 3 The density of the heavy liquid phase is greater than 0.9 to 1.2 g / cm 3 .

8. The method of claim 1, wherein the catalyst is a boron trifluoride and a complex thereof. The second flash separation is performed at high temperature and normal pressure.

9. The method of separation of boron trifluoride and its complexes catalysts in olefin polymerization reaction according to claim 8, characterized in that, The second flash separation is performed at a temperature of 50-180℃.

10. The method of claim 8, wherein the catalyst is a boron trifluoride and a complex thereof. The second flash separation is performed for 10-30 min.

11. A separation system for boron trifluoride and its complex catalysts in olefin polymerization reactions, characterized by, The system is used to realize the method for separating the boron trifluoride catalyst and its complex in the polymerization of the olefin according to any one of claims 1-10, and the system comprises an ultrasonic treatment and first flash separation unit, a liquid-liquid separation unit and a second flash separation unit. The ultrasonic treatment and first flash separation unit is provided with at least an inlet, a first gas phase outlet and a first liquid phase outlet. The liquid-liquid separation unit is provided with at least an inlet, a light liquid phase outlet and a heavy liquid phase outlet. The second flash separation unit is provided with at least an inlet, a second gas phase outlet and a second liquid phase outlet. The first liquid phase outlet of the ultrasonic treatment and first flash separation unit is in communication with the inlet of the liquid-liquid separation unit, and the light liquid phase outlet of the liquid-liquid separation unit is in communication with the inlet of the second flash separation unit.

12. The system for separation of boron trifluoride and its complexes catalysts in olefin polymerization reaction according to claim 11, characterized in that, The ultrasonic treatment and first flash separation unit comprises a flash tank provided with an ultrasonic generator.

13. The system for separation of boron trifluoride and its complexes catalysts in olefin polymerization reaction according to claim 11, characterized in that, The liquid-liquid separation unit comprises one or a combination of several of the following devices: a sedimentation separation device, a centrifugal separation device and a membrane separation device.

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