SEPARATION AND RECOVERY METHOD FOR BORON TRIFLUORIDE AND COMPLEX THEREOF IN OLEFIN POLYMERIZATION REACTION

Abstract

The present invention provides a method for separation and recovery of boron trifluoride and complexes thereof in an olefin polymerization reaction. The method for separation and recovery of boron trifluoride and complexes thereof in an olefin polymerization reaction, comprising: 1) subjecting a mixture obtained after an olefin polymerization reaction to flash distillation separation to separate part of gaseous boron trifluoride; 2) subjecting the liquid phase obtained from the flash distillation separation to membrane separation to obtain complexes of boron trifluoride and a crude product of the olefin polymerization reaction; and 3) subjecting the crude product of the olefin polymerization reaction obtained in step 2) to gas stripping separation to separate the remaining gaseous boron trifluoride, so as to obtain a pure product of the olefin polymerization reaction The present invention designs a matching process based on the polymorphic characteristics of boron trifluoride and complexes thereof to achieve efficient separation of boron trifluoride and complexes thereof from polymerization intermediates.

Claims

1. A method for separation and recovery of boron trifluoride and complexes thereof in an olefin polymerization reaction, comprising: 1) subjecting a mixture obtained after an olefin polymerization reaction to flash distillation separation to separate part of gaseous boron trifluoride; 2) subjecting the liquid phase obtained from the flash distillation separation to membrane separation to obtain complexes of boron trifluoride and a crude product of the olefin polymerization reaction; and 3) subjecting the crude product of the olefin polymerization reaction obtained in step 2) to gas stripping separation to separate the remaining gaseous boron trifluoride, so as to obtain a pure product of the olefin polymerization reaction.

2. The method for separation and recovery according to claim 1, wherein an organic membrane of a fluorine-containing polymer is used in the membrane separation.

3. The method for separation and recovery according to claim 2, wherein the organic membrane of a fluorine-containing polymer is an organic membrane of polyvinylidene fluoride or polytetrafluoroethylene.

4. The method for separation and recovery according to claim 1, wherein the membrane separation is carried out at a separation pressure of 0.1 to 1 MPa and a separation temperature of 5 to 50 C.

5. The method for separation and recovery according to claim 1, further comprising: passing the gaseous boron trifluoride separated in step 1) through a gas booster to pressurize it to a desired pressure for recovery and reuse.

6. The method for separation and recovery according to claim 5, wherein the gaseous boron trifluoride is subjected to a purification treatment prior to the pressurization, wherein the purification treatment comprises cooling the gas down to 0 to 30 C.

7. The method for separation and recovery according to claim 1, further comprising: further subjecting the complexes of boron trifluoride separated in step 2) to solvent extraction before recovery and reuse, wherein the extractant for the solvent extraction is a saturated hydrocarbon with a carbon number of 10 to 18 having an electron-donating group; and the volume ratio of the extractant to the complexes of boron trifluoride is 1:1 to 10:1.

8. The method for separation and recovery according to claim 1, further comprising: subjecting the gaseous boron trifluoride separated in step 3) to complexation and absorption by a complexing agent before reuse.

9. The method for separation and recovery according to claim 8, wherein the complexing agent is water or an alcohol-based complexing agent; and the complexation and absorption is carried out at a temperature of 10 C. to 30 C.

10. The method for separation and recovery according to claim 1, wherein the flash distillation separation is carried out at a flash distillation pressure of 1 to 101 kPa, and a flash distillation temperature of 5 to 120 C. for a flash distillation duration of 1 to 60 min.

11. The method for separation and recovery according to claim 10, wherein the gas stripping separation is carried out at a gas stripping temperature of 5 to 120 C. for a duration of 10 to 60 min, a volume ratio of the gas used for gas stripping to the crude product of the olefin polymerization reaction is 1:1 to 50:1, and a gas stripping medium is one or a combination of two or more of nitrogen, helium, argon, krypton and xenon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to better illustrate the present invention, the invention is further described below in connection with preferred examples. It should be understood by those skilled in the art that the following specific description is illustrative and not limiting, and is not intended to limit the protection scope of the present invention.

[0034] All numerical indications in the present invention (e.g., temperature, time, concentration, weight, and the like, including the range of each of these) may generally be approximated by varying, (+) or (), in an appropriate increment of 0.1 or 1.0. All numerical indications are understood to be represented as they are preceded by the term approximately.

Example 1

[0035] In this example, separation and recovery of boron trifluoride and its complexes in an olefin polymerization reaction were carried out, which specifically comprises the following steps.

[0036] Polymerization Reaction:

[0037] 1-octene was used as a raw material, and the catalyst was a complex of BF.sub.3 and isopropanol as a complexing agent. The amount of catalyst used was 4 wt %. The raw material 1-octene and the catalyst were placed in a reaction kettle and mixed with stirring, followed by the introduction of gaseous BF.sub.3 to conduct a reaction at constantly 0.5 MPa, where the reaction temperature was 40 C. and the reaction duration was 3 h.

[0038] Separation and recovery of boron trifluoride and its complex:

[0039] After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled for 1 min at a flash distillation pressure of 1 kPa and a flash distillation temperature of 120 C. The dissolved BF.sub.3 gas in the polymerization intermediate product was removed, and this portion of gaseous BF.sub.3 was pressurized by a compressor and recycled to the reaction system for reuse.

[0040] The intermediate product after flash distillation then entered a membrane separation device at a rate of 0.01 m.sup.3/h for the separation of the complex catalyst, at a separation pressure of 1 MPa and a separation temperature of 50 C. The material used for membrane separation was a polyvinylidene fluoride membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst. The extraction was carried out by using 2-methylundecane as an extractant at a volume ratio of 1:1, and the purified complex upon further separation could be reused.

[0041] The intermediate product from which the complex catalyst was removed was subjected to separation by gas stripping for 10 min at a gas stripping temperature of 120 C. and a volume ratio of 50:1 of the gas (inert gas such as nitrogen) to the intermediate product for gas stripping, so as to further remove the remaining gaseous BF.sub.3 dissolved in the polymerization intermediate product. The BF.sub.3 separated by gas stripping was absorbed with water at a complexation temperature of 25 C. After the gas stripping separation, a final polymerization product was obtained, with a fluorine content measured to be less than 10 ppm, and a rate of separation and recovery of boron trifluoride and its complex of more than 99%. The recovery is calculated as follows: recovery (%)=(F.sub.1F.sub.2)/F.sub.1, where F.sub.1 is the fluorine content in boron trifluoride and its complex in the olefin polymerization reaction, and F.sub.2 is the fluorine content in the product of the olefin polymerization reaction, and the same applies in the following examples.

Example 2

[0042] In this example, separation and recovery of boron trifluoride and its complexes in an olefin polymerization reaction were carried out, which specifically comprises the following steps.

[0043] The procedure of the polymerization reaction was the same as that in Example 1. After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled for 60 min at a flash distillation pressure of 50 kPa and a flash distillation temperature of 5 C. The dissolved BF.sub.3 gas in the polymerization intermediate product was removed, and this portion of gaseous BF.sub.3 was pressurized by a compressor and recycled to the reaction system for reuse.

[0044] The intermediate product after flash distillation then entered a membrane separation device at a rate of 5 m.sup.3/h for the separation of the complex catalyst, at a separation pressure of 0.1 MPa and a separation temperature of 5 C. The material used for membrane separation was a polyvinylidene fluoride membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst. The extraction was carried out by using 2-methylundecane as an extractant at a volume ratio of 5:1, and the purified complex upon further separation could be reused.

[0045] The polymerization intermediate product from which the complex catalyst was removed was subjected to separation by gas stripping for 60 min at a gas stripping temperature of 5 C. and a volume ratio of 1:1 of the gas (inert gas such as nitrogen) to the intermediate product for gas stripping, so as to further remove the remaining gaseous BF.sub.3 dissolved in the polymerization intermediate product. The BF.sub.3 separated by gas stripping was absorbed with isopropanol as complexing agent at a complexation temperature of 30 C. After the gas stripping separation, a final polymerization product was obtained, with a fluorine content measured to be less than 10 ppm, and a rate of separation and recovery of boron trifluoride and its complex of more than 99%.

Example 3

[0046] In this example, separation and recovery of boron trifluoride and its complexes in an olefin polymerization reaction were carried out, which specifically comprises the following steps.

[0047] The procedure of the polymerization reaction was the same as that in Example 1.

[0048] Separation and recovery of boron trifluoride and complex thereof:

[0049] After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled for 30 min at a flash distillation pressure of 101 kPa and a flash distillation temperature of 60 C. The dissolved BF.sub.3 gas in the polymerization intermediate product was removed, and this portion of gaseous BF.sub.3 was pressurized by a compressor and recycled to the reaction system for reuse.

[0050] The intermediate product after flash distillation then entered a membrane separation device at a rate of 2.5 m.sup.3/h for the separation of the complex catalyst, at a membrane separation pressure of 0.5 MPa and a separation temperature of 25 C. The material used for membrane separation was a polytetrafluoroethylene membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst. The extraction was carried out by using 2-methylundecane as an extractant at a volume ratio of 10:1, and the purified complex upon further separation could be reused.

[0051] The polymerization intermediate product from which the complex catalyst was removed was subjected to separation by gas stripping for 30 min at a gas stripping temperature of 80 C. and a volume ratio of 10:1 of the gas (inert gas such as nitrogen) to the intermediate product for gas stripping, so as to further remove the remaining gaseous BF.sub.3 dissolved in the polymerization intermediate product. The BF.sub.3 separated by gas stripping was absorbed with isopropanol at a complexation temperature of 10 C. After the gas stripping separation, a final product was obtained, with a fluorine content measured to be less than 10 ppm, and a rate of separation and recovery of boron trifluoride and its complex of more than 99%.

Example 4

[0052] In this example, separation and recovery of boron trifluoride and its complexes in an olefin polymerization reaction were carried out, which specifically comprises the following steps.

[0053] The procedure of the polymerization reaction was the same as that in Example 1.

[0054] Separation and recovery of boron trifluoride and complex thereof:

[0055] After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled at a flash distillation pressure of 20 kPa and a flash distillation temperature of 100 C. to remove the dissolved BF.sub.3 gas in the polymerization intermediate product, and this portion of gaseous BF.sub.3 was pressurized by a compressor and recycled to the reaction system for reuse.

[0056] The intermediate product after flash distillation then entered a membrane separation device at a rate of 2.0 m.sup.3/h for the separation of the complex catalyst, at a membrane separation pressure of 1.0 MPa and a separation temperature of 30 C. The material used for membrane separation was a polytetrafluoroethylene membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst.

[0057] The intermediate product from which the complex catalyst was removed was subjected to separation by gas stripping for 20 min at a gas stripping temperature of 80 C. and a volume ratio of 10:1 of the gas (inert gas such as nitrogen) to the intermediate product for gas stripping, so as to further remove the remaining gaseous BF.sub.3 dissolved in the polymerization intermediate product. The BF.sub.3 separated by gas stripping was absorbed with water at a complexation temperature of 5 C. After the gas stripping separation, a final polymerization product was obtained, with a fluorine content measured to be less than 10 ppm, and a rate of separation and recovery of boron trifluoride and its complex of more than 99%.

Example 5

[0058] In this example, separation and recovery of boron trifluoride and its complexes in an olefin polymerization reaction were carried out, which specifically comprises the following steps.

[0059] The procedure of the polymerization reaction was the same as that in Example 1.

[0060] Separation and recovery of boron trifluoride and complex thereof:

[0061] After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled at a flash distillation pressure of 30 kPa and a flash distillation temperature of 70 C. to remove the dissolved BF.sub.3 gas in the polymerization intermediate product, and this portion of gaseous BF.sub.3 was pressurized by a compressor and recycled to the reaction system for reuse.

[0062] The intermediate product after flash distillation then entered a membrane separation device at a rate of 1.0 m.sup.3/h for the separation of the complex catalyst, at a membrane separation pressure of 0.8 MPa and a separation temperature of 35 C. The material used for membrane separation was a polytetrafluoroethylene membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst.

[0063] The intermediate product from which the complex catalyst was removed was subjected to separation by gas stripping for 30 min at a gas stripping temperature of 60 C. and a volume ratio of 30:1 of the gas (inert gas such as nitrogen) to the intermediate product for gas stripping, so as to further remove the remaining gaseous BF.sub.3 dissolved in the polymerization intermediate product. The BF.sub.3 separated by gas stripping was absorbed with water at a complexation temperature of 5 C. After the gas stripping separation, a final polymerization product was obtained, with a fluorine content measured to be less than 10 ppm, and a rate of separation and recovery of boron trifluoride and its complex of more than 99%.

Example 6

[0064] In this example, separation and recovery of boron trifluoride and its complexes in an olefin polymerization reaction were carried out, which specifically comprises the following steps.

[0065] The procedure of the polymerization reaction was the same as that in Example 1.

[0066] Separation and recovery of boron trifluoride and complex thereof:

[0067] After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled at a flash distillation pressure of 80 kPa and a flash distillation temperature of 50 C. to remove the dissolved BF.sub.3 gas in the polymerization intermediate product, and this portion of gaseous BF.sub.3 was pressurized by a compressor and recycled to the reaction system for reuse.

[0068] The intermediate product after flash distillation then entered a membrane separation device at a rate of 2.0 m.sup.3/h for the separation of the complex catalyst, at a membrane separation pressure of 0.6 MPa and a separation temperature of 40 C. The material used for membrane separation was a polytetrafluoroethylene membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst.

[0069] The intermediate product from which the complex catalyst was removed was subjected to separation by gas stripping for 40 min at a gas stripping temperature of 70 C. and a volume ratio of 40:1 of the gas (inert gas such as nitrogen) to the intermediate product for gas stripping, so as to further remove the remaining gaseous BF.sub.3 dissolved in the polymerization intermediate product. The BF.sub.3 separated by gas stripping was absorbed with water at a complexation temperature of 10 C. After the gas stripping separation, a final polymerization product was obtained, with a fluorine content measured to be less than 10 ppm, and a rate of separation and recovery of boron trifluoride and its complex of more than 99%.

[0070] The BF.sub.3 and its complexes separated and recovered in Examples 1 to 6 were recovered and used for polymerization reaction, and the reaction effects were comparable to that before recovery. The results for comparison are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Kinematic Pour viscosity Pentamer point (mm.sup.2/s) Viscosity Mononer Dimer Trimer Tetramer and higher Conversion Catalysts ( C.) 100 C. 40 C. index (wt %) (wt %) (wt %) (wt %) (wt %) rate (%) Fresh 53 4.33 19.43 134 0.6 3.8 55.7 26.0 14 99.4 Recovered 54 4.29 18.18 133 0.8 4.2 56.4 26.2 12.5 99.2 Example 1 Recovered 53 4.32 19.34 134 0.5 3.5 56.1 26.1 13.8 99.5 Example 2 Recovered 53 4.33 19.41 134 0.9 4.6 54.3 25.3 14.9 99.1 Example 3 Recovered 54 4.42 19.86 135 0.2 3.9 57.3 22.5 16.1 99.8 Example 4 Recovered 53 4.27 18.69 136 1.0 4.8 55.3 24.3 14.6 99.0 Example 5 Recovered 54 4.43 19.69 138 0.7 5.3 57.8 22.6 13.6 99.3 Example 6

Comparative Example 1

[0071] The procedure of the polymerization reaction was the same as that in Example 1. After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled for 40 minutes at a flash distillation pressure of 60 kPa and a flash distillation temperature of 90 C. Analysis was conducted on the intermediate product, and the rate of removal of boron trifluoride and its complex is 20%.

Comparative Example 2

[0072] The procedure of the polymerization reaction was the same as that in Example 1. After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled for 40 minutes at a flash distillation pressure of 60 kPa and a flash distillation temperature of 90 C.

[0073] The intermediate product after flash distillation then entered a membrane separation device at a rate of 3.0 m.sup.3/h for the separation of the complex catalyst, at a membrane separation pressure of 0.8 MPa and a separation temperature of 35 C. The material used for membrane separation was a polyvinylidene fluoride membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst. The extraction was carried out by using 2-methylundecane as an extractant at a volume ratio of 1:1, and the purified complex upon further separation could be reused.

[0074] The intermediate product from which the complex catalyst had been removed was analyzed, and the removal rate of boron trifluoride and its complex was 68%. In addition, the performance of the recovered catalyst was evaluated, and the results of the compositional analysis of the product showed a significant increase in the content of higher polymers in the product (up to 37.6% for pentamer and higher polymers) and a decrease in the yield of the target product.

Comparative Example 3

[0075] The procedure of the polymerization reaction was the same as that in Example 1.

[0076] After the polymerization reaction was completed, the polymerization intermediate product containing boron trifluoride and its complex was pumped into a flash distillation tank and flash distilled for 40 minutes at a flash distillation pressure of 60 kPa and a flash distillation temperature of 90 C.

[0077] The intermediate product after flash distillation then entered a membrane separation device at a rate of 3.0 m.sup.3/h for the separation of the complex catalyst, at a membrane separation pressure of 1.0 MPa and a separation temperature of 30 C. The material used for membrane separation was a polytetrafluoroethylene membrane. The output of the membrane separation device was the intermediate product from which the complex catalyst was removed, and the bottom output was the separated complex catalyst. The extraction was carried out by using 2-methylundecane as an extractant at a volume ratio of 1:1, and the purified complex upon further separation could be reused. The output of the polymerization device was the intermediate product from which the complex catalyst was removed, and upon analysis of the intermediate product the removal rate of boron trifluoride and its complex was 80%.

Comparative Example 4

[0078] The procedure of the polymerization reaction was the same as that in Example 1.

[0079] After the polymerization reaction was completed, the BF.sub.3 complexes were separated and recovered by using a flash distillation/settling process. After flash distillation of the polymerized product, the liquid portion entered the settling equipment to obtain a complex which was recovered, while the gaseous product at the top of the flash distillation tank was absorbed by isopropanol. Through extensive process test verification, the results show that the best result of complex removal from the oil product was 58%, which still cannot meet the requirement of F content of catalyst in the subsequent hydrogenation process.

[0080] The data for comparison of the complex removal rate and the profile of the polymerization product composition obtained by recycling the catalyst in the examples and comparative examples are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Pentamer Complex Mononer Dimer Trimer Tetramer and higher Conversion removal Examples (wt %) (wt %) (wt %) (wt %) (wt %) rate (%) rate (%) Example 1 0.8 4.2 56.4 26.2 12.5 99.2 >99 Example 2 0.5 3.5 56.1 26.1 13.8 99.5 >99 Example 3 0.9 4.6 54.3 25.3 14.9 99.1 >99 Example 4 0.2 3.9 57.3 22.5 16.1 99.8 >99 Example 5 1.0 4.8 55.3 24.3 14.6 99.0 >99 Example 6 0.7 5.3 57.8 22.6 13.6 99.3 >99 Comparative 20 Example 1 Comparative 1.6 5.3 25.2 30.3 37.6 98.4 68 Example 2 Comparative 1.2 6.3 38.9 26.4 27.2 98.8 80 Example 3 Comparative 1.5 5.9 36.9 24.9 31.2 98.8 58 Example 4

[0081] By comparison, it can be seen that, as shown in the test results of Comparative Example 1, in the case of the catalyst removal from the oil product by flash distillation process only, the removal rate is only 20%, which is poor in terms of the removal efficiency. As shown in the test results of Comparative Example 2, in the case of catalyst removal from oils by flash distillation/membrane separation processes, in which the membrane separation equipment used was a self-designed membrane separation device and polyvinylidene fluoride was chosen as the membrane material, the removal rate is 68%; at the same time, the product composition profile changes drastically, with a significant increase in the number of pentamer and higher polymers. As shown in the test results of Comparative Example 3, in the case of catalyst removal from the oil product by flash distillation/membrane separation processes, in which polytetrafluoroethylene was chosen as the membrane material, the removal rate is 80%.

[0082] The above examples of the present invention are clearly only exemplification for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For a person of ordinary skill in the art, other variations or changes in different forms can be made on the basis of the above description. The embodiments herein are not meant to be exhaustive, and any apparent variations or changes derived from the technical solutions of the present invention are still within the protection scope of the present invention.