Method for removing chlorinated hydrocarbon impurities in fluorine-containing olefin

Abstract

The invention provides a method for removing chlorinated hydrocarbon impurities in fluorine-containing olefin, which comprises the following steps: after the fluorine-containing olefin is adsorbed by an adsorbent, at least 99% of chlorinated hydrocarbon impurities are removed; wherein the adsorbent is zeolite. Through a reasonable design scheme, the adsorbent singly and efficiently adsorbs chlorinated hydrocarbon impurities, and does not adsorb other substances.

Description

Technical Field

[0001] The present application relates to a method for removing chlorinated hydrocarbon impurities from fluoroolefins. Background Art

[0002] Substances such as chlorofluorocarbons and halons used in industrial production and use, when released into the atmosphere and rising to the stratosphere, are decomposed into Cl· free radicals or Br· free radicals under the irradiation of ultraviolet light. These free radicals quickly carry out chain reactions with ozone, destroying the ozone layer. These substances that damage the atmospheric ozone layer are called "ozone-depleting substances (ODS)", and their destructive power to the atmospheric ozone layer is called the ozone depletion potential (ODP).

[0003] CFCs and HCFCs belong to ODS chlorofluorocarbons. CFCs have been globally prohibited from production due to their extremely high ODP, while HCFCs have been widely used as substitutes for CFCs in fields such as refrigeration, foaming, and cleaning for a period of time, alleviating the damage of CFCs to the ozone layer to a certain extent. However, HCFCs still contain Cl atoms and cannot fundamentally prevent their damage to the ozone layer.

[0004] However, organofluorine compounds containing chlorine are still common in the fluorochemical industry for the production of (ODS) substitutes, including the production of the latest generation of HFOs. However, the current fluoroolefins contain a lot of chlorinated hydrocarbon impurities or introduce new impurities. With the tightening of environmental protection regulations around the world, the restrictions on chlorinated saturated hydrocarbon compounds in HFOs products have reached an extremely stringent level. Due to the large difference in volatility between these chlorofluorocarbons and most ODS substitutes, a large amount of chlorofluorocarbon impurities can usually be removed through a distillation process. However, considering that some chlorofluorocarbons form azeotropes and it is difficult to completely remove chlorofluorocarbons only through the distillation process, it is necessary to develop new technical means to meet the above requirements. Summary of the Invention

[0005] To solve the above problems, the present application provides the following solution: A method for removing chlorinated hydrocarbon impurities from fluoroolefins, which includes the following steps:

[0006] After the fluoroolefin is adsorbed by an adsorbent, at least 99% of the chlorinated hydrocarbon impurities are removed; wherein the adsorbent is zeolite.

[0007] In some embodiments of the present application, the adsorbent is pretreated as follows before adsorption:

[0008] The adsorbent is dried in an inert gas and then calcined, wherein the calcination temperature is higher than the drying temperature.

[0009] In some embodiments of the present application, the adsorption temperature for adsorption is -40 to 20 °C, preferably -40 to -20 °C.

[0010] In some embodiments of the present application, the adsorption pressure for adsorption is -0.1 to 0.3 Mpa, preferably 0 to 0.1 Mpa.

[0011] In some embodiments of the present application, the adsorption method for adsorption is static adsorption or cyclic adsorption;

[0012] Preferably,

[0013] the time for the static adsorption is 6 to 24 h; or,

[0014] the time for the cyclic adsorption is 2 to 12 h.

[0015] In some embodiments of the present application, the temperature for drying is 80 to 250 °C, and the time for drying is 0.1 to 10 hours;

[0016] Preferably,

[0017] the temperature for drying is 100 to 200 °C, and the time for drying is 1 to 8 hours.

[0018] In some embodiments of the present application, the temperature for calcination is 150 to 600 °C, and the time for calcination is 4 to 25 hours;

[0019] Preferably,

[0020] the temperature for calcination is 200 to 350 °C, and the time for calcination is 6 to 12 hours.

[0021] In some embodiments of the present application, the pore diameter of the zeolite is 5 to 15 Å, preferably 6 to 10 Å.

[0022] In some embodiments of the present application, the silica-alumina ratio of the zeolite is 1 to 60, preferably 3 to 15, or,

[0023] the particle size of the zeolite is 1.5 to 3 mm.

[0024] In some embodiments of the present application, the zeolite is prepared from sodium silicate, sodium metaaluminate, and sodium hydroxide.

[0025] Compared with the prior art, the beneficial effects of the present application are:

[0026] The present application provides an adsorption method for efficiently removing chlorinated hydrocarbon impurities in HFOs. After HFOs contact with the zeolite, more than 99% of the chlorinated hydrocarbon impurities can be removed, the yield is greater than 90%, and the operation can be carried out economically and safely.

[0027] Through a reasonable design solution, the adsorbent in this application adsorbs chlorinated hydrocarbon impurities solely and efficiently without adsorbing other substances.

[0028] The process of this application is reasonable, simple, stable, reliable and easy to operate; it has a large adsorption capacity for fluorochlorinated organic impurities in fluorinated organic compounds and a high removal efficiency. The adsorbent used in this application produces few by-products and is easy to regenerate, making it suitable for large-scale industrial production. Specific Embodiments

[0029] The following further illustrates this application with reference to embodiments. It should be understood that the embodiments are only used to further illustrate and explain this application and are not used to limit this application.

[0030] Unless otherwise defined, the technical and scientific terms in this specification have the same meanings as those commonly understood by those skilled in the art. Although methods and materials similar or identical to those described herein can be used in experiments or practical applications, the materials and methods are still described below. In case of conflict, this specification, including its definitions, shall prevail. Additionally, the materials, methods and examples are for illustrative purposes only and are not restrictive. The following further illustrates this application with specific embodiments, but does not limit the scope of this application.

[0031] This application provides a method for removing chlorinated hydrocarbon impurities in fluorinated olefins, which includes the following steps: after the fluorinated olefins are adsorbed by the adsorbent, at least 99% of the chlorinated hydrocarbon impurities are removed; the adsorbent is zeolite.

[0032] In some embodiments of this application, the adsorption temperature used for adsorption is -40 to 20°C, preferably -40 to -20°C. For example, the adsorption temperature used for adsorption can be -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C or any range therebetween.

[0033] In some embodiments of the present application, the adsorption pressure used for adsorption is -0.1 to 0.3 Mpa, preferably 0 to 0.1 Mpa. For example, the adsorption pressure used for adsorption can be -0.1 Mpa, 0 Mpa, 0.01 Mpa, 0.02 Mpa, 0.03 Mpa, 0.04 Mpa, 0.05 Mpa, 0.06 Mpa, 0.07 Mpa, 0.08 Mpa, 0.09 Mpa, 0.1 Mpa, 0.11 Mpa, 0.12 Mpa, 0.13 Mpa, 0.14 Mpa, 0.15 Mpa, 0.16 Mpa, 0.17 Mpa, 0.18 Mpa, 0.19 Mpa, 0.2 Mpa, 0.21 Mpa, 0.22 Mpa, 0.23 Mpa, 0.24 Mpa, 0.25 Mpa, 0.26 Mpa, 0.27 Mpa, 0.28 Mpa, 0.29 Mpa, 0.3 Mpa or any range therebetween.

[0034] In some embodiments of the present application, the adsorption method used for adsorption is static adsorption or cyclic adsorption.

[0035] In some embodiments of the present application, the time for static adsorption is 6 to 24 h; for example, the time for static adsorption can be 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h or any range therebetween.

[0036] In some embodiments of the present application, the time for cyclic adsorption is 2 to 12 h; for example, the time for cyclic adsorption can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h or any range therebetween.

[0037] In some embodiments of the present application, the adsorbent is pretreated as follows before adsorption: the adsorbent is dried in an inert gas and then calcined, wherein the calcination temperature is higher than the drying temperature.

[0038] In some embodiments of the present application, the drying temperature is 80~250°C, and the drying time is 0.1~10 hours; preferably, the drying temperature is 100~200°C, and the drying time is 1~8 hours. For example, the drying temperature can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C or any range therebetween; the drying time can be 0.1 hour, 0.5 hour, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 8 hours, 9.5 hours, 10 hours or any range therebetween.

[0039] In some embodiments of the present application, the calcination temperature is 150~600°C, and the calcination time is 4~25 hours; preferably, the calcination temperature is 200~350°C, and the calcination time is 6~12 hours. For example, the calcination temperature can be 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C or any range therebetween; for example, the calcination time can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours or any range therebetween.

[0040] In some embodiments of the present application, the pore diameter of the zeolite is 5~15 Å, preferably 6~10 Å. For example, the pore diameter of the zeolite can be 5 Å, 6 Å, 7 Å, 8 Å, 9 Å, 10 Å, 11 Å, 12 Å, 13 Å, 14 Å, 15 Å or any range therebetween.

[0041] In the present application, the method for detecting the pore diameter of the zeolite is as follows: using a specific surface area analyzer (BET), testing by the static nitrogen adsorption method.

[0042] In some embodiments of the present application, the silica-alumina ratio of the zeolite is 1~60, preferably 5~30. For example, the silica-alumina ratio of the zeolite can be 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or any range therebetween.

[0043] In this application, the silica-alumina ratio of the zeolite is tested by an X-ray diffractometer (XRD), and the specific silica-alumina ratio is calculated by measuring the unit cell parameters of the zeolite.

[0044] In some embodiments of this application, the particle size of the zeolite is 1.5 - 3 mm. For example, the particle size of the zeolite can be 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm or any range therebetween.

[0045] In this application, the method for measuring the particle size of the zeolite is based on the test method in GB / T 6288 - 2021.

[0046] In some embodiments of this application, the zeolite is prepared from sodium silicate, sodium aluminate, and sodium hydroxide.

[0047] In some embodiments of this application, a certain amount of Na2CO3 and NaOH are accurately weighed and added into a polytetrafluoroethylene cup, then a certain amount of NaAlO2 solution and distilled water are added. An appropriate amount of powdered X-type zeolite molecular sieve is placed in a magnetic stirrer and stirred at a certain temperature for three times. Then, after washing, drying, and calcining, the target zeolite is obtained.

[0048] In this application, a fluoroolefin refers to a compound containing at least one carbon atom, one fluorine atom (including but not limited to consisting only of carbon and fluorine atoms), and at least one carbon-carbon double bond; specifically, a compound having the formula E- or Z-R 1 CH=CHR 2 structure, where each R 1 and R 2 is a perfluoroalkyl group, and the perfluoroalkyl groups are independently selected from CF3, C2F5, n-C3F7, i-C3F7, n-C4F9, i-C4F9, and t-C4F9, and where R 2 can be F.

[0049] In this application, fluoroolefins are also called HFOs. This application does not make any limitations on the types and sources of HFOs, and they can be synthesized by oneself or purchased commercially. Among them, HFOs are selected from any one of HFO-1234ze(E), HFO-1234yf, 1,2,3,3,3-pentafluoropropene (HFO-1225ye), and 2,3,3,4,4,4-hexafluoro-1-butene (HFO-1336yf).

[0050] In this application, chlorinated hydrocarbon impurities refer to hydrocarbons in which at least one H atom of "chlorinated hydrocarbon" is replaced by Cl; examples of chlorinated hydrocarbons are intended to include, without limitation, dichloromethane, chloroform, carbon tetrachloride, and dichloroethane. Dichloromethane is also known as DCM or CH2Cl2.

[0051] Through reasonable design schemes in this application, such as the selection of the silica-alumina ratio of the adsorbent, the size of the pore diameter, the drying and calcination treatment of the adsorbent before adsorption, the adsorption temperature, the adsorption pressure, the optimization of the adsorption method, etc., the adsorbent can adsorb chlorinated hydrocarbon impurities singly and efficiently without adsorbing other substances.

[0052] Preparation Example 1 Preparation of Zeolite

[0053] Accurately weigh a certain amount of Na2CO3 and NaOH and add them to a polytetrafluoroethylene cup. Then add a certain amount of NaAlO2 solution and distilled water to make a 150 mL solution. The concentration of Na2CO3 is 0.8 mol / L, and the concentration of NaOH is 0.3 mol / L (pH value is 13). Weigh 5 g of powder X-type zeolite molecular sieve and place it in a magnetic stirrer. Stir at 80 °C for 4 h and perform the treatment three times. Then, after washing, drying, and calcination, the target zeolite is obtained.

[0054] After testing: The pore diameter of the target zeolite is 7 Å, the silica-alumina ratio is 10, and the particle size is 3 mm.

[0055] The pore diameter is measured by BET using the nitrogen static adsorption method.

[0056] The silica-alumina ratio is calculated by XRD through measuring the unit cell parameters.

[0057] The measuring method of the particle size is tested according to GB / T 6288-2021.

[0058] Examples

[0059] Example 1

[0060] Load 100 g of the zeolite in Preparation Example 1 into the adsorption column, pass nitrogen to dry at 150 °C for 2 h, heat up to 300 °C and calcine for 12 h. After cooling, perform adsorption at 20 °C and 0 Mpa. Pass 200 g into the adsorption column, sample and test after static adsorption for 12 h, collect the adsorbed material, weigh and calculate the yield.

[0061] Among them, before adsorption the purity of the fluorinated olefin is 99.80%, C4F8HCl is 1245 ppm, C4F8Cl2 is 620 ppm, C4F6H2Cl is 115 ppm, and C4F7H is 20 ppm.

[0062] The difference between Example 2-13 and Comparative Examples 1-2 lies only in Table 1, and the rest is the same as Example 1.

[0063] In the commercial 3A molecular sieve in Comparative Example 1, the pore diameter is 3 Å and the silica-alumina ratio is 2.

[0064] In the commercial ZSM molecular sieve in Comparative Example 2, the pore diameter is 5 Å and the silica-alumina ratio is 100.

[0065] Table 1

[0066]

[0067] For Examples 1-13 and Comparative Examples 1-2, the content of fluorochlorocarbon impurities and the analysis results of organic purity are shown in Table 2. In addition, for those before storage, the content of fluorochlorocarbon impurities and the analysis results of organic purity are shown in Table 2. The purity and impurity content were analyzed by GC-FID and obtained by the peak area normalization method.

[0068] Table 2

[0069]

[0070] According to the above analysis results, it can be seen that the molecular sieve has little adsorption capacity for impurities such as C4F7H without chlorine. From Comparative Examples 1 and 2, it can be known that molecular sieves with inappropriate pore diameters and silica-alumina ratios have no significant effect on removing fluorochlorocarbon impurities. In Examples 1 to 5, it was observed that temperature and adsorption time had a significant impact on the removal effect of fluorochlorocarbon impurities. The lower the adsorption temperature, the higher the organic purity, but when the temperature is low to a certain extent, it has no significant impact on the adsorption effect, and the lower the temperature, the greater the energy consumption. The form of static or cyclic adsorption has little impact on the adsorption effect. Examples 6-9 show that increasing the adsorption pressure and adsorption time is beneficial to improving the adsorption effect, but when increased to a certain extent, the adsorption effect is not significantly improved, and the energy consumption increases, increasing the production cost. Examples 12 and 13 show that the pretreatment of the adsorbent directly determines the adsorption effect. From Examples 4, 14-16, it can be seen that the value of the silica-alumina ratio has an important impact on the removal of specific fluorochlorocarbon impurities.

[0071] Example 17

[0072] Load 100 g of the zeolite in Preparation Example 1 into the adsorption column, dry it with nitrogen at 150 °C for 2 h, heat it to 300 °C and calcine it for 12 h. After cooling, carry out adsorption at 20 °C and 0 Mpa, and use 200 g It was introduced into the adsorption column, and after standing for adsorption for 12 h, samples were taken for testing. The materials after adsorption were collected, weighed, and the yield was calculated.

[0073] Among them, before adsorption the purity of the fluoroolefin was 99.84%, C3H3F4Cl-1 was 861 ppm, C3H2F4Cl2 was 423 ppm, C3H3F4Cl-2 was 256 ppm, and Z-1234ze was 33 ppm. Z-1234ze refers to cis-1,3,3,3-tetrafluoropropene.

[0074] The differences between Examples 17-32 and Comparative Examples 3-4 were only in Table 3, and the rest were the same as in Example 14.

[0075] In the commercial 3A molecular sieve in Comparative Example 3, the pore diameter was 3 Å and the silica-alumina ratio was 2.

[0076] In the commercial ZSM molecular sieve in Comparative Example 4, the pore diameter was 5 Å and the silica-alumina ratio was 100.

[0077] Table 3

[0078]

[0079] For Examples 17 to 32 and Comparative Examples 3 to 4, the contents of the fluorochlorocarbon impurities and the analysis results of the organic purity are shown in Table 4. The purity and the impurity content were analyzed by GC-FID and obtained by the peak area normalization method.

[0080] Table 4

[0081]

[0082] According to the above analysis results, it can be seen that the molecular sieve has almost no adsorption capacity for the chlorine-free impurity Z-1234ze. From Comparative Examples 3 and 4, it can be known that the molecular sieves with inappropriate pore diameters and silica-alumina ratios have no significant effect on removing fluorochlorocarbon impurities. In Examples 17-20 and Examples 22-23, it was observed that the temperature and the adsorption pressure had a significant effect on the removal effect of the fluorochlorocarbon impurities. The lower the temperature and the higher the pressure, the higher the organic purity. However, the form of static or cyclic adsorption had little effect on the adsorption effect. But when the temperature was low to a certain extent, there was no significant effect on the adsorption effect, and the lower the temperature, the greater the energy consumption. Moreover, when the pressure increased to a certain extent, the adsorption effect did not increase significantly, and the energy consumption increased, increasing the production cost. Examples 28-29 demonstrated the necessity of the pretreatment of the adsorbent. The adsorbent without pretreatment had almost no adsorption effect. From Examples 20, 30-32, it can be seen that the value of the silica-alumina ratio had an important influence on the removal of specific fluorochlorocarbon impurities.

[0083] Although the present case has been disclosed above by way of examples, it is not intended to limit the present case. Any person having ordinary knowledge in the relevant technical field may make some modifications and refinements without departing from the spirit and scope of the present case. Therefore, the scope of protection of the present case shall be subject to that defined by the appended patent application scope.

Claims

1. A method for removing chlorinated hydrocarbon impurities from fluorinated olefins, comprising the following steps: After the fluorinated olefin is adsorbed by the adsorbent, at least 99% of the chlorinated hydrocarbon impurities are removed; the adsorbent is zeolite.

2. The method according to claim 1, wherein: The adsorbent is pre-treated as follows before adsorption: The adsorbent is dried in an inert gas and then calcined, wherein the calcination temperature is higher than the drying temperature.

3. The method according to claim 1 or 2, wherein: The adsorption temperature used for adsorption is -40~20℃.

4. The method according to claim 3, wherein: The adsorption temperature used for adsorption is -40~-20℃.

5. The method according to claim 1 or 2, wherein: The adsorption pressure used for adsorption is -0.1~0.3Mpa.

6. The method according to claim 5, wherein: The adsorption pressure used for adsorption is 0~0.1Mpa.

7. The method according to claim 1 or 2, wherein: The adsorption method used in adsorption is static adsorption or cyclic adsorption; or, The static adsorption time is 6 to 24 hours; or, The cyclic adsorption time is 2 to 12 hours.

8. The method according to claim 2, wherein: The drying temperature is 100-200° C., and the drying time is 1-8 hours.

9. The method according to claim 2, wherein: The calcination temperature is 200-350° C., and the calcination time is 6-12 hours.

10. The method according to claim 1, wherein: The pore size of the zeolite is 5-15Å.

11. The method according to claim 10, wherein: The pore size of the zeolite is 6-10 Å.

12. The method according to claim 1, wherein: The silicon-aluminum ratio of the zeolite is 1 to 60, or The particle size of the zeolite is 1.5-3 mm.

13. The method according to claim 1, wherein: The silicon-to-aluminum ratio of the zeolite is 3-15.

14. The method according to claim 1, wherein: The zeolite is prepared from water glass, sodium aluminate and sodium hydroxide.

Images