PROCESS FOR PURIFYING (HYDRO)FLUOROPROPENES CONTAMINATED WITH HALOGENATED ETHANE

Abstract

A process for treating a composition comprising one or more desired (hydro)fluoroolefins and one or more undesired halogenated ethanes, halogenated methanes or mixtures thereof so as to reduce the concentration of at least one undesired halogenated ethane or halogenated methane, the process comprising contacting the composition with an adsorbent comprising pores having openings which have a size across their largest dimension of about 6 or less.

Claims

1. A process for treating a composition comprising one or more desired (hydro)fluoropropenes and one or more undesired halogenated ethanes, so as to reduce the concentration of at least one undesired halogenated ethane the process comprising contacting the composition with an adsorbent comprising pores having openings which have a size across their largest dimension of about 6 or less.

2. A process according to claim 1 wherein the desired (hydro)fluoropropene comprises at least 10 wt %, for example at least 20 wt %, at least 30 wt %, at least 40 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt % or at least 90 wt % of the composition to be treated.

3. A process according to claim 1 or claim 2 wherein the adsorbent comprises having openings which have a size across their largest dimension of from about 4 to about 6 .

4. A process according to any of claims 1 to 3 wherein the adsorbent comprises pores having openings which have a size across their largest dimension of about 5 .

5. A process according to any of the preceding claims wherein the adsorbent is a molecular sieve.

6. A process according to any of the preceding claims wherein the adsorbent comprises a zeolite.

7. A process according to claim 1 wherein the tetrafluoropropene is 2,3,3,3-tetrafluoropropene (1234yf).

8. A process according to any of the preceding claims wherein the at least one undesired halogenated ethane is a fluorinated ethane.

9. A process according to claim 8 wherein the fluorinated ethane is tetrafluoroethane.

10. A process according to claim 9 wherein the tetrafluoroethane is 1,1,1,2-tetrafluoroethane (134a).

11. A process according to any of the preceding claims wherein the contacting step is performed, at least in part, at a temperature of from about 0 C. to about 200 C.

12. A process according to claim 11 wherein the contacting step is performed, at least in part, at a temperature of from about 20 C. to about 100 C.

13. A process according to claim 12 wherein the contacting step is performed, at least in part, at a temperature from about 20 C. to about 60 C., preferably at a temperature of about 40 C.

14. A process according to any preceding claim wherein the contacting step is conducted at a pressure of from about 0.1 MPa to the saturation pressure.

15. A process according to any preceding claim further comprising an adsorbent treatment step prior to the contacting step.

16. A process according to claim 15 wherein the adsorbent treatment step comprises a heat treatment step comprising heating the adsorbent to a maximum temperature of at least 150 C., preferably at least 200 C.

17. A process according to claim 16 wherein the heat treatment step comprising heating the adsorbent to a maximum temperature of at least 300 C., preferably at least 400 C.

18. A process according to claim 16 or 17 wherein the heat treatment step comprises heating the adsorbent to the maximum temperature at a rate of from 1 C./minute to 100 C./minute.

19. A process according to claim 18 wherein the heat treatment step comprises heating the adsorbent to the maximum temperature at a rate of from 10 C./minute to 60 C./minute, preferably at a rate of from 20 C./minute to 40 C./minute.

20. A process according to any of claims 16 to 19 wherein the heat treatment step comprises maintaining the adsorbent at or around the maximum temperature for a time of from 1 second to 1 hour.

21. A process according to any of claims 14 to 19 wherein the adsorbent treatment step comprises an exposure step comprising exposing the adsorbent to one or more inert gases, preferably N.sub.2 or one or more noble gases.

22. A process according to claim 21 wherein the exposure step is performed before, during or after the heat treatment step.

23. A process according to any of the preceding claims wherein the process removes at least 50% by weight, preferably 90% by weight, even more preferably 98% of the undesired halogenated ethanes, halogenated methanes or mixtures thereof.

24. A process according to claim 23 wherein the process reduces the concentration of the undesired halogenated ethanes, halogenated methanes or mixtures thereof to levels at, around or below the limit of detection by gas chromatography.

25. A process according to any preceding claim wherein the adsorbent is dried before use.

26. A process according to any preceding claim wherein the moisture content of the adsorbent is less than about 1.5% by weight.

27. A process according to any of the preceding claims wherein the composition to be treated is passed, at least once, through a polishing bed containing the adsorbent.

28. A process according to claim 27 wherein the composition is passed through two or more polishing beds.

29. A process according to claim 27 or 28 wherein the polishing bed comprises a packed or fluidised bed.

30. A process according to any preceding claim wherein the composition is contacted with the adsorbent more than once.

31. A process according to any of the preceding claims further comprising a step of regenerating the adsorbent after it has been contacted with the composition.

32. A process according to claim 31 wherein the regenerating step comprises contacting the adsorbent with a heated stream of inert gas and/or heating the adsorbent whilst the or an inert gas is passed over it.

33. A process according to claim 31 or 32 wherein the regenerating step comprises subjecting the adsorbent to a change in pressure.

34. A process according to any preceding claim further comprising one or more additional purifying steps, which may be conducted before and/or after the contacting step.

35. A process according to claim 34 wherein the additional purifying step comprises the use of one or more molecular sieves, preferably wherein the one or more molecular sieves are acid stable.

36. A process according to claim 34 or 35 wherein the additional purifying step comprises the use of drying agents and/or distillation techniques.

37. A process according to any preceding claim which is carried out, at least in part, in the gas or liquid phase.

38. A method for recovering a desired component of a spent refrigerant, the method comprising removing the refrigerant from the refrigerant system and contacting the refrigerant with an adsorbent comprising pores having a size opening across their largest dimension of 6 or less to remove or reduce the concentration of one or more undesired components, the desired component comprising a (hydro)fluoropropene, the undesired component comprising a halogenated ethane.

39. A method according to claim 38 wherein the desired (hydro)fluoropropene comprises at least 10 wt %, for example at least 20 wt %, at least 30 wt %, at least 40 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt % or at least 90 wt % of the spent refrigerant.

40. A kit for recovering a desired component of a spent refrigerant, the kit comprising an apparatus comprising an adsorbent comprising pores having a size opening across their largest dimension of 6 A or less and instructions for removing the refrigerant from the refrigerant system and contacting the refrigerant with the apparatus to remove or reduce the concentration of one or more undesired components, the desired component comprising a (hydro)fluoropropene, the undesired component comprising a halogenated ethane.

41. A kit according to claim 40 wherein the desired (hydro)fluoropropene comprises at least 10 wt %, for example at least 20 wt %, at least 30 wt %, at least 40 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt % or at least 90 wt % of the refrigerant.

42. A heat transfer fluid comprising at least one desired (hydro)fluoropropene and being substantially free of an undesired halogenated methane or ethane, the at least one (hydro)fluoropropene having been purified by a method according to any of claims 1 to 37.

43. A heat transfer device comprising a heat transfer fluid comprising one or more desired (hydro)fluoropropenes and an adsorbent comprising pores having openings which have a size across their largest dimension of about 6 or less.

44. A heat transfer device according to claim 43 wherein the heat transfer device is a refrigeration system.

45. A process as substantially herein described.

Description

[0036] The present invention is now illustrated, but not limited by, the following description and Examples, with reference to the following drawings:

[0037] FIG. 1 shows a chart representing the 2 hour absorption capacity of a range of absorbent materials for each of the refrigerants R-134a, 1234yf and E-1234ze;

[0038] FIG. 2 shows a chart representing the heat of absorption for a range of absorbent materials for each of the refrigerants R-134a, 1234yf and E-1234ze.

[0039] As described above, the invention provides a method for the separation of one or more undesired halogenated ethanes and/or methanes from a composition comprising one or more desired (hydro)fluoroolefins as a major component. Such a method serves to reduce the concentration of at least one undesired halogenated ethane or halogenated methane through the retention by the absorbent of at least a portion of the halogenated ethanes and/or methanes. The process comprises contacting the composition with an adsorbent comprising pores having openings across their largest dimension of about 6 or less, preferably between 4 and 6 , (also referred to as nominal pore diameter).

[0040] A particularly preferred variety of adsorbent is a zeolite molecular sieve material preferably having a pore size across its largest dimension of approximately 5 , however alternative molecular sieve materials having similar pore dimensions may also be effective.

[0041] The use of such an adsorbent is unexpectedly selective in retaining, within the adsorbent, undesired halogenated ethanes and/or methanes from a composition comprising desired (hydro)fluoroolefins as a major component.

[0042] A composition to be treated may be contacted with a granulated solid sorbent bed comprising the adsorbent. Such a contacting step may be conducted as part of a once through process, wherein the product composition is recovered after being contacted with the adsorbent.

[0043] Alternatively, the composition to be treated may be contacted with a single granulated solid sorbent bed, comprising the adsorbent, multiple times as part of a cyclic process. In which case the sorbent may be regenerated through a change in temperature or pressure as described above, prior to the composition being re-contacted.

[0044] Twin or multi sorbent bed schemes may also be adopted in order to work the process. In two or multi bed schemes, one or more temperature changes as described above may be employed in order to regenerate the sorbent after each time the composition has been contacted with the sorbent bed. Such processes are known also as temperature-swing processes. For example, in a two bed temperature swing process, the second bed becomes operational while the first is regenerated, and vice-versa. It will be appreciated that for the process to be continuous, the regeneration time will be equal to the adsorption time so that the composition feed stream can be switched between the beds.

[0045] Alternatively, in a two or multi bed scheme, one or more pressure changes, as described above, may be employed to regenerate the sorbent after each contacting step, known also as pressure-swing processes. Similarly to temperature swing processes, the composition feed may be switched between beds. As pressure changes can typically be effected more quickly than temperature changes, cycle times can be significantly quicker than temperature swing processes.

[0046] The process of the invention may be used in preparative chromatographic separation processes.

[0047] The processes of invention may be used in numerous applications.

[0048] The invention may be employed as part of the synthesis and/or purification of desired (hydro)fluoroolefins, in order to remove unwanted by-products or impurities, such as halogenated ethanes and/or halogenated methanes that could be present in the final product.

[0049] Alternatively, the invention may be employed in order to recover and/or purify a refrigerant that has been used in a system to replace an undesired halogenated ethane or methane refrigerant.

[0050] Where the invention is used to recover and/or purify a refrigerant as previously discussed, the invention may be used in situ in the refrigeration apparatus, e.g. a mobile air-conditioning unit. Alternatively, the invention may be operated in a separate apparatus in which the composition to be treated is introduced to the apparatus.

[0051] The invention may also form part of a kit for recovering a desired component of a spent refrigerant in which the kit comprises an apparatus comprising an adsorbent comprising pores having a size opening across their largest dimension of 6 A or less, and instructions for removing the refrigerant from the refrigerant system and contacting the refrigerant with the apparatus to remove or reduce the concentration of one or more undesired components.

[0052] In a further aspect, the invention provides a heat transfer fluid comprising at least one desired (hydro)fluoroolefin as described above and being substantially free of any undesired halogenated methanes or ethanes, the at least one (hydro)fluoroolefin having been purified by a method as described above.

[0053] In another aspect, the invention provides a heat transfer device comprising a heat transfer fluid comprising one or more desired (hydro)fluoroolefins and an adsorbent comprising pores having openings which have a size across their largest dimension of about 6 or less. Preferably, the heat transfer device is a refrigeration system.

EXAMPLES

[0054] In the following Examples, industrial grade R-1234yf and R-134a was obtained from Apollo Scientific limited and Mexichem. The adsorbents were obtained from Aldrich and Chemviron.

Examples 1 to 10

[0055] The uptake of gas phase adsorbates by adsorbents in real time was measured by TGA analyser. The following adsorbents were tested: [0056] Molecular sieve 3Apores having openings which have a size across their largest dimension of about 3 ; [0057] Molecular sieve 4Apores having openings which have a size across their largest dimension of about 4 ; [0058] Molecular sieve 5Apores having openings which have a size across their largest dimension of about 5 ; [0059] Molecular sieve 13Xpores having openings which have a size across their largest dimension of about 10 ;
and Chemviron 207ea activated charcoal.

[0060] A small sample (approximately 50 mg) of each adsorbent was accurately weighed into a 100 L aluminium crucible before being loaded into the TGA furnace.

[0061] The adsorbent was first pre-treated by being equilibrated at 30 C. under nitrogen (75 mL/min) for 5 minutes, before being heated to 450 C. at 30 C./minute under flowing nitrogen (75 mL/min). The sample was held at 450 C. for 5 minutes, before being cooled to 40 C. at a rate of 30 C./minute, and being equilibrated at 40 C. for 5 minutes, all under a flow of nitrogen (75 mL/min).

[0062] The adsorbents were then exposed to 3.3% v/v refrigerant (R-1234yf or R-134a) in nitrogen (75 mL/min), at 40 C. for 120 minutes.

[0063] The results are shown in Table 1, with FIGS. 1 and 2 illustrating the capacity of the adsorbents and the heat of adsorption in each case.

[0064] As can be seen from the Table and Figures, adsorbents comprising pores having openings which have a size across their largest dimension of below about 6 , particularly between 4 and 6 , show surprising selectivity for the halogenated ethane over the (hydro)fluoroolefin. This indicates the proficiency of such adsorbents for separating halogenated ethanes from (hydro)fluoroolefins.

TABLE-US-00001 TABLE 1 Reference Wt Conc rying wt los Dry wt Wt gain Capacity Capacity Exotherm H.sub.(ads) Example Adsorbent Adsorbate (mg) (v/v) (mg) (mg) (mg) (% wt) (mol/Kg) Equilibrium (mj) (kj/mol) 1 3A 134a 58.6 3.3 9.1937 49.4063 1.6507 3.34 0.33 No 137.65 8.5 2 4A 134a 55.8 33 5.3326 50.4674 2.2154 4.39 0.43 No 239.68 11 3 5A 134a 54.2 3.3 8.1745 46.0255 5.1451 11.18 1.1 No 330.82 6.6 4 13X 134a 49.7 3.3 12.2144 37.4856 12.8923 34.39 3.37 Yes 3447.79 27.3 5 207ea 134a 34.2 3.3 0.9434 33.2566 2.5564 7.69 0.75 Yes 339.64 13.6 6 3A 1234yf 56.3 3.3 9.8521 46.4479 1.9397 4.18 0.37 No 62.18 3.3 7 4A 1234yf 53.3 3.3 10.873 42.427 2.1945 5.17 0.45 No 72.99 3.4 8 5A 1234yf 59.7 3.3 11.0719 48.6281 2.3742 4.88 0.43 No 88.19 3.8 9 13X 1234yf 47.1 3.3 11.726 35.374 10.4077 29.42 2.58 Yes 1821.33 17.8 10 207ea 1234yf 31.8 3.3 0.9976 30.8024 4.6035 14.95 1.31 Yes 699.24 15.5 indicates data missing or illegible when filed

[0065] Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

[0066] The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge