Selective separation of refrigerant mixtures using zeolites

Abstract

A process for separating components of a refrigerant mixture is provided that comprises flowing a refrigerant mixture through an acidic zeolite to form a processed refrigerant mixture, the refrigerant mixture comprising a first refrigerant component having a size d1 and a second refrigerant component having a size d2, wherein d1 > d2, the acidic zeolite having a silica to alumina ratio (SAR) of greater than 25, wherein the acidic zeolite adsorbs the first refrigerant component having the size d1 while allowing the second refrigerant component having the size d2 to break through the acidic zeolite.

Description

SELECTIVE SEPARATION OF REFRIGERANT MIXTURES USING ZEOLITESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. provisional patent application number 63 / 573,655 that was filed April 3. 2024, the entire contents of which are incorporated herein by reference.REFERENCE TO GOVERNMENT RIGHTS

[0002] This invention was made with government support under grant 2029354 awarded by the National Science Foundation. The government has certain rights in the invention.BACKGROUND

[0003] Hydrofluorocarbons (HFCs) are currently the most prevalent refrigerants in global circulation but are being phased out due to high global warming potentials (GWPs). Many countries have implemented strict regulations that either phase down or completely ban the use of many HFCs by as early as 2030. Nearly 1 billion kilograms of HFCs are currently in global use and so there is an imminent need to develop technology for reclaiming and recycling HFCs. The most prevalent fluorocarbon refrigerants are HFC mixtures that must first be separated before being recycled. However, these separations are impossible to perform using conventional industry methods due to the azeotropic nature of most refrigerants.SUMMARY

[0004] Provided are processes for separating refrigerant mixtures, e.g., an azeotropic refrigerant mixture of halocarbons, using certain zeolites. The present disclosure is based, at least in part, on the unexpected finding that certain zeolites selectively adsorb relatively large components of the refrigerant mixture to enable their separation from relatively small components under continuous flow operation, enabling the smaller components to breakthrough the zeolite and to be recovered therefrom, including at very high purities. This result is unexpected because the present processes occur under non-equilibrium conditions. Under such conditions, the slower adsorption rate of the larger component as compared to the faster adsorption rate of the smaller component was expected to prevent a viable separation.In the present disclosure, the term “adsorb” (and the like) encompasses the adherence of the refrigerant components to both the internal and external surfaces of the zeolitic structure.

[0005] The present processes and unexpected findings are demonstrated in the Example below, which describes the use of certain zeolites, e.g., silicalite- 1, H-ZSM-5, H-ZSM-11, Id- beta, and H-Y, to separate the HFC components of the near-azeotropic refrigerant mixture R- 410A by flowing R-410A through these zeolites. Specifically, it is shown that these zeolites selectively adsorb the larger pentafluoroethane (HFC-125, CHF2CF3) hydrofluorocarbon allowing the smaller difluoromethane (HFC-32, CH2F2) hydrofluorocarbon to breakthrough at unexpectedly high purities, e.g., greater than 99%. It is of particular interest to reclaim pure HFC-32 from any separation process since it can be directly recycled into next-generation refrigerant blends with hydrofluoroolefm refrigerants (e.g., R-454 composed of difluoromethane and 1,2,2,2-tetrafluoropropene).

[0006] An embodiment 1 is a process for separating components of a refrigerant mixture, the process comprising flowing a refrigerant mixture through an acidic zeolite to form a processed refrigerant mixture, the refrigerant mixture comprising a first refrigerant component having a size di and a second refrigerant component having a size d2, wherein di > d2, the acidic zeolite having a silica to alumina ratio (SAR) of greater than 25, wherein the acidic zeolite adsorbs the first refrigerant component having the size di while allowing the second refrigerant component having the size d2 to break through the acidic zeolite.

[0007] An embodiment 2 is according to embodiment 1, wherein the step of flowing the refrigerant mixture through the acidic zeolite occurs under non-equilibrium conditions.

[0008] An embodiment 3 is according to any of embodiments 1-2, wherein a difference between di and d2 is at least 0.2 A.

[0009] A embodiment 4 is according to any of embodiments 1-3, w herein a difference between di and d2 is at least 0.5 A.

[0010] An embodiment 5 is according to any of embodiments 1-4, wherein the refrigerant mixture consists of the first refrigerant component having the size di and the second refrigerant component having the size d2.

[0011] An embodiment 6 is according to any of embodiments 1-5, wherein the refrigerant mixture comprises pentafluoroethane.

[0012] An embodiment 7 is according to embodiment 6, wherein the refrigerant mixture further comprises difluoromethane.

[0013] An embodiment 8 is according to any of embodiments 1-7, wherein the refrigerant mixture consists of pentafluoroethane and difluoromethane.

[0014] An embodiment 9 is according to embodiment 8, wherein pentafluoroethane is present at 50 mass % and difluoromethane is present at 50 mass %.

[0015] An embodiment 10 is according to any of embodiments 1-9, wherein the acidic zeolite has a two-dimensional (2D) channel-type structure or a three-dimensional (3D) channel-type structure.

[0016] An embodiment 11 is according to any of embodiments 1-10, wherein the acidic zeolite has a MFI, BEA, MEL, MOR, or FAU framework structure.

[0017] An embodiment 12 is according to any of embodiments 1-11, wherein the SAR is greater than 100.

[0018] An embodiment 13 is according to any of embodiments 1-12, wherein the acidic zeolite is selected from H-ZSM-5, silicalite- 1 , H-ZSM-8, H-ZSM-11. H-beta, and H-Y.

[0019] An embodiment 14 is according to any of embodiments 1-13, wherein the process is characterized by a retention factor (RF) of at least 1.2, wherein RF is defined as a ratio of a breakthrough time of the first refrigerant component having the size di to a breakthrough time of the second refrigerant component having the size d2.

[0020] An embodiment 15 is according to any of embodiments 1-14, wherein the processed refrigerant mixture comprises a first portion comprising the second refrigerant component having the size d2 at a purity of greater than 90 mole percent.

[0021] An embodiment 16 is according to embodiment 2, wherein the refrigerant mixture comprises pentafluoroethane and difluoromethane.

[0022] An embodiment 17 is according to embodiment 16, wherein the acidic zeolite has a two-dimensional (2D) channel-type structure or a three-dimensional (3D) channel-type structure.

[0023] An embodiment 18 is according to any of embodiments 16-17, wherein the acidic zeolite is selected from H-ZSM-5, silicalite- 1 , H-ZSM-8, H-ZSM-11, H-beta, and H-Y.

[0024] An embodiment 19 is according to any of embodiments 16-18, wherein the SAR is greater than 100.

[0025] An embodiment 20 is according to any of embodiments 16-19, wherein the processed refrigerant mixture comprises a first portion comprising difluoromethane at a purity of greater than 90 mole percent

[0026] Other principal features and advantages of the disclosure will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Illustrative embodiments of the disclosure will hereafter be described with reference to the accompanying drawings.

[0028] FIGs. 1 A-1B show schematics of the MFI framework structure. FIG. 1A is a view along the

[0010] crystallographic plane. FIG. IB is a view along the

[0100] crystallographic plane.

[0029] FIG. 2 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through silicalite- 1 (SAR > 400) zeolite at 1.0 bar and 298.15 K.

[0030] FIG. 3 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-ZSM-5 zeolite (SAR=30) at 1.0 bar and 298. 15 K.

[0031] FIG. 4 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-beta zeolite (SAR=300) at 1.0 bar and 298.15 K.

[0032] FIG. 5 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-Y zeolite (SAR = 500) at 1.0 bar and 298.15 K.

[0033] FIG. 6 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-mordenite zeolite (SAR = 240) at 1.0 bar and 298. 15 K.

[0034] FIG. 7 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-Y zeolite (SAR = 30) at 1.0 bar and 298.15 K.

[0035] FIG. 8 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-ZSM-1 1 zeolite (SAR = 50) at 1.0 bar and 298.15 K.

[0036] FIG. 9 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through 5A zeolite at 1.0 bar and 298.15 K.

[0037] FIG. 10 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through 13X zeolite at 1.0 bar and 298.15 K.

[0038] FIG. 11 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-mordenite zeolite (SAR = 30) at 1.0 bar and 298.15 K.DETAILED DESCRIPTION

[0039] The present disclosure provides processes for separating components of refrigerant mixtures. The individual components (i.e., chemical compounds) of the refrigerant mixtures may be referred to as refrigerant components or simply, refrigerants. In embodiments, the refrigerants comprise (or consist of ) halocarbons. The processes comprise flowing a refrigerant mixture through certain zeolites, which are further described below. In embodiments, the refrigerant mixture comprises (or consists ol) two (or more) different types of refrigerants, e.g., 2, 3, 4, 5, 6. By “type,” it is meant chemical formula such that “different types” means the refrigerants have different chemical formulas. The refrigerant mixture may be an azeotropic mixture. The phrase “azeotropic mixture” encompasses near-azeotropic mixtures and refers to a mixture of two (or more) components in which the composition of the vapor phase and the liquid phase are the same or nearly the same at a selected pressure and temperature. The phrase also refers to mixtures of components in which the components have normal boiling point temperatures that are the same or within 10°C of each other or less (including, within 9°C, 8°C, 7°C, 6°C, 5°C, 4°C, 3°C, 2°C, or 1°C).

[0040] The term “halocarbon’" refers to a hydrocarbon in which at least one hydrogen is substituted with a halogen, e.g., fluorine, chlorine, or both fluorine and chlorine. Halocarbons include fluorocarbons, compounds comprising fluorine and carbon, but not hydrogen. A fluorocarbon compound includes an FC-fluorocarbon compound (“FC”), which consists of fluorine and carbon, as well as a chlorofluorocarbon (CFC) compound, which consists of chlorine, fluorine, and carbon, wherein FC and CFC are known terms used to define refrigerants. Fluorocarbon compounds also include, however, compounds selected from the group consisting of fluoroether compounds, fluoroketone compounds, fluoroaromatic compounds and fluoroolefin compounds. Halocarbons also include hydrofluorocarbons, compounds comprising fluorine, carbon, and at least one hydrogen atom. A hydrofluorocarbon compound includes an HFC -hydrofluorocarbon compound (“HFC”), which consists of fluorine, carbon, and hydrogen, as well as a hydrochlorofluorocarbon (HCFC) compound, which consists of chlorine, fluorine, carbon, and hydrogen, wherein HFC and HCFC are known terms used to define refrigerants. Hydrofluorocarbon compounds also include, however, compounds selected from the group consisting of hydrofluoroether compounds, hydrofluoroketone compounds, hydrofluoroaromatic compounds and hydrofluoroolefin, and hydrofluorochloroolefin compounds.

[0041] Non-halocarbon refrigerants include, e.g., alky l alcohols, alkanes (e.g., linear or branched alkanes having from 3 to 8 carbons), alkenes (e.g., linear or branched alkenes having from 3 to 8 carbons), carbon dioxide.

[0042] The two different types of refrigerants (e.g., halocarbons) to be separated from one another using the present processes are further characterized by having different sizes. By “size” it is meant a kinetic diameter d. Values of the kinetic diameter d for refrigerant components are known, e.g., R-12 (4.4 Angstroms), R-13 (4.5 Angstroms), R-14 (4.662 Angstroms), R-22 (4.2 Angstroms), R-32 (3.9 Angstroms), R-116 (5.1 Angstroms), and R- 125 (4.4 Angstroms). (See Wanigarathna, Darshika KJA, Jiajian Gao, and Bin Liu. "Metal organic frameworks for adsorption-based separation of fluorocompounds: a review." Materials Advances 1.3 (2020): 310-320.)

[0043] In embodiments, the size difference between the two refrigerants is at least 0.2 A, at least 0.3 A, at least 0.4 A, or at least 0.5 A. This includes a range of between any of these values. As further described below in the present processes, the refrigerant having the larger size (larger d) is selectively adsorbed onto the zeolite while the refrigerant having the smallersize (smaller d) breaks through the zeolite to be collected therefrom. This includes the refrigerant having the largest size (largest d) in a refrigerant mixture being selectively adsorbed onto the zeolite while refrigerant(s) having smaller sizes (smaller d values) breakthrough, even if they breakthrough together or to differing degrees. In addition, for mixtures of more than two different types of refrigerants, e.g., 3 different types of refrigerants, the size difference described above refers to the refrigerant having the largest d as compared to the refrigerant having the next largest d of the remaining refrigerants. For example, for three refrigerants having sizes di > d2> ds, the size differences described above refers to the difference between di and d2.

[0044] Azeotropic refrigerant mixtures that may be separated using the present processes include those having the ASHRAE designation R-5XX such as those shown in Table 1, below.

[0045] Table 1 R-5XX azeotropic refrigerant mixtures.

[0046] Other refrigerant mixtures that may be separated using the present processes include those having the ASHRAE designation R-4XX such as those shown in Table 2, below. Many of these blends also contain components that form binary azeotropes (e.g., R- 410A is a near-azeotropic mixture of difluoromethane and pentafluoroethane).

[0047] Table 2. R-4XX refrigerant mixtures.

[0048] Table 3, below, lists the individual refrigerants that make up the refrigerant mixtures shown in Tables 1 and 2. above.

[0049] Table 3. Refrigerants from which the refrigerant mixtures of Tables 1 and 2 are composed.

[0050] In embodiments, the refrigerant mixture to be separated using the present processes comprises (or consists of) HFC-125 and one or more (e.g., 2. 3, 4, 5) other refrigerants. In embodiments, the refrigerant mixture to be separated using the present processes comprises (or consists of) HFC-125 and HFC-32. In embodiments, the refrigerant mixture is R-410A, a near-azeotropic mixture composed of 50 mass % HFC-125 and 50 mass % HFC-32.

[0051] The present processes comprise flowing any of the disclosed refrigerant mixtures (e.g., as shown in Tables 1 and 2) through certain zeolites. Zeolites are crystalline materials composed of a rigid, porous framework of silica, alumina, and extra-framework cations (e.g., hydrogen, alkali metals, alkaline earth metals, transition metals). Zeolites may be classified by their framework structure, silica to alumina ratio (SAR), and acidity / basicity. These parameters, and suitable values thereof, for zeolites for use in the present processes are further described below. Although zeolites have been generally considered for some halocarbon separations, the present disclosure is based, at least in part, on the inventors’ unexpected findings as described immediately below.

[0052] Specifically, the present disclosure is based on the fact that refrigerant separation via zeolite adsorption under continuous flow' operation is a non-equilibrium, dynamicprocess, rather than an equilibrium, thermodynamic process. Under continuous flow operation, the separation of refrigerants via adsorption onto a zeolite does not occur during steady state operation, but rather occurs in a transient state as the chemical system approaches thermodynamic equilibrium. In fact, thermodynamic equilibrium is avoided during continuous flow operation. For separation processes occurring under non-equilibrium conditions, the existing wisdom in the field is that the kinetics of the separation process influence the viability and efficacy of separating any particular refrigerant mixture via zeolite adsorption, including to a greater degree than the thermodynamics.

[0053] Using the near-azeotropic refrigerant mixture R-410A as an illustrative example, HFC-125 has larger kinetic diameter (4.4 A) as compared to HFC-32 (3.9 A). As such, even using a zeolite having a chemical affinity7for HFC-125 (based on thermodynamic considerations), it was expected that the inherently slower adsorption rate of HFC-125 relative to HFC-32 would result in early breakthrough of HFC-125 during continuous flow operation, preventing a viable separation based on its selective adsorption (i.e., over the adsorption of HFC-32) onto such a zeolite.This problem was expected to be exacerbated using zeolites posing additional kinetic limitations, e.g., due to spatial inhomogeneity and steric hindrances inherent to their framework structure. However, as demonstrated in the Example, below, the opposite result was observed. Specifically, zeolites such as H-ZSM-5, H-ZSM-11. sihcalite- 1. H-beta. and H-Y were highly selective for HFC-125 over HFC-32under non-equilibrium conditions, enabling breakthrough of HFC-32 at surprisingly high purities, e.g., greater than 99%.

[0054] With reference back to the zeolites suitable for use in the present processes, as noted above, zeolites may be characterized by their SAR, acidity / basicity, and framework structure. Regarding SAR, this refers to the ratio of silica to alumina in the zeolite. The SAR value is related to the hydrophobicity of the zeolite. A higher SAR correlates with greater hydrophobicity7. Suitable zeolites for use in the present processes include hydrophobic zeolites having relatively high SAR values, i.e., a SAR greater than 25. This includes zeolites having a SAR of greater than 50, greater than 75, greater than 100, greater than 150, greater than 200. greater than 250. greater than 300. greater than 350, and greater than 400. This further includes zeolites having a SAR in a range of between any of these values.

[0055] Regarding acidity / basicity. this is determined by the framework cations present in the zeolite framework. The negative charge on the zeolite framework increases with thenumber of alumina units, requiring more positive charge from additional extra-framework cations. If the cations are alkali metal, alkaline earth metal, or transition metals, Lewis acid and Lewis base sites will exist around the additional extra-framework cations and framework oxygen atoms, respectively. In such cases, the zeolite is said to be basic, referring to the existence of strong Lewis base sites. If the cations are hydrogen, Bronsted acid sites will exist. In such cases, the zeolite is said to be acidic, referring to the strong Bronsted acid sites. If an acidic zeolite has been dehydroxylated through calcination at temperatures greater than 500 °C such that cationic alumina species are formed, the zeolite is additionally said to be acidic, referring to the existence of Lewis acid sites. As the SAR decreases, the number of acid / base sites increases and the zeolite becomes more hydrophilic. Basic zeolites and acidic zeolites with SAR < 10 are typically viewed as hydrophilic, whereas acidic zeolites with SAR > 10 are typically viewed as hydrophobic. However, as noted above, increasing the SAR in each case will increase the hydrophobicity of the zeolite. Suitable zeolites for use in the present processes are acidic zeolites.

[0056] Regarding framework structure, this refers to the morphology of the framework as represented by a three-letter framework type code (FTC) as designated by the International Zeolite Association. In general, the various framework structures can be divided into channeltype structures and cage-type structures. The channels in channel-type structures may have elliptical cross-sections, cylindrical cross-sections, or both types of channels may be present. The channels may extend in either one dimension (ID), two dimensions (2D), or three dimensions (3D) throughout the material of the zeolite. Cage-type structures consist of uniform, repeating cages that are connected via short channels. A variety of zeolite framework structures may be used in the present processes, provided the zeolite has a relatively high SAR and is acidic as described above. However, in embodiments, the zeolite being used in the present process has a framework structure characterized by spatial inhomogeneity and steric hindrances. Although such zeolites were expected to prevent the selective adsorption of a larger refrigerant, and thus, its separation from a smaller refrigerant (due to the additional kinetic limitations posed by such zeolites) the opposite result was observed as demonstrated in the Example, below. Framew ork structures characterized by spatial inhomogeneity and steric hindrances include channel-type structures having a 2D channel network or a 3D channel network. Illustrative such framework structures include the following framework structures: MFI, BEA, and MEL. Using the MFI channel-type zeolite as an example, this spatially inhomogeneous and sterically hindered framework definessinusoidal channels with 5.1 x 5.4 A pore openings intersected by straight channels with 5.4 x 5.6 A pore openings. FIG. 1 A shows a schematic of the MFI framework structure, viewed along the

[0010] crystallographic plane; FIG. IB is a view along the

[0100] crystallographic plane.

[0057] Zeolites may also be characterized by pore size. The pore size may refer to the cross-sectional dimension of a channel within the zeolite. The zeolite framework may define different pores having different sizes. Pore size is not particularly limited provided the zeolite defines pores sufficiently large to accommodate the largest refrigerant in the refrigerant mixture. Using HFC-125 as an illustrative example, suitable zeolites include those having a pore size of 5 A or greater.

[0058] Illustrative, specific zeolites that may be used with the present processes include H-ZSM-5 (a MFI zeolite), Silicalite-1 (a MFI zeolite), H-ZSM-8 (a MFI zeolite), H-ZSM-11 (a MEL zeolite), H-beta (a BEA zeolite), H-mordenite (a MOR zeolite), and H-Y (a FAU zeolite). FIG. 2 plots the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through silicalite-1 at 1.0 bar and 298.15 K. FIG. 3 plots the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-ZSM-5 at 1.0 bar and 298.15 K. FIG. 4 plots the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-beta at 1.0 bar and 298. 15 K. FIG. 5 plots the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-Y (SAR = 500) at 1.0 bar and 298.15 K. FIG. 6 plots the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-mordenite (SAR=240) at 1.0 bar and 298.15 K. FIG. 7 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-Y zeolite (SAR = 30) at 1.0 bar and 298.15 K. FIG. 8 shows a plot of the breakthrough profiles for HFC-125 (dashed line) and HFC-32 (solid line) obtained when flowing R-410A through H-ZSM-11 zeolite (SAR = 50) at 1.0 bar and 298.15 K. These plots illustrate the unexpected finding that for these zeolites, despite the expected slower HFC-125 adsorption kinetics, the larger halocarbon HFC-125 is actually retained on the zeolite for an extended period of time while the smaller halocarbon HFC-32 breaks through the zeolite, enabling its recovery7at surprisingly high purity.

[0059] In embodiments, various types of zeolites are excluded from use in the present processes. Among the zeolites that may be excluded are basic zeolites and acidic zeolites having SAR < 25. In embodiments, the zeolite is not a ID channel type zeolite. Illustrative, specific zeolites that may be excluded from use in the present processes include zeolite 5A (a LTA zeolite) and zeolite MX (a FAU zeolite, wherein “M” is an alkali, alkaline earth, or transition metal cation, e.g., Na or Ca). Breakthrough profiles for some zeolites that may be excluded are shown in FIGs. 9-1 1. by way of comparison.

[0060] Breakthrough profiles such as those described above may be used to quantify the selectivity of the present processes towards the desired, larger refrigerant (e.g., halocarbon) in the refrigerant mixture. Specifically, each breakthrough profile provides a breakthrough time for each refrigerant, i.e., the initial time point at which the refrigerant breaks through the zeolite and is detected. The breakthrough times for HFC-125 (tHFC-125) and HFC-32 (tHFC-32) are labeled in FIG. 2. For each refrigerant in a refrigerant mixture (excluding the largest refrigerant), a retention factor (RF) may be defined as the ratio of the breakthrough time of the largest refrigerant to the breakthrough time of the smaller refrigerant. By way of illustration, for a refrigerant mixture composed of HFC-125 (tHFC-125) and HFC-32 (tHFC-32), an RF is defined as tHFc-i2s / tHFc-32. For a refrigerant mixture composed of three refrigerants (i.e., refrigerant A having size d. refrigerant B having size du. and refrigerant C having size de, wherein d.x > di>, > de), two RFs are defined, one for refrigerant B (tx / te) and one for refrigerant C (t.x / tc). The larger the RF, the greater selectivity, since a greater time exists during which only the smaller refrigerant is breaking through the zeolite, enabling its recovery at high purity. The RFs calculated from FIGs. 2-11 are provided in Table 4, below. In embodiments, the present process is characterized by an RF of at least 1.2, at least 1.3, at least 1.4, at least 1.5, at least 1.6, at least 1.8, at least 1.9, at least 2.0, at least 2.1, at least 2.2, at least 2.3. or a range of between any of these values.

[0061] As noted above, the present processes are carried out under continuous flow operation, i.e., by flowing the refrigerant mixture through the selected zeolite at a selected flow rate. In addition to the flow rate, conditions used during the present processes include parameters such as pressure and temperature, each of which may be adjusted to maximize selective adsorption of the larger (including largest) refrigerant (e.g., halocarbon) in the refrigerant mixture onto the zeolite and breakthrough of the smaller refrigerant(s) from the zeolite, i.e., to maximize the RF. Illustrative values of these parameters are provided in the Example, below. As also noted above, the present processes occur under non-equilibriumconditions. By “non-equilibrium conditions,” it is meant that while flowing the refrigerant mixture through the selected zeolite at the selected temperature and pressure, the amount of each refrigerant component adsorbed onto the zeolite does not reach its saturation concentration. By “saturation concentration,” it is meant the value at which the zeolite cannot adsorb any more of the refrigerant component from the refrigerant mixture at the selected temperature and pressure because the equilibrium state for the system been reached.

[0062] Flowing the refrigerant mixture through the zeolite forms a processed refrigerant mixture, which may be collected from the zeolite. As described above and illustrated in the breakthrough profiles of FIGs. 2-8, a first portion of the processed refrigerant mixture comprises (or consists of) the smaller refrigerant at a high degree of purity, e.g., greater than 90 mole percent, 95 mole percent, 97 mole percent, 99 mole percent, or higher. This includes a range of between any of these values. Following this first portion, an additional portion of the processed refrigerant mixture may be collected that comprises both the larger refrigerant now breaking through the zeolite and the smaller refrigerant at a reduced amount as compared to the initial refrigerant mixture. This additional portion of the processed refrigerant mixture may be passed through the zeolite one or more times as desired in order to extract more of the smaller refrigerant.

[0063] A variety of separation systems may be used to carry out the present processes. The Example below described the use of a fixed bed apparatus. However, continuous systems using multiple fixed beds or other configurations may also be used.EXAMPLE

[0064] A fixed bed apparatus was used to conduct dynamic breakthrough experiments using R-410A and various zeolites. The zeolites tested included H-beta (acidic, SAR=300, BEA framework); H-mordenite (acidic, SAR=30 and SAR=240, MOR framework); H-Y (acidic. SAR=30 and siliceous, SAR=500. FAU framework); zeolite 13X (basic, SAR=1.2- 1.5, FAU framework); silicalite-1 (siliceous, MFI framework); H-ZSM-5 (acidic, SAR=30, MFI framework); zeolite 5A (basic, SAR=1, LTA framework); H-ZSM-11 (acidic, SAR = 50, MEL framework). By “siliceous,” it is meant having a SAR of greater than 400.

[0065] The fixed bed apparatus included the following components: two separate mass flow controllers (MFCs), one for R-410A and the other for helium, a 0.5-inch inner diameter reactor tube into which the adsorbent is loaded, a vacuum pump, and a mass spectrometer(MS) that samples what is exiting the reactor as a function of time. The experiments were carried out in three main stages: zeolite pretreat. MS signal calibration, and running the breakthrough experiment.

[0066] Pretreat. 2-10 grams of zeolite were loaded into the reactor tube with stainless steel frits and quartz wool on either end to ensure the adsorbent bed is packed tightly. Reactor tubes were filled with 10 grams of zeolite powder, but some samples had smaller bulk densities. After loading the zeolite powder, the reactor tube was sealed, installed into the apparatus, and wrapped with copper mesh, heating tape, and insulating tape. The apparatus was then pulled under a strong vacuum (approx. 4- 10'5mbar) and heated to 250 °C for at least 12 hours, after which heating is turned off and the apparatus is kept under vacuum.

[0067] MS Signal Calibration. The flow rate of both helium and R-410A were set to known flow rates (e.g., R-410A flowing at 20 standard cubic centimeters per minute (seem) and helium flowing at 30 seem) and the gases flow through a line that bypasses the reactor and goes directly to the MS. Once the MS signals stabilize, the flow rates for each gas were changed to different values and signal stabilization is again allowed to occur. This process was performed at least once, but often multiple times. From the stabilized signals and known flow rates of each species (R-410A has a known composition of 50 / 50 wt.% HFC-125 / HFC- 32), relative sensitivity factors were calculated that are applied to the raw MS signals during data processing of dynamic breakthrough experiment results.

[0068] Dynamic Breakthrough Experiment. After ensuring that the tubing upstream of the reactor was either purged with helium or vacuumed out, helium was fed through the apparatus until the pressure stabilized, as indicated by both the upstream and downstream pressure gauges. Experiments were performed without any back pressure regulation downstream of the reactor, and so the downstream pressure typically stabilized at 1.034 bar, whereas the pressure upstream from the reactor typically stabilized at 1.2-1.7 bar. The temperature at the beginning of the experiment was set to 25 °C, but temperature regulation was not employed during the experiment (adiabatic operation was carried out since the reactor is insulated). Once the temperature and pressure signals were stable, the feed was switched to R-410A. which was fed at 6 seem for the entirety of the experiment. The MS signals w ere observed throughout the experiment, and once both species have broken through (i.e., detected at reactor exit) the reactor and have re-stabilized, the experiment was stopped.

[0069] Breakthrough profiles are shown in FIGs. 2-11 and the some of the results are also summarized in Table 4, below. Table 4 quantifies the selectivity of the zeolite via a retention factor, defined as the ratio of the breakthrough time for HFC-125 (toc-125) to the breakthrough time for HFC-32 (tHFc-32). A large retention factor indicates better HFC-125 selectivity7since a large time exists during which purified HFC-32 exits the reactor.

[0070] Table 4. Results of breakthrough experiments using R-410A and various zeolites.

[0071] The word "illustrative" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "illustrative" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, "a" or "an" means "one or more.”

[0072] The foregoing description of illustrative embodiments of the disclosure has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure. The embodiments were chosen and described in order to explain the principles of the disclosure and as practical applications of the disclosure to enable one skilled in the art to utilize the disclosure in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the claims appended hereto and their equivalents.

[0073] If not already included, all numeric values of parameters in the present disclosure are proceeded by the term ’‘about” which means approximately. This encompasses thosevariations inherent to the measurement of the relevant parameter as understood by those of ordinary skill in the art. This also encompasses the exact value of the disclosed numeric value and values that round to the disclosed numeric value.

[0074] Throughout the present disclosure, terms such as “comprising7’ and the like may be replaced with terms such as “consisting” and the like.

Claims

WHAT IS CLAIMED IS:1 . A process for separating components of a refrigerant mixture, the process comprising flowing a refrigerant mixture through an acidic zeolite to form a processed refrigerant mixture, the refrigerant mixture comprising a first refrigerant component having a size di and a second refrigerant component having a size d2, wherein di > d2, the acidic zeolite having a silica to alumina ratio (SAR) of greater than 25, wherein the acidic zeolite adsorbs the first refrigerant component having the size di while allowing the second refrigerant component having the size d2 to break through the acidic zeolite.

2. The process of claim 1. wherein the step of flowing the refrigerant mixture through the acidic zeolite occurs under non-equilibrium conditions.

3. The process of claim 1. wherein a difference between di and d2 is at least 0.2 A.

4. The process of claim 1, wherein a difference between di and d2 is at least 0.5 A.

5. The process of claim 1. wherein the refrigerant mixture consists of the first refrigerant component having the size di and the second refrigerant component having the size d2.

6. The process of claim 1, wherein the refrigerant mixture comprises pentafluoroethane.

7. The process of claim 6, wherein the refrigerant mixture further comprises difluoromethane.

8. The process of claim 1, wherein the refrigerant mixture consists of pentafluoroethane and difluoromethane.

9. The process of claim 8, wherein pentafluoroethane is present at 50 mass % and difluoromethane is present at 50 mass %.

10. The process of claim 1, wherein the acidic zeolite has a two-dimensional (2D) channel-type structure or a three-dimensional (3D) channel-type structure.

11. The process of claim 1, wherein the acidic zeolite has a MFI, BEA, MEL, MOR, or FAU framework structure.

12. The process of claim 1. wherein the SAR is greater than 100.

13. The process of claim 1, wherein the acidic zeolite is selected from H-ZSM-5, silicalite-1, H-ZSM-8, H-ZSM-11, H-beta, and H-Y.

14. The process of claim 1, wherein the process is characterized by a retention factor (RF) of at least 1.2, wherein RF is defined as a ratio of a breakthrough time of the first refrigerant component having the size di to a breakthrough time of the second refrigerant component having the size d2.

15. The process of claim 1, wherein the processed refrigerant mixture comprises a first portion comprising the second refrigerant component having the size d2 at a purity of greater than 90 mole percent.

16. The process of claim 2, wherein the refrigerant mixture comprises pentafluoroethane and difluoromethane.

17. The process of claim 16, wherein the acidic zeolite has a two-dimensional (2D) channel-type structure or a three-dimensional (3D) channel-type structure.

18. The process of claim 16, wherein the acidic zeolite is selected from H-ZSM-5, silicalite-1. H-ZSM-8, H-ZSM-11. H-beta, and H-Y.

19. The process of claim 18, wherein the SAR is greater than 100.

20. The process of claim 16, wherein the processed refrigerant mixture comprises a first portion comprising difluoromethane at a purity of greater than 90 mole percent.

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