Process for reducing 3,3,3-trifluoropropyne in 2,3,3,3-tetrafluoropropene

Abstract

To provide a process for reducing the concentration of fluorinated alkyne impurities, such as 3,3,3-trifluoropropyne (TFPY), in 2,3,3,3-tetrafluoropropene (HFO-1234yf).SOLUTION: The process comprises bringing a mixture comprising HFO-1234yf and at least one fluorinated alkyne impurity having the formula RC≡CH, where R is perfluorinated linear C1-C3 alkyl, into contact with a caustic material under conditions effective for forming at least one reaction product between the caustic material and at least a portion of the alkyne impurity and for keeping the HFO-1234yf substantially unreacted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001]

[0001] The present invention provides a method for reducing fluorinated alkyne impurities in 2,3,3,3-tetrafluoropropene (HFO-1234yf) using a caustic material. In one embodiment, a caustic material such as sodium hydroxide (NaOH) is used to reduce the level of TFPY (3,3,3-trifluoropropyne) impurity to a level less than 100 ppm. [Background technology]

[0002]

[0002] Hydrofluoroolefins (HFOs), such as tetrafluoropropenes, such as 2,3,3,3-tetrafluoropropene (HFO-1234yf), are known to be effective refrigerants, heat transfer media, propellants, foaming agents, blowing agents, gaseous dielectrics, sterilant carriers, polymerization media, particulate removal fluids, carrier fluids, buffing agents, displacement desiccants, and power cycle working fluids. Unlike chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), both of which can damage the Earth's ozone layer, HFOs do not pose a threat to the ozone layer. HFO-1234yf has also been shown to be a low global warming compound with low toxicity, and thus can meet the increasingly stringent requirements for refrigerants in mobile air conditioning. Thus, compositions containing HFO-1234yf are among the materials being developed for use in many of the above-mentioned applications.

[0003]

[0003] One production process for HFO-1234yf uses 1,1,2,3-tetrachloropropene (1230xa) as the starting material. The process includes the following three steps:

[0004] Step (1): 1230xa + 3HF → 2-chloro-3,3,3-trifluoropropene (1233xf) + 3HCl in a vapor phase reactor packed with a solid catalyst; Step (2): In a liquid-phase reactor packed with a liquid catalyst, 1233xf + HF → 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb); and Step (3): 244bb→1234yf+HCl in a vapor phase reactor. Summary of the Invention [Problem to be solved by the invention]

[0005] In step (3), the final product 2,3,3,3-tetrafluoropropene (1234yf) is usually contaminated with fluorinated organic by-products such as fluorinated alkynes. These fluorinated alkynes include fluorinated propynes such as 3,3,3-trifluoropropyne (TFPY). Because both TFPY and 1234yf are light components with relatively low boiling points, traditional purification methods, such as distillation, result in large yield losses of 1234yf. TFPY is toxic and flammable; therefore, it is desirable to reduce the amount of TFPY in 1234yf using improved methods. [Means for solving the problem]

[0006] In one aspect, the present invention provides a method for reducing the concentration of a fluorinated alkyne impurity in 2,3,3,3-tetrafluoropropene (HFO-1234yf); the method comprises: subjecting a mixture comprising 2,3,3,3-tetrafluoropropene (HFO-1234yf) and at least one fluorinated alkyne impurity having the formula: RC≡CH, where R is a perfluorinated linear C1-C3 alkyl, to conditions effective to reduce the concentration of the alkyne impurity. The method includes contacting the HFO-1234yf with a caustic under conditions that are effective, such that the caustic forms a reaction product with at least a portion of the alkyne impurity and the HFO-1234yf remains substantially unreacted. Substantially unreacted as used herein means that at least 90% by weight of the HFO-1234yf does not react with the caustic. The reaction product can then be removed from the HFO-1234yf to reduce the concentration of the alkyne impurity. In one embodiment, the fluorinated alkyne impurity is TFPY. Caustic materials that can be used in the present invention include, without limitation, alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and combinations thereof. In a preferred embodiment, the caustic material is sodium hydroxide (NaOH). The concentration of the fluorinated alkyne impurity is reduced by at least about 20% (wt / wt); in another embodiment, the concentration of the fluorinated alkyne impurity is reduced by at least about 50% (wt / wt).

[0007]

[0006] In a preferred embodiment, the present invention relates to a method for reducing the concentration of 3,3,3-trifluoropropyne (TFPY) in 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising: (a) providing a first composition comprising 2,3,3,3-tetrafluoropropene (HFO-1234yf) and a first concentration of 3,3,3-trifluoropropyne (TFPY); (b) contacting the first composition with a caustic material under conditions effective to react the caustic material with at least a portion of the TFPY; and (c) recovering a second composition comprising 1234yf and a second concentration of TFPY, wherein the second concentration is less than the first concentration. In one embodiment, the first concentration of TFPY is greater than 300 ppm by weight and the second concentration of TFPY is 300 ppm or less, in another embodiment 200 ppm or less, preferably 100 ppm or less. [Brief description of the drawings]

[0008] [Figure 1]

[0007] The Figure graphically illustrates the decrease in concentration of TFPY over time in one embodiment of the invention using 4% (w / w) NaOH as the caustic at 25°C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009]

[0008] The entire contents of US Patent No. 8,058,486 are incorporated herein by reference. The procedures described below can be carried out as continuous, semi-continuous, or batch processes, or any combination thereof.

[0010] In one aspect, the present invention provides a method for reducing the concentration of a fluorinated alkyne impurity in 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising contacting a mixture comprising 2,3,3,3-tetrafluoropropene (HFO-1234yf) and at least one fluorinated alkyne impurity having the formula RC≡CH, where R is a perfluorinated linear C1-C3 alkyl, with a caustic material under conditions effective to reduce the concentration of the alkyne impurity. The conditions are such that a reaction product between the caustic material and the alkyne impurity is formed, while the HFO-1234yf remains substantially unreacted and substantially intact. The reaction product can be removed to further isolate the HFO-1234yf of increased purity. The term "reaction product" includes, without limitation, the product or products formed by contacting a caustic with an alkyne impurity as described herein, such as, without limitation, one or more decomposition products or other products formed by contacting a caustic, such as NaOH, with an alkyne, such as TFPY. As used herein, the term "linear perfluorinated alkyl group" refers to a linear alkyl group in which all hydrogens on the carbon atoms of the alkyl group are replaced by fluorine. Examples of linear perfluorinated alkyl groups include -CF3, -CF2CF3, and -CF2CF2CF3. In a preferred embodiment, the perfluorinated alkyl group is -CF3, i.e., the fluorinated alkyne impurity is 3,3,3-trifluorinated alkyl group. It is oropropionate (TFPY).

[0011]

[0010] Without limitation, in one embodiment, the starting concentration of the fluorinated alkyne impurity in the mixture is greater than about 400 ppm, but other starting concentrations, such as concentrations less than 400 ppm, are included. The contacting can be performed by methods known in the art, such as, for example, adding caustic directly to a composition consisting of HFO-1234yf and fluorinated alkyne impurities; other contacting methods include passing a composition containing HFO-1234yf and fluorinated alkyne impurities in vapor form through a reaction vessel or reactor filled with caustic. HFO-1234yf with a reduced concentration of fluorinated alkyne impurities can be recovered by conventional methods, such as phase separation when caustic is added directly to a composition containing HFO-1234yf and fluorinated alkyne impurities; and compression or condensation when the composition consisting of HFO-1234yf and fluorinated alkyne impurities is passed through caustic as a mixed vapor. Optionally, other purification means such as distillation can then be applied to further increase the purity of the HFO-1234yf.

[0012]

[0011] The caustic material can include, for example, an alkali metal hydroxide, an alkali metal oxide, an alkaline earth metal hydroxide, an alkaline earth metal oxide, and combinations thereof. Without limitation, examples of suitable alkali metal hydroxides include potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), and combinations thereof. Non-limiting examples of alkaline earth metal hydroxides include magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), strontium hydroxide (Sr(OH)2), barium hydroxide (Ba(OH)2), and combinations thereof. A representative non-limiting example of an alkaline earth metal oxide is calcium oxide (CaO). In a preferred embodiment, the caustic material is NaOH.

[0013] In one embodiment, effective conditions include, without limitation, having the caustic present in the aqueous solution at less than 50% by weight; in one embodiment, having the caustic present in the aqueous solution at between 0.1% and about 20% by weight; in another embodiment, having the caustic present in the aqueous solution at between about 1% and about 10% by weight; in a further embodiment, having the caustic present in the aqueous solution at between about 2% and about 5% by weight; and even more preferably, having the caustic present in the aqueous solution at between about 4% by weight. Without limitation, suitable temperatures for the contacting step include temperatures between about 0° C. and about 100° C.; in one embodiment, between about 10° C. and about 80° C.; in a further embodiment, between about 20° C. and about 60° C. Suitable pressures for the contacting step include pressures between about 0.1 psig and about 1000 psig; in another embodiment, between about 5 psig and about 500 psig; in a further embodiment, between about 10 psig and about 100 psig. In one embodiment, the reaction product between the caustic and the alkyne impurity may be removed from the HFO-1234yf by techniques known in the art, such as by phase separation, optionally followed by distillation.

[0014] In one embodiment, by practicing the present invention, the concentration of fluorinated alkyne impurities in the mixture is reduced by at least about 20%; preferably, the concentration of fluorinated alkyne impurities in the mixture is reduced by at least about 30%; more preferably, the concentration of fluorinated alkyne impurities in the mixture is reduced by at least about 40%; and even more preferably, the concentration of fluorinated alkyne impurities in the mixture is reduced by at least about 50%.

[0015] In another embodiment, by practicing the present invention, the concentration of fluorinated alkyne impurities is reduced to a level of about 300 ppm or less; in one embodiment, the concentration of fluorinated alkyne impurities is reduced to a level of about 200 ppm or less; in another embodiment, the concentration of fluorinated alkyne impurities is reduced to a level of about 200 ppm or less. The concentration of the pure substance is reduced to a level of about 100 ppm or less.

[0016] In another aspect, the present invention relates to a method for reducing the concentration of 3,3,3-trifluoropropyne (TFPY) in a composition consisting of 3,3,3-trifluoropropene (TFPY) and 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising: (a) providing a first composition comprising 2,3,3,3-tetrafluoropropene (HFO-1234yf) and a first concentration of a fluorinated alkyne impurity such as 3,3,3-trifluoropropyne (TFPY); wherein, without limitation, the first concentration of TFPY as representative of a fluorinated alkyne impurity is greater than 300 ppm, but includes lower concentrations; the method further comprises: (b) contacting the first composition with a caustic under conditions effective to react at least a portion of the TFPY with the caustic; wherein the caustic is as described above and is provided in the form of an aqueous solution, for example in the weight percentages described below. In one embodiment, the caustic material comprises NaOH. In another embodiment, the NaOH is provided as an aqueous solution of about 0.1% to about 20% by weight NaOH; in yet another embodiment, the NaOH is provided as an aqueous solution of about 1% to about 10% by weight NaOH; in yet another embodiment, the NaOH is provided as an aqueous solution of about 2% to about 5% by weight NaOH; in yet another embodiment, the NaOH is provided as an aqueous solution of about 4% by weight NaOH. The method further comprises (c) recovering a second composition comprising 1234yf and a second concentration of TFPY, the second concentration being less than the first concentration; without limitation, in embodiments where the first concentration of TFPY is greater than 300 ppm, the second concentration of TFPY is 300 ppm or less; preferably about 200 ppm or less; more preferably about 100 ppm or less.

[0017] The process of the present invention can be used as part of a larger process for producing compounds such as 2,3,3,3-tetrafluoropropene (1234yf). For example, the process of the present invention can be associated with step (3) of the three-step process for producing 1234yf described above. In a preferred embodiment in this regard, for step (3): HCFC-244bb produced in step (2) is dehydrohalogenated under conditions effective to produce 2,3,3,3-tetrafluoropropene (HFO-1234yf). Preferably, the dehydrohalogenation step comprises a gas or vapor phase catalytic reaction. The catalytic conversion of HCFC-244bb is carried out under conditions effective to dehydrochlorinate HCFC-244bb to produce 2,3,3,3-tetrafluoropropene (HFO-1234yf). Preferably, the dehydrochlorination of HCFC-244bb is carried out in the vapor phase, more preferably in the vapor phase in a fixed bed reactor. The dehydrohalogenation reaction can be carried out in any suitable reaction vessel or reactor, which should preferably be constructed of materials that are resistant to the corrosive action of hydrogen chloride (to the extent that such materials are formed under dehydrohalogenation conditions), such as nickel and its alloys, e.g., Hastelloy, Inconel, Incoloy, and Monel, or vessels lined with fluoropolymers, and may employ single or multiple tubes filled with a dehydrohalogenation catalyst.

[0018] The catalyst may be a metal halide, a metal oxide halide, a neutral (or zero oxidation state) metal or metal alloy, or an activated carbon, in bulk or supported form. When a metal halide or metal oxide catalyst is used, preferably, monovalent, divalent, and trivalent metal halides, oxides, and mixtures / combinations thereof are used, more preferably monovalent and divalent metal halides, and mixtures / combinations thereof. The constituent metals are Cr, ... 3+ , Fe 3+ , Mg 2+ , Ca 2+ , Ni 2+ , Zn 2+ , Pd 2+, Li + , Na + , K + , and Cs + The halogen components include, but are not limited to, F. - , Cl - , Br - , and I - Examples of useful monovalent or divalent metal halides include, but are not limited to, LiF, NaF, KF, CsF, MgF2, CaF2, LiCl, NaCl, KCl, and CsCl. Halogenation treatments include, but are not limited to, any of those known in the art, particularly those using HF, F2, HCl, Cl2, HBr, Br2, HI, and I2 as halogenation sources.

[0019]

[0018] When neutral, i.e., zero-valent metals, metal alloys, and mixtures thereof are used, useful metals include, but are not limited to, Pd, Pt, Rh, Fe, Co, Ni, Cu, Mo, Cr, Mn, and combinations of the above as alloys or mixtures. The catalyst may be supported or unsupported. Useful examples of metal alloys include, but are not limited to, SS316, Monel 400, Inconel 825, Inconel 600, and Inconel 625.

[0020]

[0019] HCFC-244bb can be introduced into the reactor either in pure form, partially purified form, or as part of the reactor effluent stream from a previous step. HCFC-244bb can be optionally fed with an inert gas diluent such as nitrogen, argon, and the like. In one embodiment of the invention, HCFC-244bb is prevaporized or preheated prior to introduction into the reactor. Alternatively, HCFC-244bb is vaporized inside the reactor. Useful reaction temperatures can range from about 100°C to about 700°C. Preferred temperatures can range from about 150°C to about 600°C, and more preferred temperatures can range from about 200°C to about 550°C. The reaction can be carried out at atmospheric pressure, superatmospheric pressure, or under vacuum. The vacuum pressure can be from about 5 torr (0.0966 psia) to about 760 torr (14.69 psia). Contact times between HCFC-244bb and the catalyst may range from about 0.5 seconds to about 120 seconds, although longer or shorter times can be used.

[0021] In the dehydrofluorination embodiments described herein, the conversion of HCFC-244bb is at least about 10%, more preferably at least about 20%, and even more preferably at least about 30%. Preferably, in such embodiments, the selectivity to HFO-1234yf is at least about 70%, more preferably at least about 85%, and more preferably at least about 95%.

[0022] In one embodiment, the process flow may be downward or upward through the bed of catalyst, or horizontal. It may also be advantageous to periodically regenerate the catalyst while it is in place in the reactor after extended use. Regeneration of the catalyst may be accomplished by any means known in the art, for example, with an oxidizing agent such as O2 or chlorine. For example, the catalyst may be regenerated by passing air or air diluted with nitrogen over the catalyst at temperatures between about 100°C and about 400°C, and in other embodiments, between about 200°C and about 375°C, for about 0.5 hours to about 3 days, depending on the size of the reactor. Regeneration of the catalyst may also include the use of a reducing agent such as H2. Other reducing agents include, without limitation, NH3 (ammonia), CO (carbon monoxide), CH4 (methane); mixtures thereof, including mixtures with hydrogen, may also be used.

[0023]

[0022] In general, the effluent from the dehydrohalogenation reaction step, including any intermediate effluents that may be present in the multi-stage reactor sequence, may be treated to achieve the desired degree of separation and / or other treatment. For example, in embodiments in which the reactor effluent contains HFO-1234yf, the effluent will generally also contain HCl and unreacted HCFC-244bb. Some or substantially all of these components of the reaction product may be recovered using any separation or purification method known in the art, such as neutralization and distillation. By practicing the present invention, the concentration of alkyne impurities, such as TFPY, may be reduced. It is expected that the unreacted HCFC-244bb may be recycled in whole or in part to improve the overall yield of the desired CF3CF=CH2 (HFO-1234yf). Optionally, hydrogen chloride is then recovered from the result of the dehydrochlorination reaction. Recovery of hydrogen chloride may be achieved by conventional distillation. and removing it from the distillate.

[0024] Alternatively, the HCl can be recovered or removed by using water or a caustic scrubber. When a water extractant is used, the HCl is removed as an aqueous solution. When a caustic scrubber is used, the HCl is removed from the system as a chloride salt in an aqueous solution.

[0025]

[0024] In another embodiment of the present invention, the dehydrohalogenation of HCFC-244bb can also be carried out by reacting it with a strong caustic solution, including but not limited to KOH, NaOH, Ca(OH)2, and CaO, at an elevated temperature. This is described in US Patent Publication 2011 / 0270000. In this case, the concentration of the caustic solution is about 2% to about 100% by weight, in another embodiment about 5% to about 90% by weight, and in yet a further embodiment about 10% to about 80% by weight. The molar ratio of caustic to HCFC-244bb is preferably in the range of about 1:1 to about 2:1, more preferably about 1.1:1 to about 1.5:1, and most preferably about 1.2:1 to about 1.4:1. The reaction can be carried out at a temperature of about 20°C to about 100°C, in another embodiment about 30°C to about 90°C, and in a further embodiment about 40°C to about 80°C. As noted above, the reaction can be carried out at atmospheric pressure, above atmospheric pressure, or under vacuum. The vacuum pressure can be from about 5 torr (14.80 psig) to about 760 torr (29.40 psig). Additionally, the organic compounds can be optionally dissolved in the caustic solution using a solvent or phase transfer catalyst such as Aliquat 336. This optional step can be carried out using solvents known in the art for such purposes. The HFO-1234yf can then be recovered from the reaction product mixture, including unreacted starting materials and by-products, by any means known in the art, such as extraction and preferably distillation. The mixture of HFO-1234yf and any by-products is passed through a distillation column. For example, the distillation can be preferably carried out at atmospheric pressure, above atmospheric pressure, or in vacuum in a standard distillation column. Preferably, the pressure is less than about 300 psig, preferably less than about 200 psig, and most preferably less than 150 psig. The pressure of the distillation column inherently determines the distillation operating temperature. Preferably, in such dehydrofluorination embodiments described in this section, the conversion of HCFC-244bb is at least about 60%, more preferably at least about 75%, and even more preferably at least about 90%. Preferably, in such embodiments, the selectivity to HFO-1234yf is at least about 70%, more preferably at least about 85%, more preferably at least about 95%.

[0026]

[0025] Unless indicated to the contrary, all percentages and ppm are by weight. Furthermore, as used herein, the terms "caustic" and "caustic material" are synonymous and are used interchangeably. EXAMPLES

[0027] The following non-limiting examples serve to illustrate the invention.

[0028] The following description is for the purposes of example only and does not limit the scope of the invention. Example 1:

[0029] A TFA (trifluoroacetic acid) / D2O insert was placed inside the NMR tube. Approximately 1.0 g of DI water was added, enough to just cover the insert. The exact weight of the DI water was recorded. The NMR tube was then equilibrated in a temperature bath at approximately 25°C for approximately 2 minutes. A pure sample of 3,3,3-trifluoropropyne (TFPY) gas was then slowly bubbled into the liquid using a PEEK fine tube to saturate the water and the headspace above the water. The NMR tube was immediately tightly capped to prevent gas from escaping. The initial concentration of TFPY (at time t=0) was calculated as: 19 The concentrations of dissolved gases were determined by F-NMR analysis. Next, a sample of 44% NaOH solution was prepared and approximately 0.1 g of the sample was injected into the sample and mixed. This resulted in a solution of approximately 4% NaOH by weight. The injection time was recorded and the sample was mixed every 5-6 minutes for 1 hour. 19 The results were analyzed by F-NMR. The concentration of TFPY in 4% (w / w) NaOH solution was measured and plotted, as shown in the figure. The figure graphically depicts the concentration of TFPY in 4% NaOH solution as a function of time at 25°C. As shown in the figure, the concentration of 3,3,3-trifluoropropyne decreased with time, indicating that a reaction between TFPY and NaOH is occurring.

[0028] Comparative Example 1:

[0030] Instead of 3,3,3-trifluoropropyne, 2,3,3,3-tetrafluoropropene (HFO-1234yf) was used in Comparative Example 1. Following the same procedure as described in Example 1, it was found that the concentration of HFO-1234yf in 4% (w / w) NaOH remained constant, indicating that no reaction occurred between HFO-1234yf and NaOH.

[0029] Example 2:

[0031] 1 L of Tedlar gas was charged with 3,3,3-trifluoropropyne (TFPY) gas at room temperature and 2.11 g of 4% NaOH solution was injected into the bag through the septum. The liquid was allowed to react for 4 days with occasional rotation of the bag. The liquid was carefully withdrawn from the bag using a syringe and calibrated with a TFA (trifluoroacetic acid) / D2O insert. 19 The reaction was analyzed by F-NMR. The results showed that as the reaction proceeded, the peak at -51.0 ppm (attributed to TFPY) decreased, while the peak at -119.9 ppm (F - The results showed that the amount of TFPY (attributed to fluoride) increased. This indicates that some of the TFPY reacted and disappeared, and fluoride was formed as one of the reaction products. Integration also showed that the conversion of TFPY to fluoride was quantitative. By extending the reaction time to 6 days after injecting the liquid back into the bag to ensure the reaction was complete, the reaction capacity of TFPY in 4% (w / w) NaOH solution was determined to be about 1.7%-1.8% (w / w) of the amount of 4% (w / w) NaOH solution.

[0030] Example 3:

[0032] A 750 g mixture of 1234yf and TFPY (0.5% TFPY) is passed through 200 mL of 4% (w / w) aqueous NaOH at room temperature and 1 atm through a gas sparger, and the tail gas is collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results show that the concentration of TFPY in 1234yf was reduced to about 260 ppm, and the recovery of 1234yf was 99%.

[0031]

[0033] In other experiments, the same procedure was used but with 4% (w / w) aqueous KOH, with similar results. Example 4:

[0034] A 750 g mixture of 1234yf and TFPY (0.5% TFPY) was passed through 210 mL of 4% (w / w) aqueous NaOH at room temperature and 1 atm through a gas sparger, and the tail gas was collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results show that the concentration of TFPY in 1234yf was reduced to about 20 ppm (w / w), and the recovery of 1234yf was 99%.

[0032]

[0035] In other experiments, the same procedure was used but with 4% (w / w) aqueous KOH, with similar results. Example 5:

[0036] A 175 g mixture of 1234yf and TFPY (0.5% (w / w) TFPY) was added to 200 mL of 200% (w / w) NaO2 via a gas sparger at room temperature and 1 atm. The mixture was passed through a H2O solution and the tail gas was collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results show that the concentration of TFPY in 1234yf was reduced to about 75 ppm (w / w) and the recovery of 1234yf was 99%.

[0033]

[0037] In other experiments, the same procedure was used but with 1% (w / w) aqueous KOH, with similar results. Example 6:

[0038] A 2000 g mixture of 1234yf and TFPY (0.5% (w / w) TFPY) is passed through 205 mL of 10% (w / w) aqueous NaOH at room temperature through a gas sparger and the tail gas is collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results show that the concentration of TFPY in 1234yf was reduced to about 165 ppm (w / w) and the recovery of 1234yf was 98%.

[0034]

[0039] In another experiment, the same procedure was used but with 10% (w / w) aqueous KOH, and similar results were obtained.

Claims

1. 1. A method for reducing the concentration of fluorinated alkyne impurities in 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising: １ ~C ３ and contacting a mixture containing at least one fluorinated alkyne impurity having a molar ratio of 1:1 or 2:1, with a caustic material under conditions effective to form at least one reaction product between the caustic material and at least a portion of said alkyne impurity and to maintain said HFO-1234yf substantially unreacted.

2. 10. The method of claim 1, further comprising recovering said HFO-1234yf having a reduced concentration of said fluorinated alkyne impurity.

3. R is -CF ３ The method of claim 1, wherein

4. 2. The method of claim 1, wherein the caustic material is selected from the group consisting of alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and combinations thereof.

5. 5. The method of claim 4, wherein the alkali metal hydroxide is selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), and combinations thereof.

6. The alkaline earth metal hydroxide is magnesium hydroxide (Mg(OH) ２ ), calcium hydroxide (Ca(OH) ２ ), strontium hydroxide (Sr(OH) ２ ), barium hydroxide (Ba(OH) ２ 5. The method of claim 4, wherein the compound is selected from the group consisting of:

7. The method of claim 4, wherein the alkaline earth metal oxide is calcium oxide (CaO).

8. 10. The method of claim 1, wherein the caustic is present in an aqueous solution at less than about 50% by weight of the caustic.

9. 9. The method of claim 8, wherein the caustic is present in the aqueous solution at between about 0.1% and about 20% by weight of the caustic.

10. 10. The method of claim 9, wherein the caustic is present in the aqueous solution at between about 1% and about 10% by weight of the caustic.

11. 11. The method of claim 10, wherein the caustic is present in the aqueous solution at between about 2% and about 5% by weight of the caustic.

12. 12. The method of claim 11, wherein the caustic is NaOH.

13. 10. The method of claim 1, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 20%.

14. 14. The method of claim 13, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 30%.

15. 15. The method of claim 14, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 40%.

16. 16. The method of claim 15, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 50%.

17. 1. A method for reducing the concentration of 3,3,3-trifluoropropyne (TFPY) in 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising: (a) providing a first composition comprising 2,3,3,3-tetrafluoropropene (HFO-1234yf) and a first concentration of 3,3,3-trifluoropropyne (TFPY); (b) contacting the first composition with a caustic substance under conditions effective to react at least a portion of the TFPY with the caustic substance; and (c) recovering a second composition comprising 1234yf and a second concentration of TFPY, wherein said second concentration is less than said first concentration; The above method comprising the steps of:

18. 20. The method of claim 17, wherein the first concentration of TFPY is greater than 300 ppm.

19. 20. The method of claim 17, wherein the second concentration of TFPY is less than or equal to 300 ppm.

20. 20. The method of claim 19, wherein the second concentration of TFPY is about 200 ppm or less.

21. 21. The method of claim 20, wherein the second concentration of TFPY is about 100 ppm or less.

22. 20. The method of claim 17, wherein the caustic comprises NaOH.

23. 23. The method of claim 22, wherein the NaOH is provided as an aqueous solution of about 0.1% to about 20% NaOH by weight.

24. 24. The method of claim 23, wherein the NaOH is provided as an aqueous solution of about 1% to about 10% by weight NaOH.

25. 25. The method of claim 24, wherein the NaOH is provided as an aqueous solution of about 2% to about 5% NaOH by weight.

26. 25. The method of claim 24, wherein the NaOH is provided as an aqueous solution of about 4% NaOH by weight.

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