PROCESS FOR PRODUCING CHLOROTRIFLUOROETHYLENE

PROCESS FOR PRODUCING CHLOROTRIFLUOROETHYLENE

The present invention relates to and claims the priority benefit of U.S. Application 62/046,340, filed September 4, 2014, which is incorporated herein by reference in its entirety as is ful ly set forth below.

The present invention relates, at least in part, to a process for makmgchlorotrifluoroethyiene (CFO-1113) from !,2-dichloro-l,l,2~trifluoroethane (HCFC-

1-chloro-l ,2,2-trifluoroethylene (also named as chlorotrifluoroethylene (CTFE) or CFO-1113) is commonly used as a refrigerant in cryogenic applications. CFO-1113 has a carboncarbon double bond and so can be polymerized to form polychlorotrilluoroethylene or copolymerized to produce the plastic ECTFE. Chlorotrifluoroethylene (CFO-1113) is currently manufactured commercially by dechlorinating 1,1,2-trichlorotrifluoroethane (CFC-113) via reaction with zinc in the presence of methanol as a solvent. A major drawback with this process is the formation of l,2-dichloro-l,l,2-trifluoroethane (HCFC-I23a) as a major byproduct, which greatly reduces the yield of CFO-1113 and is also costly to dispose of

Applicants have come to appreciate that it would be desirable to develop a method which is able to convert HCFC-123a to a more useful product, including specifically CFO-1112. One route which has been contemplated by applicants for producing CFO-1113 from HCFC-123a is through its dehydrochlorination either in the presence of a caustic solution in a liquid phase reaction or more preferably in the presence of a solid catalyst in a vapor phase reaction, One potential problem that may be associated with certain vapor phase processes is the formation of by-products such as trans- and/or cis-isomers of 1,2-dichloro-1,2-difluoroethylene (CFO-1112) which can be formed via a competing deliydrotluorination reaction. The formation of these byproducts in significant quantaties can negatively reduce the yield of the desired CFO-1112 product and can negatively effect the process efficiency due to additional requirements for product separation. Applicants have therefore comet to appreciate that it would be advantageous to develop processes and systems, including catalyst systems, that are able to reduce or suppress the extent of undesirable dehydrofluorination reactions and to increase the productivity and yield of the desired fluorinated olefin, namely, CFO-1113.

In certain non-limiting aspects, the present invention provides processes for making chlorotrifluoroethylene (CFO-1113) from 1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a). In certain embodiments, the processes include dehydrochlorinating 1,2-dichloro-1,1,2-trifiuoroethane (HCFC-123a) in the presence of a catalyst selected from the group consisting of

(i) one or more metal halides; (ii) one or more halogenated metal oxides; (iii) one or more zero-valent metals or metal alloys; and (ΐν) combinations thereof. This reaction can be depicted schematically as follows:

Cl₂FC-CHF₂GlF©MS8s

Preferably, the processes provides a conversion percentage of HCFC-123a that is at least about 5 wt.% , more preferably in certain embodiemtns at least about 10 wt.% , and even more preferably in certain embodiments at least about 15 wt.%. In certain preferred embodiments, include in accordance with each of the preferred conversion percentages mentioned herein, the selectivity of the process to chlorotrifluoroethylene is at least about 70 wt. %, more preferably in certain embodiments at least about 80 wt. %, and even more preferably in certain embodiments at least about 90 wt. %.

The reaction product stream of the dehydrochlormating step, that is, prior to any distillation or purification, in certain embodiments preferably includes less than about 10 wt. % of organic by-product impurities, more preferably in certain embodiments less than about 7 wt.

% of organic by-product impurities, and in even more preferably in certain embodiments less than about 5% organic by-product impurities. In certain embodiments, the reaction product stream, prior to any distillation or purification, preferably includes less than about 10 wt. % of the organic by-product impurity CFO-1112, more preferably in certain embodiments less than about 7 wt. % of CFO-1112, and in even more preferably in certain embodiments l ess than about 5 wt. % of CFO-1112. As used herein, the term “organic by-product impurities” means organic products other than the the starting reactants, including HCFC-123a but does not include by-product acid gas, such as HC1 or HF.

The dehydrochlorinating step may be conducted under reaction conditions, including temperature, pressure and reaction time conditions, that results in the desired CFO-1113 product and preferably one or more of the advantages discussed herein. In certain preferred embodimens, the process comprises conducting the dehydrochlorination at a temperature greater than about 400 °C, more preferably in certain embodiments greater than about 425 °C, and even more preferably in certain embodiments greater than about 450 °C.. In certain aspects, at least a substantial portion of the dehydrochlorination reaction, and preferably in certain embodiment substantially the entire dehydrochlorination reaction, is conducted within a temperature range of from about 400 °C to about 550 °C, and more preferably in certain embodiments within a temperature range of from about 425 °C to about 550 °C, and even more preferably in certain embodiments within a temperature range of from about 480 °C to about 550 °C. In certain preferred embodiments, at least a substantial portion of the dehydrochlorination reaction, and preferably in certain embodiment substantially the entire dehydrochlorination reaction, is conducted within a temperature range of from about 480 °C to about 525 °C.

In certain preferred embodiments, the catalyst includes mono-valent metal halide, bi-valent metal halide, tri-valent metal halide, or a combination thereof. The catalyst can be supported or unsupported, although supported catalyst systems are preferred in certain embodiments. The component metal in such preferred embodiments may include one or more of Cr \ Pe^3r, Mgⁱ⁺, Ca²"^f', Ni^z"^h. Zn^2f, Pdⁱ⁺, Li\ Na^r, K^r, and Cs fr The component halogen may include one or more ofF", Cl', Br", and I'. Non-limiting examples of such catalysts include one or more of LiF, NaF, KF, CsF, Mgp2, Cap2, LiCl, NaCl, KC1, and CsCf. In certain embodiments, the catalyst includes an optionally supported combination of MgF?and one or more of CsCl. LiCl, NaCl, KC1, LiF, NaF, KF, and/or CsF. In certain preferred embodiments of the foregoing combination, the one or more of CsCl, LiCl, NaCl, KC1, LiF, NaF, KF, and/or CsF is present in an amount of about 5.0 wt.% to about 50 wt fro, based on the total weight of the catalyst in combination with MgPV

In further embodiments, the catalyst may include one or more of an optionally substituted halogenated mono-valent metal oxide, halogenated bi-valent metal oxide, halogenated trivalentmetal oxide, or a combination thereof. In such embodiments, the component metal may include one or more of Cr³⁺, Fe~^r, Mgⁱ⁺, Ca²'"', Ni^z"^h, Zn^2f, Pdⁱ⁺, Li⁺, Na^r, Kf, and Cs\ Non-limiting examples of such catalysts include at least one optionally supported halogenated metal oxide selected from the group consisting of fluorinated or chlorinated MgO, fluorinated or chlorinated CaO, fluorinated or chlorinated Li₂0, fluorinated or chlorinated Na₂0, fluorinated or chlorinated Κ2Ο, and fluorinated or chlorinated Cs₂0. In certain aspects, the catalyst includes an optionally supported combination of fluorinated MgO with one or more of a fluorinated Cs₂0, a fluorinated LyO, a fluorinated Na?0, and/or a fluorinated K₂0. In certain aspects of such a combination, the one or more of a fluorinated CS2O, a fluorinated Li₂0, a fluorinated Na₂0, and/or a fluorinated K₂0 may be present in an amount of about 5.0 wt.% to about 50 wt %, based on the total weight of the catalyst in combination with MgO.

In even further embodiments, the catalyst comprises an optionally supported zero valent metal, a zero valent metal alloy, or a combination thereof. In such embodiments, the component metal may include one or more of Pd, Pt, Rh, Ru, Ir, Os, Fe, Co, Ni, Cu, Mo, Cr, and Μη. Zero valent metal alloys may include one or more stainless steel alloys, Monel alloys, Inconel alloys, Hastelloy alloys, Incolov alloys and combinations thereof. Catalyst supports may include, but are not limited to, MgO, fluorinated MgO, MgF₂, carbon materials such as activated carbons and carbon molecular sieves, and α-Αΐ2Ο3. In certain preferred embodiments, the zero valent metal or zero valent metal alloy comprises one or more of Pd, Pt, Ru, Rh, and/or Ir supported on MgO. In certain preferred embodiments of such a preferred combination, the one or more of Pd, Pt, Ru, Rh, and/or Ir may be present in an amount of about 0.05 to about 5 wt %, based on the total weight of the catalyst in combination with MgO. I11 further embodiments, the catalyst is a zero valent metal alloy that is contained within the walls of the reactor.

Additional embodiments and advantages will be readily apparent to one of skill in the art on the basis of the disclosure provided herein.

In the present invention, l,2-dichloro-l,l,2-trifluoroethane (HCFC-123a) is dehydrochlorinated in the presence of a catalyst to form a product comprising chlorotrifluoroethylene (CFO-1 ! 13).

In the process of the present invention, the catalysts are preferably selected to to achieve the selectivity and/or conversion of HCFC-123a to CFO-1113 according to one or more of the preferred embodiments described herein. The processes of the present invention preferably utiize catalysts as described herein since applicants have found that such catalysts are capable, especially and preferably under the other reaction conditions specified herein, of providing advantageous selectivity for the dehydrochlorination reaction than for competing reactions, including dehydrofluorination side reaetion(s).

There are three preferred classes of cataly sts that applicants have found to be especial ly useful in the present invention: (i) metai halides, (ii) halogenated metal oxides, and (iii) zero-valent metals/metal alloys.

The first class of catalysts is metal halides. In certain preferred embodiments, the metal halides include mono-, bi-, and tri-valent. metal halides and their mixtures/combinations, and in certain more preferred embodiments mono- and bi-valent metal halides and their mixtures/combinations. Component metals include, but are not limited to, Cr^Jt, Fe^{3 h}, Mg²', Caf’', Nk\ Zn^2t, Pd^2:, Li^:, Na³, K³, and Cs . Component halogens include, but are not limited to, F‘, Cf, Br, and F. Examples of preferred mono- or bi-valent metal halides include, but are not limited to, LiF, NaF, KF, CsF, MgF?., CaPb, LiCl, NaCl, KC1, and CsCl. The catalyst may he supported or unsupported, such as with one or a combination of catalyst supports discussed herein. In certain embodiments, the catalyst is a combination of MgFa with one or more of CsCl, LiCl, NaCl, KO, LiF, NaF, KF, and/or CsF. In certain aspects of such embodiments, CsCl, LiCl, NaCl, KC1, LiF, NaF, KF', and/or CsF are present in an amount of about 5.0 to about 50 wt %, based on the total weight of the catalyst.

The second class of catalysts is halogenated metal oxides. In certain preferred embodiments, the halogenated metal oxides include halogenated mono-, hi-, and tri-valent metal oxides and their mixtures/combinations, and in certain more preferred embodiments halogenated mono- and bi-valent metal oxides and their mixtures/combinations. Component metals include, but are not limited to, CL, Fe³⁴, Mg²⁴', Ca^z'^r, Ni²⁴, Zn^z4, Pd²⁴', Li⁴', Na⁴, K⁴, and Cs⁺.

Halogénation treatments can include any of those known in the prior art, particularly those that employ HF, Ft, HCl, CI2, HBr, Bn, HI, and h as the halogénation source. Examples of preferred halogenated mono- and bi-valent metal oxides include, but are not limited to, fluorinated or chlorinated MgO, fluorinated or chlorinated CaO, fluorinated or chlorinated LLQ, fluorinated or chlorinated Naif), fluorinated or chlorinated Κ2Ο, and fluorinated or chlorinated (Ν2Ο. The catalyst may be supported or unsupported, such as with one or a combination of catalyst supports discussed herein. In certain embodiments, the catalyst includes a combination of fluorinated MgO with one or more of a fluorinated CS2O, a fluorinated LLQ, a fluorinated Na20, and/or a fluorinated Κ2Ο. in certain aspects of such embodiments, the fluorinated CS2O, fluorinated Li?0, fluorinated Na2.0, and/or fluorinated K >() is present in an amount of about 5.0 to about 50 wt %, based on the total weight of the catalyst .

The third class of catalysts is neutral (i.e., zero valent) metals, metal alloys, and their mixtures. The zero valent metals may include, but are not limited to, Pd, Pt, Rh, Ru, Ir, Os, Fe, Co, Ni, Cu, Mo, Cr, Μη, and combinations of the foregoing as alloys or mixtures. The catalyst may be supported or unsupported. Useful supports include, but are not limited to MgO, fluorinated MgO, MgF), carbon materials such as activated carbons and carbon molecular sieves, α-Αΐ2Ο3.111 certain embodiments, the catalyst includes a combination of MgO with one or more of Pd, Pt, Ru, Rh, and/or Ir. In certain aspects of such embodiments, Pd, Pt, Ru, Rh, and/or Ir are present in an amount of about 0.05 to about 5 wt %, based on the total weight of the catalyst.

Non-limiting examples of metal alloys include stainless steel alloys (304, 316, 316L, etc.), Monel alloys (400, 401, 404, etc.), Inconel alloys (600, 617, 625, 718, etc.), Hastelloy alloys (Β-2, C-4, C-22, C-276, etc.), and Incoloy alloys (800, 825, etc.). In certain preferred embodiments, the metal alloy catalyst is an Inconel alloy. In certain preferred embodiments, the catalyst is an Inconel 625 alloy. In one preferred embodiment, ainner,surface of a metal alloy reactor vessel, and in preferred embodiments an inner surface of the vessel can serve as catalyst for HCFC-123adehydrochlorination.

In addition to CFO-1113, the reaction product mixture may also have unconverted HCFC-123a and hydrogen chloride. In certain aspects, the final reaction product contains, prior to any distillation or purification, less than about 10 wt.% of organic by-product impurities, less than about 7 wt. % of organic by-product impurities, or less than about 5 wt. ℅ of organic by-product impuriti es, based on the total weight of the final product. Such organic by-product impurities may include any one or more compounds that inhibit the ability to convert HCFC-123a and/or the production (e.g. selectivity of) chlorotrifluoroethylene (CFO-1113), particularly at the levels discussed in greater detail below. In one embodiment, such organic by-product impurities include, but are not limited to, CFO-1112 isomers (e.g. l,2-dichloro-l,2-difluoroethylene), HFO-1123 (1,1,2-trifluoroethene), CFC-13 (chlorotrifluoromethane), CFC-12 (dichlorodifluoromethane), and G-124 isomer (2-chloro-l ,1,1,2-tetrafluoroethane). In certain preferred embodiments, the organic by-product impurities include CFO-1112 isomers, particularly 1,2-dichloro-1,2-difluoroethylene. .

According to certain preferred embodiments, the reaction product stream , prior to any distillation or purification, includes less than about 10 wt.% of CFO-1 ! 12, more preferably less than about 7 wt. % of CFO-1112, and even more preferably less than about 5 wt. % of CFO-1112, based on the total weight of the components in the reaction product stream . In certain preferred embodiments, the reaction of the present invention is conducted under conditions effective to ensure that the amount of organic by-product impurities, and preferably in certain embodiments, CFO-1112, is reduced prior to any purification or distillation, relative to the amount of impurities produced by reaction conditions that lie outside each of those preferred reaction conditions disclosed herein.

Greately enhanced or improved selectivity for CFO-113 is an unexpected but highly advantageous feature of the preferred aspects of the present invention. The dehydrochlorrnation reaction is, in certain preferred embodiments, preferably carried out under conditions effective to obtain a selectivity of at least about 70%, more preferably at least about 80%, and most preferably at least about 90%. The dehydrochlorrnation reaction is, in certain preferred embodiments, preferably carried out under conditions effective to obtain a conversion of at least about 5%, more preferably at least about 10%, and even more preferably at least about 15%. In certain highly preferred embodiments, the dehydrochlorination reaction is carried out under conditions effective to at once obtain a selectivity and a conversion according to any one of the preferred aspects described herein.

The dehydrochlorinating step may be conducted at any temperature and pressure that results in the product and preferably the advantages discussed herein. In certain aspects, dehydrochlorination may be carried out at a temperature range of about 200 °C to about 800 °C, and in certain embodiments from about 300 °C to about 600 °C. In certain embodiments, the temperature is about or greater than 400 °C, about or greater than 425 °C, or about or greater than 450 °C. In further embodiments, the temperature is within the range of from about 425 °C to about 525 °C in the presence of a catalyst. In certain aspects, the dehydrochlorinating step is conducted within a temperature range of from about 425 °C to about 550 °C, In further aspects, the dehydrochlorinating step is conducted within a temperature range of from about 480 °C to about 550 °C, and in further aspects, the dehydrochlorinating step is conducted within a temperature range of from about 480^UC to about 525 °C.

It is contemplated that a variety of reaction pressures may be used, such as superatmospheric, atmospheric, and subatmospheric. In certain aspects, atmospheric pressure is preferred.

Dehydrochlorination may optionally be earned out in presence or absence of an oxidizing agent. Useful examples of oxidizing agents include, but are not limited to, oxygen and carbon dioxide. Use of an oxidizing agent can extend the life of the catalyst. The oxidizing agent can be pure or diluted with an inert gas such as nitrogen before being introduced into reactor. The level of oxidizing agent is generally from about 1% to about 10% by volume and preferably from about 2% to 5% by volume based on the volume of the organic feed.

It may also be advantageous to periodically regenerate the catalyst after prolonged use while in place in the reactor. Regeneration of the catalyst may be accomplished by any means known in the art. One method is by passing oxygen or oxygen diluted with nitrogen over the catalyst at temperatures of about 200 °C to about 600 °C (in certain preferred embodiments from about 350 °C to about 450 °C) for about 0.5 hour to about 3 days followed by either halogénation treatment at temperatures of about 25 °C to about 400 °C (in certain preferred embodiments from about 200 °C to about 350 °C) for halogenated metal oxide catalysts and metal halide ones or reduction treatment at temperatures of about 100 °C to about 600 °C (preferably about 200 °C to about 350 °C) for metal catalysts.

Dehydrochlorination is preferably earned out in a corrosion-resistant reaction vessel.

Examples of corrosion-resistant materials are Hastelloy, Inconel, Monel and fluoropolymer linings. The vessel may have a fixed and/or a fluidized catalyst bed. If desired, inert, gases such as nitrogen or argon may be employed in the reactor during operation.

The following are examples of the present invention and are not to be construed as limiting.

About 40 ml of 10% CsCl/MgF₂ catalyst was charged into a V” X 0.035” tube Inconel 625 reactor.The reactor was installed in the middle of an electric 3-zone split furnace. Process temperatures w'ere recorded using a multi-point thermocouple placed inside the reactor and within the catalyst bed. The reactor was firstly heated to desired temperatures in nitrogen flow, and then a stream containing 94.6% pure HCFC-123a was fed into the bottom of the vertically mounted reactor at a feed rate of 12 g/h to start a reaction. The reactor pressure was set at 1 atm. The reactor effluent was periodically sampled and analyzed by GC-MS and GC for its compositions to determine raw material conversion level and product selectivity.

As shown in Table 1, both HCFC-123a conversion and CFO-1113 selectivity were increased with increasing temperature over the 10% CsCl/MgF? catalyst. At 500°C, on average, the HCFC-123a conversion and CFO-1113 selectivity were 16.2 and 96.7%, respectively. As a comparison, the empty Inconel 625 reactor provided a conversion of about 6% and a CFO-1113 selectivity of about 94% at the same 500°C.

¹ Other reaction conditions: Ô psig, 94.6% pure Ï23a feed, 12 g/h feed rate;

² Others include CFO-1112 isomers, HFO-1123, CFC-13, CFC-12, G-124 isomer, etc.

The above experimental protocol is performed using the following catalysts: 10% LiCl/MgF₂, 10% NaCl/MgF₂, 10% KCl/MgF₂, 10% LiF/MgF₂, 10% NaF/MgF₂, 10% KF/MgF₂ and 10% CsF/MgF₂. At or above 480 °C, each of these catalysts exhibits substantially the same conversion and selectivity percentages as the 10% CsCl/MgF? catalyst and exhibits similar impurity levels.

About 40 ml of fluorinated 15 wt% Cs₂0/MgO catalyst is loaded into the same %” X 0.035” tube Inconel 625 reactor as described in Example 1 for HCFC-123ad.ehydrochlorination.

The reactor is heated to 480°C in nitrogen flow. After the temperature is stabilized, 94.6% pure HCFC-123a feed is then passed through the catalyst bed at a rate of 12 grams/hour (g/h). The reactor pressure is set at 1 atm. As shown in Table 2, on average, the 15 wt% Cs20/MgO catalyst provides a HCFC-123a conversion of about 15% and a CFO-1113 selectivity of about 95%.

¹ Other reaction conditions: 0 psig, 94.6% pure 123a feed, 12 g/h feed rate;

² Others include CFO-1112 isomers, HFO-1123, CFC-13, CFC-12, G-124 isomer, etc.

The above experimental protocol is performed using the following catalysts: fluorinated 15 wt% LEO/'MgQ , fluorinated 15 wt% Na₂0/MgO, and fluorinated 15 wt% K₂0/Mg0. At or above 480 °C, each of these catalysts exhibits substantially the same conversion and selectivity percentages as the fluorinated 15 wt% Cs₂0/Mg0 and exhibits similar impurity levels.

40 ml of 1 wt% Pd/MgO catalyst is loaded into the same

%” X 0.035” tube Inconel 625 reactor as described in Example 1 for HCFC-123adehydrochlorination, The reactor is heated to 450°C in nitrogen flow. After the temperature is stabilized, 94.6% pure HCFC-123a feed is then passed through the catalyst bed at a rate of 12 grams/hour (g/h). The reactor pressure is set at 1 atm. As shown in Table 3, on average, the ! wt% Pd/MgO catalyst provides a HCFC-123a conversion of about 10% and a CFO-1113 selectivity of about 97%.

¹ Other reaction conditions: 0 psig, 94.6% pure 123a feed, 12 g/h feed rate;

² Others include CFO-1112 isomers, HFO-1123, CFC-13, CFC-12, G-124 isomer, etc.

The above experimental protocol is performed using the following catalysts: 1 wt%

Pt/MgO, lwt% Ru/MgO, 1 wt% Rh/MgO, and 1 wt% Ir/MgO.

At or above 450 °C, each of these catalysts exhibits substantially the same conversion and selectivity percentages as the 1 wt% Pd/MgO and exhibits similar impurity levels.