PROCESS FOR THE PREPARATION OF FLUOROXY HALO COMPOUNDS

Abstract: Fluoroxy-halo-compounds are prepared by direct reac­ tion between fluorine and organic compounds having a molecular structure in which at least one oxygen atom is directly bound to a carbon atom in the carbonylic form, in the presence of a fluorination catalyst, in a gaseous phase, at an absolute pressure of between 50 and 800 kPa and at a temperature higher than -50°C and up to 150°C, under conditions of continuous feeding of the reactants and a continuous removal of the reaction product.

Description: The present invention concerns a process for the preparation of fluoroxy-halo-compounds. More particularly the present invention refers to a continuous process for the preparation of fluoroxy-halo-compounds of the formula: (R) n C(F) m -O-F (I) wherein R is: an alkyl or cycloalkyl radical containing from 1 to 12 carbon atoms, either partially or fully halogenated with bromine, chlorine, and/or fluorine or R is a perfluoromonoether or perfluoropolyether radical containing from 1 to 12 carbon atoms; n is 1 or 2; m is equal to 3-n; it being understood that the value n=2 comprises the compounds in which C is part of a cyclic ring. Fluoroxy-halo-compounds comprised by the above indicated general formula (I) are quite well known in the literature and described in U.S. Patent US-A-3,442,927, by John R. Ruff et al. in J.A.C.S. , 88:19, Oct. 5, 1966 pages nos. 4531-4532, and by Lustig et al. in J.A.C.S. 89:12, June 7, pages 2841-2843. These compounds find a useful application as oxidizers, for example in the bleaching, as oxidizing agents in organic syntheses in various different applicational fields, as oxidizers in propellants, and as fluorinating agents. Fluoroxy-halo-compounds have, so far, been considered difficult to produce, mainly because of their high instability. Due to the high instability of the products, the various processes proposed for their preparation are conducted under such drastic and limitative conditions as not to find a practical industrial application. In fact, operating according to the known processes, there are obtained very low yields (∼ 2%), or it is necessary to operate at very low reaction temperatures, in general at -78°C, or the reaction is not selective and one gets the formation of by-products that subsequently have to be removed. At any rate, the known processes all operate in a discontinuous way and with very low quantities of reactant. Thus, for instance, in J.A.C.S. 80:19 - Oct. 5, 1966 on pages 4531 to 4532 and in J.A.C.S. 89:12 - June 7, 1967 on pages 2841 to 2843 there is described the preparation of fluoroxyalkanes by the catalytic addition of fluorine on the double carbon/oxygen bond in a perfluorocarbonyl compound according to the scheme: wherein: R₁ and R₂ may be, independently from each other, fluorine or a perfluoroalkyl radical while M is K, Na, Rb or Cs. The reaction is conducted in a discontinuous way, on small quantities, at a low temperature (-78°C), at a reduced absolute pressure of 10-20 kPa, and in long times. Although the process allows one to obtain high yields (up to 98%), the quantity of obtainable fluoroxy-alkanes does not exceed 10 mM (millimoles) per charge (batch). US-A-3,442,927 describes a process for the production of fluoroxy-compounds by direct reaction in a discontinuous way of fluorine with oxygen-containing compounds whose oxygen is directly bound to carbon, at temperatures comprised between -100°C and +50°C, in which process the desired products are isolated from the reaction mixture by fractioned condensation using separators refrigerated with dry ice, liquid air, ice-salt for the low-boiling products, and other suitable temperature conditions for the high-boiling liquids. The fluorine and the other gases are introduced into the reaction medium, under a slight pressure, and the reaction time is between 10 minutes and 12 h. The main drawbacks of this process consist in the lack of selectivity, in low yields, and in the necessity of carrying out the fractioned separation of the products obtained, at a low temperature and under perfectly clean conditions in order to avoid explosive decomposition of the fluoroxy-compounds which, as is well known, is provoked by traces of pollutants. Moreover, also in this process the reaction is conducted in a discontinuous way and on small quantities of product. Thus, what is desired is a process for the preparation of fluoroxy-compounds that will not display the above mentioned drawbacks, more particularly, an industrial process for the preparation of fluoroxy-compounds. The industrial process should allow one to produce in a selective way and with high yields, the desired fluoroxy compound. It should also be possible to obtain fluoroxy-compounds with a high productivity and high purity without requiring subsequent isolation and/or manipulation, so as to avoid the risks and limitations connected with their high instability. We have now found, surprisingly, that these aims can be achieved by carrying out a direct reaction between fluorine and an organic compound having a molecular structure in which at least one atom of oxygen is directly bound to a carbon atom in the carbonylic form, in the presence of a fluorination catalyst, in a gaseous phase and in such conditions as to obtain the fluoroxy-halo-compound in the gaseous state, at an absolute pressure comprised between 50 and 800 kPa, at a temperature greater than -50°C and up to 150°C, under conditions of continuous feeding of the reactants and continuous removal of the reaction product, so that the mean dwell time of the reactants in the reaction medium is less than 10 minutes, and under conditions of removal of the reaction heat, in order to maintain the temperature at values of not more than 150°C. The gaseous mixture fed to the reaction may contain a diluent. The operational conditions of the reaction, including the possible dilution conditions, are chosen in such a way that the starting carbonyl compound and the obtained fluoroxy-halo-compound are both in the gaseous state. According to a preferred embodiment of the present invention, the fluorination reaction is conducted by continuously passing the reactants in a gaseous phase through a layer containing the catalyst and capable of ensuring the attainment of the required heat exchange. The compound having a molecular structure in which at least one oxygen atom is directly linked to a carbon atom in a carbonylic form, may be more specifically represented by the formula: (R) n C(X) m-1 O (II) wherein:· O represents an oxygen atom directly linked to carbon, X represents fluorine or chlorine, while R , n , and m have the same values and meanings as indicated previously above. When R contains H and/or Br, it is preferred to operate the reaction at a temperature not higher than 50°C. The compounds in which R represents a perfluoro-alkyl radical having from 1 to 5 carbon atoms or a perfluoromonoether or perfluoropolyether radical having from 1 to 5 carbon atoms are preferred compounds in the process of the present invention. Examples illustrating the starting compounds to be submitted to the fluorination process according to the present invention are: fluoride and chloride of trifluoro-acetyl; fluoride and chloride of chloro,difluoro-acetyl; fluoride and chloride of trichloro-acetyl; fluoride and chloride of bromo,difluoro-acetyl; fluoride and chloride of penta fluoro-propionyl; fluoride and chloride of heptafluoro-butyryl; hexafluoroacetone; and perfluoroetoxy-difluoro-acetyl-fluoride, perfluorometoxy-difluoro-acetylfluoride, and a mixture thereof. The reactants are continuously fed in, in gaseous phase, preferably under a slight pressure and in equimolar quantities, with flow rates for each reactant greater than 5.10⁻⁶ mol/h per gram of catalyst. Flow rates for each reactant that are between 10⁻⁴ and 10⁻¹ mol/h per gram of catalyst are preferred. The reactants are preferably diluted with an inert gas in order to obtain concentrations comprised between 5% and 70% by volume. As an inert gas there may be used any gas or vapour that is non-reactive with the reactants and the reaction products such as, for instance, nitrogen, argon, helium, tetrafluoromethane, dichlorotetrafluoroethanes, pentafluorochloroethane, difluorodichloromethane, perfluorocyclobutane, etc. As a catalyst there may be used any kind of known fluorination catalyst, particularly caesium fluoride, rubidium fluoride, potassium fluoride, lithium fluoride, or sodium fluoride; a caesium fluoride is the preferred one. In order to remove the reaction heat and achieve the required heat exchange, the process may be carried out in the presence of a metallic material substantially inert to fluorine, or carried out in a metal reactor having such a geometric configuration as to ensure the required heat exchange. Amongst the metallic materials suited for the purpose we would cite before all and preferably copper and its alloys such as brass and Monel, although also other materials may be used. The catalyst can be mixed with the metallic material, the material being in the form of chips (shavings), Raschig rings, or similar filling bodies or can be supported on the metallic material which is in one of the abovesaid forms. It is also possible to use the catalyst both mixed with the metallic material and supported on it. According to a preferred embodiment of the present invention, the catalyst is intermingled (mixed) with the metal material and/or supported on it, the metal material being in the form of shavings, Raschig rings or similar filling bodies, and the reactants, in gaseous phase and diluted in an inert gas, are made to continuously pass through a fixed layer of the metallic material catalyst, with such a flow speed as to maintain the dwell time in the reactor below 10 minutes, keeping the reaction temperature at a value between -20°C and 100°C, but preferably between 20°C and 60°C, while the absolute pressure is between 100 and 200 kPa. In order to regulate (control) the reaction temperature, any known suitable means may be used, for instance a thermostatic bath. The gaseous mixture that goes to the reaction should be well purified from HF and H₂O and from the acid or dialcohol that can form by hydrolysis of the starting carbonylic compound. More precisely the inert gas should be purified from H₂O, the F₂ from HF, and the starting carbonylic compound from HF and from the possible acid or dialcohol. The process of the present invention allows one to obtain the full conversion of the reactants with stoichiometric yields in a pure fluoroxy-compound which does not need any successive operations for its isolation or purification. The fluoroxy compounds obtained according to the process of the present invention find their useful application in condensation and/or fluorination reactions of the most various organic substrates (compounds) such as: olefines, unsaturated compounds, organic compounds having hydrogen or functional groups that can be substituted with fluorine, etc., or they may be decomposed with the formation of COF₂ and of the corresponding halogeno-compound. In order to give a better understanding of the invention and its practical actuation, a series of illustrative but not limiting examples follow. Example 1 Into a brass reactor, having a diameter of 50 mm and a useful holding capacity of 500 cm³, completely filled with copper chips (shavings) intermingled with 300 g of CsF (dried at 250°C in a nitrogen flow during 4 hours, milled, and screened in a dry box in order to obtain a granulometry between 250 and 500 micron), there was fed continuously a mixture of N₂/F₂/CF₃COF (purified from HF, H₂O, and the acid or dialcohol that can form by hydrolysis of the starting carbonylic compound) in a molar ratio equal to 3.75/1/1, at a global flow rate of 23 Nl/hr (6.10⁻⁴ mol/h per g of catalyst for each reactant) and at an absolute pressure of 110 kPa. The temperature inside the reactor was kept at -10°C by means of external cooling. The gaseous mixture flowing out of the reactor, after analysis by IR spectrophotometry and iodometry, proved to consist of N₂/CF₃CF₂OF in a molar ratio of 3.75/1, with a 100% conversion and a 100% yield of perfluoro-ethoxy-fluoride. After 400 hours of operation, the conversion of the reactants and the yield remained unvaried. On increasing the temperature inside the reactor to +20°C or increasing the absolute pressure to 500 kPa, the conversions and the yields remained unvaried at the value of 100%. Example 2 Into the reactor described in Example 1, there was continuously fed a gaseous mixture consisting of: N₂/F₂/CF₃COF (purified as indicated above) in a molar ratio of 1/1/1, at a global flow rate of 12 Nl/h (6.10⁻⁴ mol/h per gram of catalyst for each reactant) and at an absolute pressure of 110 kPa. The temperature inside the reactor was maintained at +20°C by means of a thermostatically controlled bath. The gaseous mixture flowing out of the reactor, analysed by means of IR spectrophotometry and iodometry, proved to consist of N₂/CF₃CF₂OF in a molar ratio of 1/1, with 100% conversion and yield. Even after several weeks of operation, no variations in the conversion and/or yield could be noticed. Example 3 Into the same reactor as that of Example 1, there was continuously fed a gaseous mixture of N₂/F₂/CClF₂COF (purified as indicated above) in a molar ratio of 3.75/1/1, at a total flow rate of 23 Nl/h (6.10⁻⁴ mol/h per gram of catalyst for each reactant) and at an absolute pressure of 110 kPa. The temperature inside the reactor was maintained at 20°C. The gaseous mixture flowing out of the reactor, analyzed by means of IR spectrophotometry and iodometry, proved to consist of N₂ and CClF₂-CF₂OF in a molar ratio of 3.75/1, with a 100% conversion and a 100% yield of 2-chloro-tetrafluoro-ethoxy-fluoride. The yield and the conversion remained unvaried after several weeks. Example 4 Into an AISI 316 reactor of 25 mm diameter and of 500 cm³ holding capacity, completely filled with Raschig copper rings of 4 mm size, intermingled with 300 g of CsF (treated as Indicated in Example 1), was fed continuously a gaseous mixture of N₂/F₂/CF₃COF (purified as indicated above) in a molar ratio of 30/2/1, at a total flow rate of 16.5 Nl/h (7.4.10⁻⁵ mol/h of CF₃COF per gram of catalyst and 14.9.10⁻⁵ mol/h of fluorine per gram of catalyst), and at an absolute pressure of 110 kPa. The temperature inside the reactor was kept at 135°C by means of a thermostatic bath. The outflowing gases were analyzed by IR spectrophotometry and iodometry, and they proved to consist of N₂ and CF₃CF₂OF with complete conversion of CF₃COF into CF₃CF₂OF. Example 5 Into the reactor described in Example 4, was continuously fed a gaseous mixture consisting of C₂ClF₅/F₂/CF₃COF (purified as indicated above) in a molar ratio of 1/1/1, at a total flow rate of 45 Nl/h (2.2.10⁻³ mol/h per gram of catalyst for each reactant), and at an absolute pressure of 110 kPa. The temperature in the reactor was kept at 20°C by means of external cooling. The outflowing gaseous mixture, analyzed by means of IR spectrophotometry and iodometry, proved to consist of C₂ClF₅/CF₃CF₂OF in a molar ratio equal to 1/1, with a 100% conversion and a 100% yield of pentafluoro-ethoxy-fluoride. Example 6 Into the same reactor as that of Example 1, there was continuously fed a gaseous mixture of N₂/F₂/CF₃COCl (purified as indicated above) in a molar ratio of 3.75/1.5/1, at a global flow rate of 25 Nl/h (9.10⁻⁴ mol/h of fluorine per gram of catalyst and 6.10⁻⁴ mol/h of CF₃COCl per gram of catalyst) and at an absolute pressure of 110 kPa. The temperature inside the reactor was maintained at 30°C by external cooling. The outflowing gaseous mixture, analyzed by means of IR spectrophotometry and iodometry and titration of chlorides, proved to consist of N₂/CF₃CF₂OF/Cl₂ in a molar ratio of 7.5/2/1, with a 100% conversion and a 100% yield of pentafluoro-ethoxy fluoride. Example 7 Into the reactor of Example 1, there was continuously fed a gaseous mixture of N₂/F₂/(CF₃)₂CO (purified as indicated above) in a molar ratio of 3.75/1/1, at a global flow rate of 23 Nl/h (6.10⁻⁴ mol/h per gram of catalyst for each reactant), and at an absolute pressure of 110 kPa. The temperature inside the reactor was maintained at 20°C by external cooling. The outflowing gaseous mixture, analyzed by IR spectrophotometry and iodometry, proved to consist of N₂/(CF₃)₂-CF-O-F in a molar ratio of 3.75/1, with a 100% conversion and yield. Example 8 Into the reactor of Example 1, there was continuously fed a gaseous mixture of N₂/F₂/CF₃-CF₂-COF (purified as indicated above) in a molar ratio of 3.75/1/1, at a global flow rate of 23 Nl/h (6.10⁻⁴ mol/h per gram of catalyst for each reactant), and at an absolute pressure of 110 kPa. The temperature inside the reactor was maintained at 20°C by external cooling. The outflowing gaseous mixture, analyzed by IR spectrophotometry and iodometry, proved to consist of N₂/CF₃-CF₂-CF₂-OF in a molar ratio of 3.75/1, with a 100% conversion and yield. Example 9 Into the reactor of Example 1, there was continuously fed a gaseous mixture of (purified as indicated above) in a molar ratio of 3.75/1/1, at a global flow rate of 23 Nl/h (6.10⁻⁴ mol/h per gram of catalyst for each reactant), and at an absolute pressure of 110 kPa. The temperature inside the reactor was maintained at 20°C by external cooling. The outflowing gaseous mixture, analyzed by IR spectrophotometry and iodometry, proved to consist of in a molar ratio of 3.75/1, with a 100% conversion and yield.

Claims: A process for the preparation of a fluoroxy-halo-compound of the formula: (R) n C(F) m -O-F (I) wherein either R is an alkyl or cycloalkyl radical containing from 1 to 12 carbon atoms, partially or fully halogenated with bromine, chlorine, and/or fluorine or R is a perfluoromonoether or perfluoropolyether radical containing from 1 to 12 carbon atoms, n=1 or 2, and m=3-n, it being understood that when n is 2 the formula includes compounds in which C is part of a cyclic ring, the said fluoroxy-halo-compound being prepared by direct reaction, in the presence of a fluorination catalyst, between fluorine and an organic compound having a molecular structure in which at least one oxygen atom is directly linked to a carbon atom in the carbonylic form, characterized in that the reaction is conducted in gaseous phase and in such conditions as to obtain the fluoroxy-halo-compound in the gaseous state, at an absolute pressure of 50 to 800 kPa, at a temperature higher than -50°C and up to 150°C, under conditions of continuous feeding of the reactants and continuous removal of the reaction product, so that the dwell time of the reactants in the reaction medium is less than 10 minutes, and under conditions of removal of the reaction heat in order to prevent the temperature exceeding 150°C. A process as claimed in claim 1, in which the said organic compound, having a molecular structure wherein at least one oxygen atom is directly linked to a carbon atom in the carbonylic form, is of the formula: (R) n C(X) m-1 O (II) wherein: O represents an oxygen atom directly linked to the carbon; X represents fluorine or chlorine; and R , m , and n have the same values and meanings as in formula (I). A process as claimed in claim 1 or 2, in which R represents a perfluoro-alkyl radical having from 1 to 5 carbon atoms or a perfluoromonoether or perfluoropolyether radical having from 1 to 5 carbon atoms. A process as claimed in any preceding claim, in which the reaction between the fluorine and the said organic compound, having a molecular structure in which at least one oxygen atom is directly bound to a carbon atom in the carbonylic form, is conducted by means of continuous passage of the reactants in gaseous phase through a fixed bed containing the catalyst and capable of ensuring the required thermal exchange. A process as claimed in any preceding claim, conducted in the presence of a metallic material substantially inert to fluorine. A process as claimed in claim 5 when dependent on claim 4, in which the catalyst is intermingled with the metallic material, the metallic material being in the form of chips, Raschig rings, or similar filling bodies, and/or is supported on the metallic material. A process as claimed in claim 5 or 6, in which the metallic material is copper or an alloy thereof, e.g. brass or Monel. A process as claimed in any preceding claim, in which each reactant is fed in with a flow rate greater than 5.10⁻⁶ mol/h per gram of catalyst. A process as claimed in claim 8, in which the flow rate for each reactant is 10⁻⁴ to 10⁻¹ mol/h per gram of catalyst. A process as claimed in claim 1, in which the catalyst is intermingled with metallic material substantially inert to fluorine in the form of chips, Raschig rings or similar filling bodies, and/or supported on the metallic material, and the reactants, in gaseous phase and diluted in an inert gas, are continuously passed through a fixed layer of the metallic material/catalyst at a speed corresponding to a dwell time in the reactor below 10 minutes, while maintaining a reaction temperature of -20°C to +100°C, preferably 20°C to 60°C, while the absolute pressure is 100 to 200 kPa.

Inventors: CARLINI, FILIPPO MARIA, CONTE, LINO, GUGLIELMO, GIORGIO
Applicants: AUSIMONT S.P.A.
Application year: 1986
Main classification: C07C71
IPC codes: C07C71, C07C201, C07C69, B01J27, C07C67, C07B61, C07C41, C07C31, C07C29, C07C43