CONVERSION OF OXYGENATED ORGANIC COMPOUNDS TO FLUOROCARBONS AND ANHYDROUS HYDROGEN FLUORIDE USING URANIUM HEXAFLUORIDE

Abstract: A method of fluorination by reacting UF6 with a C2 to C8 alcohol, acids, esters, aldehydes or epoxides. The preferred reagent is a monohydroxyl or polyhydroxyl alcohol which does not form a chelate when reacted with UF6. The reaction is conducted in the presence of a fluorination catalyst in an amount sufficient to catalyze the reaction between the UF6 and the alcohol, acids, esters, aldehydes or epoxides.

Description: CONVERSION OF OXYGENATED ORGANIC COMPOUNDS TO FLUOROCARBONS AND ANHYDROUS HYDROGEN FLUORIDE USING URANIUM HEXAFLUORIDE BACKGROUND OF THE INVENTION Field of the Invention The invention pertains to the fluorination of oxygenated organic compounds by uranium hexafluoride in the presence of Group I - HI fluorides and transition metal fluorides to produce hydrogen fluoride, fluorocarbons, and uranium oxyfluorides and oxides. The fluorocarbons produced are of use as non-ozone depleting refrigerants, foam blowing agents, and solvents. Anhydrous hydrogen fluoride finds use as a catalyst and as a chemical intermediate, for example, for production of chlorofluorocarbons, hydrochlorofluorocarbons, and fluorocarbons including hydrofluorocarbons. Description of the Prior Art Uranium hexafluoride (UFg) is a selective and mild fluorinating agent that is in abundant supply worldwide, for example from the approximately 1.5 billion pounds of depleted UFg tailings that are remnants of the U.S. isotope enrichment process, and that await utilization or disposal around the world. There are no currently available large-scale methods to directly utilize the fluorine value of the uranium hexafluoride tails while simultaneously reducing the hazard of storing UFg inventories. It is known in the art to use magnesium or calcium to reduce UFg and produce uranium metal and metal fluoride salts having low-level radioactive contaminants that have no significant end-use. This is the so-called Ames process. Alternative methods produce large amounts of uranium oxides and aqueous hydrogen fluoride which is considered a chemical waste product because of a limited commercial market. At the same time, new, selective, and less expensive fluorinating agents are needed to supplement the current fluorination technology that is driving international efforts to produce fluorine chemicals that do not deplete atmospheric ozone, i.e. having zero ozone depletion value. The current technology to manufacture hydrochlorofluoro- carbons and fluorocarbons relies on fluorination of chlorinated hydrocarbon feed stocks using hydrogen fluoride (HF) and suitable catalysts. Because of selectivity problems with this approach, significant amounts of chlorinated by-products are produced which must either be sold in an increasingly competitive market or neutralized and disposed as waste. According to this invention, the problem of reducing the hazard of world UFg tails inventories might be solved by the use of more ss wasteful fluorinating agents by capitalizing on the fluorine value of UFg inventories and using the fluorinating abilities inherent in UFg. This invention captures the fluorine value in UF by using uranium hexafluoride to fluorinate oxygenated organic compounds in the presence of suitable metal fluoride salts to produce fluorocarbons. Oxygenated organic compounds can be deoxygenatively fluorinated using uranium hexafluoride. There has been a demonstrated need to remove UF tails in a cost-effective manner. Uranium hexafluoride has been known for use to fluorinate certain organic chemicals, principally halogenated organic chemicals. The literature makes note of several disclosures which refer to UFg-mediated fluorination of organohalides to synthesize chlorinated organofluorides. The vapor- and liquid-phase reduction of uranium hexafluoride using trichloroethylene to produce uranium tetrafluoride and chlorofluorocarbons is known. Schnautz, et al [S. African J. Chem. 1992, 45(2/3), 59-62] reported that the reaction between simple alcohols and uranium hexafluoride in the gas phase produced the corresponding hydrocarbon ethers by dehydrogenation, or fluorocarbons by deoxygenative fluorination. The uranium hexafluoride was converted to uranyl fluoride, UO2F2. EP O 503 792 Al teaches a process for the UF 6 -mediated replacement of hydrogen atoms for fluorine atoms in hydrohalocarbons. DE 4328606- Al teaches the use of UFg to fluorinate unsaturated hydrocarbons and chlorohydrocarbons to produce hydrofluorocarbons and hydrochlorofluorocarbons, respectively, with formation of UF4. US 3,382,049 teaches the reduction of UFg to UF4 using trichloroethylene to produce the hydrochlorofluorocarbons C2CI3F3 and C2CI3F2H from the reaction. L B. Asprey et al. "Fluorination Reactions of UFg"; J Fluor. Chem. 1982, 20(2), 277-280 described the reaction of UF 6 with alcohols, aldehydes, ketones, acids, acid halides, ethers, olefins, and alkanes without detailed accounts of the products obtained or conditions used. Shatolov et al "Use of Uranium Hexafluoride for making 1,2-Difluorotrichloroethane" Atomnaya Energaya, 1992, 72(2), 192-195 describe the reaction of UFg with trichloroethylene to produce uranium tetrafluoride and l,2,2-trichloro-l,2-difluoroethane in 99% yield. Goosen et al. "Reactions of Uranium Hexafluoride with Organic Substrates" S. Ar. Tydskr. Chem. 1987; 40(1), 30-34 describes the solution state reactivity of UFg toward organic compounds such as ketones and hydrocarbons, with no evidence of deoxygenative fluorination obtained using adamantanone, acetone, cyclohexanone, benzaldehyde and hep t anal. N.G Schnautz, et al, "Uranium Fluoride Chemistry. Part 1. The Gas Phase Reaction of Uranium Hexafluoride with Alcohols" S. Afr. Chem; 1992, 45(2/3), 59-62 describe the reaction of UFg with methanol, ethanol, trifluoroethanol, 1-propanol, and 2-propanol to produce fluoromethane, dimethyl ether, 1-fluoroethane, tetrafluoroethane, bis(trifluoromethyl)ether, 1-fluoropropane and 2-fluoropropane. US 3,235,608 to E.I.du Pont de Nemours & Co (1962) teaches the use of UFg to fluorinate alkanes, benzene and chloroalkanes in the presence of metal fluoride catalysts such as calcium fluoride, sodium fluoride, and potassium fluoride. None of these references teach the metal fluoride catalyzed multiple fluorination of C2 to Cg alcohols, acids, esters, aldehydes and epoxides to produce polyfluorinated hydrocarbons. Metal fluoride catalysts increase the number of fluorine atoms on carbon backbones compared to UFg alone, thereby increasing the value of the resulting fluorocarbon. The resulting uranium oxyfluorides and oxides can be subsequently converted to stable uranium oxides by known techniques SUMMARY OF THE INVENTION The invention provides a method of fluorination which comprises reacting UFg with a compound selected from the group consisting of C2 to Cg alcohols, acids, esters, aldehydes and epoxides, wherein the reaction is conducted in the presence of a fluorination catalyst in an amount sufficient to catalyze the reaction between the UFg and the alcohol, acid, ester, aldehyde or epoxide. The invention particularly provides a method of fluorinating an alcohol which comprises reacting UFg with a C2 to Cg monohydroxyl or polyhydroxyl alcohol, particularly those which do not form a stable chelate when reacted with UF5, wherein the reaction is conducted in the presence of a fluorination catalyst in an amount sufficient to catalyze the reaction between the UF6 and the alcohol. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As heretofore mentioned, the process of the invention fluorinates an alcohol, acid, ester, aldehyde or epoxide with UF in the presence of a fluorination catalyst. In the preferred embodiment, the reagent is a C2 to Cg alcohol, C2 to Cg acid, C2 to Cg ester, C2 to Cg aldehyde or C2 to Cg epoxide. In a more preferred embodiment, the reagent is a C2 to Cg and most preferably a C2 to C4 alcohol, acid, ester, aldehyde or epoxide. The preferred reagent according to this invention include C2 to Cg aliphatic or aromatic alcohols, acids, esters, aldehydes and epoxides. It is within the contemplation of this invention that each of these reagents may be unsubstituted or substituted with functional groups which do not materially interfere with the method which is the subject of the invention. Such substitutents may include, but are not limited to, functionalities derived from nitrogen, sulfur and halogens. Such may include, but are not limited to, cyano, nitro, ether, chlorine and bromine groups Such pendant groups may or may not take part in the inventive reaction. Non-exclusive examples of alcohols suitable for use according to this invention include primary alcohols such as ethanol and 1-propanol, secondary alcohols such as 2- propanol, tertiary alcohols such as tert-butyl alcohol, benzylic alcohols such as benzyl alcohol, diols such as ethylene glycol and 1,3-propanediol and polyols such as 1,2,4- butanediol. In the most preferred embodiment, the reagent is a monohydroxyl or polyhydroxyl alcohol, including polyols which do not form a stable chelate when reacted with UF . Non-exclusive examples of acids suitable for use according to this invention include alkyl carboxylic acids such as acetic acid and butyric acid, aromatic carboxylic acids such as benzoic acid and alkyl dicarboxylic acids such as malonic acid. Non-exclusive examples of esters suitable for use according to this invention include saturated alkyl carboxylic acid esters such as methyl acetate and ethyl acetate, and aryl carboxylic acids such as methylbenzoate, ethylbenzoate and phenyl benzoate. Primary, secondary and tertiary esters are useful. Non-exclusive examples of aldehydes suitable for use according to this invention include unsaturated alkyl aldehydes such as acetaldehyde and butyraldehyde and aromatic aldehydes such as benzaldehyde. Non-exclusive examples of epoxides suitable for use according to this invention include saturated aliphatic epoxides such as ethylene oxide, propylene oxide and cyclohexene oxide as well as aromatic epoxides such as 1,2-epoxyethylbenzene Some oxygen containing organic compounds have been found not to function according to this invention. For example, ethers and ketones such as diethyl ether and acetone cannot be fluorinated satisfactorily by the inventive method. The alcohol, acid, ester, aldehyde or epoxide is preferably present in a mole ratio of alcohol, acid, ester, aldehyde or epoxide to UFg which ranges from about 0.5: 1 to about 5: 1 or more preferably from about 2:1 to about 3:1. PCΪYUS95/15076 The reaction is conducted in the presence of a fluorination catalyst to catalyze the reaction between the UFg and the alcohol, acid, ester, aldehyde or epoxide. The fluorination catalyst is preferably a Group I, Group II, Group III or transition metal fluoride. Preferred fluorination catalysts are sodium, potassium, calcium, magnesium, chromium and aluminum fluoride with calcium fluoride being most preferred Other fluorination catalysts non-exclusively include Cu(0), BF3, Ag(0)/Cu(O), Au(O)/Cu(O), FeC13/C, HF/Al 2 O 3 , AIF3, CrF 3 , MnF 2 , FeF 3 , CoCl 2 , NiF 2 , ZrF 4 , ThF 4 , HF/Cr 2 O 3 , HF/Crθ3F2, HF/SbC^/C, and HF/SnCl4. The fluorination catalyst is present in an amount sufficient to catalyze the reaction between the UFg and the alcohol, acid, ester, aldehyde or epoxide. The fluorination catalyst is preferably present in a mole ratio of UF to catalyst ranging from about 1000: 1 to about 1 : 1 or more preferably from about 20:1 to about 1 : 1. In the preferred embodiment, the reaction is conducted at a temperature of from about 15 °C to about 800 °C, or more preferably from about 75 °C to about 200 °C. In the preferred embodiment, the reaction is conducted at a pressure of from about -15 psig to about 500 psig, or more preferably from about 50 psig to about 150 psig. In the preferred embodiment, the reduction is conducted for from about .1 hours to about 48 hours, or more preferably from about 0.5 hours to about 8 hours depending on the substrate. In a flow configuration, this corresponds to a liquid hourly space velocity ranging from about 0.02 to about 10 or more preferably from about 0.1 and about 2 The most advantageous reaction time may be determined by those skilled in the art In the preferred embodiment, the reaction is conducted in an inert atmosphere such as nitrogen or argon. The reaction can be conducted in a batch mode or continuous reactor configuration and in gas phase or liquid phase. When conducted in a liquid phase, it may be conducted with a suitable solvent which is preferably an excess of the alcohol, acid, ester, aldehyde or epoxide. The following non-limiting examples serve to illustrate the invention. Example 1 (Comparative) Reaction of 2-propanol + CaF2 A 10-ml Hoke stainless steel single-neck sample cylinder was charged with 0.1 16 g (1.5 mmol) calcium fluoride under a nitrogen atmosphere and was attached to a stainless steel vacuum manifold equipped with a pressure sensing transducer. The reactor was purged with helium three times and evacuated. 2-Propanol (1.787 g, 29 7 mmol) that had been previously dried over 3 Angstrom moiecular sieves was vacuum transferred into the reactor following multiple freeze-pump-thaw cycles. The reactor was closed, warmed to ambient temperature (22.6°C) and re-evacuated after cooling to liquid nitrogen temperature. The reactor was sealed again and warmed to 100°C Over eight hours the pressure increased from -12 psig to 80 psig (calibrated 0 psig = 1 atm.). The reactor was to cooled ambient temperature and a residual pressure of 23 psig was noted. The reactor was cooled to liquid nitrogen temperature, evacuated, and volatile materials were vacuum transferred into a receiving flask. Analysis by gas chromatography indicated only 2-propanol present in the raw reaction mixtures. Example 2 (Comparative) Reaction of 2-propanol + UFg A 10-ml Hoke stainless steel single-neck sample cylinder was attached to a stainless steel vacuum manifold equipped with a pressure sensing transducer and was charged with 1.08 g (3.1 mmol) uranium hexafluoride and 0.728 g (12.1 mmol) of 2-propanol by vacuum transfer. The reactor was chilled to liquid nitrogen temperature and evacuated. The reactor was sealed and warmed to 100°C. Over eight hours the pressure increased from -12 psig to 105 psig (calibrated 0 psig = 1 atm). The reactor was cooled to ambient temperature and a residual pressure 29 psig was noted. The reactor was cooled to liquid nitrogen temperature, evacuated and all volatile materials were vacuum transferred into a receiving flask containing ca. 1.5 g. sodium fluoride as a scavenger of hydrogen fluoride. Approximately 1 g methylene chloride was transferred into the product receiving flask to facilitate analysis. Analysis by gas chromatography, gas chromatographic mass spectrometry, and *^F NMR spectrometry indicated conversion of 2-propanol to 2-fluoropropane and diisopropyl ether. Example 3 Reaction of 2-propanol + UFg + CaF2 A 10-ml Hoke stainless steel single-neck sample cylinder was charged with 0.032 g (0.4 mmol) calcium fluoride under an nitrogen atmosphere and was attached to a stainless steel vacuum manifold equipped with a pressure sensing transducer. The reactor was evacuated and charged with 2.16 g (6.1 mmol) uranium hexafluoride and 1.007 g (16.8 mmol) 2-propanol by vacuum transfer. The reactor was chilled to liquid nitrogen temperature and evacuated. The reactor was sealed and warmed to 100°C. Over three hours the pressure increased from 2 psig at ambient temperature to 206 psig (calibrated 0 psig = 1 atm.) then dropped to 114 psig over an additional two hours. The reactor was cooled to ambient temperature and a residual pressure 31 psig was noted. The reactor was cooled to liquid nitrogen temperature, evacuated, and all volatile materials were vacuum transferred into a receiving flask containing ca 1.6 g sodium fluoride as a scavenger of hydrogen fluoride. Approximately 2 g carbon tetrachloride was transferred into the product receiving flask to facilitate analysis. Analysis by gas chromatography, gas chromatographic mass spectrometer, and ^F NMR spectrometry indicated conversion of 2-propanol to 1, 1 difluoropropane, 2- fluoropropane and trace amounts of diisopropyl ether. Example 4 Reaction of 1-propanol + UF5 + CaFo Using the procedure of Example 3, reaction of 0.049 g (0.6 mmol) CaF2 with 1.190 g (19.8 mmol) 1-propanol and 2.75 g (7.8 mmol) UFg produced 1-fluoropropan as the major hydrofluorocarbon with a mixture of 1,1 and 2,2-difluoropropanes, and dipropyl ether and trace amounts of diisopropyl ether present. EXAMPLE 5 (Comparative) Reaction of dimethylketone + UFg The procedure of Example 3 was followed except the reactants were 0.406 g (7.0 mmol) dimethyl ketone and 2.44 g (6.9 mmol) UFg and there was no reactor charging with CaF2- No volatile products were observed. This example demonstrates that a dimethylketone could not be fluorinated satisfactorily. EXAMPLE 6 (Comparative) Reaction of Dimethylketone + UF + CaF2 Using the procedure of Example 3, 0.861 g (14.8 mmol) dimethyl ketone reacted with 1.71 g (4.9 mmol) UFg in the presence of 0.051 g (0.7 mmol) CaF2 with produced no detectable volatile products. This example demonstrates that a dimethylketone could not be fluorinated satisfactorily even in the presence of a fluorination catalyst. Example 7 (Comparative) Reaction of 1.3-Propanediol + CaF2 Using the procedure of Example 1, 0.112 g (1.4 mmol) of CaF2 were reacted with 0.834 g (1 1.0 mmol) 1,3-propanediol and produced no pressure increases and no detectable amounts of volatile materials. This example demonstrates no reactivity toward calcium fluoride. EXAMPLE 8 (Comparative) Reaction of 1.3-Propanediol + UFg Using the procedure of Example 2, 0.613 g (8.1 mmol) of 1,3-propanediol reacted with 2.32 g (6.6 mmol) UF produced a pressure increase of -12 psig to 54 psig over eight hours. No volatile materials were detected. This example demonstrates the production of a stable chelate. EXAMPLE 9 Reaction of 1.3-Propanediol + UF5 + CaF2 Using the procedure of Example 3, 0.601 g (7.9 mmol) 1,3-propanediol reacted with 2.35 g (6.7 mmol) UFg in the presence of 0.05 g (0.6 mmol) CaF2 at 100°C produced a pressure increase from 12 to 70 psig after 1 hour. Volatile materials were vacuum transferred from the reaction vessel. Analysis by g e m s, and ^F NMR indicated the conversion of the 1,3-propanediol into a mixture of tetra- and pentafluoropropanes, i.e. 1, 1,3,3-tetrafluoropropane and 1, 1,2,3,3-pentafluoropropane. EXAMPLE 10 Reaction of Ethylene oxide + UF5 + CaF2 Example 3 is repeated except the reaction of ethylene oxide and UFg in the presence of a catalytic amount of CaF2 produces 1, 1-difluoroethane. EXAMPLE 11 Reaction of Cyclohexene + UF + CaF2 Example 3 is repeated except the reaction of cyclohexene and UF in the presence of a catalytic amount of CaF2 produces 1,1 -difluorocyclohexane. EXAMPLE 12 Reaction of Methylacetate + UF5 + CaF2 Example 3 is repeated except the reaction of methylacetate and UFg in the presence of a catalytic amount of CaF2 produces 1,1,1-trifluoroethane. EXAMPLE 13 Reaction of Ethyl benzoate + UF5 + CaF2 Example 3 is repeated except the reaction of ethyl benzoate and UFg in the presence of a catalytic amount of CaF2 produces 1, 1-trifluoromethylbenzene EXAMPLE 14 Reaction of Acetic acid + UFg + CaFo Example 3 is repeated except the reaction of acetic acid and UFg in the presence of a catalytic amount of CaF2 produces 1,1, 1-trifluoroethane. EXAMPLE 15 Reaction of Malonic acid + UFg + CaF^ Example 3 is repeated except the reaction of malonic acid and UFg in the presence of a catalytic amount of CaF2 produces 1, 1, 1,3,3,3-hexafluoropropane. EXAMPLE 16 Reaction of Acetaldehyde + UFg + CaF2 Example 3 is repeated except the reaction of acetaldehyde and UFg in the presence of a catalytic amount of CaF2 produces 1,1,1-trifluoroethane. EXAMPLE 17 Reaction of Benzaldehyde + UFg + CaF2 Example 3 is repeated except the reaction of benzaldehyde and UFg in the presence of a catalytic amount of CaF2 produces 1,1, 1-trifluoromethylbenzene.

Claims: What is claimed is: 1. A method of fluorination which comprises reacting UFg with a compound selected from the group consisting of C2 to Cg alcohols, acids, esters, aldehydes and epoxides, wherein the reaction is conducted in the presence of a fluorination catalyst in an amount sufficient to catalyze the reaction between the UFg and the alcohol, acid, ester, aldehyde or epoxide. 2. The method of claim 1 wherein UFg is reacted with a compound selected from the group consisting of C2 to C4 alcohols, acids, esters, aldehydes and epoxides. 3 The method of claim 1 wherein UFg is reacted with a compound selected from the group consisting of ethylene oxide, cyclohexene oxide, methyl acetate, ethylbenzoate, acetic acid, malonic acid, acetaldehyde, and benzaldehyde. A method of fluorinating an alcohol which comprises: reacting UFg with a C3 to Cg monohydroxyl or polyhydroxyl alcohol, wherein the reaction is conducted in the presence of a fluorination catalyst in an amount sufficient to catalyze the reaction between the UFg and the alcohol. The method of claim 4 wherein the alcohol does not form a stable chelate when reacted with UFg. 6. The method of claim 4 wherein the alcohol is a C2 to Cg monohydroxyl or polyhydroxyl alcohol. 7. The method of claim 4 wherein the alcohol is selected from the group consisting of 1-propanol, 2-propanol and 1,3-propanediol. 8. The method of claim 1 wherein the fluorination catalyst is selected from the group consisting of Group I, Group II, Group III and transition metal fluorides The method of claim 1 wherein the fluorination catalyst is selected from the group consisting of sodium, potassium, calcium, magnesium, chromium and aluminum fluoride. 10. The method of claim 1 wherein the alcohol is selected from the group consisting of 1-propanol, 2-propanol and 1,3-propanediol and the fluorination catalyst is calcium fluoride.

Inventors: HEWES JOHN, KOCUR MICHAEL, ROBERTSON ALEXANDER, HEWES, JOHN, KOCUR, MICHAEL, ROBERTSON, ALEXANDER
Applicants: ALLIED SIGNAL INC, ALLIEDSIGNAL INC.
Application year: 1995
Main classification: C07B39
IPC codes: B01J27, C07B39, C07B61, C07C17, C07C19