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Home , Calcium fluoride, Carbon tetrafluoride, Chlorotrifluoromethane, Dichlorodifluoromethane, Difluoromethane, Fluoromethane

2,757,214 United States Patent Office Patented July 31, 1956

1 2 - formed according to the following equation, again usin 2,757,214 : - NEW PROCESS FOR PREPARING CHLORO FLUORO METHANES FROM 2CaF2-4-3COCI2->2COFC1-COF2--2CaCl2 AND A METAL FLUORIDE 5 It is also possible that part or all of the carbonylfluoride Earl L. Muetterties, Hockessin, Del, assignor to E. I. du results from the carbonyl chlorofluoride initially formed Pont de Nemours and Company, Wilmington, Del, a since it has been found experimentally that carbonyl corporation of Delaware chlorofluoride disproportionates at elevated temperature to give and other products. For exam No Drawing. Application February 18, 1955, 0. ple, when carbonyl chlorofluoride is heated at 500 C. Serial No. 489,295 for one hour under autogenous pressure in a corrosion d resistant bomb, the resulting gaseous product is found by 7 Claims. (CI. 260-653) infrared analysis to contain carbonyl fluoride, carbonyl chlorofluoride, phosgene, dioxide. A similar dis This invention relates to a new process of preparing 5 proportionation of carbonyl chlorofluoride (0.34 mole) -containing organic compounds. More particu takes place in the presence of finely divided calcium fluo larly, it relates to a process of preparing completely halo ride (0.68 mole) at 500 C. for one hour under autoge genated methanes in which at least one of the nous pressure, and in this case the product contains atoms is fluorine, any other halogen being chlorine. 20% carbonyl fluoride, 35% carbonyl chlorofluoride, These compounds will be referred to hereinafter as fluo 20 10% phosgene, 15% , 5% chlorotrifluoro rine-containing perhalomethanes. and 2% dichlorofluoromethane. The fluorine-containing perhalomethanes, i. e., carbon The reaction between phosgene and the inorganic bi tetrafluoride and the chlorofluoromethanes, and especial nary fluoride to give fluorine-containing perhalomethanes ly , are extremely valuable com should be carried out at a temperature of at least 400 C. pounds. They find extensive use as liquids as 25 and preferably at least 450° C. At lower temperatures dielectric fluids and as ingredients of insecticidal com the reaction, if it proceeds at all, does not produce per positions, e.g., as propellants in aerosols. but solely carbonyl chlorofluoride and/or This invention has as an object a new process for pre carbonyl fluoride. The reaction temperature can be paring fluorine-containing perhalomethanes. Other ob much higher, e.g., up to 1000 C., but there is normally jects will appear hereinafter. 30 no advantage in using temperatures above about 700 C. These objects are accomplished by the present inven The preferred temperature range is from about 500 to tion of the process which comprises reacting phosgene at about 600 C. a temperature of at least 400° C. with a binary inorganic The conversions to perhalomethanes are improved, fluoride of an element having an atomic number from 11 especially in the lower temperature range (400-500 C.) to 83, inclusive, and isolating the fluorine-containing per 35 by the presence of a small amount of a halide (particular halomethanes formed. ly fluoride or chloride) of a metal in a valence state of 3 The phosgene can be used preformed or it can be to 5. Examples of such promoters are aluminum tri formed in situ from and chlorine which, fluoride, tin tetrachloride, ferric fluoride and antimony as is well known, combine readily at elevated tempera pentachloride. These materials are used in molar ture to give phosgene. When this is done, the two phos 40 amounts between 1 and 5%, based on the binary fluoride gene-forming components, i. e., carbon monoxide and employed. chlorine, can be used in equimolar quantities, or one or The reaction can be carried out at atmospheric pres the other can be used in excess. sure, for example by passing phosgene through a hot tube The inorganic binary fluoride which serves as the source containing the inorganic fluoride and recycling the efflu of fluorine can be the fluoride of any of those elements 45 ent , with or without separation of the reaction prod in groups I to VIII, inclusive, of the periodic table, which ducts. This procedure is operable but it entails practical have atomic numbers from 11 to 83, inclusive. Refer difficulties in that, when the inorganic fluoride is solid ence to any accepted periodic table, e.g., that given on at the reaction temperature, intimate contact between it page 27 of F. Ephraim's "Inorganic Chemistry,” fifth and the gaseous reactant is difficult to achieve. If it is English edition (1949), will show what these elements 50 liquid and/or volatile, it is at least partly entrained by are. the gas stream and must be recovered and recycled. The respective proportions of phosgene (or its com Thus, conversions are low when operating at atmospheric ponents) and inorganic fluoride are not critical. How pressure. It is therefore preferred to carry out the re ever, it is desirable to use the two reactants in such ratio action in a pressure vessel. Also, the use of pressure that there is present in the reaction mixture at least one 55 favors the presence of phosgene in the equilibrium reac fourth, preferably at least one-half, gram atom of fluorine tion between it and its components, carbon monoxide per gram atom of chlorine. Normally, the reactants are and chlorine. The reaction is normally conducted under used in approximately the ratio of one atom of fluorine the autogenous pressure developed by the reactants and per atom of chlorine. reaction products at the operating temperature but if de The reaction produces a mixture of products. The 60 sired additional pressure furnished by a non-interfering three possible chlorofluoromethanes are formed, prin gas, such as carbon monoxide or , can be applied, cipally and dichlorofluorometh e.g., an additional pressure of 100-1000 atmospheres or ane, which may be formed according to the following even higher. equation, using calcium fluoride as the illustrative re When operating under pressure, appreciable conver actant: 65 sions are obtained at reaction times as low as thirty minutes at the reaction temperature. Normally, the re Carbon dioxide is always found in the reaction products. action is allowed to proceed for at least one hour, and is normally formed in small preferably for three to eight hours. Longer reaction amounts, and traces of are some 70 times can be used, e. g., up to twelve hours, but they times present. Two other products, carbonyl fluoride and offer no special advantages since the conversions are not carbonyl chlorofluoride are also formed. These may be materially increased. It has been found that the catalysts 2,757,214 3 4 or promoters already mentioned improve the conversions a corrosion-resistant bomb. The gaseous reaction prod obtainable in short reaction times. uct, which weighed 53.3 g. after removal of any carbon A convenient procedure for working up the crude re monoxide present, was scrubbed with aqueous 40% potas action product consists in transferring the gaseous re sium hydroxide. The residual gas weighed 12.2 g. (47% action mixture to an evacuated cylinder, leaving in the conversion based on the phosgene, with chlorotrifluoro reaction vessel the non-volatile materials (unreacted in methane considered to be the entire product) and had organic fluoride and inorganic chlorides). The cylinder the following composition in moles percent: carbon is then externally cooled to a low temperature, for ex tetrafluoride, 1%; chlorotrifluoromethane, 60%; dichloro ample by means of liquid nitrogen, and pumped off to , 35%; , 10%. a low pressure, e. g., 0.1-1 mm. of mercury. This re O Iodometric titration of the scrubbing solution showed moves from the reaction mixture any air present in it, and that 76% of the initial amount of chlorine had been it also removes the residual carbon monoxide, whose recovered unchanged. presence results either from its addition as a reactant or Example III additional pressure gas or from its formation by partial dissociation of the phosgene used. After removal of the 5 The process of this example is similar to that of Ex carbon monoxide, the cylinder is closed and allowed to ample I except that an excess of calcium fluoride was warm to room temperature or to a temperature sufficient used. to permit vaporization of the volatile mixture, which A mixture of 78.0 g. (1.0 mole) of commercial cal is then fractionated in a suitable low temperature still cium fluoride and 49.5 g. (0.5 mole) of phosgene was to separate the various constituents. If the perhalo 20 heated at 500 C. under autogenous pressure for 6 hours. methanes are the only components it is desired to isolate, The gaseous product, after removal of any carbon mo it is convenient to remove all the acidic (carbon noxide present and scrubbing with aqueous 40% potas dioxide, chlorine, unchanged phosgene, carbonyl chloro sium hydroxide, weighed 10.6 g. (41% conversion based fluoride and carbonyl fluoride) prior to fractional distill on phosgene with chlorotrifluoromethane considered to lation. This can be done by bringing the crude gaseous 25 be the only product). This gas contained, on a molar reaction product in contact with an aqueous alkaline basis, 1-2% carbon tetrafluoride, 65% chlorotrifluoro solution, e. g., aqueous potassium or sodium hydroxide, methane, 30% dichlorodifluoromethane, and 5-10% tri used in sufficient amount to absorb all the products re chlorofluoromethane. active therewith. Absorption of the acidic gases can It is possible to increase the relative proportion of be carried out in the cylinder used to receive the crude 30 dichlorodifluoromethane in the reaction product by in gaseous reaction product, or the latter can be passed corporating in the reaction mixture a small amount, e.g., directly through an absorbing apparatus containing the 5-20 moles percent based on the inorganic fluoride, of alkaline solution and the effluent gas can be fractionated an alkali or alkaline earth metal . However, with or without prior removal of the carbon monoxide. the total conversions to perhalomethanes appear to be The following examples in which parts are by weight 35 lower when this is done. Example IV, below, which is unless otherwise specified are illustrative of the invention. otherwise comparable to Example I, illustrates this varia tion. Example I Example IV A mixture of 39 g. (0.5 mole) of commercial calcium A mixture of 39.0 g. (0.5 mole) of commercial cal fluoride and 49.5 g. (0.5 mole) of phosgene was heated 40 cium fluoride, 6.9 g, (0.05 mole) of anhydrous potassium in a steel bomb lined with a corrosion-resistant nickel carbonate and 49.5 g. (0.5 mole) of phosgene was heated iron-molybdenum alloy for 6 hours at 500 C. under at 500 C. for 6 hours under autogenous pressure. After the autogenous pressure developed by the reactants and scrubbing the gaseous reaction product with 40% aqueous reaction products. The gaseous reaction product, which potassium hydroxide, there was left 2.3 g of a product weighed 30.3 g. after removal of the carbon monoxide, having the following molar composition: carbon tetra was scrubbed with aqueous potassium hydroxide to re fluoride, 1%; chlorotrifluoromethane, 15%; dichlorodi move the acidic or hydrolyzable bases. The remaining , 65%; trichlorofluoromethane, 15-20%; alkali-insoluble gas weighed 10.9 g, Infrared analysis carbon tetrachloride, trace. The conversion was 8%, showed that it contained, on a molar basis, 1% carbon based on dichlorodifluoromethane as the sole product. tetrafluoride, 65% chlorotrifluoromethane, 30% dichlo Commercial calcium fluoride contains, as shown by rodifluoromethane, about 5% trichlorofluoromethane, emission spectroscopy, from 0.05 to 0.5% of aluminum. and a trace of carbon tetrachloride. The principal com This impurity can be removed, for example by heating ponents of this mixture are separated by fractional distill the calcium fluoride with potassium carbonate or by lation. However, the mixture is of itself useful as an fusing it with , and extracting the mass aerosol propellant. The conversion, calculated on the with distilled until it is free from carbonate or basis of chlorotrifluoromethane as the sole product and chloride . The resulting calcium fluoride contains using the equation then only traces of aluminum and other elements such as and iron. It is then found to be less reactive with phosgene than the non-purified material. For ex was 42%. 60 ample, repeating Example I with a sample of calcium A repetition of this example, except that the reaction fluoride purified by fusion with calcium chloride and time was 12 hours, gave about the same conversion to extraction with water gave a 10% conversion to chloro a product having substantially the same composition. fluoromethanes. However, addition of a polyvalent (at When the reaction time was only 3 hours, other condi least trivalent) metal halide as a promoter markedly tions being the same, there was obtained a 21% conver increases the conversion, as shown in Example V, below. sion to alkali-insoluble gas, containing on a molar basis 45% each of chlorotrifluoromethane and traces of car Example V bon tetrafluoride and carbon tetrachloride. The calcium fluoride used in this example was first heated at 500 C. for one-half hour with anhydrous po Example II 70 tassium carbonate, extracted with distilled water until The process of this example is similar to that of Ex free of carbonate, and dried at 400 C. A mixture of ample I except that an excess of chlorine was used. 39.0 g. (0.5 mole) of this calcium fluoride, 49.5 g. (0.5 A mixture of 39 g (0.5 mole) of commercial calcium mole) of phosgene and 1.13 g (0.01 mole) of ferric fluoride, 49.5 g. (0.5 mole) of phosgene and 18 g. (0.25 fluoride was heated at 500 C. for 3 hours. After scrub mole) of chlorine was heated at 500 C. for 6 hours in 75 bing the gaseous reaction product with aqueous alkali 2,757,214 5 6 there was left 9.9 g, of inert gas having the following molar bomb which was heated to 450° C. and pressured with composition: carbon tetrafluoride, less than 5%; chloro carbon monoxide to 800 atmospheres pressure. The bomb trifluoromethane, 70%; dichlorodifluoromethane, 25%; was maintained at 450° C. for 6 hours. After removing trichlorofluoromethane, 5%. The conversion was 38% the excess carbon monoxide by evaporation at reduced based on trifluorochloromethane as the sole product. pressure and liquid nitrogen temperature, the remaining Example VI gaseous reaction product (15.5 g.) was found by infrared analysis to contain, on a molar basis, 2% carbonyl fluo A mixture of 39.0 g. (0.5 mole) of commercial cal ride, 13% carbonyl chlorofluoride, 40% phosgene, 20% cium fluoride, 49.5 g. (0.5 mole) of phosgene and 0.84 carbon dioxide, 0.5% chlorotrifluoromethane, 0.5% di g. (0.01 mole) of aluminum fluoride was heated at 400 0 , 1% chloride, and 5% C. for 6 hours under autogenous pressure. The gaseous . The last component is presumably product, which weighed 35.0 g., was scrubbed with 40% formed through hydrolysis of the carbonyl by aqueous potassium hydroxide. There was obtained 1.8 adventitious moisture and reaction of the resulting hy g. of inert gas containing on a molar basis, less than 1% drogen fluoride with the glass of the analytical cell. carbon tetrafluoride, 25% chlorotrifluoromethane, 60% 15 dichlorodifluoromethane and 15% trichlorofluorometh Example XI ane. The conversion was 6%, based on dichlorodifluoro A pressure vessel containing 21.0 g (0.5 mole) of so methane as the sole product. dium fluoride and 49.5 g. (0.5 mole) of phosgene was heated at 500 C. for 6 hours. After removing any car Example VII 20 bon monoxide present and scrubbing the crude gaseous The procedure of Example VI was repeated, except that reaction product (26.5 g.) with aqueous potassium hy the reaction mixture was heated at 500 C. for one hour. droxide, the residual gas (8.1 g) was found to contain, on The alkali-insoluble gas (3.8 g.) contained, on a molar a molar basis, 5% carbon tetrafluoride, 85% chlorotri basis, less than 1% carbon tetrafluoride, 35% chlorotri fluoromethane, 5% dichlorodifluoromethane, and less fluoromethane, 55% dichlorodifluoromethane and 10% 25 than 1% trichlorofluoromethane. The conversion based trichlorofluoromethane. The conversion was 13% based on the and with chlorotrifluoromethane on dichlorodifluoromethane as the sole product. as the sole product was 46.5%. When the above experiment was repeated, except that Example VIII 0.84 g (0.01 mole) of aluminum fluoride was added to A mixture of 39.0 g (0.5 mole) of commercial calcium 30 the reaction mixture, the conversion on the same basis fluoride, 35.5 g. (0.5 mole) of chlorine and 14 g. (0.5 was raised to 65.5%. The alkali-insoluble product (11.4 mole) of carbon monoxide was treated as in Example I g.) contained, in moles percent, 5% carbon tetrafluoride, and the crude gaseous reaction product (25.8 g. after 90% chlorotrifluoromethane, 5% dichlorodifluorometh removal of any remaining carbon monoxide by pumping ane, and less than 1% trichlorofluoromethane. off at liquid nitrogen temperature) was scrubbed with 35 aqueous potassium hydroxide. The remaining gas (8.5 Example XII g.) was shown by infrared analysis to contain, on a molar A pressure vessel containing 44.0 g. (0.33 mole) of basis, 1% carbon tetrafluoride, 55% chlorotrifluorometh arsenic EEI fluoride and 49.5 g. (0.5 mole) of phosgene ane, 40% dichlorodifluoromethane, and 5-10% trichloro was heated at 500 C. for 6 hours. The gaseous reac fluoromethane. The conversion was 33% based on chlo 40 tion product, after removal of any carbon monoxide rotrifluoromethane as the sole product. present and scrubbing with aqueous 40% potassium hy In the two following examples the gaseous reaction droxide, weighed 5.8 g. This represents a 22% conver product was analyzed without prior treatment with alkali sion, with chlorotrifluoromethane considered to be the in order to determine the nature of the alkali-reactive entire product, and on the basis of the equation components. 45 Example IX 2COCl2--Asfa-> AsCl3--CO2--CF3Cl A mixture of 49.5 g. (0.5 mole) of phosgene, 45 g. This produce contained, on a molar basis, 85% chloro (0.58 mole) of calcium fluoride, and 5 g. of antimony pen trifluoromethane, 10% dichlorodifluoromethane, and tachloride, used as reaction catalyst, was heated in a traces of carbon tetrafluoride and carbon tetrachloride. steel bomb at 500° C. for 3 hours under autogenous 50 Example XIII pressure. The gaseous reaction product (38 g. total A mixture of 38.6 g. (0.33 mole) of cobalt III fluoride weight) was found by infrared analysis to contain, on a and 49.5 g. (0.5 mole) of phosgene was heated at 500 C. molar basis, 3% carbonyl fluoride, a small amount of for 6 hours under autogenous pressure. The crude carbonyl chlorofluoride, 10% phosgene, 10% carbon di 55 gaseous product (45.0 g) contained 3.8 g. of alkali oxide, 0.5% carbon tetrafluoride, 10% chlorotrifluoro insoluble gas having the following molar compositions: methane, 3% dichlorodifluoromethane, and 3% hydro carbon tetrafluoride, 10%; chlorotrifluoromethane, 75%; gen chloride. The remainder was probably in part chlor difluorodichloromethane, 15%; trichlorofluoromethane, ine (which has no infrared absorption band) and in part trace. The conversion based on the phosgene and with adventitious air in the infrared cell. The various com 60 chlorotrifluoromethane considered as the entire product ponents are separated by fractional distillation, with the was 15%. exception of carbonyl fluoride and hydrogen chloride The process of this invention is also applicable to the which have practically the same boiling points. These preparation of bromofluoromethanes by reaction of car may be separated by bringing the mixture thereof in con bonyl bromide, or of carbon monoxide and , with tact with at least two moles of sodium fluoride, per mole 65 the binary inorganic fluorides defined above. In this of hydrogen chloride in the mixture, and maintaining the case, however, the conversions are very poor with most mixture in contact with the sodium fluoride, preferably inorganic fluorides, probably because carbonyl bromide at room temperature, until the hydrogen chloride has been is strongly dissociated at the operating temperautres. Ac absorbed from the mixture. This separation of carbonyl ceptable conversions are, however, observed with the fluoride from hydrogen chloride is the subject of appli 70 more reactive binary inorganic fluorides. Thus, when a cation Serial No. 489,294 concurrently filed by Charles mixture of mercury II fluoride (59.7 g., 0.25 mole), W. Tullock. bromine (80 g., 0.5 mole), carbon monoxide (14 g., 0.5 Example X mole) and aluminum fluoride (0.84 g., 0.01 mole) is A mixture of 49.5 g. (0.5 mole) of calcium fluoride heated at 500 C. for 3 hours under autogenous pressure, and 35.5 g. (0.5 mole) of chlorine was placed in a steel 75 there is obtained 1.4 g. of alkali-insoluble gas having 2,757,214 7 8 the following molar composition: carbon tetrafluoride, ing phosgene in contact at a temperature of at least 55%; bromotrifluoromethane, 40%; , 400° C. with a binary inorganic fluoride of an element less than 1%; , trace; trifluoromethane, having an atomic number of 11 to 83, inclusive, and 1%. The conversion was 8% based on the mercury II isolating the said halogenated methanes. fluoride and assuming the product to be a 1:1 mixture of 2. The process for preparing completely halogenated carbon tetrafluoride and bromotrifluoromethane. methanes in which at least one halogen atom is fluorine, While this invention has been illustrated through the any other halogen being chlorine, which comprises bring use of certain specific inorganic fluorides, it comprises ing phosgene in contact at a temperature of at least 400 broadly the process of preparing fluorine-containing per C. with a binary metallic fluoride of a metal having an halomethanes by reacting phosgene, or its precursor com 10 atomic number of 11 to 83, inclusive, and isolating the ponents, i. e., carbon monoxide and chlorine, with a Said halogenated methanes. binary fluoride of an element of atomic number from 11 3. The process for preparing completely halogenated to 83, inclusive. The fluorides of these elements in any methanes in which at least one halogen atom is fluorine, valence state can be used. Thus, in addition to the any other halogen being chlorine, which comprises bring fluorides of the examples, there can be used potassium 5 ing phosgene in contact at a temperature of at least 400 fluoride, copper II fluoride, , zinc C. with a binary fluoride of an alkali forming metal of fluoride, , mercury I fluoride, aluminum atomic number of 11 to 83, inclusive, and isolating the II fluoride, titanium IV fluoride, tin II fluoride, lead II said halogenated methanes. fluoride, phosphorus II fluoride, antimony III fluoride, 4. The process for preparing completely halogenated antimony V fluoride, bismuth II fluoride, chromium III 20 methanes in which at least one halogen atom is fluorine, fluoride, tungsten VI fluoride, manganese III fluoride, any other halogen being chlorine, which comprises bring chlorine III fluoride, iron II fluoride, iron II fluoride, ing phosgene in contact at a temperature of at least 400 cobalt II fluoride, nickel I fluoride, etc. Metal fluorides C. with calcium fluoride and isolating the said halogenated are in general more desirable. The preferred fluorides methanes. because they give the highest conversions to chloro 25 5. The process of claims 1-3 wherein the binary fluoromethanes, are those of the elements in groups fluoride has added thereto a small amount of a binary and II of the periodic table, and particularly the binary halide of a metal having, in the halide, a valence of fluorides of the alkali forming metals, i. e., the alkali 3 to 5. metals and alkaline earth metals. The most useful fluo 6. The process for preparing completely halogenated rides are calcium fluoride and sodium fluoride. 30 methanes in which at least one halogen atom is fluorine, The foregoing detailed description has been given for any other halogen being chlorine, which comprises bring clearness of understanding only and no unnecessary ing phosgene in contact at a temperature of at least 400 limitations are to be understood therefrom. The inven C. with calcium fluoride containing a small amount of a tion is not limited to the exact details shown and de binary halide of a metal having, in the halide, a valence scribed, for obvious modifications will occur to those 35 of 3 to 5 and isolating the said halogenated methanes. skilled in the art, 7. The process for preparing completely halogenated The embodiments of the invention in which an ex methanes in which at least one halogen atom is fluorine, clusive property or privilege is claimed are defined as any other halogen being chlorine, which comprises bring follows: ing phosgene in contact at a temperature of at least 400 1. The process for preparing completely halogenated 40 C. with sodium fluoride and isolating the said halogenated methanes in which at least one halogen atom is fluorine, methanes. any other halogen being chlorine, which comprises bring No references cited.