US2916526A - Recovery of saturated perhalogenated fluorine-containing hydrocarbons - Google Patents

Description

at present are relatively expensive.

United States Patent RECOVERY OF SATURATED PERHALOGENA'IED FLUORINE-CONTAINlbIG HYDROCARBONS Charles F. Baranauckas, Niagara Falls, N.Y., and Donald H. Campbell, Niagara-on-the-Lake, Ontario, Canada, assignors to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Application May 6, 1957 Serial No. 657,022

8 Claims. (Cl. 260-653) This invention relates to a process for removing hydrocarbons and partially oxidative derivatives of hydrocarbons from saturated chlorofluorocarbons and fluorocarbons of the type which are resistant to strongly oxidative Conditions and recovering the chlorofiuorocarbons and fluorocarbons in condition for reuse.

Saturated perhalogenated hydrocarbons containing only carbon, chlorine and fluorine atoms or only carbon and fluorine atoms which are resistant to such strong oxidizing agents as: fuming nitric acid, 90% hydrogen peroxide, perchloric acid, sodium chlorate, sodium perchlorate, oxygen under pressure, permanganates, chromates etc. have found many lubrication applications and other uses in industry. Under some use conditions the saturated perhalogenated fluorine-containing hydrocarbons become contaminated with various hydrocarbons, and partially oxidized derivatives thereof, such as are present in fuels and oils before and after the fuels and oils have been burned, especially in applications associated with power plants and platforms for missiles and rockets. Once the saturated perhalogenated fluorine-containing hydrocarbons have been contaminated with hydrocarbons and partially oxidized derivatives thereof, their continued use in a setting where strong oxidizing agents'of'the type mentioned above are present is hazardous since explosions may result. Since said perhalogenated fluorine-containing hydrocarbons are relatively expensive, a method of reclaiming the perhalogenated fluorine-containing hydrocarbons by removing the hydrocarbon (and partially oxidized derivatives thereof) contaminants, is economically desirable.

As a more specific example, a series of chlorofluorohydrocarbons which are relatively low molecular weight polymers (having a molecular weight in the 300-2000 range) of chlorotrifluoroethylene such as are currently marketed by the Hooker Chemical Corporation under the trademark Fluorolube, are used in guided missile pumps, motors and bearings exposed to strongly oxidative conditions. The various jet-type fuels used in the missiles, such as kerosene and straight and branched chain hydrocarbons on the order of those present in kerosene and their partially oxidized derivatives, often seep in through the seals and contaminate the chlorotrifluoroethylene polymer lubricant. Since liquid oxygen and hydrogen peroxide capable of detonating or exploding the kerosene type hydrocarbons are present in the general area of the lubricants, such contamination is a real hazard, and the usual procedure is to drain the contaminated lubricants from the use areas and replace them with fresh uncontaminated lubricants, which Until the present invention the contaminated lubricants were usually discarded, as prior recovery procedures were so complex as to be uneconomical.

We have found a relatively simple way to reclaim the saturated perhalogenated fluorine-containing hydrocarbons by removing the kerosene type hydrocarbon contaminants using inexpensive, readily available reagents, and it is this method which constitutes the present invention. The invention is not limited to just chlorotrifluoroethylene polymers, but is applicable to any saturated perhalogenated fluorine-containing hydrocarbons which are resistant to strongly oxidative conditions, and which are liquids at temperatures of about C.

Among such operable saturated perhalogenated fluorine-containing hydrocarbons included within the present invention are, for example, polymers and copolymers made from such monomeric units as (CF CF (CF CFCI), (OF -C01 (CF -CF=CF perfluorobutene-l, perfluorocyclobutene, perfiuoropentene, which have a molecular weight in the 3002000 range and in which the terminal carbon atoms of the polymers and copolymers have attached thereon at least one fluorine atom. Perfluoronaphthalene, perfluoro-l-methylnaphthalene, perfluoro 2 methylnaphthalene, perfluoroacenaphthene perfluoroindene, perfluorofluorene, perfluorodimethylnaphthalenes, perfluorophenanthrene, perfluoroanthrancene, perfluoro-fluoranthene, perfluoro-2,2,3- trimethylpentane, perfluorotrimethylbutane, perfluorodimethylcyclohexane, perfluoro 1,3,5 trimethylcyclohexane, perfluoro-n-hexadecane, chloropentadecafluoroheptane, etc.

The contaminants which may be removed include all the various branched and straight chain hydrocarbons and partially oxidized derivatives thereof such as acids, aldehydes, ketones etc. These contaminants will be referred to hereinafter as hydrocarbon contaminants, for convenience.

The hydrocarbon contaminants may be present in as much as about 25% by weight of the saturated perhalogenated fluorine-containing hydrocarbons. The kerosene or other hydrocarbon fuels which are used in missiles often contain small amounts of conventional fuel additives and the present process usually serves to remove these. Small amounts of silicones which may be present with the hydrocarbon contaminants are also removed. For certain uses reclamation becomes desirzlle' when hydrocarbon contamination reaches about Generally the process of the present invention includes reacting the hydrocarbon-contaminated saturated perhalogenated fluorine-containing hydrocarbon with a strong sulfonating agent, thereby converting the unwanted hydrocarbons and partially oxidized derivatives thereof, to various water soluble products which are easily and almost completely removed from the waterinsoluble saturated perhalogenated fluorine-containing hydrocarbons leaving a saturated perhalogenated fluo- IIDC-COIltaiHiIIg hydrocarbon of the same viscosity and composition as the virgin material. Among the strong sulfonating agents which may be used are, for example, chlorosulfonic acid, sulfur trioxide, fluoro-sulfonic acid and a sulfur dioxide-chlorine gaseous mixture. Where chlorosulfonic acid is used as the sulfonating agent, the reaction products are hydrogen chloride, and the water soluble sulfonates of the hydrocarbon and various other water soluble degradation products.

The relative amount of strong sulfonating agent used is directly proportionate to the degree of contamination of the saturated perhalogenated fluorine-containing hydrocarbon. Since the sulfonating agent is relatively inexpensive, it is deemed preferable to use a substantial excess over the stoichiometrically required amount. With chlorosulfonic acid, where the saturated perhalogenated fluorine containing hydrocarbon is contaminated with 4% by weight of kerosene, approximately equal weights of the hydrocarbon contaminated saturated perhalogenated fluorine-containing hydrocarbon and chlorosulfonic acid are preferred.

To ensure complete reaction of the sulfonalting agent with the hydrocarbon contaminant a temperature less than that at which the saturated perhalogenated fluorinecontaining hydrocarbon is attacked by the sulfonating agent is used, so the upper temperature limits will vary somewhat for the various saturated perhalogenated fluorine-containing hydrocarbon which are to be reclaimed. When a strong sulfonating agent is used which is a liquid at room temperature, we prefer to conduct the reaction at temperatures below the boiling point of said sulfonating agent to avoid loss to the atmosphere of such sulfonating agent without necessity for an involved recovery system, although higher temperatures are operable. For the relatively low molecular weight chlorotrifluorethylene polymer, temperatures below about 100 C. are preferred when chlorosulfonic acid is the sulfonating agent. Where sulfur trioxide is used, reaction temperatures are preferably maintained slightly below the 45 C. boiling point of sulfur trioxide.

Where a sulfur dioxide-chlorine gas mixture in the presence of ultra-violet light is used as the sulfonating agent, no external heating is required.

The reaction time depends on the relative amount of hydrocarbon contaminant present and the amount of strong sulfonating agent used, the efliciency of the mixing, and the highest feasible temperature, and is on the order of 0.5-14 hours.

When the hydrocarbon contaminated saturated perhalogenated fluorine-containing hydrocarbon has been completely reacted with the strong sulfonating agent, the mixture is allowed to cool and any unreacted excess of sulfonating agent is destroyed, as by pouring the mixture slowly onto ice, or the unreacted sulfonating agent, which forms a separate layer, can be removed as with a separatory funnel. The water reaction mixture is then washed well as by flowing water up through the saturated perhalogenated fluorine-containing hydrocarbon layer. The saturated perhalogenated fluorine-containing layer is separated from the water layer and purified further to remove any traces of acid materials which may be left. The preferred way of purifying is by heating the washed saturated perhalogenated fluorine-containing hydrocarbon layer at about 110 C. for about an hour with a mixture of sodium carbonate (2% by weight of the perhalogenated fluorine-containing hydrocarbon layer) and clay (1% by weight of the perhalogenated fluorine-containing hydrocarbon layer) and then filtered to obtain the reclaimed perhalogenated fluorine-containing hydrocarbon relatively free from all contaminants. When the perhalogenated fluorine-containing hydrocarbon to be purified is dry, a small amount of water is added with the sodium carbonate and clay.

The following examples are offered for the better understanding of the invention. It will be apparent to those skilled in the art that the procedures described in the examples may be modified and equivalents substituted for the various reactants used, as suggested in the foregoing part of the specification, without departing from the scope of this invention, hence these examples are not to be construed as limiting:

Example 1 Into a three necked flask fitted with an additional funnel, electric stirrer, Y tube vented to hood and thermometer, and equipped with an electric heating mantle, there were introduced 542 grams of chlorotrifluoroethylone polymer (as a clear, colorless liquid having a viscosity at 100 F. of 16.72 centistokes), 25 grams of kerosene, and 593 grams of technical grade chlorosulfonic acid. The reaction mixture was heated at 135- 150 C. with continuous stirring for 13.5 hours. The reaction mixture was then allowed to cool and added slowly to ice in a beaker and was washed well with a continuous stream of water through a sparger which permitted water to flow up through the stirred chlorotrifluoroethylene layer. The washed chlorotrifiuoroethylene polymer which had been separated off, was then heated in a 3 necked flask equipped with an electric stirrer and a thermometer, with 2% by weight of sodium carbonate and 1% by weight of clay at C. for one hour and then filtered, thus removing all traces of acidic material which may have been left. There were thus obtained 520 grams of chlorotrifluoroethylene polymer as a clear, colorless liquid having a viscosity of 16.4 centistokes at 100 F. Infrared analysis of the product showed that the kerosene content was less than 5 parts per million.

Example 2 Following the procedure of Example 1, but using 542 grams of chlorotrifluoroethylene polymer, 25 grams of kerosene, and 567 grams of chlorosulfonic acid, and reacting the above at 100 C.i5 C., for a period of 4.5 hours, there were obtained 495 grams of chlorotrifluoroethylene polymer having a kerosene content of less than 5 parts per million.

Example 3 The procedure of Example 1 was followed, but using 163 grams of chlorotrifluoroethylene polymer contaminated with 2% by weight of jet fuel (JP-4) which was mainly kerosene, and 176 grams of chlorosulfonic acid and a temperature of 100 C. After 30 minutes a sample of the reaction product was withdrawn and purified by the soda ash-clay method, and infra-red analysis showed that the reclaimed chlorotrifluoroethylene polymer contained only 22 parts er million of kerosene.

The reaction was continued and after another 3.5 hours, the reaction product was purified and the reclaimed chlorotrifiuoroethylene polymer recovered grams) contained less than 5 parts per million of kerosene.

Example4 Following the procedure of Example 1, but reacting 504 grams of chlorotrifluoroethylene polymer, 23 grams of kerosene, and 713 grams of fluorosulfonic acid for 1 hour at a temperature of 100 C., there were obtained 440 grams of chlorotrifluoroethylene polymer containing 110 parts per million of kerosene as a contaminant.

Example 5 Example 6 Into a liter 3 necked flask, equipped With electric stirrer, thermometer and vent, with 2 ultra-violet lights above the flask, were placed 632 grams of chlorotrifluoroethylene polymer and 24 grams of kerosene. A gaseous mixture of approximately equal parts of S0 and Cl gases was fed through calibrated flowmeter tubes, bubblers and traps into the bottom of the flask until 473 grams of S0 and 438 grams of C1 were added over 4 hours, While the reaction flask was kept at room temperature. The reaction product was cooled and a tan gummy layer settled out on the top of the polymer layer. This layer was filtered out and the polymer-containing filtrate was heated at IOU-110 C. for one hour with 2% by weight of polymer of sodium carbonate, 1% by weight of the polymer of clay (Attapulgus) and 0.25% by weight of the polymer of water. There were thus obtained 546.6

H 5 grams of chlorotrifluoroethylene polymer having a ke r sene content of 82 parts per million. The loss of startmg material to be reclaimed was due mainly to losses on the gummy layer, on the soda ash filter cake and handling loss.

Example 7 Following the procedure of Example 1, but using 310 grams of chloroperfluoroheptane, 12 grams of kerosene and 315 grams of chlorosulfonic acid, and reacting the above at C. for a period of 5 hours, there were obtained 283 grams of chloroperfluoroheptane. Infrared analysis of this product showed that the kerosene content was less than 5 parts per million.

Example 8 Following the procedure of Example 1, but using 185 grams of perfluoronaphthalene, 9 grams of kerosene and 170 grams of chlorosulfonic acid and reacting the above at 100i5 C. for a period of 6 hours, there were obtained pure 176 grams of perfluoronaphthalene having a kerosene content of less than 5 parts permillion as determined by infrared analysis.

Example 9 Following the procedure of Example 1 but using 475 grams of perfluorodimethylcyclohexane, 25 grams of kerosene, and 500 grams of chlorosulfonic acid and reacting the above at 100:5" C. for a period of 5 /2 hours, there were obtained 450 grams of pure perfluoroethylcyclohexane having a kerosene content of less than 5 parts per million as determined by infrared analysis.

Example The procedure of Example 1 was followed, but using 475 grams of chlorotrifluoroethylene polymer (as a clear colorless liquid having a viscosity at 100 F. of 100:5 centistokes), 95 grams of jet fuel (JP-4) and 825 grams of technical grade chlorosulfonic acid. The reaction mixture was heated for seven hours at 140 C., after the chlorosulfonic acid had all been added. After working up the recovered polymer (443 grams) infrared analysis showed a hydrogen content of only 12 parts per million.

Example 11 Following the procedure of Example 1 but using 123 grams of a liquid copolymer of chlorotrifluoroethylene and symmetrical dichlorodifluoroethylene having a boiling range of 70200 C. at a pressure of 0.2 mm., 127 grams of chlorosulfonic acid, and 5 grams of kerosene, and reacting the above at l00i5 C. for a period of 6 hours, there were recovered 101 grams of a copolymer of chlorotrifluoroethylene and symmetrical dichlorodifluoroethylene which contained less than 10 parts per million of kerosene by infrared anlysis.

Example 12 Example 13 Following the procedure of Example 1, but using 120 grams of a liquid polymer of tetrafluoroethylene having a boiling range of 100-200 C. at a pressure of 0.5 mm., 125 grams of fluorosulfonic acid, and 5 grams of kerosene, and reacting the above at 70i5 C. for a period of 10 hours, there were obtained 113 grams of tetrafluoroethylene polymer which contained less than 100 parts per million of kerosene by infrared analysis.

Example 14 Following the procedure of Example 1, but using 76 grams of a liquid copolymer of chlorotrifluoroethylene and tetrafluoroethylene having a boiling range of 70170 C. at a pressure of 0.5 mm., 80 grams of chlorosulfonic acid, and 5 grams of kerosene, and reacting the above at :5" C. for a period of 4.5 hours, there were obtained 63 grams of the copolymer of chlorotrifluoroethylene and tetrafluoroethylene which contained less than 25 parts per million of kerosene by infrared analysis.

We claim:

1. A process for reclaiming water-insoluble saturated perhalogenated fluorine-containing hydrocarbons which are liquid at temperatures of about 150 C., and are resistant to strongly oxidative conditions, from mixtures of said perhalogenated fluorine-containing hydrocarbons contaminated with up to 25% by weight of hydrocarbon contaminants which comprises: reacting said hydrocarbon contaminated perhalogenated fluorine-containing hydrocarbon with a strong sulfonating agent at a temperature below that at which said perhalogenated fluorine containing hydrocarbon is attacked by the sulfonating agent, until the hydrocarbon contaminants have been converted to water-soluble products, and recovering the uncontaminated water-insoluble saturated perhalogenated fluorine-containing hydrocarbons from the reaction mixture.

2. A process for reclaiming water-insoluble saturated perhalogenated fluorine-containing hydrocarbons which are liquid at temperatures of about 150 C., and are resistant to strongly oxidative conditions from mixtures of said perhalogenated fluorine-containing hydrocarbons "contaminated with up to about 25% by weight of hydrocarbon contaminants, which comprises the following steps: mixing said contaminated perhalogenated fluorinecontaining hydrocarbon with a strong sulfonating agent, said sulfonating agent being present in an amount in excess of that stoichiometrically required to sulfonate the hydrocarbon contaminants, reacting the contaminated perhalogenated fluorine-containing hydrocarbon sulfonating agent mixture at a temperature below that at which said perhalogenated fluorine-containing hydrocarbon is attacked by the sulfonating agent, until said contaminants have been converted to water-soluble products; washing the reaction products; and separating the water-insoluble perhalogenated fluorine-containing hydrocarbon layer which forms.

3. The process of claim 2, wherein the strong sulfonating agent is chlorosulfonic acid.

4. The process of claim 2, wherein the strong sulfonating agent is fluorosulfonic acid.

5. The process of claim 2, wherein the strong sulfonating agent is sulfur trioxide.

6. The process of claim 2, wherein the strong sulfonating agent used is a gaseous mixture of approximately equal amounts of sulfur dioxide and chlorine.

7. A process for reclaiming water-insoluble saturated perhalogenated fluorine-containing hydrocarbons which are liquid at temperatures of about 150 C., and are resistant to strongly oxidative conditions, from mixtures of said perhalogenated fluorine-containing hydrocarbons contaminated with up to 25% by weight of hydrocarbon contaminants which comprises: reacting said contaminated perhalogenated fluorine containing hydrocarbon with about 50-110% by weight of a strong sulfonating agent based on the starting hydrocarbon contaminated perhalogenated fluorine-containing hydrocarbon, at a temperature from room temperature to about C., for a period of 0.5-14hours; cooling said reaction mixture; adding said cooled reaction mixture slowly to ice; washing the resultant ice mixture with water; separating the water-insoluble perhalogenated fluorine-containing hydrocarbon layer which forms, and purifying said layer, thereby to obtain the perhalogenated fluorine-containing hydrocarbon substantially free from all contaminants.

8. A process for reclaiming chlorotrifluoroethylene polymers having a molecular Weight of 300-2000 from a mixture of said polymers contaminated by 115% of hydrocarbon contaminants of kerosene boiling point range which comprises; heating said contaminated polymer with an approximately equal Weight of chlorosulfonic acid for 313 hours at about 100 C, cooling, and adding the reaction mixture slowly to ice; Washing the ice mixture with Water, and separating off the water-insoluble polymer-containing layer which forms.

References Cited in the file of patent UNITED STATES PATENTS 2,036,469 Field Apr. 7, 2,037,229 Gunther et a1 Apr. 14, 2,197,800 Henke et a1 Apr. 23, 2,496,115 Burford et a1. Jan. 31, 2,691,052 Cines Oct. 5,

OTHER REFERENCES 374 (p. 368 relied upon).

Claims (1)

1. A PROCESS FOR RECLAIMING WATER-INSOLUBLE SATURATED PERHALOGENATED FLUORINE-CONTAINING HYDROCARBONS WHICH ARE LIQUID AT TEMPERATURE OF ABOUT 150* C., AND ARE RESISTANT TO STRONGLY OXIDATIVE CONDITIONS, FROM MIXTURES OF SAID PHERHALOGNENATED FLUORINE-CONTAINING HYDROCARBONS CONTAMINATED WITH UP TO 25% BY WEIGHT OF HYDROCARBONS CONTAMINATED PERHALOGENATED FLUORINE-CONTAINING HYDROCARBON WITH A STRONG SULFONATING AGENT AT A TEMPERATURE BELOW THAT AT WHICH SAID PERHALOGENATED FLUORINE CONBELOW THAT AT WHICH SAID PERHALOGENATED FLUORINE CONTAINING HYDROCARBON IS ATTACKED BY THE SULFONATING AGENT, UNTIL THE HYDROCARBON CONTAMINANTS HAVE BEEN CONVERTED TO WATER-SOLUBLE PRODUCTS, AND RECOVERING THE UNCONTAMINATED WATER-SOLUBLE SATURATED PERHALOGENATED FLUORINE-CONTAINING HYDROCARBON FROM THE REACTION MIXTURE.