US3873630A - Process for pyrolyzing tetrafluoroethylene to hexafluoropropylene - Google Patents

Process for pyrolyzing tetrafluoroethylene to hexafluoropropylene Download PDF

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US3873630A
US3873630A US261629A US26162972A US3873630A US 3873630 A US3873630 A US 3873630A US 261629 A US261629 A US 261629A US 26162972 A US26162972 A US 26162972A US 3873630 A US3873630 A US 3873630A
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tfe
mixture
pyrolysis
hfp
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Norman Eugene West
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EIDP Inc
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EI Du Pont de Nemours and Co
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Priority to CA172,485A priority patent/CA1015771A/en
Priority to JP6344673A priority patent/JPS5728696B2/ja
Priority to FR7321021A priority patent/FR2187743B1/fr
Priority to GB2771973A priority patent/GB1384036A/en
Priority to IT50667/73A priority patent/IT989657B/en
Priority to DE2329750A priority patent/DE2329750C2/en
Priority to NL7308149A priority patent/NL7308149A/xx
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C17/00Preparation of halogenated hydrocarbons
    • C07C17/26Preparation of halogenated hydrocarbons by reactions involving an increase in the number of carbon atoms in the skeleton

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  • the UNITED STATES PATENTS distillate mixture can be recycled to the pyrolysis fur- 2,394,58l 2/1946 Benning ct 211 260/6533 nace, 2,551,573 5/1951 Downing et al 260/6533 2,758,138 8/1956 Nelson 260/6533 6 Chums N0 Drawmgs PROCESS FOR PYROLYZING TETRAFLUOROETHYLENE TO HEXAFLUOROPROPYLENE This invention relates to pyrolysis of tetrafluor oethylene to hexafluoropropylene.
  • U.S. Pat. No. 2,551,573 to Downing et al. discloses the pyrolysis of CHCIF to tetrafluoroethylene and higher boiling fluorocarbon products.
  • U.S. Pat. No. 2,758,138 to Nelson discloses the pyrolysis of tetrafluoroethylene to hexafluoropropylene at various specific conditions involving low partial pressures, i.e., 25 to 200 mm. of Hg, of the tetrafluoroethylene feed.
  • a process for pyrolyzing tetrafluoroethylene to hexafluoropropylene at higher pressures, viz., 0.2 to 65 psia. is disclosed in U.S. Pat. No.
  • the present invention provides a pyrolysis process for making hexafluoropropylene which is economically advantageous over all the foregoing described processes.
  • the process involves pyrolyzing a feed of tetra tluoroethylenc (TFE) and a minor proportion of car bon dioxide in a reaction zone at a temperature of 700 to 900C, and a pressure of 0.75 to 2.0 atmospheres absolute, and a minimum partial pressure of TFE of 360 mm.
  • TFE tetra tluoroethylenc
  • the process has been operated economically at conversions of TFE up to about 80 percent.
  • the major pyrolysis product i.e., greater than 50 percent by weight of the pyrolysis products, is HFP. Yields of greater than 80 percent by weight and as high as 90 percent by weight of TFE to HFP, the desired product, can be obtained by this pro cess.
  • a major problem involved in pyrolyzing TFE is its tendency to disproportionate to carbon tetrafluoricle and carbon according to the reaction which represents both a yield loss of expensive chemical and causes plugging of the reaction apparatus. This disproportionation is an exothermic reaction so once it begins, it tends to be a runaway reaction.
  • the invention of the aforementioned Nelson patent attempted to avoid this problem by operating at very low pressures, i.e., less than 200 mm. of Hg absolute. This low pressure of operation was obtained by continuously evacuating the pyrolysis furnace and feeding the TFE to the furnace, which, by itself, determined the pressure in the furnace.
  • TFE could be pyrolyzed to HFP at higher, more conveniently obtainable pressures such as atmospheric pressure, but this required the presence of at least 5 percent of pyrolyzable fluorocarbon materials having a boiling point higher than HFP which were normally provided by recycling the higher boiling pyrolyzate, which had the disadvantage of repeated handling of highly toxic materials rather than leading to quick waste disposal thereof.
  • the present invention also operates at the more favored pressure condition of around atmospheric pressure but without requiring the presence of the highboiling fluorocarbon compounds and the attendant toxicity problem and yet avoiding the disproportionate problem.
  • the process of the present invention is most conveniently conducted preferably at atmospheric pressure by passing a mixture of the TFE and carbon dioxide through a heated tube, called a pyrolysis furnace, with the heated portion of the tube being the reaction or pyrolysis zone.
  • a pyrolysis furnace a heated tube
  • the presence of the carbon dioxide in the pyrolysis furnace during the pyrolysis of TFE in the present invention prevents the undesirable disproportionation ofthe TFE despite the partial pressure ofTFE being substantially higher than that disclosed by Nelson.
  • the proportions of TFE and carbon dioxide in the feed to the reaction Zone there is always a greater weight of TFE present than carbon dioxide, and thus the latter is present as a minor proportion (weight basis) of the feed.
  • the proportion ofTFE to carbon dioxide in the feed will be from 1:1 to 25:1 on a weight basis.
  • the feed mixture to the reaction zone advantageously contains at least 40 percent by weight (total feed basis) of carbon dioxide to render the mixture nonflammable in case of leakage to the atmosphere.
  • the partial pressure of TFE in the feed mixture is at least 450 mm. of Hg absolute.
  • gaseous hydrogen chloride or hydrogen fluoride is preferably injected into the pyrolysis mixture as described in U.S. Pat. No. 3,578,721 to Couture eta1., in order to prevent polymerization of unreacted TFE which would eventually cause plugging of the recovery system.
  • the next step in the process is to recover the unreacted TFE and carbon dioxide as a mixture from the rest of the pyrolysis mixture by techniques well known in the art, such as distillation.
  • the boiling point of the TFE is 76.8C. and the sublimation point of carbon dioxide is -78C. which enables these compounds to be separated from the HFP (b.p. 29C) and higher boiling fluorocarbon pyrolysis products in a single distillation operation and recovered as a mixture.
  • the distillation is conducted under pressure, such as 17.5 kg/cm (gauge), to raise the boiling point of the distillate to a convenient temperature of operation, which temperature is above the temperature at which solid CO could exist in the distillation system.
  • HCl is added to the pyrolyzate, as described above, it will distill with the TFE as an azeotrope therewith. 1f the additive is HF. it will a mixture to the lnconel tube via calibrated rotameters. Hydrogen chloride was injected into the exit zone of the pyrolysis tube where the temperature was about 500C. to inhibit polymerization of unreacted TFE in not dlstlll with the TFE but will remain with the HFP 5 the collection system.
  • the lnconel tube was heated to and other hlgh'bolllhg Py y productswhen the the desired reaction temperature with a carbon dioxide HCl is distilled with the TFE and carbon dioxide, the purge d h TFE was added to the feed stream to resultant gaseous mlxlhle can be Passed through a the tube to obtain a mixture having the desired TFE/- ventional water-scrubber to remove the HCl to prevent (IQ ti Th y ol sis was conducted at about atmolhe l'lcl from behlg recycled to the py y furnace l spheric pressure.
  • the carbon dioxide can be separated from the TFE by passing this mixture through a conventional EXAMPLES 7 to 10 hqhews when: scrubbef- Bmh f c and carbon w
  • Oxldg can be separated m h 1 FE m h h l ysis furnace in which the lnconel tube was 1.78 cm. in by aqueous caustic scrubbing, if the TFE is desired for diameter and 487 Cm long, with the thermocouplc some purpose otheruthim recycle monomer for being installed inside the tube and near its exit end.
  • the HFP can be separated by dlstlllatlon from the conditions were used and results were obtained. higher-boiling pyrolysis products.
  • the HFP is useful in the same manner as HFP synthesized by other techniques heretofore to make known copolymers, e.g., with TFE, or chemicals such as HFP epoxide.
  • TFE Yield to The process is normally conducted on a continuous 40 Conversion H ZP basis, i.e., continuously passing the feed mixture p through the reaction zone, followed by continuous sep- 7 319 907 aration, scrubbing and recycling.
  • the desired product HFP is recovered length of about 30.5 cm. to give a volume ofthe heated from the tails stream of the column. zone of about 5 cc.
  • the tube was heated by a 2.54 cm.
  • the recycle of carbon dioxide and unreacted TFE to diameter tubular furnace positioned about the heated the pyrolysis furnace can be done as follows: The preslength ofthe lnconel tube. The temperature of the tube sure of the TFE, CO and HCl distillate of the preced was measured using a chromel-alumel thermocouple attached to the outside of the tube near the center of the heated zone.
  • TFE and carbon dioxide were fed as ing paragraph is reduced to atmospheric pressure, and the distillate is scrubbed in water to remove HCl and is dried over CaSO
  • the composition of the resultant TFE and CO mixture is 39 percent TFE by weight and 61 percent CO by weight.
  • To 1 part of the product is added 0.41 parts of makeup TFE to give a mixture of TFE and CO having a TFE/CO weight ratio of 1.31.
  • This mixture is fed to a heated lnconel tube at a rate to give the contact times and results shown in Examples 1 l and 12; the contact time being defined as the volume of the reactor divided by the volumetric flow of the ambient temperature feed per second.
  • the improvement which comprises diluting the feed to the pyrolysis with CO at a TFEzCO weight ratio of 1:1 to 25:1 so the TFE partial pressure is at least 360 mm Hg absolute and the total pressure is 0.75 to 2.0 atmospheres absolute.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

A feed mixture of tetrafluoroethylene and a minor proportion of carbon dioxide is fed to a pyrolysis furnace operating at about atmospheric pressure and a temperature of 700* to 900*C., and a conversion of 20 to 80 percent by weight, to a yield of at least 80 percent by weight of hexafluoropropylene and a mixture of carbon dioxide and unreacted tetrafluoroethylene which is distilled from the hexafluoropropylene. The distillate mixture can be recycled to the pyrolysis furnace.

Description

United States Patent [ll] 3,873,630 West Mar. 25, 1975 [54] PROCESS FOR PYROLYZING 2,759,983 8/1956 Waddell 260/6533 TETR FLU R ETH LENE T 2,970,176 2/1961 Ten Eyck et al. 260/6533 rs g g z 0 3,009,966 11/1961 Glenside et al. 260/6533 3,519,384 7/1970 Engel et a1 423/432 [75] Inventor: Norman Eugene West, Vienna, W, 3,578,721 5/1971 Couture 260/6533 Va. 73 Assignee: E. 1. DuPont de Nemours and j 'r g r" 33 r Company, Wilmington DeL SSIS an .iammer am s me [22] Filed: June 12, 1972 [57 ABSTRACT [21] Appl. No.: 261,629 A feed mixture of tetrafluoroethylene and a minor proportion of carbon dioxide is fed to a pyrolysis furnace operating at about atmospheric pressure and a [52] US. Cl. 260/6533, 260/6536 temperature of to 900C and a Conversion of 20 [51] Int. Cl. C07c 21/20 [58] Fi Id of 5 Nb 260/653 3 to 80 percent by weight, to a yeild of at least 80 pere ea cent by weight of hexafluoropropylene and a mixture [56] Refere ces Cited of carbon dioxide and unreacted tetrafluoroethylene n which is distilled from the hexafluoropropylene. The UNITED STATES PATENTS distillate mixture can be recycled to the pyrolysis fur- 2,394,58l 2/1946 Benning ct 211 260/6533 nace, 2,551,573 5/1951 Downing et al 260/6533 2,758,138 8/1956 Nelson 260/6533 6 Chums N0 Drawmgs PROCESS FOR PYROLYZING TETRAFLUOROETHYLENE TO HEXAFLUOROPROPYLENE This invention relates to pyrolysis of tetrafluor oethylene to hexafluoropropylene.
U.S. Pat. No. 2,551,573 to Downing et al. discloses the pyrolysis of CHCIF to tetrafluoroethylene and higher boiling fluorocarbon products. U.S. Pat. No. 2,758,138 to Nelson discloses the pyrolysis of tetrafluoroethylene to hexafluoropropylene at various specific conditions involving low partial pressures, i.e., 25 to 200 mm. of Hg, of the tetrafluoroethylene feed. A process for pyrolyzing tetrafluoroethylene to hexafluoropropylene at higher pressures, viz., 0.2 to 65 psia. is disclosed in U.S. Pat. No. 2,970,176 to Ten Eyck et al., wherein the tetrafluoroethylene feed contains at least weight percent of higher boiling fluorocarbon compounds which contribute to the formation of hexafluoropropylene. A more economical process was developed later in which CHClF is pyrolyzed to both tetrafluoroethylene and hexafluoropropylene by conducting the pyrolysis within a specific conversion range of 86 to 94 percent as described in U.S. Pat. No. 3,306,940 to Halliwell.
The present invention provides a pyrolysis process for making hexafluoropropylene which is economically advantageous over all the foregoing described processes. The process involves pyrolyzing a feed of tetra tluoroethylenc (TFE) and a minor proportion of car bon dioxide in a reaction zone at a temperature of 700 to 900C, and a pressure of 0.75 to 2.0 atmospheres absolute, and a minimum partial pressure of TFE of 360 mm. ofHg absolute, to a conversion ofTFE at least of percent by weight, separating the unpyrolyzed TFE and the carbon dioxide from the hexafluoropropylene (HFP) and other pyrolysis products produced, and, ifdesired, recycling the separated TFE and carbon dioxide to the reaction zone while adding make-up TFE to maintain a substantially constant proportion of TFE in the feed to the reaction zone. The process has been operated economically at conversions of TFE up to about 80 percent. The major pyrolysis product, i.e., greater than 50 percent by weight of the pyrolysis products, is HFP. Yields of greater than 80 percent by weight and as high as 90 percent by weight of TFE to HFP, the desired product, can be obtained by this pro cess. When the unpyrolyzed TFE and carbon dioxide are recycled to the reaction zone, then steps to isolate the carbon dioxide from the TFE are unnecessary.
A major problem involved in pyrolyzing TFE is its tendency to disproportionate to carbon tetrafluoricle and carbon according to the reaction which represents both a yield loss of expensive chemical and causes plugging of the reaction apparatus. This disproportionation is an exothermic reaction so once it begins, it tends to be a runaway reaction. The invention of the aforementioned Nelson patent attempted to avoid this problem by operating at very low pressures, i.e., less than 200 mm. of Hg absolute. This low pressure of operation was obtained by continuously evacuating the pyrolysis furnace and feeding the TFE to the furnace, which, by itself, determined the pressure in the furnace. One disadvantage of this vacuum operation was the danger of leakage of air into the pyrolysis systern from the surrounding atmosphere which would result in oxidation of TFE and could give an explosive mixture of air in TFE. Another disadvantage was the need for using larger equipment for the same throughput achieved at higher pressure operations, such as disclosed in the Downing et al. patent.
The invention of the Ten Eyck et al. patent found that TFE could be pyrolyzed to HFP at higher, more conveniently obtainable pressures such as atmospheric pressure, but this required the presence of at least 5 percent of pyrolyzable fluorocarbon materials having a boiling point higher than HFP which were normally provided by recycling the higher boiling pyrolyzate, which had the disadvantage of repeated handling of highly toxic materials rather than leading to quick waste disposal thereof.
The present invention also operates at the more favored pressure condition of around atmospheric pressure but without requiring the presence of the highboiling fluorocarbon compounds and the attendant toxicity problem and yet avoiding the disproportionate problem.
The process of the present invention is most conveniently conducted preferably at atmospheric pressure by passing a mixture of the TFE and carbon dioxide through a heated tube, called a pyrolysis furnace, with the heated portion of the tube being the reaction or pyrolysis zone. The presence of the carbon dioxide in the pyrolysis furnace during the pyrolysis of TFE in the present invention prevents the undesirable disproportionation ofthe TFE despite the partial pressure ofTFE being substantially higher than that disclosed by Nelson.
With respect to the proportions of TFE and carbon dioxide in the feed to the reaction Zone (pyrolysis furnace), there is always a greater weight of TFE present than carbon dioxide, and thus the latter is present as a minor proportion (weight basis) of the feed. Typically the proportion ofTFE to carbon dioxide in the feed will be from 1:1 to 25:1 on a weight basis. At proportions of TFE/CO of greater than 25:1, it is feared that longterm repression of the disproportionation reaction will not occur. The feed mixture to the reaction zone advantageously contains at least 40 percent by weight (total feed basis) of carbon dioxide to render the mixture nonflammable in case of leakage to the atmosphere. Preferably, the partial pressure of TFE in the feed mixture is at least 450 mm. of Hg absolute.
lmmediately succeeding the pyrolysis zone of the furnace, gaseous hydrogen chloride or hydrogen fluoride is preferably injected into the pyrolysis mixture as described in U.S. Pat. No. 3,578,721 to Couture eta1., in order to prevent polymerization of unreacted TFE which would eventually cause plugging of the recovery system.
The next step in the process is to recover the unreacted TFE and carbon dioxide as a mixture from the rest of the pyrolysis mixture by techniques well known in the art, such as distillation. The boiling point of the TFE is 76.8C. and the sublimation point of carbon dioxide is -78C. which enables these compounds to be separated from the HFP (b.p. 29C) and higher boiling fluorocarbon pyrolysis products in a single distillation operation and recovered as a mixture. The distillation is conducted under pressure, such as 17.5 kg/cm (gauge), to raise the boiling point of the distillate to a convenient temperature of operation, which temperature is above the temperature at which solid CO could exist in the distillation system. If HCl is added to the pyrolyzate, as described above, it will distill with the TFE as an azeotrope therewith. 1f the additive is HF. it will a mixture to the lnconel tube via calibrated rotameters. Hydrogen chloride was injected into the exit zone of the pyrolysis tube where the temperature was about 500C. to inhibit polymerization of unreacted TFE in not dlstlll with the TFE but will remain with the HFP 5 the collection system. The lnconel tube was heated to and other hlgh'bolllhg Py y productswhen the the desired reaction temperature with a carbon dioxide HCl is distilled with the TFE and carbon dioxide, the purge d h TFE was added to the feed stream to resultant gaseous mlxlhle can be Passed through a the tube to obtain a mixture having the desired TFE/- ventional water-scrubber to remove the HCl to prevent (IQ ti Th y ol sis was conducted at about atmolhe l'lcl from behlg recycled to the py y furnace l spheric pressure. Samples of the exit gas from the tube with the recycled Carbo di ide d were scrubbed in water to remove HCl and analyzed by ll the Hcl were to be recycled to the Py y gas chromatography to establish yields and converhaee lhefe would be a Yield loss because llCl would be sions. Further details of these experiments and the rereaCtive ith TFE and i h th ifluqroqa rhene 5 1 1: sults are shown in the following Table:
HCl feed TFE Yield to Exam- Temp. Contact rate TFE/CO Conversion HFP ple C. time-sec. ml/min. wt.ratio 7r cals formed in the pyrolysis reaction. 1f the polymeriza- These results show high yields to HFP at various tion inhibitor is HF, it will have already been removed TFE/carbon dioxide feed ratios and other variations in from the TFE/CO mixture in the HFP distillation step. process conditions.
If desired, the carbon dioxide can be separated from the TFE by passing this mixture through a conventional EXAMPLES 7 to 10 hqhews when: scrubbef- Bmh f c and carbon w These experiments were conducted in a larger pyrol. Oxldg can be separated m h 1 FE m h h l ysis furnace in which the lnconel tube was 1.78 cm. in by aqueous caustic scrubbing, if the TFE is desired for diameter and 487 Cm long, with the thermocouplc some purpose otheruthim recycle monomer for being installed inside the tube and near its exit end. subsequent polymerization to valuable polym and with the procedure including pressure being essentially Copolymers' I the same as in Examples 1 to 6. The following pyrolysis The HFP can be separated by dlstlllatlon from the conditions were used and results were obtained. higher-boiling pyrolysis products. The HFP is useful in the same manner as HFP synthesized by other techniques heretofore to make known copolymers, e.g., with TFE, or chemicals such as HFP epoxide. TFE Yield to The process is normally conducted on a continuous 40 Conversion H ZP basis, i.e., continuously passing the feed mixture p through the reaction zone, followed by continuous sep- 7 319 907 aration, scrubbing and recycling. 3 $33 38 gig $313 Specific embodiments of the process of the present 0 7 6 1.0 1.54 28.8 89.6 invention are as follows: these embodiments are intended as examples of the present invention and not as HT -AT i MT an M a llmltatlon on the Scope h In these e P i These experiments were operated for 22 hours with 2? ig gg bylwellghtdunlesz l i i no problem in temperature control being encountered, cate. ie to iscacuate onte asistate cyclic dimer can be recovered as a valuable fluorocar bon chemical. or it can be pyrolyzed to HFP as is dis- EXAMPLES 11 to 12 closed in U.S. Pat. No. 3,306,940 to Halliwell. The co-distillation of TFE, CO and HCl and separation from HFP and the higher boiling fluorocarbon py- EXAMPLES l to 6 55 rolysis products can be done as follows: The pyrolyzate, A series of pyrolysis experiments was conducted for example that obtained from the run illustrated by using the following equipment and procedure: The py- Example 8, is compressed and fractionally distilled to rolysis furnace consisted of a tube of lnconel metal recover an overhead mixture consisting of unreacted (nickel-chromium-iron alloy with small amounts of sili- TFE, CO and HCl boiling at -22C. at a pressure of con); the tube had a diameter of 0.635 cm. and heating 14.7 kg/cm The desired product HFP is recovered length of about 30.5 cm. to give a volume ofthe heated from the tails stream of the column. zone of about 5 cc. The tube was heated by a 2.54 cm. The recycle of carbon dioxide and unreacted TFE to diameter tubular furnace positioned about the heated the pyrolysis furnace can be done as follows: The preslength ofthe lnconel tube. The temperature of the tube sure of the TFE, CO and HCl distillate of the preced was measured using a chromel-alumel thermocouple attached to the outside of the tube near the center of the heated zone. TFE and carbon dioxide were fed as ing paragraph is reduced to atmospheric pressure, and the distillate is scrubbed in water to remove HCl and is dried over CaSO The composition of the resultant TFE and CO mixture is 39 percent TFE by weight and 61 percent CO by weight. To 1 part of the product is added 0.41 parts of makeup TFE to give a mixture of TFE and CO having a TFE/CO weight ratio of 1.31. This mixture is fed to a heated lnconel tube at a rate to give the contact times and results shown in Examples 1 l and 12; the contact time being defined as the volume of the reactor divided by the volumetric flow of the ambient temperature feed per second.
TFE Yield to Exam- Temp. Contact TFE/CO Conversion HFP ple C. time-sec. wt.ratio A Wt.7r
percent of the TFE to hexafluoropropylene (HFP), with injection of a material selected from the class of HCl or HF into the pyrolysis mixture to prevent polymerization of unconverted TFE, followed by cooling and separation of HFP, and recycling of unconverted TFE with makeup TFE; the improvement which comprises diluting the feed to the pyrolysis with CO at a TFEzCO weight ratio of 1:1 to 25:1 so the TFE partial pressure is at least 360 mm Hg absolute and the total pressure is 0.75 to 2.0 atmospheres absolute.
2. The process of claim 1 wherein HCl or HF is separated from the cooled product mixture by water scrubbing, the HFP is separated from the TFE-CO mixture by distillation, and the TFE-CO mixture remaining is recycled.
3. The process of claim 1 wherein HCl or HF and CO is separated from the cooled product mixture by aqueous caustic scrubbing, the HFP is separated from the TFE by distillation, and the TFE remaining is recy cled.
4. The process ofclaim 1 wherein at least 40 percent by weight of said feed mixture is carbon dioxide.
5. The process of claim 1 wherein the pyrolysis is conducted to a conversion of tetrafluoroethylene of 20 to percent by weight.
6. The process of claim 5 wherein the pyrolysis is conducted to a yield of hexafluoropropylene of at least 80 percent by weight.

Claims (5)

1. IN A PROCESS FOR PYROLYZING IN A REACTION ZONE A FEED MIXTURE OF TETRAFLUOROTHYLENE (TFE) AT A TEMPERATURE BETWEEN 700* AND 900*C. TO CONVERT AT LEAST 20 PERCENT OF THE TFE TO HEXAFLUOROPROPYLENNE (HFP), WITH INNJECTION OF A MATERIAL SELECTED FROM THE CLASS OF HC1 OR HF INTO THE PYROLYSIS MIXTURE TO PREVENT POLYMERIZATION OF UNCONVERTED TFE, FOLLOWED BY COOLING AND SEPARATION OF HFP, AND RECYCLING OF UNCONVERTED TFE WITH MAKEUP TFE, THE IMPROVEMENT WHICH COMPRISES DILUTING THE FEED TO THE PYROLYSIS WITH CO2 AT A TFE:CO2 WEIGHT RATIO OF 1:1 TO 25:1 SO THE TFE PARTIAL PRES-S SURE IS AT LEAST 360 MM HG ABSOLUTE AND THE TOTAL PRESSURE IS 0.75 TO 2.0 ATMOSPHERES ABSOLUTE.
2. The process of claim 1 wherein HCl or HF is separated from the cooled product mixture by water scrubbing, the HFP is separated from the TFE-CO2 mixture by distillation, and the TFE-CO2 mixture remaining is recycled.
3. The process of claim 1 wherein HCl or HF and CO2 is separated from the cooled product mixture by aqueous caustic scrubbing, the HFP is separated from the TFE by distillation, and the TFE remaining is recycled. 4. The process of claim 1 wherein at least 40 percent by weight of said feed mixture is carbon dioxide.
5. The process of claim 1 wherein the pyrolysis is conducted to a conversion of tetrafluoroethylene of 20 to 80 percent by weight.
6. The process of claim 5 wherein the pyrolysis is conducted to a yield of hexafluoropropylene of at least 80 percent by weight.
US261629A 1972-06-12 1972-06-12 Process for pyrolyzing tetrafluoroethylene to hexafluoropropylene Expired - Lifetime US3873630A (en)

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US261629A US3873630A (en) 1972-06-12 1972-06-12 Process for pyrolyzing tetrafluoroethylene to hexafluoropropylene
CA172,485A CA1015771A (en) 1972-06-12 1973-05-28 Process for pyrolyzing tetrafluoroethylene to hexafluoropropylene
JP6344673A JPS5728696B2 (en) 1972-06-12 1973-06-07
FR7321021A FR2187743B1 (en) 1972-06-12 1973-06-08
GB2771973A GB1384036A (en) 1972-06-12 1973-06-11 Process for pyrolyzing tetrafluoroethylene to hexafluoropropylene
IT50667/73A IT989657B (en) 1972-06-12 1973-06-11 PROCESS FOR THE PYROLYSIS OF TETRAFLUOROETHYLENE AND HEXAFLUORO PROPYLENE
DE2329750A DE2329750C2 (en) 1972-06-12 1973-06-12 Process for the production of hexafluoropropene by pyrolysis of tetrafluoroethylene
NL7308149A NL7308149A (en) 1972-06-12 1973-06-12

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4365102A (en) * 1980-09-29 1982-12-21 E. I. Du Pont De Nemours And Company Method of manufacturing perfluoromethane and perfluoroethane
US5043491A (en) * 1989-12-19 1991-08-27 E. I. Du Pont De Nemours And Company Multistep synthesis of hexafluoropropylene
US5057634A (en) * 1989-12-19 1991-10-15 E. I. Du Pont De Nemours And Company Multistep synthesis of hexafluoropropylene
US5334783A (en) * 1988-03-14 1994-08-02 Hoechst Aktiengesellschaft Process for the preparation of hexafluoropropene
US5345013A (en) * 1993-06-10 1994-09-06 E. I. Du Pont De Nemours And Company Safe handling of tetrafluoroethylene
KR100361585B1 (en) * 2000-11-11 2002-11-22 한국과학기술연구원 Preparation of Hexafluoropropylene(HFP) by the pyrolysis of trifluoromethane(R23) and tetrafluoroethylene(TFE)
KR100405187B1 (en) * 2001-02-20 2003-11-12 한국과학기술연구원 Preparation Method of Octafluorecyclobutane(RC318)
KR100405895B1 (en) * 2001-02-20 2003-11-14 한국과학기술연구원 Preparation Method of Hexafluoropropylene(HFP) and Octafluorecyclobutane(RC318) simultaneously
US20040002621A1 (en) * 2002-06-26 2004-01-01 Barnes John James Synthesis of hexafluoropropylene
US7271301B2 (en) 2000-07-14 2007-09-18 E.I. Du Pont De Nemours And Company Synthesis of perfluoroolefins

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US2551573A (en) * 1945-11-30 1951-05-08 Du Pont Pyrolysis of chloro-fluoro alkanes
US2758138A (en) * 1954-05-06 1956-08-07 Du Pont Pyrolysis process for making perfluoropropene from tetrafluoroethylene
US2759983A (en) * 1954-05-06 1956-08-21 Du Pont Pyrolysis process for preparing hexafluoropropene from tetrafluoroethylene polymer
US2970176A (en) * 1957-10-31 1961-01-31 Du Pont Pyrolysis of fluorocarbons to hexafluoropropylene
US3009966A (en) * 1960-02-08 1961-11-21 Pennsalt Chemicals Corp Production of fluorinated compounds
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Cited By (11)

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Publication number Priority date Publication date Assignee Title
US4365102A (en) * 1980-09-29 1982-12-21 E. I. Du Pont De Nemours And Company Method of manufacturing perfluoromethane and perfluoroethane
US5334783A (en) * 1988-03-14 1994-08-02 Hoechst Aktiengesellschaft Process for the preparation of hexafluoropropene
US5043491A (en) * 1989-12-19 1991-08-27 E. I. Du Pont De Nemours And Company Multistep synthesis of hexafluoropropylene
US5057634A (en) * 1989-12-19 1991-10-15 E. I. Du Pont De Nemours And Company Multistep synthesis of hexafluoropropylene
US5345013A (en) * 1993-06-10 1994-09-06 E. I. Du Pont De Nemours And Company Safe handling of tetrafluoroethylene
US7271301B2 (en) 2000-07-14 2007-09-18 E.I. Du Pont De Nemours And Company Synthesis of perfluoroolefins
KR100361585B1 (en) * 2000-11-11 2002-11-22 한국과학기술연구원 Preparation of Hexafluoropropylene(HFP) by the pyrolysis of trifluoromethane(R23) and tetrafluoroethylene(TFE)
KR100405187B1 (en) * 2001-02-20 2003-11-12 한국과학기술연구원 Preparation Method of Octafluorecyclobutane(RC318)
KR100405895B1 (en) * 2001-02-20 2003-11-14 한국과학기술연구원 Preparation Method of Hexafluoropropylene(HFP) and Octafluorecyclobutane(RC318) simultaneously
US20040002621A1 (en) * 2002-06-26 2004-01-01 Barnes John James Synthesis of hexafluoropropylene
US6924403B2 (en) 2002-06-26 2005-08-02 E. I. Du Pont De Nemours And Company Synthesis of hexafluoropropylene

Also Published As

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GB1384036A (en) 1975-02-19
JPS5728696B2 (en) 1982-06-18
DE2329750C2 (en) 1982-07-29
JPS4948608A (en) 1974-05-11
FR2187743B1 (en) 1977-02-11
IT989657B (en) 1975-06-10
DE2329750A1 (en) 1974-01-03
CA1015771A (en) 1977-08-16
FR2187743A1 (en) 1974-01-18
NL7308149A (en) 1973-12-14

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