United States Patent (19) 11) 4,108,966 Lileck 45 Aug. 22, 1978

54 PREPARATION OF ODNE (56) References Cited PENTAFLUORIDE BY DIRECT FLUORINATION OF MOLTEN ODNE U.S. PATENT DOCUMENTS 3,336,111 8/1967 Watson et al...... 423A69 (75) Inventor: John Theodore Lileck, Tamaqua, Pa. Primary Examiner-O. R. Vertiz Assistant Examiner-Thomas W. Roy (73) Assignee: Air Products & Chemicals, Inc., Attorney, Agent, or Firm-Richard A. Dannells; Barry Allentown, Pa. Moyerman (57) ABSTRACT 21 Appl. No.: 845,695 Iodine pentafluoride is produced from gaseous fluorine and molten iodine by contacting the iodine with fluo 22 Filed: Oct. 26, 1977 rine in a reaction zone maintained at a temperature in the range of about 114 to about 280 C. The process 51) Int. Cl? ...... CO1B 7/24 results in high yields of pure iodine pentafluoride. 52) U.S. C...... 423/466 58 Field of Search ...... 423/466, 462 8 Claims, 1 Drawing Figure

WENT U.S. Patent Aug. 22, 1978 4,108,966

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AR 4,108,966 1. 2 external heating means which in this instance, was heat PREPARATION OF ODINE PENTAFLUORIDE ing coil 3. The iodine was melted and maintained at 121 BY DIRECT FLUORINATION OF MOLTEN C (250 F) by means of conventional temperature con ODNE trolling equipment not shown. Elemental fluorine was introduced through valve 4, flow meter 5, valve 6, line BACKGROUND OF THE INVENTION 7 and sparger 8 immersed below the liquid level of 1. Field of the Invention iodine in reactor 1. Any suitable means can be used to This invention relates to an improved process for the uniformly distribute the fluorine in the form of fine preparation of iodine pentafluoride. bubbles adjacent to the bottom of the reactor. 2. Description of the Prior Art 10 Typically, fluorine has a purity of 99% with hydro It is known to produce iodine pentafluoride (IFs) by fluoric acid and nitrogen being the major impurities. reacting gaseous fluorine with solid iodine crystals; see: The rate of introduction of the fluorine was maintained Schumb et al., "Iodine Heptafluoride,' Industrial and at an average rate of approximately 14 cubic meters per Engineering Chemistry, Vol. 42, July 1950, pp. hour per square meter of iodine (46 ft./hr./ft.) which 1383-1386. One of the disadvantages of this process is 15 assisted in maintaining the reactor temperature within that the bed of solid iodine crystals serves as a poor heat the optimum temperature range of 121 to 131° C transfer medium. This causes hotspots to develop in the (250-270 F). The practical range for the introduction reaction zone leading to poor temperature control. Ad rate of fluorine can be as low as 2.5 m./hr./m. of iodine ditionally, iodine heptafluoride (IF) formed by the (8 ft./hr./ft.) to as high as 50 m./hr./m.of iodine (163 reaction between the IF5 product vapors and the excess 20 ft./hr./ft.) or even higher depending on removal of flourine is greatly aggravated by these hot spots in the the heat of reaction from the system. Upon commence reaction zone. Another disadvantage is the plugging of ment of the exothermic reaction, heating coil 3 was shut the process lines downstream from the reaction zone by off and external cooling means, which in this example, the recrystallization of iodine. was air blower 10, was used to remove the heat of reac A current commercial method for the production of 25 tion from reactor 1. The pressure in reactor 1 was main IF is disclosed in Tepp, U.S. Pat. No. 3,367,746 in tained in the range of 212 kilopascals (30.7 psia) to 308 which gaseous fluorine is reacted with iodine dissolved kilopascals (44.7 psia) by periodically venting reactor 1 in an inert solvent such as the IF5 product. The tempera through line 12, valve 14 and condenser 16. Condenser ture of the reaction is critical and must be maintained 16 allowed gas impurities such as nitrogen, HF and below 98' C, the boiling point of the IF solvent. The 30 fluorine to be vented from the system and to condense chief disadvantage of this process is the requirement for any IFs that was entrained in the gaseous impurities for a large number of reaction vessels and auxiliary equip return to reactor 1. After 3,482 grams (7.7 pounds) of ment in order to dissolve the iodine in the IFS solvent fluorine had been added to reactor 1, nitrogen was in and to return the resulting iodine solution to the reac troduced into the reactor through valve 18 and line 20 tion zone. 35 to maintain the desired pressure in the reactor. Nitrogen was also employed to pass through line 22 and valve 24 SUMMARY OF THE INVENTION to purge product line 26. It is obvious that other gases In contrast to these prior art methods, the process of inert to the IF5 reaction can be employed for this pur the present invention has improved heat transfer pose. throughout the reaction zone resulting in excellent tem- 40 The reaction was terminated after the temperature of perature control and high yields of IFs, has practically the reactor began to decrease for a total reaction time of no plugging problems due to iodine recrystallization approximately 19 hours. Upon completion of the reac nor yield losses due to the formation of IF, and utilizes tion, 7,486 grams (16.5 pounds) of IFs product was a minimum of process vessels and equipment resulting transferred from reactor 1 via lines 7 and 26 through in obvious economies. The heat of exothermic reaction 45 valve 28 to storage vessel 30. The IFs yield based on in the present process is transferred to the iodine in its iodine was 98% and based on fluorine was 92%. molten state which is more easily cooled by conven As shown in the drawing, the IF5 product was pres tional heat exchange techniques to avoid the formation sured through sparger 8 and line 7 by means of nitrogen of hot spots in the reaction zone. introduced through line 20. Alternatively, the product The improved process comprises contacting iodine in 50 can be pressured from the reactor through a separate a molten state with gaseous fluorine in a reaction zone at lines by means of any suitable inert gas. a temperature in the range of about 114 to 280 C, Due to the particular sparging system of this example, preferably 120° to 160° C. The pressure in the reaction 454 grams of iodine were found unreacted at the botton zone is held at or above the vapor pressure of IFs to of the reactor. Preferably, the fluorine should be intro prevent the loss of product material and to lessen the 55 duced as close to the bottom of the reactor to prevent formation of by-product IF. The pressure of the reac such an occurrence. tion generally ranges from about 160 kilopascals (23 The product quality was maintained by monitoring psia) to 7,600 kilopascals (1100 psia), preferably 195 the color of the product as it passed through transparent kilopascals (28 psia) to 630 kilopascals (91 psia). section 32 of line 26. Trace amounts of free iodine in the 60 product leads to its discoloration. Chemical analyses A BRIEF DESCRIPTION OF THE DRAWING have shown that a free iodine content in the product of The drawing is a process flow diagram of the process less than 0.015% results in a product having a light of the present invention. orange color. The present process process produced a high purity product essentially water white in color. DETAILED DESCRIPTION AND EXAMPLE OF A specific mode of operating the process of the pres THE PRESENT INVENTION ent invention on a batch basis has been described. It is A total of 4,777 grams (10.5 pounds) of iodine crystals contempated that this process can be run on a continu were initially charged to nickel reactor 1 equipped with ous basis by providing for the continuous introduction 4,108,966 3 4. of iodine and continuous removal of IF5 product by zone, and recovering the resulting iodine pentafluoride techniques obvious to one skilled in the art. Other varia from the reaction zone. tions can be made to the process without departing from 3. The process as in claim 2 wherein said inert gas is the spirit of the invention. All such variations that fall nitrogen. within the scope of the appended claims are intended to be embraced thereby. 4. The process as in claim 2 wherein the iodine is I claim: continuously introduced into said reaction zone and the 1. A process for producing iodine pentafluoride from iodine pentafluoride is continuously removed from said iodine and gaseous fluorine which comprises contacting reaction zone. said fluorine with iodine in a molten state in a reaction 10 5. The process as in claim 2 wherein the fluorine is zone maintained at a temperature in the range of about introduced in said reaction zone through means to uni 114 to 280 and at a pressure in the range of about 160 formly distribute the fluorine in the form of bubbles to 7,600 kilopascals to effect a reaction between said below the liquid level of iodine. fluorine and molten iodine and recovering the resulting 6. The process as in claim 5 wherein said reaction iodine pentafluoride. 15 zone is a vertical reactor having a sparger adjacent to its 2. A process for producing iodine pentafluoride bottom for uniformly distributing the fluorine in the which comprises introducing gaseous fluorine through iodine. iodine in a molten state below the liquid level in a reac 7. The process as in claim 6 wherein the iodine penta tion. zone to effect a reaction between said fluorine and fluoride is pressured from said reaction zone by means molten iodine, maintaining the temperature in the reac 20 of an inert gas. tion zone in the range of about 120 to 160 C, maintain 8. The process as in claim 7 wherein said inert gas in ing the pressure in the range of about 195 to 630 kilopas nitrogen. cals by the introduction of an inert gas into the reaction k is :: *k 25

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