Patent Publication Number: US-3878257-A

Title: Catalytic conversion of 1,1,2-trichlorotrifluoropropene-1 to 2-chloropentafluoropropene

Description:
United States Patent Bruce, Jr.  
  [111 3,878,257 [451 Apr. 15, 1975 CATALYTIC CONVERSION OF 1,1,2-TRICHLOROTRIFLUOROPROPENE-l TO 2-CHLOROPENTAFLUOROPROPENE John MacMillan Bruce, Jr., Wilmington, Del.  
 Inventor:  
 Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.  
 Filed: Aug. 10, 1973 Appl. N0.: 387,478  
 US. Cl 260/653.4; 252/468 Int. Cl. C07c 17/20 Field of Search 260/653.4  
 [56] References Cited UNITED STATES PATENTS 2,917,558 12/1959 Cunningham et al 260/6534 Primary ExaminerDaniel D. Horwitz [57] ABSTRACT 4 Claims, No Drawings l CATALYTIC CONVERSION OF 1,l,Z-TRICHLOROTRIFLUOROPROPENE-1 TO Z-CHLOROPENTAFLUOROPROPENE BACKGROUND OF THE INVENTION The compound, 2-chloropentafluoropropene is known in the art as a fumigant. As disclosed in U.S. Pat. No. 2,917,558, the compound may be prepared by reaction of 1,1,2-trichlorotrifluoropropene-1 with hydrogen fluoride at a temperature above 300F. utilizing anhydrous aluminum fluoride catalyst.  
 SUMMARY OF THE INVENTION The present invention is directed to the production of 2-chloropentafluoropropene in high conversion and yield by reaction of hydrogen fluoride with 1,1,2- trichlorotrifluoropropene-l employing as a catalyst activated anhydrous chromium (III) oxide in combination with divalent zinc ion.  
  Conversion of 1,1,2-trichlorotrifiuoropropene-l to 2-chloropentafluoropropene is set forth in US. Pat. No. 2,917,558 with disclosed yields of 27 and 29 percent. In contrast with the catalyst combination of this disclosure, conversions of the order of 95-100 percent and yields of the order of 80 percent have been obtained.  
  In addition to use as a fumigant, the compound is a useful intermediate in making hexafluoropropene.  
 DETAILED DESCRIPTION OF THE INVENTION The use of activated anhydrous chromium (III) oxide in combination with divalent zinc as catalyst allows both a high conversion of CF CCl=CCl and a high yield of CF CCl=CF The activated anhydrous chromium (III) oxide portion of the catalyst is disclosed in U.S. Pat. No. 3,258,500. The oxide is activated by heating in an inert atmosphere at about 400C. to about 600C. with a preferred temperature of the order of 500C.  
  A preferred type of anhydrous chromium (III) oxide catalyst is one with a high surface area and is of the gel type. This catalyst is specifically disclosed in US. Pat. No. 3,258,500 as well as by Ruthruff in Inorganic Syntheses, Vol. II, pages 190 to 193 published in 1946 by Me Graw-Hill Book Co.  
  The remaining portion of the catalyst consists of divalent zinc ion which will be present as a solid compound at the operating temperatures and pressures of the reaction. Suitable examples of compounds useful are divalent zinc salts including zinc chloride, zinc bromide, zinc iodide, zinc sulfate and zinc acetate.  
  It is believed that the zinc salt is converted to zinc fluoride at the operating conditions of the reaction since zinc salts with low melting points may be employed. In any event the zinc ion is present in the catalyst combination at the reaction conditions employed.  
  The concentration of Zn may vary over a wide range relative to the chromium oxide since criticality exists in the combination of anhydrous (III) oxide and divalent zinc rather than the amount of each portion of the catalyst. An illustrative concentration of zinc is from 1 to mole percent with a preferred range of 12 to 16 percent.  
  The catalyst may also contain diluents, carriers and small quantities of impurities.  
  The reaction of CF CCl=CC1 with hydrogen fluoride is undertaken in the vapor phase at temperatures bebe used. 7  
 For the hydrofluorination, hydrogen fluoride is the I preferred source of the hydrogen and fluorine,&#39;;However, it is within the scope of this invention to employ separate source materials which serve asthe hydrogen fluoride precursor. Illustratively, these source materials may act in situ to form hydrogen fluoride at the operating conditions of the catalytic conversion. The hydrogen fluoride will be at an excess over that required for conversion of the 1,1,2-trichlorotrifluoropropene-l. Molar ratios based upon hydrogen fluoride to CF CCl=CCl may range from 2:1 to 30:1. A preferred ratio will be of the order of 10:1.  
  The contact time of CF CCl=CC1 and the hydrogen fluoride with the catalyst will be dependent upon the operating conditions and the activity of the catalyst. Higher operating temperatures will denote a shorter requirement for catalyst contact. Contact times of the order of about 1 minute or less may be used with a contact time of 1 to 20 seconds preferred. A more preferred contact time is 2 to 10 seconds. Excessively long contact times will denote an excess formation of byproduct compounds.  
  To further illustrate the innovative aspects of the invention, the following examples are provided:  
 EXAMPLE I CATALYST PREPARATION Chromium oxide (Cr O in the form of a gel was prepared in accordance with the technique disclosed in Inorganic Syntheses, 2, 190.  
  Into a beaker was placed grams of the Cr O which was covered with a solution of 30 grams ZnCl dissolved in 80 ml. water. The Cr O decrepitated upon treatment with the aqueous solution. With occasional stirring of the mixture, water was evaporated in an oven maintained at a temperature of C.  
 SYNTHESES OF CF CCI=CF A 1 inch X 18 inches nickel reactor tube containing a thermocouple well in the center, was charged with 53 grams (4 inches bed) of the cr,o,-zn catalyst described above. The catalyst was heated at 400C. under a stream of N for a period of 16 hours and then treated with HF cc/min) for 3.5 hours. The temperature of the reactor was maintained between 500-504 while the following were added at the rates indicated: HP, 135 cc/min; CF CCl=CCl 12 cc/min; N 60 cc/min. After running a period of about 6 hours a sample of effluent was analyzed by GC analysis which disclosed the following: conversion of CF CCl=CCl 97 percent; yields: CF CCl=CF 83 percent; CF CCl=CFCl, 13 percent; CF CH=CF 3 percent; other, 1 percent. Contact time in the 4 inches catalyst bed was about 6 seconds.  
 EXAMPLE 2 In a similar procedure as Example 1, the 1 inch X 18 inches nickel reactor was charged with a 3% inches bed of Cr O as catalyst (no Zn&#34; present) which was held 3 at 400C. under N for 16 hours followed by treatment with HF (135 seconds/min.) at 400C. for two hours and 500C. for 3 hours. HF, CF CCl-CCl and N were added in the same fashion as in Example 1.  
  After operating at about 500 for about 2 hours GC analysis of the effluent disclosed the following: conversion of CF CCl=CCl 99 percent; CF CCl=CF 22 percent; CF CCl=CFCl, 6 percent; CF CH=CF 8 percent; CF Cl 6 percent; CF CH CF 23 percent; CF CHCICF 21 percent; other, 14 percent. Contact time was about 5.5 seconds.  
  Although the invention has been described by way of specific embodiments, it is not intended to be limited thereto. As will be apparent to those skilled in the art, numerous embodiments can be made without departing from the spirit of the invention or the scope of the following claims.  
 What is claimed is:  
  1. In a catalyzed reaction at a temperature of about 400 to 600C. of l,l,2-trichlorotrifluoropropene-l with hydrogen fluoride to form 2-chloropentafluoropropene, the improvement comprising employing a catalyst combination of activated anhydrous chromium (Ill) oxide and a divalent zinc compound.  
  2. The process of claim 1 wherein said oxide is prescut as a gel and said divalent zinc compound is present as a zinc salt.  
  3. The process of claim 2 wherein said zinc compound is present in an amount of l to 20 mole percent of said catalyst combination.  
 4. The process of claim 3 wherein a catalyst contact time of l to 20 seconds is used.