PROCESS. OF A STAGE. TO PRODUCE HORROF UOROCARBONS FROM PERCHLORETHYLENE
FIELD OF THE INVENTION The present invention relates to a process for producing hydrochlorofluorocarbons and hydrofluorocarbons. In particular, the invention relates to the production of CHCIFCF3 (HCFC-124), CHF2C1F2 (HCFC-124a) and CHF2CF3 (HFC-125) and -. from the perchlorethylene, in a single reactor
stage. These compounds are useful in a variety of industrial applications, including blowing agents, refrigerants, sterilizing gases and solvent applications. BACKGROUND DB INVENTION 15 Numerous chlorofluorocarbons (CFCs) are known. in the art, which have industrial and domestic applications, which include their use as refrigerants, and solvent and blowing applications, however, they are believed to be detrimental to the ozone layer that protects the
Earth. Because of the potential danger to atmospheric ozone from CFCs, it is convenient to develop substitutes that function substantially in the same way, but that do not essentially reduce ozone. Several replacement materials include 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124), 1-chloro-1,2,1,2,2-tetrafluorochloroethane (HCFC-124a) and pentafluoroethane (HFC-125). ). It is expected that the demand for these materials will be increased drastically in the future and thus the procedures, commercially viable, for the preparation of these materials are advantageous. Many processes for the production of HCFCs and HFCs are known in the art. Many of them use catalysts that are not very selective and in addition to producing the desired materials, they also produce a wide variety of inconvenient byproducts. Some of the catalysts have a very short life and thus they are not practical for commercial applications. In addition, the operating conditions described in the art do not make commercial production practical. The following are typical methods of the prior art. U.A. Patent No. 3,258,500 describes a one-step process for the production of HCFC-124 and HFC-125, by the reaction of tetrachlorethylene with anhydrous hydrogen fluoride, in the presence of a fluorination catalyst. This catalyst may be activated anhydrous chromium oxide on alumina. This procedure has an excessively low selectivity and yield. The patent of E. U. A., No. 4,843,181, describes a one-stage, gas phase process that reacts tetrachlorethylene with hydrogen fluoride in the presence of chromium oxide. In order to obtain the desired product, a long extreme contact time between the catalyst and the reagents is required. The patent of E. U. A., No. 4,967,023 describes a single-stage process which hydrofluorically perchlorethylene with a chromium oxide on an AIF3 catalyst. A low conversion of the reactants is noted. Similar procedures of a stage and low yields are described in the patent of E. U. A., No. 4,766,260. The gas phase conversion of perchlorethylene to other HCFCs is shown in U.S. Patent No. 5,091,601. U.A. Patent No. 5,155,082 discloses a partially fluorinated aluminum / chromium oxide catalyst for the hydrofluorination of a halogenated aliphatic hydrocarbon to produce a chlorofluorocarbon, hydrochlorofluorocarbon or hydrofluorocarbon. According to this patent, when HCFC-124 is the desired hydrofluorocarbon, the preferred starting material is HCFC-123 or HCFC-123a. This HCFC-123 or HCFC-123a, in turn, is preferably produced from the perchlorethylene as the starting material. This leads to a system of two reactors. Although it is mentioned that many of the by-products formed during the course of the fluorination reactions can be recycled for the production of additional hydrochlorofluorocarbons and HCFC-124 is specifically listed as one of the byproducts of the HCFC-123 production of perchloro-ethylene, there is no description of any process for obtaining HCFC-124, HCFC-124a or HFC-125, as the main products of perchlorethylene from a single-step reaction. Prior to this invention, the production of HCFC-124 involved two separate reagent steps. First, perchlorethylene was subjected to hydrofluorination to produce HCFC-123 and HCFC-123a, and then, in a separate reagent system, this HCFC-123 and HCFC-123a was subjected to hydrofluorination to produce HCFC-124. Now, because of this invention there is no longer a need for two separate reagent stages and all the additional equipment required for this two-stage system. The process of the invention produces HCFC-124 as the main product, as does HCFC-124a and HFC-125 from perchlorethylene, in a single reactive step. Consequently, a significant advantage is that less equipment is required, particularly, since only one reactor vessel is necessary. SUMMARY OF THE INVENTION The invention provides a process for the preparation of one or more of CHC1FCF3, CHF2CCIF2 and CHF2CF3, which comprises the reaction of perchlorethylene with hydrogen fluoride, in the vapor phase, in the presence of a fluorination catalyst, in a reaction vessel. Next, the reaction product is distilled to produce a distillate comprising HCl, CHCIFCF3, CHF2CCIF2 and CHF2CF3, and a smaller amount of HF, and a bottom product which includes perchlorethylene, hydrogen fluoride and intermediate organic products . A phase separation of the bottom product is then carried out to thereby substantially separate the hydrogen fluoride from a mixture of the perchlorethylene and the intermediate organic products. BRIEF DESCRIPTION OF THE DRAWING __; Figure 1 is a schematic representation of the
process of the invention. DETAILED DESCRIPTION OF THE INVENTION As a first step in the process of the invention, perchlorethylene and anhydrous hydrogen fluoride are reacted with each other in the presence of the catalyst. The reaction can be conducted in any suitable reaction vessel, but which must be constructed of materials that are resistant to the corrosive effects of hydrogen fluoride, such as HASTALLOY, INCONEL and MONEL materials. The molar ratio of hydrogen fluoride
to perchlorethylene, is adjusted to be from about 2: 1 to 50: 1, and preferably from about 5: 1 to 40: 1 and more preferably from 6: 1 to 20: 1. The temperature at which the reaction is conducted varies preferably from about 200 to about 600 or more preferably from
about 250 to 500 [deg.] C. and still more preferably about 300 to about 400 [deg.] C., inside the reactor. This reactor is preferably an adiabatic reactor filled with a fluorination catalyst. The organic vapor is allowed to make contact with the fluorination catalyst for about 0.5 to 120 seconds, more preferably about 2 to about 90 seconds and even more preferably about 10 to about 60 seconds. For the purposes of this invention, the contact time is the time required for the gaseous reactants to pass through the catalyst bed, assuming that this catalyst bed is 100% empty. The reaction pressure preferably ranges from atmospheric pressure to about 28 kg / cm2, preferably from about 3.5 to about 21 kg / cm2 and more preferably from about 7 to about 17.5 kg / cm2. Any of the fluorination catalysts, known in the art, can be used. These fluorination catalysts include, but are not limited to, oxides, halides, oxyhalides and inorganic salts of chromium, aluminum, cobalt, manganese, nickel and iron, Cr2? 3 / Al2? 3, Cr203 / A1F3, Cr203 / carbon, C? Cl2 / Cr2? 3 / Al2? 3, NCl2 / Cr2? 3 / Al2? 3, C? Cl2 / AlF3 and NCICI2 / AIF3. Chromium oxide / aluminum oxide catalysts are described in U.S. Patent No. 5,155,082, which is incorporated herein by reference. The chromium oxide can be crystalline or amorphous. Amorphous chromium oxide is preferred. Chromium oxide (Cr2? 3 > is a commercially available material, which can be purchased in a variety of particle sizes.) Chromium oxide, for example, can be purchased from Great Western Inorganics, Golden, Colorado. and from Mallinckrodt Specialty Chemicals Company, St. Louis, Missouri In the preferred embodiment, 5 small amounts of gaseous oxygen or air flow through the chromium oxide to maintain catalyst activity.The amount of air or oxygen supplied to the reactor is preferably from about 0.01 to 30 mole percent of oxygen relative to the organic load
total of the reactor. A more preferred amount ranges from about 0.05 to 20 mole percent and even more preferably from 0.1 to 10 mole percent. The resulting mixture of products includes HCFC-124, HCFC-124a, HCFC-125 as well as 1,1-dichloro-2,2,2-trifluoroethane
(HCFC-123), 1, 1,2-trichloro-2,2-difluoroethane (HCFC-122), trichlorofluoroethylene (HCFC-1111), hydrogen chloride and
^ Hydrogen fluoride and unreacted perchlorethylene. The product mixture is then subjected to distillation to form a distillate portion and a portion of
funds. The primary purpose of distillation is to separate HCFC-124 from hydrogen fluoride. Distillation, rather than another type of separation, is necessary for this separation, because it was found that HCFC-124 dissolves in hydrogen fluoride. The distillation is preferably conducted at a pressure ranging from 0.35 to 35 kg / cm2, preferably at 0.7 to 28 kg / cm2 and even more preferably from 3.5 to 21 kg / cm2, approximately. The pressure of the distillation column inherently determines the operating temperature of the distillation. The distillate portion includes substantially all HCFC-124, HCFC-124a, HCFC-125, hydrogen chloride and air or oxygen present in the product mixture, as well as a lower amount of hydrogen fluoride. The funding portion includes substantially all of the hydrogen fluoride, perchlorethylene, HCFC-123, HCFC-122 and HCFC-1111, present in the product mix. Optionally an additional distillation column can be used before the distillation column described above, to remove HCl and non-condensable products, such as air or oxygen. In the preferred embodiment, hydrogen chloride and hydrogen fluoride are substantially removed from the distillate portion, by means of a conventional scrubbing apparatus leaving HCFC-124, HCFC-124a and HCFC-125. If desired, HCFC-124, HCFC-124a and HCFC-125 can be separated individually by means of a conventional distillation process, well known to those skilled in the art. The portion of funds undergoes phase separation, in which hydrogen fluoride is separated from an organic portion, which includes perchlorethylene, HCFC-123, HCFC-122 and HCFC-1111. The phase separator can be a holding tank, in which the HF migrates to the top and the other ingredients settle to the bottom. The HF and background components are then pumped and separated individually. The hydrogen fluoride and the organic portion are then recycled so that they react with the fresh hydrogen fluoride and perchlorethylene. Although both effluent streams are recycled back to the reactor, this phase separator is necessary to control the molar ratio of the reactive materials and determine how much fresh charge will be added. A critical feature of the invention is that the reverse placement of the phase separator, before the distillation column, will not produce an operating process. This is because HCFC is soluble in hydrogen fluoride. They can be separated in the distillation column, but not in the phase separator. Therefore, if the reverse order is used, HCFC-124 must remain undissolved in hydrogen fluoride. If a larger proportion of HCFC-125 is desired as the main product, the distillation column can be operated at a lower temperature of the condenser, in order to cause HCFC-124 and HCFC-124a to exit by means of the effluent. funds, for recycling and return to the reactor. Alternatively, HCFC-124 and HCFC-124a can be returned for recycling and returned to the reactor after leaving the scrubber.
j Figure 1 provides a schematic representation of a preferred process flow of the invention. A charging stream 2 of hydrogen fluoride, fresh gas, and a fresh charging stream of gaseous perchlorethylene 5, are mixed to form a reactor charge stream 6, which is fed into a reactor 8. The effluent of the Reactor 10 is the mixing stream of the product that enters a column 12 for distillation. Distillate stream 14 includes HCFC-124 as the main product 0 and additionally includes HCFC-124a, HFC-125, HCl, air or oxygen, and a minor amount of HF. In the preferred embodiment, the distillate stream 14 is fed into an additional separation and / or purification apparatus, such as a conventional scrubber 16, to remove the HF and HCl. Another distillation column 5 (not shown) separates the component of HCFC-124a and HCFC-125. Such a scrubber is well known in the art and conventionally comprises scrubbing with aqueous NaOH or KOH, under conditions sufficient to neutralize the residual acidity. The bottom stream 18 is fed to a phase separator 20. This stream contains the vast majority of hydrogen fluoride as well as an organic mixture of HCFC-123, HCFC-122, HCFC-1111 and perchlorethylene. Stream 18 is separated by phase separator 20 into a first HF recycle stream 22 and a second recycle stream 24 containing HCFC-123, HCFC-122, HCFC-1111 and perchlorethylene. Both recycle streams 22 and 24 are passed through pumps 26 and 28. Recycling streams 30 and 32 then melt into reactor charge stream 6. It will be readily appreciated that the respective amounts of the component of the product mixture will vary depending on the reaction conditions and the catalysts employed. Similarly, the amounts of the components of the distillate and the portions of funds may vary for the person skilled in the art. The method of the invention provides a method for obtaining HCFC-124 as the main product with high productivity, usually greater than 0.160 kg / hr / liter. As used herein, the term "major product" means the only product that is produced by the reactive system in the greatest amount. The present invention is illustrated more fully by the following non-limiting examples. EXAMPLE 1 Perchlorethylene (PCE), substantially pure, was fed into a 2.54 cm reactor, manufactured from MONEL, at a rate of 60 grams / hour. The reactor contains 110 ml of amorphous Cr 2? 3 catalyst. The catalyst time in the stream is 118 hours. The reactor temperature is 330OC and the pressure is 3.5 kg / cm2. The anhydrous hydrogen fluoride (HF) is simultaneously fed to the reactor at a rate of 58.2 g / hr. The molar ratio of HF to PCE is 8. The air was co-fed to the reactor at a molar ratio of 02: PCE of about 2 mol%. The contact time is 11 seconds. The effluent from the reactor was analyzed using in-line gas chromatography. The results are shown in Table 1. The conversion of the PCE is 67.1%. The "120" products combined account for about 96%. The ratio of HCFC-124 / HFC-125 was 3/1. The productivity of HCFC-124 and HCFC-124a is 0.0897 kg / hr / liter of catalyst. Total non-recyclable products were 3.8%. The main product is HCFC-123 and HCFC-123a, which is an intermediate product to produce HCFC-124. TABLE 1
Non-recyclable products:
Productivity (kg / hr / liter):
EXAMPLE 2 In order to simulate the recycling of intermediate HCFC-123, an organic load of 30/70% by weight of PCE / HCFC-123 was fed to the same reactor used in Example 1. The pressure is 14 kg / cm2 and the HF and the organic products were also fed to the reactor at a molar ratio of HF: organic products of 7.6. The temperature is 3302C..
The contact time is 18 seconds and the catalyst time in the stream is 282 hours. The air was co-fed at a 1% molar ratio of O2: organic products. The reactor effluent was analyzed using gas chromatography. The results are shown in the first column of Table 2. The productivity of HCFC-124 and HCFC-124a was increased to 0.1842 kg / hr / liter of catalyst. Combined products 120 add up to 97.8%. The term "combined products 120" refers to the combined selectivities of the desired products and the recyclable by-products of chlorofluorocarbons and / or hydrochlorofluorocarbons produced in a given hydrofluorination reaction. The ratio of HCFC-124 / HFC-125 is 1 / 0.98. The conversion of the PCE is 81.6%. The net conversion of HCFC-123 / HCFC-123a is 3.7, which suggests that the recycling ratio of HCFC-123 is approximately 70%. Total non-recyclable byproducts account for approximately 2.4%. EXAMPLE 3 The same rector and the reaction conditions were used as in Example 2, except that the molar ratio of HF: organic products was changed to 4.9, the contact time of 24 seconds and the time of the catalyst in the stream is 337 hours. The results are shown in the second column of Table 2. The change in the molar ratio of HF: organic products reduces the selectivity of products 120 to 94.9% and increases the conversion of HCFC-123 / HCFC-123a to 19.7. The conversion of the PCE is 78.1%. These results suggest that a lower molar ratio of HF: organic products is not beneficial for the reaction and this reaction of the PCE with HF seems to be slower than that of HCFC-123 and HF.
EXAMPLE 4 The same reactor and reaction conditions were used as in Example 3, except that a lower pressure (7 kg / cm2) was used, the contact time was 13 seconds and the catalyst time in the stream was 354 hours. The results are listed in the third column of Table 2. The PCE conversion was reduced to 67.8 as the pressure decreased, although the conversion of HCFC-123 / HCFC-123a increased to 31.0. These results suggest that high pressure is preferred for the single-stage process. TABLE 2
NON-RECYCLABLE PRODUCTS