MXPA98010077A - Preparation of 24 - Google Patents

Abstract

A process for the preparation of 245fa is provided, where 1233zd is first fluorinated at 1234ze, followed by fluorination from 1234ze to 245fa. It is known that 245fa is an aerating agent of foam and refrigerate

Description

PREPARATION OF 245fa BACKGROUND OF THE INVENTION This invention relates to the preparation of 1,1,1,3-pentafluoropropane ("245fa") from 1,1,1trifluoro-3-chloro-2-propene ("1233zd"). "), particularly to processes wherein said 1233zd is first converted to 1, 1, 1, 3-tetrafluoro-2-propene (" 1234ze "), followed by conversion of 1234ze to 245fa. It is known that 1, 1, 1, 3,3-pentafluoropropane has utility as a foam and coolant aerating agent. U.S. Patent 5,616,819 describes the conversion of 1233zd to 245fa in one step via the reaction with excess hydrogen fluoride, but the separation of the resulting reaction mixture is tedious because 245fa forms azeotropes with 1233zd and excess HF. Thus, the '819 patent teaches the use of organic salts to assist in the recovery of 245fa, the three compounds having similar boiling points. What is desired is a way to produce 245fa easily recoverable.

BRIEF DESCRIPTION OF THE INVENTION A process for preparing easily recoverable 245fa is provided, said process comprising (a) contacting 1233zd with hydrogen fluoride (hereinafter referred to by convenience as "HF") in a first low reaction zone. conditions sufficient to produce 1234ze, and (b) contacting said 1234ze with HF in a second reaction zone under conditions sufficient to produce 245fa. Because 1234ze readily reacts with HF, it is not necessary to use large molar excesses of HF in step (b). The reaction mixture of step (a) contains mainly 1234ze, 245fa and hydrogen chloride ("HCI"), together with unreacted 1233zd and HF. The 245fa, 1233zd and HF can be separated from this mixture and recycled to the first reaction zone, such as by distillation to separate the reaction in streams containing (i) 245fa, 1233zd and HF and (ii) 1234ze and HCl. The 1234ze and HCl in the second stream (ii) can be separated by methods known in the art, such as by a second distillation or by absorption, wherein the HCl is removed, for example, by absorption in water or caustic solution.

DETAILED DESCRIPTION A process for producing 245fa easily recoverable by converting 1233zd to 1234ze, followed by conversion of 1234ze to 245fa has now been discovered. Intermediary 1234ze has a boiling point 35 ° C lower than that of 1233zd, so that it can be easily separated from 245fa by distillation. In addition, the 1234ze reacts easily with HF, so that large excesses of HF are not required in the second step, simplifying recovery again. The 1233zd starting material can be prepared by known processes, such as 1, 1, 3,3-tetrachloro-2-propene fluorination ("1230za") as shown in U.S. Patent 5,616,819.

The first step of the process involves contacting 1233zd with HF in a first reaction zone under conditions sufficient to produce 1234ze, such as by the gas phase, the catalyzed fluorination of 1233zd to produce a mixture whose main components are 1234ze, 245fa, HF, HCl and 1233zd. The molar ratio HF: 1233zd is usually from about 0.5: 1 to 40: 1, but is preferably about 1: 1 to intensify the conversion and not more than about 10: 1 in order to produce lower levels of downstream HF. for recovery. Temperatures of from about 250 ° C to about 600 ° C, preferably from about 300 ° C to about 500 ° C are usually used. The pressures are usually from about 0 to 28.12 kg / cm2, preferably from about 1 .406-14.06 kg / cm2. A variety of fluorination catalysts can be used, such as aluminum fluoride or a chromium-based catalyst (such as chromium oxide, Cr2O3), said chromium-based catalyst is either unsupported or supported on fluoridated alumina or activated carbon, only the chromium catalyst being used or in the presence of a co-catalyst, such as an alkali metal (eg, sodium, potassium or lithium), alkaline earth metal (eg, calcium, barium or magnesium), zinc, manganese , cobalt or nickel. Two such preferred chromium catalysts are chromium oxide and chromium / nickel in fluoridated alumina, the preparation of this latter catalyst is shown, for example, in European patent 486333. Chromium-based catalysts are preferably activated before use, usually by a process wherein the catalyst bed is heated to about 370-380 ° C, (usually with a continuous flow of nitrogen), after which a mixture of approximately equal volumes of HF and air or nitrogen is fed (preferably nitrogen) on the catalyst bed for approximately 18 hours. An oxygen or chlorine co-feed can also be used to extend the life of the catalyst, usually in an amount from about 0.005 to about 0.20 mole of chlorine or oxygen per mole of organic in the feed, oxygen being introduced as an oxygen-containing gas such as air, oxygen, or a mixture of oxygen / nitrogen. The contact times (catalyst volume divided by the total flow rate of reactants and co-feeds at the process operating temperature and pressure) are usually from about 1 to about 250 seconds, more usually from about 1 to about 120 seconds. The 1234ze produced in the first reaction zone is preferably separated from the reaction mixture and then contacted with HF in a second reaction zone under conditions sufficient to produce 245fa. One way to perform the separation is to subject the reaction mixture of the first reaction zone to two distillations, with the first distillation serving to separate the lower boiling point 1234ze and HCl (taken at the top of the column) from the 245fa, 1233zd, HF and any other heavy (taken at the bottom of the column), and the second distillation used to separate the lower boiling point HCl (removed at the top of the column) from the 1234ze (removed in the lower column and fed to the second reaction zone). Preferably, the lower portions of the first column are then recycled to the first reaction zone, where the 1233zd and 245fa can be reacted to produce 1234ze. The fluorination of 1234ze to 245fa in the second reaction zone can be performed using a gas phase, liquid phase or mixed phase, catalyzed system to produce a mixture whose main components are 245fa, 1234ze and HF. Since 1234ze reacts easily with HF, the molar ratio HF: 1234ze is usually from about 0.1: 1 to about 3: 1, preferably from about 1: 1 to about 1.5: 1, in order to avoid a concentration of HF in the stream of product in excess of the HF / 245fa azeotrope. Temperatures from about 30 ° C to about 300 ° C are normally used, preferably from about 50 ° C to about 200 ° C. The pressures are usually from about 0 to 21.09 kg / cm2, preferably from about 2.109-14.06 kg / cm2. A variety of fluorination catalysts can be used, such as supported Lewis acids, including the oxides or salts (preferably chlorides) of Sb (V), Ti (IV), Sn (IV), Ta (V) or Nb (V) in activated carbon, the chromium-based catalysts discussed above or compounds containing sulfonic acid, such as trifluoromethanesulfonic acid supported on activated carbon or activated alumina. If the process is run as a gas phase reaction at a low temperature / up to about 130 ° C), sulfonic acid or supported Lewis acid catalysts are preferred. If the gas phase process is carried out at a higher temperature, then chromium-based catalysts are preferred. If the process is run as a liquid phase reaction, sulfonic acid or Lewis acid catalysts are preferred. Each type of catalyst will have its own activation procedure before use. The activation of the chromium-based catalysts is as discussed above. The supported sulfonic acids and Lewis acids have a lower activation temperature, usually about 50 ° C, using a low feed of HF diluted with nitrogen to convert the metal chloride to metal fluoride. The contact times for the gas phase reaction (catalyst volume divided by the total flow rate of reactants and co-feeds) are usually from about 1 to about 250 seconds, more typically from about 1 to about 250 seconds, more usually from about 1 to about 120 seconds, while the residence time for the liquid phase reaction is usually from about 1 to about 400 minutes, more usually from about 10 to about 120 minutes. The 245fa (boiling point 15 ° C) can then be recovered from the reaction mixture by conventional techniques, such as distillation, the lower boiling point 1234ze (boiling point -16 ° C) and any azeotrope of HF / 245fa coming from above, where it can be recycled to the reactor. The separation of any azeotrope from HF / 245fa can be conducted as shown, for example, in the worldwide patent application WO97 / 27163. The practice of the invention is illustrated in more detail in the following non-limiting examples.

EXAMPLE 1 . Fluorination of 1233zd to 1234ze with chromium oxide catalyst (unsupported): The chromium oxide catalyst (Cr2O3) was activated at 380 ° C when a mixture of HF (124 cc / min) and air (100 cc / min. ) for 18 hours. 1233zd and HF were then fed, in a molar ratio of HF: 1233zd of 10.6: 1, to the reactor at 365 ° C and 2.67 kg / cm2 for a contact time of 3.9 seconds, resulting in 54.8% conversion of 1233zd, being the selectivity 58.3% for 1234ze and 36.6% for 245fa. In runs subsequent to a molar ratio of HF: 1233zd of 21 .1: 1, while maintaining other parameters equal, essentially the same results were obtained. Still further tests indicated that higher pressure (10.82 kg / cm2) and longer contact time (14 seconds) increased the conversion to approximately 74%, while lower pressure (1.96 kg / cm2) and shorter contact time (3.5 seconds) ) improved the selectivity for 1234ze to approximately 61%.

EX EMPLO 2. Fluorination of 1233zd to 1234ze using supported chromium / nickel catalyst: The catalyst for this example was a mixture of chromium and nickel oxides supported on fluoridated alumina (prepared as in European patent 486333), said catalyst was activated at 380 ° C by coalescing a mixture of HF (123 cc / min) and nitrogen (100 cc / min) for 18 hours. 1233zd and HF were then fed, in varying molar proportions ("mr" s), together with an air co-containment containing 0.03 moles of oxygen per mole of organic (1233zd), on the activated catalyst under the conditions, and with the results, exposed below: Run # 1 2 3 4 5 6 Temperature (° C) 300 354 354 353 354 404 Pressure (kg / cm2) 10.54 1 1 .03 10.96 3.02 3.02 10.75 HF: 1233zd (m.r.) 2.9 2.6 5.3 2.6 5.2 2.6 Contact time (seconds) 18.5 9.4 9.5 1 .8 4.7 17.1 Conversion (%) 43.1 37.3 51 .0 30.5 42.6 30.8 Selectivity for 1234ze (%) 13.2 28.1 24.1 45.0 43.2 35.9 Selectivity for 245fa (%) 86.9 71.8 75.8 54.9 56.7 64.0 EXAMPLE 3. Gas Phase Fluorination of 1234ze to 245fa with chromium oxide catalyst (unsupported) Using the same catalyst and activation procedures as in EXAMPLE 1, 1234ze and HF were fed in a molar ratio of HF: 1234ze of 1.6: 1, to a reactor at a temperature of 204 ° C and 10.61 kg / cm2 for a contact time of 77 seconds, resulting in 98.9% conversion of 1234ze to 245fa and 79.8% conversion of HF.

EXAMPLE 4. Gas Phase Fluorination of 1234ze to 245fa using antimony chloride catalyst supported on activated carbon (SbCls / C): 38 grams of SbCls / C were activated at 50 ° C by coalescing a mixture of HF (123 cc / min) and nitrogen (100 cc / min) for 18 hours. Then HF and 1234ze, in a molar ratio of 1.04: 1, were fed to the reactor under the conditions and with the results set forth below: Run # 1 2 3 4 Temperature (° C) 123 128 119 115 Pressure (kg / cm2) 10.33 10.33 10.33 10.40 Contact time (seconds) 50.7 49.9 51.1 51.8 Conversion of 1234ze (%) 99.7 97.6 95.3 95.1 Selectivity for 245fa (%) 100 100 100 100

Claims (6)

1. A process for preparing 1,1,1,3,3-pentafluoropropane, which comprises (a) contacting 1,1,1-trifluoro-3-chloro-2-propene with hydrogen fluoride in a first reaction zone under conditions sufficient to produce 1,1,1,3-tetrafluoro-2-propene; and (b) contacting said 1,1,1,3-tetrafluoro-2-propene with hydrogen fluoride in a second reaction zone under conditions sufficient to produce 1,1,1,3,3-pentafluoropropane.

2. A process as in claim 1, wherein the molar ratio of hydrogen fluoride to 1,1,1,3-tetrafluoro-2-propene in step (b) is at most about 3 to 1.

3. A process for preparing 1,1,1,3,3-pentafluoropropane, which comprises (a) contacting 1,1,1-trifluoro-3-chloro-2-propene with hydrogen fluoride in a first low reaction zone conditions sufficient to produce a reaction mixture containing 1,1,1,3-tetrafluoro-2-propene, 1,1,1,3,3-pentafluoropropane, and hydrogen chloride, together with 1,1,1-trifluoro- Unreacted 3-chloro-2-propene and hydrogen fluoride; and (b) separating the 1,1,1,3-tetrafluoro-2-propene from said reaction mixture and contacting it with hydrogen fluoride in a second reaction zone under conditions sufficient to produce 1,1,1, 3. , 3-pentaf luoropropane.

4. A process as in claim 3, wherein the 1,1,1,3,3-pentafluoropropane, 1,1,1-trifluoro-3-chloro-2-propene and hydrogen fluoride are separated from the mixture of reaction in step (a) and recycled to the first reaction zone.

5. A process as in claim 3, wherein the reaction mixture of step (a) is subjected to a first distillation to separate the reaction mixture in a first stream containing the 1,1,1,3,3-pentafluoropropane , 1,1,1-trifluoro-3-chloro-2-propene and hydrogen fluoride and a second stream containing 1,1,1,3-tetrafluoro-2-propene and hydrogen chloride, the chloride being then separated from hydrogen in the second stream of 1234ze via absorption or a second distillation.

6. A process for preparing 1,1,1,3-tetrafluoro-2-propene, which comprises (a) contacting 1,1,1-trifluoro-3-chloro-2-propene with hydrogen fluoride in a first reaction zone under conditions sufficient to produce 1,1,1,3-tetrafluoro-2-propene; and (b) separating 1,1,1, -3-tetrafluoro-2-propene from the reaction mixture resulting from step (a).