MXPA98010756A - Azeotropo of hf and 123 - Google Patents

Abstract

The present invention relates to an azeotrope containing HF and 1233zd, as well as methods to separate this azeotrope from mixtures of HF and 1233zd, which are rich in HF or rich in 1233zd and methods for making use of azeotrope and separation methods to improve the procedures for preparing 1233zd, an intermediate used in the preparation of 245fa. The 245fa is a known foam blowing agent and refrigerate

Description

AZEOTROPO OF HF AND 1233zd BACKGROUND OF THE INVENTION This invention relates to an azeotrope containing hydrogen fluoride (hereinafter referred to as "HF") and 1,1,1-trifluoro-3-chloro-2-propene (hereinafter referred to as "1233zd") , to methods for separating this azeotrope and mixtures of HF and 1233zd, which are rich in HF or rich in 1233zd, and to methods for making use of azeotrope and separation methods to improve methods for preparing 1233zd, a known intermediate for the preparation of 1, 1,, 3,3-pentafluoropropane (hereinafter referred to as "245fa"), as taught, for example, in the US patent 5,616,189. The 245fa is known to be useful as a blowing agent for foam and coolant. A number of procedures in the prior art make 245fa by making the intermediary 1233zd first. For example 1233zd can be made through the fluorination of 1,1,1,3,3-pentachloropopane ("240fa") or the fluorination of 1,1,3,3-tetrachloro-2-propene (hereinafter referred to as as "1230za"). The 1230az is of special interest as a starting material, since it has been shown that it readily performs fluorination in the liquid phase without a catalyst, as taught in the patent application of E.U.A. co-pending series No. 3523, filed on January 27, 1998. Intermediary 1233zd can then be fluorinated directly or through other intermediaries to make 245fa. One of the problems associated with the 1233zd intermediate, however, is that it has the same boiling point (20 ° C) as HF, presenting a problem of how to recover enough HF to make the procedure economical. Processes of heterogeneously catalyzed gas phase can also be used to fluorinate 240fa or 1230za to 1233zd, as described, for example, in the application WO 97/24307 and the patent application of E.U.A. Copendent 08 / 980,746, filed on 1st. December 1997. A major problem associated with gas phase reactions, however, is that the precursor compounds have high boiling points (179 ° C for 240fa and 149 ° C for 1230za) and low thermal stability at temperatures elevated. In addition, its decomposition can be catalyzed in the liquid phase through acids such as HF, which is a reactor feed. In this way, it could be useful to develop a procedure that can be used to reduce the volatility of the organic feed and thus prevent its thermal decomposition. In this application "distillation column" and "rectification column" are sometimes used interchangeably. In reality, however, a rectification column is a specific type of distillation column. In most distillation columns, the material to be distilled is fed to the middle of the column; below the feed point is referred to as the separation section and above the feed point is called the rectification section. In the present reference is made to a rectification column when the material is to be distilled instead of fed to the bottom of the "distillation column".

COMPENDIUM OF THE INVENTION Herein provided, among other things, is an azeotropic composition consisting essentially of HF and 1233zd; a method for separating HF from a mixture containing HF and 1233zd (and, optionally, hydrogen chloride or "HCl"), which is rich in HF relative to the azeotropic composition, the method comprising treating said mixture in a column of distillation (rectification) to obtain a distillate containing the azeotropic composition (and HCl, if any) and a relatively pure HF bottom product; a method to produce 1233zd, which comprises (a) contacting 1230za and HF in the liquid phase in a feed ratio of HF to 1230za, which is at least equal to the sum of the stoichiometric ratio of the feeds ( 3.0) and the azeotropic ratio of HF to 1233zd to create a reaction mixture containing HF, 1233zd, and HCl, said mixture is rich in HF with respect to the azeotropic composition of HF and 1233zd, and (b) treating the mixture of (a) in a distillation (rectification) column to obtain a distillate containing HCl and the azeotropic composition of HF and 1233zd and a product that accumulates in the background of relatively pure HF, said product that accumulates in the bottom is preferably recirculated to be used as part of the HF feed; a method for separating 1233zd from a mixture containing HF and 1233zd (and, optionally, 245fa and / or HCl), said mixture is 1233zd rich relative to the azeotropic composition, said method comprises treating the mixture in a distillation column for obtain a distillate containing the azeotropic composition of HF and 1233zd (and HCl, if any) and a relatively pure 1233zd background product (and a predominant amount of 245fa, if any); and a method for producing 1233zd, which comprises (a) contacting HF and a selected organic feed of 1230za and 240fa in the gas phase in a feed ratio of HF to organic feed, which is at least equal to the stoichiometric ratio of the feeds, but less than the sum of the stoichiometric ratio of feeds and the azeotropic ratio of HF to 1233zd to create a reaction mixture containing HF, 1233zd, and HCl (and optionally some 245fa), said mixture is rich in 1233zd relative to the azeotropic composition of HF and 1233zd, (b) treating the mixture of (a) in a distillation column to obtain a distillate containing HCl and the azeotropic composition of HF and 1233zd and a product that accumulates in the background with relatively pure 1233zd (and a predominant amount of either 245fa), and (c) recirculate the product that accumulates in the bottom to be used as part of organic food. A Each of the above procedures preferably is operated continuously.

DETAILED DESCRIPTION Hitherto an azeotrope of HF and 1233zd has been found, which can be used to remove an azeotrope of HF / 1233zd from a system that is rich in HF or to remove an azeotrope of HF / 1233zd from a stream of pure 1233zd, said methods of separation are particularly useful for solving the problems discussed above, which are associated with liquid phase and gas procedures to make 1233zd. It has been found that HF and 1233zd have a low boiling azeotrope (highly high volatility). This azeotropic composition (at 20 ° C and 50 ° C) is shown below in Table 1: TABLE 1 Moles of HF / Temperature Mol (° C) Pressure (kg / cm m) 1233zd in Azeóropo 20 2,038 2.90 50 5.413 2.33 The application of the use of a rectification column to separate an azeotrope of HF / 1233zd from a stream that is rich in HF, is particularly useful in relation to the liquid phase processes to produce 1233zd of 1230za in an HF rich medium, since that abstinence from oligomer formation requires the use of HF / 1230za feed ratios, which are in excess of the sum of the stoichiometric ratio (3.0) and the azeotropic ratio (HF / 1233zd), thus ensuring that the mixture Reaction HF / 1233zd / HCl resulting will be rich in HF relative to the azeotropic ratio of HF / 1233zd. In practice, this reaction mixture can be removed from the reactor as a gas and fed to the bottom of a rectification column, with the liquid residues that accumulate in the bottom containing the purified HF being recirculated to the reactor. The distillate (HCl and azeotrope HF / 1233zd) is removed in the upper part and can be treated through conventional means in a second distillation column to recover the HCl as vapors leaving the upper part and HF / 1233zd as residues that are accumulate in the background. Reactor temperatures between about 70 ° C and 120 ° C and rectifying column pressures between about 9,139 kg / cm 2m and 19,332 kg / cm 2m are typically employed. For example, the process can be carried out at a reactor temperature of 70-85 ° C and a rectification column pressure of 9,842 kg / cm2m, using a minimum feed ratio of HF / 1230zd of 5.4. The application of the use of a distillation column to separate an azeotrope of HF / 1233zd from a stream that is rich in 1233zd is particularly useful in relation to the gas phase processes to produce 1233zd of 240fa or 1230za, since the recirculation of 1233zd (boiling point only of 20 ° C), and any of 245fa that is formed (boiling point of approximately 14 ° C), to be used as part of the organic feed reduces the volatility of the organic volatility and helps in this way to avoid its thermal decomposition. In order to generate the reaction mixture rich in 1233zd, HF / organic feed ratios are used, which are an excess of the stoichiometric ratio, but lower than the sum of the stoichiometric ratio and the azeotropic ratio (HF / 1233zd) . The following two examples of this embodiment, wherein 130za or 240fa is fluorinated with HF in the gas phase to produce a reaction mixture containing HCl, HF, 1233zd, and optionally, 245fa, said reaction mixture is 1233zd rich relative to to the azeotropic ratio, the reaction mixture is distilled to obtain a distillate containing mainly the azeotrope HF / 1233zd and HCl and residues that accumulate in the bottom containing purified 1233zd and the predominant amount of either of 245fa formed is recirculated to be used as part of the food. In any case, the recirculation stream generally contains a recirculation molar ratio of 1233zd / 245fa to precursor 1230za or 240fa of between about 1 and 20, but preferably between about 3 and 8; the reaction temperature depends on the catalyst, but preferably it is on the scale of approximately 150-200 ° C; and the pressure of the distillation column is generally about 8,436-17,575 kg / cm2m (preferably 10,545-15,817 kg / cm m). A) When using 1230za as the feed, the system is operated so that the recirculation current contains about 3 moles of 1233zd and 0.8 moles of 245fa per mole of 1230za and the molar ratio of HF: 1230za is about 5.4, approximately 3.4 being required for the reaction at 1233zd and 245fa, with about 2 moles of HF being present in the reaction mixture so that the reaction mixture is 1233zd rich in relation to the azeotropic ratio. The reaction mixture effluent can be fed to the distillation column as a liquid, gas or mixed phase. The distillation column removes HCl and the azeotrope 1233zd / HF as leaving vapors from the upper part (for conventional separation as in the liquid phase system) and recirculates 1233zd and 245fa in the aforementioned ratios. B) By using 240fa as the feed, the system is operated so that the recirculation stream contains about 5 moles of 1233zd and 0.8 moles of 245fa per mole of 240za and the molar ratio of HF: 240za is about 5.5, about 3.4 being required for the reaction at 1233zd and 245fa, with about 2.1 moles of HF being present in the reaction mixture so that the reaction mixture is 1233zd rich in terms of the azeotropic ratio. The reaction mixture effluent can be fed to the distillation column as a liquid, gas or mixed phase. The distillation column removes HCl and the azeotrope 1233zd / HF as vapors projecting from the upper part (for conventional separation as in the liquid phase system) and recirculations 1233zd and 245fa in the aforementioned ratios.

Claims (11)

1. An azeotropic composition consisting essentially of hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene.

2. A method for separating hydrogen chloride from a mixture containing hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene, said mixture is rich in hydrogen fluoride with respect to the composition azeotropic hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene, the method comprises treating said mixture in a distillation column to obtain a distillate containing the hydrogen fluoride azeotropic composition and 1.1. , 1-trifluoro-3-chloro-2-propene and a waste product that accumulate in the background of relatively pure hydrogen fluoride.

3. A method according to claim 2, wherein the mixture also contains hydrogen chloride and wherein said hydrogen chloride also becomes part of said distillate.

4. A method according to claim 3, further characterized in that it comprises treating the distillate in a second distillation column to obtain a second distillate containing purified hydrogen chloride and a residue product that accumulates in the bottom containing the azeotropic composition of hydrogen fluoride and 1, 1, 1-trifluoro-3-chloro-2-propene.

5. A method for producing 1,1,1-trifluoro-3-chloro-2-propene, which comprises (a) contacting 1, 1, 3,3-tetrachloro-2-propene and hydrogen fluoride in the liquid phase in a feed ratio of hydrogen fluoride to 1, 1, 3,3-tetrachloro-2-propene which is at least equal to the sum of the stoichiometric ratio of the feeds and the azeotropic ratio of the fluoride of hydrogen to 1, 1, 1-trifluoro-3-chloro-2-propene to create a reaction mixture containing hydrogen fluoride, 1,1,1-trifluoro-3-chloro-2-propene and hydrogen chloride, said mixture is rich in hydrogen fluoride with respect to the azeotropic composition of hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene; and (b) treating said mixture in a distillation column to obtain a distillate containing hydrogen chloride and the azeotropic composition of hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene and a waste product. that accumulate in the bottom of purified hydrogen fluoride.

6. A method according to claim 5, wherein the product that accumulates in the bottom is recirculated to be used as part of the hydrogen fluoride feed. 7.- A method to separate 1, 1, 1-trifluoro-3-chloro-2-propene from a mixture containing hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene, said mixture is rich in 1, 1, 1-trifluoro-3-chloro-2-propene relative to the azeotropic composition of hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene, the method comprises treating said mixture in a distillation column to obtain a distillate containing the azeotropic composition and a product that accumulates on the bottom of purified 1,1-trifluoro-3-chloro-2-propene. 8. A method according to claim 7, wherein the mixture also contains 1, 1, 1, 3,3-pentafluoropropane and wherein said 1,1,1,3-pentafluoropropane is also part of the product that it accumulates in the background. 9. A method according to claim 8, wherein the mixture also contains HCl and wherein said HCl becomes part of said distillate. 10. A method according to claim 9, characterized in that it further comprises treating the distillate in a second distillation column to obtain a second distillate containing purified hydrogen chloride. 11. A method to produce 1, 1, 1-trifluoro-3-cioro-2-propene, which comprises (a) contacting with hydrogen fluoride and an organic feed selected from 1,1,3,3-tetrachlor -2-propene and 1, 1, 1, 3,3-pentachloropropane in the gas phase in a feed ratio of hydrogen fluoride to organic feed, which is at least equal to the stoichiometric ratio of the feeds, but less than the sum of the stoichiometric ratio of feeds and the azeotropic ratio of hydrogen fluoride to 1,1,1-trifluoro-3-chloro-2 -propene to create a reaction mixture containing hydrogen fluoride, 1, 1, 1-trifluoro-3-chloro-2-propene and hydrogen chloride, the mixture is rich in 1, 1, 1-trifluoro-3-chloro- 2-propene in relation to the azeotropic composition of hydrogen fluoride and 1,1,1-trifluoro-3-chloro-2-propene; (b) treating said mixture in a distillation column to obtain a distillate containing hydrogen chloride and the azeotropic composition and a product that accumulates on the bottom of purified 1,1,1-trifluoro-3-chloro-2-propene; and (c) recirculate the product that accumulates in the bottom to be used as part of the organic food.