GB2329386A

GB2329386A - Synthesis of 1,1,1,3,3-Pentafluoropropane

Info

Publication number: GB2329386A
Application number: GB9820753A
Authority: GB
Inventors: Philippe Bonnett; Laurent Wendlinger
Original assignee: Elf Atochem SA
Current assignee: Arkema France SA
Priority date: 1997-09-23
Filing date: 1998-09-23
Publication date: 1999-03-24
Also published as: NL1010169C2; KR19990030026A; CA2245152A1; IT1302243B1; AU8614998A; JPH11158089A; BE1011954A3; ITMI982041A1; CN1217313A; GB9820753D0; FR2768727A1; DE19843681A1

Abstract

The invention relates to a process for the production of 1,1,1,3,3-pentafluoropropane, which process comprises reacting hydrogen fluoride with, in particular, 1,1,1,3,3-pentachloro-propane in the liquid phase in the presence of a titanium-based catalyst. The use of a titanium-based catalyst makes it possible to avoid the problems of corrosion which are generated by antimony-based catalysts.

Description

SYNTHESIS OF 1,1,1,3 ,3-PENTAFLUOROPROPANE The present invention relates to the synthesis of 1,1,1,3,3-pentafluoropropane.

Due to the depletion of the ozone layer, limitation of the production of fully halogenated chlorofluorocarbons (CFCs) was planned from 1986 (Montreal protocol) and an update (Copenhagen convention in 1992) finalized the principle of phasing out these products completely by the end of the year 1995.

Research to find substitutes for these compounds was first focused on products containing hydrogen atoms (HCFCs), and then on products no longer containing chlorine: hydrofluorocarbons. Among these, there seems to be a growing interest in C3 compounds.

1,1,1,3,3-Pentafluoropropane, known by the reference F245fa, is not detrimental to the ozone layer. It therefore belongs to the class of potential substitutes for CFCs, and its use has been mentioned in various patent applications, in particular as an expansion agent for foam (JP 5239251), as a propellant gas and cleaning solvent for the electronics industry (DD 298419) and, lastly, as a heat-exchange fluid (JP 2272086).

1,1,1,3,3-Pentafluoropropane can be prepared in different ways, in particular: - by catalytic hydrogenation of 1,1,3,3,3pentafluoro-1-propene (Knunyants et al., Izvest. Akad.

Nauk. S.S.S.R., Ctdel. Khim. Nauk. 1960, 1412-1418; C.A. 55:349c and Kinet. Katal. 1967, 8(6), 1290-1299; C.A. 69:3510n), - by hydrogenolysis of 1,2,2-trichloro 1,1,3,3,3-pentafluoropropane (US Patent 2942036), - by reacting tetrahydrofuran with cobalt trifluoride (Burdon et al., J. Chem. Soc. C,1969, 13, 1739-1746).

Since these processes are not industrially viable, it has recently been proposed, in EP-A-703 205 and WO-A-9601797, to produce 1,1,1,3,3pentafluoropropane by reacting hydrogen fluoride with 1,1,1,3,3-pentachloropropane or a partially fluorinated derivative of 1,1,1,3,3-penta-chloropropane, in the liquid phase and in the presence of a catalyst.

1,1,1,3,3-Pentachloropropane, used as the starting product, can be prepared with ease in a single step by reacting carbon tetrachloride with vinyl chloride, these being two widely available industrial products.

The term "partially fluorinated derivative of 1,1,1,3,3-pentachloropropane" is here intended to mean intermediate reaction compounds such as 3-chloro1,1,1,3-tetrafluoropropane (F244), 3,3-dichloro-1,1,1- trifluoropropane (F243), l-chloro-3,3,3-trifluoropropene (F1233zd), 1,1,3,3-tetrachloro-1-fluoropropane (F241), 1,3,3-trichloro-1,1-difluoropropane (F242), 1,3,3-trichloro-3-fluoropropene (F1231zd), 1,3 dichloro-3, 3-difluoropropene (F1232zd) and 1,3,3,3tetrafluoropropene (F1234ze).

Although these two publications generally indicate that the catalyst may be selected from the metal derivatives, in particular those of the metals belonging to main groups IIIa, IVa and Va and to sub-groups IVb, Vb and VIb, they recommend preferential use of antimony derivatives and, more particularly, antimony pentahalides which lead to a high degree of conversion of the 1,1,1,3,3-pentachloropropane and to a high selectivity with respect to 1,1,1,3,3-pentafluoropropane.

All of the examples in these two publications were carried out using an antimony pentahalide (SbCls or SbF5) as catalyst. Unfortunately, the use of these catalysts is accompanied by significant corrosion phenomena, which makes it difficult to use a process of this type industrially.

Furthermore, W0-A-97/08117 describes a process for the two-step preparation of a fluorinated aliphatic compound from a chlorinated olefin, which employs a chlorofluoro-olefin as intermediate. Thus, Example 1 of this patent application describes the preparation of F245fa from 1,1,3,3-tetrachloro-1propene, also referred to as F1230za, necessarily proceeding via 1-chloro-3,3,3-trifluoropropene as intermediate. This document teaches that only the step of converting the chlorofluoro-olefin intermediate needs to be catalyzed. The catalyst envisaged for this step is a fluoride of Sb, Sn, Ti and, more particularly, a mixture of Sb(V) and Ti(IV). This process is, however, difficult to employ industrially.

Titanium-based compounds such as titanium tetrachloride have been used as liquid-phase fluorination catalysts for the fluorination of acetylene to form 1,1-difluoroethane (US Patent 2 830 100), the fluorination of trichloroethylene to form 1,1,2-trichloro-l-fluoroethane (US Patent 4 383 128) and the synthesis of l-chloro-2-fluoroethane from vinyl chloride (FR Patent 1 534 403). A.E. Feiring (J. of Fluorine Chemistry 13 (1979) 7-18) has studied the addition of HF to tetrachloroethylene catalyzed by TiC1,. This titanium compound has also been used as a catalyst for the fluorination reaction of vinylidene chloride to form l,l-dichloro-l-fluoroethane (EP-A378 942), that of trifluoroethylene to form 1,1,1,2tetrafluoroethane (EP-A-574 077) and that of 1,1,1,3,3,3-hexachloropropane to form 1-chloro 1,1,3,3,3-pentafluoropropane (WO-A-95/04022). Certain synergy effects have also been demonstrated between TiCl and SbCl2 (US Patent 5 202 509), with a nitrated solvent or a sulphone for the synthesis of 1,1dichloro-1-fluoroethane from vinylidene chloride (WO-A- 94/13607) or, recently, with SbCls for the fluorination of trichloroethylene to form F134a (J. Chem. Soc. Chem.

Communications 1994 (7) 867).

A literature survey shows that TiCl, is most often used to catalyze the addition of HF to a double bond, and rarely for Cl-F exchange on a saturated substrate.

It has now unexpectedly been found that TiCl, and, more generally, titanium-based compounds are good catalysts for the fluorination of 1,1,1,3,3pentachloropropane, 1,1,3,3-tetrachloro-l-propene (F1230za) or 1,3,3,3-tetrachloro-l-propene (F1230zd) to form 1,1,1,3,3-pentafluoropropane. They exhibit a high degree of activity without the drawbacks generated by antimony-based catalysts in terms of corrosion.

Furthermore, unlike antimony, titanium catalysts are not deactivated by reduction and practically do not lead to the by-production of C6 heavy compounds, which cannot be recycled to give the desired final product (F245fa).

According to the present invention, there is provided a process for the production of 1,1,1,3, 3-pentafluoropropane (F245fa), which process comprises reacting hydrogen fluoride with a compound A selected from 1,1,1,3,3-pentachloropropane (F240fa), a partially fluorinated derivative of F240fa, 1,1,3,3,tetrachloro-1-propene (F1230za) and 1,3,3,3tetrachloro-l-propene (F1230zd) in the liquid phase, and using a titanium-based compound as catalyst.

F1230zd and za can be prepared by de-hydrochloration of F240fa at a temperature of between 20 and 100"C, in the presence of a Lewis acid such as Alma, All?, Fecal3 TiCl, as catalyst. The partially fluorinated derivatives of 1,1,1,3,3-pentachloropropane can be prepared by reacting 240fa with HF in the presence of a fluorination catalyst, for example based on Sb.

As titanium-based compounds, use is preferably made of titanium halides, such as chlorides, fluorides or chlorofluorides, but use may also be made of oxides or oxyhalides. Titanium tetrachloride has proved particularly advantageous.

The process according to the invention may be carried out in a manner known per se, in batch, semi-batch or continuous mode.

In batch mode, the procedure is carried out in a stirred autoclave in which the reactants are introduced prior to the start of the reaction; the pressure in the autoclave is then the autogenous pressure and therefore changes as the reaction progresses.

When the process is carried out in a semi-batch procedure, the equipment used may consist of an autoclave, on top of which is a simple condenser, or on top of which there is a return column and a reflux condenser, also equipped with a pressure-control valve.

As before, all of the reactants are introduced into the autoclave prior to the start of the reaction, but the reaction products with low boiling point (in particular F245fa) are generally extracted continuously during the reaction.

When the process according to the invention is carried out in continuous mode, use may be made of the same equipment as in semi-batch mode but the reactants are introduced continuously, preferably in a medium comprising a solution of catalyst in HF.

The amount of catalyst to be employed can vary within wide limits. It is generally between 0.0005 and 0.1 mol, preferably between 0.001 and 0.05 mol, per mole of HF. In any case, it is preferable to work with an amount of catalyst less than its solubility limit in HF.

Since the catalyst according to the invention does not generate corrosion, the amount of hydrogen fluoride to be used in batch or semi-batch mode is generally between 0.5 and 50 mol per mole of compound A, e.g. F240fa and, preferably, between 2 and 20 mol.

In the case of the continuous mode, it is preferable to operate by injecting the reactants into a medium consisting of HF.

The temperature for carrying out the process according to the invention may generally be between 30 and 180"C. It is preferably selected between 70 and 150 C, and, more particularly, between 100 and 140"C.

When the procedure is carried out in semi-batch or continuous mode, the working pressure is selected so as to keep the reaction medium in the liquid phase. It generally lies between 5 and 50 bar and, preferably between 10 and 40 bar.

The temperature of the condenser is controlled according to the amount and nature of the products that may be discharged during the reaction. It is generally between -50 and 150"C and, preferably, between 0 and 100"C.

The Examples which follow further illustrate the invention. In the Examples the percentages indicated are molar percentages.

ExamPle 1 The procedure adopted is the semi-batch mode described above, in a stirred, 1 litre autoclave made of stainless steel 316L, containing a small sample (mass: 5g; area: 760 mm) made of stainless steel 316L, on top of which there is a condenser supplied with industrial water at 170C. 228 g of HF (11.4 mol) and 11.8 g of TiCl, (0.062 mol) were introduced into this autoclave. The autoclave was then heated to llO"C using an oil bath flowing in a double jacket. After the temperature of the reaction medium had stabilized, 19 g/hour of F240fa (0.09 mol/h) was supplied continuously, and some of the most volatile products were degassed continuously by means of a pressurecontrol valve set at 20 bar. After passing through a water bubbler and then a drier, these products were collected in a stainless steel trap cooled with liquid nitrogen.

After 5 hours of reaction, the operation was terminated and the trapped gasses and the reaction medium were analyzed by gas chromatography. This analysis indicates that the conversion of F240fa amounts to 88% with the following selectivities: - F245fa : 11% - F244 : 36% - F243 : 35% - F1233zd: 18E The percentages indicated are molar percentages.

After separation of the F245fa, the unconverted F240fa and the partially fluorinated intermediates F244, F243 and F1233zd can be recycled to the reactor.

Furthermore, weighing the stainless steel 316L sample kept in the medium throughout the reaction does not demonstrate any difference in weight from its initial weight. No corrosion was therefore observed.

Example 2 The procedure was carried out using the same operating method, the same equipment and the same conditions as those described in Example 1.

245g of HF (12.25 mol) and 12.5g of TiClw (0.066 mol) were introduced into the continuously supplied autoclave. After heating the reaction medium to 1l00C and stabilizing the temperature, 18 g/hour of F1230za (0.1 mol/h) was supplied. Some of the most volatile products were degassed continuously by means of a pressure-control valve set at 20 bar.

After passing through a water bubbler and then a drier, these products were collected in a stainless steel trap cooled with liquid nitrogen.

After 5 hours of reaction, the operation was terminated and the trapped gasses and the reaction medium were analyzed by gas chromatography. This analysis indicates that the conversion of F1230za amounts to 90% with the following selectivities: - F245fa : 8% - F244 : 25% - F243 : 25% - F1233zd: 39% - heavy components : 3% The percentages indicated are molar percentages.

After separation of the F245fa, the unconverted F1230za and the partially fluorinated intermediates F244, F243 and F1233zd can be recycled to the reactor.

Claims

1. Process for the production of 1,1,1,3,3-pentafluoropropane, which process comprises reacting hydrogen fluoride with a compound A selected from 1,1,1,3,3-pentachloropropane (F240fa), a partially fluorinated derivative of F240fa, 1,1,3,3,-tetrachloro1-propene (F1230za) and 1,3,3,3-tetrachloro-l-propene (F1230zd) in the liquid phase, and using a titaniumbased compound as catalyst.

2. Process according to Claim 1, in which the compound A is F240fa or a partially fluorinated derivative of F240fa.

3. Process according to Claim 1, in which the compound A is F1230za or 1,3,3,3-tetrachloro1-propene (F1230zd).

4. Process according to any one of Claims 1 to 3, in which the titanium-based compound is a halide, an oxide or an oxyhalide of titanium.

5. Process according to Claim 4, in which the titanium-based compound is titanium tetrachloride.

6. Process according to any one of Claims 1 to 5, in which the HF/compound A molar ratio is between 0.5 and 50.

7. Process according to Claim 6, in which the HF/compound A molar ratio is between 2 and 20.

8. Process according to any one of Claims 1 to 7, in which the procedure is carried out at a temperature of between 30 and 1800C.

9. Process according to Claim 8, in which the procedure is carried out at a temperature of between 70 and 150"C.

10. Process according to Claim 9, in which the procedure is carried out at a temperature of between 100 and 140"C.

11. Process according to any one of Claims 1 to 10, in which from 0.0005 to 0.1 mol of catalyst is used per mole of HF.

12. Process according to Claim 11, in which from 0.001 to 0.05 mol of catalyst is used per mole of HF.

13. Process for the production of 1,1,1,3,3pentafluoropropane substantially as described in Example 1 or 2.

14. 1,1,1,3,3-Pentafluoropropane obtained by the process claimed in any one of Claims 1 to 13.