Process for the preparation of fluorine containing...

Details Process for the preparation of fluorine containing... Process for the preparation of fluorine containing...

1998-04-09

2001-02-13

Peselev, Elli (Department: 1623)

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

C570S166000, C570S168000

Reexamination Certificate

active

06187976

ABSTRACT:

FIELD OF THE INVENTION
This invention is related to the preparation of fluorine containing hydrohalocarbons. Specifically, it relates to the manufacture of 1-chloro-1,1,3,3,3-pentafluoropropane (referred to in the art as HCFC-235fa) in the presence of a fluorination catalyst either in the liquid phase or vapor phase. HCFC-235fa is useful as an intermediate in the production of 1,1,1,3,3-pentafluoropropane (referred to in the art as HFC-245fa).
The invention also relates to a process for the preparation of 1,1,1,3,3-pentafluoropropane comprising the step of producing 1-chloro-1,1,3,3,3-pentafluoropropane by reaction of CCl
3
CH
2
CCl
3
with hydrogen fluoride in the presence of a fluorination catalyst either in the liquid phase or the vapor phase.
BACKGROUND OF INVENTION
Fluorine containing hydrohalocarbons are of current interest due to their potential to replace ozone depleting chlorofluorocarbons, which are used in a variety of applications including refrigerants, propellants, blowing agents, and solvents. Both HCFC-235fa and HFC-245fa are known to be useful as blowing agents. HFC-245fa has physical properties, including a boiling point of about 14° C., that makes it particularly attractive as a blowing agent, refrigerant or propellant. Its ability to function in a manner similar to CFC-11 (CCl
3
F, b.p. 24° C.), a well known aerosol propellant at the time, was noted by Smith and Woolf in U.S. Pat. No. 2,942,036 (1960). European Patent Application EP 381 986 also states (using a generic formula) that CF
3
CH
2
CF
2
H may be used as a propellant or blowing agent. The use of HFC-245fa as a heat transfer agent is also mentioned in JP 02/272,086 (Chem. Abstr. 1991, 114, 125031q).
Previously, CF
3
CH
2
CF
2
Cl has been prepared by a liquid phase reaction of 1,1,1,3,3,3-hexachloropropane with HF in the presence of a catalyst, as disclosed in EP 0 522 639.
Commonly assigned U.S. Pat. No. 5,728,904 discloses the preparation CF
3
CH
2
CF
2
Cl by fluorination of CCl
3
CH
2
CCl
3
with HF in the presence of either TiCl
4
or SnCl
4
catalysts, followed by reduction to HFC-245fa.
The preparation of CF
3
CH
2
CF
2
Cl by the BF
3
-catalyzed addition of HF to CF
3
CH═CFCl is also known (R. C. Arnold, U.S. Pat. No. 2,560,838; 1951). The source of CF
3
CH═CFCl was not disclosed.
HFC-245fa was first made by the reduction of CF
3
CCl
2
CF
2
Cl over a palladium catalyst (Smith and Woolf, U.S. Pat. No. 2,942,036, 1960). Materials exiting the reaction zone include CF
3
CH
2
CHF
2
, CF
3
CH═CF
2
, CF
3
CCl═CF
2
, and unreacted starting material. The desired CF
3
CH
2
CF
2
H was formed in yields up to about 60%, but the source of the starting material was not disclosed.
Reduction of 1,1,1,3,3-pentafluoropropene was disclosed by Knunyants et al. (Chem. Abstr., 1961, 55, 349f). The yield of pentafluoropropane was 70%.
Burdon et al., J. Chem. Soc., C, 1969, 1739 disclose the formation of CF
3
CH
2
CF
2
H, in low yield, during the elemental fluorination of tetrahydrofuran.
Commonly assigned U.S. Pat. No. 5,574,192 discloses the fluorination of CCl
3
CH
2
CHCl
2
with HF/SbCl
5
to produce HFC-245fa.
It is an object of this invention to provide a means of preparing 1-chloro-1,1,3,3,3 pentafluoropropane that is economical and amenable to large scale, using readily available raw materials.
It is a further object of this invention to provide a means of manufacturing 1,1,1,3,3-pentafluoropropane comprising reacting CF
3
CH
2
CF
2
Cl with hydrogen in the presence of a reduction catalyst wherein the said CF
3
CH
2
CF
2
Cl is prepared by reacting CCl
3
CH
2
CCl
3
with hydrogen fluoride in the presence of a fluorination catalyst in either the liquid phase or the vapor phase.
It is a further object of this invention to provide a means of manufacturing 1,1,1,3,3-pentafluoropropane comprising the following steps:
1) the formation of CCl
3
CH
2
CCl
3
by the reaction of CCl
4
with vinylidene chloride;
2) the conversion of CCl
3
CH
2
CCl
3
to CF
3
CH
2
CF
2
Cl by reaction with hydrogen fluoride (HF) in the presence of a fluorination catalyst either in the liquid phase or in the vapor phase; and
3) reduction of CF
3
CH
2
CF
2
Cl to CF
3
CH
2
CF
2
H.
Each step is conducted under process conditions, i.e., temperature and pressure, sufficient to produce the desired product as discussed herein.
DETAILED DESCRIPTION
The telomerization of vinylidene chloride by reaction with CCl
4
, is known in the art and has been studied in some detail. The telomerization reaction produces compounds of the formula CCl
3
(CH
2
Cl)
n
Cl, where n varies as needed for the products desired. The telomerization of vinylidene chloride can be initiated by several means, but initiation with metal salts, particularly of copper, has distinct advantages for the process of this invention. The copper salts are believed to initiate the reaction by first reacting with CCl
4
, to produce a trichloromethyl radical which then combined with vinylidene chloride, initiating the telomerization (see for example, Assher and Vofsi, J. Chem. Soc., 1961, 2261 for a discussion of the mechanism). The copper salts also terminate the telomerization by chlorine atom transfer to the growing radical chain. Thus, the chain lengths are shortened considerably, compared to e.g., peroxide initiated telomerizations. For the reactions of interest here, telomers having 3 to 9 carbon atoms are obtained in excellent yield. Some control of the telomer distribution is feasible by controlling the reaction conditions, notably the ratio of CCL
4
to vinylidene chloride and the type of copper salt used (see for example Belbachir et al., Makromol. Chem. 1984, 185, 1583-1595). Thus, it is possible to obtain CCl
3
CH
2
CCl
3
with very little higher molecular weight telomers (see Example 1).
A variety of catalysts have been used in telomerization processes. To a large degree, many of these telomerization catalysts, including mixtures thereof, can be equivalent, and the choice of catalyst depends on cost, availability, and solubility in the reaction medium. For the telomerization reaction of this invention, it was discovered that salts of copper and iron are preferred. Overall, for the reaction of interest here, the more preferred catalysts are cuprous chloride, cupric chloride, or mixtures of the two or cuprous iodide. The amount of catalysts used in the telomerization reaction is at least about 0.1 mmol, and preferably, about 0.1 to about 50 mmol, per mole of saturated halogenated hydrocarbon (e.g., CCl
4
or CCl
3
CH
2
CCl
3
) used. At very low concentrations, the reaction rate may be unacceptably slow, and very high catalyst concentrations may be wasteful due to the fact that the solubility limit may have been reached at even lower catalyst to CCl
4
, ratios. Consequently, the more preferred amount of catalyst is about 1 to 20 mmol, per mole of saturated halogenated hydrocarbon.
It is also noted that a co-catalyst can be used in the telomerization process. Amines may be employed as co-catalysts, preferably in concentration of 1 to 10 moles per mole of metal catalyst (i.e. copper salt). Such amine co-catalysts include alkanol amines, alkyl amines and aromatic amines, for example ethanolamine, butyl amine, propyl amine, benzylamine, pyridine and the like.
The ratio of CCl
4
to vinylidene reactant will substantially alter the degree of polymerization, i.e. average value of n for compounds of the formula CCl
3
(CH
2
Cl)
n
Cl. Thus, for example, if the desired product has only one more —CH
2
CCl
2
— unit than the starting material, the ratio of CCl
4
(or CCl
3
CH
2
CCl
3
) to vinylidene chloride should be relatively high (at least about 2, and preferably, about 2 to 5), so that higher molecular weight telomers are minimized. If the desired product has two or more —CH
2
CCl
2
— units than the starting material (e.g., CCl
3
(CH
2
CCl
2
)
2
Cl from CCl
4
), smaller ratios of CCl
4
to vinylidene chloride (about 0.3 to 1) should be used. The same rationale is used for a system employing vinylidene fluoride.
Useful temperatures for the telomerization reaction range from ab

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