Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2000-09-29
2002-03-26
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S167000, C570S168000, C570S169000
Reexamination Certificate
active
06362383
ABSTRACT:
The present invention relates to a process for the hydrofluorination of a chlorohydrocarbon by reaction with hydrogen fluoride in the presence of a hydrofluorination catalyst, and in particular to a process for the manufacture of 1,1,1,3,3-pentafluoropropane.
Liquid-phase hydrofluorination processes, based on the reaction of hydrogen fluoride and an organochlorine compound, in the presence of a catalyst, have been known for a long time. The desired products are organic compounds similar to the organochlorine compound used, in which the chlorine atoms have been partially or totally replaced with fluorine atoms. However, the degree of conversion of the reagents used is often low and the selectivity toward desired product is insufficient, in particular when a complete fluorination is desired. In certain cases, several steps are required in order to obtain the desired fluoro products. Thus, patent application WO 97/24307 discloses the two-step synthesis of 1,1,1,3,3-pentafluoropropane (HFC-245fa) starting with 1,1,1,3,3-pentachloropropane. The 1,1,1,3,3-pentachloropropane first reacts, in the gas phase, with hydrogen fluoride to give 1,1,1-trifluoro-3-chloro2-propene, which, after removal of the hydrogen chloride formed, reacts in a second step with hydrogen fluoride to give HFC-245fa.
It is consequently advantageous to have available an efficient hydrofluorination process allowing chlorine atoms to be replaced with fluorine atoms more easily and with high selectivity.
The term “hydrofluorination” means the addition reaction of hydrogen fluoride to a carbon-carbon double bond as well as the substitution reaction of a chlorine atom with a fluorine atom on a saturated substrate.
Consequently, the invention relates to a process for the hydrofluorination of a chlorohydrocarbon by reaction with hydrogen fluoride, in a reaction medium comprising a hydrofluorination catalyst, in which process hydrogen chloride is continuously fed into the reaction medium.
In the hydrofluorination process according to the present invention, the expression “continuous feed of hydrogen chloride” means the addition of hydrogen chloride into the reaction medium throughout the reaction, either in gaseous form or in liquid form, or in the form of any compound other than the reagents which is capable of generating hydrogen chloride in the reaction medium under the operating conditions selected.
In a continuous hydrofluorination process, the molar ratio between the hydrogen chloride added by continuous feed and the chlorohydrocarbon introduced continuously into the reactor is generally greater than or equal to 1.
This molar ratio is advantageously greater than or equal to 3. However, this molar ratio is usually less than or equal to 100. This ratio is advantageously less than or equal to 50. In a particularly preferred manner, this ratio is greater than or equal to 5 and less than or equal to 25.
When the hydrofluorination process according to the invention is carried out in a batchwise manner, the hydrogen chloride can be fed in continuously, for example, by introducing a stream of hydrogen chloride gas into the reaction medium throughout the reaction. In this case, the hydrogen chloride feed rate is adjusted such that the ratio between the total amount of hydrogen chloride introduced throughout the reaction to the amount of chlorohydrocarbon initially used corresponds to the molar ratios indicated above.
The chlorohydrocarbon used in the hydrofluorination process according to the invention can be an aliphatic alkane corresponding to the general formula C
w
H
x
Cl
y
F
z
(I) in which w is an integer between 1 and 6, x is an integer between 0 and (2w+1), y is an integer between 1 and (2w+1), z is an integer between 0 and (2w+1) and the sum (x+y+z) is equal to (2w+2). The chlorohydrocarbon used in the process according to the invention is advantageously an aliphatic alkane corresponding to formula (I) in which w is an integer between 1 and 4 and x is an integer between 1 and 2w. As non-limiting examples of chloroalkanes used in the process according to the invention, mention may be made of dichloromethane, chlorofluoromethane, chlorodifluoromethane, 1-chloro-1-fluoroethane, 1,1-dichloro-1-fluoroethane and 1-chloro-1,1-difluoroethane, chlorotetrafluoroethane isomers, dichlorotrifluoroethane isomers, trichlorodifluoroethane isomers, tetrachlorofluoroethane isomers, pentachloroethane, compounds of general formula C
3
H
3
Cl
(5−z)
F
z
, C
4
H
5
Cl
(5−z)
F
z
with z representing an integer which can take the values from 0 to 4.
The chlorohydrocarbon used in the hydrofluorination process according to the invention can also be an aliphatic alkene corresponding to the general formula C
w
H
x
Cl
y
F
z
(II) in which w is an integer between 1 and 6, x is an integer between 0 and (2w−1), y is an integer between 1 and (2w−1), z is an integer between 0 and (2w−1) and the sum (x+y+z) is equal to 2w. The chlorohydrocarbon used in the process according to the invention can also advantageously be an aliphatic alkene corresponding to the formula (I) in which w is an integer between 1 and 4. As non-limiting examples of chloroalkenes used in the process according to the invention, mention may be made of 1,1-dichloroethylene, trichloroethylene, perchloroethylene, vinyl chloride, 3,3,3-trichloro-1-propene, 1,1,3-trichloro-1-propene, 1,1,3,3,-tetra-chloro-1-butene, 1,1,1,3-tetrachloro-2-butene, 1,1,1,3 -tetrachloro-3-butene, 1,1,4,4,4-pentachloro-1-butene, 1,1,1,3-tetrachloro-2-propene, 1,1,3,3-tetrachlorol-1-propene, 1,1,3,3-tetrachloro-2-methyl-2-propene, 1,1,1,3-tetrachloro-2-methyl-2-propene and 1-chloro-3,3,3-trifluoropropene, as well as mixtures of these compounds.
One object of the invention is thus, starting with saturated or unsaturated chlorohydrocarbons, to produce fluoroalkanes or chlorofluoroalkanes which contain more fluorine atoms and fewer chlorine atoms than the reagents used. The invention is directed in particular toward the synthesis of fluorohydrocarbons or chlorofluorohydrocarbons such as, in particular, difluoromethane, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,1-trifluoroethane, 1,1-difluoroethane, 1,2,2-trichloro-1,1-difluoroethane, 2,2-dichloro-1,1,1-trifluoroethane, 1,1,1-trifluoro-2-chloroethane, 1,1,1,3-tetrafluoro-3-chloropropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3,3-hexafluorobutane, 1,1,1,3,3-pentafluoro-2-methylpropane and 1,1,1,3,3,3-hexafluoropropane. The hydrofluorination process according to the invention is particularly suitable for preparing fluoroalkanes containing no chlorine atoms in their molecular structure, starting with saturated chlorohydrocarbons, as well as to the preparation of chlorofluoroalkanes starting with unsaturated chlorohydrocarbons.
In the hydrofluorination process according to the present invention, the reaction medium is advantageously in liquid form and the hydrofluorination catalyst contained therein is advantageously chosen from derivatives of metals from groups 3, 4, 5, 13, 14 and 15 of the Periodic Table of the Elements (IUPAC 1988) and mixtures thereof. The expression “derivatives of metals” means the hydroxides, oxides and inorganic salts of these metals, as well as mixtures thereof. Derivatives of titanium, niobium, tantalum, molybdenum, boron, tin and antimony are particularly selected. The catalyst is preferably chosen from derivatives of the metals from groups 4, 5, 14 and 15 of the Periodic Table of the Elements, and more particularly from derivatives of titanium, tantalum, tin and antimony. In the process according to the invention, the preferred metal derivatives are the salts of these metals, and the salts are preferably chosen from the halides, and more particularly from the chlorides, fluorides and chlorofluorides. Hydrofluorination catalysts that are particularly advantageous in the process according to the invention are the chlorides, fluorides and chlorofluorides of titanium, tin and antimony, in particular titanium tetrachloride, tin tetrachlor
Janssens Francine
Wilmet Vincent
Connolly Bove & Lodge & Hutz LLP
Siegel Alan
Solvay ( Societe Anonyme)
LandOfFree
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