The present invention relates to a process for preparing (hydro) (chloro)fluoroolefins. One subject of the present invention is more particularly a process for preparing (hydro)(chloro)fluoropropenes.
Document JP 4110388 describes the use of hydrofluoropropenes of Sformula C3HmFn, with m, n representing an integer between 1 and 5 inclusive and m + n = 6, as a heat transfer fluid, in particular tetrafluoropropene and trifluoropropene.
Quite recently, document WO 2004/037913 teaches the use of tetrafluoropropene and pentafluoropropene as refrigerants having a low GWP I0(low global warming potential).
Hydrofluoroolefins are in general obtained by the dehydrohalogenation
reaction. Thus, pentafluoropropene (CF3CH=CF2) is obtained either from
monochloropentafluoropropane by removing one molecule of HCI or from
hexafluoropropane by removing one molecule of HF (WO 05/030685,
15WO 98/33755).
Tetrafluoropropene may also be obtained by the dehydrofluorination reaction of pentafluoroethane (US 5986151).
Trifluoropropene and tetrafluoropropene are also formed during the fluorination reaction of pentachloroethane with HF in the presence of a catalyst 20(WO 98/12161).
Another route for preparing trifluoropropene and/or tetrafluoropropene consists in reacting trichloropropene with HF in the presence of a catalyst (US 5811603).
Furthermore, liquid-phase fluorination reactions necessitate, in order to 25be effective, using a reaction medium that is rich in HF and SbCI5 (or SbClxFy) and temperatures between 80 and 120°C. Anhydrous HF in the form of a liquid phase forms, with SbCI5, a very corrosive superacids medium.
The present invention describes a process for preparing (hydro)
(chloro)fluoroolefins,
30 of general formula (I) CaF6ClcH2a-i,-c with a representing an integer
between 3 and 6, b representing an integer between 1 and 2a, c representing either the value zero or an integer between 1 and (2a-l),
comprising at least one step of liquid-phase fluorination of a
(hydro)haloalkane of general formula (II) CaF/,XcH2a+2-6-cWith a having the same meaning as in formula (I), b' representing either the value zero or an integer between 1 and 2a-l with b > b\ X representing an atom of CI, Br or I and c' representing an integer between 1 and 2a+2; when X represents an atom of CI, 5c' > c;
or a (hydro)haloalkene of general formula (III) CJFvXc^aw with a
having the same meaning as in formula (I), b" representing either the value zero
or an integer between 1 and 2a-l with b > b", X representing an atom of CI, Br
or I and c" representing an integer between 1 and 2a; when X represents an
lOatom of CI, c" > c,
in the presence of at least one ionic liquid as a catalyst.
The (hydro)haloalkane of general formula (II) may originate from a
telomerization reaction between a haloalkane preferably having one carbon
atom and a haloalkene.
15 Preferably, a represents an integer equal to 3 or 4 and advantageously a
is equal to 3.
The preferred (hydro)(chloro)fluoroolefins are trifluoropropene
(CF3CH=CH2), chlorotrifluoropropene (CF3CH=CHCI), 1,1,1,3-
tetrafluoropropene (CF3CH=CHF) and its isomers, 1,1,1,2-tetrafluoropropene
20(CF3CF=CH2), 1,1,1,3,3-pentafluoropropene (CF3CH=CF2) and 1,1,1,2,3-
pentafluoropropene (CF3CF=CHF).
The fluorination step is advantageously carried out in the presence of anhydrous hydrofluoric acid.
The process according to the invention may also comprise a step of 25dehydrohalogenation or of hydrofluori nation of the fluorinated product or products resulting from the reaction in the presence of at least one ionic liquid.
According to one preferred embodiment of the invention, a (hydro)haloalkane of general formula (II), with a equal to 3, b' equal to zero, c' equal to 5 or 6 and X preferably representing CI, is reacted with anhydrous 30hydrofluoric acid in the presence of a catalyst comprising at least one ionic liquid in order to give a fluorinated compound of formula C3HnF8-n with n equal to 2 or 3. The fluorinated compound, after optional separation, is then subjected to a dehydrofluorination step in order to give the desired hydrofluoroolefin.
According to another preferred embodiment of the invention, a (hydro)haloalkene of general formula (III) with a equal to 3, b" equal to zero, c" equal to 4 and X preferably representing CI, is reacted with anhydrous hydrofluoric acid in the presence of a catalyst comprising at least one ionic liquid in order to give a fluorinated compound of formula C3H2FpX4-p, p representing a value equal to 3 or 4, and/or of formula C3HnF8.n with n possibly taking the value 2 or 3. When the products resulting from the fluorination step comprise a compound of formula C3H„F8-n, the latter is subjected to a dehydrofluorination step.
Thus, 2-chloro-l,l,l-trifluoropropene (1233 xf) and/or 1,1,1,2-tetrafluoropropene (1234 yf) may be obtained from 1,1,2,3-tetrachloropropene (1230 xa) by liquid-phase fluorination in the presence of at least one ionic liquid as a catalyst.
1,1,1,2-Tetrafluoropropene (1234 yf) may also be obtained from 2-chloro-l,l,l-trifluoropropene (1233 xf) by liquid-phase fluorination in the presence of at least one ionic liquid as a catalyst in order to give 2-chloro,l,l,l,2-tetrafluoropropane (244 bb) and/or 1,1,1,2,2-pentafluoropropane (245 bb) which is or are then subjected to a step of dehydrohalogenation either in the liquid phase or in the gas phase.
Similarly, 1,1,1,3-tetrafluoropropene (1234 ze) may be obtained from 3-chloro-l,l,l-trifluoropropene (1233 zd).
Furthermore, 1,1,1,2-tetrafluoropropene (1234 yf) may be obtained from l,l,l,2-tetrachloro,2-fluoropropane (241 bb) by liquid-phase fluorination in the presence of at least one ionic liquid as a catalyst.
The ionic liquids which may be suitable are derivatives of Lewis acids based on aluminum, titanium, niobium, tantalum, tin, antimony, nickel, zinc or iron.
The expression "ionic liquids" is understood to mean non-aqueous salts having an ionic character that are liquid at moderate temperatures (preferably below 120°C). The ionic liquids preferably result from the reaction between an organic salt and an inorganic compound.
The ionic liquids are preferably obtained by reaction of at least one halogenated or oxyhalogenated Lewis acid based on aluminum, titanium,
niobium, tantalum, tin, antimony, nickel, zinc or iron with a salt of general formula Y+A, in which A" denotes a halide (bromide, iodide and preferably chloride or fluoride) anion or hexafluoroantimonate (SbF6) anion and Y* a quaternary ammonium cation, quaternary phosphonium cation or ternary sulfonium cation.
The halogenated Lewis acid based on aluminum, titanium, niobium, tantalum, antimony, nickel, zinc or iron may be a chlorinated, brominated, fluorinated or mixed derivative, for example a chlorofluorinated acid. Mention may more particularly be made of the chlorides, fluorides or chlorofluorides of the following formulae:
TiClxFy with x+y = 4 and 0 < x <, 4
TaCIKFy with x+y = 5 and 0 < x £ 5
NbClxFy with x+y = 5 and 0 £ x <, 5
SnClxFy with x+y = 4 and 1 < x < 4
SbClxFy with x+y = 5 and 0 £ x < 5
AlClxFy with x+y = 3 and 0 < x <, 3
NiClxFy with x+y = 2 and 0 <, x <, 2
FeClxFy with x+y = 3 and 0 <, x £ 3 As examples of such compounds, mention may be made of the following compounds: TiCI4, TiF4, TaCI5, TaF5, NbCI5, NbF5, SbCI5, SbCI4F, SbCI3F2, SbCI2F3, SbCIF4, SbF5 and mixtures thereof. Use is preferably made of the following compounds: TiCI4, TaCI5+TaF5, NbCI5+NbF5, SbCI5, SbFCU, SbF2CI3, SbF3CI2, SbF4CI, SbF5 and SbCI5+SbF5. The antimony compounds are more particularly preferred.
As examples of oxyhalogenated Lewis acids that can be used according to the invention, mention may be made of TiOCI2, TiOF2 and SbOCIxFy (x+y=3). In the Y*A" salt, the Y+ cation may correspond to one of the following general formulae:
R1R2R3R4N+
RXR2R3S+
in which the symbols R1 to R4, which are identical or different, each
denote a hydrocarbyl, chlorohydrocarbyl, fluorohydrocarbyl,
chlorofluorohydrocarbyl or fluorocarbyl group having from 1 to 10 carbon atoms, which is saturated or unsaturated, cyclic or non-cyclic, or aromatic, one or more of these groups possibly also containing one or more heteroatoms such as N, P, SorO.
The ammonium, phosphonium or sulfonium cation Y+ may also be part of a saturated or unsaturated, or aromatic heterocycle having from 1 to 3 nitrogen, phosphorus or sulfur atoms, and may correspond to one or the other of the following general formulae:
(FORMULA REMOVED)
in which R1 and R2 are as defined previously.
A salt containing 2 or 3 ammonium, phosphonium or sulfonium sites in its formula may also be suitable.
As examples of YW salts, mention may be made of tetraalkylammonium chlorides and fluorides, tetraalkylphosphonium chlorides and fluorides, and triaikylsulfonium chlorides and fluorides, alkylpyridinium chlorides and fluorides, dialkylimidazolium chlorides, fluorides and bromides and trialkylimidazolium chlorides and fluorides. More particularly appreciated are trimethylsulfonium fluoride or chloride, N-ethyfpyridinium chloride or fluoride, N-butyipyridinium chloride or fluoride, l-ethyl-3-methylimidazolium chloride or fluoride and 1-butyl-3-methylirnidazolium chloride or fluoride.
The ionic liquids may be prepared in a manner that is known per se by mixing, in an appropriate manner, the halogenated or oxyhalogenated Lewis acid and the organic salt Y+A~. Reference may especially be made to the method described in document WO 01/81353.
The ionic liquids that are advantageously preferred are those resulting from a Lewis acid/organic salt molar ratio that is strictly greater than 1:1.
The step of liquid-phase fluorination using, as catalyst, an ionic liquid
may be carried out in batch mode, semi-continuously and continuously. When
the fluorination step is carried out in batch mode, the molar amount of HF to the
molar amount of starting product is between 2 and 50 and preferably between
and 30.
When the fluorination is carried out continuously, the molar amount of HF supplied to the molar amount of starting product supplied is at least equal to the stoichiometric ratio.
The amount of catalyst depends on the operating conditions, on the reaction medium (in the case of a continuous process) but also on the intrinsic activity of the catalyst. This amount is between 0.5 and 90 (mol)% of the reaction medium.
When the catalyst used is based on antimony, it may sometimes be advantageous to introduce chlorine in order to keep the antimony in the +5 degree of oxidation.
The temperature at which the fluorination reaction (under batch and continuous conditions) is carried out is generally between 30 and 180°C, preferably between 80 and 130°C.
The pressure at which the reaction is carried out in semi-continuous or continuous modes is chosen so as to keep the reaction medium in the liquid phase. It is generally situated between 5 and 50 bar and preferably between 10 and 40 bar; under continuous conditions, if HF constitutes the reaction medium, the operating pressure chosen is in general the saturation vapor pressure of the HF at the desired reaction temperature. The temperature of the condenser is set as a function of the amount and of the nature of the products likely to be discharged during the reaction. It is generally between -50 and 150°C and preferably between 0 and 100°C.
A reactor made of stainless steel or of MONEL, INCONEL or HASTELLOY type alloys may be suitable for the fluorination. Compared to a conventional catalyst, the step of fluorination in the presence of an ionic liquid is less corrosive.

We Claim:
1) A process for preparing (hydro)(chloro)fluoroolefins, of general formula (I) CaFbClcH2a-^ with a representing an integer between 3 and 6, b Srepresenting an integer between 1 and 2a, c representing either the value zero or an integer between 1 and (2a-l),
comprising at least one step of liquid-phase fluoridation of a (hydro) haloalkane of general formula (II) CaF6'Xc'H2a+2-b-c with a having the same meaning as in formula (I), b' representing either the value zero or an integer lObetween 1 and 2a-l with b > b', X representing an atom of CI, Br or I and c' representing an integer between 1 and 2a+2; when X represents an atom of CI, c' > c;
or a (hydro)haloalkene of general formula (III) CaFbXc"H2a-b- with a
having the same meaning as in formula (I), b" representing either the value zero
l5or an integer between 1 and 2a-l with b > b'\ X representing an atom of CI, Br
or I and c" representing an integer between 1 and 2a; when X represents an
atom of CI, c" > c,
in the presence of at least one ionic liquid as a catalyst.
2 ) The process as claimed in claim 1, characterized in that a represents
20an integer equal to 3 or 4 and advantageously a is equal to 3.
3 ) The process as claimed in claim 1 or 2, characterized in that the
(hydro)(chloro)fluoroolefins are trifluoropropene (CF3CH=CH2),
chlorotrifluoropropene (CF3CH=CHCI), 1,1,1,3-tetrafluoropropene
(CF3CH=CHF) and its isomers, 1,1,1,2-tetrafluoropropene (CF3CF=CH2),
251,1,1,3,3-pentafluoropropene (CF3CH=CF2) and 1,1,1,2,3-pentafluoropropene (CF3CF=CHF).
4 ) The process as claimed in any one of the preceding claims,
characterized in that the process comprises a step of dehydrohalogenation or of
hydrofluorination of the fluorinated product or products resulting from the
30reaction in the presence of at least one ionic liquid.
5 ) The process as claimed in any one of the preceding claims,
characterized in that the ionic liquids are derivatives of Lewis acids based on
aluminum, titanium, niobium, tantalum, tin, antimony, nickel, zinc or iron.
6 ) The process as claimed in any one of the preceding claims,
characterized in that a (hydro)haloalkane of general formula (II), with a equal to
3, b' equal to zero, c' equal to 5 or 6 and X preferably representing CI, is
reacted with anhydrous hydrofluoric acid in the presence of a catalyst
comprising at least one ionic liquid in order to give a fluorinated compound of
formula C3HnF8-n with n equal to 2 or 3; the fluorinated compound, after optional
separation, is then subjected to a dehydrofluorination step.
7 ) The process as claimed in any one of the preceding claims,
characterized in that a (hydro)haloalkene of general formula (III) with a equal to
3, b" equal to zero, c" equal to 4 and X preferably representing CI, is reacted
with anhydrous hydrofluoric acid in the presence of a catalyst comprising at
least one ionic liquid in order to give a fluorinated compound of formula
C3H2FpX4-p, p representing a value equal to 3 or 4, and/or of formula C3H„F8-n
with n possibly taking the value 2 or 3.
8 ) The process as claimed in claim 7, characterized in that the
compound of formula C3H„F8-n is subjected to a dehydrofluorination step.