Description
Process for dehydrochlorination of hydrochlorofluoroalkanes
[0001] This application claims priority to US provisional patent application
No. 61/320425 filed April 2nd, 2010, the whole content of this application
being incorporated herein by reference for all purposes.
[0002] The present invention relates to a process for dehydrochlorinating
hydrochlorofluoroalkanes.
[0003] WO 2009/010472 discloses a process for the preparation of halogen
containing alkenes over metal fluoride catalysts. Hydrochlorofluoroalkanes
are also mentioned as suitable starting materials, but metal fluorides
containing chlorine are not mentioned amongst the catalysts.
[0004] US 2,673,139 discloses a method for preparing aluminum fluoride
catalysts with high activity in dehydrohalogenation reactions. The
aluminum fluoride does not contain chlorine.
[0005] Mixed chloride fluorides such as barium chloride fluoride are known per se
and described in the literature. However, such compounds have not been
used as catalysts for dehydrohalogenation reactions before.
[0006] The products obtained by dehydrochlorination of hydrochlorofluoroalkanes
are interesting intermediates for the synthesis of other hydrofluorocarbons
and thus there exists a need for selective dehydrochlorination catalysts
and processes.
[0007] It was thus an object of the instant invention to provide a process for the
dehydrochlorination of hydrochlorofluoroalkanes which yields the
dehydrochlorinated products in high yield and with good selectivity.
[0008] This object is achieved with the process in accordance with claim 1.
Preferred embodiments of the invention are set forth in the dependent
claims and the detailed description hereinafter.
[0009] Thus, the instant invention relates to a process for the selective
dehydrofluorination of hydrochlorofluoroalkanes, said
hydrochlorofluoroalkanes comprising at least one chlorine atom and at
least one fluorine atom and at least one hydrogen atom at the carbon atom
wo 2011/121058 PCT /EP2011/054980
2
or atoms vicinal to the carbon atom or carbon atoms carrying the chlorine
and fluorine atoms.
[001 0] The hydrochlorofluoroalkanes are not subject to further restrictions as far
as their structure is concerned, i.e. any representative of this class of
products fulfilling the foregoing prerequisites are suitable for use in the
process in accordance with the instant invention.
[0011] Generally, the chlorine and fluorine substituents may be located at the
same or different carbon atoms in the molecule. If a chlorine and a fluorine
substituent are present at different carbon atoms, the hydrogen atoms at
carbon atoms vicinal thereto might be attached to different carbon atoms
or to the same carbon atom in case at least one chlorine and fluorine
substituent are attached to different carbon atoms separated by one
carbon atom carrying such hydrogen substituent. In this case, one
hydrogen substituent in the molecule is sufficient.
[0012] Dehydrohalogenation reactions require this structural feature as in the
reaction a hydrogen halide is split off, the hydrogen and the halogen
arising from vicinal or neighboured carbon atoms.
[0013] Preferred hydrochlorofluoroalkanes which are suitable as educts for the
process in accordance with the instant invention comprise either at least
one structural element Ia and at least one structural element lb or at least
one structural element II
F H 7 ~
(Ia)
F H
) ~ Cl
(II)
[0014] The substituents not shown in the formulae above are preferably selected
from C1-Cs-alkyl groups, which may be substituted by halogen, in
particular by chlorine or fluorine.
wo 2011/121058 PCT /EP2011/054980
3
[0015] A particularly preferred group of hydrochlorofluoroalkanes has the formula
Ill
H R3
1w4(111)
R 2 R
R
Cl
wherein R1 to R4 are the same or different and independently of each
other represent a hydrogen atom, a fluorine atom a C1-Cs-alkyl, a C1-Csfluoroalkyl
or a C1-Cs-hydrofluoroalkyl group.
[0016] Hydrochlorofluoroalkanes having 1 to 6 carbon atoms and preferably 1 to
4 carbon atoms are preferred substrates. 3-chloro-1, 1,1 ,3-
tetrafluorobutane is a particularly preferred substrate.
[0017] The starting materials which can be used in the process according to the
instant invention are known to the skilled man and are available from
various sources. 3-chloro-1, 1 ,3,3-tetrafluorobutane (also referred to as
HCFC-364mfb according to the generally used nomenclature system used
for halogenated hydrocarbons), for example, is inter alia disclosed in US
patent 7,074,434 and other suitable starting materials are described
elsewhere.
[0018] Various routes for the manufacture of halogenated hydrocarbons with at
least 3 carbon atoms are disclosed in WO 2008/043720 to which reference
is made herewith for further details.
[0019] In the process in accordance with the instant invention
hydrochlorofluoroalkanes as described hereinbefore are subjected to a
reaction at a temperature preferably above 50°C with an effective amount
of a metal compound having the formula
(M 1 )x(M2)1-xCI1+yF 1-y
wherein
M1 and M2 are selected from the group consisting of Ca, Sr and Ba
x is in the range of from 0.2 to 1.0 and
y is in the range of from -0.8 to 0.8.
wo 2011/121058 PCT /EP2011/054980
4
[0020] According to a preferred embodiment of the process in accordance with
the instant invention y has a value in the range of from -0.6 to 0.6, more
preferably in the range of from -0.6 to 0.3 and even more preferred in the
range of from -0.6 to 0. Most preferred y has a value in the range of from
-0.4 to 0.
[0021] x has preferably a value of at least 0.5, preferably 0.5 to 1.0 and more
preferably at least 0.8. Most preferred xis 1, i.e. compounds having only
one metal are most preferred.
[0022] Among the metals, Ba and Sr are preferred, Ba being the most preferred
metal.
[0023] Surprisingly it has been found that these catalytically effective metal
compounds in this reaction yield the dehydrochlorinated products with a
very good selectivity, which is typically at least 80, preferably at least 90
%, the remainder being dehydrofluorination products.
[0024] Depending on the starting materials more than one dehydrochlorination
product and/or more than one dehydrofluorination product as by-product
may be obtained and in this case the selectivity is expressed based on the
aggregate amount of dehydrochlorination respectively dehydrofluorination
products.
[0025] Particularly preferably, the selectivity towards dehydrochlorinated products
vs. dehydrofluorinated products is at least 92 %, most preferred above 94
%and may be 100 %, i.e. no detectable dehydrofluorination product in
particular cases.
[0026] In accordance with a preferred embodiment of the instant invention, the
metal compound is obtainable by
a) providing a precursor, optionally on a support, wherein the precursor
comprises a structure having the formula (M 1 )x(M2)1-xF2-o-dBdle and
b) reacting the precursor with a hydrochlorofluoroalkane
wherein B is a co-ordinatively bound group; Lis an organic solvent; x has
a value in the range of from 0.2. to 1.0, d is any integer in the range of
from 0 to 2, e has a value in the range of from 0 to 1 and o has a value in
the range of from 0 to 0.1, provided that the denominators representing the
number of chlorine and fluorine atoms are positive.
wo 2011/121058 PCT /EP2011/054980
5
[0027] B is preferably an alkoxide, enolate or carboxylic acid group, more
preferably an alkoxide group of the formula -O-CcH2c+1 wherein cis any
integer from 1 to 6, preferably of from 1 to 3 ; L is a solvent, preferably an
anhydrous organic solvent selected from the group comprising alcohols,
ethers, ketones, alkanes and aromatics ; and d and e are preferably less
than or equal to 1.
[0028] Preferred processes for the synthesis of the metal compounds used in
accordance with the process of the invention comprising these steps are
disclosed in WO 2004/060806 and EP 1,666,411 which are incorporated
herein by reference. Such processes are referred to hereinafter as
fluorolytic sol-gel synthesis.
[0029] The process of the instant invention is not limited, however, to metal
compounds obtained in accordance with these references only; any metal
compound having the formula according to claim 1 is principally suitable.
[0030] According to WO 2004/060806, the precursor is preferably obtained by
reacting (M 1 )x(M2)1-xB2, wherein B is preferably an alkoxide. B is more
preferably dissolved or suspended in an organic solvent L, with of from 2
to 4 equivalents, preferably about 3 equivalents (preferably anhydrous)
HF. The HF is preferably dissolved in an organic solvent L', whereby L'
can be any of the solvents Land also L' can be equal to or different from
L; followed by removing excessive solvents under vacuum at temperatures
equal to or less than 350°C, preferably equal to or less than 200°C, still
more preferably equal to or less than 1 00°C. The product obtained thereby
is a precursor as defined above.
[0031] The preparation of the precursor is preferably performed in a water free
solvent, preferably selected from the group consisting of alcohols, ethers,
ketones, alkanes, petroleum ether, formic acid, acetic acid or propionic
acid. Alcohols of formula CcH2c+10H with c = 1 to 6, especially 1 to 3, are
preferred.
[0032] The precursor obtained thereby, in a second step, is further activated by
reaction with a (hydro)chlorofluoroalkane, preferably CCI2F2 or CHCIF2 or
3-chloro-1, 1,1 ,3-tetrafluorobutane or the hydrochlorofluoroalkane which is
the substrate for the dehydrochlorination reaction.
wo 2011/121058 PCT /EP2011/054980
6
[0033] The suitable metal compounds used in the process in accordance with the
instant invention can be prepared as described above by selecting the
appropriate precursors.
[0034] Metal compounds as obtained by the processes in accordance with WO
2004/060806 and EP 1 ,666,411 and as described in preferred
embodiments hereinbefore have generally a high surface area, preferably
in the range of from 40 to 200 m2/g, as measured according to the BET
method using N2 (see [0091] of US 2006/052649 A1 for details).
Particularly preferred the surface area of the metal compounds thus
obtained is in the range of from 50 to 160 m2/g.
[0035] The metal compounds can be used as such or on a support material.
[0036] Preferably, a support is selected which has a suitably shaped form, is
chemically and thermally stable under the conditions of catalyst synthesis
and under reaction conditions of catalyst use, mechanically stable, not
deteriorating the performance of the catalyst, not interfering with the
catalyzed reaction, and enabling anchoring of the metal compound. Any
support which meets these requirements can be used. For example,
oxides of aluminum or of transition metals are very suitable. Usually, these
are present in crystalline form. Activated carbon can also be applied; in a
preferred embodiment, aluminum oxide and in an even more preferred
embodiment y-AI203 is used as support.
[0037] Preferably, the total amount of metal compound (M1)x(M2)1-xCI1+yF1-y,
especially of BaCI1+yF1-y in the supported catalyst is equal to or greater
than 3 % by weight, more preferably equal to or more than 4 % by weight.
Preferably, the content of metal compound in the supported catalyst is
equal to or less than 30 % by weight, more preferably equal to or less than
20 % by weight. In some applications, the content can be equal to or less
than 10 % by weight. A range with good results is between 4 and 20 % by
weight. A range of 4 to 8 % by weight also gives good results.
[0038] The procedure for coating the active metal compound on the catalyst
support can be performed by methods known to the skilled man and
described in the literature. Two specific alternatives are preferred. Both
wo 2011/121058 PCT /EP2011/054980
7
alternatives comprise a step wherein a support coated with the precursor
is formed and a step wherein the activation takes place.
[0039] According to the first preferred alternative, the support is impregnated with
the precursor compound (M 1 )x(M2)1-xBd as described above. After
impregnation, the sol-gel reaction with HF, preferably in a solvent, is
performed to obtain the precursor.
[0040] In detail, the support, preferably thermally pretreated y-AI203, is given,
preferably under stirring, to a solution of a suitable metal compound,
preferably an alkoxide, more preferably an isopropoxide or a methoxide, in
an anhydrous organic solvent, preferably an alcohol.
[0041] Contact between support and metal compound, preferably under stirring,
is continued for a sufficient time to achieve the desired degree of
impregnation. For example, after addition of the metal compound, the
contact can be continued for equal to or more than 10 minutes, preferably,
for equal to or more than 20 minutes. The contact can be extended, if
desired, to a very long time, for example, more than 6 hours. It is assumed
that the longer the contact, the deeper the metal compound will penetrate
into the support. Preferably, the contact between support and metal
compound is equal to or less than 6 hours, still more preferably, equal to
or less than 2 hours. Often, 20 minutes to 45 minutes are very suitable.
[0042] Thereafter, the product obtained after impregnation is transformed into the
precursor. A solution of anhydrous hydrogen fluoride in an organic solvent,
preferably in a C1 to C3 alcohol or in diethyl ether, is added, preferably
under continued stirring, to the system of support and metal compound.
The amount of HF is selected so that the molar ratio of HF:metal is
preferably equal to or greater than 2. Preferably, it is equal to or lower than
4. Very preferably, the molar ratio of HF:metal is 3 ± 0, 1.
[0043] Preferably, the total amount of metal compound starting material in the
system is adjusted to correspond to a metal compound content of the final
catalyst of equal to or greater than 3 % by weight, more preferably equal to
or more than 4 % by weight. Preferably, the content of metal compound in
the supported catalyst is equal to or less than 30 % by weight, more
preferably equal to or less than 20 % by weight, sometimes even equal to
wo 2011/121058 PCT /EP2011/054980
8
or less than 10 % by weight, based on the weight of the catalyst. However,
it is possible to use the metal compound as such also as support, i.e. in
this case the content of metal compound may be up to 100 % by weight of
the catalyst. Often, the amount is adjusted so that the content of the metal
compound in the supported catalyst is preferably between 4 and 20 % by
weight. Often, a supported catalyst with 4 to 8% by weight metal
compound is produced.
[0044] According to the second preferred alternative, the organic metal
compound, preferably the barium compound, preferably in the form of a
solution, is first reacted in the sol-gel type reaction with the appropriate
amount of HF solution, preferably under stirring, followed by addition of the
respective support, whereby the materials used and their relative amounts
are as described above, especially in view of the alternative a).
[0045] After the reaction of the metal compound and HF to form the precursor has
taken place, be it after impregnation of the carrier according to the first
alternative, or before contact with the carrier according to the second
alternative, excessive solvent(s) is or are removed. Preferably, this is
performed in a gentle manner, preferably under vacuum. The removal
advantageously is supported by warming or heating. Preferably, the
temperature is equal to or higher than 25°C, more preferably, it is equal to
or higher than 30°C. Preferably, the temperature is equal to or lower than
200°C, more preferably, it is equal to or lower than 150°C. A preferred
range is 40 to 90°C. Both procedures a) or b) and subsequent solvent
removal provide a supported precursor.
[0046] The precursor already has catalytic activity. The catalytic activity can be
greatly enhanced if the precursor is activated by subsequent reaction with
a gaseous hydrochlorofluoroalkane at elevated temperature.
[0047] They can be applied in admixture with up to 95% (v/v), of an inert gas
such as nitrogen or a noble gas, preferably argon; the content of the inert
gas is preferably equal to or higher than 75 % (v/v); it is preferably equal to
or lower than to 90 % (v/v). Especially preferably, the inert gas content is
85 ± 5 % (v/v). The temperature in step A 1) preferably is equal to or higher
wo 2011/121058 PCT /EP2011/054980
9
than 150°C, more preferably, equal to or higher than 180°C. Preferably,
the temperature is equal to or lower than 400°C.
[0048] Whereas any hydrochlorofluoroalkane is principally suitable for the
activation step, it has proven advantageous in a number of cases to carry
out the activation with the same hydrochlorofluoroalkane which is the
substrate for the dehydrochlorination reaction. By doing so, the activation
can be carried out in-situ, i.e. immediately prior to the dehydrochlorination
reaction in the same reactor.
[0049] The activation can be monitored by elementary analysis of the reaction
mixture at various times. The chlorine content of the metal compound
increases up to a certain value at which it remains. Once the chlorine
content remains constant, the activation is completed. It can be assumed
that the fluoride precursor is chlorinated by virtue of HCI produced in the
dehydrochlorination of the hydrochlorofluoroalkane.
[0050] In a subsequent step, flushing is optionally performed to remove volatiles
from the catalyst. It is preferred to perform a flushing step. Flushing can be
stopped when the desired degree of purification has been achieved. It can
be performed for an extended time, for example, up to ten hours or more.
Preferably, flushing is performed for equal to or less than 6 hours.
Preferably, it is performed for equal to or more than 1 hour. The
temperature during flushing is preferably equal to or higher than 200°C.
Preferably, it is equal to or lower than 300°C. A temperature range of from
240°C and 260°C is very suitable.
[0051] The supported catalyst can be prepared in the form of a powder, in the
form of pellets, beads, extrudates and other formed bodies. Beads with a
diameter in the range of, for example, 1 to 10 mm are very suitable for the
dehydrochlorination process according to the instant invention.
[0052] The dehydrochlorination reaction in the process of the present invention
takes place very selectively and in high yields. The temperature at which
dehydrochlorination occurs depends on the respective starting compound.
Generally, the reaction temperature is equal to or higher than 50°C,
preferably equal to or higher than 120°C. The reaction can be performed
at even lower temperature, but in some cases, the speed of reaction may
wo 2011/121058 PCT /EP2011/054980
10
be considered to be too low. Generally, the reaction is performed at a
temperature equal to or lower than 300°C, preferably equal to or lower
than 250°C, and very preferably equal to or lower than 230°C. The
catalyst is very active for extended periods of time when the reaction
temperature is equal to or lower than 400°C. The result of the
dehydrochlorination is very good at temperatures e.g. above 1 00°C. The
long-term performance of the catalyst is especially good if it is operated at
temperatures equal to or below 400°C.
[0053] The reaction temperature is preferably equal to or higher than 120°C. The
speed of reaction can be accelerated if the reaction temperature is equal
to or higher than 150°C. Often, performing the reaction in a range of from
180°C to 250°C allows a high reaction speed with high conversion. A fast
reaction and high conversion are observed even if the dehydrochlorination
temperature is equal to or higher than 250°C.
[0054] Generally, the selectivity of the dehydrochlorination decreases slightly with
increasing temperature, i.e. at higher reaction temperatures
dehydrofluorination is increasingly observed. The skilled man will select
the reaction conditions so as to obtain the best conditions for the desired
conversion and selectivity.
[0055] Depending on the structure of the starting material in the
dehydrochlorination isomers may be formed, which can then be separated
by distillation, if required. In the dehydrochlorination of HCFC-364 having
the formula CH3-CFCI-CH2-CF3, for example, three isomers are formed
namely 1,1, 1 ,3-tetrafluorobut-3-ene and the E-and Z-isomers of 1,1, 1,3-
tetrafluoro-but-2-ene. With other starting materials the respective isomers
can be obtained.
[0056] In some cases, the balance between high reaction speed and high
selectivity may favour operation at relatively low reaction temperature.
[0057] If one observes diminishing catalyst activity, e.g. after long reaction
periods, or if the reaction temperature was selected too high, a
regeneration of the catalyst is possible. Oxidizing gases can be passed at
elevated temperatures through the reactor, e.g. air or oxygen. As is
wo 2011/121058 PCT /EP2011/054980
11
described below, the catalytic activity can be extended by passing a
hydrochlorofluoroalkane/nitrogen (or inert gas) mixture through the reactor.
[0058] The reaction can be performed batch wise or continuously. It is preferred
to operate in the gas phase, especially continuously.
[0059] If desired, the halogenated hydrocarbon used as starting material can be
diluted before the dehydrochlorination reaction with an inert gas, for
example, nitrogen, or a noble gas, for example, argon. In this case, the
halogenated hydrocarbon preferably is present in the gas mixture with
inert gas in an amount of equal to or more than 10 val.%. Preferably, it is
present in an amount of equal to or less than 75 val.%, more preferably in
an amount of equal to or less than 50 val.%, and especially preferably
equal to or less than 35 val.%. The productivity of the catalyst was in some
cases observed to be higher when using inert gas (nitrogen for example).
[0060] Accordingly, mixtures comprising or consisting of nitrogen and a
hydrochlorofluoroalkane with 2 to 5 carbon atoms in a molar ratio of
N2:hydrochlorofluoroalkane of (2-9): 1, preferably of (3-6): 1 can be passed
over the catalyst as described above. Mixtures comprising or consisting of
nitrogen and a hydrochlorofluoroalkane with 2 to 5 carbon atoms in a
molar ratio of N2:hydrochlorofluoroalkane of (3-5): 1 are especially
preferred. Especially preferred are mixtures comprising or consisting of N2
and a C3 or C4 hydrochlorofluoroalkane in a molar ratio of (2-9): 1,
preferably (3-6): 1, more preferably (3-5): 1.
[0061] The process in accordance with the instant invention yields the desired
products with good yield and with a good conversion. The products of the
dehydrochlorination can be used for various applications. Chlorine-free
end products obtained by dehydrochlorination of hydrochlorofluoroalkanes
with one chlorine atom are useful as such or after saturation of the double
bond as so called second-generation halogenated hydrocarbons.
[0062] Another aspect of the present invention is the use of a metal compound of
formula
(M 1 )x(M2)1-xCI1+yF 1-y
wherein
M1 is selected from the group consisting of Ca, Sr and Ba
wo 2011/121058
12
x is in the range of from 0.2 to 1.0 and
y is in the range of from -0.8 to 0.8.
PCT /EP2011/054980
as a catalyst for the selective dehydrochlorination of
hydrochlorofluoroalkanes. Preferred metal compounds, starting
compounds, reaction products and reaction conditions are those given
above.
[0063] Should the disclosure of any patents, patent applications, and publications
which are incorporated herein by reference conflict with the description of
the present application to the extent that it may render a term unclear, the
present description shall take precedence.
[0064] Examples
[0065] Catalytically active Barium compounds were prepared in accordance with
the so-called water-free fluorolytic Sol-Gel method in accordance with
Kemnitz, E. et al., "Amorphe Metallfluoride mit aussergewohnlich grosser
spezifischer Oberflache", Angew. Chem. 2003, 115(35) and Rudiger, S.
and Kemnitz, E., "The fluorolytic sol-gel method to metal fluorides- a
versatile process opening up a variety of application fields, Dalton Trans.
2008, pp. 1117-1127.
[0066] In the first step a respective Ba precursor compound was reacted with HF
in methanol. Thereby sol- or gel-like network structures were obtained.
Thereafter the volatile substances were removed by drying at 100 oc
under vacuum for two hours.
[0067] The resulting Xerogel (BaF2) was then subjected to a gas-phase activation
with 3-chloro-1, 1,1 ,3-tetrafluorobutane (S-364) at a temperature of 200 °C.
[0068] The carbon content of the BaF2 was very low, indicating that the organic
components formed during its synthesis had been substantially completely
removed during the subsequent drying process.
[0069] The chlorine content of the product increased initially rapidly from 0 to 10.4
wt.% within two hours, reaching a constant value of 13.4 wt.% after 20
hours. A chlorine content of 13.4 wt.% corresponds to a stoichiometric
formula BaCio.7F1.3, i.e. yin this experiment had a value of -0.3 and x was
1.
wo 2011/121058 PCT /EP2011/054980
13
[0070] The catalytic dehydrochlorination of 3-chloro-1, 1,1 ,3-tetrafluorobutane (S-
364) was carried out as follows:
A heatable quartz reactor having an internal diameter of 8 mm and an
external diameter of 10 mm was filled with 200 mg of the respective
catalytically active compound which was fixed in the middle of the reactor
by quartz wool plugs. A gas stream of 25 ml/min of a mixture of 3-chloro-
1, 1,1 ,3-tetrafluorobutane and nitrogen (volume ratio 1:4) was introduced
into the reactor which was kept at a temperature of 150, 200 or 230 °C.
After passage through the reactor, the gas stream was carried through a
0.5 molar solution of sodium hydrogen carbonate to neutralize the
gaseous acids produced during the reaction (HCI, SiF4). Thereafter
samples were taken which were analyzed directly by gas chromatography
and GC-MS respectively (in this case the gas stream was condensed in
trichloromethane for injection into the GC-MS system).
[0071] Conversion at 200 and 230°C was approximately 95% whereas at 150 oc
conversion dropped to 20-40 %.
[0072] Table 1 shows the results of the dehydrochlorination at the respective
temperatures and the relative selectivity towards the three possible
products Z- and E-1, 1,1 ,3-tetrafluorobut-2-ene (TFBE1 and TFBE2
respectively) and 1,1, 1 ,3-tetrafluorobut-3-ene (TFBE3). Selectivity for
dehydrochlorination denotes the percentage of dehydrochlorinated
products in the reaction mixture, the remainder being dehydrofluorinated
products.
Table 1
Temperature Selectivity Selectivity Selectivity Selectivity
oc TFBE1 TFBE1 TFBE1 dehydrochlorination
150 0.24 0.13 0.57 0.94
200 0.12 0.10 0.73 0.95
230 0.10 0.09 0.69 0.88
wo 2011/121058 PCT /EP2011/054980
14
[0073] The results show that selectivity slightly decreased with increasing
temperature. Due to the significantly lower conversion at 150°C as
indicated above, the margin of error of the values at this temperature is
higher than at 200 and 230°C as there is a significant amount of starting
material in the reaction mixture.
[0074] In a second row of experiments at 200°C, the flow rate of the gas stream
comprising 3-chloro-1, 1,1 ,3-tetrafluorobutane and nitrogen was increased
to 50 ml/min, thereby reducing the contact time from 0.5 s to 0.25 s. The
conversion dropped to 70-75 % whereas the selectivity towards
dehydrochlorination was not affected significantly.
[0075] Further embodiments of the instant invention by modifying the reaction
conditions or the compositions of the catalytically active metal compound
are evident to the skilled man.

Claims
1. A process for the catalytic dehydrochlorination of hydrochlorofluoroalkanes
comprising at least one chlorine atom, at least one fluorine atom and at least
one hydrogen atom on a carbon atom vicinal to the carbon atom or carbon
atoms carrying the at least one chlorine and at least one fluorine atom by
contacting the hydrochlorofluoroalkane with a metal compound of formula
(M 1 )x(M2)1-xCI1 +yF 1-y
wherein
M1 and M2 are selected from the group consisting of Ca, Sr and Ba
x is in the range of from 0.2 to 1.0 and
y is in the range of from -0.8 to 0.8.
2. A process in accordance with claim 1 wherein y is in the range of from -0.6. to
0.6.
3. A process in accordance with claim 2 wherein y is in the range of from -0.6 to
0.
4. A process in accordance with at least one of claims 1 to 3 wherein xis at least
0.5.
5. A process in accordance with claim 4 wherein x is at least 0.8.
6. A process in accordance with claim 5 wherein x is 1.
7. A process in accordance with at least one of claims 1 to 6 wherein M1 isBa.
8. A process in accordance with at least one of claims 1 to 7 wherein the
catalytically active metal compound is obtained by
a) providing a precursor, optionally on a support, wherein the precursor
comprises a structure having the formula (M 1 )x(M2)1-xF2-o-dBdle and
b) activating the precursor with a hydrochlorofluoroalkane generating the
catalytically active metal compound,
wherein B is a co-ordinately bound group; L is an organic solvent; xis in the
range of from 0.2 to 1.0, d is any integer in the range of from 0 to 3, e has a
value in the range of from 0 to 1 and o has a value in the range of from 0 to
0.1, provided that the denominators representing the number of chlorine and
fluorine atoms are positive.
wo 2011/121058
16
9. Use of a metal compound of formula
(M 1 )x(M2)1-xCI1+yF 1-y
wherein
M1 is selected from the group consisting of Ca, Sr and Ba
x is in the range of from 0.2 to 1.0 and
y is in the range of from -0.8 to 0.8.
PCT /EP2011/054980
as a catalyst for the selective dehydrochlorination of hydrochlorofluoroalkanes.