Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
HIGH SELECTIVITY PROCESS TO MAKE DIHYDROFLUOROALKENES
BACKGROUND INFORMATION
FIELD OF THE DISCLOSURE
This disclosure relates in general to the synthesis of
hydrofluoroolefins.
DESCRIPTION OF THE RELATED ART
The fluorocarbon industry has been working for the past few
decades to find replacement refrigerants for the ozone depleting
chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) being
phased out as a result of the Montreal Protocol. The solution for many
applications has been the commercialization of hydrofluorocarbon (HFC)
compounds for use as refrigerants, solvents, fire extinguishing agents,
blowing agents and propellants. These new compounds, such as HFC
refrigerants, HFC-1 34a being the most widely used at this time, have zero
ozone depletion potential and thus are not affected by the current
regulatory phase-out as a result of the Montreal Protocol.
In addition to ozone depleting concerns, global warming is another
environmental concern in many of these applications. Thus, there is a
need for compositions that meet both low ozone depletion standards as
well having low global warming potentials. Certain hydrofluoroolefins are
believed to meet both goals. Thus there is a need for manufacturing
processes that provide halogenated hydrocarbons and fluoroolefins that
contain no chlorine that also have a low global warming potential.
SUMMARY
In one embodiment the process is a method for the synthesis of
fluorinated alkenes comprising contacting a fluorinated alkyne of the
formula R'-C=C-R2, wherein R1 and R2 are independently selected from
CF33 C2F5, C3F7, and C4F9, in a pressure vessel, with a Lindlar catalyst,
with substantially up to and including one molar equivalent of hydrogen, to
make the corresponding cis or trans-alkene of formula R1HC=CHR 2 with
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high selectivity, wherein said hydrogen is added in portions over a period
of time, so as to produce an initial pressure in the vessel of no more than
about 100 psi.
In another embodiment, the process is a method for the synthesis
of fluorinated alkenes comprising: contacting a fluorinated alkyne of the
formula R1C=CR2, wherein R, and R2 are independently selected from
CF3, C2F5, C3F7, and C4F9 in a pressure vessel, in a solvent, with a Lindlar
catalyst, with substantially one molar equivalent of hydrogen, to make the
corresponding cis-alkene of formula R'HC=CH R2 with high selectivity.
In yet another embodiment, the process is a method for
synthesizing fluorinated alkenes in a continuous process, contacting a
fluorinated alkyne of the formula R1 C=C R2, wherein R1 and R2 are
independently selected from CF3, C2F5, C3F7, and C4F9, in a reaction zone,
in the gas phase with substantially one equivalent or less of hydrogen in
the presence of a Lindlar catalyst.
The foregoing general description and the following detailed
description are exemplary and explanatory only and are not restrictive of
the invention, as defined in the appended claims.
DETAILED DESCRIPTION
In one embodiment, the process is a method for the synthesis of
fluorinated alkenes from the corresponding fluorinated alkynes in high
selectivity by selective hydrogenation in the presence of particular
catalysts.
Many aspects and embodiments have been described above and
are merely exemplary and not limiting. After reading this specification,
skilled artisans appreciate that other aspects and embodiments are
possible without departing from the scope of the invention.
Other features and benefits of any one or more of the embodiments will be
apparent from the following detailed description, and from the claims.
Before addressing details of embodiments described below, some
terms are defined or clarified.
As used herein, the terms "comprises," "comprising," "includes,"
"including," "has," "having" or any other variation thereof, are intended to
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cover a non-exclusive inclusion. For example, a process, method, article,
or apparatus that comprises a list of elements is not necessarily limited to
only those elements but may include other elements not expressly listed or
inherent to such process, method, article, or apparatus. Further, unless
expressly stated to the contrary, "or" refers to an inclusive or and not to an
exclusive or. For example, a condition A or B is satisfied by any one of the
following: A is true (or present) and B is false (or not present), A is false
(or not present) and B is true (or present), and both A and B are true (or
present).
Also, use of "a" or "an" are employed to describe elements and
components described herein. This is done merely for convenience and to
give a general sense of the scope of the invention. This description
should be read to include one or at least one and the singular also
includes the plural unless it is obvious that it is meant otherwise.
Group numbers corresponding to columns within the Periodic Table
of the elements use the "New Notation" convention as seen in the CRC
Handbook of Chemistry and Physics, 81 st Edition (2000-2001).
As used herein, a reaction zone may be a reaction vessel
fabricated from nickel, iron, titanium or their alloys, as described in U. S.
Patent No. 6,540,933, incorporated herein by reference. A reaction vessel
of these materials (e.g., a metal tube) may also be used. When reference
is made to alloys, it is meant a nickel alloy containing from about 1 to
about 99.9 weight percent nickel, an iron alloy containing about 0.2 to
about 99.8 weight percent iron, and a titanium alloy containing about 72 to
about 99.8 weight percent titanium. Of note is the use of a tube such as
above, packed with a Lindlar catalyst made of nickel or alloys of nickel
such as those containing about 40 weight percent to about 80 weight
percent nickel, e.g., InconelTM 600 nickel alloy, HastelloyTM C617 nickel
alloy or HastelloyTM C276 nickel alloy.
A Lindlar catalyst is a heterogeneous palladium catalyst on a
calcium carbonate support, which has been deactivated or conditioned
with a lead compound. The lead compound can be lead acetate, lead
oxide, or any other suitable lead compound. In one embodiment, the
catalyst is prepared by reduction of a palladium salt in the presence of a
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slurry of calcium carbonate, followed by the addition of the lead
compound. In one embodiment, the palladium salt in palladium chloride.
In another embodiment, the catalyst is deactivated or conditioned with
quinoline. The amount of palladium on the support is typically 5% by
weight but may be any catalytically effective amount.
Unless otherwise defined, all technical and scientific terms used
herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although methods
and materials similar or equivalent to those described herein can be used
in the practice or testing of embodiments of the present invention, suitable
methods and materials are described below. All publications, patent
applications, patents, and other references mentioned herein are
incorporated by reference in their entirety, unless a particular passage is
cited. In case of conflict, the present specification, including definitions,
will control. In addition, the materials, methods, and examples are
illustrative only and not intended to be limiting.
In one embodiment, fluorinated alkenes are synthesized by
contacting fluorinated alkynes of the structure R1 C=C R2, wherein R1 and
R2 are independently selected from CF3, C2F5, C3F7, and C4F9 with
hydrogen in the presence of a selective catalyst. Representative
fluorinated alkynes include alkynes selected from the group consisting of
hexafluoro-2-butyne, octafluoro-2-pentyne, decafluoro-2-hexyne,
decafluoro-3-hexyne, dodecafluoro-2-heptyne, dodecafluoro-3-heptyne,
tetrad ecafluoro-3-octyne and tetrad ecafluoro-4-octyne.
Hexafluoro-2-butyne is readily available by dechlorination of
1,1,1,4,4,4-hexafluoro-2,3-dichloro-2-butene (CFC-1316mxx) with zinc.
CFC-1316mxx is readily prepared from CF3CC13 as disclosed in U.S.
Patent 5,919,994, which disclosure is herein incorporated by reference.
Similarly, decafluoro-3-hexyne is readily prepared from
CF3CF2CCI=CCICF2CF3 by dechlorination with zinc.
CF3CF2CCI=CCICF2CF3 is similarly prepared from CF3CF2CC13. Similarly,
decafluoro-2-hexyne is readily prepared from CF3CCI=CCICF2CF2CF3,
which is readily prepared from CFC-1316mxx via reaction with
tetrafluoroethylene in the presence of an aluminum chlorofluoride catalyst.
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Octafluoro-2-pentyne can be prepared from 1,1,1,2,2,3,4,5,5,5-
decafluoropentane by dehydofluroinating twice in the presence of base, or
zeolites, as disclosed in Japanese patent 2004292329.
In one embodiment, the catalyst of the process is a Lindlar catalyst.
In one embodiment, the amount of the catalyst used is from about 0.5% by
weight to about 4% by weight of the amount of the fluorinated alkyne. In
another embodiment, the amount of the catalyst used is from about 1 % by
weight to about 3% by weight of the amount of the fluorinated alkyne. In
yet another embodiment, the amount of the catalyst used is from about 1 %
to about 2% by weight of the amount of the fluorinated alkyne.
In some embodiments, the reaction is conducted in a solvent. In
one such embodiment, the solvent is an alcohol. Typical alcohol solvents
include ethanol, i-propanol and n-propanol. In another embodiment, the
solvent is a fluorocarbon or hydrofluorocarbon. Typical fluorocarbons or
hydrofluorocarbons include 1,1,1,2,2,3,4,5,5,5-decafluoropentane and
1,1,2,2,3,3,4-heptafluorocyclopentane.
In one embodiment, the process is conducted in a batchwise
process.
In another embodiment, the process is conducted in a continuous
process in the gas phase.
In one embodiment, reaction of the fluorinated alkynes with
hydrogenation in the presence of the catalyst should be done with addition
of hydrogen in portions, with increases in the pressure of the vessel of no
more than about 100 psi with each addition. In another embodiment, the
addition of hydrogen is controlled so that the pressure in the vessel
increases no more than about 50 psi with each addition. In one
embodiment, after enough hydrogen has been consumed in the
hydrogenation reaction to convert at least 50% of the fluorinated alkyne to
alkene, hydrogen can be added in larger increments for the remainder of
the reaction. In another embodiment, after enough hydrogen has been
consumed in the hydrogenation reaction to convert at least 60% of the
fluorinated alkyne to alkene, hydrogen can be added in larger increments
for the remainder of the reaction. In yet another embodiment, after
enough hydrogen has been consumed in the hydrogenation reaction to
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convert at least 70% of the fluorinated alkyne to alkene, hydrogen can be
added in larger increments for the remainder of the reaction. In one
embodiment, the larger increments of hydrogen addition can be 300 psi.
In another embodiment, the larger increments of hydrogen addition can be
400 psi.
In one embodiment, the amount of hydrogen added is about one
molar equivalent per mole of fluorinated alkyne. In another embodiment,
the amount of hydrogen added is from about 0.9 moles to about 1.3
moles, per mole of fluorinated alkyne. In yet another embodiment, the
amount of hydrogen added is from about 0.95 moles to about 1.1 moles,
per mole of fluorinated alkyne. In yet another embodiment, the amount of
hydrogen added is from about 0.95 moles to about 1.03 moles, per mole
of fluorinated alkyne.
In one embodiment, the hydrogenation is performed at ambient
temperature. In another embodiment, the hydrogenation is performed at
above ambient temperature. In yet another embodiment, the
hydrogenation is performed at below ambient temperature. In yet another
embodiment, the hydrogenation is performed at a temperature of below
about 0 C.
In an embodiment of a continuous process, a mixture of fluorinated
alkyne and hydrogen are passed through a reaction zone containing the
catalyst. In one embodiment, the molar ratio of hydrogen to fluorinated
alkyne is about 1:1. In another embodiment of a continuous process, the
molar ratio of hydrogen to fluorinated alkyne is less than 1:1. In yet
another embodiment, the molar ratio of hydrogen to fluorinated alkyne is
about 0.67:1Ø
In one embodiment of a continuous process, the reaction zone is
maintained at ambient temperature. In another embodiment of a
continuous process, the reaction zone is maintained at a temperature of
30 C. In yet another embodiment of a continuous process, the reaction
zone is maintained at a temperature of about 40 C.
In one embodiment of a continuous process, the flow rate of
fluorinated alkyne and hydrogen is maintained so as to provide a
residence time in the reaction zone of about 30 seconds. In another
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embodiment of a continuous process, the flow rate of fluorinated alkyne
and hydrogen is maintained so as to provide a residence time in the
reaction zone of about 15 seconds. In yet another embodiment of a
continuous process, the flow rate of fluorinated alkyne and hydrogen is
maintained so as to provide a residence time in the reaction zone of about
7 seconds.
It will be understood, that contact time in the reaction zone is
reduced by increasing the flow rate of fluorinated alkyne and hydrogen into
the reaction zone. As the flow rate is increased this will increase the
amount of fluorinated alkyne being hydrogenated per unit time. Since the
hydrogenation is exothermic, depending on the length and diameter of the
reaction zone, and its ability to dissipate heat, at higher flow rates it may
be desirable to provide a source of external cooling to the reaction zone to
maintain a desired temperature.
In one embodiment of a continuous process, the amount of
palladium on the support in the Lindlar catalyst is 5% by weight. In
another embodiment, the amount of palladium on the support in the
Lindlar catalyst is greater than 5% by weight. In yet another embodiment,
the amount of palladium on the support can be from about 5% by weight to
about 1 % by weight.
In one embodiment, upon completion of a batch-wise or continuous
hydrogenation process, the cis-dihydrofluoroalkene can be recovered
through any conventional process, including for example, fractional
distillation. In another embodiment, upon completion of a batch-wise or
continuous hydrogenation process, the cis-dihydrorofluoroalkene is of
sufficient purity to not require further purification steps.
EXAMPLES
The concepts described herein will be further described in the
following examples, which do not limit the scope of the invention
described in the claims.
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Example 1
Example 1 demonstrates the selective hydrogenation of hexafluoro-
2-butyne.
5g of Lindlar (5% Pd on CaCO3 poisoned with lead) catalyst was
charged in 1.3 L rocker bomb. 480g (2.96mole) of hexafluoro-2-butyne
was charged in the rocker. The reactor was cooled down (-78 C) and
evacuated. After the bomb was wormed up to room temperature, H2 was
added slowly, by increments which did not exceed Ap= 50psi. A total of 3
moles H2 were added to the reactor. A gas chromatographic analysis of
the crude product indicated the mixture consisted of CF3C=CCF3
(0.236%), trans-isomer of CF3CH=CHCF3 (0.444%), saturated
CF3CH2CH2CF3 (1.9%) CF2=CHCI, impurity from starting butyne,
(0.628%), cis-isomer of CF3CH=CHCF3 (96.748%). Distillation afforded
287g (59%yield) of 100% pure cis-CF3CH=CHCF3 (boiling point 33.3 C).
MS: 164 [MI], 145 [M-19], 95 [CF3CH=CH], 69 [CF3]. NMR H1: 6.12 ppm
(multiplet), F19: -60.9 ppm (triplet J=0.86Hz)
Example 2
Example 2 demonstrates the hydrogenation of hexafluoro-2-butyne
with 2% catalyst by weight.
Into a 1.31 Hastelloy reactor 1 Og of Lindlar catalyst was loaded.
Then, hexafluoro-2-butyne 500g (3.08mole) was added to the reactor.
Hydrogen was added by small increments of 50-100psi. A total of 1100psi
of hydrogen was added in total. (3.08 mole) Hydrogen was consumed at
the rate of 150psi/hr average during 6.5hrs. Analysis of the product by
gas chromatography indicated that 93.7% of hexafluorobutyne was
converted into cis-CF3CH=CHCF3, with 4.8% of saturated CF3CH2CH2CF3.
Example 3
Example 3 demonstrates the hydrogenation of octafluoro-2-pentyne
with 1 % catalyst by weight.
Into a 1.31 Hastelloy reactor 1 Og of Lindlar catalyst is loaded. Then,
octafluoro-2-pentyne 650g (3.06mole) is added to the reactor. Hydrogen is
then added slowly, by increments which do not exceed Ap= 50psi. A total
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of 3 moles H2 is added to the reactor. Analysis of the product by gas
chromatography indicated that 96.7% of octafluoro-2-pentyne is converted
into cis-CF3CH=CHCF2CF3, with 1.8% of saturated CF3CH2CH2CF2CF3.
Example 4
Example 4 demonstrates the hydrogenation of hexafluoro-2-butyne
with 1 % catalyst by weight.
Into a 1.31 Hastelloy reactor 5g of Lindlar catalyst was loaded.
Then, hexafluoro-2-butyne 500g (3.08mole) was added to the reactor.
Hydrogen was added by small increments of 30-50psi. 1414psi was added
total (4.0 moles hydrogen). Hydrogen was consumed at the rate of
50psi/hr average during 28hrs. Analysis of the resulting product mixture
indicated 80.7% cis-CF3CH=CHCF3, and 19.3% saturated CF3CH2CH2CF3
Example 5
Example 5 demonstrates the hydrogenation of decafluoro-3-
hexyne.
Into a 1.31 Hastelloy reactor 8 g of Lindlar catalyst is loaded. Then,
decafluoro-3-hexyne 800 g (3.05mole) is added to the reactor. Hydrogen
is then added slowly, by increments which do not exceed Ap= 50psi. A
total of 3 moles H2 is added to the reactor. Analysis of the product by gas
chromatography indicated that 96.7% of decafluoro-3-hexyne is converted
into cis-CF3CF2CH=CHCF2CF3, with 1.8% of saturated
CF3CF2CH2CH2CF2CF3.
Example 6
Example 6 demonstrates the hydrogenation of hexafluoro-2-butyne
in a continuous process to produce a mixture of cis- and trans-1,1,1,4,4,4-
hexafluoro-2-butene.
A Hastelloy tube reactor 10" long with a 5" O.D. (outside diameter)
and 0.35" wall thickness was filled with 10 g of Lindlar catalyst. The
catalyst was conditioned at 70 C with a flow of hydrogen for 24 hours.
Then a flow of a 1:1 mole ratio of hexafluoro-2-butyne and hydrogen was
passed through the reactor at 30 C at a flow rate sufficient to provide a 30
second contact time. The product mixture was collected in a cold trap
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after exiting the reactor and analyzed by gas chromatography. The
product mixture was found to contain CF3CH=CHCF3 (cis) (72%),
CF3CH=CHCF3 (trans) (8.8%), CF3CH2CH2CF3 (7.8%) and CF3C=CCF3
(3.3%).
Example 7
Example 7 demonstrates the hydrogenation of hexafluoro-2-butyne
in a continuous process with a 15 second contact time.
The procedure of example 6 was followed, with the exception that
the flow rate was adjusted to provide a contact time of 15 seconds. The
reaction was slightly exothermic, with the reactor warming to 35-36 C.
Analysis of the product mixture indicated CF3CH=CHCF3 (cis) (72%),
CF3CH=CHCF3 (trans) (9.3%), CF3CH2CH2CF3 (11.3%) and CF3C=CCF3
(3.9%).
Example 8
Example 8 demonstrates the hydrogenation of hexafluoro-2-butyne
in a continuous process with a hydrogen:alkyne mole ratio of 0.67:1.
The procedure of example 6 was followed, with the exception that
the mole ratio of hydrogen:hexafluoro-2-butyne fed to the reactor was
0.67:1Ø Analysis of the product mixture indicated CF3CH=CHCF3 (cis)
(65.3%), CF3CH=CHCF3 (trans) (4.4%), CF3CH2CH2CF3 (3.4%) and
CF3C=CCF3 (23.5%).
Example 9
Example 9 demonstrates the hydrogenation of hexafluoro-2-butyne
in a continuous process with a 7 second contact time.
The procedure of example 6 was followed, with the exception that
the flow rate was adjusted to provide a contact time of 7 seconds. The
reaction was slightly exothermic, with the reactor warming to 42 C.
Analysis of the product mixture indicated CF3CH=CHCF3 (cis) (72.5%),
CF3CH=CHCF3 (trans) (8.7%), CF3CH2CH2CF3 (8.6%) and CF3C=CCF3
(6.9%).
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Comparative Example 1
Into a 400m1 Hastelloy shaker tube was loaded with 2g of Lindlar
catalyst, 30g of hexafluoro-2-butyne. The shaker was pressurized up to
300psi with H2. The pressure suddenly rose to 4000 psi, and the
temperature of the reactor contents went up to 70 C. Black powder was
recovered as a product.
Comparative Example 2
Into a 1.31 Hastelloy reactor 10g of Lindlar catalyst was loaded.
Then, hexafluoro-2-butyne 500g (3.08mole) was added to the reactor.
Hydrogen was added by small increments of 30-50psi. 2385psi was added
total. At the rate 40psi/hr average. Hydrogen was consumed at the rate of
35psi/hr average during 60hrs. As a result 89% of hexafluoro-2-butyne
was converted into saturated CF3CH2CH2CF3, 7.7% of unsaturated cis-
CF3CH=CHCF3 was detected in the mixture of products.
Comparative Example 3
Into Hastelloy 210m1 shaker tube 1 g of Raney Ni was placed. After
the reactor was cool 25 g (0.154mole) of hexafluoro-2-butyne was added.
The reactor was pressurized to 150psi (approx., 0.09mole) with H2 at
ambient temperature. The reactor was then heated to 50 C. The pressure
went up to 299psi at 52 C and the following one hour dropped only 14 psi.
After increasing temperature to 90 C, the pressure dropped to 214psi and
didn't change during 3 additional hours. After carefully venting the
remaining pressure, 20g of crude product mixture was recovered. The
mixture contained 86% of starting hexafluoro-2-butyne, 8.375% of
saturated CF3CH2CH2CF3 and 5.6 % of cis- CF3CH=CHCF3.
Note that not all of the activities described above in the general
description or the examples are required, that a portion of a specific
activity may not be required, and that one or more further activities may be
performed in addition to those described. Still further, the order in which
activities are listed are not necessarily the order in which they are
performed.
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In the foregoing specification, the concepts have been described
with reference to specific embodiments. However, one of ordinary skill in
the art appreciates that various modifications and changes can be made
without departing from the scope of the invention as set forth in the claims
below. Accordingly, the specification and figures are to be regarded in an
illustrative rather than a restrictive sense, and all such modifications are
intended to be included within the scope of invention.
Benefits, other advantages, and solutions to problems have been
described above with regard to specific embodiments. However, the
benefits, advantages, solutions to problems, and any feature(s) that may
cause any benefit, advantage, or solution to occur or become more
pronounced are not to be construed as a critical, required, or essential
feature of any or all the claims.
It is to be appreciated that certain features are, for clarity, described
herein in the context of separate embodiments, may also be provided in
combination in a single embodiment. Conversely, various features that
are, for brevity, described in the context of a single embodiment, may also
be provided separately or in any subcombination. Further, reference to
values stated in ranges include each and every value within that range.
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