U.S. patent application number 12/770217 was filed with the patent office on 2011-11-03 for process for dehydrohalogenation of halogenated alkanes.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to Yuon Chiu, George R. Cook, Stephen A. Cottrell, Haluk Kopkalli, Daniel C. Merkel, Peter Scheidle.
Application Number | 20110269999 12/770217 |
Document ID | / |
Family ID | 44858759 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110269999 |
Kind Code |
A1 |
Cook; George R. ; et
al. |
November 3, 2011 |
PROCESS FOR DEHYDROHALOGENATION OF HALOGENATED ALKANES
Abstract
A process for the manufacture of halogenated olefins in
semi-batch mode by dehydrohalogenation of halogenated alkanes in
the presence of an aqueous base such as KOH which simultaneously
neutralizes the resulting hydrogen halide. During the process,
aqueous base is continuously added to the haloalkane which results
in better yields, lower by-product formation and safer/more
controllable operation.
Inventors: |
Cook; George R.; (Buffalo,
NY) ; Kopkalli; Haluk; (Staten Island, NY) ;
Cottrell; Stephen A.; (Baton Rouge, LA) ; Chiu;
Yuon; (Denville, NJ) ; Scheidle; Peter;
(Wheatfield, NY) ; Merkel; Daniel C.; (Orchard
Park, NY) |
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
44858759 |
Appl. No.: |
12/770217 |
Filed: |
April 29, 2010 |
Current U.S.
Class: |
570/155 ;
570/153 |
Current CPC
Class: |
C07C 17/25 20130101;
C07C 17/23 20130101; C07C 17/25 20130101; C07C 21/18 20130101 |
Class at
Publication: |
570/155 ;
570/153 |
International
Class: |
C07C 21/18 20060101
C07C021/18 |
Claims
1. A process for preparing a hydrofluoroolefin comprising: a.
introducing an alkali-metal hydroxide feed stream into a reactor
charged with at least one halogenated propane having a structure
according to Formula I: C.sub.3F.sub.xCl.sub.yH.sub.8-x-y (Formula
I) wherein x is 5 or 6 and y is 0 or 1, provided that x+y is
.ltoreq.6; b. reacting, in a liquid phase, said halogenated propane
with said an aqueous base in said reactor to produce a halogenated
propene having a structure according to Formula II:
C.sub.3F.sub.z-1H.sub.7-z (Formula I) wherein z is x-1; and c.
removing at least a portion of said halogenated propene from said
reactor as a vapor product stream, wherein steps (a), (b), and (c)
are at least partially performed simultaneously.
2. The process of claim 1 wherein x+y is 6 and said halogenated
propene is HFO-1225.
3. The process of claim 2 wherein said halogenated propane is
HFCF-235fa and said halogenated propene is HFO-1225zc.
4. The process of claim 2 wherein said halogenated propane is
HFCF-236fa and said halogenated propene is HFO-1225zc.
5. The process of claim 2 wherein said halogenated propane is
HFCF-236ea and said halogenated propene is HFO-1225ye.
6. The process of claim 1 wherein x+y is 5 and said halogenated
propene is HFO-1234.
7. The process of claim 6 wherein said halogenated propane is
HFCF-245eb and said halogenated propene is HFO-1234yf.
8. The process of claim 1 further comprises refluxing at least a
portion of unreacted halogenated propane in said vapor product
stream back to said reactor.
9. The process of claim 8 further comprises refluxing water in said
vapor product stream back to said reactor.
10. The process of claim 1 wherein said reacting occurs at a
temperature of about 40 to about 75.degree. C.
11. The process of claim 10, wherein said reacting occurs at a
temperature of about 50 to about 60.degree. C.
12. The process of claim 1, wherein said aqueous base is an alkali
metal hydroxide.
13. The process of claim 12, wherein said alkali metal hydroxide is
potassium hydroxide.
14. The process of claim 13, wherein potassium hydroxide is present
in a concentration of about 10 to about 50 wt. %.
15. A process for dehydrohalogenating a compound comprising: a.
providing a reaction admixture comprising potassium hydroxide and a
halogenated propane having a degree of halogenation of M; and b.
reacting said potassium hydroxide with said halogenated propane to
form a halogenated propene having a degree of halogenation of
M-1.
16. The process of claim 15 wherein M is 5 or 6.
17. The process of claim 16 wherein said halogenated propane is at
least pentafluorinated.
18. The process of claim 17 wherein said product is a
hydrofluoroolefin.
Description
BACKGROUND
[0001] 1. Field of Invention
[0002] This invention relates to processes for producing
hydrofluoroolefins. More particularly, this process relates to
processes for producing hydrofluoroolefins via
dehydrohalogenation.
[0003] 2. Description of Related Art
[0004] Certain hydrofluoroolefins (HFOs), such as HFO-1225zc,
HFO-1234yf and HFO-1234ze, have zero ozone depletion potential and
have very low global-warming potential such that they are desirable
replacement for hydrofluorocarbons (HFCs) such as HFC-134a and
HFC-245fa in applications such as refrigeration, foam blowing,
etc.
[0005] One method for synthesizing hydrofluoroolefins involves
dehydrohalogenation of a halogenated alkane, such as
hydrofluorocarbons and hydrochlorofluorocarbons (HCFCs). Such
dehydrohalogenation reactions can occur as a liquid or gas phase
reaction.
[0006] For liquid phase dehydrohalogenation reactions, one method
involves reacting the HCFC or HFC in the presence of a KOH solution
which simultaneously neutralizes the HF or HCl according to the
reactions below:
HCFC-235fa+KOH(aq).fwdarw.HFO-1225zc+KCl(aq)+Water
HFC-236fa+KOH(aq).fwdarw.HFO-1225zc+KF(aq)+Water
HFC-236ea+KOH(aq).fwdarw.HFO-1225ye(E)+HFO-1225ye(Z)+KF(aq)+Water
HFC-245eb+KOH(aq).fwdarw.HFO-1234yf+KF(aq)+Water
HFC-245fa+KOH(aq).fwdarw.HFO-1234ze(E)+HFO-1234ze(Z)+KF(aq)+Water
[0007] Conventionally, such liquid phase reactions are performed as
a batch process wherein the reactants are charged into a batch
reactor without regard to their order of addition. Typically, the
charged reactants are allowed to react for a period of time
followed by recovery of the product. This mode of operation results
in long batch times as well as large amounts of moisture in the
crude product. Hence there is a need to design a more economical
and more effective means of carrying out the above reactions.
SUMMARY OF THE INVENTION
[0008] It has been discovered that for liquid phase
dehydrohalogenation reactions involving an aqueous base, the order
in which the reactants are charged into a reactor affects the
product yield and composition. Moreover, it has been discovered
that limiting the amount of aqueous based in the reaction admixture
can increase the product yield and selectivity.
[0009] Accordingly, provided is a process for preparing a
hydrofluoroolefin comprising the following steps: (a) introducing
an alkali-metal hydroxide feed stream into a reactor precharged
with at least one halogenated propane having a structure according
to Formula I:
C.sub.3F.sub.xCl.sub.yH.sub.8-x-y (Formula I)
wherein x is 5 or 6 and y is 0 or 1, provided that x+y is
.ltoreq.6; (b) reacting, in a liquid phase, said halogenated
propane with said an aqueous base in said reactor to produce a
halogenated propene having a structure according to Formula II:
C.sub.3F.sub.z-1H.sub.7-z (Formula I)
wherein z is x-1; and (c) removing at least a portion of said
halogenated propene from said reactor as a vapor product stream,
wherein steps (a), (b), and (c) are at least partially performed
simultaneously.
[0010] Also provided is a process for dehydrohalogenating a
compound comprising: (a) providing a reaction admixture comprising
potassium hydroxide and a halogenated propane having a degree of
halogenation of M; (b) reacting said potassium hydroxide with said
halogenated propane to form a halogenated propene having a degree
of halogenation of M-1.
BRIEF DESCRIPTION OF THE DRAWING
[0011] FIG. 1 shows a dehydrohalogenation system according to a
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTIONS
[0012] This invention provides for a more effective method for
dehydrofluorination of certain hydrofluorocarbons and
hydrochlorofluorocarbons in the presence of aqueous base. In
certain preferred embodiments, this method is a semi-batch process
having the following general steps: (a) precharging all or a
portion of an organic reactant, e.g., unsaturated starting
material, into a reactor, such as a stirred tank reactor; (b)
optionally heating the contents of the reactor to a desired
reaction temperature; (c) forming a reaction admixture by
continuously adding an aqueous base to the organic reactant,
wherein the aqueous base is continuously added during a reaction
cycle so it is consumed immediately (or almost immediately) so as
not to build up a concentration of aqueous base in the admixture
(d) reacting the organic reactant with the aqueous base to produce
a vapor phase dehydrohalogenated product; (e) separating the
resulting vapor phase product from the reaction admixture; and (f)
passing the reaction vapors through a rectifying column and a
condenser while (1) refluxing unreacted starting material and
moisture back to the reactor (2) allowing a predominantly pure
product to leave the system as a vapor. At the end of the reaction
cycle when the majority of the organic reactant is exhausted, the
reactor contents may be heated further to drive off additional
organic from the aqueous phase followed by draining the reactor to
prepare for the next batch.
[0013] In certain preferred embodiments, the organic reactant
comprises a halogenated propane, preferably a hydrofluorocarbon or
a hydrochlorofluorocarbon. In certain preferred embodiments, the
halogenated propane has a structure according to Formula I:
C.sub.3F.sub.xCl.sub.yH.sub.8-x-y (Formula I)
wherein x is 5 or 6 and y is 0 or 1, provided that x+y is
.ltoreq.6. Examples of such halogenated propanes include
1-chloro-1,1,3,3,3-pentafluoropropane (HCFC-235fa),
1,1,1,2,3-pentafluoropropane (HFC-245eb), 1, 1, 1, 2, 3,
3-hexafluoropropane (HFC-236ea), 1,1,1,3,3,3-hexafluoropropane
(HFC-236fa), and 1,1,1,3,3-pentafluoropropane (HFC-245fa).
[0014] In certain preferred embodiments, the aqueous base is an
alkali-metal hydroxide, such as KOH. The strength of the base is
not particularly limited, but preferably is about 10-50%. For
embodiments in which the organic reactant comprises HFC-236 the
strength of the aqueous KOH is preferably about 30-40%. For
embodiments in which the organic reactant comprises HFC-245, the
strength of the aqueous KOH is preferably about 40-50%.
[0015] Preferably, the aqueous base is added to the organic
reactant as a continuous feed stream.
[0016] Preferably, the reaction is performed at a temperature of
about 40 to about 75.degree. C., and more preferably about 50 to
about 60.degree. C.
[0017] Turning to FIG. 1, shown is a semi-batch dehydrohalogenation
system 1 according to a preferred embodiment of the invention.
Here, an organic reactant 10 is charged into a stir tank reactor
100. During or subsequent to the charging, the temperature of the
reactor is controlled via the tank heating/cooling medium 110.
After at least a majority, and preferably all, of an organic
reactant feed for a reaction cycle is charged into reactor 100, a
KOH feed stream 20 is introduced into the reactor to initiate a
liquid phase dehydrohalogenation reaction. The vapor phase product
stream (comprising a hydrofluoroolefin reaction product derived
from the organic reactant and optionally unreacted organic reactant
and moisture) exits the reactor 100 via rectifier/condenser 120.
Here, unreacted organic reactant and moisture reflux back into the
reactor 100, while the desired hydrofluoroolefin is removed as a
product stream 30. At the end of the reaction cycle, the aqueous
waste 40 is removed from the reactor 100.
[0018] The benefit of such an operation is reduced batch cycle time
due to continuous withdrawal of product while returning reactant
thereby maintaining conditions favorable to driving the reaction to
the right side of the chemical equation. That is, by continuously
reducing the concentration of the product, the reaction kinetics
are favorably impacted. An additional benefit is a reduction in the
amount of water that leaves the reactor since any moisture in the
crude product must be removed prior to subsequent processing.
Another benefit is an improved yield due to lower instantaneous
concentration of the aqueous base in contact with a more fragile
molecule (the halogenated alkane and/or the halogenated olefin).
Yet another benefit is a safer operation since of the two
reactants, the aqueous base is the limiting reactant and hence the
energy stored within the reaction system is minimized.
EXAMPLES
[0019] The following non-limiting examples are given to provide a
better understanding of the claimed invention.
Comparative Example 1
HFO-1225zc from HCFC-235fa
[0020] A 10 gallon jacketed metal reactor equipped with an
agitator, rectifying column, and condenser (to reflux unreacted
organic material back to the reactor) were prepared to run a
dehydrohalogenation reaction. The reaction being studied was the
dehydrochlorination of 1-chloro-1,1,3,3,3-pentafluoropropane
(HCFC-235fa) to produce 1,1,3,3,3-pentafluoropropene (HFO-1225zc).
For a first experiment, the reactor was charged with 35.2 lbs of 38
wt % KOH solution and 0.4 lbs of a phase transfer catalyst. The
mixture was then agitated at 420 RPM and heated to 98-100.degree.
C. About 27.1 lbs of crude organic stream containing 65% HCFC-235fa
was added over 6 hours. The reactor pressure rose to about 200 psig
and some product was removed from the top of condenser as it was
formed according to the target temperature at the top of the column
indicating presence of 1,1,3,3,3-pentafluoropropene. The overhead
material was dried using a desiccant and collected in a dry-ice
trap. This approach did not work as the high concentration of high
pH material (KOH) decomposed the organic producing acetates and
formates which stayed in the aqueous layer in the reactor. The
overall yield organic recovered overhead was about 30%. A second
experiment was run similarly with comparable results.
Example 1
HFO-1225zc from HCFC-235fa
[0021] The same equipment, reactants, and operating conditions were
used as described in Comparative Example 1, but for Example 1 the
order of addition was changed. The 27.1 lbs of crude organic
containing 65% HCFC-235fa organic was put into the reactor first,
and heated to the reaction temperature. The rectifying column was
then started at total reflux. Next, 38% KOH solution and phase
transfer catalyst were fed into the reactor continuously over
several hours. The dehydrochlorination reaction proceeded consuming
the KOH as it was added leading to a lower pH system, which did not
decompose the reactants and product, and allowed recovery of the
product overhead.
[0022] The results of this experiment were better than those of
comparative example 1. More particularly, the reaction demonstrated
a 85% conversion of HCFC-235fa and 77% selectivity to
HFO-1225zc.
Comparative Example 2
HFO-1234ze from HFC-245fa
[0023] This reaction was run in a semi-batch mode. About 12500 lbs
of 45% KOH was charged to a 2000 gallon agitated reaction vessel.
The reactor was also equipped with a rectifying column and
condenser. The reactor was then heated to about 60.degree. C. After
the desired temperature was achieved, 8800 lbs of HFC-245fa was fed
to the reactor over a several hour period to produce a desired
HFO-1234ze product by dehydrofluorination. As the reaction was
initiated the pressure in the reactor was allowed to rise to about
100 psig where it was maintained by use of a pressure control
valve. Crude HFO-1234ze exiting the top of the condenser was dried
with a desiccant and collected in a chilled tank. The rectifying
column and condenser continuously refluxed unreacted 245fa back to
the reactor for further processing during the run. After the
desired amount of HFC-245fa was fed a material balance was
performed. The organic yield was only 65%. A dark color was
observed in the spent KOH stream at the end of the batch. Analysis
of the spent KOH revealed high levels of acetates and formates,
indicating a large portion of the HFC-245fa reacted to form
undesirable by-products.
Example 2
HFO-1234ze from HFC-245fa
[0024] The same equipment from Comparative Example 2 was used in
Example 2. The reaction was run in a semi-batch mode. About 12500
lbs of 245fa was charged to the reaction vessel. The reactor was
then heated to about 60.degree. C. After the desired temperature
was achieved, 12000 lbs of 45% KOH was fed to the reactor over a
several hour period to produce a desired HFO-1234ze product by
dehydrofluorination. As the reaction was initiated the pressure in
the reactor was allowed to rise to about 80 psig where it was
maintained by use of a pressure control valve. Crude HFO-1234ze
exiting the top of the condenser was dried with a desiccant and
collected in a chilled tank. The rectifying column and condenser
continuously refluxed unreacted 245fa back to the reactor for
further processing during the run. After the desired amount of 45%
KOH was fed a material balance was performed. The organic yield was
95%, which is quite acceptable for an economical process. Only a
slight discoloration was observed in the spent KOH stream at the
end of batch. Analysis of the spent KOH revealed low levels of
acetates and formates, indicating that only a small portion of the
HFC-245fa reacted to form undesirable products.
Comparative Example 3
HFO-1225ye from HFC-236ea
[0025] The reaction is run in a semi-batch mode. About 12500 lbs of
45% KOH is charged to a 2000 gallon agitated reaction vessel. The
reactor is also equipped with a rectifying column and condenser.
The reactor is then heated to about 60.degree. C. After the desired
temperature is achieved, 10200 lbs of HFC-236ea is fed to the
reactor over a several hour period to produce a desired HF0-1225ye
product by dehydrofluorination. As the reaction is initiated the
pressure in the reactor is allowed to rise to about 100 psig where
it is maintained by use of a pressure control valve. Crude
HFO-1225ye exiting the top of the condenser is dried with a
desiccant and collected in a chilled tank. The rectifying column
and condenser continuously reflux unreacted 236ea back to the
reactor for further processing during the run. After the desired
amount of 236ea is fed a material balance is performed. The organic
yield is only 65%, which is not an acceptable value for an
economical process. A dark color is observed in the spent KOH
stream at the end of the batch. Analysis of the spent KOH reveals
high levels of acetates and formates, indicating a large portion of
the HFC-236ea reacts to form undesirable products.
Example 3
HFO-1225ye from HFC-236ea
[0026] The same equipment from Comparative Example 3 is used in
Example 3. The reaction is run in a semi-batch mode. About 14400
lbs of 236ea is charged to the reaction vessel. The reactor is then
heated to about 60.degree. C. After the desired temperature is
achieved, 12000 lbs of 45% KOH is fed to the reactor over a several
hour period to produce a desired HFO-1225ye product by
dehydrofluorination. As the reaction is initiated the pressure in
the reactor is allowed to rise to about 100 psig where it is
maintained by use of a pressure control valve. Crude HFO-1225ye
exiting the top of the condenser is dried with a desiccant and
collected in a chilled tank. The rectifying column and condenser
continuously reflux unreacted 236ea back to the reactor for further
processing during the run. After the desired amount of 45% KOH is
fed a material balance is performed. The organic yield is 95%,
which is quite acceptable for an economical process. Only a slight
discoloration is observed in the spent KOH stream at the end of
batch. Analysis of the spent KOH reveals low levels of acetates and
formates, indicating that only a small portion of the HFC-236ea
reacts to form undesirable products.
Comparative Example 4
HFO-1234yf from HFC-245eb
[0027] The reaction is run in a semi-batch mode. About 12500 lbs of
45% KOH is charged to a 2000 gallon agitated reaction vessel. The
reactor is also equipped with a rectifying column and condenser.
The reactor is then heated to about 60.degree. C. After the desired
temperature is achieved, 8800 lbs of HFC-245eb is fed to the
reactor over a several hour period to produce a desired HFO-1234yf
product by dehydrofluorination. As the reaction is initiated the
pressure in the reactor is allowed to rise to about 100 psig where
it is maintained by use of a pressure control valve. Crude
HFO-1234yf exiting the top of the condenser is dried with a
desiccant and collected in a chilled tank. The rectifying column
and condenser continuously reflux unreacted 245eb back to the
reactor for further processing during the run. After the desired
amount of 245eb is fed a material balance is performed. The organic
yield is only 65%, which is not an acceptable value for an
economical process. A dark color is observed in the spent KOH
stream at the end of the batch. Analysis of the spent KOH reveals
high levels of acetates and formates, indicating a large portion of
the HFC-245eb reacts to form undesirable products.
Example 4
HFO-1234yf from HFC-245eb
[0028] The same equipment from Comparative Example 4 is used in
Example 4.
[0029] The reaction is run in a semi-batch mode. About 12500 lbs of
245eb is charged to the reaction vessel. The reactor is then heated
to about 60.degree. C. After the desired temperature is achieved,
12000 lbs of 45% KOH is fed to the reactor over a several hour
period to produce a desired HFO-1234yf product by
dehydrofluorination. As the reaction is initiated the pressure in
the reactor is allowed to rise to about 100 psig where it is
maintained by use of a pressure control valve. Crude HFO-1234yf
exiting the top of the condenser is dried with a desiccant and
collected in a chilled tank. The rectifying column and condenser
continuously reflux unreacted 245eb back to the reactor for further
processing during the run. After the desired amount of 45% KOH is
fed a material balance is performed. The organic yield is 95%,
which is quite acceptable for an economical process. Only a slight
discoloration is observed in the spent KOH stream at the end of
batch. Analysis of the spent KOH reveals low levels of acetates and
formates, indicating that only a small portion of the HFC-245eb
reacts to form undesirable products.
Comparative Example 5
HFO-1225zc from HFC-236fa
[0030] A 10 gallon jacketed metal reactor equipped with an
agitator, rectifying column, and condenser (to reflux unreacted
organic material back to the reactor) is prepared to run a
dehydrohalogenation reaction. The reaction being studied is the
dehydrofluorination of 1-chloro-1,1,3,3,3-pentafluoropropane
(HCF236fa) to produce 1,1,3,3,3-pentafluoropropene (HF01225zc). For
Exp#1, the reactor is charged with 36 lbs of 45 wt % KOH solution
and 0.4 lbs of a phase transfer catalyst. The mixture is then
agitated at 350 RPM and heated to 90.degree. C. 30 lbs of 98% pure
HFC236fa is added over 6 hours. The reactor pressure rises to about
200 psig and some product is removed from the top of condenser as
it is formed according to the target temperature at the top of the
column, indicating the presence of 1,1,3,3,3-pentafluoropropene.
The overhead material is dried using a desiccant and collected in a
dry-ice trap. This approach does not work as the high concentration
of high pH material (KOH) decomposes the organic, producing
acetates and formates which stay in the aqueous layer in the
reactor. The overall yield organic recovered overhead is about
35%.
Example 5
HFO-1225zc from HFC-236fa
[0031] The same equipment, reactants, and operating conditions are
used as described in Comparative Example 5, but for Exp#2 the order
of addition is reversed. The 30 lbs of 236fa is put into the
reactor first, and heated to the reaction temperature. The
rectifying column is then started at total reflux. Next, 45% KOH
solution and phase transfer catalyst are fed into the reactor
continuously over several hours. The dehydrofluorination reaction
commences consuming the KOH as it is added leading to a lower pH
system, which does not decompose the reactants and product, and
allows recovery of the product overhead. Results of Exp#2 are much
better than Exp#1 with 80% conversion of HCFC236fa and 90%
selectivity to 1225zc.
* * * * *