FIELD OF INVENTION
The present invention relates to processes for separating
pentafluoroethane (CHF2-CF3, HFC-125) from a mixture comprising
HFC-125 and chloropentafluoroethane (CF3-CClF2, CFC-115).
The present invention further relates to the production of heptafluoropropane (CF3CHFCF3
or CF3CF2CHF2, HFC-227ea or HFC-227ca, collectively
BACKGROUND OF THE INVENTION
In the recent years, there has been an increasing concern
about global warming. As a result, several chlorofluorocarbons (CFC's) that are
known to have an adverse environmental impact have been removed from the marketplace.
In their place, new compounds have been introduced as flooding agents, streaming
agents, blowing agents, propellants, and refrigerants. However, some of these new
compounds do not meet environmental safety requirements. Consequently, there is
a constant need to develop fluorocarbon compounds, especially hydrofluorocarbons,
which have no chlorine. Two hydrofluorocarbons that are known to have desirable
properties are pentafluoroethane (HFC-125) and heptafluoropropane (HFC-227).
HFC-125 is a valuable hydrofluorocarbon (HFC) that is especially
useful as a refrigerant, blowing agent, propellant, or fire-extinguishing agent.
HFC-125 can be prepared by a multi-step process starting with fluorination of tetrachloroethene
(C2Cl4). The end products of the multi-step process include
a mixture containing HFC-125, chloropentafluoroethane (CFC-115), and small amounts
of other fluorinated compounds.
HFC-227 is another valuable hydrofluorocarbon. One known
starting material for the production of HFC-227 is hexafluoropropene (CF3CF=CF2,
HFP). HFP can be hydrofluorinated with hydrogen fluoride (HF) in the presence of
a suitable catalyst to form HFC-227 and other byproducts. Typically, in the final
step of HFC-227 purification, these byproducts are separated out by simple distillation.
CFC-115 is an undesirable compound because it contains
chlorine, and, as a result, its use is highly regulated. Thus, in the production
of HFC-125 for commercial use, it is necessary to separate HFC-125 from CFC-115.
Unfortunately, the mixture of HFC-125 and CFC-115 forms a near-azeotrope. At high
concentrations of HFC-125, the relative volatility of HFC-125 to CFC-115 is close
to 1.0, making recovery of pure HFC-125 from a mixture of HFC-125 and CFC-115 by
simple distillation difficult.
An azeotrope is a liquid mixture that exhibits a maximum
or minimum boiling point relative to the boiling points of its components. An azeotrope
is homogeneous if only one liquid phase is present. An azeotrope is heterogeneous
if more than one liquid phase is present. Regardless, a characteristic of azeotropes
is that the bulk liquid composition is identical to the vapor composition in equilibrium
therewith, and distillation of the azeotropic mixture is ineffective as a separation
technique. For the purposes of this discussion, a near-azeotrope means a composition
which behaves like an azeotrope (i.e., has constant-boiling characteristics or a
tendency not to fractionate upon boiling or evaporation). Thus, the composition
of the vapor formed during boiling or evaporation of such compositions is the same
as or substantially the same as the original liquid composition. Hence, during boiling
or evaporation, the liquid composition, if it changes at all, changes only to a
minimal or negligible extent. This is to be contrasted with non-azeotrope compositions
in which during boiling or evaporation, the liquid composition changes to a substantial
Accordingly, the essential features of an azeotrope or
a near-azeotrope are that at a given pressure, the boiling point of the liquid composition
is fixed and that the composition of the vapor above the boiling composition is
essentially that of the boiling liquid composition (i.e., no fractionation of the
components of the liquid composition takes place). It is recognized in the art that
both the boiling point and the weight percentages of each component of the azeotropic
composition may change when the azeotrope or near-azeotrope liquid composition is
subjected to boiling at different pressures. Thus, an azeotrope or a near-azeotrope
may be defined in terms of the unique relationship that exists among components
or in terms of the compositional ranges of the components or in terms of exact weight
percentages of each component of the composition characterized by a fixed boiling
point at a specified pressure. It is also recognized in the art that various azeotropic
compositions including their boiling points at particular pressures may be calculated
W. Schotte, Ind. Eng. Chem. Process Des. Dev. 1980, 19, pp 432-439
). Experimental identification of azeotropic compositions involving the
same components may be used to confirm the accuracy of such calculations and/or
to modify the calculations for azeotropic compositions at the same or other temperatures
It is known that pure HFC-125 as a near-azeotropic mixture
with CFC-115 can be recovered by a process of extractive distillation. In this process,
a suitable extracting agent that changes the relative volatility of a component
or the azeotrope is used. Examples of extracting agents used in the purification
of HFC-125 are disclosed in
U.S. Patent Nos. 5,087,329
Extractive distillation processes for the purification
of HFC-125 usually include a step of separating the extracting agent from either
HFC-125 or CFC-115 subsequent to the completion of the extractive distillation.
This additional separation process may add to the cost of HFC-125 production even
though the extracting agent may be reused.
SUMMARY OF INVENTION
The present invention provides processes for the production
of halogenated hydrocarbons either alone or in combination with the synthesis of
olefinic derivatives. In one embodiment of the present invention, at least one halogenated
hydrocarbon is purified from a near-azeotropic mixture comprising at least one halogenated
hydrocarbon and at least one halocarbon by extractive distillation using an olefinic
extracting agent. In this particular embodiment, the olefinic extracting agent is
converted into a derivative compound.
In another embodiment of the present invention, HFC-125
is purified from a mixture containing CFC-115 by extractive distillation, using
hexafluoropropene (HFP) or chlorotrifluoroethene (CClF=CF2, CFC-1113)
as an extracting agent. One feature of this particular embodiment is that the extracting
agent can be recovered and reused in the purification of HFC-125 as set forth herein.
In an alternative embodiment, the recovered extracting agent can be used as a starting
material for the production of fluorocarbons like HFC-227.
In a specific embodiment of the present invention, the
process of recovering HFC-125 comprises the steps of: (a) providing a first mixture
comprising HFC-125 and CFC-115, (b) distilling the first mixture in the presence
of hexafluoropropene (HFP) to separate HFC-125 from a second mixture comprising
HFP and CFC-115. The distilling process may be extractive distillation, in which
HFP is an extracting agent.
According to another embodiment of the invention, the process
may further include the steps of: (c) recovering HFC-125 as an overhead product
and (d) recovering the second mixture as a bottom product.
According to a further embodiment, the process may further
include the step of: (e) purifying HFP from the second mixture to produce a third
mixture comprising CFC-115 and the step of (f) recovering HFP. Optionally, the process
may include the step of re-using the recovered HFP as an extracting agent, as described
Another embodiment of the present invention is directed
to a process comprising the steps of: (a)-(d), as described, and the steps of: (g)
adding HF to the second mixture to form a fourth mixture, (h) converting HFP in
the fourth mixture by hydrofluorination in the presence of a suitable catalyst to
HFC-227 to produce a fifth mixture, (i) separating the fifth mixture into HFC-227
and a sixth mixture comprising CFC-115, and (j) recovering HFC-227.
A further embodiment of the present invention is directed
to a process comprising the steps of: (a)-(f), as described, and the steps of: (k)
adding HF to the recovered HFP, (1) converting the recovered HFP by hydrofluorination
to HFC-227 in the presence of a suitable catalyst to produce a seventh mixture,
(m) separating the seventh mixture into HFC-227 and byproducts, and (n) recovering
In another embodiment, the process comprises the steps
of: (a)-(f), as described, and the step of converting HFP to at least one HFP derivative
or a fluoropolymer.
In an alternative embodiment of the present invention,
the process comprises the steps of: (o) providing a first mixture comprising HFC-125
and CFC-115, (p) distilling the first mixture in the presence of CFC-1113 to separate
HFC-125 from an eighth mixture comprising CFC-1113 and CFC-115, (q) recovering HFC-125
as an overhead product, and (r) recovering the eighth mixture as a bottom product.
The distilling process may be extractive distillation, in which HFP is an extracting
In still another embodiment, the process comprises the
steps of (o)-(r) and the steps of: (s) adding HF to the eighth mixture to produce
a ninth mixture, (t) converting CFC-1113 in the ninth mixture in the presence of
a suitable catalyst to a fluoroethane to make a tenth mixture, and recycling the
tenth mixture to a hydrofluorocarbon production process. In one embodiment, the
fluoroethane is 1-chloro-1,2,2,2-tetrafluoroethane (CHClFCF3, HCFC-124).
The above and other embodiments, aspects, alternative and
advantages of the present invention will become more apparent from the following
detailed description of the present invention taken in conjunction with the examples.
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention overcome the shortcomings
of the prior art by providing innovative processes for producing hydrofluorocarbons
by separating mixtures of near-azeotrope halogenated hydrocarbons with extracting
agents and subsequently converting the extracting agent to a derivative compound
that can be separated from at least one of the halogenated hydrocarbons from the
In one embodiment, the present invention involves the use
of an extracting agent, namely HFP, that can be used to purify HFC-125 from a mixture
comprising HFC-125 and CFC-115. The mixture may contain mostly HFC-125 and only
minute amounts of CFC-115 and other fluorocarbon byproducts. HFP is an important
monomer used to produce organic fluorine materials and is readily available in the
The use of HFP as an extracting agent for the separation
of alkanes has never been described in the prior art. It is commonly known that
similar compounds are attracted to each other. Thus, typically, in order to separate
chlorine containing alkanes from non-chlorine containing alkanes, another chlorine
containing alkane is used as an extracting agent. As an alkene, HFP is structurally
different from the alkanes disclosed as extracting agents in the
U.S. Patent No. 5,087,329
. This structural difference in combination with the fact that HFP contains
no chlorine made its usefulness as an extracting agent for separating HFC-125 from
CFC-115 unexpected. The use of HFP and fluorinated alkenes as extracting agents
is demonstrated below in non-limiting Example 1.
Screening of extracting agents for vapor phase separation of HFC-125 and CFC-115
A 50 cc stainless steel sample cylinder fitted with a pressure
gauge and valve with a septum port was chilled to -78°C and a known amount
of HFC-125 and CFC-115 was charged to the cylinder. This mixture was shaken and
allowed to warm to ambient temperature and the vapor phase was sampled for subsequent
analysis by gas chromatography (GC).
The cylinder was then re-cooled to -78°C and a desired
amount of the chosen extraction solvent was added to the vessel. The mixture was
then allowed to warm to ambient temperature, at which time, it was shaken and allowed
to equilibrate for 3 to 12 hours before it was re-sampled for GC analysis.
All GC data of this and the following examples were taken
by sampling a collection or storage vessel or the appropriate sample port with a
50 to 250 µL airtight syringe fitted with an on/off valve. This collected sample
was injected on either an HP-5890 or 5890II GC equipped with a Varian plot fused
silica column (30m x 0.32mm ID). All analyses were done using a time-temperature
program which had an initial temperature and time of 70°C and 15 min followed
by a ramp to 140°C at a rate of 15°C/min and a final time of 20 min. Selection
of column type, sample size and analysis conditions are well known to those skilled
in the art of GC. All amounts noted were based on area percent. To verify the identity
of each compound, analyses were performed using mass spectrometry.
TABLE I is a result of the GC analyses of vapor phase content
of HFC-125 and CFC-115 in the starting mixture and the mixture with extracting agent
that absorbs CFC-115. As shown in TABLE I, relative volatility of CFC-115 changed
with the addition of different solvents. The volatility of CFC-115 was relatively
low with the addition of the CFC-solvents, like 1,1,2-trichloro-1,2,2-trifluoroethane
(CCl2FCClF2, CFC-113) and 1,2-dichloro-1,1,2,2-tetrafluoroethane
(CClF2CF2Cl, CFC-114). Thus, these solvents, CFC-113 and CFC-114,
performed well in the separation of CFC-115 from HFC-125, as shown by the increase
in the percent of HFC-125 or the decrease in the percent of CFC-115 in the vapor
phase. As expected, the similar compounds like dichlorohexafluoropropane (C3F6Cl2,
CFC-216) and chloroheptafluoropropane (C3F7Cl, CFC-217) also
exhibited good extracting ability for CFC-115. However, being chlorofluorocarbons,
these compounds are not desirable extracting agents because they are highly regulated
suspect ozone depleting compounds.
The efficiency of the fluoro-olefins, namely CFC-1113,
HFP, HFC-1243zf (CF3CH=CH2, TFP), and HFC-1225zc (CF3CH=CF2,
PFP) varied. CFC-1113 and HFP demonstrated a surprising ability to extract CFC-115
from HFC-125. However, since HFP contains no chlorine, it may be more useful as
an extracting agent.
In contrast to HFP and CFC-1113, the olefins HFC-1243zf
and HFC-1225zc had little or no extractive power. In addition, chloroform (CHCl3)
did not appear to be an effective extracting agent for the separation of CFC-115.
TABLE I: GC Analysis of the vapor phase content of HFC-125 and CFC-115 in starting
mixture and mixture with extracting agent that absorbs CFC-115
Relative Volatility of CFC-115
Extracting agent added
Extracting agent added
In certain embodiments, the present invention involves
utilizing olefinic extracting agents in two different ways. First, the olefinic
extracting agent can be used to purify HFC-125 from a mixture comprising HFC-125
and CFC-115. Relatively pure HFC-125 is recovered as the overhead product, while
the majority of the olefinic extracting agent is recovered as a mixture with CFC-115
as a bottom product. In one embodiment, the olefinic extracting agent is HFP. In
another embodiment, the olefinic extracting agent is CFC-1113.
Second, after it is used as an extracting agent, the olefinic
extracting agent can be recovered and used as a precursor for the production of
extracting agent derivatives or fluoropolymers. As an olefin, the recovered extracting
agent lends itself to hydrohalogenation by addition across the double bond.
In one embodiment, HF is added across the double bond of
HFP to produce HFC-227. In another embodiment, HF may be added across the double
bond of CFC-1113 to produce HCFC-124. In these embodiments, the relative volatility
of the extracting agent derivative is sufficiently disparate from CFC-115 that the
derivative can be readily separated by known chemical separation techniques such
as distillation. Further, CFC-1113 may also be converted to HFC-125 or a mixture
of HFC-125 and HCFC-124, in which case it may be recycled to the HFC-125/CFC-115
purification process to produce more HFC-125.
These types of hydrohalogenation reactions are commonly
performed in the presence of a catalyst. Suitable gas phase catalysts include activated
carbon, chromium oxide, nickel, copper, iron, or aluminum oxide. Suitable liquid
phase catalysts include antimony chloride, molybdenum, and tantalum. It is contemplated
that other compounds and synthetic schemes can be used to derivatize the extracting
agent. The resulting compound may be recovered or recycled back to the separation
According to a specific embodiment of the present invention,
a process for separating HFC-125 from CFC-115 is provided. The process includes
a step of (a) providing a first mixture comprising HFC-125 and CFC-115. The first
mixture may be derived from a hydrofluorination reaction of tetrachloroethene, or
other similar processes. The first mixture may also contain small amounts of other
hydrofluorination byproducts such as 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113),
1,2-dichloro-1,1,2,2-tetrafluoroethane (CFC-114), 2,2-dichloro-1,1,1-trifluoroethane
(HCFC-123), or hexafluoroethane (FC-116). The percent concentration of HFC-125 and
CFC-115 in the first mixture may vary. The first mixture may contain more than 90%
The first mixture is fed to a fractionation column. In
this specific embodiment of the invention, the process further comprises the step
of (b) distilling the first mixture in the presence of HFP to separate HFC-125 from
a second mixture comprising HFP and CFC-115. During this step, HFP is added to the
upper section of the fractionation column. As much as about 50% HFP by weight of
HFC-125 may be used, although more than 50% HFP by weight of HFC-125 may be used
if desired. However, preferably 20% HFP by weight of HFC-125 is used.
The distillation is performed at a condition that allows
HFC-125 to pass substantially free of CFC-115 to the top of the column where it
is condensed. Some of the HFC-125 may be returned as reflux. Simultaneously, HFP
and CFC-115 pass to the bottom of the column as a second mixture. It is possible
for the second mixture to also contain residual HFC-125 and other compounds that
are present in the first mixture. Finally, in a particular embodiment, the process
includes the steps of (c) recovering HFC-125 as an overhead product and (d) recovering
the second mixture as a bottom product. One embodiment of this process is demonstrated
below in non-limiting Example 2.
Vapor phase separation of HFC-125 from CFC-115 using HFP as an extracting agent
This procedure demonstrates the effective removal of CFC-115
from streams of the first mixture comprising HFC-125 and CFC-115, by the use of
HFP as an extracting agent.
The apparatus used was a 92 in. packed, schedule 40, carbon
steel distillation column fitted with a reboiler, overhead condenser, overhead reflux
loop, timed take-off valves, and multiple feed points. This evacuated column was
charged with 584 g of the first mixture comprising 97.928% of HFC-125 and 2.073
% of CFC-115, by weight. This mixture was allowed to equilibrate at a reflux ranging
from 14 to 29 cc/min. HFP was then fed into the column at an average rate of 1.98
g/min, while taking off CFC-115 and HFP at a rate of 1.75 g/min as the bottom product
from the reboiler.
The operation was continued over 2348 minutes. The total
amount of HFP added was 4438 g. During this time, the relative ratio of HFC-125
to CFC-115 in the overhead of the column increased from 87 to 8194 (TABLE II). This
ratio represents approximately 121 ppm (0.0121 % GC-Area) of CFC-115 remaining in
the overhead fraction (TABLE II).
The recovery from the reboiler shows that most of the HFP
was recaptured in the reboiler or the bottom fraction. This bottom fraction also
contained CFC-115 and residual HFC-125 (TABLE II).
At the end of the operation, the initial charge, including
the amount of the first mixture and the total amount of HFP used, is compared to
the final recovery in both the reboiler and the overhead fractions. The results
show a total mass balance accountability of 96.6%.
TABLE II: Extractive distillation using HFP as an extracting agent to separate
HFC-125 from CFC-115
HFP Feed (g)
HFC-125 (% GC-Area)
CFC-115 (% GC-Area)
Relative ratio of HFC-125 to CFC-115
HFC-125 (% GC-Area)
CFC-115 (% GC-Area)
HFP (% GC-Area)
In another embodiment of the present invention, the process
further includes the step of (e) purifying HFP in the second mixture to produce
relatively pure HFP and a third mixture comprising CFC-115 and the step of (f) recovering
HFP. The third mixture may include residual HFP and HFC-125. In addition, the third
mixture may also include small amounts of byproducts, as indicated above. The recovered
HFP from this purification step may contain a minute amount of CFC-115 and other
byproducts. The purification step may involve any appropriate technique including
distillation. The purification of HFP by simple distillation is demonstrated below
in non-limiting Example 3.
Purification of HFP
To demonstrate this process, 507 grams of a mixture containing
90.17% of HFP, 9.798% of HFC-125, and 0.025% of CFC-115 (see TABLE III) was charged
to an apparatus consisting of a 92 in. packed, schedule 40, carbon steel distillation
column fitted with a reboiler, overhead condenser, and overhead reflux loop. This
mixture was allowed to equilibrate with a steady reflux for 224 minutes. The distillation
was run at a pressure of about 122-123 psig. The boiler temperature was set at about
31.4°C, and the overhead temperature was set at about 27°C. The overhead
and reboiler compositions were checked by GC analysis. The column was then equilibrated
for another 100 minutes to obtain further homogeneity of the HFP in the reboiler
of the column (see TABLE III). This demonstrates that the longer the distillation
was run, the higher purity of HFP was obtained. This level of purity is acceptable
for recycle to the HFC-125 extractive distillation system or to be used as a raw
material in subsequent downstream reactions.
TABLE III: Separation of HFP from HFC-125 and CFC-115 by distillation
Equilibrium Time (min)
The recovered HFP may be recycled to be used as an extracting
agent in the process of recovering HFC-125 described herein. In another embodiment,
the recovered HFP may be converted to at least one of HFP derivatives such as HFC-227,
or polymers such as elastomers, plastomers, resins, and fluoropolymers.
Another specific embodiment of the present invention comprises
the steps of (a)-(d), as described herein, and the further steps of (g) adding HF
to the second mixture to form a fourth mixture and (h) converting HFP in the fourth
mixture to HFC-227 by hydrofluorination to form a fifth mixture. The benefits of
this embodiment are demonstrated by way of non-limiting Example 4 below.
Converting HFP to HFC-227 by selective hydrofluorination in the presence of HFC-125
A 34 cc alloy-600 reactor tube was charged with 13.1 g
of activated carbon catalyst and dried overnight at 155°C with a nitrogen purge.
The reaction outlet was configured with an aqueous scrubber filled with dilute caustic
followed by a Drierite tube, GC sampling port, and optional cold trap. Three different
mixtures were used as the starting material in the reaction runs (# 1-3). Each mixture
comprises HFP and minute amounts of CFC-115 and HFC-125 (see TABLE IV). In the reaction
run # 4, relatively pure HFP was used as the starting material for comparison.
TABLE IV: Composition (% GC) of starting material for four reaction runs of fluorination
of HFP to HFC-227
Specific conditions of each fluorination reaction run using
the materials shown in TABLE IV are shown in TABLE V. For each run, the starting
material was supplied to the reactor tube described above. HF was first added to
the reactor tube at a rate of about 70 to 74 cc/min. The flow rate of the starting
material was about 47 to 60 cc/min. The ratio of HF to HFP ranged from 1.28 to 1.60.
The fluorination reaction was run at a temperature of about 200° C (see TABLE
V). The contact time ranged from 9.16 to 10.08 seconds.
TABLE V: Fluorination conditions of four fluorination reaction runs using four
starting materials shown in TABLE IV
Contact Time (sec)
Starting Material HFP/115/125 (cc/min)
Molar Ratio HF:HFP
* HFP only
The result of each fluorination reaction run shown in TABLE
V is reported in TABLE VI. Percent conversion of HFP to HFC-227 ranged from about
92.13 to 97.24, while selectivity ranged from about 85 to about 99 %. The amounts
of HFC-125 and CFC-115 did not substantially change from what was present in the
starting materials (see TABLE IV and VI). Thus, the data in TABLE VI indicate that
olefins can be selectively fluorinated without causing any serious side reactions
or lowering of conversion while allowing HFC-125 and CFC-115 to pass through the
system essentially unchanged.
TABLE VI: The results of the fluorination process based on the conditions shown
in TABLE V
HFC-125 % GC-Area
CFC-115 % GC-Area
In accordance with another embodiment of the present invention,
a process includes the steps of (a)-(d), (g)-(h), and the step (i) separating the
fifth mixture into HFC-227 and a sixth mixture comprising CFC-115. The sixth mixture
may further comprise HFC-125 and other fluorination byproducts. The separation can
be performed by distillation. Finally, this specific embodiment further includes
the step of(j) recovering relatively pure HFC-227. This embodiment is demonstrated
below by way of non-limiting Example 5.
Separation of HFC-227 from HFC-125 and CFC-115
A mixture containing mainly HFC-227 (57.24%), HFC-125 (29.44%),
and CFC-115 (13.32%) was used as the starting material to demonstrate the process
of HFC-227 separation. An evacuated apparatus consisting of a 92 in. packed, schedule
40, carbon steel distillation column fitted with a reboiler, overhead condenser,
and overhead reflux loop was charged with 719 grams of the above described mixture.
This mixture was allowed to equilibrate at a reflux ranging from 1.86 to 2.46 cc/min
over a 1417 minute time period. The overhead product and the bottom product were
collected at three different distillation conditions (see TABLE VII). The content
of both the overhead and the bottom products was determined by GC. The results shown
in TABLE VII indicate that the majority of HFC-227 was separated in the bottom fraction
while HFC-125 and CFC-115 were removed as distillates. When the reboiler temperature
was increased from 28.2°C to 55.3°C and the vapor pressure was raised
from 132 psig to 143 psig, the reflux increased from 1.85 cc/min to 2.46 cc/min,
and a significant increase in purity of the HFC-227 in the bottom fraction was observed.
Essentially pure HFC-227 (99.92%) could be recovered under one of the conditions
tested (144 psig, reboiler temperature 54.8°C, overhead temperature 21.9°C,
reflux 2.46 cc/min), while only a small amount of HFC-227 was removed in the overhead
fraction. The levels of HFC-227 purity recovered were acceptable for commercial
use. The resulting CFC-115 and HFC-125 can either be destroyed, recycled or reacted
to form other desirable and useful materials.
TABLE VII : Separation of HFC-227 at three different distillation conditions
a: 132 psig, reboiler temperature
28.2°C, overhead temperature 21.5°C, reflux 1.85 cc/min
b: 143 psig, reboiler temperature 55.3°C, overhead temperature 21.6°C,
reflux 2.46 cc/min
c: 144 psig, reboiler temperature 54.8°C, overhead temperature 21.9°C,
reflux 2.46 cc/min
A further embodiment of the present invention involves
a process which comprises the steps of(a)-(f) and the steps of: (k) adding HF to
the purified HFP, (1) converting the purified HFP by hydrofluorination to HFC-227
in the presence of a suitable catalyst to form a seventh mixture, (m) separating
the seventh mixture into HFC-227 and fluorination byproducts, and (n) recovering
relatively pure HFC-227. An example of converting relatively pure HFP to HFC-227
is demonstrated in TABLES IV-VI (see run #4).
According to one embodiment, the suitable catalyst is active
carbon, but other catalysts that have been previously described are contemplated.