PROCESS FOR MANUFACTURING TETRAFLUOROPROPENE
FIELD OF THE INVENTION
The present invention relates to a process for the manufacture of
10 tetrafluoropropene (HFO-1234) and in particular of 2,3,3,3-tetrafluoropropene
(HFO-1234~0, and also to a plant suitable for the implementation of this
process.
TECHNICAL BACKGROUND
15 Greenhouse gases are gaseous components which absorb the infrared
radiation emitted by the surface of the earth, thus contributing to the
greenhouse effect. The increase in their concentration in the atmosphere is one
of the factors causing global warming.
The production of the chlorofluorocarbons (CFCs) and
20 hydr~chlor~flu~r~carb(HoCnsF Cs) used in refrigeration and air conditioning
systems has thus been successively regulated by the Montreal protocol and
then the Kyoto protocol. There exists a need to develop new molecules which
are as effective and which in particular exhibit the smallest possible global
warming potential. This is the case with hydrofluoroolefins and in particular
25 HFO-1234yf, which is a particularly useful compound.
It is known to produce hydrofluoroolefins or hydrofluorocarbons by
fluorination of hydrochloroolefins or of hydrochlorocarbons in particular. This
fluorination is generally a catalytic fluorination using hydrofluoric acid as
fluorinating agent.
30 The fluorination reaction generally has to be carried out at a high
temperature (more than 300°C) in the gas phase, in the presence of a
supported or bulk solid catalyst.
It is known to provide cofeeding with an oxidizing agent, in particular air,
or optionally chlorine, in order to preserve the lifetime of the catalyst and to limit
35 the deposition of coke at its surface during the reaction stage.
The document US 8 614 361 describes a process for the manufacture of
HFO-1234yf by reacting HCFO-1233xf with HF in the presence of a high
oxygen content.
The document US 8 618 338 describes a process for the manufacture of
5 fluoroolefin in two stages, in particular a first stage of reaction in the liquid
phase starting from 1,1,2,3-tetrachloropropene (HCO-1230xa), in order to
obtain the intermediate HCFO-1233xf, and a second stage of reaction in the
gas phase starting from HCFO-1233xf, in order to obtain HFO-1234yf.
The document WO 20131088195 teaches a process for the manufacture
10 of HFO-1234yf in two stages, a first stage of fluorination in the gas phase of
1 ,I ,I ,2,3-pentachloropropane (HCC-240db) andlor of 1 , I ,2,2,3-
pentachloropropane (HCC-240aa), in order to obtain the intermediate
HCFO-1233xf, and then a second stage of reaction in the gas phase starting
from HCFO-1233xf, in order to obtain HFO-1234yf.
15 The documents WO 20121098421 and WO 20121098422 teach the
activation and the regeneration of fluorination catalysts.
The document WO 20131182816 describes a chemical reaction process
for the alternating implementation of a phase of catalytic reaction and of a
phase of regeneration of catalyst in a reactor.
20 There still exists a need to improve the processes for the manufacture of
HFO-1234 compounds, such as HFO-1234yf, and in particular to produce these
compounds with a high yield and with a high degree of purity.
SUMMARY OF THE INVENTION
25 The invention relates first to a process for the manufacture of
tetrafluoropropene, comprising, alternately:
- at least one stage of reaction of a chlorinated compound with
hydrofluoric acid in the gas phase, in the presence of a fluorination
catalyst, the proportion of oxygen optionally present being less than
0.05 mol% with respect to the chlorinated compound;
- a stage of regeneration of the fluorination catalyst by bringing the
fluorination catalyst into contact with a regeneration stream
comprising an oxidizing agent.
According to one embodiment, the stage of reaction of the chlorinated
35 compound with hydrofluoric acid is carried out essentially in the absence of
oxygen and preferably essentially in the absence of any oxidizing agent
According to one embodiment, the regeneration stream contains at least
1 mol% of oxygen with respect to the total regeneration stream.
According to one embodiment, the stage of reaction of the chlorinated
compound with hydrofluoric acid is carried out in a single reactor, separately in
5 time with respect to the stage of regeneration of the fluorination catalyst.
According to one embodiment, the stage of reaction of the chlorinated
compound with hydrofluoric acid is carried out in at least one first reactor,
simultaneously with the implementation of the stage of regeneration of the
fluorination catalyst in at least one second reactor.
10 According to one embodiment, the tetrafluoropropene is 2,3,3,3-
tetrafluoropropene.
According to one embodiment, the tetrafluoropropene is 1,3,3,3-
tetrafluoropropene.
According to one embodiment, the chlorinated compound is chosen from
15 tetrachloropropenes, chlorotrifluoropropenes, pentachloropropanes and
mixtures of these.
According to one embodiment, the chlorinated compound is 2-chloro-
3,3,3-trifluoropropene and the tetrafluoropropene is 2,3,3,3-tetrafluoropropene.
According to one embodiment, the chlorinated compound is 1, I1,,2 ,3-
20 pentachloropropane andlor 1 ,I ,2,2,3-pentachloropropane and the
tetrafluoropropene is 2,3,3,3-tetrafluoropropene.
According to one embodiment, the chlorinated compound is l-chloro-
3,3,3-trifluoropropene and the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.
According to one embodiment, the process comprises:
- a preliminary stage of manufacture of the chlorinated compound,
which is preferably a preliminary stage of reaction of a preliminary
compound with hydrofluoric acid in the gas phase, in the presence of
a preliminary fluorination catalyst, the proportion of oxygen optionally
present being less than 0.05 mol% with respect to the preliminary
compound.
According to one embodiment, the preliminary stage of reaction is carried
out alternately with:
- a stage of regeneration of the preliminary fluorination catalyst by
bringing the preliminary fluorination catalyst into contact with a
35 regeneration stream comprising an oxidizing agent.
According to one embodiment, the preliminary compound is 1,1,1,2,3-
pentachloropropane andlor 1,1,2,2,3-pentachloropropanet,h e chlorinated
compound is 1-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is
2,3,3,3-tetrafluoropropene.
According to one embodiment, the process comprises:
- the collecting of a stream of products on conclusion of the preliminary
reaction stage;
- the separation of the stream of products into a first stream
comprising hydrochloric acid and tetrafluoropropene and a second
stream comprising hydrofluoric acid and the chlorinated compound;
- the use of said second stream to carry out the stage of reaction of
the chlorinated compound with hydrofluoric acid; and
- optionally, the collecting of a stream of products on conclusion of the
stage of reaction of the chlorinated compound with hydrofluoric acid
and the recycling of the latter in the preliminary reaction stage.
The invention also relates to a plant for the manufacture of
15 tetrafluoropropene, comprising at least one gas-phase fluorination reactor
comprising a bed of fluorination catalyst, said gas-phase fluorination reactor
being configured in order to be fed alternately by:
- a system for feeding with reaction stream comprising a chlorinated
compound and hydrofluoric acid, the proportion of oxygen optionally
present in this reaction stream being less than 0.05 mol% with
respect to the chlorinated compound; and
- a system for feeding with regeneration stream comprising an
oxidizing agent.
According to one embodiment, the reaction stream is essentially devoid
25 of oxygen and preferably of any oxidizing agent.
According to one embodiment, the regeneration stream contains at least
1 mol% of oxygen with respect to the total regeneration stream.
According to one embodiment, the plant comprises a single reactor
configured in order to be fed alternately by the system for feeding with reaction
30 stream and the system for feeding with regeneration stream.
According to one embodiment, the plant comprises a plurality of reactors,
each being configured in order to be fed alternately by a system for feeding with
reaction stream and a system for feeding with regeneration stream.
According to one embodiment, the plant is configured so that, when a
35 reactor is fed by the system for feeding with reaction stream, another reactor is
fed by the system for feeding with regeneration stream.
According to one embodiment, the plant is configured so that:
- the system for feeding with reaction stream feeds the reactor at the
bottom and the system for feeding with regeneration stream feeds
the reactor at the bottom; or
- the system for feeding with reaction stream feeds the reactor at the
bottom and the system for feeding with regeneration stream feeds
the reactor at the top; or
- the system for feeding with reaction stream feeds the reactor at the
top and the system for feeding with regeneration stream feeds the
reactor at the bottom; or
- the system for feeding with reaction stream feeds the reactor at the
top and the system for feeding with regeneration stream feeds the
reactor at the top.
According to one embodiment:
- the tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or
- the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.
According to one embodiment, the chlorinated compound is chosen from
tetrachloropropenes, chlorotrifluoropropenes, pentachloropropanes and
mixtures of these; and preferably:
- the chlorinated compound is 2-chloro-3,3,3-trifluoropropene and the
20 tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or
- the chlorinated compound is 1,1,1,2,3-pentachloropropane andlor
1,1,2,2,3-pentachloropropane and the tetrafluoropropene is 2,3,3,3-
tetrafluoropropene; or
- the chlorinated compound is 1-chloro-3,3,3-trifluoropropene and the
tetrafluoropropene is 1,3,3,3-tetrafluoropropene.
According to one embodiment, the plant comprises:
- at least one unit for the manufacture of chlorinated compound, which
preferably is at least one preliminary fluorination reactor; configured
in order to be fed by:
- a system for feeding with reaction medium comprising a preliminary
compound and hydrofluoric acid, the proportion of oxygen optionally
present in this reaction stream being less than 0.05 mol% with
respect to the preliminary compound.
According to one embodiment, the preliminary fluorination reactor is also
35 configured in order to be fed by a system for feeding with regeneration stream
comprising an oxidizing agent.
According to one embodiment, the preliminary compound is 1,1,1,2,3-
pentachloropropane andlor 1 , I ,2,2,3-pentachloropropane, the chlorinated
compound is I-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is
2,3,3,3-tetrafluoropropene.
According to one embodiment, the plant comprises:
- at least one first catalytic fluorination reactor;
- at least one second catalytic fluorination reactor;
- a system for collecting a stream of products connected at the outlet
of the first catalytic fluorination reactor;
- a separation unit fed by the system for collecting a stream of
products;
- a first collecting pipe and a second collecting pipe which are
connected at the outlet of the separation unit, the first collecting pipe
being configured in order to transport a stream comprising
hydrochloric acid and tetrafluoropropene and the second collecting
pipe being configured in order to transport a stream comprising
hydrofluoric acid and chlorinated compound;
- an intermediate collecting system connected at the outlet of the
second reactor;
- a first system for feeding with reaction medium configured in order to
feed the first reactor, this being itself fed by the intermediate
collecting system;
- a second system for feeding with reaction medium configured in
order to feed the second reactor, this being itself fed by the second
collecting pipe;
- a system for feeding with regeneration stream configured in order to
feed the first reactor andlor the second reactor; and
- a system for collecting a stream of gases resulting from the
regeneration.
30 According to one embodiment, the plant comprises at least two second
reactors configured so that, when one of these reactors is fed by the second
system for feeding with reaction stream, the other reactor is fed by the system
for feeding with regeneration stream.
According to one embodiment, the plant comprises at least two first
35 reactors and two second reactors configured so that, when one of the first
reactors and one of the second reactors are respectively fed by the f~rsst ystem
for feeding with reaction stream and the second system for feeding with reaction
stream, the other first reactor and the other second reactor are fed by the
system for feeding with regeneration stream; and which, preferably, is
configured so that one and the same regeneration stream resulting from the
system for feeding with regeneration stream passes successively into the first
5 reactor and then the second reactor or passes successively into the second
reactor and then the first reactor.
According to one embodiment, the plant comprises a single second
reactor configured in order to be fed sequentially either by the second system
for feeding with reaction stream or by the system for feeding with regeneration
10 stream.
According to one embodiment, the plant comprises a single first reactor
and a single second reactor configured in order to be fed sequentially either by
the second system for feeding with reaction stream or by the system for feeding
with regeneration stream; and which, preferably, is configured so that one and
15 the same regeneration stream resulting from the system for feeding with
regeneration stream passes successively into the first reactor and then the
second reactor or passes successively into the second reactor and then the first
reactor.
The invention also relates to a composition comprising
20 tetrafluoropropene and containing, in molar proportions:
- less than 100 pprn of chloromethane; andlor
- less than 100 pprn of 1 ,I-difluoroethane; andlor
- less than 100 pprn of fluoromethane; andlor
- less than 100 pprn of difluoromethane.
According to one embodiment, the tetrafluoropropene is 2,3,3,3-
tetrafluoropropene.
According to one embodiment, the composition contains, in molar
proportions:
- less than 50 pprn of chloromethane; andlor
- less than 50 ppm of 1,l-difluoroethane; andlor
- less than 50 pprn of fluoromethane; andlor
- less than 50 ppm of difluoromethane.
The present invention makes it possible to overcome the disadvantages
of the state of the art. It more particularly provides a process for the
35 manufacture of HFO-1234 (and in particular of HFO-1234yf) which has a high
yield and which provides the desired product in a high degree of purity.
This is accomplished by virtue of the discovery, by the present inventors,
that some fluorination reaction stages can be carried out essentially in the
absence of oxidizing agent, such as oxygen, without the lifetime of the
fluorination catalyst being visibly affected over a predetermined period, so long
5 as intermediate regeneration stages are provided.
An advantage resulting therefrom is that a gaseous stream of HFO-1234
of a higher purity is obtained as it is obtained essentially in the absence of
oxygen during the reaction. The content of carbon oxides and also of
compounds containing one or two carbons is markedly reduced with respect to
10 the state of the art. The downstream treatment and the final purification of the
desired product are thus simplified, guaranteeing that the final product is
obtained preferably with a purity of greater than or equal to 98%,
advantageously of greater than or equal to 99% and very advantageously of
greater than or equal to 99.8% by weight. The hydrochloric acid coproduced is
15 also more easily recovered in value.
BRIEF DESCRIPTION OF THE FIGURES
Figures l a and l b diagrammatically represent an embodiment of a plant
according to the invention with just one catalytic fluorination reactor, in two
20 different operating configurations.
Figures 2a and 2b diagrammatically represent an embodiment of a plant
according to the invention with two catalytic fluorination reactors, in two different
operating configurations.
Figure 3 diagrammatically represents an embodiment of a plant
25 according to the invention with three catalytic fluorination reactors, in a
particular operating configuration.
Figures 4a and 4b diagrammatically represent an embodiment of a plant
according to the invention with just one catalytic fluorination reactor, in two
different operating configurations.
30 Figures 5a and 5b diagrammatically represent an embodiment of a plant
according to the invention with two catalytic fluorination reactors, in two different
operating configurations.
Figure 6 diagrammatically represents an embodiment of a plant
according to the invention with three catalytic fluorination reactors, in a
35 particular operating configuration.
Figures 7 to 11 diagrammatically represent embodiments of plants
according to the invention for the production of HFO-1234yf in two stages.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The invention is now described in more detail and without limitation in the
description which follows.
5 Unless otherwise mentioned, the percentages and proportions shown are
values by weight.
The invention provides for the production of HFO-1234 by catalytic gasphase
fluorination; this catalytic fluorination is, according to the invention,
alternated with the regeneration of the fluorination catalyst. In some
10 embodiments, the invention provides for the production of HFO-1234 in several
fluorination stages.
Fluorination reaction for the production of HFO-1234
The invention provides at least cine fluorination stage, making it possible
15 to produce HFO-1234 from a chlorinated compound.
The HFO-1234 can in particular be HFO-1234yf or else HFO-1234ze
(1,3,3,3-tetrafluoropropene), in the cis or trans form or in the form of a mixture
of cis and trans forms.
"Chlorinated compound is understood to mean an organic compound
20 comprising one or more chlorine atoms. This compound preferably comprises
three carbon atoms.
This chlorinated compound is preferably a propane or a propene having
substituents chosen from F, CI, I and Br (preferably from F and CI) and
comprising at least one CI substituent.
25 It is understood that "chlorinated compound" is also understood to mean
mixtures of compounds.
Preferably, the chlorinated compound is a tetrachloropropene, a
chlorotrifluoropropene, a pentachloropropane or a mixture of these.
In one embodiment, the chlorinated compound is 2-chloro-3,3,3-
30 trifluoropropene (HCFO-1233xf), in order to produce HFO-1234yf.
In another embodiment, the chlorinated compound is 1-chloro-3,3,3-
trifluoropropene (HCFO-1233zd), in order to produce HFO-1234ze.
In another embodiment, the chlorinated compound is 1,1,1,2,3-
pentachloropropane (HCC-240db) or 1,1,2,2',3-pentachloropropane (HCC-
35 240aa), or a mixture of the two, in order to produce HFO-1234yf.
According to yet another embodiment, the chlorinated compound is 2,3-
dichloro-I ,I,I -trifluoropropane (HCFC-243db), in order to produce HFO-1234yf.
According to yet another embodiment, the chlorinated compound is
1 ,I ,2,3-tetrachloropropene (HCO-1230xa) or 2,3,3,3-tetrachloropropene
(HCO-1230xf) or a mixture of these two compounds, in order to produce HFO-
1234yf.
5 The conversion of the chlorinated compound to give HFO-I234 can be a
direct conversion or an indirect conversion (that is to say, involving an
intermediate product).
The fluorination of the chlorinated compound to give HFO-1234 is carried
out in one or more gas-phase fluorination reactors comprising a bed of
10 fluorination catalyst.
The catalyst used can, for example, be based on a metal comprising a
transition metal oxide or a derivative or a halide or an oxyhalide of such a metal.
Mention may be made, for example, of FeC13, chromium oxyfluoride, chromium
oxides (optionally subjected to fluorination treatments), chromium fluorides and
15 their mixtures. Other possible catalysts are catalysts supported on carbon,
catalysts based on antimony or catalysts based on aluminum (for example AIF3
and AI2O3, alumina oxyfluoride and alumina fluoride).
Use may be made, in general, of a chromium oxyfluoride, an aluminum
fluoride, an aluminum oxyfluoride or a supported or unsupported catalyst
20 containing a metal, such as Cr, Ni, Fe, Zn, Ti, V, Zr, Mo, Ge, Sn, Pb, Mg or Sb.
Reference may be made, in this regard, to the document
W0 20071079431 (on p. 7, 1. 1-5 and 28-32), to the document EP 939071
(section [0022]), to the document WO 20081054781 (on p. 9, 1. 22 - p. 10, 1. 34)
and to the document WO 20081040969 (claim I), to which documents reference
25 is expressly made.
The catalyst is more particularly preferably based on chromium and it is
more particularly a mixed catalyst comprising chromium.
According to one embodiment, a mixed catalyst comprising chromium
and nickel is used. The CrINi molar ratio (on the basis of the metal element) is
30 generally from 0.5 to 5, for example from 0.7 to 2, for example approximately 1.
The catalyst can contain from 0.5 to 20% by weight of chromium and from 0.5 to
20% by weight of nickel, preferably from 2 to 10% of each.
The metal can be present in the metallic form or in the form of a
derivative, for example an oxide, halide or oxyhalide. These derivatives are
35 preferably obtained by activation of the catalytic metal.
The support preferably consists of alurninum, for example alumina,
activated alumina or aluminum derivatives, such as aluminum halides and
aluminum oxyhalides, for example described in the document US 4 902 838 or
obtained by the activation process described above.
The catalyst can comprise chromium and nickel in an activated or
nonactivated form, on a support which has or has not been subjected to
5 activation.
Reference may be made to the document WO 200911 18628 (in particular
on p.4, 1. 30 - p. 7, 1. 16), to which reference is expressly made here.
Another preferred embodiment is based on a mixed catalyst containing
chromium and at least one element chosen from Mg and Zn. The Mg or ZnlCr
10 atomic ratio is preferably from 0.01 to 5.
Before its use, the catalyst is preferably subjected to activation with air,
oxygen or chlorine andlor with HF.
For example, the catalyst is preferably subjected to activation with air or
oxygen and HF at a temperature of 100 to 500°C, preferably of 250 to 500°C
15 and more particularly of 300 to 400°C. The activation time is preferably from 1
to 200 h and more particularly from 1 to 50 h.
This activation can be followed by a stage of final fluorination activation in
the presence of an oxidizing agent, of HF and of organic compounds.
The HFIorganic compounds molar ratio is preferably from 2 to 40 and the
20 oxidizing agentlorganic compounds molar ratio is preferably from 0.04 to 25.
The temperature of the final activation is preferably from 300 to 400°C and its
duration is preferably from 6 to 100 h.
The gas-phase fluorination reaction can be carried out:
- with an HFlchlorinated compound molar ratio of 1:l to 150:1,
preferably of 3:l to 100:l and more particularly preferably of 5:l to
50:l;
- with a contact time of 1 to 100 s, preferably 1 to 50 s and more
particularly 2 to 40 s (catalyst volume divided by the total incoming
stream, adjusted to the operating temperature and pressure);
- at an absolute pressure ranging from 0.1 to 50 bar, preferably from
0.3 to 15 bar;
- at a temperature (temperature of the catalyst bed) of 100 to 500°C,
preferably of 200 to 450°C and more particularly of 250 to 400°C.
The stream making up the reaction medium can comprise, in addition to
35 the HF and the chlorinated compound, additional compounds, in particular other
halohydrocarbons or halohydroolefins.
The duration of the reaction stage is typically from 10 to 2000 hours,
preferably from 50 to 500 hours and more particularly preferably from 70 to
300 hours.
According to the invention, the proportion of oxygen optionally present in
5 the reaction medium is less than 0.05 mol% with respect to the chlorinated
compound, more preferably less than 0.02 mol% or less than 0.01 mol%.
Traces of oxygen may possibly be present but the fluorination stage is
preferably carried out essentially in the absence of oxygen or in the complete
absence of oxygen.
10 Preferably, the proportion of any oxidizing agent (such as oxygen and
chlorine) optionally present in the reaction medium is less than 0.05 mol% with
respect to the chlorinated compound, more preferably less than 0.02 mol% or
less than 0.01 mol%. Traces of oxidizing agent may possibly be present, but the
stage is preferably carried out essentially in the absence of oxidizing agent or in
15 the complete absence of oxidizing agent.
The stream of products resulting from the stage of fluorination of the
chlorinated compound to give HFO-1234 can be subjected to appropriate
treatments (distillation, washing, etc.) in order to recover the HFO-1234 in the
purified form and to separate it from the other compounds present (HCI,
20 unreacted HF, unreacted chlorinated compound, other organic compounds).
One or more streams can be subject to a recycling.
The HCI in particular can be subject to a purification according to the
process described in the application FR 13161736, to which reference is
expressly made.
25
Regeneration of the catalyst
In each reactor used for the implementation of the fluorination of the
chlorinated compound to give HFO-1234, said fluorination can be alternated
with phases of regeneration of the catalyst, in the presence of oxygen.
30 It is possible, for example, to pass from the reaction phase to the
regeneration phase when the conversion of the chlorinated compound falls
below a predetermined threshold, for example 50%.
If need be, beforehand, a transition period consisting in decompressing
the reaction gas phase is provided. It can be followed by a phase of flushing
35 with an inert gas or else by placing under vacuum with the aim of completely
removing the reactants present.
The regeneration stream preferably contains at least 1 mol% of oxygen in
total. It can be pure air but the stream can also contain an inert gas of use in
providing a degree of dilution, for example nitrogen, argon, helium or else
hydrofluoric acid in proportions varying from 0 to 95%, preferably from 5 to 85%
5 and more particularly preferably from 10 to 80%. The flow rate of the
regeneration stream is preferably kept sufficiently high to prevent external
diffusional conditions.
The temperature in the regeneration stage has a value, for example, from
100 to 500°C, preferably from 200 to 450°C and more particularly preferably
10 from 250 to 400°C. It may be practical to carry out the regeneration at the same
temperature as the reaction.
The pressure in the regeneration stage has a value, for example, from
atmospheric pressure to 15 bar absolute. It is preferably approximately equal to
atmospheric pressure.
15 The duration of the regeneration stage is typically from 10 to 2000 hours,
preferably from 50 to 500 hours and more particularly preferably from 70 to 300
hours.
The regeneration can be carried out cocurrentwise or countercurrentwise
with respect to the direction of the stream used during the reaction period.
20 This regeneration stage makes it possible to recover the initial activity of
the catalyst. Several cycles can thus be linked together without significantly
detrimentally affecting the activity of the catalyst, which makes it possible to
increase its lifetime.
On conclusion of the regeneration stage, the reactor can be placed under
25 vacuum so as to remove the inert gases and the oxygen introduced, prior to the
reintroduction of the organic compounds.
30 Plants accordina to the invention for the implementation of the fluorination stage
described above
The fluorination stage described above can be carried out with a single
reactor. In this case, the latter is operated alternately in reaction and in
regeneration. Production is then noncontinuous.
35 Otherwise, the fluorination stage described above can be carried out with
a plurality of reactors, for example two, three or more than three reactors. In this
case, it is possible to operate at least one reactor iil reaction while at least one
other is operated in regeneration, and thus optionally to provide continuous
production.
Referring to figures l a and lb, an embodiment with just one reactor is
described.
5 The plant then comprises a reactor 10, capable of being fed either by a
system 2a for feeding with reaction stream or by a system 2b for feeding with
regeneration stream.
Both a system 3a for collecting a stream of products and a system 3b for
collecting a stream of gases resulting from the regeneration are connected at
10 the outlet of the reactor 10.
"System for feeding" and "system for collecting" are understood to mean
a single pipe or an assembly of several pipes.
A system 20 of valves at the inlet and a system 30 of valves at the outlet
are provided in order to make it possible to switch between the respective
15 systems for feeding and for collecting.
During the reaction stage (figure la), the system 20 of valves at the inlet
is positioned in order for the reactor 10 to be fed by the system 2a for feeding
with reaction stream, and the system 30 of valves at the outlet is positioned in
order for the reactor 10 to feed the system 3a for collecting a stream of
20 products, which directs the stream of products toward units for the downstream
treatment of the production gases.
During the regeneration stage (figure I b), the system 20 of valves at the
inlet is positioned in order for the reactor 10 to be fed by the system 2b for
feeding with regeneration stream, and the system 30 of valves at the outlet is
25 positioned in order for the reactor 10 to feed the system 3b for collecting a
stream of gases resulting from the regeneration, which directs the stream of
gases resulting from the regeneration towards units for the downstream
treatment of these gases.
The reactor 10 alternately links together periods of production and of
30 regeneration sequentially. Production is noncontinuous.
Referring to figures 2a and 2b, an embodiment with two reactors is now
described.
In a first configuration (figure 2a), the reaction stage is carried out in a
first reactor 10 and the regeneration stage is carried out in a second reactor 11.
35 In a second configuration (figure 2b), the reaction stage is carried out in the
second reactor 11 and the regeneration stage is carried out in the first reactor
10. In this way, production is continuous.
Each reactor 10, 11 is provided with a system 20, 21 of valves at the
respective inlet and also with a system 30, 31 of valves at the respective outlet
in order to make it possible to pass from one configuration to the other. It is
possible to provide for the system 2a for feeding with reaction stream, the
5 system 2b for feeding with regeneration stream, the system 3a for collecting a
stream of products and the system 3b for collecting a stream of gases resulting
from the regeneration to be shared by the two reactors 10, 11, as illustrated, or
else to provide separate systems dedicated to each reactor 10, 11.
Referring to figure 3, an embodiment with three reactors is now
10 described.
In the configuration illustrated, the reaction stage is carried out in a first
reactor 10, a second reactor I 1 is waiting and the regeneration stage is carried
out in a third reactor 12. The waiting stage is a state in which the reactor has
been regenerated and is ready to be used again in the reaction. In other
15 nonillustrated configurations, the states of the reactors 10, 11, 12 are switched
around. In this way, continuous production can be ensured.
Each reactor 10, 11, 12 is provided with a system 20, 21, 22 of valves at
the respective inlet and also with a system 30, 31, 32 of valves at the respective
outlet in order to make it possible to pass from one configuration to the other. It
20 is possible to provide for the system 2a for feeding with reaction stream, the
system 2b for feeding with regeneration stream, the system 3a for collecting a
stream of products and the system 3b for collecting a stream of gases resulting
from the regeneration to be shared by the three reactors 10, 11, 12 as
illustrated or else to provide distinct systems dedicated to each reactor 10, 11,
25 12.
In the embodiments of figures la, lb, 2a, 2b and 3, the streams in the
reactors are oriented in the same direction for the fluorination and for the
regeneration.
According to alternative forms, the streams in the reactors can be
30 oriented in reverse directions between the fluorination and the regeneration.
Thus, an embodiment is represented in figures 4a and 4b with just one
reactor 10 which is analogous to the embodiment of figures l a and l b , except
that the streams are reversed between the fluorination and the regeneration.
For example, if the system 2a for feeding with reaction stream feeds the reactor
35 10 at the bottom, then the system 2b for feeding with regeneration stream feeds
the reactor 10 at the top (or vice versa). Likewise, if the system 3a for collecting
a stream of products is connected at the top of the reactor 10, then the system
3b for collecting a stream of gases resulting from the regeneration is connected
at the bottom of the reactor 10 (or vice versa).
Likewise, an embodiment is represented in figures 5a and 5b with two
reactors 10, 11 which is analogous to the embodiment of figures 2a and 2b,
5 except that the streams are reversed between the fluorination and the
regeneration. For example, if the system 2a for feeding with reaction stream
feeds the reactors 10, 11 at the bottom, then the system 2b for feeding with
regeneration stream feeds the reactors 10, 11 at the top (or vice versa).
Likewise, if the system 3a for collecting a stream of products is connected at the
10 top of the reactors 10, 11, then the system 3b for collecting a stream of gases
resulting from the regeneration is connected at the bottom of the reactors 10, 11
(or vice versa).
Likewise, an embodiment is represented in figure 6 with three reactors
10, 11, 12 which is analogous to the embodiment of figure 3, except that the
15 streams are reversed between the fluorination and the regeneration. For
example, if the system 2a for feeding with reaction stream feeds the reactors
1 1 12 at the bottom, then the system 2b for feeding with regeneration
stream feeds the reactors 10, 11, 12 at the top (or vice versa). Likewise, if the
system 3a for collecting a stream of products is connected at the top of the
20 reactors 10, 11, 12, then the system 3b for collecting a stream of gases
resulting from the regeneration is connected at the bottom of reactors 10, 11, 12
(or vice versa).
Processes accordincl to the invention in several stages
25 In some embodiments, the invention provides several successive
reaction stages and preferably: first a preliminary stage of the manufacture of
the chlorinated compound mentioned above; then, subsequently, the stage of
fluorination of the chlorinated compound to give HFO-1234.
Preferably, the preliminary stage is itself a fluorination stage.
30 In this case, this stage converts a preliminary compound into the
abovementioned chlorinated compound. In such a case, it should be noted that
the chlorinated compound comprises at least one fluorine atom (since it results
from a fluorination stage) and also at least one chlorine atom (since it is
subsequ6ntly subjected to the fluorination stage describetl above in order to
35 provide HFO-1234).
The 'prelimina~y compound" is advantageously an organic compound
(preferably having three carbon atoms) which comprises at least two chlorine
atoms (and which comprises more chlorine atoms than the "chlorinated
compound")).
The preliminary compound can preferably be a propane or a propene
having substituents chosen from F, CI, I and Br (preferably from F and CI) and
5 comprising at least two CI substituents. A propane is more particularly
preferred.
It is understood that "preliminary compound is also understood to mean
mixtures af compounds.
According to a preferred embodiment, the preliminary compound is HCC-
10 240db or HCC-240aa or a mixture of the two and the chlorinated compound is
HCFO-1233xf, in order to produce HFO-1234yf.
According to yet another embodiment, the preliminary compound is
HCFC-243db and the chlorinated compound is HCFO-1233xf, in order to
produce HFO-1234yf.
15 According to yet another embodiment, the preliminary compound is
HCO-1230xa or HCO-1230xf or a mixture of these two compounds and the
chlorinated compound is HCFO-1233xf, in order to produce HFO-1234yf.
The conversion of the preliminary compound into the chlorinated
compound can be a direct conversion or an indirect conversion (that is to say,
20 involving an intermediate product).
It is possible to carry out the fluorination of the preliminary compound to
give a chlorinated compound in the liquid phase. However, preferably, the
fluorination is a gas-phase fluorination, in the presence of a fluorination catalyst.
It can be carried out in one or more fluorination reactors in series or in parallel.
25 The fluorination catalyst can be of the same type as described above for
the fluorination of the chlorinated compound to give HFO-1234. The above
description relating to the activation of the catalyst also applies.
The reaction for the fluorination in the gas phase of the preliminary
compound to give a chlorinated compound can in particular be carried out:
- with an HFlorganic compounds molar ratio of 3:l to 100:1, preferably
of 5:l to 50:l (the term "organic compounds" denotes all of the
compounds of the reaction medium comprising one or more carbon
atoms);
- at an absolute pressure ranging from 0.1 to 50 bar, preferably from
35 0.3 to 15 bar;
- with a contact time of 1 to 100 s, preferably of 1 to 50 s and more
particularly of 2 to 40 s (catalyst volume divided by the total incoming
stream, adjusted to the operating temperature and pressure);
- at at temperature (temperature of the catalyst bed) of 100 to 500°C,
preferably of 200 to 450°C and more particularly of 250 to 400°C.
The stream making up the reaction medium can comprise, in addition to
the HF and the preliminary compound, additional compounds, in particular other
halohydrocarbons or halohydroolefins. The stream can, for example, already
comprise an HFO-1234 fraction.
10 According to a preferred embodiment, there is no or essentially no
oxygen (and optionally there is no or essentially no other oxidizing agent) in the
reaction medium.
Thus, the presence of oxygen or of oxidizing agent in the subsequent
fluorination stage is also avoided, without having to carry out an intermediate
15 separation of a stream of oxygen or oxidizing agent.
The duration of the stage of reaction of the preliminary compound to give
a chlorinated compound is typically from 10 to 2000 hours, preferably from 50 to
500 hours and more particularly preferably from 70 to 300 hours.
On conclusion of this reaction stage, a stream of products is collected
20 which comprises in particular chlorinated compound, unreacted preliminary
compound, HF, HCI, optionally HFO-1234 and optionally secondary products,
such as in particular 1 ,I ,I ,2,2-pentafluoropropane (HFC-245cb).
This stream of products can subsequently directly feed the stage of
fluorination of the'chlorinated compound to give HFO-1234yf described above.
25 Alternately, this stream of products can be separated, for example by
distillation, to provide, for example, a first stream comprising HCI and optionally
HFO-1234 and a second stream comprising HF and chlorinated compound. The
distillation can, for example, be carried out at a temperature of -90 to 150"C,
preferably of -85 to 10O0C, and at a pressure of 0.1 to 50 bar abs and preferably
30 of 0.3 to 5 bar abs.
The first stream can be directed to a unit for the production of acid in
order to produce HCI and HFO-1234. The HFO-I234 and the intermediate
products can be recovered by known means, such as extraction, washing,
separation by settling and preferably distillation means.
35 It should be noted that, according to the invention, at least one of the two
fluorination stages described above is alternated with a stage of regeneration of
the reactor or reactors with a stream of oxidizing agent, as described above in
connection with the fluorination of the chlorinated compound to give HFO-1234.
The above description thus applies by analogy (including that relating to the
different possible plants illustrated in figures l a to 6):
- either to the regeneration alternated with the fluorination of the
preliminary compound to give a chlorinated compound;
- or to the regeneration alternated with the fluorination of the
chlorinated compound to give HFO-1234;
- or both to the regeneration alternated with the fluorination of the
preliminary compound to give a chlorinated compound and to the
regeneration alternated with the fluorination of the chlorinated
compound to give HFO-1234.
Depending on the reaction conditions and the nature of the catalyst, the
tendency of the catalyst to become deactivated can be different, hence these
various possible scenarios.
15
Processes for the manufacture of HFO-1234yf in two stages
A description is now given of various embodiments in connection with the
manufacture of HFO-1234yf in two stages starting from HCC-240db (it being
understood that it is also possible instead to use HCC-240aa or a mixture of the
20 two): a first stage of conversion of HCC-240db to give HCFO-1233xf and then a
second stage of conversion of HCFO-1233xf to give HFO-1234yf, which stages
are carried out in successive reactors.
Referring to figure 7, according to one embodiment, a plant according to
the invention can thus comprise a first fluorination reactor 40 for the
25 implementation of the stage of preparation of HCFO-1233xf. It is understood
that it is also possible instead to use a plurality of reactors, operating in series
andlor in parallel.
This first fluorination reactor 40 is fed by a first system 39 for feeding with
reaction medium (comprising HF and HCC-240db).
30 A system 41 for collecting a stream of products is positioned at the outlet
of the first fluorination reactor 40, which collecting system feeds a separation
unit 42. This separation unit 42 can in particular be a distillation unit as
described above.
A first collecting pipe 43 and a second collecting pipe 44 are provided at
35 the outlet of the separation unit 42. The first collecting pipe 43 is configured in
order to transport a stream comprising in particulal- HCI and HFO-1234yf and
the second collecting pipe 44 is configured in order to transport a stream
comprising in particular HF and HCFO-1233xf.
The first collecting pipe 43 feeds additional treatment units, not
represented, which can in particular comprise a unit for the production of acid,
while the second collecting pipe 44 provides for recycling toward at least one
second gas-phase fluorination reactor 48 which is used for the fluorination of
HCFO-1233xf to give HFO-12349. This second collecting pipe 44 can thus also
be described as a recycling pipe. This second reactor 48 is fed by a second
system 46 for feeding with reaction medium, which itself is fed by the second
collecting pipe 44, on the one hand, and by a system 45 for feeding with HF, on
the other hand.
An intermediate collecting system 47 is connected at the outlet of the
second reactor 48. This collecting system in turn feeds the first system 39 for
feeding with reaction medium of the first reactor 40. HCC-240db is supplied by
a system 38 for feeding with HCC-240db.
Preferably, in this plant and in all the fluorination stages, the proportion of
oxygen optionally present in the streams is less than 0.05 mol% with respect to
the predominant organic compound, more preferably less than 0.02 mol% or
less than 0.01 mol%. Traces of oxygen may possibly be present but, preferably,
the whole of the process for the fluorination of HCC-240db to give HFO-1234yf
is carried out essentially in the absence of oxygen or in the complete absence
of oxygen.
Preferably, the proportion of any oxidizing agent (such as oxygen and
chlorine) optionally present in the reaction medium is less than 0.05 mol% with
respect to the predominant organic compound, more preferably less than
0.02 mol% or less than 0.01 mol%. Traces of oxidizing agent may optionally be
present but, preferably, the entire process for the fluorination of HCC-240db to
give HFO-1234yf is carried out essentially in the absence of oxidizing agent or
in the complete absence of oxidizing agent.
In accordance with the invention, regeneration of the catalyst is provided,
alternating with the fluorination. This regeneration can concern either the first
reactor 40 or the second reactor 48 or both the reactors 40, 48. The
regeneration is carried out as described above, using a stream of oxidizing
agent. The means necessary for the regeneration are not represented in
figure 7 but are analogous to those described above.
An alternative form is illustrated in figure 8. It is identical to the
embodiment of figure 7 except that, instead of a single second reactor 48, two
second reactors 48a, 48b are provided. These are configured to operate
alternately in fluorination mode and in regeneration mode, as described above
in connection with figures 2a and 2a.
Thus, by controlling a system 20, 21 of valves at the inlet and a system
5 30, 31 of valves at the outlet, it is arranged that:
- in one phase, one of the second reactors 48a operates in fluorination
mode, that is to say is fed by the second system 46 for feeding with
reaction medium and feeds the intermediate collecting system 47,
while the other of the second reactors 48b operates in regeneration
mode, that is to say is fed by a system 49 for feeding with
regeneration stream and itself feeds a system 50 for collecting a
stream of gases resulting from the regeneration;
- in another phase, the configurations of the two reactors 48a, 48b are
reversed.
15 It should be noted that, in figure 8, a regeneration which is carried out in
the same direction as the fluorination has been represented. However, the
streams can also be reversed, as described in connection with figures 5a and
5b.
Another alternative form is illustrated in figure 9. It is identical to the
20 embodiment of figure 8 except that not only are two second reactors 48a, 48b
provided but also two first reactors 40a, 40b are provided instead of a single
first reactor. These two first reactors are configured in order to operate
alternately in fluorination mode and in regeneration mode, as described above
in connection with figures 2a and 2b.
25 In a first phase, which is that illustrated in the figure, the second system
46 for feeding with reaction medium feeds one of the two second reactors 48a.
The intermediate collecting system 47 is connected at the outlet of this second
reactor 48a, which makes it possible to collect a stream of intermediate
products. This feeds the first system 39 for feeding with reaction medium (also
30 with the system 38 for feeding with HCC-240db), which itself feeds one of the
two first reactors 40a.
The system 41 for collecting a stream of products is connected at the
outlet of this first reactor 40a.
The system 49 for feeding with regeneration stream feeds the other
35 second reactor 48b, preferably simultaneously. A system 52 for the intermediate
collecting of a stream of gases resulting from the regeneration is connected at
the outlet of this second reactor 48b and feeds, at the inlet, the other first
reactor 40b. The system 50 for the intermediate collecting of a stream of gases
resulting from the regeneration is connected at the outlet of this first reactor
40b.
Alternatively, intermediate feeding with an additional regeneration stream
5 can be provided between the two reactors 48b, 40b. Alternatively again,
regeneration by streams independent of these two reactors 48b, 40b can be
provided.
Alternately again, regeneration with streams in the reverse direction to
those of the fluorination can be provided, according to the principles of figures
l o 5a and 5b.
In a second phase, not illustrated, the fluorination and regeneration
configurations are reversed between the reactors.
The change from one configuration to the other is provided by means of
an assembly of valves: in the example illustrated, the valves are valves 20, 21
15 at the inlet 20, 21, which are located upstream of the second reactors 48a, 48b,
valves at the outlet, which are located downstream of the first reactors 40a, 40b,
and finally an HCC-240db valve 51 located at the system 38 for feeding with
HCC-240db.
Another alternative form is illustrated in figure 10. It is analogous to the
20 embodiment of figure 7. In this alternative form, sequential regeneration with
respect to the fluorination (and not simultaneous regeneration) is provided, on
just one of the two reactors, namely the second reactor 48.
To this end, the system 49 for feeding with regeneration stream is
connected at the inlet of the second reactor 48 and the system 50 for collecting
25 a stream of gases resulting from the regeneration is connected at the outlet of
the second reactor 48. A system 20 of valves at the inlet and a system 30 of
valves at the outlet makes it possible to switch the second reactor 48, either into
fluorination mode or into regeneration mode.
It should be noted that the fluorination and regeneration streams can be
30 in the same direction or in the opposite direction.
It should also be noted that it is also possible to provide the same means
for ensuring the regeneration at the first reactor 40, either in addition to or as a
replacement for the regeneration means of the second reactor 48.
Another alternative form is illustrated in Figure 11. It is analogous to the
35 embodiment of figure 7. In this alternative form, sequential regeneration with
respect to the fluorination (and not simultaneous regeneration) is provided, on
the two reactors simultaneously, namely the first reactor 40 and the second
reactor 48.
To this end, the system 49 for feeding with regeneration stream is
connected at the inlet of the second reactor 48 and the system 50 for collecting
5 a stream of gases resulting from the regeneration is connected at the outlet of
the first reactor 40. A system 20 of valves at the inlet and a system 30 of valves
at the outlet makes it possible to switch the reactors 40, 48, either into
fluorination mode or into regeneration mode.
It should be noted that the fluorination and regeneration streams can be
10 in the same direction or in the opposite direction.
Everything which has been described here in connection with the
preparation of HFO-1234yf in two stages can be read analogously by replacing
HCC-240db with another starting preliminary compound (and by replacing
HCFO-1233xf with another chlorinated compound). Likewise, that which has
15 been described here can be applied analogously to the preparation of other
HFO-1234 compounds.
Another possibility for the implementation of the invention consists in: on
the one hand, producing chlorinated compound from the preliminary compound
(for example HCFO-1233xf from HCC-240db or similar) and, on the other hand,
20 producing HFO-1234 from chlorinated compound (for example HFO-1234yf
from HCFO-1233xf), this being done independently and separately, for example
by isolating, storing andlor transporting the chlorinated compound between the
two stages, and by carrying out the alternating regeneration according to the
invention on the first stage or the second stage or both, independently.
25
Products obtained
The consequence of the absence or virtual absence of oxygen during the
reaction phase is the decrease in the content of impurities related to the
30 combustion or decomposition reactions of the molecules. The impurities are
carbon oxides or dioxides and also the molecules containing fewer carbon
atoms than the starting chlorinated product.
Thus, the invention makes it possible to obtain a stream of HFO-I234
(and in particular of HFO-1234yf) containing less chloromethane (HCC-40) and
35 1,l-difluoroethane (HFC-152a) than in the state of the art. In point of fact, these
compounds form an azeotrope with HFO-1234yf, which makes them difficult to
purify.
The invention also makes it possible to obtain a stream of HFO-1234
(and in particular of HFO-1234yf) containing less fluoromethane (HFC-41) and
difluoromethane (HFC-32) than in the state of the art. In point of fact, it is known
that these compounds are extremely flammable.
5 The molar proportion of each of these compounds in the HFO-1234
stream is thus preferably less than 100 ppm and more particularly less than
50 ppm.
According to one embodiment, this stream contains HFO-1234
(preferably HFO-1234yf) and also from 1 to 50 ppm of HCC-40, from 1 to
10 50 ppm of HFC-152a, from 1 to 50 ppm of HFC-41 and from 1 to 50 ppm of
HFC-32.
According to one embodiment, this stream is essentially devoid and
preferably is devoid of HCC-40.
According to one embodiment, this stream is essentially devoid and
15 preferably is devoid of HFC-152a.
According to one embodiment, this stream is essentially devoid and
preferably is devoid of HFC-41.
According to one embodiment, this stream is essentially devoid and
preferably is devoid of HFC-32.
20 According to one embodiment, this stream contains at least 98% of
HFO-1234, preferably at least 99% and in particular at least 99.5%, indeed
even at least 99.8%, by weight.
The HFO-1234 streani under consideration is either the stream obtained
at the outlet of the reactor for the fluorination of the chlorinated compound to
25 give HFO-1234 (stream withdrawn in the system 3a for collecting a stream of
product in the figures), or the stream obtained at the outlet of the separation unit
(stream withdrawn in the first collecting pipe 43 in the figures), or the stream
obtained later still after separation of the HFO-1234 and the hydrochloric acid.
Furthermore, the absence or virtual absence of oxygen also makes it
30 possible to obtain a stream of hydrochloric acid with a greater purity which
makes possible easier recovery in value. Thus, the stream of hydrochloric acid
recovered after separation from HFO-1234 is preferably devoid (or essentially
devoid) of trifluoroacetic acid, of COF;, or of COFCI.
35 EXAMPLES
The following examples illustrate the invention without limiting it
A gas-phase fluorination reactor equipped with feeding with HF, with
feeding with fresh organic products, with available feeding for the cofeeding of
another gaseous compound and with a pipe for feeding resulting from the
recycling of the unconverted reactants is available.
5 The outflow of the gas stream resulting from this reactor is sent to a pipe
cooled with a jacket which makes it possible to cool and partially condense the
reaction products before they are introduced into the distillation column. The
partially condensed stream is thus conveyed to a distillation column with a
height of 1.5 m filled with a metal packing of Sulzer type which facilitates the
10 exchanges between the ascending gas stream and the descending liquid reflux.
The distillation column is equipped with a boiler at the column bottom and with a
condensation system at the top. This separation unit makes it possible to
separate a top stream which predominantly consists of the desired product
(HFO-1234yf) and of the byproduct HCI. Greater or lesser amounts of byproduct
15 HFC-245cb are also present. The column bottom stream predominantly
consists of HF and of unconverted reactant (HCFO-1233x9 and also of the
byproduct HFC-245cb resulting from the addition of HF to HFO-1234yf. This
column bottom stream is subsequently recycled to the gas-phase reactor.
Traces of impurities are present in each of the streams.
20 180 ml of bulk chromium-based catalyst are introduced into the reactor
made of lnconel. It is first subjected to a period of drying under 50 llh of nitrogen
at atmospheric pressure at 275°C overnight. Subsequently, while maintaining
the nitrogen and still at 275"C, a stream of HF is gradually added until a flow
rate of 1 mollh is obtained. This treatment is maintained overnight. The nitrogen
25 is subsequently halted and the temperature of the oven is increased to 350°C.
The treatment under pure HF is thus also maintained overnight. Finally, a
treatment under 5 l/h of air is applied for at least 24 h.
Following the treatment for activation of the catalyst, the reactants
HCFO-1233xf and HF are introduced into the recycling loop so as to fill this part
30 of the plant while retaining a molar ratio of the hydrofluoric acid to the organic
compound of 25. Initiation is carried out by feeding the liquid present in the
recycling loop to the gas-phase reactor (a preheater ensures the prior
vaporization of the reactants). The system subsequently gradually becomes
equilibrated between the unconverted reactants, which are recycled, the
35 products formed, which are discharged from and collected outside the system,
and the fresh reactants, which are continuously fed so as to compensate
exactly for the amount of products discharged. The level of liquid in the
distillation column thus remains constant.
The conversion of the catalyst changes over time and gradually
decreases. When the conversion falls below 50%, a regeneration treatment with
5 air is applied to the catalyst. This treatment makes it possible to fully recover the
initially activity of the catalyst.
The conversion is calculated from the molar content of HCFO-1233xf
measured at the inlet of the reactor (sum of the recycling and fresh organic
compound streams) and from the content of HCFO-1233xf measured at the
10 outlet of the reactor.
Example 1 -Catalytic results in the presence of air
A test is carried out under the following operating conditions: the catalyst
is freshly regenerated, the molar ratio of HF to the organic compounds is 25, the
15 gas-phase contact time is 15 seconds, the temperature is 350°C and 10 mol%
of oxygen are added with respect to the sum of the organic compounds
introduced. The conversion of the HCFO-1233xf obtained over time is given in
table 1 below. During this test, the gas stream exiting from the top of the
distillation column is analyzed by gas chromatography. The analysis is given in
20 table 2 below (value as % of GC area).
Example 2 - Catalytic results without air
The procedure of example 1 is taken up again but without addition of
supplementary oxygen to the gas phase. The results obtained for the
25 conversion over time are given in table 1 below. The analysis of the gas stream
exiting from the distillation column is given in table 2 below (value as % of GC
area). The carbon oxides and the C1 and C2 impurities are markedly reduced.
The purity of the sum of the desired product HFO-1234yf and of the recyclable
byproduct HFC-245cb increases.
30
Example 1
Time (h)
4
8
12
16
Example 2
Conversion of
HCFO-1233xf (%)
78.6
77.4
76.3
77.2
Time (h)
15
19
24
27
Conversion of
HCFO-1233xf (%)
77.6
78.5
77.8
78.3
Table 1
Table 2
Nd: not detected
1. A process for the manufacture of tetrafluoropropene, comprising,
alternately:
- at least one stage of reaction of a chlol-inated compound with
hydrofluoric acid in the gas phase, in the presence of a
fluorination catalyst, the proportion of oxygen optionally
present being less than 0.05 mol% with respect to the
chlorinated compound;
- a stage of regeneration of the fluorination catalyst by bringing
the fluorination catalyst into contact with a regeneration stream
comprising an oxidizing agent.
2. The process as claimed in claim 1, in which the stage of reaction
of the chlorinated compound with hydrofluoric acid is carried out
essentially in the absence of oxygen and preferably essentially in
the absence of any oxidizing agent.
3. The process as claimed in claim 1 or 2, in which the regeneration
stream contains at least 1 mol% of oxygen with respect to the total
regeneration stream.
4. The process as claimed in one of claims 1 to 3, in which the stage
of reaction of the chlorinated compound with hydrofluoric acid is
carried out in a single reactor, separately in time with respect to
the stage of regeneration of the fluorination catalyst.
5. The process as claimed in one of claims 1 to 3, in which the stage
of reaction of the chlorinated compound with hydrofluoric acid is
carried out in at least one first reactor, simultaneously with the
implementation of the stage of regeneration of the fluorination
catalyst in at least one second reactor.
6. The process as claimed in one of claims 1 to 5, in which the
tetrafluoropropene is 2,3,3,3-tetrafluoropropene.
7. The process as claimed in one of claims 1 to 5, in which the
tetrafluoropropene is 1,3,3,3-tetrafluoropropene.
8. The process as claimed in one of claims 1 to 7, in which the
chlorinated compound is chosen from tetrachloropropenes,
chlorotrifluoropropenes, pentachloropropanes and mixtures of
these.
9. The process as claimed in one of claims 1 to 6 and 8, in which the
chlorinated compound is 2-chloro-3,3,3-trifluoropropene and the
tetrafluoropropene is 2,3,3,3-tetrafluoropropene.
10. The process as claimed in one of claims 1 to 6 and 8, in which the
chlorinated compound is 1 , I, I,2 ,3-pentachloropropane andlor
1,1,2,2,3-pentachloropropane and the tetrafluoropropene is
2,3,3,3-tetrafluoropropene.
11. The process as claimed in one of claims 1 to 5 and 7 and 8, in
which the chlorinated compound is I-chloro-3,3,3-trifluoropropene
and the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.
12. The process as claimed in one of claims 1 to 11, comprising:
- a preliminary stage of manufacture of the chlorinated
compound, which is preferably a preliminary stage of reaction
of a preliminary compound with hydrofluoric acid in the gas
phase, in the presence of a preliminary fluorination catalyst,
the proportion of oxygen optionally present being less than
0.05 mol% with respect to the preliminary compound.
13. The process as claimed in claim 12, in which the preliminary stage
of reaction is carried out alternately with:
- a stage of regeneration of the preliminary fluorination catalyst
by bringing the preliminary fluorination catalyst into contact
with a regeneration stream comprising an oxidizing agent.
14. The process as claimed in either of claims 12 and 13, in which the
preliminary compound is 1 ,I ,I ,2,3-pentachloropropane andlor
1,1,2,2,3-pentachloropropane, the chlorinated compound is
I-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is
2,3,3,3-tetrafluoropropene.
15. The process as claimed in one of claims 12 to 14, comprising:
- the collecting of a stream of products on conclusion of the
preliminary reaction stage;
- the separation of the stream of products into a first stream
comprising hydrochloric acid and tetrafluoropropene and a
second stream comprising hydrofluoric acid and the
chlorinated compound;
- the use of said second stream to carry out the stage of
reaction of the chlorinated compound with hydrofluoric acid;
and
- optionally, the collecting of a stream of products on conclusion
of the stage of reaction of the chlorinated compound with
hydrofluoric acid and the recycling of the latter in the
preliminary reaction stage.
16. A plant for the manufacture of tetrafluoropropene, comprising at
least one gas-phase fluorination reactor (10) comprising a bed of
fluorination catalyst, said gas-phase fluorination reactor (10) being
configured in order to be fed alternately by:
- a system (2a) for feeding with reaction stream (2a) comprising
a chlorinated compound and hydrofluoric acid, the proportion
of oxygen optionally present in this reaction stream being less
than 0.05 mol% with respect to the chlorinated compound; and
- a system (2b) for feeding with regeneration stream comprising
an oxidizing agent.
17. The plant as claimed in claim 16, in which the reaction stream is
essentially devoid of oxygen and preferably of any oxidizing agent.
18. The plant as claimed in claim 16 or 17, in which the regeneration
stream contains at least 1 mol% of oxygen with respect to the total
regeneration stream.
19. The plant as claimed in one of claims 16 to 18, comprising a single
reactor (10) configured in order to be fed alternately by the system
(2a) for feeding with reaction stream and the system (2b) for
feeding with regeneration stream.
20. The plant as claimed in one of claims 16 to 18, comprising a
plurality of reactors (10, 11, 12), each being configured in order to
be fed alternately by a system (2a) for feeding with reaction
stream and a system (2b) for feeding with regeneration stream.
21. The plant as claimed in claim 20, configi~red so that, when a
reactor (10) is fed by the system (2a) for feeding with reaction
stream, another reactor (1 1) is fed by the system (2b) for feeding
with regeneration stream.
22. The plant as claimed in one of claims 16 to 21, configured so that:
- the system (2a) for feeding with reaction stream feeds the
reactor (10) at the bottom and the system (2b) for feeding with
regeneration stream feeds the reactor (10) at the bottom; or
- the system (2a) for feeding with reaction stream feeds the
reactor (10) at the bottom and the system (2b) for feeding with
regeneration stream feeds the reactor (10) at the top; or
- the system (2a) for feeding with reaction stream feeds the
reactor (10) at the top and the system (2b) for feeding with
regeneration stream feeds the reactor (10) at the bottom; or
- the system (2a) for feeding with reaction stream feeds the
reactor (10) at the top and the system (2b) for feeding with
regeneration stream feeds the reactor (10) at the top.
23. The plant as claimed in one of claims 16 to 22, in which:
- the tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or
- the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.
24. The plant as claimed in one of claims 16 to 23, in which the
chlorinated compound is chosen from tetrachloropropenes,
chlorotrifluoropropenes, pentachloropropanes and mixtures of
these; and preferably:
- the chlorinated compound is 2-chloro-3,3,3-trifluoropropene
and the tetrafluoropropene is 2,3,3,3-tetrafluoroprop&e; or
- the chlorinated compound is 1,1,1,2,3-pentachloropropane
andlor 1 ,I ,2,2,3-pentachloropropane and the
tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or
- the chlorinated compound is 1-chloro-3,3,3-trifluoropropene
and the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.
25. The plant as claimed in one of claims 16 to 24, comprising:
- at least one unit for the manufacture of chlorinated compound,
which preferably is at least one preliminary fluorination reactor
(40); configured in order to be fed by:
- a system (39) for feeding with reaction medium comprising a
preliminary compound and hydrofluoric acid, the proportion of
oxygen optionally present in this reaction stream being less
than 0.05 mol% with respect to the preliminary compound.
26. The plant as claimed in claim 25, in which the preliminary
fluorination reactor (40) is also configured in order to be fed by a
system (49) for feeding with regeneration stream comprising an
oxidizing agent.
27. The plant as claimed in either of claims 25 and 26, in which the
preliminary compound is 1 ,I ,I ,2,3-pentachloropropane andlor
1,1,2,2,3-pentachloropropane, the chlorinated compound is
1-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is
2,3,3,3-tetrafluoropropene.
28. The plant as claimed in one of claims 16 to 27, comprising:
- at least one first catalytic fluorination reactor (40);
- at least one second catalytic fluorination reactor (48);
- a system (41) for collecting a stream of products connected at
the outlet of the first catalytic fluorination reactor (40);
- a separation unit (42) fed by the system (41) for collecting a
stream of products;
- a first collecting pipe (43) and a second collecting pipe (44)
which are connected at the outlet of the separation unit (42),
the first collecting pipe (43) being configured in order to
transport a stream comprising hydrochloric acid and
tetrafluoropropene and the second collecting pipe (44) being
configured in order to transport a stream comprising
hydrofluoric acid and chlorinated compound;
- an intermediate collecting system (47) connected at the outlet
of the second reactor (48);
- a first system (39) for feeding with reaction medium configured
in order to feed the first reactor (40), this being itself fed by the
intermediate collecting system (47);
- a second system (46) for feeding with reaction medium
configured in order to feed the second reactor (48), this being
itself fed by the second collecting pipe (44);
- a system (49) for feeding with regeneration stream configured
in order to feed the first reactor (40) andlor the second reactor
(48); and
- a system (50) for collecting a stream of gases stream resulting
from the regeneration (50).
29. The plant as claimed in claim 28, which comprises at least two
second reactors (48a, 48b) configured so that, when one of these
reactors (48a) is fed by the second system (46) for feeding with
reaction stream, the other reactor (48b) is fed by the system (49)
for feeding with regeneration stream.
30. The plant as claimed in claim 28, which comprises at least two first
reactors (40a, 40b) and two second reactors (48a, 48b) configured
so that, when one of the first reactors (40a) and one of the second
reactors (48a) are respectively fed by the first system (39) for
feeding with reaction stream and the second system (46) for
feeding with reaction stream, the other first reactor (40b) and the
other second reactor (48b) are fed by the system (49) for feeding
with regeneration stream; and which, preferably, is configured so
that one and the same regeneration stream resulting from the
system (49) for feeding with regeneration stream passes
successively into the first reactor (40b) and then the second
reactor (48b) or passes successively into the second reactor (48b)
and then the first reactor (40b).
31. The plant as claimed in claim 28, which comprises a single second
reactor (48) configured in order to be fed sequentially either by the
second system (46) for feeding with reaction stream or by the
system (49) for feeding with regeneration stream.
32. The plant as claimed in claim 28, which comprises a single first
reactor (40) and a single second reactor (48), configured in order
to be fed sequentially either by the second system (46) for feeding
with reaction stream or by the system (49) for feeding with
regeneration stream; and which, preferably, is configured so that
one and the same regeneration stream resulting from the system
(49) for feeding with regeneration stream passes successively into
the first reactor (40) and then the second reactor (48) or passes
successively into the second reactor (48) and then the first reactor
(40).
33. A composition comprising tetrafluoropropene and containing, in
molar proportions:
- less than 100 pprn of chloromethane; andlor
- less than 100 pprn of I ,I-difluoroethane; andlor
- less than 100 pprn of fluoromethane; andlor
- less than 100 pprn of difluoromethane.
34. The composition as. claimed in claim 33, in which the
tetrafluoropropene is 2,3,3,3-tetrafluoropropene.
35. The composition as claimed in claim 33 or 34, containing, in molar
proportions:
- less than 50 pprn of chloromethane; andlor
- less than 50 pprn of 1,l-difluoroethane; andlor
- less than 50 ppm of fluoromethane; andlor
- less than 50 ppm of difluoromethane.