FR2607132A1 - Catalytic process for the manufacture of propionyl fluoride - Google Patents

Abstract

Catalytic process for the manufacture of propionyl fluoride from carbon monoxide, hydrogen fluoride and a flow of aliphatic hydrocarbons comprising propane as the main component. It comprises the following sequence of stages: a) introduction of at least one fluid chosen from carbon monoxide and the said hydrocarbon flow into a reactor in the presence of a super acid consisting of hydrogen fluoride and of antimony pentafluoride SbF5, b) if appropriate, if it has not already been introduced during stage a, introduction into the reactor of a fluid chosen from carbon monoxide and the said hydrocarbon flow under conditions suitable for making possible the formation, as main component, of a complex consisting of the propionyl cation and of the SbF6<-> anion, c) conversion of the said complex to propionyl fluoride, d) separation of the propionyl fluoride, and e) recovery of the super acid. Application to the manufacture of propionic acid.

Description

CATALYTIC PROCESS FOR MANUFACTURING PROPIONYL FLUORIDE.

US-A-4,582,571 mentions the possibility of forming isobutyryl fluoride by reaction of carbon monoxide, ae propane, annyor hydrogen fluoride and ae antimony dentafluoride under a pressure greater than 100 bars and at a temperature close to 1000C.

The problem which the present invention has attempted to solve consists in the manufacture of Driopionyl fluoride from propane.

Initially, the applicant undertook the study of the carbonylation of propane in the presence of different superacid systems in order to determine a system capable of leading, in an efficient and economical manner, to obtaining ae DroDionyl fluoride. In a second step, the applicant undertook the study of the separation of the compound obtained in order to determine a means capable of ensuring the regeneration of the chosen superacid.

The process according to the invention is thus defined as a catalytic process for the manufacture of propionyl fluoride from carbon monoxide, hydrogen fluoride and a stream of aliphatic hydrocarbons comprising propane as the main title, characterized by the succession of the following steps (a) introauction of at least one fluid chosen from carbon monoxide and
said stream of hydrocarbons in a reactor in the presence of a superacid
consisting of hydrogen fluoride and antimony pentafluoride SoFs, (D) if applicable, if it has not already been introduced during step (a),
introduction into the reactor of a fluid chosen from
carbon and said hydrocarbon stream, under conditions specific to
allow the formation of a complex consisting of the propionyl cation and
SbF6 anion,
(c) conversion of said complex to propionyl fluoride,
(a) separation of propionyl fluoride,
(e) superacid recovery, and
(f) if necessary, adjusting the quantity of hydrogen fluoride to the
constitution of the superacid used in step (a).

Thus the method according to the invention necessarily comprises the four stages designated (a), (c), (d) and (e). In this case the carbon monoxide and the stream comprising the main propane are introduced
simultaneously in the reactor. Alternatively it may not be necessary
re simultaneously bringing the carbon monoxide and the stream comprising the propane as the main title in the presence of the superacid. In this second case, the carbon monoxide and said stream of hydrocarbons will be introduced separately into the reactor by virtue of the additional step (D).

For a good understanding of the invention, it should be specified that - by "propane as a principal" is meant that the flow of hydrocarbons ali
phatics may include, besides propane, small proportions of at least
very alkanes, alkenes or alkynes having a low number of carbon atoms
ne, such as in particular ethane, butane or propyne, as well as a
minority proportion of propylene.

- By "propionyl cation mainly" means that the reaction engen
due to the superacid system mainly leads to the formation of
this cation (also called ethyloxocarbonium), next to mid proportions
neures of the isobutyryl cation and of carbocations either derived from other
aliphatic hydrocarbons possibly present in the reaction medium
tional either from rearrangements of the propionyl cation or of said charDocations.

Moreover, the content of the description which follows is intended to specify the embodiment of each of the steps of the process according to the present invention. The purpose of step (a) is to bring either the carbon monoxide, or the stream comprising the main propane, or their mixture, into contact with the superacid system. This bringing together takes place in a reactor which may be of the autoclave type or else of the tubular type or any other type suitable for bringing the reactants into contact.

On the other hand, when the said reagent (s) are introduced into the reactor, the latter already contains the superacid system. This comprises hydrogen fluoride and antimony pentafluoride SDF5 in proportions such that they constitute a homogeneous phase.

During step (o), optional as indicated above, the other component is introduced into the reactor. It is only from this moment that, carbon monoxide and propane being in contact with the superacid, a complex consisting of the propionyl cation and the anion SbF6 will begin to form mainly. The presence of said cation is confirmed by sampling the reaction medium at this stage and analysis, in particular by Droton nuclear magnetic resonance. By this analysis, a spectrum is obtained comprising on the one hand a triplet at approximately 2.2 ppm (3H) and on the other hand a quadruple at approximately 4.3 ppm (2H). more efficiently possible, it is desirable that the operating conditions in the reactor be chosen as follows - a CO / C3H8 molar ratio at least equal to 1.5 and preferably comprised
between 2 and 30.

- an HF / SDF5 molar ratio of between 1 and 30 approximately, - a temperature of between -80 C and +60 "C approximately,
The complex formed at the end of step (b) is used, in particular by virtue of the embodiment described below, to manufacture the ae propionyl fluoride. According to this embodiment of the process according to the invention, the complex is converted into ae propionyl fluoride by the intervention of at least one means for shifting the equilibrium between said complex and the ae propionyl fluoride towards the formation of the latter. intervention, in the context of step (c), to displace this chemical equilibrium, mention may in particular be made of the addition of a chemical species capable of significantly reducing the acidity of the reaction medium. Among such species, hydrogen fluoride will be chosen ae. Intervention means of a physical nature, for example thermal, can also be envisaged in the context of step (c).

The aforementioned chemical balance having been sufficiently displaced, it is then appropriate in step (a) to separate a substantial proportion of the propionyl fluoride from the other constituents of the reaction medium. Knowing the boiling temperatures at atmospheric pressure of hydrogen fluoride (20 "C), antimony pentafluoride (1500C) and ae propionyl fluoride, as well as the respective amounts of the various components present, the man ae the art is able to choose the most suitable method of separation.

Still in the context of this first embodiment, the process according to the present invention further provides for the superacid and optionally the residual propionyl fluoride to be recovered during step (e). When the process is carried out batchwise, the suDeraciae, alone or as a mixture with hydrogen fluoride and optionally a part of the propionyl fluoride which has not been separated, is recovered to be reused for the next reaction. When the process is carried out continuously, the superacid, optionally mixed with hydrogen fluoride and / or propionyl fluoride, is recycled to the reactor. When hydrogen fluoride has been added during step (c), recycling can be carried out after partial removal of hydrogen fluoride. In this case, a particular embodiment consists in adjusting, by virtue of step (f), the quantity of hydrogen fluoride to the constitution of the superacid used in step (a). The fluoride ("the hydrogen eliminated at this stage can in turn be recycled, for example to the intervention point of stage (c) where it will at least partially allow it to constitute the make-up necessary for the displacement of the chemical balance. aforementioned.

The reaction of the process according to the present invention can be com-.

moderately performed under atmospheric pressure. For reasons of kinetics and economy of industrial operation, it may also be advantageous to proceed under a pressure greater than atmospheric pressure, for example under a pressure of up to 250 bars. Those skilled in the art are able to choose, as a function of the pressure level, on the one hand the residence time in the reaction medium in the reactor and on the other hand the appropriate temperature. The residence time in the reactor is generally between 0.1 and 300 minutes. In addition, in the case where the reaction pressure is appreciably higher than atmospheric pressure, it may be advisable to lower the pressure at the end of the process. step (c) and recompress the fluids recovered in particular during step (e) and, where appropriate, during step (f) to the pressure of the reactor.

The process according to the invention makes it possible to obtain with satisfactory kinetics and yield, after at least one purification step known to those skilled in the art such as fractional distillation, propionyl fluoride having a degree of purity suitable for subsequent use. In fact, propionyl fluoride constitutes an important intermediate ae synthesis which will allow in particular the production of propionic acid by hydrolysis. In accordance with the objectives of the present invention, this compound is obtained at a moderate cost due to the choice of propane as the starting raw material.

The sole object of the examples below is to illustrate the present invention, without limiting its scope in any way.

EXAMPLES 1 to 4)
In a polymonochlorotrifluoroethylene reactor with a volume of 0.1 liter, are introduced at 20oC, with stirring and under a nitrogen atmosphere, with antimony pentafluoride and hydrogen fluoride in the HF / SoF5 molar ratio equal to 4. This mixture is then transferred to a stainless steel autoclave reactor of 0.3 liter volume. The temperature T of the mixture (expressed in degrees Celsius) is then brought to the value indicated in the table then the mixture of propane and carbon monoxide in the CO / C3Ha molar ratio indicated in the table is introduced by a turbine until reach the pressure P mentioned in the table (expressed in bars).

Two operating regimes can then be applied, namely - a "static" regime (noted s): in this case all the reagents are
introduced at the start and the pressure indicated in the table is the pres
initial pressure, or else - an "aynamic" regime (noted d): in this case the addition of propane and
carbon monoxide continues throughout the reaction with a time of
contact of the gas with the liquid phase for about 9 seconds, the pressure in
indicated in the table being constant during the test.

In each case the duration of the test is 1 hour. At the end of the test ("static" mode) or during the test ("dynamic" mode), the gas phase is expanded to a temperature not not exceeding 25 "C and analyzed online in a series of chromatographs to identify and measure - on the one hand propane and unreacted carbon monoxide, on the one hand,
to calculate the TC conversion rate (expressed in tó and indicated in
table below), equal to the number of moles of propane consumed on the
number ae moles ae propane introduced.

- on the other hand the gaseous side products resulting from the reaction, consisting of
generally killing a mixture of hydrogen, methane and ethane including the Dro-
molar portions in said mixture are those indicated in the table below
after.

Furthermore, the liquid phase contained in the reactor is subjected to total hydrolysis at 0 ° C., then the aqueous solution obtained is analyzed by gas chromatography so as to identify and assay the organic compounds formed by hydrolysis of the reaction products.

These generally constitute a mixture of isobutyric acid (AIB), propionic acid (AP) and ae various compounds (generally denoted "Others" in the table below), these comprising in particular acetic acid, n-butyric acid, methanol and acetone. The molar proportions of AIB and AP acids in the mixture are shown in the table below. BOARD

Example <SEP> TC <SEP> P <SEP> CO / C3H8 <SEP> TC <SEP> AIB <SEP> AP <SEP> Others <SEP> CH4 <SEP> C2H6 <SEP> H2
<tb> 1 <SEP> - <SEP> 6 <SEP> 55s <SEP> 9.5 <SEP> 33 <SEP> 18 <SEP> 76 <SEP> 6 <SEP> 87 <SEP> 10 <SEP> 3
<tb> 2 <SEP> -10 <SEP> 6d <SEP> 20.0 <SEP> 20 <SEP> 5 <SEP> 76 <SEP> 19 <SEP> 93 <SEP> 7 <SEP> 0
<tb> 3 <SEP> +30 <SEP> 62s <SEP> 16.0 <SEP> 94 <SEP> 12 <SEP> 79 <SEP> 9 <SEP> 89 <SEP> 7 <SEP> 4
<tb> 4 <SEP> -10 <SEP> 6d <SEP> 3.3 <SEP> 10 <SEP> 23 <SEP> 66 <SEP> 11 <SEP> 79 <SEP> 21 <SEP> 0
<tb>

Claims (11)

1. Catalytic process for the manufacture of dropionyl fluoride from carbon monoxide, hydrogen fluoride and a stream of aliphatic hydrocarbons comprising mainly propane, characterized by the succession of the following steps (a) introduction of 'at least one fluid chosen from carbon monoxide and said stream of hydrocarbons in a reactor in the presence of a superacid consisting of hydrogen fluoride and antimony pentafluoride SDFs, (b) where applicable, if it has not already been introduced during step (a), introduction into the reactor of a fluid chosen from monoxide carbon and said hydrocarbon stream, under conditions specific to allow the formation, mainly, of a complex consisting of propionyl cation and SDF6 anion, (c) conversion of said complex to propionyl fluoride, (d) separation of propionyl fluoride, and (e) recovery with superacid. 2. Method according to claim 1, characterized in that the CO / C3H8 molar ratio in the reactor is at least equal to 1.5. 3. Method according to one of claims 1 and 2, characterized in that the HF / SoF5 molar ratio in the reactor is between 1 and 30. 4. Method according to one of claims 1 to 3, characterized in that the reaction temperature is between -80 C and + 600C. 5. Method according to one of claims 1 to 4, characterized in that the complex formed at the end of step (o) is converted into propionyl fluoride during step (c) by the intervention of at least one means oour shifting the equilibrium between said complex and the propionyl fluoride towards the formation of the latter. 6. Method according to claim 5, characterized in that the intervention means of step (c) is the addition of a chemical species capable of significantly reducing the acidity of the reaction medium. 7. Method according to claim 6, characterized in that said chemical species is hydrogen fluoride. 8. Method according to one of claims 1 to 7, characterized in that the superacid recovered during step (e) is recycled to the reactor. 9. Method according to claims 7 and 8, characterized in that the recycling of the superacid is carried out after partial removal of hydrogen fluoride. 10. The method of claim 9, characterized in that the hydrogen fluoride removed at this stage is recycled to the intervention point of step (c). 11. Method according to one of claims 9 and 10, characterized in that it further comprises a step (f) of adjusting the amount of hydrogen fluoride to the constitution of the superacid used in 1 step. (at).