Field of Invention:
The invention relates to a process for preparation of trifluoroacetyi chloride by reacting trifluoroacetyl fluoride and a chlorinated acid chloride, capable of getting fluorinated by mixing these reactants in a reactor and isolating the wanted Trifluoroacetyl chloride.
Background of Invention:
US 2257868 describes a process for synthesis of trifluoroacetyl chloride by the reaction of trifluoroacetic acid and benzoyl chloride. The process requires trifluoroacetic acid which could be manufactured by electro fluorination of acetic acid or acetic anhydride containing anhydrous hydrofluoric acid. Alternatively, the trifluoroacetic acid could be prepared by the catalytic fluorination of trichloroacetyl chloride using anhydrous hydrogen fluoride. It is also known that the trifluoroacetyl fluoride is prepared from trifiuorodichloroethane and hexafluorodichloro butene with molecular oxygen in presence of UV light. Although these kind of process are known, it is uneconomical to implement them on a commercial scale and starting compounds are not that freely available.
Of the all the above processes for trifluoroacetic acid, the catalytic process of fluorinating trichloroacetyl chloride is considered best for the reason that the starting material trichloroacetyl chloride is a cheap, easily available chemical and is used commercially for making agrochemical product.
US 3829483 addresses the above problem of the process by reacting trifluoroacetyl fluoride with another chlorinated hydrocarbon, capable of getting fluorinated, by passing the mixture over chromium oxyfluoride catalyst at a temperature range of 100- 350
degree C. The resultant trifluoroacetyl chloride is isolated from the mixture by
distillation.
Various chlorinated organics suggested in he process are hydrocarbons of 1-3 carbon
atom out of which alteast 2 carbon atoms are hooked up to same carbon atom. The
hydrocarbons cited are carbon tetrachloride, chloroform, monofluorotrichloro methane &
monochlorodifluoro methane.
In doing such reaction, if one looks into today's context, the carbon tetrachloride would
result in the formation of monofluorotrichloro methane or dichlorodifluoro methane.
Both these compounds are ozone depletors and cannot be used as a process on a
commercial level.
Similarly the use of monofluorotrichloro methane as a chlorinating agent would result in
the formation of dichlorodifluoro methane (R-12) whose boiling point is similar to that of
trichloroacetyl chloride causing problem in isolation of trifluoroacetyl chloride.
However the process for the manufacturing of trifluoroacetyl chloride in the prior art has
following disadvantages.
1. The fluorination of trichloroacetyl chloride results in formation trifluoroacetyl fluoride which forms an azeotrope with the hydrogen chloride formed as a by product. Separation of pure trifluoroacetyl fluoride from such a mixture is difficult.
2. Further in catalytic fluorination of perchloro compound, a large excess of hydrogen fluoride is needed for completion of the reaction. Separation of this excess hydrogen fluoride from trifluoroacetyl fluoride is difficult.
3. Separation of trifluoroacetyl fluoride from hydrogen chloride and hydrogen fluoride needs either very high pressure distillation or low temperature refrigerant thereby adding further cost to the overall process.
The present invention obviates the drawbacks of prior art.
The objective of the present invention is to provide a process comprising of reacting
trifluoroacetyl fluoride with chlorinated acetyl chloride capable of getting fluorinated
with high yield.
Another objective of the present invention is to provide an environmental friendly
process in which unreacted trichloroacetyl chloride and trifluroacetyl fluoride is recycled
back to the fluorination reactor generating no waste or by-product.
STATEMENT OF INVENTION:
The reaction relates to a process for preparation of trifluroacetyl chloride comprising reacting trifluoroacetyl fluoride with a chlorinatedacetyl chloride.
SUMMARY OF INVENTION:
The present invention discloses a process for preparation of trifluoroacetyl chloride by reacting chlorinatedacetyl chloride with trifluoroacetyl fluoride. The reaction can be carried out in liquid or vapour phase in presence or absence of the catalyst.
In a preferred embodiment the unreacted chlorinatedacetyl chloride and trifluoroacetyl fluoride is recycled back to the reactor. Recycling does not yield waste and therefore the process is environmental friendly.
In an embodiment trichloroacetyl chloride is contacted with excess of HF in presence of a catalyst in a reactor, resulting into trifluoroacetyl fluoride. Excess moles of HF might be present along with trifluoroacetyl fluoride. The trifluoroacetyl fluoride alongwith HF can be recycled back into the reactor to react with trichloroacetyl chloride to form trifluoroacetyl chloride and HCl.
DETAILED DESCRIPTION:
The reaction of trifluoroacetyl fluoride with chlorinated acetyl chloride can be carried out either in the liquid phase or in vapor phase.
Various acetyl chlorides that can be used in the process of current invention are monochloroacetyl chloride, dichloroacetyl chloride and trichloroacetyl chloride, preferably trichloroacetyl chloride.
In vapor phase, the reaction is performed at a temperature ranging from 110- 350 degree C. The reaction can proceed in presence or absence of a catalyst in the range of 0.5 to 5% by weight of the reactants. Various catalysts which can be used for the process include chromium oxyfluoride, chromium- aluminum oxyfluoride, chromium-aluminum with zinc. The reaction can be done either at atmospheric pressure or at higher pressure. The reaction can be performed in a pressure range of 1-30 kg/cm2, preferably 1-20 kg/cm2 High pressure facilitates easy and economical separation of down stream products.
The molar ratio of trifluoroacetyl fluoride to chlorinated acetyl chloride can be varied from 1:1 to 1:20. The molar excess of chlorinated acetyl chloride is seen as advantageous to the process in terms of higher conversion of trifluoroacetyl fluoride.
In an embodiment of the invention, the reaction can also proceed in the following manner:
Trichloroacetyl chloride is contacted with excess of HF in a reactor in presence of a fluorination catalyst of the kind of coprecipitated chromia-alumina impregnated with zinc salt, resulting into trifluoroacetyl fluoride. Excess moles of HF will be present along with trifluoroacetyl fluoride. The trifluoroacetyl fluoride alongwith HF can be recycled back into the reactor to react with trichloroacetyl chloride to form trifluoroacetyl chloride and HC1. It is not essential to eliminate HF and HC1 from the reactor. However, it is preferred that HF and HC1 are removed from the reactor to avoid formation of side products. Alternatively, the crude reaction mixture from the fluorination reactor can be mixed with chlorinated acetyl chloride in a manner which is known in the art. The gaseous mixture obtained can then be passed over the catalyst bed for converting the trifluoroacetyl fluoride to trifluoroacetyl chloride.
In liquid phase the reaction can be carried in the absence of catalyst or the reaction may be carried in presence of catalyst such as Lewis acid of the kind of FeCl3, SbCl5, A1C13, etc in the range of 0.5 to 5% of the reactants. The reaction is carried at a temperature range of 100-220 degree C more preferably in a region of 175-200 degree C. The molar ratio of trifluoroacetyl fluoride to chlorinated acetyl chloride is 1:1 to 1:20. Higher molar ratio of trifluoroacetyl fluoride to chlorinated acetyl chloride can be used for the process but the size of the reactor and down stream equipment makes the process uneconomical. The preferred molar ratio of trifluoroacetyl fluoride to chlorinated acetyl chloride is 1:3 to 1:12, more preferred molar ratio of trifluoroacetyl fluoride to chlorinated acetyl chloride is 1:3 to 1:6.
The pressure of the reaction is autogenous and goes as high as 30 Kg/cm . As the reaction
proceeds there is seen a drop in pressure.
The reaction of liquid phase is done in pressure reactor capable of handling upto 50
kg/cm . Lewis acid catalyst along with trichloroacetyl chloride is introduced into the Parr
reactor through the liquid line and then trifluoroacetyl fluoride is introduced into the
pressure reactor from the sample cylinder. The temperature of the reactor is raised slowly
and is allowed to reach the reaction temperature of 170-200 degree C.
The progress of the reaction is monitored by drawing the sample from the liquid phase as
well as gas phase of the reactor and carrying the chromatographic analysis of the sample.
Once the desired level of conversion is achieved, the pure trifluoroacetyl chloride is
separated by fractionation of the reactor material.
The unreacted trichloroacetyl chloride along with trichloroacetyl fluoride can optionally be recycled back to the reactor. The unreacted trichloroacetyl chloride along with trichloroacetyl fluoride is distilled and recycled back to the reactor. This limits the amount of waste and makes the process environment friendly.
Having described the basic concept of the invention, references are now made to the following examples, which are provided by the way of illustration and not of limitation, of the practice of the invention in the preparation of the trifluoroacetyl chloride.
Example 1
In a pressure reactor of 2-liter capacity made of Hastalloy-C, 1010 gms of commercially
available trichloroacetyl chloride was introduced through the liquid line of the reactor.
Subsequently, trifluoroacetyl fluoride was introduced from the pressure cylinder into the
Parr reactor slowly to a extend of 120 grams. The reactor pressure at the ambient temp
was seen at 9-10 Kg/cm2. The temperature of the reactor was raised slowly to 200 degree
C where the autogenous pressure of the reactor goes up to 33 Kg/cm2. The reaction mass
was stirrer for a period of 5 hrs after which the reactor mass was analyzed by gas
chromatography to find a composition of 66.7% of trifluroacetyl chloride and 26.64%
of trifluoroacetyl fluoride content with small amount of trichloroacetyl fluoride.
The reaction mass was subjected to distillation and the unreacted trichloroacetyl chloride
along with trichloroacetyl fluoride was recycled back to the fluorination reactor.
The amount of trifluroacetyl chloride recovered is from the reactor is 94.54 grams
corresponding to a yield of 93.69 %
Example- 2
Experiment was carried out in a similar fashion as described in example -1 with trifluoroacetyl fluoride of 120 grams and trichloroacetyl chloride of 510 grams. The reaction mass was allowed to come in contact for a period of 3 hrs. Samples were drawn and the composition of the reactor mass was seen at 57.3 % of trifluroacetyl chloride and 36.63 % of trifluoroacetyl fluoride. The reaction mass on distillation yielded 89.5 grams of trifluroacetyl chloride, amounting to a yield of 82.2 %.
Example -3
Reaction was carried in a similar apparatus as described in example -1 with 110 grams of
trifluoroacetyl fluoride and 1010 grams of trichloroacetyl chloride. A Lewis acid catalyst
(FeCl3) of 4 % with respect to the reactant was incorporated for the reaction. The
reaction was run for a period of 10 hrs. The reaction mass at the end of the reaction
showed a composition of trifluoroacetyl chloride 67.99 % and trifluoroacetyl fluoride
28.457%.
Trifluoroacetyl chloride so obtained was distilled to give 76.42 grams of trifluoroacetyl
chloride amounting to a yield of 73 %.
Example-4
Reaction was carried with higher molar ratio of trichloroacetyl chloride to trifluoroacetyl fluoride. An amount of 133O grams of trichloroacetyl chloride was reacted with 67 grams of trifluoroacetyl fluoride for a period of 6 hrs at a temperature of 200 degree C. At the end of the reaction, the composition of the mass showed trifluoroacetyl chloride 73.145 % and trifluoroacetyl fluoride 24.038 %. The reaction mass was distilled to give trifluoroacetyl chloride of 54.03 grams amounting to a yield of 90.88 %
Example -5
A 1.5 foot inconel reactor of 1" was filled with 300 grams of fluorinated chromia
catalyst. Trichloroacetyl chloride at rate of 1.7 gms / mt and trifluoroacetyl fluoride at
rate of 1.7 gms / mts for a period of 1 hr were fed into the reactor.
The effluent form the reactor was analyzed by gas chromatography and the composition
was found at trifluoroacetyl chloride 33.95 % and trifluoroacetyl fluoride 54.07 %. Based
on the quantity of trifluoroacetyl chloride collected, the yield of the process works out to
82.3 %.

We Claim:
1. A process for preparation of trifluroacetyl chloride comprising reacting
trifluoroacetyl fluoride with a chlorinatedacetyl chloride.
2. A process as claimed in claim 1, wherein chlorinated acetyl chloride is selected
from a group of monochloroacetyl chloride, dichloroacetyl chloride and
trichloroacetyl chloride, preferably trichloroacetyl chloride.
3. A process as claimed in claim 1 or 2, wherein the molar ratio of trifluoroacetyl
fluoride to chlorinatedacetyl chloride is 1:1 to 1:20.
4. A process as claimed in any of the preceding claim, wherein the molar ratio of
trifluoroacetyl fluoride to chlorinatedacetyl chloride is 1:3 to 1:12, more
preferably 1:3 to 1:6.
5. A process as claimed in any of the preceding claims, wherein the reaction is
performed in a reactor at a pressure ranging from 1 to 20 kg/cm2.
6. A process as claimed in any of the preceding claim, wherein reaction is carried
out in liquid phase in presence of a lewis acid catalyst selected from a group
consisting of FeCl3, SbCl5, A1C13
7. A process as claimed in any of the preceding claim, wherein reaction is carried
out in vapour phase in presence of a catalyst in presence of a catalyst selected
from a group consisting of chromium oxyfluoride, chromium-aluminum
oxyfluoride, and chromium-aluminum with zinc.
8. A process as claimed in any of the preceding claim, wherein the catalyst is
present in the range of 0.5 to 5% of the reactants.
9. A process as claimed in any of the preceding claim, wherein unreacted
trichloroacetyl chloride along with trichloroacetyl fluoride is recycled back to the
reactor.
10. A process as claimed in any of the preceding claim, wherein trifluroacetyl
fluoride is obtained by fluorination of trichloroacetyl chloride with HF in
presence of a fluorination catalyst.
11. A process for preparation of trifluroacetyl chloride substantially as hereinbefore
described with reference to the foregoing examples.