DE2221844C3 - Process for the perfluorination of perchlorinated carbonyl compounds - Google Patents

Description

22 2Ί5844

3 4

• The efficiency of this procedure is retained. The aim is also to keep the decomposition -Hch weak: in this way at 300 to the organic compound used as a result of ¹³ VfC : with a throughput of 310 g HF and side reactions to less than 5 mol percent, all- **! To limit thexachloroacetone per hour and per kg of catalyst to less than 3 mol percent.

Edited, the mean conversion is 5 Finally, the desired perfluorinated compound should

* ^tOr prad when the reactants pass through in a single pass of the reaction

^ MMh 45 ° / and the product contains 89.4% hexa-partners due to the fluorination zone with a pro-

WP ¹ ^ ₁ ^ corresponding to a production of 53 g productivity of more than 100 g per hour and per kg

α "fluoroacetone per hour and per kg of catalyst. Catalyst can be obtained.

If one examines the efficiency of the system io The tasks set are described in the

h to actually increase further temperature increase, inventively characterized in the preceding claims

wc _{results very} bad because the method according to the invention was solved. This is the one

f t of hexafluoroacetone to 20% falls as a result of the finding that the perfluorine ring is a

When the compounds are split in a perchlorinated compound, a series of successive

• comprises «door 380 to 450 ⁰ C, at a flow rate 15 following reactions according to the following Temperaiu" _{hexachloroacetone e} j hour and per kg scheme, each of the illustrated Reakv remains ^0I tal sator Ds ** Yield of Hexafluoracetou functions a fluorination means .

«Ring through and as a result of the loss of the product

Decomposition is not feasible this way R _ CCl ₃ + HF ^ HCl + R - CCl ₁ F

Analogous observations can be made with the Fluone- * ο _R _ _caFj

_Λ «Make trichloroacetyl chloride: at tempe- ^Λ ^ * ^

^W r "U voISo up to? 25 ° C only 62.5 mol- R = remainder with carbonyl group.

♦ »im>« mixture of trifluoroacetyl fluoride and.

CÄdfluoScetylfluorid received, which before In the course of the reaction contains the Reakt.ons-

1, T this latter compound contains, which however * ₅ mixture as a result is a mixture of percWor-

* · M is the desired perfluorinated compound. fluorinated intermediates, which is produced by the

^ω ΐ _η another known method for fluorinating average ratio of fluorine atoms to chlorine atoms

Haloeen carbonyl compounds with each organic molecule in the mixture identified

I ⁰ U- α carbon atoms in the molecule works can be drawn. .

\ l \ m TeSatuäbereich from 150 to 400 ⁰ C in 30 compounds, which according to the nomination perfluone t

^g ^ t bSimmter chromium oxyfluoride contacts are e.g. Trichloracetylchlond Hexachlor-

14 43 83 ^ Also in this process acetone, octachlorobutanone, trichloroacetaldehyde and

: or in 7 5 hours only 72 to 74 mol pentachloropropionyl chloride.

L ^ S from trichloroacetyl chloride It is important and represents a feature of the fictional

of hexafluoroacetone and 35 according to the method that the first two ^ Pe -

i Ä ^ r: zT: r rsxsss ää

Connections ^ a, ge ^ nen * , rich

SsSSSSSüi

3 ESSI ^ SSS

It is expressed as the ratio of the number of moles of HM ^l ™ _h ™ £ _included perchlorinated causes of the reaction ^ f ^^} ^^^ bSung S unfunctional groups. It depends on weker-MoIe HF, which theoretically fa the Ρ «3» ° ™ ^ ~ ^Γ ₆ J ^ _from ⁸ _other reaction conditions such as combined organic compounding requirements are 65 mn ^ o reaction zone, molar ratio of

The outflowing vaporous water hydrofluoric acid to the used per-ST ⁿ ° ^en ^ SSÜ ^ SSi ^ connection- chlorinated compound and catalyst activity.

This choice of temperatures in each zone is essential in order to achieve the desired high temperature in particular To achieve the efficiency of the process.

The Applicant has found that the temperature established for the second zone is the most critical S because the compounds present in this zone tend to decompose and also show a significantly lower rate of fluorination than the compounds which are fed into the first zone. The choice of this temperature must therefore be made sensibly; it represents a compromise between siner relatively low temperature, such as 25O ⁰ C in softer the thermal decomposition is prevented, and a higher temperature such as 275 ° C, wherein the Fluorierungsgeschwindigkeit is increased. The following examples describe in detail how this compromise can be implemented in individual cases.

In the first zone, due to the relatively high rate of fluorination of the compounds used, the temperature can be limited to 220 to 250 ° C. In the third zone, however, the complete or total perfluorination in a single pass of the reactants along the catalyst requires a significantly higher temperature, which can also vary greatly depending on the nature of the desired perfluorinated compound. In this third zone, however, the risk dT is thermal decomposition of the present there compounds are very low, and the temperature can therefore be set 275 to 35O ⁰ C to above without the final yield of aspired perfluorinated compound by side reactions is remarkably limited.

Will be the temperature of the three consecutive Reaction zones set in the manner indicated, the residence time of the reactants in each individual zone can be set to values from 2 to 10 seconds: this dwell time is determined for the gaseous reactants under the prevailing temperature and pressure conditions and with respect to the total volume of each zone without taking into account the volume occupied by the catalyst. The maximum performance is thereby achieved that the temperature practically prevailing in each zone is controlled so that the rate of consumption of hydrofluoric acid in each Zone is practically of the same order of magnitude. This has the consequence that the residence time of the reactants in each of the three zones depends on the amount Hydrofluoric acid, which is supposed to react there. This condition is put into practice in a very simple way realized: For example, if the reactor has the same cross-section over its entire length has, the length of each zone is adjusted so that it corresponds substantially to the amount of hydrofluoric acid which is to react there. Indeed it runs the reaction practically without changing the number of moles, because the side reactions of the decomposition on one Minimum are reduced, the fluorination proceeds with a constant number of moles. Will therefore be on In this way, given lengths to each reaction zone, the corresponding residence times are given roughly proportional to the amount of hydrofluoric acid that is supposed to react there. Furthermore can be taken into account that for a given feed into each zone the actual residence times also depend on that prevailing in each zone Temperature fluctuates, especially when the extreme temperatures are significantly different.

However, such a procedure is not of critical importance for the present method. On the contrary, it may be necessary to lengthen the residence time in one of the three zones, especially in the third zone in order to achieve better yields of the desired perfluorinated compound.

Determining the residence time in each zone for maximum efficiency or For a better understanding, productivity should be based on the example of the fluorination of hexachloroacetone explained.

In the first zone, the partial fluorination of hexachloroacetone is carried out at a temperature of 236 ° C. until a mixture of perchlorofluorinated compounds is obtained which contains on average 2.6 fluorine atoms per organic molecule: The first two steps are carried out completely, and the mixture of intermediate compounds exiting the first zone has an average composition of the formula C ₃ OCl ₃₄ FIG.

In the second zone, the fluorination of the organic compounds is continued at 265 ° C. until a mixture of perchlorofluorinated compounds is obtained which contains an average of 4.4 fluorine atoms per organic molecule, which is a mixture of intermediate compounds of the general formula C ₃ OCl ₁₈ F _4-4 corresponds, in which the ratio of the number of fluorine atoms to the number of chlorine atoms is equal to 2.75, ie is greater than 1.5. 1.6 moles of HF per mole of organic compound must then be converted in order to achieve complete perfluorination; this takes place in a third zone at 310 ° C. The residence time in the three successive zones is 6 seconds, 4.1 seconds and 3 _S 5 seconds; the dimensions of each zone can be calculated from this, taking into account the temperatures and the total throughput. The average reaction rate in the three zones is about 0.38 moles of HF per second and per mole of hexachloroacetone.

Of course, the temperatures and dwell times in the three zones must be established experimentally and specially determined for each individual case will.

For the process according to the invention it is absolutely necessary that the first two fluorination steps take place completely in the first zone. As a result, the number of moles of hydrofluoric acid is soft in the two subsequent zones should respond, smaller than n-2, where π is the number Mole HF, which is the perfluorination of the starting compound used and, for example, for Trichloroacetyl chloride 4, for pentachloropropionyl chloride and hexachloroacetone 6 and for perchlorobutanone 8 amounts to. These differences, given by the starting compound used, require a special one Study of the operating conditions in each individual case. So becomes the lower limit of the ratio of Number of fluorine atoms to number of chlorine atoms, which according to the invention when leaving the second zone should be reached, preferably set to or above 3 in the case of trichloroacetyl chloride and trichloroacetaldehyde and to 2 in the case of hexachloroacetone. This limit value should be used for octachlorobutanone be at least 1.5 and reach the characteristic value defining the invention.

The efficiency of the procedure is determined by the

Influenced pressure under which the reactants are in the three reaction zones. The reaction rate increases noticeably at an absolute pressure in the range from 1 to 2.5 bar and increases slightly in the range from 2.5 to 4 bar if a good catalyst is used. Above 4 bar, a further gain in terms of performance is very limited or equal to zero, because the technological difficulties then determine the weight of the axial thermocouple in a housing. The reactor had twelve side exits, each 8 cm apart; the first exit was 30 cm from the entrance to the reactor. These side exits are normally closed, but can be opened to analyze the composition of the reaction mixture at various points in the reactor.
The fluorination catalyst was prepared in

fall; therefore, although in some cases the reaction can lead to a precipitated chromium

tion was treated by hydroxide gel with anhydrous HF under an absolute pressure above 4 bar.

be performed, for example with trichloroacetyl After fluorination and agglomeration to one

chloride, which is sufficiently volatile; However, it is granules with a grain size of about 5 mm

neither interesting nor economical, this value too specific surface area of this catalyst 186 m ² / g.

exceed. The application of an absolute pressure 15 The reactor was held vertically and so loaded

above 1 bar is particularly advantageous because here the Side reactions of the decomposition remain very limited, while the rate of fluorination increases with the Pressure increases noticeably up to 2.5 bar. The pressure thus improves the performance of the process and at the same time increases the yield of the desired product. In addition, it is useful that in some If the flue gas from the fluorination reactor is under pressure: this facilitates the separation of the reaction products. As a result, the method according to the invention is preferably used in a

sends that one received consecutively from bottom to top:

g absolute pressure of 1.2 to 2.5 bar carried out.

The efficiency of the process also depends on the feed ratio of the reactants anhydrous hydrofluoric acid and perchlorinated functional compound. It has to be at least an amount of anhydrous hydrofluoric acid can be used to cover all of the perfluorination the perchlorinated compound enables. Therefore ß d

g g

the molar ratio when feeding HF must be 35, hli

A 7 cm high layer of spheres made of flaky aluminum oxide (not vulnerable to HF);
a 33.5 cm high catalyst layer (third catalyst zone);

a 7.0 cm high layer of flaky alumina;

a 36.5 cm high catalyst layer (second catalyst zone);

a 7.0 cm high layer of leafy alumina;

a 50.0 cm high catalyst layer (first catalyst zone);

a 6.0 cm high layer of flaky aluminum oxide.

A total of 1.21 or 0.84 kg of catalyst was made

perchlorinated compound be equal to or above the previously defined number η, d. H. for trichloroacetyl 4, 6 for pentachloropropionyl and hexachloroacetone and 8 for octachlorobutanone. An excess of HF, based on the stoichiometric ratio, is useful because it significantly increases the rate of fluorination is increased, especially in the last two stages, the total perfluorination of the lead drawn connection. Preferably will

therefore the method according to the invention with a 45 attached heating element is heated so that the Tem excess of HF of at least 20 mole percent, the temperature therein was substantially uniform. the based on the stoichiometric ratio.

However, an excessively high HF excess is undesirable,
because the gain in fluorination rate is 50
is compensated by a loss of performance due to the strong dilution of the organic compounds in the reaction volume. As a result, it is preferred to use an excess of HF
from 20 to 80 mol percent, based on the stoichiometric 55 1.3 bar fixed. The temperatures in the three Katalymetrische ratio for the Perfluorierungsreaktion, sator zones were set at 236, 265 and 310 ⁰ C regulated The residence time in each of the three zones was 6 seconds, 4.1 seconds, and 3.5 seconds.

The analysis of the gas mixture emerging from the first catalyst zone showed that the average was organic Molecule 2.6 fluorine atoms were bonded and that the first two steps of fluorination were complete were carried out. The analysis of the gas mixture emerging from the second catalyst zone Other independent electrical heating elements showed that an average of 4.4 fluorine-heated elements per organic molecule Stainless steel tube with inner diametres bound and that the middle joint 3.56 cm and length 1.5 m are used. The composition of the organic compounds has a heat gradient of the reactor was made with the help of a ratio of the number of F-atoms to the number of Cl-atoms

The reactants, anhydrous HF with a degree of purity 99.7% and hexachloroacetone with a degree of purity of 99.5% were fed in at the top of the reactor and went through one after the other:

The 6.0 cm high layer of flaky aluminum oxide in which the reactants are mixed and preheated and the three catalyst layers separated by two aluminum oxide layers.

Each catalyst layer was made with one of the outside

The temperature of the gases increased in the intermediate layers of flaky aluminum oxide.

The feed of the reactants was adjusted to 0.94 mol / h hexachloroacetone and 8.4 mol / h HF anhydrous, corresponding to an excess of anhydrous HF of 48.8%, based on the stoichiometric Crowd. The pressure in the reactor was increased

worked

The invention is explained in more detail with reference to the following examples.

example 1

As a reactor, an externally

= 2.75 corresponded. That from the third catalyst zone escaping gas mixture was composed as follows:

si) Organic part

Hexafluoroacetone 96.8 mole percent

Pentafiuormonochloraceton .. 1.2 mole percent

Tetrafluorodichloroacetone 0.1 mole percent

Perchlorethylene traces

(<0.01 mole percent)

Tetrafluorodichloroethane 0.2 mole percent

Trifluorotrichloroethane 1.2 mole percent

Difluorotetrachloroethane 0.3 mole percent

various (mainly C ₁ ) 0.2 mole percent

b) Inorganic part

HF
HCl

33.7%
66.3%

10

The outflowing gas also contained a small amount of CO, which originated from the decomposition of ketone compounds with the formation of C ₂ compounds.

The total degree of fluorination, based on HF, namely moles HF consumed / moles HF theoretically required was 98.7%.

The target perfluorinated compound content of the organic part was 96.8%.

ίο The degree of decomposition of the organic compounds due to side reactions was only 1.9%.

The hexafluoroacetone output was 0.91 mol / h, corresponding to 151 g / h. The output was 180 g each Hour and per kg of catalyst.

For comparison, various tests were carried out, with either all three catalyst zones adjusted to the same temperature or two of three catalyst zones to the same temperature became; all other conditions were the same

as in example 1.

Comparative experiments
away

example 1

Temperature of the 1st zone, ⁰ C 236 265 310 236 236 265 236 2nd zone temperature, ° C 236 265 310 236 310 265 265 3rd zone temperature, "C 236 265 310 310 310 310 310 Total degree of fluorination,
based on HF,% 51.7 88.2 94.7 79.2 92.2 91.8 98.7 Hexafluoroacetone
in exhaust gas,% 1.5 52 85.3 27 76.4 70.9 96.8 Degree of decomposition,% 1.5 6.2 14.3 5.3 8.7 6.4 1.9 Productivity,
g / h / kg catalyst 3 96 157 50 141 130 180

The comparison clearly shows the advantages of the method according to the invention.

Experiment a shows that the degree of fluorination is low and low in the entire reactor at low temperatures the formation of perfluorinated product is negligible.

At an average temperature in the entire reactor (experiment b), the inlet temperature has the effect that the hexachloroacetone fed in is cracked to a considerable extent, which leads to a 6.2% loss of reactants. A comparison of experiments b and f shows that the cracking increases only slightly when the third catalyst zone is ^{brought to 31O 0} C; this is explained by the fact that the compounds that are already strongly fluorinated are not very sensitive to cracking.

At a high temperature in the entire reactor (experiment c), a good productivity or yield of hexafluoroacetone is achieved, but cracking increases particularly in the first and second catalyst cores, corresponding to a loss of 14.3% of the reactants. The organic exhaust gas contains only 85.3% hexafluoroacetone, which is essentially in the form of a mixture with C ₂ -chlorofluorocarbons and is difficult to separate and purify, which increases the production costs accordingly. From an economic point of view, the loss affects both the yield of perfluorinated product and the cleaning costs for this product. Tests d, e and f show the importance of the measure according to the invention of inserting a second zone of medium temperature between the first and third zones. In this ver

In similar experiments, the degree of decomposition as a result of cracking is higher and the productivity or yield is higher less than is achieved according to the invention. In addition, the exhaust gas from the reactor contains a mixture from perchlorofluorinated ketones and chlorofluoro-

hydrocarbons with 2 carbon atoms, which are difficult to separate.

Test d in particular shows that in the absence of a second zone with a temperature of 265.degree m the third zone is a crack-sensitive reaction

mixed entry. In fact, the degree of fluorination in this version is at the exit from the second zone of the organic compound about 3, and the mean composition of the organic compounds corresponds to a ratio of number

F-atoms / number of Cl-atoms of about 1, as c below the lower limit defined according to the invention of 1.5 and significantly lower than the preferred « Limit of 2 in the case of hexachloroacetone. In this case, it was found that the degree of decomposition κ

of the third zone at 31O ⁰ C increases sharply. Diesel degree of decomposition actually increases from 1.3% when exiting the second zone to 5.3% when exiting the third, zone. This experiment shows somi

the importance of the second zone provided according to the invention, with the aid of which at the same time the performance of the process and the degree of decomposition as a result of cracking of the organic compounds can be reduced.

In a further comparative experiment with Example 1, the residence time of the reactants became arbitrary so reduced that the first two fluorination steps do not all take place in the first zone took place. To do this, the reactor was filled as follows:

A 7.0 cm high layer of spheres of flaky alumina or alumina hydrate, a
25 cm high catalyst layer (third catalyst zone), a 7.0 cm high layer of flaky aluminum oxide, a 61.5 cm high catalyst layer (second catalyst layer), a 7.0 cm high layer of flaky aluminum oxide, a 33.5 cm high catalyst layer (first catalyst zone), a 6.0 cm high layer of flaky alumina.

The same catalyst was applied as in Example 1 (1.2 1, 0.84 kg) and the experiment under the the same conditions with regard to the infeed carried out.

The outside heating elements were modified so that uniform temperatures in each of the three new catalyst zones were obtained, and these zones were corresponding to the same Temperatures as in Example 1 brought.

The absolute pressure was kept at 1.3 bar.

The residence time in the individual zones was:

1st zone 3.0 seconds,

2nd zone 7.0 seconds,

3rd zone 3.5 seconds.

When leaving the first zone, a mixture was obtained consisting essentially of perchlorofluorinated compounds Compounds which on average only contain 1.8 fluorine atoms per organic molecule. the The composition of the organic part of the reaction mixture was:

Mole percent

Hexachloroacetone not converted .. 0

Monofluoropentachloroacetone 28.5

!, l-difluorotetrachloroacetone 63.1

Trifluorotrichloroacetone 7.0

Chlorofluorinated C ₂ compounds 0.9

Hexachloroethane 0.3

On leaving the second reaction zone, the mixture of perchlorofluorinated compounds contained an average of 4.2 fixed fluorine atoms per organic molecule, and the average ratio of the number of F atoms / number of Cl atoms per organic molecule was 2.15.

The organic part of the exhaust gas from the reactor was composed as follows:

Mole percent Hexafluoroacetone 79.6 Pentafluoromonochloroacetone 13.4 Tetrafluorodichloroacetone 1.8 Trifluorotrichloroacetone 0.1 Perchlorethylene 0.1 Tetrafhiordichl iräthan 0,4 Tnöuortnchiorethane 3.2 Difluorotetrachloroethane 0.9 Monofluoropentachloroethane 0.1 Various ^ compounds 0.4

The total degree of fluorination, based on HF, i.e. H. Mole HF consumed / Mole HF theoretically required, was 94.6% compared to 98.7% in Example 1. The exhaust gas contained 79.6% of the desired perfluorinated Compound compared to 96.8% in Example 1. The degree of decomposition as a result of side reactions was 5.1% compared to 1.9% in example 1.

The yield of hexafluoroacetone was 0.748 mol / h or 124 g per hour. Productivity was ίο 148 g / h / kg catalyst.

These results are all below those in the example! 1 and show that it is critical, the entirety of the first two fluorination steps to be carried out at a limited temperature in the first reaction zone.

The results are even worse if the residence time in the second catalyst zone is in favor the residence time in the third zone is reduced. It is not reached when exiting the second Zone a sufficient number of fluorine atoms which are bound on average per organic molecule, and cracking increases.

B e i s ρ i e 1 2

It was trichloroacetyl chloride in the same apparatus and with the same catalyst as in Example 1 (1.21, 0.84 kg) perfluorinated; the reactor was equipped with three catalyst layers, separated by Layers of spheres loaded with flaky aluminum oxide. The length of the individual catalyst zones fraud:

1st zone 48.0 cm,

2nd zone 35.0 cm,

3rd zone 37.0 cm.

The temperatures of the three zones were set to 240, 260 and 300 ^° C. with the aid of the heating elements fitted on the outside.

The reactor was filled with a mixture of trichloroacetyl chloride (99% purity) and anhydrous HF (99.7%) fed in the following quantities:

Trichloroacetyl chloride 0.97 mol / h

HF anhydrous 6.8 mol / h

The excess of anhydrous HF was 75%, based on the stoichiometrically required amount. The absolute pressure in the reactor was set to 1.3 bar. The residence times of the reactants in the three consecutive zones were 6.9 seconds, 4.8 seconds and 4.8 seconds.

Upon exiting the first catalyst zone were each organic molecule F atoms ge connected on average 2.5.

When leaving the second catalyst zone, there were on average 3.3 F atoms per organic molecule bound, and the average ratio of the number of F atoms / Cl atoms per organic molecule was 4.7.

The gas mixture emerging from the third catalyst zone had the following composition:

Trifluoroacetyl fluoride 97.1% Difluononochloroacetyl fluoride 0.07 % Fluorinated _Cr compounds 2.83%

The total degree of fluorination, based on HF, d. H. Mole HF consumed / Mole HF theoretically required was 97.2%.

The organic gas mixture flowing out contained 97.1% of the desired perfluorinated compound.

The degree of decomposition due to side reactions was 2.83%.

The production of trifluoroacetyl fluoride was 0.94 mol / h or 109 g / h. Productivity was 130 g / h / kg catalyst.

For comparison, the same compounds were used as just now, but at a temperature of 300 ^° C. in the entire reactor; the cracking resulted in the formation of CO and 12.3% chlorofluorinated Cj compounds.

It was again under the same conditions as above, but at a temperature of 260 ° C im worked throughout the reactor. This time the organic exhaust gas contained only 61% trifluoroacetyl fluoride, and productivity fell to 81.5 g / h / kg catalyst.

Example 3

It was octachlorobutanone in the same apparatus and on the same catalyst as in the example 1 (1.2 1, 0.84 kg) perfluorinated and with three catalyst layers in the reactor, separated by layers made from spheres of leafy aluminum oxide; the length of the catalyst zones was:

1st zone 40 cm,

2nd zone 31 cm,

3rd zone 49 cm.

The temperature of the reaction zones was adjusted to 244, 271 and 340 ° C. The following were fed in:

Octachlorobutanone (99.5%) 0.65 mol / h

HF anhydrous (99.7% purity) 6.76 mol / h

The excess of anhydrous HF, based on the stoichiometrically required amount, was 30%.

The absolute pressure in the reactor was set to 1.3 bar. The residence times of the reactants in the three consecutive zones were 6 seconds, 3.9 seconds and 6.2 seconds.

The mixture of perchlorofluorinated compounds exiting from the first zone contained on average 2.9 fluorine atoms bound per organic molecule.

The mixture of organic compounds emerging from the second zone contained an average of 5.0 fluorine atoms, bound according to an average ratio of number of F atoms / number of Cl atoms = 1.66.

The organic part of the exhaust gas from the third Zone was composed as follows:

Octafluorobutanone 95.3%

Heptafluoromonochlorobutanone 1.2%

Various chlorofluorinated products 3.5%

The total degree of fluorination, based on HF, d. H. Mole HF consumed / Mole HF theoretically required was 98.5%.

The target perfluorinated compound content of the exhaust gas was 95.3%.

The degree of decomposition due to side reactions reached 3.5%.

The production of octafluorobutanone was 0.62 mol / h or 134 g / h. The productivity was 159 g / h / kg of catalyst. A comparative experiment under otherwise identical conditions, but carried out at a temperature of 34O ⁰ C throughout the reactor: the cracking rate reached 27.8%, and the productivity increased to 120 g Octafluorbutanon per hour and per kg of catalyst from. The mixture obtained was extremely difficult to separate. Was carried out at a temperature of 271 ⁰ C throughout the reactor under otherwise identical conditions, so absolutely no Octaflucrbutanon was obtained: The exhaust gas did not contain perfluorinated product. In addition, the crack rate was 7.1%.

Example 4

It became anhydrous trichloroacetaldehyde in the same device and with the same catalyst perfluorinated as in Example 1 (1.2 l, 0.84 kg); Three catalyst layers were separated in the reactor made up of layers of spheres of flaky aluminum oxide; the length of the individual catalyst zones fraud:

1st zone 70 cm,

2nd zone 25 cm,
3 zone 25 cm.

The temperature of the three zones was set at 240, 260 and -280 ° C. The following was added to the reactor Mixture fed in:

Trichloroacetaldehyde anhydrous

(99.9%) 1.15 moles / hour

HF anhydrous (99.7%) 6 times / h

The excess of anhydrous HF was 74%.

based on the stoichiometrically required amount. The absolute pressure in the reactor was set to 1.3 bar. The residence times of the reactants in the three successive zones were 10.9 seconds in the first zone, 3.8 seconds in the second zone and 3.6 seconds in the third zone.

The gas mixture emerging from the first catalyst zone contained 2.2 fluorine atoms per organic molecule bound. When leaving the second zone, there were 2.6 fluorine atoms per molecule in the gas mixture.

bond, and the mean ratio number of F atoms: / The number of Cl atoms was 6.25.

The organic part of the exhaust gas from the third catalyst zone was composed as follows:

Trifluoroacetaldehyde 97.4%

Difluoromonochloroacetaldehyde 1.9%

Fluorinated Q compounds 0.7 ° ₀

The total degree of fluorination, based on HF, was 98.9%.

The organic part of the exhaust gas contained 97.4% of the desired perfluorinated compound.

The degree of decomposition due to side reactants was 0.7%.

The production of Trifluoracetaldehvd betrus 1.12 mol / h or 110 g / h. The productivity was 131 g / h and per kg of catalyst.

For comparison, operating at a temperature prior to 28O ⁰ C throughout the reactor, the cracking rate reached 8.9% in this case.

In another comparative test bz 260 ⁰ C throughout the reactor was working. The Abga> contained only 69.4% trifluoroacetaldehyde; the productivity fell to 93.3 g / h per kg of catalyst, and the purification of the trifluoroacetaldehyde obtained was extremely difficult.

The examples given show the advantages of the Ver drive clearly recognize according to the invention. The new method involves working with three reac

tion zones with increasing from the first to the third zone Temperature critical to achieve very good results. Correspondingly, these three can be consecutive Reaction zones can be divided into sub-zones. The formation of the reaction zones with

increasing temperature in the catalyst bed can take place in any known manner. The catalyst bed can be carried out in a single reactor continuously or in separate portions or in successive portions Reactors are included.

Claims (1)

tional compounds with hydrogen fluoride in vapor phase ^{and in the} presence of a catalyst, preferably based on chromium. With the known Process for the perfluorination of perchlorinated processes, which describe this measure, carbonyl compounds with 2 to 4 carbon 5 are specified that at a reaction temperature of atoms in the molecule through continuous reaction 200 up to 600 ⁰ C is to be carried out and the tion of the perchlorinated compounds with over implementation examples indicate that the reaction temperature, anhydrous hydrogen fluoride, amounts to 250 to 380 C in practice.
Vapor phase in the presence of a fluorination Under these conditions, the catalyst can in fact be characterized at temperatures from 220 to 350 ⁰ C, io successive fluorination stages in the fact that functional perchlorinated compounds are sought carry out application. In practice, however, two occur a) the reactants under an absolute- Kind of difficulty in doing so: pressure of 1 to 4 bar, preferably 1.2 If, for example, the fluorination of hexachloro to 2.5 bar, by means of a three successive acetone is under relatively mild conditions, that is constructed in the following zones of catalyst a temperature of 250 ⁰ C and a throughput of the fixed bed in one zone to the next in order of 66.4 g and hexachloroacetone 65.5 g HF per hour at least 1O ⁰ C as the temperature increases and per kg of catalyst, in the presence of a good passes, carried out the catalyst, the fluorination proceeds b) the first two steps of the fluorination ao incomplete in the last steps and affects overall in the first zone at a temperature not the entire originally used compound, temperature of 220 to 250 ⁰ C, then a mixture of different is obtained c) the fluorination in the second zone in the case of a chlorofluorinated compound, below which the per-T; mperatur from 250 to 275 ° C and only a small proportion of fluorinated compounds d) in the third zone makes _{the complete per- a 5.} If only the preparation of the perfluorofluorination of the intermediate products from c), the th compound is sought, the mixture of at least 1.5 fluorine atoms present in the obtained mixture, still containing chlorine atoms and containing 1 chlorine atom, are compounds by-products at one temperature, and the performance from 275 to 35O ° C. of the process with regard to the desired perfluorinated 30 th connection is greatly reduced. In the example just described, the Yield of hexcfluoroacetone, monochloropentafluoro acetone and dichlorotetrafluoroacetone only 29.7 g each Hour and per kg of catalyst; this is extraordinary The invention relates to a method for 35 little. The resulting mixture of organic perfluorination of perchlorinated carbonyl compounds contains 38 mol percent dichlorotetrafluorogen with 2 to 4 carbon atoms in the molecule due to acetone, 20 mol percent monochloropentafluoroacetone continuous reaction of the perchlorinated compounds and 4 mol percent hexafluoroacetone, a total of 62 moldings with excess anhydrous fluorine water percent and 29 mol percent trichlorotrifluoroacetone, substance in the vapor phase in the presence of a fluorine 40 8 mol percent tetrachlorodifluoroacetone and 1 Molprorungskaulysators at temperatures from 220 to 350 ⁰ C. cent different C ₄ compounds. The yield at The perchlorinated carbonyl compounds contain the desired perfluorinated compound is therefore exceptionally low in its molecule of trichloromethyl groups (- CCl ₃ ) and is only 1.65 g per hour or Peiitachloräthylgruppen (- C ₈ Cl ₆ ) and no and per kg of catalyst. Hydrogen atom more, which is replaced by a chlorine atom 45 This result can of course be replaced by this can be. improve that the mixture obtained is present It is known that in the catalytic fluorination which chlorofluorinated by-products are separated off and of perhalogenated carbonyl compounds such as tri- they undergo further fluorination in the vapor phase with chloroacetyl chloride or hexachloroacetone rejects this: step by step by alternating separation bindings 1 in the liquid phase or in the vapor phase with 50 and additional fluorination of the still chlorine-containing Hydrogen fluoride in the presence of a catalyst to compounds can be the yield of the desired treat. When working in the liquid phase, improve for example perfluorinated compound. The performance in the presence of antimony halides, however, the ability of the process remains exceptional Catalysts, the fluorination is incomplete, weak; in addition, this procedure is compli- and the corresponding perfluorinated compounds 55 graceful and time consuming. It would of course be easier and cannot be preserved. more economical to have a process that To get the perfluorinated compounds, starting from ches immediately in a single pass of the perchlorinated carbonyl compounds, to obtain reactants to the desired perfluorinated namely must successively all the chlorine atoms of the compound in increased yield and with improved Starting compound can be replaced by fluorine; this leads to 60 efficiency. requires the implementation of just as much at one time. If, on the other hand, the fluorination takes place at higher other subsequent fluorination steps, such as the equipment (300 to 350 ⁰ C) carried out to produce the product mixture contains chlorine atoms in the molecule, increase the activity of the desired perfluorinated compound to, for example, four successive steps in the case of, as a result of the development of Trichloroacetyl chloride or six successive side reactions on a considerable scale (more than the following steps in the case of hexachloroacetone. 10 mol percent), which are caused by decarbonylation of the keto The desired result can be achieved, compounds to unusable by-products by performing the fluorination of the perchlorinated func- tions, only limited yields are obtained. About it