Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2001-02-28
2003-07-08
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
Reexamination Certificate
active
06590130
ABSTRACT:
A subject-matter of the present invention is a process for the preparation of 1,1,1-trifluoro-2,2-dichloroethane (F123) by catalytic chlorination of 1,1,1-trifluoro-2-chloroethane (F133a) in the presence of hydrogen fluoride (HF). The invention also relates to the application of this process to a process for the manufacture of pentafluoroethane (F125).
As the compounds F123 and F125 can be used as substitutes for perchlorofluorocarbons (CFC) in the field of aerosols (propellants) and in that of refrigeration, there is currently a search for high performance processes for their industrial production.
WO 95/16654 discloses an operation in which F133a is brought into contact at a temperature of 340° C. with chlorine and HF in the presence of a chromium catalyst. Although the conversion of F133a in this reaction is high, it predominantly produces 1,1,1,2-tetrafluoroethane (F134a) at this temperature. Thus, the selectivity of F123 does not exceed 15%, which does not allow production of this compound under industrially acceptable conditions to be envisaged.
WO 94/11327 mentions an operation in which F133a is brought into contact, at temperatures of less than 300° C., with chlorine and HF in the presence of a chromium catalyst. This reaction is carried out with a very large excess of chlorine and of HF and preferably results in the formation of F124 and of F125; thus, the selectivity for F123 remains below 8% and the 110 series/120 series ratio is greater than 10%.
EP-A-526 908 and EP-A-346 612 provide for the preparation of F123 by bringing chlorine into contact with F133a at a temperature preferably lying between 350 and 450° C. in the absence or in the presence of a catalyst, this chlorination being carried out in the absence of HF.
U.S. Pat. No. 4,145,368 provides a process which consists in reacting chlorine with F133a, and then separating the F123 from the reaction mixture, and in reacting the F113a resulting from this separation with a fresh amount of F133a, this reaction being carried out in the vapour phase and preferably between 350 and 425° C. in the present of a catalyst, such as a chromium oxide.
According to this document, the final selectivity for F123 does not exceed 29%.
EP-B-407 990 provides for the chlorination of F133a to F123 by thermal or catalytic activation in the liquid phase under pressure. The selectivity for F123 can range from 67.9 to 83.4%, the reaction pressure ranging from 50 to 127 bar.
EP-A-402 874 provides for the reaction of the chlorine with F133a between 350 and 450° C. in the absence of catalyst and of HF. According to this document, the production of F113a can be eliminated by virtue of a specific combination of conditions relating to temperature, contact time and molar ratio of the reactants.
U.S. Pat. No. 5,414,166 provides for chlorination of F133a in the presence of hydrogen between 250 and 500° C. and preferably between 350 and 450° C.; the selectivity for F123 can range from 65 to 92%.
U.S. Pat. No. 5,723,700 discloses a stage during which F133a, HF and Cl
2
react in the presence of a fluorination catalyst between 300 and 450° C. to produce essentially F134a and traces of F123.
The invention provides a process for the preparation of F123 by chlorination of F133a, according to which a relatively moderate temperature is employed.
The invention also provides a process for the preparation of F123 by chlorination of F133a, according to which the pressure employed is atmospheric pressure or a moderate pressure, for example not exceeding 25 bar.
The invention also provides a process for the preparation of F123 by chlorination of F133a, according to which a chlorination and/or fluorination catalyst is present.
The invention also provides a process for the preparation of F123 by chlorination of F133a, according to which a selectivity for F123 of greater than 50% is obtained.
The invention also provides such a process, according to which the selectivity for F123 is greater than 70%.
The invention more specifically provides a process for the preparation of 1,1,1-trifluoro-2,2-dichloroethane (F123) by bringing 1,1,1-trifluoro-2-chloroethane (F133a) into contact with chlorine, the said process being characterized in that the said contacting operation is carried out in the presence of HF and of a catalyst under conditions of temperature and of contact time and with Cl
2
/F133a and HF/F133a molar ratios such that HF does not substantially react with the F133a and the F123 formed and promotes the selectivity for F123.
The invention relates more particularly to a process such that HF does not substantially react with the F133a and the F123 to give more highly fluorinated derivatives, such as F124 or F134a.
In the implementation of the process according to the invention, it is advisable to choose operating conditions such that HF behaves essentially as diluent and/or stabilizer for the reaction and the reactants and not as reactant in a fluorination reaction. The temperature conditions, the Cl
2
/F133a and HF/F133a molar ratios and the contact time can generally be chosen within the ranges known for this type of chlorination reaction and such as reported, for example, above with reference to the documents relating to the said chlorination reaction.
Purely by way of illustration and which should not, for this reason, limit the field of the invention, orders of magnitude recommended for the operating conditions in question will be indicated below.
The temperature of the reaction mixture is generally between 150 and 320° C. This temperature is preferably between 250 and 300° C.
The chlorine/F133a molar ratio can be between 0.01 and 0.50 and it is preferably between 0.05 and 0.15.
The HF/133a molar ratio can generally be between 0.5 and 2.5. For practical reasons, related inter alia to the separation of the products for the purpose of the recycling of the unconsumed reactants and of the HF, a ratio between 0.8 and 1.2 is preferably chosen.
The time for contact between F133a, chlorine and HF over the catalyst can be between 5 and 100 seconds; it is recommended to have a contact time of between 10 and 60 seconds. The contact time is calculated here as the ratio of the apparent volume of the catalyst to the total flow rate by volume of the gases fed to the reactor under the reaction pressure and temperature conditions.
The catalysts which can be used for this invention are the chlorination catalysts which are known to a person skilled in the art and which are resistant to hydracids, such as HF and HCl. However, preference is given to catalysts generally used for fluorination reactions with HF. Mention may be made, by way of indication, of bulk or supported catalysts (supported on fluorinated alumina or on charcoal, for example) based on Cr, Zn, Ni or Mg oxide, alone or as a mixture. For this invention, preference will be given to mixed catalysts composed of nickel and chromium oxides, halides and/or oxyhalides deposited on a support composed of aluminium fluoride or of a mixture of aluminium fluoride and of alumina, such as disclosed, for example, in Patents FR 2 669 022 and EP-B-0 609 124.
Prior to the chlorination reaction, the catalyst can be conditioned, if necessary by heat treatment in the presence of Cl
2
and/or HF, for example by following the method disclosed in EP-B-0 609 124.
When a mixed nickel/chromium catalyst is used, catalysts comprising, by mass, from 0.5 to 20% of chromium and from 0.5 to 20% of nickel and more particularly those comprising from 2 to 10% by mass of each of these metals in a nickel/chromium atomic ratio of between 0.1 and 5, preferably in the region of 1, will be recommended.
As has been specified, the process in accordance with the invention consists in particular in bringing chlorine into contact with F133a, in the presence of HF and of a catalyst, under conditions such that HF does not substantially react with the F133a and the F123 formed to give more highly fluorinated derivatives. These conditions are advantageously chosen within the temperature, molar ratio and contact time regions indicated above and it would be up to
Jorda Eric
Lacroix Eric
Perdrieux Sylvain
Atofina
Clifford Chance US LL
Price Elvis O.
Richter Johann
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