Field of the Invention
The present invention provides a process for the preparation of 1 -chloro-2, 2-difluoroethane by
gas phase fluorination of 1, 1, 2-trichloroethane and/or 1, 2-dichloroethene. The present
invention also provides a process for purification of 1 -chloro-2,2-difluoroethane.
Background of the Invention
The l-chloro-2, 2-difluoroethane is known to be useful as a foam blowing agent and can be
employed as a starting material in the preparation of various agrochemicals or pharmaceuticals
products.
EP Patent Publication No. 1,008,575 provides a process for preparing 1 -chloro-2, 2-
difluoroethane by contacting 1, 1, 2-trichloroethane with HF in the gas phase in the presence of
chromium oxide.
EP Patent Publication No. 1,008,574 provides a process for preparing l-chloro-2, 2-
difluoroethane by contacting 1, 2-dichloroethene with HF in the presence of fluorinated salt of
chromium, iron, niobium, tin, tantalum and titanium.
FR Patent Publication No. 2,783,820 describes a method for the preparation of l-chloro-2, 2-
difluoroethane by fluorinating 1, 1,2-trichloroethane with HF in the gas or liquid phase. The gas
phase reaction is camed out at a temperature between 120°C and 400°C using a solid chrome
catalyst or a chrome catalyst deposited on carbon, A1203 or AlF3.
PCT Publication No. WO 2013/053800 provides a catalyst for vapor phase fluorination of I, 1,
2-trichloroethane andfor 1, 2-dichloroethene with HF. The catalyst for fluorination is prepared by
co-depositing FeC13 and MgClz on chromia- alumina, or co-depositing Cr(N03)3 and Ni(N03)2
on active carbon, or by doping alumina with ZnC12. The WOL800 also mentions that the
separation of 1, 2-dichloroethene from l-chloro-2, 2-difluoroethane can be done by distillation in
a glass column. However, there is no further mention of any means or method to do the same.
Furthermore, the EP Patent Publication Nos. 1,008,574 and 1,008,575 state that unsaturated
organic by- products of gas phase fluorination may be separated by first reacting the product
mixture with chlorine or bromine prior to distillation to get pure 1 -chloro-2, 2-difluoroethane.
While carrying out the due experimentation, the present inventors have found that it is difficult to
separate trans-1, 2-dichloroethene from 1-chloro-2, 2-difluoroethane in conventional distillation
column as trans- 1, 2-dichloroethene forms a low boiling azeotrope with 1 -chloro-2, 2-
difluoroethane. The present inventors also observed that preforming chlorination or bromination
to separate unsaturated by-products, for example, trans-1, 2-dichloroethene results in formation
of tetra-chloroethane or 1,2-dichloro-l,2-dibromoethane. The formation of these
bromination/chlorination products results in quantum yield loss.
Such synthesis, with respect to what is known in the prior art, is apparently advantageous in that
it requires few steps and reagents. However, the conversion rates and selectivity towards the
preparation of 1-chloro-2, 2-difluoroethane in EP Patent Publication Nos. 1,008,574 and
1,008,575 is not reproducible.
Such non-reproducible results and yield is unsatisfactory in terms of industrial application, and it
is essentially due to these reasons, there still arises the need for providing an efficient as well as
economic reagents and purification methods that can be used at industrial scale for the synthesis
of 1 -chloro-2,2-difluoroethane.
Surnrnarv of the Invention
The present invention provides a process for preparation of 1-chloro-2, 2-difluoroethane
starting from 1, 1, 2-trichloroethane and/or 1, 2-dichloroethane with specific catalyst. The
present invention also provides a process for purification of 1-chloro-2,2-difluoroethane.
The one aspect of the present invention provides a process for preparation of 1-chloro-2, 2-
difluoroethane comprising;
a) contacting 1, 1, 2-trichloroethane and/or 1, 2-dichloroethene with hydrogen fluoride in
the gas phase in the presence of a zinc promoted chromia catalyst, and
b) recovering 1-chloro-2,2-difluoroethane from the resultant mixture in step a).
The second aspect of the present invention provides a process for preparation of 1-chloro-2, 2-
difluoroethane comprising;
a) contacting 1, 1, 2-trichloroethane andlor I, 2-dichloroethene with hydrogen fluoride in
the gas phase in the presence of a supported or unsupported chromia catalyst,
b) subjecting the contents of step a) to distillation, wherein distillation is carried out at about
5.0 to about 7.0 kg/cmIg pressure to obtain azeotropic composition of 1-chloro-2, 2-
difluoroethane and trans-l,2-dichloroethene about 93 % and about 7 % respectively,
c) subjecting the contents of step b) to distillation, wherein distillation is carried out at about
0.05 to about 0.3 kg/cm2g pressure, and
d) recovering 1-chloro-2,2-difluoroethane from step c).
The third aspect of the present invention provides a process for purification of 1-chloro-2, 2-
difluoroethane comprising;
a) subjecting an organic layer to distillation, wherein distillation is carried out at about 5.0
to about 7.0 kg/cmZg pressure to obtain azeotropic composition of 1-chloro-2, 2-
difluoroethane and trans-I, 2-dichloroethene in the range of about 93 % and about 7 %
respectively,
b) subjecting the contents of step a) to distillation, wherein distillation is carried out at about
0.05 to about 0.3 kg/cm" pressure, and
c) recovering 1 -chloro-2,2-difluoroethane from step b),
wherein the organic layer of step a) comprises a mixture of 1, 1, 2-trichloroethane;
cisltrans- 1, 2-dichloroethene; 1 -chloro-2, 2-difluoroethane, 1 -fluoro-2-chloroethene and
1 -fluoro- l,2-dichloroethane.
Detailed Description of the Invention
In one embodiment, the present invention provides a process for preparation of 1-chloro-2, 2-
difluoroethane comprising;
a) contacting 1, 1, 2-trichloroethane andlor 1, 2-dichloroethene with hydrogen fluoride in
the gas phase in the presence of a zinc promoted chromia catalyst, and
b) recovering 1-chloro-2,'-difluoroethane from the resultant mixture in step a).
The zinc promoted chromia catalyst may be activated at a temperature of about 300°C to about
400°C. The activation may be done by co-feeding a mixture of anhydrous hydrogen fluoride and
nitrogen over the zinc promoted chromia catalyst bed for about 40 hours to about 75 hours.
The reaction of 1, 1, 2-trichloroethane and/or 1, 2-dichloroethene with hydrogen fluoride in the
gas phase in the presence of a zinc promoted chromia catalyst in a reactor may be carried out at a
temperature of about 200°C to about 350°C, for example, about 250°C to about 300°C.
The 1, 1, 2-trichloroethane and anhydrous hydrogen fluoride may be used in a molar ratio of
about 1 : 10 to about 1 :20, for example, in a molar ratio of about 1 : 12 to about 1 : 15. The pressure
of the reactor may be maintained at about 5 bar to about 20 bar, for example, about 10 bar to
about 15 bar.
The 1-chloro-2, 2-difluoroethane may be recovered from the reaction mixture by distillation,
evaporation, layer separation or mixture thereof.
In another embodiment, the present invention provides a process for preparation of 1-chloro-2,2-
difluoroethane comprising;
a) contacting 1, 1, 2-trichloroethane andlor 1, 2-dichloroethene with hydrogen fluoride in
the gas phase in the presence of a supported or unsupported chromia catalyst,
b) subjecting the contents of step a) to distillation, wherein distillation is carried out at about
5.0 to about 7.0 kg/cm'g pressure to obtain azeotropic composition of 1-chloro-2, 2-
difluoroethane and trans- 1, 2-dichloroethene in the range of about 93 % and about 7 %
respectively,
c) subjecting the contents of step b) to distillation, wherein distillation is carried out at about
0.05 to about 0.3 kg/cm2g pressure, and
d) recovering 1-chloro-2,2-difluoroethanefr om step c).
In yet another embodiment, the present invention provides a process for purification of 1 -chloro-
2,2-difluoroethane comprising;
a) subjecting an organic layer to distillation, wherein distillation is carried out at about 5.0
to about 7.0 kg~crn'p~r essure to obtain azeotropic composition of 1-chloro-2, 2-
difluoroethane and trans-1, 2-dichloroethene in the range of about 93 % and about 7 %
respectively,
b) subjecting the contents of step a) to distillation, wherein distillation is carried out at about
0.05 to about 0.3 kg/cmzg pressure, and
c) recovering 1 -chloro-2,2-difluoroethane from step b),
wherein the organic layer of step a) comprises a mixture of 1, 1, 2-trichloroethane;
cisltrans- 1, 2-dichloroethene; 1 -chloro-2, 2-difluoroethane, 1 -fluoro-2-chloroethene and
1 -fluoro- l,2-dichloroethane.
The supported or unsupported chromia catalyst may be activated at a temperature of about 300°C
to about 400°C. The activation may be done by co-feeding a mixture of anhydrous hydrogen
fluoride and nitrogen over the chromia catalyst bed for about 40 hours to about 75 hours.
The reaction of 1, 1, 2-trichloroethane andlor 1, 2-dichloroethene with hydrogen fluoride in the
gas phase in the presence of a supported or unsupported chromia catalyst in a reactor may be
carried out at a temperature of about 200°C to about 350°C, for example, about 250°C to about
300°C.
The 1, 1, 2-trichloroethane and anhydrous hydrogen fluoride may be used in a molar ratio of
about 1 : 10 to about 1 :20, for example, in a molar ratio of about 1 : 12 to about 1 : 17. The pressure
of the reactor may be maintained at about 5 bar to about 20 bar, for example about 10 bar to
about 15 bar.
The mixture or organic layer comprises 1, 1, 2-trichloroethane; cisltrans- 1, 2-dichloroethene; 1 -
chloro-2, 2-difluoroethane, 1 -fluoro-2-chloroethene and 1 -fluoro- 1, 2-dichloroethane. The
organic layer may have azeotropic composition of 1 -chloro-2, 2-difluoroethane and trans- 1, 2-
dichloroethene about 65 % and about 10 % respectively, for example, about 68% and about 9%
respectively. The mixture or organic layer is subjected to distillation carried out at pressure of
about 5.0 to about 7.0 kg/cm2g to obtain azeotropic composition of 1-chloro-2, 2-difluoroethane
and trans-l,2-dichloroethene in the range of 93 % and 7 % respectively. The azeotrope of trans1,2-
dichloroethene and 1 -chloro-2, 2-difluoroethane may be recovered from distillation column.
The azeotrope of trans- 1, 2-dichloroethene and 1-chloro-2, 2-difluoroethane is subjected to
distillation at a pressure of about 0.05 to about 0.3 kg/cmZg.
The process of present invention is preferably carried out in a continuous mode.
The 1 -chloro-2,2-difluoroethane is recovered from distillation column.
While the present invention has been described in terms of its specific embodiments, certain
modifications and equivalents will be apparent to those skilled in the art and are intended to be
included within the scope of the present invention.
Examples
Preoaration of 1 -Chloro-2.2-Difluoroethane
(A)The chromia catalyst (562 g) was taken into 1" tubular reactor. The chromia catalyst was
activated by co-feeding a mixture of anhydrous hydrogen fluoride and nitrogen over
chromia catalyst for about 66 hours. The anhydrous hydrogen fluoride (1 3 1 ghour), 1, 1,
2-trichloroethane (59.5 g/hour) were passed through the reactor bed at about 250°C for
about 126 hours. The pressure of the reactor was maintained at about 10 ki~o~ram/crn*~).
The composition of reactor outlet organic was found to be as follows:
Trans- 1, 2-dichloroethene 9.0%
Cis - 1,2-dichloroethene 14.0%
Others 1 .O%
(B)The zinc promoted chromia catalyst (562 g) was taken into 1" tubular reactor. The zinc
promoted chromia catalyst was activated by co-feeding a mixture of anhydrous hydrogen
fluoride and nitrogen over zinc promoted chromia catalyst for about 66 h. The catalyst
bed temperature was reduced to 250°C. The anhydrous hydrogen fluoride (1 3 1 ghour), 1,
1, 2-trichloroethane (59.5 ghour) were passed through the reactor bed at about 250°C for
about 354 hours. The pressure of the reactor was maintained at about 10 k i l ~ ~ r a d c m ' ~ ) .
The composition of reactor outlet organic was found to be as follows:
Trans- 1, 2-dichloroethene 9.0%
Cis - I, 2-dichloroethene 16%
Others 0.6%
The Purification of 1-Chloro-2.2-Difluoroethane
A mixture or organic layer containing 1, 1, 2-trichloroethane (2.1 %), cis- 1, 2-dichloroethene
(20.2%), trans- 1, 2-dichloroethene (12.3%), 1 -chloro-2, 2-difluoroethane (62.6%), 1 -fluoro-2-
chloroethene (1.15%) and 1-fluoro-1, 2-dichloroethane (1.0%) was taken into distillation
column. The distillation column was operated at a pressure of about 5.0 to about 7.0 kg/cm".
The azeotropic mixture of composition 91%:7.2% of 1-chloro-2, 2-difluoroethane: trans- 1, 2-
dichloroethene was recovered from the top of distillation column. The 91%:7.2% of 1-chloro-2,
2-difluoroethane: trans- 1, 2-dichloroethene azeotropic mixture was taken into another
distillation column. The distillation column was operated at a pressure of about 0.05 to about 0.3
kg/cm2g. The 1-chloro-2,2-difluoroethane was recovered from the column.

We Claim:
1. A process for preparation of 1 -chloro-2,2-difluoroethane comprising;
a) contacting 1, 1, 2-trichloroethane andlor 1, 2-dichloroethene with hydrogen fluoride in
the gas phase in the presence of a zinc promoted chromia catalyst, and
b) recovering 1 -chloro-2,2-difluoroethane from the resultant mixture in step a).
2. The process of claim 1, wherein zinc promoted chromia catalyst is activated at a
temperature in the range of 300°C to 400°C.
3. The process of claim 2, wherein the activation is done by co-feeding a mixture of
anhydrous hydrogen fluoride and nitrogen over the zinc promoted chromia catalyst bed
for a time period in the range of 40 hours to 75 hours.
4. The process of claim 1, wherein 1-chloro-2, 2-difluoroethane is recovered from the
reaction mixture by distillation, evaporation, layer separation or mixture thereof.
5. A process for preparation of 1 -chloro-2, 2-difluoroethane comprising;
a) contacting 1, 1, 2-trichloroethane andlor 1, 2-dichloroethene with hydrogen fluoride in
the gas phase in the presence of a supported or unsupported chromia catalyst,
b) subjecting the contents of step a) to distillation, wherein distillation is carried out at 5.0
to 7.0 kgIcm2g pressure to obtain azeotropic composition of 1-chloro-2, 2-
difluoroethane and trans- l,2-dichloroethene 93 % and 7 % respectively,
c) subjecting the contents of step b) to distillation, wherein distillation is carried out at a
pressure in the range of 0.05 to 0.3 kglcm2g , and
d) recovering 1-chloro-2,2-difluoroethanefr om step c).
6. The process of claim 5, wherein the supported or unsupported chromia catalyst is
activated at a temperature in the range of 300°C to 400°C.
7. A process for purification of I-chloro-2,2-difluoroethane comprising;
a) subjecting an organic layer to distillation, wherein distillation is carried out at 5.0 to 7.0
kg/cm2g pressure to obtain azeotropic composition of 1-chloro-2, 2-difluoroethane and
trans-I, 2-dichloroethene of 93 % and 7 % respectively,
b) subjecting the contents of step a) to distillation, wherein distillation is carried out at a
pressure in the range of 0.05 to 0.3 kgIcm2g , and
c) recovering 1-chloro-2,2-difluoroethane from step b),
wherein the organic layer of step a) comprises a mixture of 1, 1, 2-trichloroethane;
cis/trans- 1, 2-dichloroethene; 1 -chloro-2, 2-difluoroethane, 1-fluoro-2-chloroethene
and I -fluoro- l,2-dichloroethane.
8. The process of claims 1, 5 or 7, wherein the process is carried out in a continuous mode.