TECHNICAL FIELD:
The present disclosure relates to a process for the preparation of 2,3,3,3-tetrafluoropropene
(HFO 1234yf). More specifically, the present disclosure relates to a process for the preparation of
2,3,3,3-tetrafluoro propene (HFO 1234yf) which is economically viable and gives high yield of HFO
1234yf.
BACKGROUND:
2,3,3,3-Tetrafluoro propene (HFO 1234yf) is a compound with low toxicity and low global
warming potential and thus the molecule preferred as a suitable replacement of the existing
refrigerants. The fluorocarbon industry has been working for the past few years to develop a cost
effective process to manufacture HFO-1234yf in large quantity.
J. Chem. Soc. 1957, 2193, discloses a process for producing HFO-1234yf, using CF3CF2CH2X
(X= C1 or I) with zinc and methanol. Process can not be used as an industrial process, because zinc is
expensive and large amount of waste are produced.
US 201110245350 A1 discloses a process for making HCFC-1234yf or mixture thereof with
1234ye by reacting at least one compound selected from the group consisting of CFC-215 cb and CFC-
2 15 ca with hydrogen in a reaction zone over a suitable catalyst. The isomer CFC-215 cb is essentially
free of isomer CFC-215 ca by reacting TFE with CFC-11 in presence of aluminum chlorofluoride in a
mole ratio of at least 1 : 1. Under these condition CFC-2 15 ca formed as a co-product with CFC-2 15 cb
react with additional TFE to form CFC-419lca, which directly affect the overall yield of the process,
therefore the process is not considered as an effective industrial process.
U.S. 2,931,840 describes a process for producing HFO-1234yf where in TFE (CF2=CF2) and
CH3C1 are reacted in gas phase at 850 "C. The process yield is about 5%, which is too low for a
commercial process.
U.S. 7,396,965 discloses a process for the production of HFO-1234yf by reacting TFE and
CH3F in the presence of SbF5 supported on activated carbon. SbFs is a highly toxic and corrosive
compound, thus poses many problems in terms of industrial purpose.
WO 201010 13795 discloses a process for producing HFO-1234yf using TFE. In the process
HCFC-214cb is obtained by reacting TFE with carbontetrachloride, HFO-1234yf is produced from the
halogenated fluoropropane by following the steps of hydrodehalogenation followed by
dehydrofluorination and fluorination. Process developed with excess quantity of solvent, which may
result in high cost and difficulty in separation. Thus, the process poses problems for industrial
application.
US 8,063,257 discloses a method for preparing 2,3,3,3-tetrafluoropropene comprising
contacting a reactant comprising CC12=CFCH2Cl with a fluorinating agent, such as HF, in the
presence of at least one catalyst selected from the group consisting of chromiurn(III)oxide, fluorinated
chromium oxide, iron(1II) chloride, activated carbon, transition metal halides, SbC15, SbClnF5-n,
SnC14, TiC14, and FeC13 under conditions effective to produce a product comprising CF3CF=CH2.
Since, this reaction uses catalyst like SbF5 which is corrosive and thus can not be used for the industrial
application.
US 8,071,826 discloses a process for the preparation of 2,3,3,3-tetrafluoropropene (HFO-
1234yf) comprising reacting chlorotrifluoroethylene with a methyl halide to form an intermediate
product stream and reacting the intermediate product stream with hydrogen fluoride to thereby produce
2,3,3,3-tetrafluoropropene.H FO-1234yf is a refrigerant with low global warming potential.
SUMMARY :
An aspect of the present disclosure provides a process for the preparation of 2,3,3,3-tetrafluoro
propene (HFO-1234yf), comprising:
i. reacting tetrafluoroethylene with a compound having general formula CX3F,wherein X=C1,
Br or I, at a temperature in the range of -15 to 75 "C for a time period in the range of 0.5 to
10 hrs in the presence of a lewis acid catalyst to obtain a first mixture of CF3-CF2-CX3 and
XCF2-CF2-CX2F;
ii. refluxing the first mixture with an aluminium halide having the formula AlClxBryFz,
wherein x =O to 3, y =O to 3, z =O to 2 and x+y+z=3, at a temperature in the range of -20 to
75 "C for a time period in the range of 1 to 4 hrs to obtain a second mixture of CF3-CF2-
CX3 and XCF2-CF2-CX3w, herein X= Br, C1 or I;
iii. reducing CF3-CF2-CX3 and XCF2-CF2-CX3 with hydrogen in a catalyst bed at a temperature
in the range of 75 - 200 OC to obtain CF3-CF2-CH3 and XCF2-CF2-CH3 respectively;
iv. dehydrofluorinating and fluorinating the XCF2-CF2-CH3 as obtained in step (iii), in the
presence of a catalyst at a temperature in the range of 300-450 "C to obtain 2,3,3,3-
tetrafluoro propene; and
v. dehydrofluorinating the CF3-CF2-CH3 as obtained in step (iv), in the presence of a catalyst at
a temperature in the range of 300-450 "C to obtain 2,3,3,3-tetrafluoro propene.
Another aspect of present disclosure provides a process for the preparation of HFO-1234yf in
high yield by converting the unwanted isomer XCF2-CF2-CX2F to XCF2-CF2-CX3.
Further an aspect of the present disclosure provides a method to separate CF3-CF2-CX3 fiom the
mixture of CF3-CF2-CX3 and XCF2-CF2-CX2F isomers, where in X=Br, C1 or I.
These and other features, aspects, and advantages of the present subject matter will become
better understood with reference to the following description. This summary is provided to introduce a
selection of concepts in a simplified form. This summary is not intended to identify key features or
essential features of the subject matter, nor is it intended to be used to limit the scope of the subject
matter.
DETAILED DESCRIPTION:
The present disclosure provides a process for the preparation of 2,3,3,3-tetrafluoro propene
(HFO- 1234yf), comprising:
i. reacting tetrafluoroethylene with a compound having general formula CX3FYwhereinX =C1,
Br or I, at a temperature in the range of -15 to 75 "C for a time period in the range of 0.5 to
10 hrs in the presence of a lewis acid catalyst to obtain a first mixture of CF3-CF2-CX3 and
XCF2-CF2-CXzF;
ii. refluxing the first mixture with an aluminium halide having the formula AlClxBryFz,
wherein x =O to 3, y =O to 3, z =O to 2 and x+y+z=3, at a temperature in the range of -20 to
75 "C for a time period in the range of 1 to 4 hrs to obtain a second mixture of CF3-CF2-
CX3 and XCF2-CF2-CX3w, herein X= Br, C1 or I;
iii. reducing CF3-CF2-CX3 and XCF2-CF2-CX3 with hydrogen in a catalyst bed at a temperature
in the range of 75-200 "C to obtain CF3-CF2-CH3a nd XCF2-CF2-CH3re spectively;
iv. dehydrofluorinating and fluorinating the XCF2-CF2-CH3 as obtained in step (iii), in the
presence of a catalyst at a temperature in the range of 300-450 "C to obtain 2,3,3,3-
tetrafluoro propene; and
v. dehydrofluorinating the CF3-CF2-CH3 as obtained in step (iii), in the presence of a catalyst
at a temperature in the range of 300-450 "C to obtain 2,3,3,3-tetrafluoro propene.
In an embodiment of the present disclosure the lewis acid used is selected from the group
consisting of BF3, BC13, BBr3, AlF3, AlCl3, A1Br3, FeC13, NiC12, SbFS and SbCIS.
In another embodiment of the present disclosure the amount of lewis acid catalyst is in the
range of 0.03 to 1.5 moles with respect to tetrafluoroethylene.
In yet another embodiment of the present disclosure the first mixture is reacted with aluminium
halide in a ratio in the range of 3% to 15% weight of aluminium halide with respect to the weight of the
first mixture.
In yet another embodiment of the present disclosure the catalyst bed consist of metal catalyst
selected from the group consisting of platinum, palladium, nickel and rhodium.
In yet another embodiment of the present disclosure the catalyst bed consist of catalyst carriers
selected from the group consisting of alumina and activated carbon.
In yet another embodiment of the present disclosure CF3-CF2-CX3 and XCF2-CF2-CX3 are
separated from the second mixture.
In yet another embodiment of the present disclosure the catalyst in dehydrofluorinating and
fluorinating the XCF2-CF2-CH3 is selected fiom the group consisting of chromia and fluorinated
chromia.
In yet another embodiment of the present disclosure the- catalyst for dehydrofluorinating the
CF3-CF2-CH3 is selected from the group consisting of alumina, fluorinated alumina and chromia,
In' yet another embodiment of the present disclosure dehydrofluorinating and fluorinating of
CF3-CF2-CH3 and XCF2-CF2-CH3 are performed in an inert atmosphere.
The amount of catalyst used in the process of the present disclosure is in the range of 0.03 to
1.5 moles with respect to tetrafluoroethylene.
The present disclosure provides a method to selectively convert the unwanted isomer XCF2-
CF2-CX2F to XCF2-CF2-CX3 by reacting the mixture of isomers CF3-CF2-CX3 and XCF2-CF2-CX2F
with an aluminum halide AlClxBryFz, wherein x =O to 3, y =O to 3 , z =O to 2 and x+y+z=3. Mixture of
CF3-CF2-CX3 and XCF2-CF2-CX3 may be further used in the process of the present disclosure with or
without separation to produce 2,3,3,3-tetrafluoro propene (HFO-1234yf) in hgh yield.
An embodiment of the present disclosure provides a process for producing 2,3,3,3-tetrafluoro
propene (HFO-1234yf) comprises contacting halogenated fluorocarbon represented by the formula
CF3-CF2-CX3 and optionally XCF2-CF2-CX3 wherein (X = C1, Br or I) with hydrogen in a reaction
zone in the presence of a catalyst comprising a catalytically effective amount of hydrogenation catalyst
.: '
to form CF3CF2CH3(, HFC-245cb) when X = C1 and when XCF2-CF2-CX3i s present,..XCF2-CF2-CH3,
where in X=CI,Br or I. Dehydrofluorination of HFCy245cb by contacting in a reaction zone in the
presence of suitable catalyst or dehydrofluorination and fluorination of XCF2-CF2-CX3 and optionally
HFC-245cb with anhydrous hydrogen fluoride in a reaction zone with suitable catalyst to produce
HFO-1234yf.
The present disclosure also provides a method to separate CF3-CF2-CX3 fiom the mixture of
CF3-CF2-CX3 and XCF2-CF2-CX2F isomers, wherein X=Br,Cl or I. The isomers of this kind normally
will have boiling point difference in the range of one "C of each other. Therefore it is difficult to
separate them by conventional distillation methods. Using the process of the present disclosure it is
possible to separate one of the isomer represented by the formula CF3-CF2-CX3 by selectively reacting
the other isomer represented by the formula XCF2-CF2-CX2F with an aluminum halide of formula
AlClxBryFz, where in x =O to 3, y =O to 3 , z =O to 2 and x+y+z=3 to form XCF2-CF2-CX3, by doing
so the boiling point difference between the halogenated fluorocarbon brought far away and one of the
isomer can be easily separated in pure form by conventional distillation method.
An embodiment of the present disclosure discloses a .process for the preparation of 2,3,3,3-
tetrafluoropropene (HFO-1234yf), comprising: reacting tetrafluoroethylene with a general formula
CC13F at a temperature ranging fiom -15 to 75 "C for a time period of 0.5 to 10 hrs in the presence of a
lewis acid catalyst to obtain a mixture of CF3-CF2-C13( HCFC-2 15 ca) and C1CF2-CF2-CC12F( HCFC-
214 cb); refluxing the mixture as obtained with an aluminium halide having the formula AlCl3, at a
temperature ranging from -20 to 75 "C for'a time period of 1 to 4 hrs to obtain a mixture of CF3-CF2-
CC13 and ClCF2-CF2-CC13; 'separating CF3-CF2-CC13 and ClCF2-CF2-CC13 from the mixture as
obtained; reducing CF3-CF2-CC13 and C1CF2-CF2-CC13 separately with hydrogen in a catalyst bed at a
temperature ranging from 75 - 200 "C to obtain CF3-CF2-CH3 (HFC-245 cb) and XCF2-CF2-CH3
(HCFC-244cc); fluorinating and dehydrofluorinating the C1CF2-CF2-CH3a s obtained in the presence of
a fluorinated chromia as a catalyst at a temperature in the range of 300-450 "C in an inert atmosphere to
obtain 2,3,3,3-tetrafluoro propene; and dehydrofluorinating the CF3-CF2-CH3 as obtained in the
presence of a fluorinated alumina as a catalyst at a temperature in the range of 300 - 450 OC in an inert
atmosphere to obtain 2,3,3,3-tetrafluoro propene. The process of the present disclosure can also be
discussed as follows:
Halogenated fluoro propane represented by the formula CF3-CF2-CX3 and XCF2-CF2-CX2F
(wherein X = C1, Br or I) is used as a starting compound.
The halogenated fluoropropane is obtained by the reaction of tetrafluoroethylene and
halogenatedfluoromethane. Reaction always leads to different isomers. Specific examples of the
1
halogenatedfluoromethanes are trichlorofluoromethane, tribromofluoromethane, triiodofluoromethane
dibromochlorofluoromethane, dichlorobromofluoromethane and the likes.
The addition reaction of the halogenated methane to tetrafluoroethylene carried out by
contacting terafluoroethylene with the halogenated methane with or without a solvent in the presence of
a lewis acid catalyst.
In a specific example if trichlorofluoromethane is used as halo methane, two isomers CF3-CF2-
CC13 (HCFC-2 15cb) and C1F2-CF2-CC12F(H CFC-2 15ca) are obtained as addition products. Lewis acid
catalyst used in the reaction is AlClxBryFz (x+y+z=3), preferable catalyst is aluminium halide (AN3,
X=Cl,Br,F). Most preferable one is aluminium chloro fluoride (AlClxFy.x=3) catalyst.
Addition reaction performed in solvents like HCFC-2 14cb, HCFC-2 15cb, HCFC-2 15ca and
likes. More preferably the reaction carried out in a pool of solvent from the mentioned solvent. Amount
of Lewis acid catalyst used is preferably from 5 to 60 parts by weight of the total amount, and more
preferably fiom about 0.1 to 5 .parts by weight.
Reaction temperature is preferably from -15 to 75 "C. Reaction time for addition is typically
about 0.5 to 10 hrs, and more preferably from 3 to 6 hrs.
The halogenated fluorocarbon represented by the formula C F ~ - C F ~ ~aCndX X~C F2-CF2-CX3,
wherein X=Br, C1 or I are prepared by adopting a simple and novel method fiom the mixture of
halogenated fluorocarbon isomers CF3-CF2-CX3 and XCF2-CF2-CX2F in the presence of AlClxBryFz
where in x =O to 3, y =O to 3 , z =O to 2 and x+y+z=3. Haloalkanes of type CX3F; X = C1, Br or I
always produces isomers of types represented by the formula CF3-CF2-CX3a nd XCF2-CF2-CX2F.
In a specific example, addition of CFC-11 with TFE produces two isomers CF3-CF2-CC13
(HCFC-2 15cb) and C1F2-CF2-CC12F( HCFC-2 15ca), which can be shown schematically as follows:
Lewis acid
CFC- 11 + TFE ---------------------->CF3-CF21-5CcbC)1 +3 C(lHCCFF2C-C-F22 -CC12F(HCFC-2 15ca)
-15 to 75 deg. Celsius
0.5 to 10 hrs
In the present disclosure one of the isomer represented by the formula XCF2-CF2-CX2F
successfully converted in to XCF2-CF2-CX3 by reacting with aluminium halide having the general
formula AlClxBryFz, wherein x =O to 3, y =O to 3 , z =O to 2 and x+y+z=3.
In a specific example, mixture of isomers CF3-CF2-CC13 (HCFC-215cb) and C1F2-CF2-CC12F
(HCFC-2 15ca) reacted with A1C13 to convert one of the unwanted isomer HCFC-215ca into C1F2-CF2-
CC13 (HCFC-2 14cb), which can be shown schematically as follows:
AICI,
HCFC-2 15 ca + HCFC-215 cb -------------->C lCF2 -CF2 -CC1 3 (HCFC-2 14cb) + CF3-CF2-CC13 (HCFC-2 15cb)
-20 to 75 deg Celsius
1 to 4 hrs
Aluminium halide used in the process is preferably AlClxBryFz where in x =O to 3, y =O to 3 , z
=O to 1 and x+y+z=3. Required moles are preferably between 2 to 4 moles.
Reaction temperature is preferably from -20 to 75 C. Reaction time for addition is preferably
from 1 to 4 hrs.
)
The halogenated fluoropropanes produced above having the general formula CF3-CF2-CX3 and
XCF2-CF2-CX3h, ydrodehalogenated in to (HFC-245cb) CF3-CF2-CH3 and XCF2-CF2-CH3 respectively
in the gas phase with hydrogen in the presence of a catalyst.
For example, mixture of CF3-CF2-CC13 (HCFC-215cb) and ClCF2-CF2-CC13 (HCFC-214cb),
hydrodehalogenated with hydrogen in the presence of a catalyst in the gas phase to produce CF3-CF2-
CH3 (HFC-245cb) and C1CF2-CF2-CH3(H CFC-244cc). Hydrodehalogenation can be camed out with or
without separation of CF3-CF2-CX3 and XCF2-CF2-CX3, which can be shown schematically as follows
Pdl AI2o3
HCFC-2 14cb + HCFC-2 15cb +H2 ----------->C F3-CF2-CH3 (HFC-245cb) + ClCF2-CF2-CH3 (HCFC-244 CC)
75 to 200 deg Celsius
Metal catalysts used for the hydrodehalogenation are platinum, palladium, nickel and rhodium;
most preferred ones are platinum and palladium. Preferred catalyst caniers are alumina and activated
carbon and most preferred one is alumina.
The reaction temperature is preferably from 75 to 200 OC to minimize the by products.
Amount of hydrogen with respect to starting material is preferably 5 to 10 moles, excess
amount of hydrogen used to convert all the starting material and intermediates. In the reaction reactants
residence time over the catalyst bed maintained between 20 to 60 secs.
The final product HFO-1234yf (2,3,3,3,-tetrafluoropropene) produced by dehydrofluorination
of CF3-CF2-CH3 (245cb) over a suitable catalyst bed in gas phase, optionally with an inert gas, and
dehydrofluorination and fluorination of XCF2-CF2-CH3 over a suitable catalyst in gas phase, optionally
with anhydrous hydrogen fluoride, and optionally with an inert gas. For example, dehydrofluorination
of CF3-CF2-CH3 (HFC-245cb) and dehydrofluorination and fluorination of ClCF2-CF2-CH3 (HCFC-
244cc) to produce 2,3,3,3-tetrafluoropropene.
Dehydrofluorination and fluorination can be carried out with or without separation of CF3-CF2-
CH3 and XCF2-CF2-CH3a nd preferably with the separation of XCF2-CF2-CH3.
Metal catalysts used for the hydrodehalogenation and fluorination are mainly comprises of
chromia containing metal nickel and zinc; most preferred ones are chromium oxides and fluorinated
chromium oxides.
Fluorination is carried out optionally with anhydrous hydrogen fluoride. If anhydrous hydrogen
fluoride is used, the amount is in the range of 1 to 3 moles, preferably from 1 to 1.5 moles.
Inert gas in the reaction is preferably nitrogen. The reaction temperature is preferably from 300
to 450°C and reactants residence time over the catalyst bed maintained between 20 to 60 secs.
Dehydrofluorination can be camed out without separation of CF3-CF2-CH3 and XCF2-CF2-CH3 and I
I
I
preferably with the separation of CF3-CF2-CH3 (HFC-245cb). Metal catalysts used for the i
hydrodehalogenation mainly comprises of alumina, fluorinated alumina or chromia. Inert gas in the !
i
reaction preferably nitrogen and argon, more preferably nitrogen.
The reaction temperature is preferably from 300 to 450 "C. In the reaction, reactants residence
time over the catalyst bed maintained between 20 to 60 secs.
Final product HFO-1234yf 2,3,3,3-tetrafluoropropene obtained from the above process purified
further to get pure product.
EXAMPLES
The following examples are given by way of illustration of the present disclosure and should not be
construed to limit the scope of present disclosure. It is to be understood that both the foregoing general
description and the following detailed description are exemplary and explanatory only and are intended
to provide further explanation of the subject matter.
Example-1
Preparation of CF3-CFZ-CC13( 2 15cb) and ClCF7-- CF-? -CFC1-2 ( 2 15ca)
A 2 L Hastelloy C autoclave was charged with anhydrous aluminium chloride ( 30g, 0.225
moles), CFC-11 (610 g, 4.4 moles), after which tetrafluoro ethylene (TFE) was fed to the reactor at -80
"C. A total of tetrafluoro ethylene (420g, 4.2 moles) were added to the autoclave and the autoclave
heated to 20 "C and stirred for one hour. The reaction was cooled and the products discharged to get
1018 g of crude product. The same slurry catalyst used for next cycle.
Crude organic analysed in GC, results are given below.
2 15cb 8 1.45%
2 15ca 10.96%
CFC- 1 1 2.08%
Others 5.51%.
Yield with respect to both isomers 94.3 %.
Example2
Conversion of ClCF?-CF7-CFC17 (2 15ca) to ClCF2-CF7-- CC1-7 (2 14cb)
A three neck 250 ml round bottom flask equipped with condenser, stirrer and temperature
sensor, charged with aluminium chloride (12.7gY 0.095mol), and mixture of isomers HCFC-215cb -.
83.01% and HCFC-215ca 11.64% (120g, 0.47mol), and the reaction mixture heated to reflux
temperature (75 "C), and refluxed for one hour. The product was discharged by decanting the
supernatant liquid to give 1 l j g of material, and analysed using gas chromatography.
Gas chromatography analysis shows a neat conversion of HCFC-2 15ca to HCFC-2 14cb.
2 15cb 74.6%
214cb 18.2%
The crude product distilled in a one meter column equipped with reflux divider and condenser, to get
pure HFC-215cb (B.P. 73 "C) and HCFC-214cb (B.P. 114 "C).
Conversion of CICF2-CF?-CFCl? (2 15ca) to CICF2-CF2-CC13 (2 14cb)
A three neck 250 ml round bottom flask equipped with condenser, stirrer and temperature
sensor, charged with aluminium chloride (16.2g, 0.121 mol), and mixture of isomers HCFC-215cb -
82.96 % and HCFC-215ca -14.71 % (176g 0.72 rnol), and the reaction mixture heated to reflux
temperature (75 "C), and refluxed for one hour. The product was discharged by decanting the
supernatant liquid to give 172 g of material, and analysed using gas chromatography.
Gas chromatography analysis shows a neat conversion of HCFC-2 15ca to HCFC-2 14cb.
214cb . 20.8%
. The crude product distilled in a one meter column equipped with reflux divider and condenser, to get
pure HFC-215cb (B.P. 73 "C) and HCFC-214cb (B.P. 114 "C).
Example-4
Preparation of C
In an Inconel tubular gas phase reactor (26mm dia, 450mm length) equipped with an electric
- . furnace was charged with 2% palladium on alumina catalyst (200g). Catalyst calcination performed by
supplying nitrogen (200 cclmin) at 350 "C, activation performed by supplying hydrogen (100 cclmin)
at 250 "C for three hours, and the reactor was allowed to cool at 180 "C.
A mixture of hydrogen (240ml/min) and 215cb (0.55glmin) was fed into the reactor.at 150 "C,
out let gas from the reactor washed with water to remove the acid content, and subsequently collected
in a cold trap and analysed by gas chromatography.
Gas chromatography analysis as fol.lows
245cb 93.5%
235cb 2.9%
As per the analysis conversion of 215cb is 100%. Crude product distilled further to get pure product
. . and the intermediates stream may be recycled.
Exampled
Preparation of C1CF2-CFZ-CH2 (244cc) f r o m -
In an Inconel tubular gas phase reactor (26mm dia, 450mm length) equipped with an electric
furnace was charged with 2% palladium on alumina catalyst (200g). Catalyst calcination performed by
supplying nitrogen (200 cclmin) at 350 "C, activation performed by supplying hydrogen (100 cclmin)
at 250 "C for three hours, and the reactor was allowed to cool at 180 "C.
A mixture of hydrogen (240cclmin) and 214cb (0.65glmin) was fed into the reactor at 180 "C,
out let gas from the reactor washed with water to remove the acid content, and subsequently collected
in a cold trap and analysed by gas chromatography.
Gas chromatography analysis as follows:
244cc 95.0%
245cb 0.4% and intermediates.
As per the analysis conversion of 214cb is 100%. Crude product distilled further to get pure product
and the intermediates stream may be recycled.
Example6
Preuaration of CF1-CF=CF, - (HFO-1234vf) from CF3-CF2-CH3 (245cb)
In an Inconel tubular gas phase reactor (26mm dia, 450mm length) equipped with an electric
furnace was charged with alumina catalyst (130g). Catalyst calcination performed by supplying
nitrogen (200 cclmin) at 350 "C, activation performed by supplying anhydrous hydrogen fluoride
(0.5g/min) along with nitrogen at 350 "C for eight hours, and the reactor was maintained at 350 "C.
A mixture of nitrogen (60cclmin) and 245cb (0.55g/min) was fed into the reactor at 350 "C , out
let gas from the reactor washed with water to remove the acid content, and subsequently collected in a
cold trap and analysed by gas chromatography.
Gas chromatography analysis as follows :
HFO-1234yf 83.77%
245cb 15.41%
As per the analysis conversion of 245cb is 84.6%. Crude product distilled further to get pure
HFO-1234yf, Unreacted 245cb recycled further to get HFO-1234yf.
Example-7
Preparation of CF3-CF=CF, (HFO- 1 2 3 4 - m
In an Inconel tubular gas phase reactor (26mm dia, 450mm length) equipped with an electric
m a c e was charged with chromia catalyst (280g). Catalyst calcination performed by supplying
nitrogen (200 cclmin) at 350 "C, activation performed by supplying anhydrous hydrogen fluoride
(0.5gJmin) along with nitrogen at 350 "C for eight hours, and the reactor was maintained at 350 "C.
A mixture of nitrogen (60cc/min), anhydrous hydrogen fluoride (0.15glmin) and
244cc(0.52g/min) was fed into the reactor at 350 "C , out let gas from the reactor washed with water to
remove the acid content, and subsequently collected in a cold trap and analyzed by gas
chromatography.
Gas chromatography analysis as follows:
HFO-1234yf : 43.2%
244cc : 49.8% and intermediates.
As per the analysis conversion of 244cc is 50.2%. Crude product distilled further to get pure 'HFO-
1234yf, Unreacted 244cc recycled further to get HFO-1234yf.
Although the subject matter has been described in considerable detail with reference to certain
preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the
disclosure should not be limited to the description of the preferred embodiment contained therein.

We Claim:
1. A process for the preparation of 2,3,3,3-tetrafluoro propene (HFO-1234yf), comprising:
i. reacting tetrafluoroethylene with a compound having general formula CX3F,wherein X=Cl,
Br or I, at a temperature in the range of -15 to 75 "C for a time period in the range of 0.5 to
10 hrs in the presence of a lewis acid catalyst to obtain a first mixture of CF3-CF2-CX3 and
XCF2-CF2-CX2F;
ii. refluxing the first mixture with an aluminium halide having the formula AlClxBryFz,
wherein x =O to 3, y =O to 3, z =O to 2 and x+y+z=3, at a temperature in the range of -20 to
75 "C for a time period in the range of 1 to 4 hrs to obtain a second mixture of CF3-CF2-
CX3 and XCF2-CF2-CX3, wherein X= Br, C1 or I;
iii. reducing CF3-CF2-CX3 and XCF2-CF2-CX3 with hydrogen in a catalyst bed at a temperature
in the range of 75 - 200 "C to obtain CF3-CF2-CH3a nd XCF2-CF2-CH3re spectively;
iv. dehydrofluorinating and fluorinating the XCF2-CF2-CH3 as obtained in step (iii), in the
presence of a catalyst at a temperature in the range of 300-450 "C to obtain 2,3,3,3-
tetrafluoro propene; and
v. dehydrofluorinating the CF3-CF2-CH3 as obtained in step (iii), in the presence of a catalyst
at a temperature in the range of 300-450 "C to obtain 2,3,3,3-tetrafluoro propene.
2. The process as claimed in claim 1, wherein the lewis acid is selected fiom the group consisting
of BF3, BC13, BBr3, AlF3, AlC13, A1Br3, FeC13, NiC12, SbFs and SbC15.
3. The process as claimed in claim 1, wherein the lewis acid catalyst is used in an amount in the
range of 0.03 to 1.5 moles with respect to tetrafluoroethylene.
4. The process as claimed in claim 1, wherein in step (ii) the first mixture is reacted with
aluminium halide in a ratio in the range of 3% to 15% weight of aluminium halide with respect
to the weight of the first mixture.
5. The process as claimed in claim 1, wherein the catalyst bed consist of metal catalyst selected
fiom the group consisting of platinum, palladium, nickel and rhodium.
6. The process as claimed in claim 1, wherein the catalyst bed consist of catalyst carriers selected
f?om the group consisting of alumina and activated carbon.
7. The process as claimed in claim 1, wherein CF3-CF2-CX3 and XCF2-CF2-CX3 are separated
from the second mixture.
8. The process as claimed in claim 1, wherein step (iv) and (v) are performed in an inert
atmosphere.
9. The process as claimed in claim 1, wherein the catalyst in step (iv) is selected fiom the group
consisting of chromia and fluorinated chromia.
10. The process as claimed in claim 1, wherein the catalyst in step (v) is selected from the group
consisting of alumina, fluorinated alumina and chromia,