Note: Descriptions are shown in the official language in which they were submitted.
CA 02238508 1998-05-26
WO 97/19903 PCT/GB9~ 29C~
PRODIJCTION OF CHLORO-2,2,2-TRIFLUOROETHANE
J 5 This invention relates to the production of chloro-2,2,2-trifluoroethane, HCFC 133a, from
trichloroethylene and particularly to a process for the co-production of 1,1,1,2-tetrafluoro-
ethane and chloro-2,2,2-trifluoroethane from trichloroethylene.A particular embodiment of
the invention relates to ~ccç~ g chloro-2,2,2-trifluoroethane as a co-product from the
production of 1,1,1,2-tetrafluoroethane by the two-step reaction of (i) trichloroethylene
with hydrogen fllloride to form chloro-2,2,2-trifluoroethane and (ii) chloro-2,2,2-trifluoro-
ethane with hydrogen fl-~onde to produce 1,1,1,2-tetrafiuo,ueLha~le with recycle of
chloro-2,2,2-trifluoroethane to step (i).
The two-step reaction of trichloroethylene with hydrogen fluoride in the vapour phase in the
presence of a flllr)rin~tioTl catalyst such as ~h~u~l~ia o:r based on chromia to produce
chloro-2,2,2-tri_uoroethane and 1,1,1,2-tetrafluo,u~Ll,alle is well known and is the basis of
a number of cfs.. e~c,;al plants for the pro~lllction of 1,1,1,2-tetrafluoroethane. The reaction
may be camed out in a single reaction zone or the two steps of the reaction may be carried
out in s~ le reaction zones. The reaction produces a number of by-products, notably
20 hydrogen f.hlnrirle and various sa~ a~ed and u~lsaLu~ ~L~d chlorofluûro(hydro)carbons and
the reaction of chloro-2,2,2-trifluoroethane to I,1,1,2-tetrafluoroethane is equilibrium
limited so that the reslllting 1,1,1,2-tetrafluoroethane product stream usually co---ylises less
than 20% by weight of 1,1,1,2-tetrafluoroethane and CQ~ major plUpUlLions of
hydrogen chlc Tid~, unreacted chloro-2,2,2-trifluoroethane and hydrogen fluoride (which is
25 commnnly used in a large excess).
The 1,1,1,2-tetrafluoroethane product stream is normally ~ul~jec~ed to several tre,~tm~nt~,
incl-lAing Ai~till~tion~7 to recover hydrogen chloride and esse.nti~lly pure
1,1,1,2-tetrafluoroethane and provide a crude recycle stream co~ ishlg mainly
30 chlorû-2,2,2-trifluoroethane and hydrogen fluoride but inrlllA;n~ various
chlorofluoro(hydro)carbon by-products. Hitherto no attempt has been made to recover
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WO 97/19903 PCT/GBg6/02909
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~c~P.nti~lly pure chloro-2,2,2-trifluoroethane from the 1,1,1,2-tetrafluoroethane product
stream as a co-product ofthe 1,1,1,2-tetrafluoroethane production process.
The present invention resides in a process for the production of chloro-2,272-trifluoroethane
S whereinthe 1,1,1,2-tetrafiuoroethaneproductstreamco~
chloro-2,2,2-trifluoroethane and hydrogen flllori(lç ob~&il~d by hy~llon..crin~tion of
trichloroethylene is treated to recover esc~nti~tly pure chloro-2,2,2-trifiuoroethane as well
as ~c~Pnti~lly pure 1,1,1,2-tetrafluoroethane.
10 Accor.lillg to the present invention there is provided a process for the production of
chloro-2,2,2-trifluoroethane as a co-product ofthe production of 1,1,1,2-tetrafluoroethane
by hydrofluorination of trichloroethylene which co~ ises (i) treating the
1,1,1,2-tetrafluoroethane product stream cu,.l~;..;..g chloro-2,2,2-trifluoroethane and
hydrogen fluoride to form a mixture of 1,1,1,2-tetr~fll-oroethane and
15 chloro-2,2,2-trifluoroethane and (ii) dictilling said ll~ib~Lul~ to sepal~Le çR~nti~lly pure
chloro-2,2,2-trifluoroethane from the mixture.
The ~iict~ tion carried out in step (ii) may be a single-stage ~ till~tion to s~ Le
chloro-2,2,2-trifluolot;Lll~le directly from the mixture or it may be a two-stage or multi-
20 stage tlictill~tio~ to sep~Le the chloro-2,2,2-trifluoroethane. In the single stage ~listill~tinn~
the mixture of 1,1,1,2-tetrafiuoroethane and chloro-2,2,2-trifluoroethane formed in step (i~
is fed into a ~i~till~tinn column and chloro-2,2,2-trifluoroethane is WilLll~wll directly from
the column as a bottom fraction. It is to be understood that whilst this stage is described as
a single-stage ~l;ctill~tion it may be carried out in more than one rli~till~fion cc l~lmn
The r~m~inf~er ofthe 1,1,1,2-tetrafluoroeth~ne product stream, cle~le~ in
chloro-2,2,2-trifluoroethane, may be withdrawn as a top stream from the column and passed
to further processing to recover the l, 1,1,2-tetrafluûroethane, for ~Y~mple by feeding the
stream back into the 1,1,1,2-tetrafluoroethane purifi~ ti-n train ofthe production plant. If
30 desired, the top stream from the fli~till~tion column may be recycled to the ~1istill~tinn
column to sepcuale a further amount of chloro-2,2,2-trifLuoroethane before the stream is
passed to further processing to sep~ale the 1,1,1,2-tetrafluoro~lalle.
=E
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WO 97/19903 PCT/GBg6/02909
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The mixture of 1,1,1,2-tetrarduoroethane and chloro-2,2,2-trifluoroethane formed in step (i)
is escçnt~ y free from hydrogen fluoride and hydrogen chloride but will usually contain
minor ~mmlntC of chlorofluorocaron by-products. In the single-stage distillation in step (ii),
these by-products remain in the column and are withdrawn with the
5 1,1,1,2-tetrafluoroethane stream. ~Iowever in an embodiment ofthe single-stage ~lictill~tion~
the by-products of boiling point interrnediate those of 1,1,1,2-tetrafluoroethane and
chloro-2,2,2-trifluoroeth~ne may be wiLlldl,lwll as a side stream from the coll-mn
The ~lictill~fion in step (ii) may be a two-stage or a rnulti-stage OyGI~LiOII and a ~le~ll~d
10 ~ict~ n is a two-stage tlictill~tinn in which the first stage (iia) co.~ ises riictillin~ the
mixture of 1,1,1,2-tetrafluoroethane and chloro-2,2,2-trifluoroethane formed in step (i) to
separate çssPnti~lly pure 1,1,1,2-tetrafluoroethane as a top fraction from the column and
form a second nli~Lu~ of 1,1,1,2-tetrafluoroethane and chloro-2,2,2-trifluoroethane and the
second stage (iib) cc~ lises ~ictillin~ said second mixture to s~palale ~cse~ti~lly pure
15 chloro-2,2,2-trifluoroethane as a bottom fraction and form a third mixture of 1,1,1,2-tetrafiuoroethane and chloro-2,2,2-trifluoroethane.
This ~ d embodiment thus provides a process for the pro~ ctio~ of
chloro-2,2,2-trifluoroethane as a co-product ofthe prodtlction of 1,1,1,2-tetrafluoroethane
20 by hydlon. lorin~tion of trichloroethy1ene which coln~-ises (i) treating the
1,1,1,2-tetrafluoroethane product sream cc~ chloro-2,2,2-trifluoroethane andhydrogen flll~ ncl~ to form a first mixture of 1,1,1,2-tetrafluoroethane and
chloro-2,2,2-trifluoroethane, (iia) ~i~tiliin~ said first. mixture to separate ç~çnti~lly pure
1,1,1,2-tetrafluolot;Ll~ne and fonn a second mixturé of 1,1,1,2-tetrafiuoroethane and
25 chloro-2,2,2-trifluoroethane and (iib) ~ illin~ said second mixture to separate ç~s~nti~lly
pure chloro-2,2,2-trifluoroethane and form a third mixture of 1,1,1,2-tetrafiuoroethane and
chloro-2,2,2-trifluoroethane.
The third ll~i~lult; of 1,1,1,2-tetrafluoroethane and chioro-2,2,2-trifluoroethane, obtained in
30 step (iia), can be recycled to any step ofthe 1,1,1,2-tetrafluoroethane production process or
to the crude 1,1,1,2-tetrafluoroethane product stre,arn prior to step (i) ofthe process
acc.Jldlng to the illvt;ll~loll.
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WO 97/19903 PCT/GB96/02909
The crude 1,1,1,2-tetrafluoroeLllane product stream fed to step (i) ofthe process plcft;l~ly
is ecc~nt~ y free from hydrogen chloride. The process ofthe invention thus l"t r~-dbly
incl~ldes an additional step of treating the crude product stream, for example by distillation,
5 to separate hydrogen chloride prior to tr~Rtm~nt according to step (i).
In a typical 1,1,1,2-tetrafluoroethane production process, a ll~Lul c of
1,1,1,2-tetrafiuoroethane, chloro-2,2,2-trifluoroethane and hydrogen fl~lori~le may be
crudely s~a-~Led from the 1,1,1,2-tetraf~uoroethane product stream, for in~ ce as the top
10 stream from a di~t~ tion col-lmn from a mixture co...l.ri~;..g mainly
chloro-2,2,2-trifluoroethane and hydrogen fluoride, for e~ll~le a liquid bottom stream
and/or a gaseous side stream from the ~i~till~tion cloumn. The
chloro-2,2,2-trifluoroethane/hydrogen fluoride mixture is preferably recycled to the
1,1,1,2-tetrafluoroethane production process, in the case of a two step process either to the
15 chloro-2,2,2-trifluoroethane COllv~l alOll step or to the trichloroethylene conversion step.
Dictill~tion ofthe 1,1,1,2-tetrafluoroethane product strearn, after removal of l~ydlo~,~..-
chlorid~ to se~Le a mixture of 1,1,1,2-tetra_uoroethane and hydrogen fluoride from a
recycle stream colll~ ing mainly chloro-2,2,2-trifluoroethane and hydrogen fl-loride is a
20 conve~ltinn~l step in the production of 1,1,1,2-tetrafluoroethane. The rii~t~ tic)n is fairly
crude so that in the conventio~l di~til~tion the separated mixture of
1,1,1,2-tetrafluoroethane and hydrogen fluoride may contain chloro-2,2,2-trifluoroethane
which is removed at a later stage and recycled to the 1,1,1,2-tetrafluoroethane production
process. However, the collv~ n~ till~tion is opelaL~d under con~litioni (Lelll~elal~lle
25 and pres~ule) ~le~ ned to ...;i .;. . .;.~ the car~y over of chloro-2,2,2-t~ifluoroethane with the
1,1,1,2-tetrafluoroethane and hydlog~ fl-~oritle so as to reduce the burden on the
subsequent separation step. In contrast the Ll~ accul~lillg to step (i) of the invention is
operated under con~lition~ for ~ ,le ~i~till~tion under higher temperature and/or lower
pl e~ e, wherby an a~p- t;cial)le amount of chloro-2,2,2-trifluoroethane is present in the
30 st;p&laLed mixture so as to provide a source of chloro-2,2,2-trifiuoroethane for recovery as
a co-product of the 1,1,1,2-tetrafiuoroethane production process.
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WO 97/19903 PCT/GI~ 909
The amount of chloro-2,2,2-trifiuoroethane in the mixture separated in step (i) and hence
the amount of chloro-2,2,2-trifluoroethane ~cc~c~ble as a co-product is ~lepentl~nt upon
and therefor controlled by the opGl~Lillg c~ n-lition~ ofthe flictill~tinn col--mn It is a simple
matter for the operator to select OpGl~illg con~1itione a~ro~ Le to any particular
5 requ" t;l~ L for chloro-2,2,2-trifiuoroet~n~ as a co-product. As a guide, the column will
usually be opc,.~Led at a p,es.,ul e in the range of about 10 barg to 20 barg.
The mixture of 1,1,1,2-tetrafluoroethane, chloro-2.,2,2-trifiuoroethane and hydrogen
fl--ori~e st:palaLGd from the product stream is then treated to remove the hydrogen fluoride
and form a ll~t~lG of 1,1,1,2-tetrafluoroethane and chloro-2,2,2-trifiuoroethane.
The removal of hydrogen fl~ n(le may be ~ffected by any suitable techr~ique, for ~Y~mllte by
s.;lubbing the mixture with water or an alkaline sollltion
The process will usually inc}ude an ~r~ tion~l tre~tm~nt between hydrogen fluoride removal
15 in step (i) and ~iet~ ticn in step (ii3 to recover e~Pnti~lly pure chloro-2,2,2-trifluoroethane.
As ~isc~ece~l helh~berulG, step (i) usually colll~lises crude dietill~tinn ofthe1,1,1,2-tetrafluoroethane product stream to sep~Lt; a mixture of 1,1,1,2-tetrafluoroethane,
chloro-2,2,2-trifluoroethane and hydrogen flllori(le. However, the 1,1,1,2-tetrafluoroethane
product stream usually c~ ;"e several other chlorofluoro(hydro~carbon c~slllpol.c.-l~ and
20 these will divide on the basis of "lights" and "heavies" beL~een the ll~Lures s~pal~Led in
step (i). The mixture obtained in step (i) may contain one or more of these "lights"
coll.~on~lL~ and is usually treated, for ~ .lt by ~lictill~tio~ to remove these components
prior to feeding to step (ii). The "lights" cc,lll~onellL~ lt;llloved in this ~ are ge~ lly
lmc~it~hle for recycle to the 1,1,1,2-tetrafluoroethane pro-lnction process and so may be
25 vented and disposed of for ~ ,plc in a thermal oxidiser. The op~raLing contliti~c for
"ligh~s"colll~ol1ellL., separation are known and/or readily d5;lf~"..;nf~d but as a guide the
con-ihion~ will usually be a column pressure offrom about 10 barg to 20 barg.
F..c~nti~lly pure chloro-2,2,2-trtifluoroethane is sepal~LLed in step ~ii) of the process. In the
30 pl~,r~lled t~vo-stage rlictill~tion~ 1,1,1,2-tetrafiuoroethane is se~al~Led by ~ictill~ti~ n in step
(iia) from a second mi~cture of chloro-2,2,2-trifluoroethane and a small amount of
1,1,1,2-tetrafluoroethane, the latter mixture then being distilled in step (iib) to sepal~le
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W O 97/19903 PCT/G B96/02909
-- 6 --
~qnti~lly pure chloro-2,2,2-trifiuoloe11~e for leCOve.y. The o~c~ g con.l;l;nl-~ for the
tlicttllsltion coll~mn~ are readily de~ ned by the opel~Lor but as a guide the con~itionc will
usually be a column pl ês~ul'e of from about 1 barg to 15 barg, say 5 to 12 barg in step (iia)
and a column pl'e5~ul è of about I barg to 10 barg in step (iib). As described hel eil,be~ e,
S any residual (third) mixture of 1,1,1,2-tetrafluoroethane and chloro-2,2,2-trifiuoroethane
from step (iib) may be recycled for further lle~ to recover the product values, for
I - S~ plF. by recycle to the 1,1,1,2-tetrafluoroethane product stream from the
1,1,1,2-tetrafluoroeth~n~ prorl~lcti~n process or to any step ofthe product sep~r~tion
tl~ lortoanystepofthe1,1,1,2-productionprocess.
The 1,1,1,2-tetrafluoroethane product stream may be the product stream from any process
for the pro~ ctinll of 1,1,1,2-tetrafluoroethane by hydrofl--orin~tion of trichloroethylene and
the invention is not restrictecl to any particular process for producing
1,1,1,2-tetrafluoroethane from trichloroethylene.
The process acco,-li,lg to the invention may be operated as a batch process ~lthr~ h we
prefer ccntin~lo~ls operation. In the two-sage ~;ctill~tion procedure we prefer contim-ous
operation at least up to and inrJl--lin~ step (iia). Step ~iib) may be inrJll(led in the cnntin
operation but if desired the second mixture of chloro-2,2,2-trifluoroethane and 1, 1,1,2-
20 tetrailuo,otlLalle ~om step (iia) may be stockpiled and treated separately as a batchwise
operation in step ~iib).
2~
