Note: Descriptions are shown in the official language in which they were submitted.
l ~ ~ S ll~ ),2
t i n r~ r (~ t, ~ t:~ .I r) l r) r' r'` '; ':; r ~:~ l' c; c p .l r' ~l ~ i r~ -J
i~J(iirle (Irl(l it~ r~ r?o~ (lr~ Fl(~ r (.~ ylc~ti(1rl pro-
d(Jcts a(elic acicl, aceti( al1l1yrlridr- or ethyli(lr?r1e di-
acrt,ilte wlli(1l arr oht.lioc(l 011 sllt),jc( l,.in(J dilllethyletller,
1ll(~tl1y1 act~ f~ llllo~ (.1rl)r1lly]~1t:iol-l Ir~ctlor
i(l t~lr? I)lr~ rl(r? "r ., t~lt.;)ly~ (?rll~li(lirl(l iorlirle, Irlllr?rr?-
in thc tol.)1 iodirlc colltalllinalill(J Ihe r.lrt)ol1y1atio
¦ ~ ~' ( ) ( I l l C ~ ( r ! ( l t() ~ rr)~ ,r, 1l~]l, 2 n ~
iodinr? by trci1tirlg the CaTI)ooy] al ion pr odllcts at tempr~-
~at~reci of 50 - 20n~c wit~ r(lrlerl 1(l t~le preserlce Or
at least one nnhle metal belon(Jin~1 to clroup VIII oF tl1e
F'eriodic System o~' t,lle elrmel-)l,s, ar)d sel)arat.irlg tllen
r 1~ 0111 t ~ ) P c ~ t ;l ] ~ r~ t .
A process oF this l<incl has a:LIea(IY her?r) dr?scrit)(?rl
io Gern)r1(1 Sp(?ciFicatioo I)E-A-33 31 548 In thir; prr)_
cess-, it hac; llJrnr?(i out ~h.1t 11)( c<ll.)1~tic pelforlnar)re
sut)s:i(:les rather ral)i(1ly r.o tl)at it. is in\larial)iy necc?s-
sary For the processincl tempcraturc ar)d/or catalyst
ctual-1tity to be incrr?asecl so as to acl1ieve a satisfacto-
rv iodine separatinrl eFfect. II)(?se a1e sLeps which en-
t ail an undesi-rclble forrnat:iol1 of by-l)ro(illctc-i~ e.y.
acetai(lehyde, acetic acid allrJ et)1yli(i(?l1e diacetclte clur-
iny the 1-12-treatlllerlt acr?tir.~ anllydride corltal))irlated With
iodirle is subjected to. rhe prrC.rrlt inver1tior) now pro-
2r~ \/irie'~ ~3 procec;s Wil i cl) ~!I)ab] (?S tl1r (~ t ~I(J(` ~Iss(l-
Ciat.e(l IAJith the prO(`I' .'' deS(`l'ih('d ill [.el'l(nll) Spr(`if ica-
tion DE-A-33 31 548 to be set aside. Io this er)d, the
invention ur1expectedly providl:?s For ~just a minor pro-
12~g~55
23343.812
portion of carbon monoxide to be added to the hydrogen/noble
metal-reaction system; as the targeted result, the Eormation of
by-products e.g. acetaldehyde, acetic acid and ethylidene
diacetate is strongly reduced and the efficiency of the
catalyst is considerably prolonged. In this process, the
iodine - regardless of whether bound or elementary - is readily
removed from the carboylation products to be purified.
The invention provides a process for separating iodine and
its compounds from the carbonylation products, acetic acid,
acetic anhydride or ethylidene diacetate, obtained on
subjecting dimethylether, methyl acetate or methanol to a
carbonylation reaction, wherein the total iodine contaminating
the carbonylation products is reduced to a content of less than
ppb iodine, which process comprises treating the carbonyl-
ation products at a temperature of 50 - 200 C and over a
period of 0.2 - 6 hours with a hydrogen/ carbon monoxide
mixture in the presence of at least one noble metal belonging
to group VIII of the Periodic System of the elements as a
catalyst, wherein 0.001 - 1 mol each of hydrogen and carbon
monoxide is used per mol carbonylation product, and separating
the carbonylation products from the catalyst.
Eurther prefered features of this invention which are
substantially the same as those described in German Spec-
ification DE-A-33 31 548 provide:
a) for carbonylation products containing less than lO0 ppm
total iodine to be used;
b) for the noble metal used to be finely distributed on a
carrier;
c) for the corbonylation products to be treated over a period
of 0.2 - 6 hours;
~i~796S5
23343-812
d) .Eor the carhonyl.ation products to be treated under a
pressure oE 0.5 - lO bars;
e) for 0.00] - l mass % noble metal, hased on the
carbonylation products, to be used as the catalyst.
The fixation of the iodine-containing contaminants should
conveniently be e~fected by adding the noble metal, which
should preferably be finely distributed on a carrier,
~ .~, ~,
lX796~;5
st.clr~l of Ille erll ire r;lrhrlny~ Jrl prr)trsr;. Iodi.rlt.-ror~tairl-
irl~i r~ r~ f ixr~ to ~r~ llrl~)lr~ r~t,ll o~ c~lrritl .~re
r~ f ~ y s r~ l r ~) ~ r~ d l:) y r f~ lll r) ~/ i r l fl t. ll t~ t~ . rl l y ~; ~ f r o lrl t tl e
r~ l)UI i f i('rl produrt hy fill,clirlt~ )el)rll(lillrl on the (luarltity of
iodirle fixrci l,o l,llr n()l!:l(? mf-~tcll l,hr lal-l,er is recycled for
r r - u s e o r r e p l a r r d l- v f r e ~; h r a t a l v s t. .
Ner(llec;s tr) S.ly, il is alr;o p-)ssit)le lor the nob:le
m(?l.al catalyst all(l hyrlTr)(~l(rl/r;,ll)r~l~ mr~r~rlxi-lr-mi~l,llrr le-
IU cesiarv l-)r el,imirlat,.i.rl(l I.hr io(lill(-corll;lillirlrl cont,amirlrlrlts
to be a~lclr,cl ahea(J nF thc~ last Ol~ nrxt t,o last puri fication
stage in wtl:icll the carl)ollyli~lir)rl prorluct, is f'rr,ed ~rom
high-l)oiling resirlLIe or low-l)(lilincl f~rlcl,iorls.
ille prr)crss nr t.his in\/rrltirlll pellnils t.he tot,a]. ioclirle
cnntrrlt in t.llr treateci cnrl)c)nylrlli(lll pl`O(ilJ(` t t O hr r ecluct?d
hrynll(l l,llc~ limit, of rlet,((l,i(ll-l ol' Irss tharl 5 pl)l) (= 5 parls
hy wr.?irlht iodine per onc~ 1)ill inn (109) parts hy weight
carbl:)rlylatiorl product).
Ihe catalyst preparat..ion does not f'orm pclrt of ttle in-
2(1 vellt.io(l. It is howe\/r?r prt.~ferat)lt! lo ar)ply tlle nobl.e rnetalto the crlrrier in the form of' VeTy f`,inely di,vicied an(i cata-
lytically act.ive mrlterial by init.ially imprerJnating the
carr.ier selected witl- a noble rnr~,al .salt, solution and then
treatirlg it, wi.th an amlllc)r)iacal tlydrazi.rle solution. In this
Z5 way very finely ciivideci not)le mrtal is appli,ed to the
carrier; after wasllinrJ until nel.ltral arld clryillg, the cat.a-
.l,yst is ready for ucie. It: is also possible for the noble
metal to be set, free hy rerillcillc) treat,l))erlt. wit.h hydrngen at
elevated temperature.
:3[~ The useful carriers rnr the noble met.al comprise e.ri.
12~5~
5ilit'ic aC.i(J antl alumilllJm nxi(lr?. Tlle p.lrticlr sizr oF the
carrier rnay vary within the wide limits oF 0.01 - 10 mm,
cleperlding orl whettler the catalyst i9 usetJ e.g as a fixed
bed or fluiclized btd cata]yst. Ihe r-,ame is true concerning
S its inner surFace area (deterrninecl by the BET-method) which
may vary within the range 1 - 700 m /y. The noble metal
concentration on the cr-)rrier rnay also vary within wide
limits, but should preFerably be within the range 0.5 - 5
mass O. rhe carbonylatiorl product should suitably be sepa-
rated from the noble metal catalyst by filtering.
Pure hydrogen and pure carbon monoxide shouldpreferably be used, but hydrogen and carbon monoxide con-
tainlng e.g. nitrogen, argon and further inert components
can also be employed.
The useFul noble metals include ruthenium, osmium,
iridium, preferably however rhodium, palladium, platinum.
It is possible for the present process to be carried
out continuously or discontinuously.
The total iodine is determined analytically by an
iodine-catalyzed reaction between arsenic and cerium ions
with photometric final determination oF cerium.
Example 1
200 9 of a carbonylation product of acetic acid (19.1
mass 0)~ acetic anhydride (80.7 mass O) and ethylidene di-
acetate (0.2 mass ~O) contaminated with 2 ppm total iodinewas admixed with 0.15 9 palladium finely distributed on 10
9 SiO2 (particle size = 0.01 - 0.2 mm, BET-surface area =
350 m /9 and contacted with 8 l/h of a mixture of 50 vol.,O
hydrogen and 50 vol.,O carbon monoxide at 120C. After a
1279655
contact timr--3 of 5 hol.)rs the supply of thr. hydrogen/carbon
monoxidc-mixtorr- was arrested the rarbonylclt;ion product was
f:iltered and an/llyzed A total lodi.ne vallle of 'less -than 5
ppb corresponding to an i.od:ine separat;i.oll of rnore than 99.8
% was determined. Gas-chromatographic (GC) analysis indicat-
ed that the product consisted of 19.15 mass % acetic acid
80.6 mass ~ acetic anhydride and 0.25 mass % ethylidene di-
acetate; in other words -the carbonylation product treated as
described hereinabove had a composltion which scarcely dif-
fered froln tha-t of the untreated product. Only 0.1 % acetic
anhydride was found to have been lost.
Example 2
Ihe Pd-cat.llyst usc(J in l-xr)lllplr 1. was hrr)ugtlt into con-
tact over a period of 200 hours wit;ll altogetller 8 kg carbony-
lati.on prodoct composed of 19.1 mass ~ acetic acid 80.7 mass
llo aceti.c anhydride and 0.2 mass ' ethylidene diacetate con-
taminated with 2 ppm total iodine and also contacted with
8 l/h of a gas mixture of 50 vol. ' hydrogen and 50 vol. %
carbon monoxide at l20C. The ca:rbonylation product so treated
and filtered was analyzed after 10n and 200 hours contact
;:ime respectively. 'I'he total iodine valuesfoulld were in each
case less than 5 ppb corresponding to all iodi~ separation
of more than 99.8 %. Ihe composition of the product was de-
termined gas-chromatographically; it was 19.15 mass % acetic
acid 80.6 mass % aceticanhydride and 0.25 ma.ss % ethylldene
diacetate which remairlr-d constant over the entire contact
period.
Example 3 (comparative Example)
200 9 of a carbonylation mixture of acetic acid (19.1
~27965S
mass %), acetic anhydride (8r).7 mass ,~) and ethyl:iclerle cli-
acetate (().2 mass ~/0) contaminatecl wlth 2 ppm total iodine
was admixed with 0.15 9 pa:l:ladium finely clistributed on 10
g SiO2 (particle size = 0.()l - 0.2 mm, BFT-surface area =
350 m7/g), arld corltacterl wi~;h 4 ~/h hytlrogerl at 120"C. After
a contact prriorJ of 5 hoors, the sopply of hydrogen was
arrested, the carhorly]atlorl product was filtered and ana-
lyzed. A tolal ioclirle value nf less thr)ll 5 ppb, correspond-
ing to t;he ser)arltinll of n~ore thrlrl ~'3.8 1". iodine, was cle-
t;ermirled. Ihe product was analyzrd gas-chromatographically
and foond to contain 20.() mass ,~, acetic acid, 77.7 mass ~'~
acetic anhydride and 2.3 mass % ethylidene diacetate, i.e.
less acetic anhydride and more acetic acid and ethylidene
diacetate than the untreated product of which the composi-
tion was found to have been modified. 3.0 % acetic anhydride
was found to have been lost after the contact period.
Example 4 (comparative Example)
The Pd-cata]yst of Examp~e 3 was brougllt into contact
over 200 hours with altogether 8 ky of a carbonylation pro-
duct containing 19.1 rnass % acetic acid, 80.70 mass %
acetic anhydride and 0.2 mass % ethylidene diacetate, con-
taminated with 2 ppm total iodine, and also contacted with
4 l/h hydrogen at 120C. Ihe carbonylation product so treated
and filtered was analyzed after 100 and 200 hours contact
tirne, respectively. Already after 100 hours, the residual
iodine content was reduced to 0.4 ppm only corresponding to
an iodine separation of B0 %. To improve the iodine separa-
tion, the temperature inside -the reactor was increased to
130C, after 100 hours. This permitted the iodine content in
-~Z79~
the reaction prnduct to be reducrrd to 7() ppb, corresponding
to an iodine separation of 96.5 %. After a furt;her 100 hours
contact time (total contact period = 200 hours), the ex-
periment was terminated and the filtered product analyzed.
After that time, it was melely possible to reduce the io
dine conterlt fronl 2 ppm to 0.3 !:)prn, corresponding to an
indine separat:ion of 85 ~'u. Gas-chrnmatogIapl-lic analysis
indicated a distinct change in the composit;ion of the car-
bonylation procluct used. It contained 20.5 mass % acetic
acid, 76.0 mass % acetic anhydride, 3.5 mass % ethylidene
diacetate and 600 ppm acetaldehyde.4.7 %anllydride, based on
t;he feed mate~rial, was found to have been lost.
Example 5
200 9 acetic anhydride contaminated with 0.6 ppm to-tal
iodine was admixed with 0.15 9 palladiurn ~inely distributed
on 10 9 silica gel (particle size = 0.01 - 0.2 mm, BET-
surface area = 580 m2/g)and contacted with 10 l/h of a gas
mixture of 95 vol.% hydrogen and 5 vol. % carbon monoxide
at 100C. After a contact period of 3 hours, the acetic
anhydride was separated from the catalyst by filtering and
analyzed. An iodine value of less than 5 ppb, corresponding
to an iodine separation of more than 99.2 %, was determined.
The acetic anhydride was analyzed gas-chromatographically
but could not be found to contain a by-product, such as
ethylidene diacetate, for example.
