Note: Descriptions are shown in the official language in which they were submitted.
lZS8469 HOE 84/H 021
This invention relates to a process for the joint manu-
facture of carboxylic acids, carboxylic anhydrides and, if
desired, carboxylic acid esters, especially acetic acid,
acetic anhydride and optionally methyl acetate.
Acetic acid and acetic anhydride belong to the most im-
portant aliphatic intermediates, and are predominantly used for
making vinyl acetate or cellulose acetate.
Heretofore, acetic acid has almost exclusively been
made by oxidizing acetaldehyde, alkanes or alkenes, but pro-
cesses for making acetic acid by subjecting methanol to car-
bonylation have recently been galning increasing interest.
German Specification DE 17 67 151 C3, for example, describes
a process for making carboxylic acids andtor their esters by
subjecting a saturated aliphatic alcohol having from 1 to 20
carbon atoms or a halogenated derivative or ester or ether
derivative thereof, or phenol to a catalytic conversion re-
action, the feed materials aForesaid being reacted with car-
bon monoxide under a CO-partial pressure of 0.34 to 207 bar
either in liquid phase at 100 to 240C or in gas phase at
200 to 400C in the presence of a rhodium compound and of
bromine, iodine or a compound of these halogenes and also in
the presence of water, in the event of a halogenated deriva-
tive, ester or ether derivative of an alcohol being used.
Heretofore, acetic anhydride has predominantly been made
either by reacting acetic acid with a ketene or by subject-
ing acetaldehyde to a modified oxidation. More recent routes
- have been described in German Specification DE-OS 24 41 502,
wherein a carboxylate ester or hydrocarbon ether is reacted
with an acyl iodide or bromide under practically anhydrous
conditions. The acyl halide is prepared by subjecting an
lZ58469
alkyl halide to carbonylation in the presence of a catalyst
system formed of a nob.le metal belonging to group VIII of
the Periodic System and, optionally, a promQter selected
from groups Ia, IIa, IIIa, IVb, VIb, non-noble metals of
group VIII, and metals of the lanthanides and actinides of
the Periodic System.
German Specification DE 24 5û 965 C2 describes a pro-
ces.s For making acetic anhydride by reacting methyl acetate
or a methyl acetate/dimethylether-mixture with carbon mon-
oxide under pressures of l to 500 bar and at temperaturesof 50 to 250C in the absence of significant proportions of
water and in the presence of catalysts containing noble me-
tals belonging to the 8th subgroup of the Periodic System or
their compounds, iodine and/or iodine compounds and
optionally carbonyl-yielding metals, the reaction being ef-
fected in the presence of catalysts which additionally con-
tain an alkyl or aryl phosphine and/or an organic nitrogen
compound, and optionally in the presence of 5 to 50 volume ~O
hydrogen. The feed materials which are preferentially used
are methyl acetate/methanol-mixtures containing 18 to 20 ~O
methanol.
A further process for the joint manuFacture of acetic
acid and acetic anhydride has been described in ~uropean
Specification EP 00 87 869 Al, wherein a carboxylic acid
ester or ether, water and optionally an alcohol are reacted
with carbon monoxide in the presence of a catalyst consist-
ing of a noble metal belonging to group VIII of the Periodic
System, a bromine or iodine promoter, and a copromoter form-
ed of a Lewis base or a non-noble metal, to give a mixture
of carboxylic acid and carboxylic anhydride, the feed
~2~i8469
mixture containing at least 5.5 weight O water. As regards
the total quantity of water and alcohol, it is not allowable
for it to exceed 85 O oF the stoichiometric quantity of
ester and ether.
Reaction mixtures such as those just described which
in addition to acetic acid contain reactive iodine compounds
and also water have, however, h.igh corrosiveness for most
materials used in industry, including Hastelloy stainless
steels, so that it is invariably necessary for these mate-
rials to be replaced by expens.i\/e substitutes, e.g. tanta-
lum.
It is possible for this dlsadvantage to be set aside by
using an anhydrous mixture of dimethylether and methanol
readily available in sufficient quantities from substantial-
- ly all methanol producers. As has unexpectedly been found,
the reaction mixture has con~sidsrably less cnrroslvenes.s in a
those cases in which the reaction is effected under anhy-
drous conditions. In this case the aCt.iVi.t.Y nf the catalyst re-
lative to the entirety of products is at least preserved or
even improved, compared with operation in the presence of
water. Besides the possibility of adapting the carboxylic
acid/carboxylic anhydride-product ratio to commercial requi-
rementS,the present process provides for the corresponding
carboxylic acid ester to be made as a further commercial
product.
The present invention provides more particularly a
process for the joint manufacture of carboxylic acids, carb-
oxylic anhydrides and, if desired, carboxylic acid esters of
}n the general formulae RCOOH, RCOOCOR and RCOOR, respectively,
lZS84~i9
in which R each time stands for one and the same alkyl radi-
cal having from 1 to 4 carbon atoms, which comprises: react-
ins at temperatures of 50 to 250C and under pressures of D.1
to 120 bars, a dialkyl ether of the general formula ROR with
an alcohol of the general formula ROH in a molar ratio of 9 :
.
1 to 1 : 9 under anhydrous conditions, with carbon monoxide
and, if desired, hydrogen in -the presence of a catalyst sy-
.stem consisting of carbonyl complexes of noble metals be-
longing to group VIII of the Periodic System; an alkali me-
tal iodide, organophosphonium iodide or organoammonium iodi-
de; an alkyl iodide of the general formula RI; and, if desi-
; red, compounds of carbonyl-yielding non-noble metals belong-
ing to groups IV, V, VI, VII or VIII of the Periodic system.
In this way, it is possible to produce acetic acid,
acetic anhydride and optionally methyl acetate from dime-
thylether, methanol and methyl iodide, for example. The car-
bon monoxide used may contain up to lû volume ~ hydrogen.
By varying the dialkylether/alcohol- feed ratio, it is
possible to establish practically any desirable product ra-
tio.of carboxylic acid/carboxylic anhydride. This is a spe-
~ cial advantage of the present invention permitting the pro-
; cess to be rapidly acted upon in accordance with require-
ments.
It is not absolutely necessary for pure carbon monoxide
to be used in the reaction. Relativaly small amounts of
inert gas, such as carbon dioxide, nitrogen or methane could
not be found to affect the carbonylation provided that the
CO-partial pressure inside the reactor is kept constant. A
hydrogen content of up to lû O has even been found positive-
3 ly to add to the catalyst activity but to reduce the selec-
lZS8469
tivity of the process by the formation of hydrogenation pro-
ducts, e.g. ethylidene diacetate or ethyleneglycol diaceta-
te.
The catalyst can be selected From all of the metals be-
longing to group VIII of the Periodic System (Ru, Rh, Pd, 05,
Ir, Pt). Rhodlum has however been found to be the most ac-
tive metal. It and all other noble metals should convenient-
ly be used in the form of compounds which are soluble under
the reaction conditions and form an acti~e noble metal/car-
bonyl-complex, e.g. RhC13 . 3H20, / Rh(C0)2Cl_/2, /_Pd(C0)2I_72,
3' ( 3C2)2' PdC12' Pd(C5H72)2- The noble metal
compound of group VIII should be present in the reaction
mi~ture in a preferred concentration of 0.001 to 0.1 mol/l,
more preferably 0.005 to 0.05 mol/l.
Lithium iodide ~is the most interesting of the alkali
- metal iodides which are used as promoter salts, but sodium
iodide or potassium iodide can also be employed. Methyltri-
butylphosphonium iodide should preferably be used as an or-
ganophosphonium iodide, but other quaternary phosphonium
iodides, such as methyltriphenylphosphonium iodide,
tetrabutylphosphonium iodide or dimethyldibutylphosphoniumiodide can also be used- The organoammonium compound prefe-
rably is N,N-dimethylimidazolium iodide, but it can also be
selected from N-methylpyridinium iodide, N-methyl-3-picoli-
nium iodide, N-methyl-Z,~-lutidinium iodide,
N-methyl-3,4-lutidinium iodide, N-methylquinolinium iodide,
etc. The concentration of the promoter salt in the reaction
mixture should be between 0.01 and 2 mol/l, preferably
between 0.1 and 0.8 mol/l.
lZS8~69
The carbonyl complex-formin9 non-noble metals of
groups IV, V, UI, VII and VIII which may be used as copromo-
ters, should conveniently be used in form oF a readily so-
luble ~ compound, e.g. as acetyl acetonate or carbonyl, in
the reaction. The concentrations of these copromoters in the
reaction mixture should conveniently be between 0.01 and 0.5
mol/l, preferably between û.05 and 0.3 mol/l. Compounds of
the metals Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co or
Ni are preFerably used.
The alkali metal iodide RI as a constituent typical of
the catalyst should be selected From materials in which the
alkyl radical R corresponds to the feed products ROR (ether)
and ROH (alcohol); failing this, mixed products are obtai-
ned. This means that it is necessary For methyl iodide to be
used for the production of acetic acid, methyl acetate and
acetic anhydride From dimethylether and methanol, whereas
ethyl iodide is required to be used For the production oF
propionic acid, ethyl propionate and propionic anhydride
from diethylether and ethanol. The concentration of alkyl
iodide in the reaction mixture should between 0.1 and 5
mol/l, preferably between 0.5 and 2.5 mol/l.
While the present process is preferably effected in li-
quid phase, it is also possible for it to be effected in gas
phase in contact with a carrier-supported catalyst. In the
two cases, reaction temperature preferably is between 150
and 250C and the operational pressure preferably is between
20 and 60 bar. The carbonylation process can be carried out
in a discontinuously and also in a continuously operated
production facility.
i2584~9
Example 1
3 mol dimethylether, dissolved in 3 mol methanol, 1 mol
methyl iodide, 0,2 mol methyltributylphosphonium iodide and
0.5 g rhodium in form of /_Rh(C0)2Cl_/2 were introduced into
an agitator-provided stainless steel (Hastelloy B2) autocla-
ve having a capacity of 1 liter, and a pressure of 25 bar
was established by injecting carbon monoxide. The whole was
heated to the reaction temperature of 180C and a total
pressure of 50 bar was maintained over a period of 45 minu-
tes by continuing the injection of carbon monoxide. After
- cooling with release of pressure, the reaçtion mixture was
analyzed gas-chromatographically and found to contain 3 mol
acetic acid, 0.8 mol methyl acetate and 2.2 mol acetic an-
::
hydride.
Example 2
Example 1 was repeated but the methyltributylphosphoni-
um iodide promoter was replaced by 0.2 mol N,N-dimethylimi-
dazolium iodide. The resulting product mixture was found to
contain 3 mol acetic acid, 0.6 mol methyl acetate and 2.4
mol acetic anhydride.
Example 3
; Example 1 was repeated but the methyltributylphosphoni-
um iodide promoter salt was replaced by 0.2 mol lithium
iodide. The resulting product mixture was found to contain 3
mol acetic acid, 0.9 mol methyl acetate and 2.1 mol acetic
anhydride.
Example 4
Example 1 was repeated while adding 0.05 mol zirconium
acetyl acetonate. After the reaction temperature of 180C
had been reached, a total pressure of 50 bar was established
:
lZS84~9
over a period of 30 minutes by continuing the injection of
C0. The resulting product mixture was worked up and found to
contain 3 mol acetic acid, 0.4 mol methyl acetate and 2.6
mol acetic anhyride.
Example 5
Example 1 was repeated whiLe adding 0.05 mol vanadi-
umhexacarbonyl and the batch was further treated as descri-
bed in Example 4. The product mixture was worked up and
found to contain 3 mol acetic acid, 0.5 mol methyl acetate
and 2.5 mol acetic anhydride.
Example 6
Example 1 was repeated while adding 0.05 mol chromace-
tylacetonate a~nd the batch was further treated as described
in Example 4. The product was worked up and found to contain
3 mol acetic acid, 0.3 mol methyl acetate and Z.7 mol acetic
anhydride.
Example 7
Example 1 was repeated while adding û.05 mol dirheni-
umdecacarbonyl and the batch was further treated as descri-
bed in Example 4. The resulting product mixture contained 3
mol acetic acid, 0.4 mol methyl acetate and 2.6 mol acetic
anhydride.
Example 8
Example 1 was repeated while adding 0.05 mol dico-
baltoctacarbonyl and the batch was further treated as des-
cribed in Example 4. The resulting product mixture contained
3 mol acetic acid, 0.5 mol methyl acetate and 2.5 mol acetlc
anhydride.
Example 9
2 mol dimethylether, dissolved in 4 mol methanol, 1.2
~Z58469
mol methyl iodide, 0.2 mol methyltributylphosphonium iodide
and 0.5 gram rhodium in form of L Rh(C0)2Cl_/2 were introd-
used into an agitator-provided stainless steel (Hastelloy
B2) autoclave having a capacity of l liter. Next, 25 bar
carbon monoxide and 2.5 bar hydrogen were injected. The
; whole was heated to the reaction temperature of 180C and a
total pressure of 50 bar was maintained over a period of 45
: minutes by continuous injection of a gas mixture of 90 mol
carbon monoxide and 10 mol ~ hydrogen. After cooling with
release of pressure, the reaction mixture was analyzed
gas-chromatographically and found to contain 4.4 mol acetic
acid, 0.2 mol methyl acetate, l.0 mol acetic anhydride and
0.4 mol ethylidene diacetate.
Example 10
Example 9 was repeated but the rhodium catalyst l.uas re-
placed by 0.5 9 palladium in form of palladium acetylaceto-
nate. The resulting product mixture contained 4.7 mol acetic
acid, 0.1 mol methyl acetate, 0.5 mol acetic anhydride and
0.7 mol ethylidene diacetate.
Example ll
3 mol diethylether, 2 mol ethanol, l mol ethyl iodide,
0.2 mol methyltributylphosphonium iodide and 0.5 9 rhodium
in form of ~Rh(C0)2Cl_/2 ~ere introduced into the autoclave
already described and a pressure of 25 bar was establish by
injecting carbon monoxide. The whole was heated to 180 C
and a reaction pressure of 50 bar was maintained over a pe-
riod of 3 hours by continuous injection of carbon monoxide.
The reaction product was worked up and found to contain 2
mol propionic acid, 1.2 mol ethyl propionate and 1.8 mol
3 propionic anhydride.
1258469
Example 12
3 mol dimethylether, dissolved in 3 mol methanol, 1 mol
methyl iodide, 0.2 mol tetrabutylphosphonium iodide and O.S g
r~ rhodium in form of / R~(C0)2C1_/2 were introduced into the
autocla~/e already described and a pressure of 25 bar was
established by injecting carbon monoxide. The whole was heated
to 180C and a total pressure oF 50 bar was maintained over
a period of 40 minutes by contlnuous injection of carbon
monoxide. After cooling with release of pressure, the reac-
tion mixture was analyzed gas-chromatographically and found
to contain 3 mol acetic acid, 0.7 mol methyl acetate and 2.3
mol acetic anhydride.
Example 13
5 mol dimethylether, 1 mol methanol, 1 mol methyl iodi-
de, 0.2 mol methyltributylphosphonium iodide and 0.5 9 rho-
dium in form of /_Rh(C0)2Cl_/2 were used. A C0-pressure oF
25 bar was established and the reaction mixture was heated to
180C. A total pressure of 50 bar was maintained over a pe-
riod of 45 minutes by continuous injection of carbon monoxi-
de. After cooling with release of pressure, the reaction
mixture was analyzed gas-chromatographlcally and found to
contain 1 mol acetic acid, 1.4 mol methyl acetate and 3.6
mol acetic anhydride.
Example 14
1 mol dimethylether, 5 mol methanol, 1 mol methyl iodi-
de, 0.2 mol methyltributylphosphonium iodide and 0.5 9 rho-
dium in form of ~ Rh(C0)2Cl_/2were used and treated in the
manner described in Example 13. The reaction product was
analyzed gas-chromatographically and found to contain 5 mol
acetic acid, 0.8 mol methyl acetate and 0.2 mol acetic anhydride.
lo
