Note: Descriptions are shown in the official language in which they were submitted.
3~7~
23343-800
This invention rela-tes to a process for making mono-
carboxylic anhydrides of the general formula (RCO)2O by reacting
a carboxylic acid ester or dialkylether of the general formulae
RCOOR and ROR, respectively, in which R each stands for one and
the same alkyl group having from 1 to 4 carbon atoms, with car-
bon monoxide in gas phase in -the presence of iodine or bromine
or their compounds as a reaction promoter and also in the pres-
ence of a carrier-supported catalyst, at temperatures of from
130 to 400C and under pressures of from 1 to 150 bars, which
comprises: using a carrier-supported catalys-t having an organo-
silicon compound as a polyfunctional adhesion promoter bound to
the carrier material on the one hand, and to a nickel compound
on the other hand, the organosilicon compound corresponding to
one of the following general Eormulae:
I. Rlx Si-(CR3) -Y or
II. RnX3_nSi-(cR2)m-cHy2 or
. 1 . 3
ILI. [Rnx3-nsl-(cR2)m]2
in which
X stands for -Cl,-Br or -OR ;
Y stands for -NR2, -PR2, -~sR2, -SR or -SH;
Z stands for -NR -, -PR -, -~sR4- or -S-;
Rl stands for a Cl-C5-alkyl;
R stands for a Cl-C3-alkyl;
R stands for -H, a Cl-C5-alkyl or -C6H5;
R4 stands for a Cl-C6-alkyl, a C5-Cg-cycloalkyl or
6 5 6 5 2 ;
n stands for 0 or 1 or 2;
m stands for 0 -through 8.
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23343-~00
A process of this kind carried out in gas phase with
the use of a carrier-supported catalyst has already been dis-
closed in German Specification DE-OS 24 50 965 and Japanese
Specification JP-OS No. 47921/1975, which permits the disadvan-t-
ages accompanying liquid-phase methods, namely the difficult
separation and recycle of suspended and partially dissolved
ca-talyst and optionally promoter, to be avoided.
The gas phase processes described in the two specific-
ations use solid carrier-supported catalysts made by impregnat-
ing the carrier with a catalyst solution containing noble metals.In this way, it is not possible, however, e.g. for organonitrog-
en or organophosphorus compounds containing trivalent nitrogen
and phosphorus, respectively, to be fixed in the carrier-support-
ed catalyst, and this has been found generally to affect the
activity of the catalyst and selectivity of the reaction.
The present invention also permits -the above deficien-
cies to be obviated, however, by the use of so-called poly-
functional adhesion promoters (spacers) which already have prom-
oters of group, V, e.g. organylamines or phosphines, integrated
therein, and permit nickel compounds to be fixed to the catalyst
surface.
The invention is more specifically characterized by
the fact that the carrier-supported catalyst has an organosilicon
compound containing an alkoxy or halogen group and also an
organonitrogen, organophosphorus, organoarsenic, organosulfur,
mercapto or thioether group as a polyfunctional adhesion promoter
bound to the carrier material on the one hand, and to a nickel
compound, on -the other hand.
Further preferred and optional features of the process
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~ `
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23343-800
of this invention provide:
a) for the carrier-supported catalyst additionally to
con-tain as a promoter a metal compound seleeted from the 1st
through 3rd principal groups or the 4th through 7th subgroups of
the Periodic System of the elements;
b) for the organosilicon compound as the polyfunctional
adhesion promoter in the carrier-supported catalyst to be bound
to the carrier material on the one hand, and alternately to the
nickel compound and to a metal compound selected from the 5th
through 7th subgroups of the Periodic System of the elements
on the other hand;
c) in the organosilicon compound of the formula III,
R4 stands for a Cl- C6 -alkyl, a C5- C8-eycloalkyl
or C6H5 or C6H5CH2- which may be substituted with a halogen,
methoxy, ethoxy or a Cl- C3-alkyl;
m stands for 1 through 3;
d) for the earrler-supported eatalyst to eontain an inor-
ganie oxidie earrier or an active carbon carrier the residual
active hydroxy groups of which were inactivated by esterifica-
0 tion or etherification;e) for the carrier-supported catalyst to contain from 0.01
-to 50 wg-t %, preferably 0.1 to 20 wgt %, nickel compound,
adhesion promo-ter and further non noble metal compound, ii desir-
ed;
f) Eor the carrier-supported catalyst to be used in form
1"',``
~5~7~
of particles with a size of from 1 to 20 mm.
The catalys-t carriers should preferably be selected from
inorganic oxides, e.g. SiO2, Al203, MgO, TiO2, La203, ZrO2,
zeoli-tes, clay, NiO, Cr203, W03 or corresponding mixed oxides
but also active carbon having a BET-surface area of from 1 to
1000 m2/g, preferably 30 to 400 m2/g, and presenting OH-groups.
These OH-groups undergo reaction with the functi.onal group or
groups X of the adhesion promoter with formation of oxygen
bridges between carrier and adhesion promoter. The promoters
of the 5th or 6th principal group are chemically combined
with the adhesion promoter and are themselves one of its
functional groups which have the nickel compounds linked
thereto, if desired alternately with metal compounds from the
5th to 7th subgroups, especially vanadium, bromium or rhenium.
These nickel compound~s and further non-noble metal compounds,
if any, may well form bridges between individual adhesion
promoter molecules fixed to the carrier.
An advantage of the present process resides in the fact
that the promoters increasing the catalyst activity and se-
lectivity, which are selected from principal group V or VIof the Periodic System of the elements, form a functional
group Y or Z in a polyfunctional adhesion promoter and can
thus be fixed up to maximum concen-tration which is determined
by the number of OH-groups on the carrier surface. This is
the reason why it is not necessary for an organonitrogen or
organophosphorus promoter, for example, to be separated and
recycled. The process of this invention for making monocar-
boxylic anhydrides compares favorably in catalyst activity
and selectivity with the prior processes referred to herein-
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above carriea out in gas phase with the use of a carrier-
supported catalyst. In addition to this, the carri.er-supported
catalysts used in accordance with this invention are free from
expensive noble metals of groups VIII of the Periodic System
of the elements.
The process of this invention is more especially used
for making acetic anhydride from methyl acetate or dimethyl-
ether in the presence of methyl iodide or methyl bromide as
a reaction promoter. HI, HBr or more generally RI or RBr,
where R s~ands for an alkyl group having from 1 to 4 carbon
atoms1 can also be used as a reaction promoter.
In the general formulae defining the organosilicon com-
pounds which should conceniently be used as adhesion promo-
ters (spacers), X preferably stands for -OR and more prefe-
rably for methoxy and ethoxy. If n stands for 1 or 2, R1
preferably stands for an unbranched alkyl group, especially
methyl, ethyl or propyl.
The useful carrier materials have already been specified
hereinabove; useful mixed oxides are e.g. Cr203 - Al203, W03 -
20 Al203, MgO - Al203, SiO2 - Al203 or ZrO2 - Al203. The carrler-
supported catalyst preferably contains from 0.01 to 5 wgt %
nickel.
The nickel compounds useful for making the carrier-suppor-t-
ed catalyst comprise e.y. the following compounds:
25 Ni(C3)4, L-P (c6H5)3 72Ni(co)2~ Ni(c3Hl2)2l 2
The metal compounds from the first to third principal
groups or from the 4th through 7th subgroups of the Periodic
System, preferably of Li, Na, Mg, Ca, Al, Ti, Zr, V, Cr, W,
Re, should conveniently be selcted from hydroxides, carbonates,
~2~3~
carbonyls, hydrides, halides and further salts. The metal
compounds can be used in form of a solution for impregnat-
ing the catalyst carrier therewith.
For preparation of the carrier-supported catalyst of
this invention, it is necessary to have the polyfunctional
adhesion promoter (organosilicon compound) which is a
commercially available product or can be made by methods
described in literature. Speaking generally, one of the
nickel compounds speciEied and, if desired, one of the me-
tal compounds of the 5th to 7th subgroups is linked to theadhesion promoter, namely to promoter group Y or Z contain-
ing an element selected from the 5th or 6th principal
group. Next, the nickel-containing intermediary product is
reactively combined with the hydroxy groups of the carrier
material with escape of a group X as a compound XH (e.g.
HCl, HBr, or R OH). This is achieved by heating the com-
pounds suspended in an unpolar solvent (e.g. benzene,
toluene, xylene) over a period of 24 to 100 hours until
decolorized.
Alternatively, it is also possible first reactively
to combine the polyfunctional adhesion promoter (organo-
silicon compound) with the hydroxy groups of the carrier
with escape of a group X as a compound XH, and then additi-
vely to combine the nickel compound and, if desired, one
of the metal compounds of the 5th to 7th subgroup wi-th the
promoter group Y or Z of -the lntermediary product.
Details are indicated in tha catalyst description
herainaEter.
In order to increase the selectivity and suppress
- ~ ~r- ~
side reactions, it is good practice, especially for discon-
tinuous operation but also for the initial phase in a con-
tinuous process, to inactivate those residual 0~l-groups on
the surface of the catalyst carrier which have not reacted
with the functional yroups X of the adhesion promoter. This
can be done e.g. by silylation with trimethylchlorosilane,
methylation with methyl iodide or acetylation with acetic
anhydride.
The quantitative ratio of carboxylic acid ester or di-
alkylether and iodine(compound) or brominetcompound) in
the reaction zone may vary within wide limits. Generally,
howaver, 1 to 500 mols, preferably 1 to 100 mols, carboxy-
lic acid ester and/or dialkylether is used per 1 mol
iodine(compound) or bromine(compound). The temperature se-
lected for the reaction zone should be high enough to al-
ways have a gaseous reaction mixture therein, irrespective
of the conversion rate, and preferably is between 170 and
250C. The preferred pressure is between 10 and 40 bars.
The reaction mixture should convaniently be contacted
with the solid carrier-supported catalyst over a period of
from 1 -to lûO0 seconds, preferably 1 to 180 seconds. The
conversion should suitably be effected in a flow tube
arranged in upright position, packed with the carrier-
supported catalyst or in an autoclave provided with a
stirrer or in a shaking autoclave, having the carrier-
supported catalyst placed therein. While the carbonylation
is generally effected under practically anhydrous con-
ditions, lt is allowable for it to be carried out in the
presence of minor amounts of water as normally found in
3~
commercial starting materials, which however should not
exceed 1 mol %, based on the starting materials. In addition,
the carbonylation remains substantially uneffected by the
presence of minor amoun-ts of methanol in the starting mate-
rials or of hydrogen in commercial carbon monoxida.
The reaction mixture coming from the carbonylation zoneis gaseous and contains carbon monoxide, methyL iodide,
acetic anhydride, unreacted methyl acetate or dimethylether
and, under circumstances, minor proportions of acetic acid.
lû The gaseous reaction mixture is cooled with condensation of
acetic anhydride and, under circumstances, acetic acid. Un-
condensed gases, such as C0, CH3I, methyl acetate or dimethyl-
ether are recycled to the reaction zone, the reacted ester
or ether and C0 portions being continuously renewed. The
anhydrides are easy to separate, i.e. in uncomplicated
fashion, by cooling the effluent reaction mixture and re-
cycling the uncondensed gas. This is a particular advantage
of the process of this invention. The carrier-supported
catalyst is not con-taminated; it remains in the reac-tion
zone. As a rasult, the entire process is rendered consider-
ably simpler.
Example 1
2 ml (1.86 9) methyl acetate, 0.5 ml (1.14 9) rnethyl
iodide and 3.15 9 catalyst of the formula
10C2H5
L-A12o3~o-Si-CH2-CH2-P(C6H5)2 72Ni( )2
OC2H5
~3~
were reacted with carbon monoxide in a stainless steel
(Hastelloy C) autoclave having a capacity of 0.25 liter,
at 200C under a C0-pressure of 20 bars. The space/time-
yield after a reaction period of 1 h was 140 9 Ac20/g Ni
per hour
The yield of Ac20, based on the ester used,was 22 %
for a selectivity of 92 %.
Example 2
1.86 ml dimethylether, 0,5 ml (1.14 9) methyl iodide
10 and 3.15 9 of the catalyst of Example 1 were reacted in
the autoclave of Example 1 at 200C under a C0-pressure
of 20 bars. Acetic anhydride was obtained in a space/time-
yield of 30 9 Ac20 per 9 Ni per hour. The experiment was
run over a period of 5 hours.
The yield of Ac20, based on the ether used, was 6 %
for a selectivlty of 19 %.
Preparation of the catalyst of the formula:
2H5
/-Al2o3~o-si-cH2-cH2-p(c6~ls)2-72Ni( )2
OC2~l5
Aluminum oxide was activated by drying it over a period
of 10 hours at 200C under a préssure of 0.1 to 0.2 mi].li-
bar.
The catalyst was prepared in the presence of nitrogen
with exclusion of oxygen and water, all of the reactants
having been dried previously using a molecular screen 4 A.
65 mg (~.4 mg Ni.) of the compound of the formula
(C2H50)36i-cH2cH2p(c6H5)2 /2Ni(C0)2, dissolved in 40 ml
~ ~J~de ~a~
~L~S3~'7~
xylene, was added whila stirring to 3.2 9 activated aluminum
oxide (99 % Al203) which consisted substantially of particles
with a diameter of 3 mm, had an inner BET-surface area of
125 m2/g and a pore volume of 0.9 ml per 9, and the mixture
was brought to boiling. After having been refluxed over a
period of 72 hours, the solution was found to have been com-
pletely decolorized. The solvent was separated and the
catalyst was given into a Soxhlet. After 12 h Soxhlet-extrac-
tion with benzene, the catalyst was dried over a period of
8 hours at 85C under a pressure of 1.33 millibar.
To suppress side-reactions and improve the selectivity,
the catalyst was ultimately treated with trimethylchloro-
silane.
Al203~0H ~ Cl-Si(CH3)3 ) Al203~U-si(cH3)3
r To this end, the catalyst was completely covered at
room temperature with trimethylchlorosilane. The suspension
was heated to boiling and boiled under reflux until gas
ceased to be evolved. Next, the suspension was allowed to
cool, the catalyst was separated from the liquid and dried
over a period of 12 hours at 85C under 1.33 millibar.
The concentrated solvents were free from nickel. The
catalyst so made contained 0.13 wgt % nickel.
The intermediate compound of the formula
3 2 2 ( 6 5)2_/2Ni(C)2 from (C2H5o)3sicH CH P(C H )
and Ni(C0)4 with escape of C0-gas was prepared as described
by A.K. Smith e-t al.. J. mol. Catal. 2 (1977), page 223. The
3~t7~
compound of the formula (C2H50)3SiCH2CH2P(C6H5)2 from tri-
ethoxyvinylsilane and diphenylphosphine with exposure to
ultraviolet light was made as described by H. Nieberyall,
Makromol Chem. 52 (19~2), page 21S.
