Process for carbonylation of ethylene

Details Process for carbonylation of ethylene Process for carbonylation of ethylene

1999-09-15

2001-09-04

Killos, Paul J. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C562S522000

Reexamination Certificate

active

06284919

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to the carbonylation of ethylene using carbon monoxide.
BACKGROUND OF THE INVENTION
The carbonylation of ethylene using carbon monoxide in the presence of an alcohol or water and a catalyst system comprising a Group VIII metal, e.g. palladium, and a phosphine ligand, e.g. an alkyl phosphine, cycloalkyl phosphine, aryl phosphine, pyridyl phosphine or bidentate phosphine, has been described in numerous European patents and patent applications, e.g. EP-A-0055875, EP-A-04489472, EP-A-0106379, EP-A-0235864, EP-A0274795, EP-A-0499329, EP-A-0386833, EP-A-0441447, EP-A-0489472, EP-A-0282142, EP-A-0227160, EP-A-0495547 and EP-A-0495548. In particular, EP-A0227160, EP-A-0495547 and EP-A-0495548 disclose that bidentate phosphine ligands provide catalyst systems which enable higher reaction rates to be achieved.
A problem with the previously disclosed catalyst systems is that although relatively high reaction rates can be achieved, the catalyst dies off quickly which necessitates the frequent replenishment of the catalyst and hence results in a process which is industrially unattractive.
WO 96/19434 disdoses a particular group of bidentate phosphine compounds which can provide remarkably stable catalysts which require little or no replenishment and the use of such bidentate catalysts in a process for the carbonylation of ethylene with carbon monoxide.
DETAILED DESCRIPTION OF THE INVENTION
It has now been found that, when used in the process for the carbonylation of ethylene with carbon monoxide, the activity and life of catalyst systems based on such phosphine compounds are very sensitive to the relative amounts of ethylene and carbon monoxide in the gaseous phase of the reactor. This is counter to the common teaching in the art which generally does not express any preference for the relative amounts of these reactants.
Surprisingly therefore, it has now been found that the activity and the life of the catalyst, when used in a liquid phase carbonation process, can be significantly improved by using a high molar ratio of ethylene to carbon monoxide in the gas in contact with the liquid phase.
Accordingly, the present invention provides a process for the carbonylation of ethylene in a liquid phase, which process comprises
(i) forming a gaseous phase from an ethylene feed stream and a carbon monoxide feed stream;
(ii) contacting the gaseous phase with a catalyst system within the liquid phase containing a source of hydroxyl groups. said catalyst system comprising palladium, or a compound thereof, and a phosphine ligand together with a source of anions; and
(iii) reacting the ethylene with the carbon monoxide in the presence of the source of hydroxyl groups and of the catalyst system
characterised in that the ethylene feed stream and carbon monoxide feed stream provide a molar ratio of ethylene to carbon monoxide in the gaseous phase which is greater than 1:1.
The carbon monoxide may be used in the presence of other gases which are inert in the reaction. Examples of such gases include hydrogen, nitrogen, carbon dioxide and the noble gases such as argon.
The molar ratio of the ethylene to carbon monoxide in the gaseous phase, hereinafter termed the gaseous phase molar ratio, is greater than 1:1, preferably at least 3:1, particularly at least 5:1, especially from 5:1 to 50:1 and particularly especially from 7:1 to 15:1. Operating the process of the present invention with a gaseous phase molar ratio of less than 5:1, particularly of less than 3:1 and especially of less than 1:1 leads to a rapid deterioration in the performance of the catalyst.
It is believed that an important factor that influences the life of the catalyst system is the molar ratio of ethylene to carbon monoxide dissolved in the liquid phase, herein after termed the liquid phase molar ratio. The liquid phase molar ratio may differ from the gaseous phase molar ratio due to the different solubilities of ethylene and carbon monoxide in the liquid phase. The solubilities of ethylene and carbon monoxide in the liquid phase are dependent on factors such as the temperature, pressure and composition of the liquid phase. Consequently, in order to achieve the required liquid phase molar ratio, the gaseous phase molar ratio may need to be adjusted to compensate for such factors. Preferably, the gaseous phase molar ratio should be adjusted such that a liquid phase molar ratio of at least 5:1 is maintained.
The ratio of the number of moles of ethylene to the number of moles of carbon monoxide fed to the reactor by the ethylene feed stream and carbon monoxide feed stream in order to maintain the desired molar ratio of ethylene to carbon monoxide in the gaseous phase will depend on the reactor design. Where the gaseous phase is recycled after contact with the liquid phase then the ethylene and carbon monoxide feed streams are used to replenish the ethylene and carbon monoxide consumed during the carbonylation reaction and the ethylene and carbon monoxide that is removed with any offtake from the liquid phase. Thus, the ratio of the number of moles of ethylene to the number of moles of carbon monoxide fed by the feed streams is approximately 1:1. Alternatively, where the gaseous phase is not fully recycled then the ratio of the number of moles of ethylene to the number of moles of carbon monoxide fed by the feed streams will more closely match the desired molar ratio in the gaseous phase.
The feeds of ethylene and carbon monoxide may be continuous, intermittent or batch. Preferably, the initial feed into the reactor is of ethylene. This further reduces the poisoning of the catalyst system by the carbon monoxide.
The process of the present invention is preferably carried out at a temperature from 20 to 250° C., in particular from 40 to 150° C. and especially from 70 to 120° C.
The process may be conducted under a total pressure of from 1×10
5
to 100×10
5
N.m
−2
and in particular from 5×10
5
to 50×10
5
N.m
−2
.
A preferred phosphine ligand is a bidentate phosphine of general formula (I)
wherein
R
0
is a tertiary carbon atom each of R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
, R
10
, R
11
, and R
12
is independently a pendant optionally substituted organic group which carries a carbon atom through which the group is linked to the respective R
0
;
each of L
1
and L
2
is independently a linking group selected from an optionally substituted lower alkylene chain connecting the respective phosphorus atom to the group, X; and
X is a bridging group comprising an optionally substituted aryl moiety to which the phosphorus atoms are linked on available adjacent carbon atoms.
The pendant optionally substituted organic groups of the preferred catalyst system, R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
, R
10
, R
11
and R
12
, may be independently selected from a wide range of components. Preferably, the pendant groups are optionally substituted lower alkyl, e.g. C
1-8
, and may be branched or linear.
Particularly preferred is when the organic groups, R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
, R
10
, R
11
and R
12
, when associated with their respective R
0
carbon atom, form composite groups which are at least as sterically hindering as t-butyl. Steric hindrance in this context is as discussed at page 14 et seq of “Homogeneous Transition Metal Catalysis—A Gentle Art”, by C Masters, published by Chapmnan and Hall, 1981.
The linking groups, L
1
and L
2
, are independently selected from an optionally substituted, particularly lower alkyl or lower alkylene, e.g. C
1
to C
4
, chain. Especially preferred is when both L
1
and L
2
are methylene.
The bridging group X is an aryl moiety, e.g. a phenyl group, which may be optionally substituted, provided that the two phosphorus atoms are linked to adjacent carbon atoms, e.g. at the 1 and 2 positions on the phenyl group. Optional substitution of the aryl moiety may be by other organic groups, e.g. alkyl, particularly C
1-8
, aryl, alkoxy, carbalkoxy, halo, nitro, trihalomethyl and cyano. Furthermo

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