Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-11-09
2002-06-11
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S451000
Reexamination Certificate
active
06403837
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a process for preparing aldehydes by hydroformylation of olefins or olefin mixtures in the presence of a catalyst comprising a metal of transition group 8, a phosphite ligand and a functionalized phosphonite ligand.
2. Background of the Invention
Aldehydes, in particular those having from 4 to 25 carbon atoms, can be prepared by catalytic hydroformylation of olefins having one less carbon atom (oxo process). The hydrogenation of these aldehydes gives alcohols which are used, for example, for preparing plasticizers or as detergents. Oxidation of the aldehydes gives carboxylic acids which can be used, for example, for preparing drying accelerators for surface coatings or as stabilizers for PVC.
The type of catalyst system and the optimum reaction conditions for the hydroformylation depends on the reactivity of the olefin used. A concise overview of hydroformylation, examples of catalysts and their fields of application, current industrial processes, etc., may be found in B. Cornils, W. A. Herrmann (Ed.), “Applied Homogeneous Catalysis with Organometallic Compounds”, VCH, Weinheim, New-York, Basel, Cambridge, Tokyo, 1996, Vol. 1, pp. 29-104. The dependence of the reactivity of the olefins on their structure is described, for example, by J. Falbe, “New Syntheses with Carbon Monoxide”, Springer-Verlag, Berlin, Heidelberg, N.Y., 1980, p. 95 ff. The differing reactivity of isomeric octenes is likewise known (B. L. Haymore, A. van Hasselt, R. Beck, Annals of the New York Acad. Sci., 415 (1983), pp. 159-175).
The various processes and catalysts make it possible to hydroformylate many olefins. A raw material which is of importance in terms of quantity is propene, from which n- and i-butyraldehyde are obtained.
Industrial olefin mixtures which are used as feedstocks for the oxo process often comprise olefins having a variety of structures with different degrees of branching, different positions of the double bond in the molecule and possibly also different numbers of carbon atoms. A typical example is raffinate I, which is a mixture of the C
4
-olefins 1-butene, 2-butene and isobutene. This is particularly true of olefin mixtures which have been formed by dimerization, trimerization or further oligomerization of C
2
-C
5
-olefins or other readily available higher olefins or by cooligomerization of olefins. Examples of industrial olefin mixtures which can be hydroformylated to give the corresponding aldehyde mixtures are tripropene and tetrapropene and also dibutene, tributene and tetrabutene.
The products of the hydroformylation are determined by the structure of the starting olefins, the catalysts system and the reaction conditions. Under conditions under which no shift of the double bond in the olefin occurs, hereinafter referred to as nonisomerizating conditions, the formyl group is introduced at the place in the molecule where the double bond was located, which can result in two different products. Thus, for example, the hydroformylation of 1-pentene can form hexanal and 2-methylpentanal. In the hydroformylation of 1-pentene under isomerizing conditions, under which a shift of the double bond in the olefin takes place in addition to the actual hydroformylation, 2-ethylbutanal would be expected as an additional product.
If alcohols for the preparation of detergents and plasticizers are sought as downstream products of the oxo aldehydes, predominantly linear aldehydes should be prepared in the oxo process. The products synthesized therefrom have particularly advantageous properties, e.g. low viscosities of the plasticizers prepared therefrom.
The abovementioned industrial olefin mixtures often contain only small proportions of olefins having a terminal double bond. To convert them into products in which more terminally hydroformylated olefin is present than in the original olefin mixture, the hydroformylation has to be carried out under isomerizing conditions. Processes suitable for this purpose are, for example, high-pressure hydroformylations using cobalt catalysts. However, these processes have the disadvantage that they form relatively large amounts of by-products, for example alkanes, acetals or ethers.
When using rhodium complexes as catalyst, the ligand also has a critical effect on the product composition of the aldehydes. Unmodified rhodium carbonyl complexes catalyze the hydroformylation of olefins having terminal and internal double bonds, which olefins may also be branched, to give aldehydes having a high degree of branching. The proportion of terminally hydroformylated olefin is significantly smaller than in the case of the cobalt-hydroformylated product.
In the presence of a ligand-modified catalyst system comprising rhodium and triorganophosphene, e.g. triphenylphosphene, &agr;-olefins are terminally hydroformylated with high selectivity. Isomerization of the double bonds and/or hydroformylation of the internal double bonds hardly occur at all.
The hydroformylation of olefins having terminal double bonds in the presence of catalyst systems containing bulky phosphite ligands does not proceed satisfactorily at high conversions with high n/iso selectivity at the same time.
An overview of the influence of ligands on the activity and selectivity in hydroformylation may be found in the above-cited book by B. Cornils and W. A. Herrmann.
Compared to phosphene or phosphite ligands, the technical literature contains only few publications on the use of phosphorous diesters (hereinafter referred to as phosphonites) as ligands in hydroformylation reactions. JP-A Hei 9-268152, WO 98/43935 and JP-B Hei 9-255610 describe catalyst systems comprising rhodium, a triorganophosphonite ligand or a bidentate phosphonite ligand for the hydroformylation of acyclic or cyclic olefins or olefin mixtures. However, the hydroformylation of olefins having internal double bonds is not disclosed. Furthermore, there is no information on the structure of the products, in particular the ratio of internal to terminal hydroformylation.
WO 97/20795 describes a hydroformylation process in which metal organophosphites and sterically hindered organophosphorus ligands are used. This ligand combination is said to serve, by means of the different catalytic activity of the individual ligands, as an indicator for the activity of the total system. Phosphonite ligands are not described in WO 97/20795.
Furthermore, the use of polydentate polyphosphite ligands as constituents of hydroformylation catalysts is known from, for example, EP 0 214 622. Here too, various ligands are used at the same time. The effects of ligand mixtures on the linearity of the product are not described; in particular, a desired direction of the reaction to linear aldehydes is not disclosed.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process for the hydroformylation of olefins which enables branched, unbranched, terminal or internal olefins to be terminally hydroformylated in high yields and with high selectivities, i.e. it enables predominantly linear aldehydes to be prepared. It has surprisingly been found that the hydroformylation of olefins in the presence of catalysts comprising metals of transition group 8 together with phosphonites, arsenonites and stibenonites in the presence of organophosphites leads to linear, terminally hydroformylated products in high yields and with high selectivities.
The present invention accordingly provides a process for preparing aldehydes having from 4 to 25 carbon atoms by catalytic hydroformylation of the corresponding olefins, i.e., an olefin having 3 to 24 carbon atoms, wherein the catalyst comprises a metal of transition group 8 of the Periodic Table in the presence of a ligand A represented by formula I:
where
X is As, Sb or P; and
R
1
, R
2
, R
3
are each a substituted or unsubstituted aliphatic, cycloaliphatic or aromatic hydrocarbon radical having from 1 to 50 carbon atoms,
where two of the radicals R
1
, R
2
, R
3
can be covalently linked with the proviso that at leas
Boerner Armin
Hess Dieter
Roettger Dirk
Selent Detlef
Oxeno Olefinchemie GmbH
Padmanabhan Sreeni
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