A process is provided for the hydroformylation of ethylenically unsaturated compounds having at least 4 carbon atoms by reaction thereof with carbon monoxide and hydrogen in the presence of a solvent and a catalyst system obtainable by combining: PA1 a) a source of Group VIII metal cations; PA1 b) a source of anions; and PA1 c) a source of phosphine ligands, wherein the solvent is a C.sub.1, to C.sub.10 alkane or alkene having two or more cyano groups attached.

FIELD OF THE INVENTION 
The invention relates to a process for the hydroformylation of 
ethylenically unsaturated compounds by reaction thereof with carbon 
monoxide and hydrogen in the presence of a catalyst and a solvent. 
BACKGROUND OF THE INVENTION 
The hydroformylation of ethylenically unsaturated compounds to form 
oxo-aldehydes and/or oxo-alcohols, hereinafter referred to as 
oxo-products, is of considerable industrial importance. The process has 
been in commercial operation for decades and over the years much 
development work has been done to optimise the reaction conditions, the 
catalyst system and the equipment. Although significant progress regarding 
the separation and reuse of the catalyst system has been made, it is felt 
that in some aspects further improvement of the process is still needed. 
In International application WO 95/05354 a process is disclosed wherein a 
major part of the metallic component of the catalyst system is recovered 
upon cooling a single-phase liquid reaction medium comprising the reaction 
mixture and an aprotic solvent containing a strong polar group. Thus, a 
multiphase liquid reaction medium is formed comprising one phase in which 
a major part of the metallic component of the catalyst system is present 
and at least one further phase containing a major portion of the 
oxo-product. 
The preferred solvent in WO 95/05354 is sulfolane. Sulfolane is 
particularly suitable in the production of higher (C.sub.11 +) 
oxo-alcohols, when cooling to about ambient temperature suffices to form 
the multiphase liquid reaction medium. Regrettably, when producing lower 
oxo-products more rigorous cooling or more solvent is needed to cause 
phase separation. It will be appreciated that this adversely affects the 
economy of the process. Furthermore, traces of sulfolane remaining in the 
product phase need to be removed in a separate step to provide an 
oxo-product that meets regulatory standards regarding the contents of 
sulfurous compounds. It is therefore desirable to find alternatives to 
sulfolane that perform in an alike manner, and that may be selected at 
will to suit the range of oxo-products produced in a process as discussed 
above. However, such is not an easy task, as the alternatives must: (i) be 
a fluid at all working conditions; (ii) be catalytically inert or 
promoting; (iii) be able to dissolve the catalyst under reaction and 
separation conditions, (iv) provide a single phase at reaction conditions 
and allow phase separation with lower oxo-products (e.g., C.sub.7 
-C.sub.11 range) and/or higher oxo-products (e.g., C.sub.11 -C.sub.18 
range) at separation conditions, and (v) be thermally and chemically 
stable. 
SUMMARY OF THE INVENTION 
Surprisingly, the inventors have found a class of compounds that allow 
phase separation without excessive cooling or use of large amounts 
thereof, and that meet these conditions. Accordingly, a process is 
provided for the hydroformylation of ethylenically unsaturated compounds 
having at least 4 carbon atoms by reaction thereof with carbon monoxide 
and hydrogen in the presence of a solvent and a catalyst system obtainable 
by combining: 
a) a source of Group VIII metal cations; 
b) a source of anions; and 
c) a source of phosphine ligands, wherein the solvent is a C.sub.1 to 
C.sub.10 alkane or alkene having two or more cyano groups attached. 
DETAILED DESCRIPTION OF THE INVENTION 
Preferably, the solvent is a C.sub.1 to C.sub.6 alkane or alkene having two 
or more cyano groups attached. For instance, suitable solvents include 
dicyanomethane (malononitrile), 1,2-dicyanoethane (succinonitrile), 
1,4-dicyanobutane (adiponitrile), 1,4-dicyano-2-butene 
(dihydromuconitrile), 1,5-dicyanopentane (pimelonitrile), 
1,6-dicyanohexane (suberonitrile), 1,6-dicyanocyclohexane, and 
1,2,4-tricyanobutane, etc. and mixtures thereof either or not with 
sulfolane. 
When preparing the higher oxo-products, it is preferred to use a solvent in 
the higher carbon atom range, such as adiponitrile. Solvents in the lower 
carbon range, such as malonitrile, are preferred when preparing the lower 
oxo-products. 
The hydroformylation process of the invention may be carried out in a 
homogeneous reaction medium using a dissolved catalyst system of adequate 
activity, whereby nevertheless the catalyst, without significant loss or 
decomposition thereof, can be readily recovered and reused if so desired. 
Accordingly, the invention relates to a process for the hydroformylation of 
ethylenically unsaturated compounds having at least 4 carbon atoms by 
reaction thereof with carbon monoxide and hydrogen in a single-phase 
liquid reaction medium, in the presence of the aforementioned catalyst 
system, followed by effecting the formation of a multiphase liquid 
reaction medium, preferably by cooling the single-phase liquid reaction 
medium, comprising one phase in which a major part of the Group VIII metal 
cations of the catalyst system is present and at least one further phase 
containing a major portion of the hydroformylated product, wherein as 
solvent a C.sub.1 to C.sub.10 alkane or alkene having two or more cyano 
groups attached is used. 
In this manner it is possible to ensure that a major portion of the 
metallic component of the catalyst system, i.e. more than 70% thereof, is 
present in the liquid phase containing the inert solvent, whereas more 
than 80% of the oxo-product is present in another phase, the oxo-product 
phase, from which it can be easily recovered by known techniques. 
Using any of the solvents mentioned above, in combination with a 
well-selected oxo-product, the multiphase liquid medium can be readily 
formed when the temperature of the reaction mixture is decreased to close 
to ambient temperatures. If desired, the reaction medium can be cooled to 
lower temperatures, but for large-scale operation this is not considered 
of special advantage, in view of the additional provisions needed for 
cryogenic cooling. 
Mixtures of solvents may also be used, for example a mixture of one of the 
aforementioned solvents with sulfolane or with a protic solvent, such as 
an alcohol. In the latter embodiment, the alcohol will separate into the 
oxo-product phase. Typically, an alcohol is selected which is identical or 
similar to the oxo-alcohol as obtained in the hydroformylation reaction. 
For ease of operation, preferably a single solvent, which is a C.sub.1 to 
C.sub.10 alkane or alkene having two or more cyano groups attached, is 
used. 
The amount of solvent to be used in the process of the invention may vary 
considerably. For instance, the amount of solvent may vary from 3 to 50% 
by volume. Preferably, the multiphase liquid reaction medium is formed by 
cooling the single-phase liquid reaction medium to a temperature within 
the range of 0.degree. to 50.degree. C., more preferably within the range 
of 25.degree. to 45.degree. C. However, it is within the reach of those 
skilled in the art to establish in each case the degree of cooling and the 
optimal amount of solvent required for the formation of a multiphase 
liquid reaction medium. No specific pressure requirements or atmospheric 
conditions apply. The experimental results provided hereinafter are also 
indicative for the amount of solvent preferably to be used. 
The ethylenically unsaturated compound used as starting material is 
preferably an olefin having from 4 to 24 carbon atoms per molecule, or a 
mixture thereof. It is believed that with ethylenically unsaturated 
compounds having only 2 or 3 carbon atoms per molecule, the formation of a 
multiphase liquid reaction medium, whereby the metallic component of the 
catalyst system is present in one phase and a major portion of the 
oxo-product in another phase, can not be easily effected. 
The ethylenically unsaturated compound may comprise one or more double 
bonds per molecule. Preferred are internal olefins having from 6 to 14 
carbon atoms, or mixtures thereof. Such olefin mixtures are commercially 
readily available as products of a process for the oligomerization of 
ethylene, followed by a double bond isomerization and disproportionation 
reaction. Typical examples are mixtures of linear internal C.sub.6 to 
C.sub.8 olefins, of linear internal C.sub.11 to C.sub.12 olefins, and of 
linear internal C.sub.13 to C.sub.14 olefins. However, also alpha-olefins 
having from 6 to 14 carbon atoms may be used, for instance in the presence 
of a Pt-based catalyst system. 
Carbon monoxide and hydrogen may be supplied in equimolar or non-equimolar 
ratios, e.g. in a ratio within the range of 5:1 to 1:5, typically 3:1 to 
1:3. Preferably they are supplied in a ratio within the range of 2:1 to 
1:2. 
In the present specification the metals of Group VIII are identified by 
their symbol as Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt. Preferred are the 
metals of the platinum group, i.e., Ni, Pd and Pt. Of these, palladium is 
most preferred. Examples of suitable metal sources are compounds such as 
salts of the metal and nitric acid, sulfuric acid, sulfonic acids, or 
carboxylic acids with up to 12 carbon atoms; metal complexes, e.g. with 
carbon monoxide or acetylacetonate; or the metal combined with a solid 
material such as an ion exchanger or carbon. Palladium(II) acetate and 
platinum(II) acetylacetonate are examples of preferred metal sources. 
As component (b), any compound generating anions may be used. Such 
compounds may comprise acids or salts thereof; for example, any of the 
acids mentioned above, which may also participate in the salts of the 
Group VIII metals. The anions are preferably derived from strong acids, 
i.e., acids having a pKa value of less than 3, preferably less than 2 as 
measured in aqueous solution at 18.degree. C. The anions derived from 
these acids are non-coordinating or weakly coordinating with the Group 
VIII metals. The stronger the acid, the less the anion coordinates with 
the Group VIII metal cation and the higher is the linearity of the 
hydroformylation product. 
Typical examples of suitable anions are anions of phosphoric acid, sulfuric 
acid, sulfonic acids and halogenated carboxylic acids such as 
trifluoroacetic acid. Also, complex anions are suitable, such as the 
anions generated by a combination of a Lewis acid such as BF.sub.3, 
B(C.sub.6 F.sub.5).sub.3, AlCl.sub.3, SnF.sub.2, Sn(CF.sub.3 
SO.sub.3).sub.2, SnCl.sub.2 or GeCl.sub.2, with a protic acid, such as a 
sulfonic acid, e.g. CF.sub.3 SO.sub.3 H or CH.sub.3 SO.sub.3 H or a 
hydrohalogenic acid such as HF of HCl, or a combination of a Lewis acid 
with an alcohol. Examples of such complex anions are BF.sub.4 -, 
SnCl.sub.3 -, SnCl.sub.2.CF.sub.3 SO.sub.3 !.sup.- and PF.sub.6 -. The 
preferred anion source is trifluoromethanesulfonic acid. 
The phosphine ligand is preferably a bidentate ligand of the formula 
EQU R1R2P--R--PR3R4 (I) 
wherein R represents a bivalent organic bridging group containing from 1 to 
4 atoms in the bridge, R1 and R2 together represent a bivalent substituted 
or non-substituted cyclic group whereby the two free valencies are linked 
to one P atom and R3 and R4 independently represent a substituted or 
non-substituted hydrocarbyl group, or together represent a bivalent 
substituted or non-substituted cyclic group whereby the two free valencies 
are linked to the other P atom. 
In the organic bridging group, represented by R, typically all bridging 
groups are carbon atoms. Preferably the bridging group contains two carbon 
atoms in the bridge and is for example an ethylene group. 
The bivalent (substituted) cyclic group, represented by R.sup.1 together 
with R.sup.2, in general comprises at least 5 ring atoms and preferably 
contains from 6 to 9 ring atoms. More preferably the cyclic group contains 
8 ring atoms. Substituents, if any, are usually alkyl groups having from 1 
to 4 carbon atoms. As a rule, all ring atoms are carbon atoms, but 
bivalent cyclic groups containing one or two heteroatoms in the ring, such 
as oxygen- or nitrogen, atoms are not precluded. Examples of suitable 
bivalent cyclic groups are 1,4-cyclohexylene, 1,4-cycloheptylene, 
1,3-cycloheptylene, 1,2-cyclooctylene, 1,3-cyclooctylene, 
1,4-cyclooctylene, 1,5-cyclooctylene, 2-methyl-1,5-cyclooctylene, 
2,6-dimethyl-1,4-cyclooctylene and 2,6-dimethyl-1,5-cyclooctylene groups. 
Preferred bivalent cyclic groups are selected from 1,4-cyclooctylene, 
1,5-cyclooctylene, and methyl (di)substituted derivatives thereof. 
Mixtures of ligands comprising different bivalent cyclic groups may be used 
as well, e.g. mixtures of ligands with 1,4-cyclooctylene and ligands with 
1,5-cyclooctylene groups. 
In the ligands of formula (I), R.sup.3 and R.sup.4 may independently 
represent various non-cyclic or cyclic groups, optionally substituted with 
substituents such as alkoxy groups with 1 to 4 carbon atoms, halogen atoms 
or (C.sub.1 to C.sub.4 alkyl)amino groups. 
Examples are alkyl groups such as ethyl, isopropyl, sec-butyl and 
tert-butyl groups, cycloalkyl groups such as cyclopentyl and cyclohexyl 
groups, aryl groups such as phenyl and tolyl groups and bivalent groups 
such as a hexamethylene group. However, preferably R.sup.3, together with 
R.sup.4 represents a bivalent cyclic group, in particular the same group 
as the group represented by R.sup.1 together with R.sup.2, in which case 
the two free valencies of the bivalent cyclic group are, of course, linked 
to M.sup.2, instead of M.sup.1. Thus, preferred bidentate ligands of 
formula (I) are 1,2-bis(1,4-cyclooctylenephosphino)ethane, 
1,2-bis(1,5-cyclooctylenephosphino)ethane and mixtures thereof, as well as 
the homologues having two methyl groups attached to one or each of the 
cyclooctylenephosphino groups. 
For the preparation of the bidentate ligands, reference is made to known 
techniques, for example the method disclosed in GB-A-1,127,965. 
The quantity in which the catalyst system is used, is not critical and may 
vary within wide limits. Usually amounts in the range of 10.sup.-8 to 
10.sup.-1, preferably in the range of 10.sup.-7 to 10.sup.-2 mole atom of 
Group VIII metal per mole of ethylenically unsaturated compound are used. 
The amounts of the participants in the catalyst system are conveniently 
selected such that per mole atom of Group VIII metal from 0.5 to 6, 
preferably from 1 to 2 moles of bidentate ligand are used, and from 0.5 to 
15, preferably from 1 to 8 moles of anion source or a complex anion source 
(i.e., component b) are used. 
The hydroformylation can be suitably carried out at moderate reaction 
conditions. Hence temperatures in the range of 50.degree. to 200.degree. 
C. are recommended, preferred temperatures being in the range of 
70.degree. to 160.degree. C. Reaction pressures in the range of 1 to 300 
bar abs are suitable, but in the range of 5 to 100 bar abs are preferred. 
Lower or higher pressures may be selected, but are not considered 
particularly advantageous. Moreover, higher pressures require special 
equipment provisions. 
The process of the invention is eminently suitable to be used for the 
preparation of alcohols from internal olefins at high rate, in particular 
by using a catalyst system as defined above, based on palladium. 
Furthermore the process is very useful for the preparation of aldehydes 
having a high linearity, in particular by using a catalyst system as 
defined above, based on platinum as Group VIII metal.

The invention will be illustrated by the non-limiting examples, as 
described hereinafter. 
COMATIVE EXAMPLES A AND B, AND EXAMPLE 1 
Three experiments were carried out using respectively sulfolane (Comp. A), 
acetonitrile (Comp. B), and adiponitrile (Example 1) as solvent. These 
experiments were conducted in a 300 ml magnetically stirred autoclave 
("Hastelloy", a trademark) at 105.degree. C. and 50 bar abs (hydrogen 
gas/carbon monoxide ratio of 2:1 v/v). The autoclave was charged with 56 g 
of an internal C.sub.11 -C.sub.12 olefin (40% C.sub.11, 60% C.sub.12, ex. 
SHELL), 49 g of 2-ethyl-hexanol, 0.8 g water, 1-2 g C.sub.13 paraffin and 
an amount of solvent set out in the Table. The catalyst was obtained by 
combining palladium(II) acetate, diphosphine (90% isomeric pure 
1,2-bis(1,5-cyclooctylenephosphino)ethane), trifluoromethanesulfonic acid 
and zinc chloride in a molar ratio of 1:1.4:(1.9-2.6):1.5. The Pd 
concentration in the reactor was 0.04% by weight on total contents. 
The reaction was followed by means of GC. Typically, at virtual complete 
conversion (better than 99%) an overall alcohol yield of around 98% was 
observed. By-products are paraffin and, at incomplete conversion, 
aldehydes and heavy ends of the acetal type. Linearity (ratio n over n and 
branched in percent) was also determined by GC. Kinetic analysis provided 
pseudo first-order rate constants. 
After a reaction period of 4 hours, during which no further hydrogen or 
carbon monoxide was supplied, the single-phase reaction mixture was cooled 
to ambient temperature. Two liquid layers were formed in case sulfolane 
and adiponitrile were employed. Palladium was detected visually in the 
solvent layer. 
Additional details and analytical results are compiled in the Table 
following hereafter. 
Further comparative tests involved dimethylsulfoxide, 
N,N-dimethylformamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, 
1,3-dimethyl-2-imidazolidinone, monoethyleneglycol, diethyleneglycol, 
monomethyl ether of diethyleneglycol, triethyleneglycol, 
1,2-propyleneglycol, 1,4-butanediol, monoethanolamine, triethanolamine, 
anisole and tributylphosphineoxide, and glycerol. Albeit these solvents 
may be used in accordance with the teaching of WO 95/05354, either 
excessive cooling or large amounts of solvent are required, since in most 
cases no phase separation was observed at 25.degree. C. for mixtures of 
20% w solvent with 80% w C.sub.12 -C.sub.13 oxo-product. Only when 
monoethyl glycol and glycerol were employed was phase separation observed. 
However, in these cases the catalytic performance was extremely low. These 
results prove that the presently-claimed class of solvents comprises the 
preferred substitutes for sulfolane. 
TABLE 
______________________________________ 
Exp. No. A B 1 
______________________________________ 
Solvent conc. 
sulfolane acetonitrile 
adiponitrile 
(% w/% vol) 15.4/10 10.3/10 4.4/3.5 
Conv. 2h. (%) 
95 89 82 
Activity (H.sup.-1) 
1.5 1.1 0.9 
Linearity (%) 
77 78 76 
Paraffin (% w) 
0.7 0.8 0.6 
Aldehyde (% w) 
0.8 0.9 2.5 
Alcohol (% w) 
88 96 83 
Heavy Ends (% w) 
10 2.4 14 
Phase separation 
+ -* + 
at 20.degree. C. 
at 105.degree. C. 
- - - 
______________________________________ 
*no phase separation at 25.degree. C. when the concentration of 
acetonitrile is increased to 20% w.