Note: Descriptions are shown in the official language in which they were submitted.
2162083
Process for preParing formylcarboxylic esters
The invention relates to a process for preparing di- and
polyformylcarboxylic esters by hydroformylation of esters
of multiply unsaturated fatty acids in the presence of an
aqueous solution containing rhodium carbonyl/phosphine
complexes as catalyst and additionally a surfactant.
The hydroformylation of unsaturated fatty acid esters is
attracting increasing interest. This is based, in parti-
cular, on the fact that the starting materials are
frequently native raw materials or substances produced
from native raw materials which are available in large
quantities. The reaction products of the hydro-
formylation, mono- or polyformylcaboxylic esters, which
can also still contain reactive double bonds, are sought-
after intermediates. They can be further processed intowidely used products such as polyamines, polyurethanes,
alkyd resins, plasticizers and synthetic lubricants.
The hydroformylation of higher, multiply olefinically
unsaturated compounds has already been repeatedly
studied. A problem in this reaction is the high molecular
weight of starting material and reaction product, which
makes separation and recycling of the catalyst homo-
geneously dissolved in the reaction product, e.g. by
distillation, impossible. Furthermore, when using multi-
ply unsaturated compounds having isolated but closelyspaced double bonds, double bond isomerization in the
hydroformylation can only be avoided by means of rhodium
carbonyl/tertiary phosphine complex catalyst systems.
A problem critical to the economics of the process is the
108s - free separation of the homogeneously dissolved
catalyst system from the reaction product and its re-
cycling in active form to the hydroformylation reactor.
Hitherto, it has only been possible to separate the
rhodium/phosphine catalyst from the reaction mixtures
containing formyl-fatty acid esters from the hydroformyl-
ation of monounsaturated fatty acid esters. However, the
21620~3
-- 2
procedure requires complicated measures, furthermore, the
catalyst is obtained in inactive form and the phosphine
part of the catalyst system is completely lost (J. Amer.
Oil Chem. Soc. Vol. 50, 455 (1973)).
Linoleic and linolenic methyl esters can be hydroformyla-
ted in the presence of heterogenized rhodium carbonyl/
phosphine complex catalysts based on polysiloxane
(Chemiker-Zeitung, 115 (1991, p. 39 ff)). When using
methyl linoleate, the process gives mono- and diformyl-
stearyl esters in yields of up to 95%, based on thedoubly unsaturated ester used. Linolenic acid too gives,
in the hydroformylation in the presence of the specified
catalyst system, only the diformyl compound; in contrast,
at most subordinate amounts of triformyl products are
obtained. The rhodium recovery is on average about 0.5%
of the noble metal originally used. It cannot be ruled
out that a part of the catalyst metal is present in
homogeneously dissolved form in equilibrium with the
fixed metal, 80 that the hydroformylation takes place not
only over the fixed-bed catalyst, but also in solution.
It is therefore an object of the invention to develop a
process which allows esters of unsaturated fatty acids to
be hydroformylated, with multiply unsaturated fatty acid
esters being not only partially, but completely hydro-
formylated. In addition, noble metal losses should belargely avoided.
The above-described object is achieved by a process for
preparing di- and polyformylcarboxylic esters. It com-
prises reacting esters of multiply un~aturated fatty
acids and low molecular weight monoalcohols with carbon
monoxide and hydrogen at from 100 to 180C and from 5 to
35 MPa in the presence of an aqueous solution contA; n; ng
rhodium-phosphine complexes as catalysts and additionally
a surfactant.
The hydroformylation of olefins having more than 6 carbon
2162083
atoms in the molecule in the presence of an aqueous
solution containing rhodium complexes as catalyst and
additionally a quaternary Ammo~;um salt as solubilizer is
known from EP-B-157 316. A further development of this
process is subject matter of EP-B-163 234. According to
this patent, C6- to C20-olefins are reacted with hydrogen
and carbon monoxide in the presence of rhodium or a
sulfonated arylphosphine whose cation is a quaternary
~mmonium ion.
Both processes concern exclusively the reaction of
monounsaturated compounds which, in addition, contain no
functional groups. Surprisingly, the new process enables
a plurality of double bonds present in the ester
molecule, including internal double bonds, to be simulta-
neously hydroformylated, giving, for example, diformylproducts from doubly unsaturated compounds and triformyl
products from triply unsaturated compounds.
Starting compounds for the process of the invention are
esters whose one component is a multiply, in particular
doubly and triply, unsaturated fatty acid having from 8
to 25, preferably from 10 to 20, carbon atoms in the
molecule and whose other component is a saturated mono-
alcohol having from 1 to 10 carbon atoms in the molecule,
preferably methanol. These esters are obtained from
natural oils, if desired previously refined and dis-
tilled, by transesterification. Examples of natural oils
as basis of the acid component of the starting ester are
cottonseed oil, thistle oil, peanut oil, pumpkin kernel
oil, linseed oil, corn oil, soybean oil and sunflower
oil.
Catalysts used in the process claimed are rhodium com-
pounds cont~; n; ng coordinated water-soluble phosphines,
i.e. salts whose anion is a phosphine which contains at
least one sulfonated or carboxylated aromatic radical.
The term phosphine also includes those compounds of
trivalent phosphorus in which the phosphorus atom is a
21~2~83
-- 4
constituent of a heterocyclic ring. The aromatic radical
can be bonded to the phosphorus atom of the phosphine
either directly or via other groups. Examples of aromatic
radicals are the phenyl and the naphthyl radical. They
can be singly or multiply sulfonated or carboxylated and
in addition can be substituted by further atom groups or
atoms such as alkyl, hydroxyl, halide. Monophosphine
anions are preferably derived from compounds of the
formula (1)
xlM
Arl ~
X2M
P / Ar2 ~
\ - y2
n2
X3M
n3 (1)
Here, Arl, Ar2, Ar3 are each a phenyl or naphthyl group,
yl~ y2~ y3 are each a straight-chain or branched alkyl
group having from 1 to 4 carbon atoms, an alkoxy group,
a halogen atom, the OH, CN, NO2 or RlR2-N groups, where Rl
and R2 are each a straight-chain or branched alkyl group
having from 1 to 4 carbon atoms; Xl, X2, X3 are each a
sulfonate (SO3-) or carboxylate (COO~) radical, nl, n2, n3
are identical or different integers from 0 to 5. M is an
alkali metal ion, one chemical equivalent of an alkaline
earth metal or zinc ion, an ammonium or quaternary
- ;um ion of the formula N(R3R4RsR6)~, where R3, R4, Rs,
R6 are each a straight-chain or branched alkyl group
having from 1 to 4 carbon atoms.
- 5 - 2 16208~
Preference is given to compounds of the above-described
formula in which Ar1, Ar2, Ar3 are each a phenyl radical
and Xl, X2, X3 are each a sulfonate radical in the meta
position to the phosphorus (tris(m-sulfonatophenyl)phos-
phine, abbreviated as TPPTS).
A further group of monophosphines suitable as catalyst
component are obtained by sulfalkylation of dialkylphos-
phines or diarylphosphines containing 1,2-, 1,3- or 1,4-
sultones
(CH2)n
~\
R-CH S02
O ~
(where n = 0, 1 or 2 and R = H, alkyl),
e.g. correspo~i ng to
CH2
CH2 S02
A2P-Na + ~ , ~ A2P(CH2)4-S03Na
CH2 ~
CH2
where A are identical or different alkyl or aryl
radicals.
The anion can be formed not only from monophosphines but
also from polyphosphines, in particular diphosphines,
which contain at least one sulfonated or carboxylated
aromatic radical. Diphosphine anions are preferably
derived from diaryl compounds of the formula (2)
- 6 ~ 2162083
(Rl)2P ~ P(R1~2
(H2C)m (CH2)m
(R2)n (R2)n (2)
which are substituted by at least one sulfonate (S03-)
radial or carboxylate (C00~) radical. In the formula,
are identical or different alkyl, cycloalkyl, phenyl,
tolyl or naphthyl radicals, R2 are identical or different
and are hydrogen, alkyl or alkoxy radicals having from 1
to 14 carbon atoms, also cycloalkyl, aryl or aroxy
radicals having from 6 to 14 carbon atoms or a fused
benzene ring, m are identical or different and are
integers from 0 to 5 and n are likewise identical or
different and are integers from 0 to 4. Preference is
given to the sulfonated compounds which are obtainable by
conventional methods. Useful representatives of this
class of compounds are the products obtained by sulfona-
tion of 2,2'-bis(diphenylphosphinf ethyl)-1,1'-biphenyl
or 2,2'-bis(diphenylphosphinomethyl)-1,1'-binaphthyl. An
example which may be mentioned of the anion of a hetero-
cyclic phosphorus compound is 3,4-dimethyl-2,5,6-tris(p-
sulfonatophenyl)-1-phosphanorbornadiene.
The alkali metal salts or the ammonium salts, in parti-
cular the sodium salts, of the sulfonated or carboxylated
phosphines are usually used as catalyst constituent.
An essential feature of the new method is the addition of
a surfactant (also described as solubilizer, phase-
transfer, surface-active or amphiphilic reagent) to the
aqueous catalyst solution. For the purposes of the
present invention, surfactants are substances or mixtures
2162083
-- 7
of substances which are compatible both with the aqueous
phase (the catalyst) and with the organic phase (the
unsaturated fatty acid ester) and are soluble in both
phases, at least at elevated temperatures. The task of
the surfactants is improving the solubility of the fatty
acid ester in the catalyst solution. This occurs by
aggregation of the surfactant particles to form micelles
above the critical micelle formation concentration
(c.m.c., cf. Ullm~nn~ Encyclopadie der technischen
Chemie, 4th edition, 1982, volume 22, pages 464, 465)
characteristic of each surfactant. The ester molecules
accumulate in the micelles and are transported in this
form into the aqueous catalyst phase in which the reac-
tion with the synthesis gas occurs.
According to the chemical structure, distinctions are
made between anionic surfactants such as the soaps, alkyl
sulfates, alkylbenzenesulfonates and alkylbenzene phos-
phates, cationic surfactants whose most important repre-
sentatives are the tetraalkylammonium salts, amphoteric
surfactants cont~;n;ng zwitterionic hydrophilic groups
and of which the aminocarboxylic acids, betaines, sulfo-
betaines and amine oxides are examples and finally non-
ionic surfactants which include alkyl and alkylphenyl
polyethylene glycol ethers, fatty acid alkylolamides and
sucrose fatty acid esters.
In the process of the invention, preference is given to
using amphoteric surfactants and, in particular, cationic
surfactants, e.g. tetrahexylammonium bromide, tetradecyl-
~o~;um bromide, N-dodecyl-N,N,N-trimethylammonium
bromide, N-tetradecyl-N,N,N-trimethylammonium bromide,
N-hexadecyl-N,N,N-trimethylammoniumbromide,N-octadecyl-
N,N,N-trimethylammonium bromide and amphoteric surfac-
tants such as N,N-dimethyldodecylammonium betaine,
N,N-dimethyloctylamine N-oxide, N,N-dimethldecylamine
N-oxide, N,N-dimethyldodecylamine N-oxide, N,N-dimethyl-
tetradecylamine N-oxide. The surfactants can be used as
uniform substances or as mixtures. The concentration of
_ - 8 - 2162083
the surfactant in the aqueous catalyst solution lies
above the critical micelle formation concentration under
the reaction conditions of the hydroformylation reaction.
The reaction of the multiply unsaturated fatty acid ester
with hydrogen and carbon monoxide is carried out at
temperatures of from 100 to 180C, in particular from 120
to 140C, and pressures of from 5 to 35 MPa, preferably
from 15 to 20 MPa.
The catalyst can be added to the reaction system in a
preformed stack. However, it can be prepared with equally
good results from the components rhodium or rhodium
compound and the aqueous solution of the sulfonated or
carboxylated phosphine under the reaction conditions in
the reaction mixture, i.e. in the presence of the fatty
acid ester. Apart from metallic rhodium in finely divided
form, the rhodium source used can be water-soluble
rhodium salts such as rhodium chloride, rhodium sulfate,
rhodium acetate or compounds soluble in organic media
such as rhodium 2-ethylh~noate or insoluble compounds
such as rhodium oxides.
The rhodium concentration of the aqueous catalyst solu-
tion is from 100 to 600 ppm by weight, preferably from
300 to 400 ppm by weight, based on the solution. To rule
out isomerization of the unsaturated fatty acid ester,
the sulfonated or carboxylated phosphine is used in such
an amount that at least 20 mol, preferably from 40 to
80 mol, of P(III) are present per mole of rhodium.
The pH of the aqueous catalyst solution should not be
below a value of 3. In general, the pH is set to from 5
to 10, preferably from 6 to 8.
The composition of the synthesis gas, i.e. the ratio of
carbon ~ono~;de to hydrogen, can be varied within wide
limits. In general, the synthesis gas used is one in
which the volume ratio of carbon monoxide to hydrogen is
2162083
g
1 : 1 or deviates only little from this value.
The reaction can be carried out either batchwise or
continuously.
The process of the invention is illustrated by the
following examples, but is not restricted to the embodi-
ments presented.
Experimental procedure
For the synthesis of the diformyl and triformyl deriva-
tives of fatty acid methyl esters by hydroformylation of
multiply unsaturated fatty acid methyl esters, use was
made either of technical-grade linseed oil fatty acid
methyl ester mixture having a composition of 55% of
methyl linolenate, 15% of methyl linoleate and 20% of
methyl oleate, remainder saturated fatty acid methyl
esters, or a mixture consisting of 90% of methyl
linolenate and 10% of methyl linoleate. The reactions
were carried out in 160 ml V4A steel autoclaves having a
pressure-resistant dropping funnel, pressure sensor,
bursting disk and thermocouple. A magnetically coupled
propeller stirrer having holes for introducing gas
provides intensive m; ~; n~ of the reaction mixture.
The catalyst solution was prepared in a Schlenk tube
flushed with argon which was charged with the calculated
amounts of rhodium compound (Rh4(C0) 12~ HRh(C0) (NaTPPTS) 3
or Rh2(S04)3), phosphine ligand, oxygen-free water and
surfactant. The pH of the catalyst solution was set using
NaHC03 or alkali metal hydroxide.
To prepare the actual hydroformylation catalyst, the
catalyst solution was pretreated with synthesis gas for
one hour while stirring and under the temperature and
pressure conditions of the hydroformylation in an auto-
clave which had been flushed with argon and then with
synthesis gas. Subse~uently, the unsaturated ester was
- lO 2162083
-
added dropwise.
The fall in pressure could be monitored during the
reaction using a pressure sensor with associated
recorder. After the reaction was complete, the autoclave
was cooled, slowly vented and the reaction mixture was
transferred to a separating funnel. Aqueous and organic
phases were separated, the organic phase was taken up in
ether and washed twice with twice its amount of distilled
water. While presumably little rhodium goes into the
organic phase, the latter was additionally washed with
NaTPPTS solution. The organic phase was dried over Na2S04,
filtered, the ether was distilled off and the hydro-
formylation product was analysed.
The hydrogenation of the hydroformylation product to give
the correspo~;ng hydroxymethyl compounds was carried out
at 100C and 14 MPa H2 pressure using, as catalyst, 10%
by weight (based on the hydroformylation product) of
Raney nickel slurry in methanol. As solvent, the same
volume of methanol was used. The reaction product freed
of catalyst by filtration and of methanol by distillation
was characterized by its fat-chemical parameters (iodine
number, carbonyl number, hydroxyl number).
Example 1
A 160 ml magnetically stirred autoclave was charged with
10 g of technical-grade linseed oil fatty acid ester
mixture (ester mixture based on the catalyst phase)
together with 20 cm3 of an aqueous catalyst solution
containing 0.08 mmol (200 ppm by weight) of Rh, 1.6 mmol
of NaTPPTS (P/Rh ratio 20), 3.2 mmol of tetradecyltri-
methyl~mo~;um bromide (7.5 times c.m.c.) and had beenadjusted to a pH of 8 using Na2C03. The two liquid phases
and the gas phase were intensively mixed at a reaction
pressure of 20 MPa and a temperature of 120C. After a
reaction time of 12 hours, the autoclave was cooled,
vented and the reaction product was worked up as
- 2162083
_,
described above. The conversion was 100%. The reaction
product had a composition of 26% by weight of monoformyl
product, based on the ester mixture used, 30% by weight
of diformyl product, based on the methyl linoleate and
methyl linolenate contents of the ester mixture, and 47%
by weight of trishydroformylation products, based only on
the methyl linolenate content of the ester mixture. The
above method of calculating the yield was also employed
for all other experiments using the technical-grade
linseed oil fatty acid methyl ester mixture.
Examples 2 - 6
Technical-grade linseed oil fatty acid methyl ester
mixture was hydroformylated in the presence of the water-
soluble rhodium carbonyl/NaTPPTS catalyst system as
described in Example 1, but with variation of the surfac-
tant. The results are summarized in Table 1.
Table 1
Surfactant pH of MF DF TF Conver~ion
cat. 801. [ % by weight ]
Ex. 2 [C16H33N~(CH3)3]Br 8 30 33 42 94
Ex. 3 [C18H3,Nt(CH3)3]Br 8 29 44 40 100
Ex. 4 tcl2H2sN~(cH3)3]Br 8 33 26 29 96
Ex. 5 C1jH29(CH3)2N - O5.6 32 41 38 99
Ex. 6 tC12H2s(CH3)2N]~5.6 39 17 5 78
CH2COO -
(MF, DF, TF = noformyl, diformyl, triformyl product~)
Example 7
Technical-grade linseed oil fatty acid ester mixture was
hydroformylated as described in Example 1, but using
three times the rhodium concentration (600 ppm of
rhodium) and twice the P/Rh ratio (40 : 1). The conver-
sion was quantitative. The product mixture contained:
- - 12 _ 216208~
27% by weight of monoformyl products
30% by weight of diformyl products
52% by weight of triformyl products
Examples 8 - 10
The surfactant concentration has a decisive influence on
the micellar two-phase hydroformylation, as the Examples
8 - 10 below show. For a micelle-aided hydroformylation
to be able to proceed, the critical micelle formation
concentration c.m.c. of the surfactant has to be main-
tained as a minimum concentration. Although a hydro-
formylation is possible in the premicellar region (0.85
times the c.m.c.), see Example 8, the reactivity
increases strongly with increasing surfactant concentra-
tion. The yields, particularly of triformyl products,
increase and the yield becomes quantitative.
The results of a number of experiments using different
concentrations of the cationic surfactant tetradecyltri-
methylammonium bromide are 8 G arized in Table 2. The
reaction conditions correspond to those of Example 1, but
the Rh concentration in the aqueous phase was 275 ppm by
weight. The volume ratio of catalyst phase to organic
phase was 3 : 1.
Table 2
Surfactant conc. Times Colv~lsion MF DF TF
[mol/l] c.m.c. [% by wt.] [ % by wt. ]
Ex. 8 0.018 0.85 55 32 19 11
Ex. 9 0.053 2.50 95 29 24 33
Ex. 10 0.107 5.00 100 27 33 52
