Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-01-05
2002-09-17
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S451000
Reexamination Certificate
active
06452055
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the catalytic hydroformylation of olefins using carbon monoxide and hydrogen, wherein the hydroformylation reaction is carried out in a microemulsion.
2. Description of the Prior Art
In 1938, Otto Roelen studied the effects of olefins, specifically ethylene, on the Fischer-Tropsch synthesis in the laboratories of Ruhrchemie AG, Oberhausen. Roelen construed small amounts of propanol and diethyl ketone as products of a novel chemical reaction, namely hydroformylation (cf. DE 849 548, U.S. Pat. No. 2,237,066).
In the middle of the 1950s, this conversion of an alkene into an n-aldehyde and the isomeric iso-aldehyde, now known as the oxo synthesis over a transition metal catalyst, gained increasing economic importance.
Two factors were primarily responsible for this development: on the one hand, innovations in the petrochemical industry made it possible to produce the olefins in a sufficient amount with consistently high quality and at a favorable price and, on the other hand, the products of the hydroformylation were needed as intermediates in the production of PVC and detergents, two rapidly growing markets which even today are still the main outlets for hydroformylation products.
The first-generation catalysts contained only cobalt as a catalyst metal (BASF, ICI, Ruhrchemie). Owing to the high stability of the cobalt carbonyls, extreme reaction conditions were required: pressures of from 200 to 300 bar, temperatures of from 150° C. to 180° C. (H. Bahrmann, H. Bach,
Oxo Synthesis,
Ullmann, 5
th
ed., Vol. A 18, p. 321).
In the middle of the 1960s, the Shell process for the first time employed phosphine ligands in place of carbon monoxide, whereby the n:iso ratio could be increased. In addition, the reaction conditions were far less severe.
With the second generation of catalysts, this ligand modification was combined with the replacement of the cobalt central atom by rhodium. Modified rhodium catalysts allowed far milder reaction conditions, achieved higher n:iso ratios, and reduced the hydrogenation of the alkene as an undesirable secondary reaction. These processes, known as low-pressure oxo (LPO) processes, have been superseded at the beginning of the 1980s by the third generation of catalysts. In the Ruhrchemie/Rhöne-Poulenc (RCH/RP) process, water-soluble phosphine ligands enabled virtually loss-free recovery of the very expensive rhodium by phase separation of the aqueous catalyst solution from the organic product phase (DE-A-32 34 701, DE-A-32 35 030).
Water solubility of the catalyst is achieved by incorporation of one or a plurality of strongly polar group(s), such as —SO
3
H, —COOH, —NH
2
, or their salts, into the phosphine ligand. Development of the two-phase catalysis is therefore closely associated with the synthesis of such ligands.
Sulfonated phenylphosphines dissolve for instance in an aqueous medium at any pH value, while carboxylated phosphines only dissolve in acidic media. The hydrophilic character of triphenylphosphine (TPP) increases with an increasing number of sulfonic acid groups:
TPPMS<TPPDS<TPPTS=triphenylphosphinetrisulfonic acid
(TPPMS=triphenylphosphinemonosulfonic acid,
TPPDS=triphenylphosphinedisulfonic acid)
For industrial use, TPPTS is the ideal ligand for modifying the rhodium carbonyl species HRh(CO)
4
. Without any elaborate synthesis, 3 of the 4 CO ligands can be replaced by the readily water-soluble, nontoxic TPPTS.
It is thus possible to provide tailored complex catalysts for a wide variety of applications.
The greatest advantage of water-soluble ligands is the ease with which the hydroformylation products can be separated from the catalyst. Homogeneous catalysts are usually separated from the product by thermal separation methods, such as distillation/rectification. This thermal stress can result in deactivation or even decomposition of the complex catalyst. In addition, loss-free recovery is not always possible. In the two-phase system of the RCH/RP process, the rhodium losses are in the ppb range.
In the reaction of synthesis gas with olefins, the hydroformylation can be accompanied by a series of secondary reactions, which influence conversion and selectivity. The hydrogenation of the olefinic double bond results in irreversible formation of saturated hydrocarbon and is likewise catalyzed by cobalt and rhodium. This parallel reaction reduces the aldehyde yield. With unmodified cobalt catalysts, hydrogenation is achieved to an extent of about 15%, based on the olefin quantity. When using modified rhodium catalysts, this reaction takes place to an extent of less than 5%. Follow-up reactions of the resultant aldehydes, e.g. condensation, trimerization, and aldol reaction, result in formation of heavy-end products having significantly higher boiling points than the desired products.
One of the main disadvantages of homogeneous catalysis can be avoided by two-phase catalysis. However, this reaction technique requires a minimum solubility of the olefins in water and is therefore restricted to short-chain olefins. Relatively long-chain olefins cannot be converted by this process. Such olefins are still hydroformylated homogeneously by a high-pressure process (Exxon process) over cobalt catalysts.
One possibility of reacting relatively long-chain olefins in a two-phase catalysis on rhodium complexes is the addition of phase-transfer catalysts or surfactants to the aqueous catalyst solution, thereby effecting micellar solubilization of the water-insoluble substrates. For this purpose, addition of cationic surfactants is reported to be preferable because cationic surfactant micelles not only solubilize the water-soluble olefin but also, as a result of their positive charge, bring about an accumulation of the negatively charged rhodium complex ions, thus increasing their concentration in the environment of the micelles (
Journal of Molecular Catalysis A:
Chemical, 101, 1995, p. 179-186).
Surfactant phosphanes combining the function of the surfactant for the micellar co-catalysis with that of the complexing ligand for the catalysis of the carbonylation reaction are also employed to that end (
Journal of Molecular Catalysis,
66, 1991, p. 143-154).
Disclosed in U.S. Pat. No. 4,399,312 is a two-phase (aqueous phase/organic phase) hydroformylation reaction without formation of microemulsions. Reportedly, the addition of small amounts of amphiphilic reagents, such as ionic and nonionic surfactants with high HLB values, which are readily soluble in water, but sparingly soluble in oil, accelerates the materials transport without producing a microemulsion.
Nevertheless, the results when using phase-transfer catalysts or surfactants are not yet satisfactory in terms of reaction conditions and yields.
A new approach to a solution in the hydroformylation of long-chain olefins is the targeted reaction to form microemulsions.
Microemulsions are ternary mixtures of water, oil, and surfactant. The aqueous phase containing the catalyst is dispersed in the form of droplets in the oil phase, namely the olefin. At the phase boundary, catalyst, olefin, and dissolved synthesis gas meet and react to give the aldehyde.
EP-A-0 380 154 describes a hydroformylation process in which an olefin is reacted with hydrogen and carbon monoxide in the presence of a water-soluble hydroformylation catalyst in a microemulsion. The microemulsion comprises an oil phase made up of an olefin or an olefin and its hydroformylation products, an aqueous phase made up of the water-soluble complex catalyst, a surfactant, and a co-surfactant, with the oil phase forming the external phase of the microemulsion and the aqueous phase forming the internal phase. The co-surfactants which are most essential to form the microemulsion are preferably monohydric aliphatic alcohols having from 3 to 7 carbon atoms, in particular n-butanol or n-pentanol. Preferred surfactants are anionic ones, such as alkylbenzene-sulfonates or fatty alcohol sulfates.
A decided disadvantage of t
Haumann Marco
Koch Herbert
Schomaecker Reinhard
Browning & Bushman P.C.
Padmanabhan Sreeni
Sasol Germany GmbH
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