Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-10-02
2002-10-29
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S813000
Reexamination Certificate
active
06472571
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to German Application DE 199 47 505.9, filed Oct. 1, 1999, which disclosure is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention concerns a process for the catalytic production of organic compounds. In particular the process operates in membrane reactors equipped with inorganic membranes.
BACKGROUND OF THE INVENTION
Catalytic processes are characterized in that the catalyst involved in the reaction is not consumed or is consumed only in small quantities. Even in a batch process a catalyst could, in ideal circumstances, be used for the reaction under consideration for an infinitely long period if losses during recycling or inactivation did not reduce the catalyst performance over time. Restricting the loss of catalyst can therefore contribute to minimizing process costs in catalytic synthesis performed on an industrial scale.
A continuous process, whereby the catalyst is immobilized in a reaction vessel while only the reactants can be added and only the products removed, is preferred to standard catalyst recycling, however. This processing mode can be put into practice in membrane reactors by the use of catalysts having increased molecular weight (Wandrey et al. in Jahrbuch 1998, Verfahrenstechnik und Chemieingenieurwesen, VDI p. 151ff.; Wandrey et al. in Applied Homogeneous Catalysis with Organometallic Compounds, Vol. 2, VCH 1996, p.832 ff.; Kragl et al., Angew. Chem. 1996, 6, 684f.).
Reports on catalysts having increased molecular weight or increased polymer have already appeared in the prior art on a number of occasions (Reetz et al., Angew. Chem. 1997, 109, 1559f.; Seebach et al., Helv. Chim Acta 1996, 79,1710 f.; Kragl et al., Angew. Chem. 1996, 108, 684f.; Schurig et al., Chem. Ber./Recueil 1997,130, 879f.; Bolm et al., Angew. Chem. 1997, 109, 773f.; Bolm et al. Eur. J. Org. Chem. 1998, 21f.; Baystone et al. in Speciality Chemicals 224f.; Salvadori et al., Tetrahedron: Asymmetry 1998, 9, 479; Wandrey et al., Tetrahedron: Asymmetry 1997, 8, 1529f.; ibid. 1997, 8, 975f.; Togni et al. J. Am. Chem. Soc. 1998, 120, 10274f., Salvadori et al., Tetrahedron Left. 1996, 37, 3375f.)
Until now exclusively polymeric membranes of organic origin have been used in processes in which homogeneously or colloidally soluble catalysts having increased molecular weight were used in membrane reactors.
The use of polymeric membranes is associated with a number of disadvantages, however, because of the organic solvents used in chemical synthesis.
The solvent resistance of the polymeric membranes that are commercially available at present applies in each case only to selected solvents. Different membranes therefore have to be used in production, depending on the reaction and solvent. In practice this means that the membranes have to be changed between different production batches. Moreover, when changing between polar and non-polar solvents, various membrane conditioning steps have to be interposed (Schmidt et al.; Chemie Ingenieur Technik (71), 3/1999).
Furthermore, the temperature resistance of the polymeric membranes that are commercially available at present is restricted to a maximum of 80° C. Information available in the literature or supplied by the manufacturer fluctuates between 40° and 80° C. for solvent-stable polymeric membranes. In homogeneous catalysis in particular, however, it may also be necessary to operate at temperatures above 70° C., since the degree of conversion can thereby be improved (“Metal-cat. Cross-coupling Reactions”, Ed.: F. Diedrich, P. J. Stang, VCH-Wiley, 1998
“Transition Metals for Org. Synthesis”, Ed.: M. Beller, C. Bolm, VCH-Wiley, 1998).
The flow rates for the currently available polymeric membranes in the area of ultrafiltration and especially nanofiltration are very low for industrial use. The flow rates that can be achieved depend on the solvent and membrane used, but are generally well below 5 l/m
2
/h/bar (Schmidt et al.; Chemie IngenieurTechnik (71), 3/1999).
The polymeric membranes display poor mechanical stability in regard to pressure. The use of these membranes at elevated pressures is technically achievable only by incorporating them in specially made and hence expensive flat or filament-wound modules with appropriate module housings.
SUMMARY OF THE INVENTION
The object of the present invention was therefore to provide a process whereby the problems in terms of solvent dependence, sensitivity to pressure, poor flow rate or reduced temperature resistance of the membranes as referred to above do not arise, such that their use in the manufacture of organic compounds on an industrial scale appears to be possible without reservation and to be advantageous in economic terms.
This object is achieved both economically and effectively in a process for the production of organic compounds in a membrane reactor with the aid of homogeneously or colloidally soluble catalysts having increased molecular weight, by using as membrane an inorganic membrane that displays an inorganic backing layer and an inorganic interlayer, whereby the interlayer can be modified with organic groups.
In principle the use of inorganic membranes for the retention and separation of heterogeneous catalysts is documented by various processes (e.g. DE 197 27 715 A1), but such membranes have so far not been proposed for the separation of homogeneously or colloidally soluble catalysts having increased molecular weight.
One reason for this is that unlike heterogeneous catalysts, the retention ability of homogeneously or colloidally soluble catalysts having increased molecular weight is not linked in a straight-forward manner to the molecule size. Instead the retention ability is determined by what is known as the hydrodynamic molecule diameter, which is governed by various parameters (molecular structure, solvent, etc.). However, the importance of an extremely high retention ability in a catalyst behind a membrane relative to the loss of catalyst due to bleeding is illustrated in
FIG. 1
by means of simple theoretical estimates. Only when the retention is well above >99.9% are the catalysts retained in the reactor to a sufficient degree and for residence times that are of any interest for industrial applications.
While polymeric membranes have enabled appropriate residence times to be achieved for some time now as a result of extremely favorable cut-offs, in the case of inorganic membranes this has only been technically feasible for a relatively short time.
Another effect likewise discouraged the use of inorganic membranes. The retention ability in the dead-end mode of operation is lower in comparison to that of polymeric membranes with a comparable cut-off.
TABLE 1
Example polymer: polystyrene in THF
Membrane
Polymer size [Da]
Retention %
Polymer-based nanofiltration membrane
70000
99.96
(nominal cut-off 700 Da)
Ceramic nanofiltration membrane
100000
99.61
(d
p50
< 0.9 nm)
Surprisingly it has been found that in the crossflow mode of operation, by contrast, a crossflow-dependent retention ability develops to such an extent that it can compensate for or even overcompensate for this disadvantage, even at relatively low crossflow speeds (see Table 2 and Example 1).
This was extremely surprising, yet no less advantageous as a consequence.
TABLE 2
Retention ability and crossflow speeds at an inorganic membrane in
a three-channel membrane module (dp
50
< 0.9 nm) for a polystyrene
polymer in THF as a function of the average molecular weight.
Ceramic membrane (dp
50
< 0.9 nm)
Crossflow speed
Molecular weight of polymer [Da]
0.5 m/s
2 m/s
4000
Retention 96.72%
97.60%
47500
Retention 99.82%
99.96%
280000
Retention > 99.98%
>99.98%
In principle all inorganic membranes familiar to the person skilled in the art that display an inorganic backing layer and an inorganic interlayer can be used as membranes. The interlayer forms the actual small pore diameter required for retention, whereby this can be modified using organic groups known to the person s
Boldt Kai
Bommarius Andreas
Burkhardt Olaf
Drauz Karlheinz
Henniges Hans
Degussa-Huls AG
Pillsbury & Winthrop LLP
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