Hydroformylation process

Details Hydroformylation process Hydroformylation process

1999-02-10

2001-02-13

Padmanabhan, Sreeni (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S451000

Reexamination Certificate

active

06187962

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a hydroformylation process wherein ethylenically unsaturated compounds are contacted with carbon monoxide and hydrogen gas in a reaction zone in the presence of a solvent and a homogeneous catalyst based on a Group 8, 9 or 10 metal (referring to the IUPAC classification of elements in use in 1997).
The hydroformylation of ethylenically unsaturated compounds, to form products such as aldehydes and/or alcohols, is of considerable industrial importance. As is apparent from the literature, e.g., “New Syntheses with Carbon Monoxide” by J. Falbe (Springer-Verlag 1980; ISBN 0-387-09674-4) and “Carbonylation” by H. M. Colqhoun, D. J. Thompson and M. V. Twigg (Plenum Press 1991; ISBN 0-306-43747-3) a multitude of catalysts based on Group 8, 9 or 10 metals (Fe, Ru, Os; Co, Rh, Ir; Ni, Pd, and Pt) have been used in hydro-formylation processes. The most important industrial hydroformylation processes are presently based on the Group 9 metals; Co and Rh. Extensive patent art is also present on hydroformylation processes based on the Group 10 metals, Ni, Pd and Pt.
For various reasons, not in the least the costs of replacing lost catalyst, the catalyst must be recovered from the hydroformylation product. Mere distillation of the hydroformylation product, however, may inactivate and hence destroy the catalyst. Catalysts that are prone to destruction are therefore separated, for instance, by extraction.
In International application WO 95/05354 a process is disclosed wherein a major portion of the metal component of the catalyst system is recovered by causing at the end of the reaction the crude product to form two immiscible layers, and separating the layer comprising the hydroformylation product from the layer comprising the catalyst. The product layer, however, will still contain active catalyst. This reference provides no teaching how that should be recovered.
From EP-A-0,350,922 a process is known for the separation and recovery of an aldehyde product from a non-aqueous hydroformylation reaction product composition. The process involves phase separation using added water or both added water and an added non-polar hydrocarbon compound. Comparative example 1 of this reference illustrates the inadequacy of recovery by mere phase separation, whilst improved phase separation is shown when water is added. However, it should be observed that this process is conducted in the presence of a water soluble hydroformylation catalyst system. Thus, ionically charged phosphorus ligands are used, which will together with the metal complex- easily separate into the aqueous phase during the phase separation step. For catalyst systems based on non-ionically charged phosphorus ligands, which are the more common type ligands, this document provides no teaching either.
The inventors have set out to develop a hydro-formylation process, based on non-ionically charged ligands, with essentially full catalyst recovery.
SUMMARY OF THE INVENTION
Accordingly, a hydroformylation process is provided comprising the steps of:
(a) contacting one or more ethylenically unsaturated compoundts) with carbon monoxide and hydrogen gas in a reaction zone in the presence of a solvent and a homogeneous catalyst based on a Group 8, 9 or 10 metal and a non-ionically charged ligand, to form a crude reaction product;
(b) allowing a major portion of the solvent, wherein a major portion of the catalyst is dissolved, to separate and be withdrawn from the crude hydroformylation product in a phase separation zone; and
(c) removing from the separated hydroformylation product emerging from step (b) substantially all remaining catalyst dissolved therein with a non-aqueous extractant in an extraction zone.
In step (c) as extractant preferably the same substance is used as the solvent used in step (a), thereby avoiding contamination of recycle streams.
In a (fully integrated) process that uses recycle streams, the extraction step (c) is preferably carried out (in a multi-stage mode) with an amount of extractant that matches the amount of solvent that is dissolved in the hydroformylation product emerging from step (c). Note that after the separation step (b) the hydroformylation product is still saturated with solvent. For instance, at a temperature of 40° C., 100 g of a sulfolane-saturated crude C
11
-C
12
olefin-derived hydroformylation product will contain about 8 g of sulfolane and therefore about 8 g of sulfolane is to be used for extraction. Obviously, the amount of extractant need not be an exact match; the process may be adapted to cope with for instance 0.9 to 1.1 times that amount.
Extraction step (c) affords a catalyst-loaded extractant. When extractant from step (c) and solvent are of the same substance, the catalyst-loaded extractant may be led to the reaction zone of step (a) and/or to the separation zone of step (b). The inventors found the latter embodiment to be beneficial as thereby substantially higher separation efficiencies could be realised in step (b).
The solvent-extracted hydroformylation product emerging from step (c) will contain solvent and/or extractant. Typically, the solvent and/or the extractant also needs removal. Distillation is one option, as the extracted hydroformylation product is now freed from valuable catalyst. However, this manner of separation may be less applicable when the solvent, the extractant and the product have similar boiling points. Therefore, removal by washing is preferred.
DETAILED DESCRIPTION OF THE INVENTION
Obviously, in case the solvent and/or the extractant are removed by washing, the problem should not be augmented by the presence of the medium used for washing. In other words, the solubility of the hydro-formylation product into. the medium should be less than into the solvent and/or extractant. Furthermore, the washing medium should preferably be a harmless impurity without undesired side-effects when becoming part of the recycle streams. Moreover, the medium should be cheap.
Water was found to be quite effective as washing medium. Thus, a step (d) is preferably added to the process of the invention that comprises:
(d) removing from the extracted hydroformylation product emerging from step (c) substantially all remaining solvent and/or extractant dissolved therein with a washing medium, that is preferably water, in a washing zone, separating the solvent and/or extractant from the washing medium emerging from the washing zone and optionally reusing each.
Preferably the water-washing is conducted (in a multi-stage mode) at temperatures in excess of 60° C., more preferably in excess of 70° C. and at a phase ratio of crude versus medium varying from 1:0.2 to 1:1 w/w. The lower temperature is important to avoid emulsification.
In the preferred embodiment, wherein the extractant and the solvent are of the same substance, the isolated extractant is preferably reused as extractant in step (c). Surprisingly, this small amount of extractant is sufficient to effectively remove substantially all the remaining catalyst from the separated hydro-formylation product emerging from step (b).
The extraction may be conducted in a column equipped with a rotary-disk contactor (cf. Perry's Chemical Engineers' Handbook, 6th ed., p. 21-77 and further) or a packed bed column. The packed bed column is more efficient in the present process, avoiding undesired emulsification, and is hence preferred. Highest extraction efficiencies may be realised using a packed bed column with structured packing.
The separated solvent emerging from step (b) contains valuable catalyst and is therefore preferably fed to the reaction zone of step (a) of the process.
Preferably, the phase separation of step (b) is caused by cooling the (single-phase) hydroformylation product to a temperature within the range of 0 to 80° C., more preferably within the range of 15 to 60° 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 phase separation to occur. No specific pressure

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