Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-07-03
2004-03-02
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S454000, C502S326000
Reexamination Certificate
active
06700021
ABSTRACT:
The present invention relates to a process for preparing aldehydes in the presence of a catalyst based on rhodium, wherein, during the process, supplementary rhodium is added to the process in the form of a specific reaction product. The invention further relates to the use of said reaction product and also a process for preparing a catalytic composition by the use of said reaction product.
It is known that aldehydes and alcohols containing one carbon atom more than a starting olefin may be prepared by transition metal-catalyzed reactions of the olefin with carbon monoxide and hydrogen (hydroformylation). In addition to cobalt, which finds industrial use as a catalytic metal on a large scale, rhodium in particular has gained increasing importance in recent years.
In the processes established in the art, the rhodium catalyst is generally a hydridorhodium carbonyl modified by additional ligands, in particular tertiary organic phosphines or phosphites. Usually, the ligands are present in excess so that the catalyst system, which is dissolved in the organic reaction product, comprises complex compounds and free ligand. The use of the rhodium catalysts described enables the hydroformylation reactions to be carried out at pressures below 30 MPa.
The hydroformylation reaction is generally run according to the aldehyde output. After a certain operation time, a loss of activity is observed which is manifested in a reduced aldehyde output. The cause for the loss of activity is believed to be the increased occurrence of catalyst and ligand decomposition products which react with the rhodium catalyst to form complex compounds which only have low catalytic activities, or an increasing concentration of high-boilers in the reaction mixture.
To counteract this loss of activity, EP-A-0544091 suggests the addition of maleic anhydride, fumaric acid or other olefinically unsaturated compounds to a used catalyst solution. These compounds react with the damaging decomposition products to form compounds which apparently no longer impair the activity of the rhodium catalyst. A disadvantage of this process is the very high quantity of maleic anhydride added. This process has therefore hitherto been unable to establish itself in the art.
DE-A1-199 40 249 relates to a process for preparing aldehydes with the use of an aqueous catalyst solution which as well as rhodium and aqueous phosphines comprises salts of aromatic sulfonic, carboxylic or phosphonous acids. The addition of these salts to used hydroformylation catalyst solutions leads to a clear improvement in activity in the hydroformylation reaction. Even the addition of these salts to freshly prepared catalyst solutions has a stabilizing effect and increases the catalyst lifetime. However, this process also requires the addition of supplementary salts to the aqueous catalyst solution which leads to the solubility limits of the ligand and its decomposition products being exceeded more quickly. Shortening of the life cycle of the catalyst solution or the catalyst on-stream time is the consequence.
EP-A-0269964 describes a process for preparing aldehydes, wherein, to maintain the original phosphine concentration, fresh phosphine solution is added until the total concentration of complexing phosphines and non-complexing secondary and decomposition products of the phosphines is about 35 to 45% by weight, based on the aqueous solution.
The industrial operation of the hydroformylation reaction is generally controlled by increasing the temperature with decreasing activity of the catalyst solution, i.e. reduced aldehyde output. However, this measure has the disadvantage of an increased thermal loading of the catalyst system which in turn leads to increased damage of the catalyst.
The inventors found that the aldehyde output may in principle also be increased by, instead of increasing the temperature, making an early supplementary addition of fresh rhodium compounds, e.g. of rhodium acetylacetonate, rhodium carboxylates or inorganic rhodium salts.
The use of a rhodium catalyst which has been preformed, i.e. obtained by a preceding reaction of a rhodium compound with carbon monoxide and hydrogen, as starting catalyst for a hydroformylation is known from EP-A-0246475. In this reference, the use of the preformed catalyst at the start of the hydroformylation reaction serves to reduce the reaction time in the initial phase of the reaction and to prevent the effluence of noble metal in this reaction segment.
Similarly, DE-A1-199 40 249 refers to the possibility of subjecting the rhodium catalyst before use as a starting catalyst in the hydroformylation reaction to a pretreatment in the presence of carbon monoxide and hydrogen.
EP-B1-0 695 734 includes a preforming step as a component of a process for rhodium recovery from the output of the hydroformylation.
However, the previously cited prior art contains no reference to preventing the loss of activity taking place during the hydroformylation process by adding further rhodium, and consequently the cited prior art contains no reference either to the form in which further rhodium may be added for optimal prevention of loss of activity.
It has now been found that the productivity of the hydroformylation reaction can be distinctly improved by rhodium supplementation when rhodium or a rhodium compound is not added untreated to the hydroformylation reactor, but is only added after it has been subjected to a pretreatment using carbon monoxide and hydrogen in the presence of rhodium-complexing compounds.
This is particularly surprising in that the pretreatment actually takes place under the conditions of the hydroformylation reaction (CO/H
2
pressure). Those skilled in the art would therefore have expected that a separate, preceding reaction of the supplementarily added rhodium or rhodium compound with carbon monoxide and hydrogen under pressure would be superfluous because such a reaction would actually also take place in the hydroformylation reactor under similar conditions. However, this expectation was very surprisingly incorrect. Apparently, under the conditions of the ongoing hydroformylation, a portion of the supplementarily added rhodium or rhodium compound is not converted to the active species. If, however, the rhodium or rhodium compound is first subjected to a separate pretreatment step in the presence of rhodium-complexing compounds with carbon monoxide and hydrogen, the reaction product generated is able to exhibit its activity in the ongoing hydroformylation losslessly, as it were. The present invention is therefore able to enormously increase the efficiency of the hydroformylation in relation to the rhodium used.
Without wishing to be bound to this theory, it is believed that a rhodium compound pretreated in this way appears to be present in such a form that it does not enter into competing reactions with ligand degradation products of the rhodium catalyst but is able to fully exhibit its catalytic activity.
It is therefore an object of the invention to provide a process for preparing aldehydes by the reaction of olefinically unsaturated compounds with carbon monoxide and hydrogen (referred to in the following as hydroformylation processes), which may also be operated over a relatively long period of time with high activity and without an increase in the reactor temperature which accompanies increased catalyst degradation or the addition of large quantities of extraneous additional compounds which increase the activity of the catalyst being necessary, and wherein the rhodium used is utilized optimally.
The invention therefore provides a process for preparing aldehydes by reaction of olefinically unsaturated compounds with carbon monoxide and hydrogen at temperatures of from 20 to 200° C. and pressures of from 0.1 to 50 MPa in the liquid phase in the presence of a catalyst based on rhodium, which comprises, during the process, adding supplementary rhodium in the form of a reaction product prepared by reacting metallic rhodium and/or one or more rhodium compounds in the presence of rhodium-complexing compo
Bohnen Hans
Frohning Carl Dieter
Wiebus Ernst
Celanese Chemicals Europe GmbH
Muserlian Lucas and Mercanti
Richter Johann
Witherspoon Sikarl A.
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