Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-02-15
2001-05-01
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S451000, C556S137000
Reexamination Certificate
active
06225508
ABSTRACT:
The present invention relates to the technical field of hydroformylation of olefins.
The present invention achieves the object of preparing, in particular, relatively high molecular weight linear and branched and also cyclic alkanals by hydroformylation of corresponding olefins by means of a rhodium tri(polyethylene glycolate) as high-activity catalyst in high yield and purity and isolating them from the reaction mixture in a simple manner.
The hydroformylation of olefins to aldehydes using a noble metal complex is known. Thus, U.S. Pat. No. 4,329,511 describes the reaction of olefins with hydrogen and carbon monoxide to give aldehydes in inert high-boiling solvents, with the catalyst used being a noble metal of transition group VIII complexed by, for example, a triorganophosphine such as triphenylphosphine. The high-boiling solvent has to have a molecular weight of at least 700 when ethylene is used as starting olefin and of at least 1500 in the case of higher olefins. These high-boiling solvents are said to dissolve the catalyst and enable the catalyst to be reused after the alkanal formed has been isolated from the reaction mixture by distillation or by stripping with an inert gas. However, this procedure has, like all hydroformylation reactions of olefins carried out in a single phase using a metal catalyst, the considerable disadvantage that the alkanal, in particular one containing over 10 carbon atoms, can be separated off by distillation only with considerable difficulty, if at all, because of its high boiling point; apart from losses of the alkanal end product, not inconsiderable amounts of heavy oils are formed as decomposition products. The hydroformylation process described in this U.S. Pat. No. 4,329,511 is therefore only economically feasible for the synthesis of lower alkanals such as those having up to 7 carbon atoms. To drive relatively high molecular weight, high-boiling alkanals out of the reaction mixture, the reaction gases (carbon monoxide, hydrogen and olefin) have to have a temperature of over 250° C.
The hydroformylation of olefins by the processes of the published European Patent Application No. 0 314 435 and U.S. Pat. No. 4,613,701 is carried out similarly; in these processes, as a consequence of the disadvantages discussed here, only low molecular weight olefins are used in the reaction.
Furthermore, DE-A 2 552 351 describes the reaction of olefins with hydrogen and carbon monoxide in the presence of a rhodium salt such as rhodium chloride, rhodium sulfate and rhodium nitrate in water or an alkanol as reaction medium and solvent with addition of a lower polyethylene glycol having up to three ethoxy units. This lower polyethylene glycol is supposed to prevent precipitation of the rhodium salt from the reaction solution. This process, too, is carried out in a single phase and has the abovementioned disadvantages.
In contrast, two-phase catalyst systems using a solvent which does not dissolve the alkanal formed offer technical advantages. The phase containing the catalyst can be separated from the alkanal formed without additional process steps. In addition, it is not absolutely necessary to isolate the catalyst after the reaction if the polar phase containing the catalyst can be used in a continuous hydroformylation process in which alkanal formed can also be separated off during the process. Such a process is known, for example, from DE-A 2 627 354 in which linear olefins are hydroformylated in water as solvent in the presence of a rhodium-triphenylphosphine complex containing sulfo groups. However, this procedure does not allow relatively long chain olefins, e.g. those having more than 5 carbon atoms, to be reacted, since the yield of the alkanals obtainable therefrom is unsatisfactory because of the insufficient activity of the catalyst in the case of relatively high molecular weight olefins. In addition, the phosphine which has the function of forming a complex with the rhodium has to be used in a considerable excess, for example up to a 100-fold excess based on the rhodium.
According to the present invention, a two-phase hydroformylation process for olefins using a novel catalyst has now been found, which process overcomes the above-described disadvantages of the prior art and enables even relatively high molecular weight linear and branched and also cyclic olefins to be hydroformylated in high yield and purity and makes it possible to easily separate the alkanals formed from the reaction mixture, even in a continuous process.
The present invention accordingly provides a process for preparing linear and branched aliphatic monoaldehydes (alkanals) having from 6 to 21 carbon atoms, preferably from 7 to 19 carbon atoms, and cyclic aliphatic monoaldehydes having from 6 to 13 carbon atoms by hydroformylation of linear and branched aliphatic monoolefins (alkenes) having from 5 to 20 carbon atoms, preferably from 6 to 18 carbon atoms, or cyclic olefins having from 5 to 12 carbon atoms, i.e. by reacting such olefins with a carbon monoxide/hydrogen gas mixture, using a rhodium catalyst, wherein the reaction is carried out in a heterogeneous phase by means of a rhodium tri(polyethylene glycolate) of a polyethylene glycol having a mean molecular weight of from 320 to 650, preferably from 350 to 450, particularly preferably 400, at a temperature of from 50 to 150° C., preferably from 80 to 120° C., and at a pressure of from 60 to 200 bar, preferably from 75 to 120 bar. The rhodium tri(polyethylene glycolate) is preferably used in the reaction in the form of a solution in water, in polyethylene glycol having the mean molecular weight indicated or a mixture of this polyethylene glycol with water as solvent.
The rhodium tri(polyethylene glycolate) serving as catalyst is a new compound in which polyethylene glycol is bound as glycolate to the rhodium. The present invention thus also provides rhodium tri(polyethylene glycolate) compounds in which the polyethylene glycol moiety has a mean molecular weight of from 320 to 650, preferably from 350 to 450, particularly preferably a mean molecular weight of 400. The invention further provides solutions of a rhodium (tri)polyethylene glycolate) according to the invention in water, in polyethylene glycol or in a polyethylene glycol/water mixture as solvent, in each case using a polyethylene glycol having a mean molecular weight of from 320 to 650, preferably from 350 to 450, particularly preferably 400.
The novel rhodium tri(polyethylene glycolate) compounds can be assigned the formula (1)
where m
1
, m
2
and m
3
, are identical or different and are each a number from 6 to 15, preferably from 7 to 11, and one third of the sum (m
1
+m
2
+m
3
) is from about 6.8 to about 14.4, preferably from about 7.55 to about 9.8. The rhodium tri(polyethylene glycolate) compound of the invention can advantageously be prepared by heating rhodium(III) chloride trihydrate with the polyethylene glycol in the stochiometric amount (i.e. in an amount which is 3 times the equivalent amount) at a temperature of from 40 to 80° C., preferably from 50 to 65° C., advantageously under a stream of nitrogen and at atmospheric pressure or slightly subatmospheric pressure, with the hydrogen chloride gas formed being removed. The compound is a stoichiometric compound and is readily miscible with water and a polyethylene glycol having a mean molecular weight of from 320 to 650. It can also be synthesized under the same conditions using an excess of polyethylene glycol so as to form the solution of the rhodium tri(polyethylene glycolate) in polyethylene glycol straight away, and this solution can, if appropriate mixed with water, advantageously be used in the hydroformylation reaction.
Olefins which are used in the hydroformylation process of the invention are, for example, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 2-hexene, 2-heptene, 2-octene, 2,4,4-trimethyl-1-pentene, 2,4,4-trimethyl-2-pentene, cyclohexene, cyclooctene and 4-methyl-1-cyclohexene.
The hydroformylation of the invention is generally carried out by placing the rh
Bogdanovic Sandra
Borrmann Thomas
Ritter Uwe
Roesky Herbert
Bierman, Muserlian and Lucas
Hoechst Research & Technology Deutschland GmbH & Co. KG
Padmanabhan Sreeni
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