Intermetallic ruthenium tin-catalyst for use in aldehyde synthes

Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing

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502326, 502261, 502349, 502352, C07C 4500

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059732105

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BRIEF SUMMARY
The present invention relates to a process for preparing aldehydes and derivatives thereof by vapour-phase reduction in the presence of hydrogen, acids, esters or carboxylic anhydrides.
It relates more particularly to a process for the synthesis of aldehydes by vapour-phase reduction of acids, esters or derivatives thereof in the presence of a bimetallic catalyst of the ruthenium/tin type. It also relates to a catalyst and to its use for the selective reduction of carboxylic derivatives to aldehydes.
The present process relates more particularly, as substrate, to carboxylic compounds which carry halogen, and especially fluorine, and are capable of undergoing hydrogenolysis in the course of reduction.
It is known in the prior art to prepare saturated aliphatic or aromatic aldehydes by reduction of the corresponding esters or acids using a catalyst chosen from the oxides of cerium, zirconium, uranium, praseodymium and yttrium at a temperature of between 350 and 450.degree. C. (U.S. Pat. No. 4,328,373).
Owing to the temperature conditions required for their implementation, these processes do not permit preparation of aldehydes from thermally unstable acids.
The patent application published under the U.S. Pat. No. 2,682,949 described a technique using alloys of ruthenium and tin which permits a significant improvement.
Catalysts of the Ru/Sn/B type had already been described in the literature [J. Cat., 121, 165-173 (1990)], as had their use for the liquid-phase reduction of unsaturated fatty acids to unsaturated fatty alcohols [J. Cat., 121, 174-182 (1990)].
Certain problems remained unresolved. For a certain number of substrates, giving rise to secondary reactions, the choice of the support and of the manner in which the surface catalytic layer was formed was found to be critical. The problem is particularly acute in the case of the reduction of certain halogenated derivatives, whose lysis by hydrogen leads to particularly aggressive acids such as, for example, hydrofluoric acid.
These acids are capable of destroying certain supports and interfere with the desired reaction. A further risk lies in a catalysis of the reduction of the aldehyde to alcohol.
For this reason, one of the aims of the present invention is to provide a composition which can be used as catalyst and permits improved resistance to products of any secondary reaction(s).
Another aim of the present invention is to provide a composition of the above type which avoids the secondary reactions or reduces their relative importance.
These and other aims which will become evident below are achieved by a composition which can be used as reduction catalyst and which comprises a support whose constituent material comprises at least one oxide chosen from oxides which are inert or capable of being made inert relative to the reaction mixture and a metallic phase at least partially covering the said support, of which at least part comprises an intermetallic ruthenium-tin compound at least some of which is in the form of the defined compound Ru.sub.3 Sn.sub.7.
The phase containing the ruthenium and the tin advantageously has an Sn/Ru atomic ratio which is at least equal to 2/3, advantageously to 3/2, preferably to 7/3. Moreover, it is preferable for the Sn/Ru atomic ratio to be at most equal to 3, advantageously to 5/2.
The said phase covering at least part of the said support advantageously contains at least 50%, more advantageously 80%, preferably at least 90%, of the said intermetallic phase.
Finally, it is desirable for at least 90%, advantageously at least 95%, preferably 98%, of the ruthenium present on the support to be in the form of the said phase covering the said support.
The invention is more particularly suitable for the preparation of aldehydes of general formula: ##STR1## in which R represents a hydrogen atom or an optionally substituted hydrocarbon radical containing 1 to 40 carbon atoms which can be a linear or branched, saturated or unsaturated acyclic aliphatic radical or a monocyclic or polycyclic, saturated, unsaturated or aromatic carb

REFERENCES:
patent: 5393919 (1995-02-01), Shinoda
patent: 5476827 (1995-12-01), Ferrero
CA;86:198283 abst of "Bonding in iron--tin and ruthenium-tin mixtures", Heinrich, J Less Common Met, 52(1), pp. 87-91. 1977.

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