Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1998-05-05
2001-01-30
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S484000, C502S227000, C502S230000, C502S326000, C502S261000, C502S349000, C502S352000
Reexamination Certificate
active
06180830
ABSTRACT:
This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR96/01762, filed on Nov. 08, 1996.
The present invention relates to a new process for the preparation of a bimetallic ruthenium/tin catalyst.
EP-A-0 539 274 described a process for the preparation of aldehydes and derivatives thereof according to a process which consists in carrying out the reduction, in the vapour phase in the presence of hydrogen, of carboxylic acids, esters or anhydrides, in the presence of a bimetallic ruthenium/tin catalyst.
Although catalysts of the ruthenium/tin type containing boron are suitable for performing the process described, the catalysts of particular interest are boron-free bimetallic catalysts containing tin and ruthenium, which contain ruthenium and tin used in such quantities that the molar ratio of tin/ruthenium is at least 2, preferably between 2 and 10 inclusive and even more preferably between 2 and 6 inclusive.
It is possible to use different types of catalysts which may or may not be supported.
Generally speaking, ruthenium represents between 0.1 and 50% of the weight of the catalyst.
If a solid catalyst is used, the ruthenium represents 10% to 50% of the weight of the catalyst.
In a preferred embodiment, however, a catalyst in the supported form is used. To this end, the support may be chosen in particular from metal oxides such as aluminium, silicon and/or zirconium oxides, or from carbons optionally activated by a well known treatment with nitric acid, acetylene black, or resins.
If the catalytic phase is deposited on a support, the ruthenium content of the catalyst is advantageously between 0.1 and 20.0% by weight, and even more preferably between 0.5 and 3.0% by weight.
A method of preparing said catalysts described in EP-A-0 539 274 consists in mixing ruthenium III chloride and tin II chloride then adding the solid support.
The disadvantage of this process is that it does not make it possible to obtain a perfectly homogeneous catalyst that can be produced on an industrial scale. Indeed, tin II chloride partially hydrolyses and precipitates on the surface of the support whereas ruthenium III chloride penetrates the pores of the support. As a result, the support is not impregnated uniformly by the precursors of the ruthenium and tin metals and the catalyst obtained is not very homogeneous.
The object of the present invention is to provide a process for the preparation of said catalyst which makes it possible to overcome the above-mentioned disadvantages.
A process has now been found, and this constitutes the subject matter of the present invention, for the preparation of a bimetallic ruthenium/tin catalyst, characterised in that it consists in carrying out the reduction of a ruthenium complex having an electrovalency of −4 and a coordination number of 6, the ligands being either a halogen atom or an anion of tin halide.
According to a preferred embodiment of the process of the invention, the reduction of a complex corresponding more particularly to the following formula (A) is carried out:
[Ru(SnX
3
)
6−n
X
n
]4
−
(A)
in which formula (A) X represents a halogen atom, preferably an atom of chlorine or bromine, and n is a number ranging from 0 to 2, and preferably equal to 1.
In the process of the invention, the following complexes are used in preference:
[Ru(SnCl
3
)
6
]
4−
[Ru(SnCl
3
)
5
Cl]
4−
[Ru(SnCl
3
)
4
Cl
2
]
4−
It was found that the catalyst obtained was of good quality if it was prepared according to the process of the invention as specified.
A halogenated complex of ruthenium and tin corresponding preferably to formula (A) is therefore used in the process of the invention.
According to a preferred embodiment of the invention, the preparation of said complex is carried out by reaction of a ruthenium halide and of a tin halide in the presence of an acid.
To this end, the starting product is a ruthenium III halide, preferably a ruthenium III chloride. It is also possible to start with a ruthenium IV salt, but there is no additional advantage, particularly as it is more expensive.
In preference, therefore, a ruthenium III halide, either in the anhydrous or hydrated form, is used.
It is desirable that said compound does not contain too many impurities. Advantageously, the compound used is free from heavy metals and has a chemical ruthenium purity of 99% with respect to the other metals.
It is possible to use the commercial form of ruthenium chloride RuCl
3
×H
2
O containing about 42 to 43% by weight of ruthenium without any disadvantages.
With regard to the tin salt, a tin halide is used in which the tin has an oxidation number lower than that of the ruthenium.
A tin II halide is used, preferably a tin II chloride.
It is also possible to use the salt in the anhydrous or hydrated form. In preference, the commercial tin salt having the formula SnCl
2
.2H
2
O is also used.
Most often, the halides of said metals are used in the form of an aqueous solution. The concentration of these solutions is such that a homogeneous solution capable of being impregnated on a support is obtained.
With regard to the quantities of the above-mentioned metal halides used, said quantity is determined in such a way that the ratio between the number of moles of ruthenium halide and the number of moles of tin halide is between 0.10 and 0.5, and preferably between 0.15 and 0.35. It should be noted that the lower limit is not critical because there is no disadvantage in using an excess of tin halide.
The preparation of the complex by reaction of the ruthenium and tin halides takes place in the presence of an acid, the function of which is to solubilise the tin halide and to keep the complex formed soluble.
It is possible to use any strong, preferably mineral acid, but it is preferable to use the hydracid of which the halide is identical to the halide used in the ruthenium and tin salts.
Thus, hydrochloric acid is generally the preferred acid.
The quantity of acid used is preferably at least 1 mole of acid per mole of ruthenium halide, and more particularly between 1 and 5 moles of acid per mole of ruthenium halide. The upper limit is not critical and may be exceeded without disadvantage. The preferred quantity of acid is in the region of 3 moles of acid per mole of ruthenium halide.
From a practical point of view, the preparation of the complex is carried out by mixing, in any order, the ruthenium halide (preferably ruthenium III chloride), the tin halide (preferably tin II chloride) and the strong acid (preferably hydrochloric acid).
The reaction mixture is brought to a temperature from 20° C. to 100° C., preferably between 70° C. and 90° C.
The duration of this operation may vary widely and it may be specified by way of illustration that a period between 1 and 3 hours is perfectly suitable.
The complex forms fairly rapidly but it remains in solution.
Afterwards, if necessary, the temperature is restored to ambient temperature, that is, to a temperature most open between 15° C. and 25° C.
It is thus possible to envisage two variants of the process depending on whether the desire is to obtain a catalyst in the solid or supported form.
In the first case, hydrolysis of the complex obtained is carried out by adding water.
The amount of water used is not critical; it generally represents 1 to 100 times the weight of the complex.
After this hydrolysis, the complex precipitates.
It may be separated by conventional solid/liquid separation techniques, preferably by filtration.
This separation is generally carried out at ambient temperature.
The precipitate obtained may optionally be dried then reduced according to the conditions defined below.
If the support is in the form of a powder, such as, for example, alumina or silica, another variant consists in adding it to the solution of the complex obtained, then carrying out hydrolysis as described above, then separating the solid obtained, preferably by filtration, and mixing it and extruding it. A formed catalyst is t
Padmanabhan Sreeni
Rhodia Chimie
Seugnet Jean-Louis
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