Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1998-08-03
1999-12-21
Barts, Samuel
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
564491, 564492, C07C20900
Patent
active
060051450
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to new metal compounds, to a process for the preparation of these metal compounds and to their use as catalysts.
Hydrogenation catalysts based on nickel or on cobalt represent an important class among the many metal compounds used in particular as catalysts in various chemical reactions. These hydrogenation catalysts based on nickel or on cobalt are in particular Raney nickel and Raney cobalt, which are widely used in industry in many hydrogenation reactions.
Catalysts of this type, which are very efficient and which possess very broad fields of application, nevertheless exhibit a number of disadvantages and a number of limitations of use.
First of all, they are prepared by attack, using a strong base, on an alloy containing nickel or cobalt and a high proportion of aluminium.
Such a preparation therefore necessarily involves the generation of large amounts of basic aqueous effluents containing aluminates, the treatment of which effluents is essential.
Another limitation on the use of Raney nickel and cobalt is due to the fact that their reduced form is pyrophoric; it must be handled with care and can only be used protected, either in the form of a suspension or liquid or in the form coated in a protective solid. Use in a stationary bed on an industrial scale is thereby rendered difficult.
Finally, a progressive deactivation of Raney nickel or cobalt is observed, whereas no efficient means of regeneration is known. One of the hypotheses which seems accepted in explaining this deactivation, in particular in a medium containing water and more specifically in basic medium, is the progressive oxidation of the residual aluminium to aluminate, which coats the active surface of the nickel or of the cobalt.
Another form of metal catalyst has been used in order to overcome certain abovementioned disadvantages of Raney catalysts: the metals are deposited on a support. Thus, Patent EP-A-0,566,197 describes hydrogenation catalysts based on nickel and/or on cobalt deposited on a solid support, such as an aluminium silicate, an alumina or a silica, preferably with a cocatalyst, such as a non-acidic alkali metal or alkaline-earth metal oxide or salt.
In this type of catalyst, the homogeneity of the distribution of the active metal in the solid support is not always very good. In addition, the presence of a support can, in certain cases, limit the activity of the catalyst and, in any event, dilutes the active metal phase.
Thus, in Patent EP-A-0,566,197, the Examples show that the active metal content of the supported catalysts does not exceed 20% and is often 5%. Finally, the method of deposition of the active metal, by impregnation of the support, can result in partial dissolution of the active metal in the reaction mixture, when the catalyst is used.
Patent FR-A-2,091,785 describes catalysts composed of active metal oxides, of active metals or of active metal oxides and of support materials, comprising magnesium, nickel, cobalt; divalent copper, zinc, manganese and/or iron and trivalent aluminium, chromium and/or iron. The proportion of divalent and trivalent metals in these catalysts is, in practice, 6 atoms of divalent metals per 2 atoms of trivalent metals.
These catalysts contain essentially aluminium as trivalent metal and magnesium, nickel and cobalt, sometimes in combination with other metals, as divalent metals. They can be used for the dehydrogenation of secondary alcohols or of monoolefins, isomerization or dealkylation reactions or for the hydrogenation of nitro compounds.
The new metal compounds according to the invention possess, when they are used as catalysts, in particular as hydrogenation catalysts, an efficiency of the same order as that obtained with Raney nickel or cobalt, while not exhibiting the disadvantages indicated above, in particular as regards their deactivation and their regeneration.
In addition, as they do not contain a support, they are composed virtually only of active compounds.
These metal compounds are more precisely compounds containing one or a number
REFERENCES:
patent: 5232887 (1993-08-01), Blaise et al.
Cordier Georges
Popa Jean-Michel
Barts Samuel
Rhone-Poulenc Fiber and Resin Intermediates
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