Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-12-21
2003-11-18
Davis, Brian (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S492000, C564S493000
Reexamination Certificate
active
06649799
ABSTRACT:
INTRODUCTION AND BACKGROUND
The invention is directed toward an improved method for producing primary and/or secondary amines from imines and nitrites, which includes the catalytic hydrogenation of nitriles or imines with hydrogen or hydrogen-containing gases in the presence of a molded hydrogenation catalyst of Raney type. The invention includes in particular the production of monoamines and diamines and the production of aminonitriles. The method allows the use of distinctly lower amounts of catalyst in the production of the amines while having the same or higher yields than with the previously known methods.
Nitriles can be catalytically reduced to amines with hydrogen. As is known, in this hydrogenation the intermediate step usually goes through an imine. For this reason one can assume that the hydrogenation of nitrites always also includes the hydrogenation of imines.
Amines are a decidedly important class of substances in organic chemistry. For example, they serve as starting materials for the production of solvents, surfactants, bactericides, anticorrosion agents, foam suppression agents, additives, pharmaceuticals or dyes. Moreover, they are very important in the production of polyamide and polyurethane plastics.
In the production of amines by hydrogenation of nitrites and imines Raney catalysts are frequently preferred because of their good catalytic properties and the fact that they are considerably easier to make than supported catalysts. Raney catalysts, which are also called activated metal catalysts, consist of an alloy of at least one catalytically active metal and at least one metal that can be leached with alkalis. Chiefly aluminum is used for the alkali-soluble alloy component, but other metals such as zinc and silicon can also be used. By adding alkalis to the alloy the leachable component is dissolved out, due to which the catalyst becomes activated.
Many inventions for production of amines from nitriles or imines by catalytic hydrogenation with Raney catalysts are known. Here different Raney catalysts, more precisely catalysts with different active metals or metal combinations, are used, in each case according to the process.
For example, U.S. Pat. No. 5,777,166 describes a method for hydrogenation of nitrites to amines using doped and alcoholate-treated Raney nickel catalysts. It is clear from the examples that the described method is preferably carried out in a batch process using catalysts in powder form. In contrast, DE 223 81 53 describes the hydrogenation of fatty acid nitriles to fatty acid amines by means of cobalt catalysts. In this process, too, the hydrogenation is carried out with the aid of powdered Raney catalysts.
Catalysts of Raney type in powder form have the disadvantage that they can only be used in a batch process and after the catalytic conversion have to be separated from the reaction medium, at high cost. For this reason among others, it is preferred to produce amines by hydrogenation of nitrites and imines using molded Raney catalysts and as far as possible to carry out this production in a continuous process. Fixed bed catalysts that, besides having good catalytic activity, also have to have sufficient strength for continuous operation, are needed for this purpose.
Combinations of metals are also known in Raney catalysts. U.S. Pat. No. 6,087,296 describes a method for hydrogenation of unsaturated organic compounds using a Raney catalyst that can contain iron, cobalt and other metals and promoters.
DE Patent 195 40 191 describes a two-step method for producing isophoronediamine. In this process isophorone is first converted with ammonia to isophoronenitrileimine in the presence or absence of an imination catalyst and the resulting product mixture is hydrogenated to isophorphonediamine while adding hydrogen. Isophoronenitrileimine contains both a hydrogenatable cyano group and a hydrogenatable imino group. A molded Raney catalyst based on cobalt serves as hydrogenation catalyst. The catalyst contains, besides the catalyst alloy of cobalt and aluminum, additional metallic cobalt, which serves as a binder to produce the necessary stability of the molded article. The disadvantage of this method lies in that the cobalt added as binder has only slight catalytic activity, so that the activity of the catalyst is reduced in comparison with binder-free catalysts. In this way it is necessary to use relatively high amounts of catalysts in order to achieve good product yields.
This disadvantage is avoided in the production of isophoronediamine as described in EP 0 880 996. A molded cobalt catalyst of Raney type, which before activation by leaching out the aluminum consists exclusively of a cobalt-aluminum alloy, is used for hydrogenation. This catalyst has the advantage over the catalyst used in DE 19540191 that it has a distinctly lower bulk density of only 1.2 kg/L. In spite of the lower bulk density hydrogenation with the catalyst consisting only of the catalyst alloy leads to slightly higher yields for the same catalyst weight. The disadvantage of the method described in EP 0 880 996 lies in the fact that the catalyst that is used still has quite high bulk densities relative to fixed bed catalysts that are not of Raney type.
DE 199 33 450.1 describes metal catalysts that are in the form of hollow bodies, preferably in the form of hollow spheres. These catalysts have a low bulk density, from 0.3 to 1.3 g/mL. Besides the catalysts, their use in hydrogenation reactions is also claimed. The examples give activity tests for the hydrogenation of nitrobenzene to aniline, in which the hydrogen uptake and thus the activity of the catalyst per gram of catalyst is clearly higher when the hollow spherical catalysts are used than with comparison catalyst. The use of the described catalysts for the production of amines by hydrogenation of nitrites and imines, however, is not mentioned.
For this reason the task of this invention was to develop a method for producing amines from nitrites and imines by catalytic hydrogenation, in which the hydrogenation is carried out with a molded hydrogenation catalyst of Raney type that, while having a catalytically active layer of sufficient strength and considerably lower bulk density than comparable catalysts, has the same or better hydrogenation activity than the previously used catalysts. Another goal of the invention is to achieve the same or better starting material conversion rates than with the known methods while using less catalyst material.
SUMMARY OF THE INVENTION
The underlying invention showed that the production of amines by hydrogenation of imines or nitrites by means of the hollow Raney catalysts described in DE 199 33 450.1 is possible with clearly higher conversion rates per unit of weight of catalyst than with comparable catalysts. This observation is surprising in that one cannot necessarily assume that the hollow Raney catalysts will achieve the necessary activities in the particular case of the hydrogenation of imines and nitrites.
The invention thus consists of a method for producing amines by catalytic hydrogenation of imines and/or nitrites, in which a molded Raney catalyst is used as hydrogenation catalyst, which is characterized by the fact that the Raney catalyst is in the form of hollow bodies. This method has the advantage that imines can be produced with the same or higher yields while using clearly smaller amounts of catalyst than is possible up to now according to the prior art.
The advantage underlying this invention is achieved through the use of Raney catalysts in the form of hollow bodies. The production of the catalysts used in the method in accordance with the invention can be carried out in correspondence with the method described in DE 199 33 450.1. According to this method a mixture of an alloy powder of a catalytically active metal with a leachable metal, preferably aluminum, an organic binder and optionally an inorganic binder, water and promoters is applied to spheres that consist of a thermally removable material. Preferably, polystyrene foam spheres can be used. The applic
Berweiler Monika
Ostgard Daniel
Röder Stefan
Davis Brian
Degussa - AG
Smith , Gambrell & Russell, LLP
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