Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-12-21
2002-11-26
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S862000, C568S864000, C568S881000, C568S885000
Reexamination Certificate
active
06486366
ABSTRACT:
INTRODUCTION AND BACKGROUND
The invention is directed toward an improved method for producing alcohols from carbonyl compounds that includes catalytic hydrogenation of carbonyl compounds with hydrogen or hydrogen-containing gases in the presence of a molded hydrogenation catalyst of Raney type. The invention especially concerns the production of sugar alcohols. The method allows the use of distinctly lower amounts of catalyst in the production of alcohols while having the same or higher yields than with the methods known up to now.
In accordance with this invention all organic compounds that contain a C═O group, including those compounds that contain an O═C—O group, are seen as carbonyl compounds. Thus, ketones, aldehydes, carboxylic acids, carboxylates, carboxylic anhydrides, carboxylic acid esters, carboxylic acid amides and carboxylic acid halides are meant by the term carbonyl compounds.
Alcohols are a decidedly important class of substances in organic chemistry. They serve, for example, as starting materials for the production of solvents, surfactants, perfumes, flavorings, additives, drugs and other organic substances. Moreover, they are very important as monomers for various plastics. Sugar alcohols are widely used, for example, as sugar substitutes.
In the production of alcohols by hydrogenation [of] carbonyl compounds Raney catalysts are frequently preferred because of their good catalytic properties and because they are significantly 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 out by alkalis. Chiefly aluminum is used as the alkali-soluble alloy component, but other metals like 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.
Numerous inventions for producing alcohols from carbonyl compounds by catalytic hydrogenation with Raney catalysts are known. In each case according to the process, various Raney catalysts, more precisely catalysts with different active metals or combinations of metals, are used.
EP 0 724 908 describes a method for producing alcohols from carbonyl compounds in which Raney catalysts whose catalytically active component is a noble metal are used as hydrogenation catalysts. The catalysts are used in powder form.
Raney catalysts in powder form have the disadvantage that they can only be used in batch processes, and have to be separated from the reaction medium after the catalytic conversion, at high cost. Because of this, among other things, it is preferable to carry out the production of alcohols by hydrogenation of carbonyl compounds using molded Raney catalysts and as far as possible in a continuous process. Fixed bed catalysts, which also have to have sufficient strength for continuous operation, in addition to having good catalytic activity, are necessary for this purpose.
JP 07206737 A2 describes another method for producing alcohols by catalytic hydrogenation of carbonyl compounds. The catalysts used in this method are spherical Raney catalysts based on copper, which preferably also contain iron and, as leachable component, aluminum. The method can be run using a fixed catalyst bed.
EP 0 773 063 describes a method for producing sugar alcohols using a fixed catalyst bed in which a Raney nickel catalyst is used. The use of a nodular Raney catalyst produced by dripping the liquid alloy into a liquid, preferably water, is important in accordance with this invention.
Sugars are hydrogenated by the method described in EP 0 854 149, likewise continuously and using a fixed catalyst bed. The catalysts used with this method are produced by mixing a catalyst alloy and a metal that serves as binder and then pressure molding this mixture to form molded pieces. After drying and calcination, these molded pieces are activated by treatment with aqueous alkalis. This produces a catalyst that consists of a catalytically active shell and a largely catalytically inactive core. It is necessary to use the binder in order to give the catalyst the necessary mechanical stability.
A serious disadvantage of the methods noted in the documents JP 07206737 A2, EP 0 773 063 and EP 0 854 149 for producing various alcohols by hydrogenation of carbonyl compounds lies in the high bulk density of the Raney catalysts. Because of this, these catalysts have relatively low activity with respect to the weight of catalytically active metal that is used.
Another disadvantage is that the reactors that are used have to have high stability. This requires additional investments in the construction and operation of a hydrogenation plant.
Metal catalysts in the form of hollow bodies, preferably in the form of hollow spheres, are described in DE 199 33 450.1. These catalysts have a low bulk density, from 0.3 to 1.3 g/mL. Besides the catalysts, the use of these catalysts in hydrogenation reactions is also claimed. The examples [in this document] give activity tests for 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 when a comparison catalyst is used. However, the use of the described catalysts for production of alcohols by hydrogenation of carbonyl compounds is not mentioned.
For this reason the task of this invention is to develop a method for producing alcohols from carbonyl compounds by catalytic hydrogenation in which the disadvantages of the said methods do not arise. Another goal of the invention is to achieve the same or better starting material conversion rates by comparison with the known methods while using less catalyst material.
The task underlying the invention is solved by the fact that alcohols can be produced by hydrogenation of carbonyl compounds with distinctly higher conversion rates per unit of weight of catalyst if hollow Raney catalysts are used than with the known catalysts. This observation is surprising in that one cannot necessarily assume that the hollow Raney catalysts achieve the necessary activities in the particular case of the hydrogenation of carbonyl compounds.
The object of the invention is a method for producing alcohols by catalytic hydrogenation of carbonyl compounds with hydrogen or hydrogen-containing gases in the presence of a molded hydrogenation catalyst of the Raney type, which is characterized by the fact that the Raney catalyst is in the form of hollow bodies. This method has the advantage that alcohols can be produced with the same or higher yields while using clearly lesser amounts of catalyst than was possible up to now according to the prior art.
SUMMARY OF THE INVENTION
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 and a leachable metal, preferably aluminum, an organic binder and optionally an inorganic binder, water and promoters is deposited onto spheres that consist of a thermally removable material. Preferably, polystyrene foam spheres can be used. The deposition of the mixture containing the metal alloy onto the polymer spheres can preferably be carried out in a fluidized bed. Preferably, 0-10 wt % polyvinyl alcohol and/or 0-3 wt % glycerol can be used as organic binders. The coated polymer foam spheres are then calcined at a temperature above 300° C., preferably in a range from 450 to 1300° C., in order to remove the polymer foam thermally and to sinter the metal. In this way the hollow spheres obtain a stable shape. After calcination the hollow spherical catalysts are activated by treatment with basic solutions, preferably alkali or alkaline earth hydroxides in water, more
Berweiler Monika
Ostgard Daniel
Röder Stefan
Degussa - AG
Shippen Michael L.
Smith , Gambrell & Russell, LLP
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