Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1996-05-16
1999-07-27
Lewis, Michael
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D30100
Patent
active
059292601
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to catalysts composed of surface.
The present invention furthermore relates to a process for the preparation of these catalysts, their use and a method for removing these catalysts from reaction solutions.
2. Description of the Related Art
Reactions in solution with homogeneous or suspended catalysts are widely encountered in the chemical industry. However, the removal and, if required, recycling of these catalysts presents difficulties in many cases. If catalysts dissolved in the reaction solution, ie. homogeneous catalysts, are used, the products are usually separated from the catalysts by distillation and the catalysts remain in the bottom product of the distillation. The catalysts are frequently deactivated during this procedure and can be reused only after being worked up by a complicated process. In the case of thermally unstable products, this method of removal by distillation leads to a deterioration in the product quality owing to decomposition reactions. In these cases, the catalyst may alternatively be removed, for example, by extraction or by adsorption, for example on active carbon. Attempts have also been made to achieve separability of product and catalyst by heterogenization, ie. by binding the catalysts to finely divided substances which are insoluble in the reaction mixture. However, the filterability of such heterogenized catalysts is often poor.
In the case of suspension catalysts, the highest catalytic activity is frequently achieved with small catalyst particles having a high specific surface area. Owing to the particle size, these particles, too, are difficult to remove from the reaction mixture by simple filtration, so that the technically complicated separation methods described above have to be used.
A possible method for removing metallic suspension catalysts containing the magnetic elements iron, cobalt and nickel entails removal in a magnetic field (magnetic filter) (Journal of Magnetism and Magnetic Materials 85 (1990), 285). However, this method is limited to magnetic metals and, in the case of larger particles, also has the difficulty that the particles agglomerate to form larger particles as a result of permanent magnetization.
The immobilization of enzymes by binding to magnetic particles is described, for example, in EP-A 125995. However, the use of these enzymes is limited to mild reaction conditions under which the enzymes bound in this manner are chemically stable.
SUMMARY OF THE INVENTION
EP-A 21 854 describes magnetic catalyst particles having a size of about 800 .mu.m for a fluidized-bed process for a reformer process. The catalytically active metal compounds such as hexachloroplatinic acid can be applied, for example by impregnation, to spray-dried mixtures of Al.sub.2 O.sub.3 and stainless steel.
EP-A 115 684 concerns magnetizable iron particles having a size of from 150 to 300 .mu.m which can be used, without application of a coating or being silvercoated, for catalysis in fluidized beds.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
It is an object of the present invention to provide metal-containing catalysts for liquid-phase reactions, which catalysts can be removed from the reaction mixture in a technically simple manner.
We have found that this object is achieved by the catalysts described above. We have furthermore found a process for their preparation, their use and a method for removing these catalysts from reaction mixtures.
The core of the novel catalysts consists of a magnetizable particle. Magnetizable particles are to be understood as being those particles which are magnetic in an external magnetic field. In general, such substances have a saturation magnetization of from 20 to 200, preferably from 30 to 100, nTm.sup.3 /g. The size of the magnetizable particles can be chosen within wide limits. If, however, permanent magnetization of these particles by an external magnetic field is to be avoided, particles having a diameter of from 5 to 100 nm are used. The size of
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Journal of Magnetism and Magnetic Materials, vol. 83, 1990--pp. 285-289 (no month).
Henkelmann Jochem
Kormann Claudius
Schwab Ekkehard
Wettling Thomas
BASF - Aktiengesellschaft
Hendrickson Stuart L.
Lewis Michael
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