Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1999-10-27
2001-10-02
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C568S851000, C502S169000, C502S172000, C502S226000
Reexamination Certificate
active
06297188
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a particulate magnesium ethoxide having a coarse particle content, to a process for its preparation and to its use.
2. Discussion of the Background
Processes for preparing magnesium ethoxide have been known for a considerable time. One industrial preparation route is the direct synthesis from metallic magnesium and ethanol. This is described, for example, by H. D. Lutz in Zeitschrift for anorganische und allgemeine Chemie, Volume 356, 1968, pages 132 ff. A catalyst is typically required to start the reaction and, generally, iodine is used as the catalyst. Magnesium ethoxide prepared in this manner disadvantageously includes traces of the starter catalyst, which can have adverse consequences, for example, when the resultant magnesium ethoxide is used as a catalyst precursor for Ziegler catalysts or for book preservation. If catalysts are not used, however, the reaction between ethanol and magnesium is not reliably initiated; and uncontrollable initiation behavior inheres great risk in industrial processes.
In the known processes for preparing magnesium ethoxide, long reaction times are also economically prohibitive. For example, for the complete reaction of ethanol magnesium to occur, reaction times of more than 24 hours are required. If the reaction is terminated prematurely, incompletely reacted metallic magnesium remains in the mixture together with magnesium ethoxide; and separation cannot be reasonably zarried out with standard equipment. In addition, the metallic magnesium impairs the properties of magnesium ethoxide.
Finally, the synthesis of magnesium ethoxide by known processes always produces magnesium ethoxide having considerable amounts of undesirable, undersized grains. This fine grain or dust content likewise impairs the properties of ihe product. This product content can be removed only with a great deal of expense during the preparation of magnesium ethoxide, for example by sieving or classifying, and discarding. It is desirable, therefore, to provide a process which enables the production of magnesium ethoxide in a particularly economical manner.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a magnesium ethoxide having a high coarse particle content in a simple and economic manner.
Another object of the present invention is to provide a process for making a magnesium ethoxide having a high coarse particle content that is simple and economically feasible.
Surprisingly, it has now been found that particulate magnesium ethoxide having a high coarse particle content can be obtained in a simple and economical manner by the present invention, the first embodiment of which relates to EL process for preparing particulate magnesium ethoxide having a coarse grain content, includinig reacting metallic, optionally activated, magnesium with liquid ethanol under pressure at a temperature above 78° C.
Another embodiment of the present invention relates; to a particulate magnesium ethoxide having a coarse grain content, which contains:
<40% by weight of a screening fraction ≦500 &mgr;m and
≧60% by weight of a screening fraction >500 &mgr;m.
The process according to the present invention can be reliably started in a simple and economical manner and without a catalyst contaminating the product. In addition, the present process can completely avoid the unwanted residue of incompletely reacted metallic magnesium. The reaction times of the present process are generally markedly less than 24 hours, which inheres a particularly economical mode of operation. Furthermore, a product having a comparatively low content of unwanted undersize grain or dust content is obtained.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description of the preferred embodiments.
Preferably, in the process according to the present invention, metallic, optionally activated, magnesium is brought into contact with anhydrous ethanol in the liquid phase under pressure at a temperature above the boiling temperature of ethanol at atmospheric pressure (78° C.), the mixture is reacted to completion and the product is isolated.
Preferably, in the reaction according to the invention, liquid ethanol and solid metallic magnesium are brought into contact and heated under pressure to a temperature above 78° C. in such a manner that liquid ethanol is available as a reaction partner, and the hydrogen that is formed is ejected from the reaction space.
Preferably, to carry out the reaction according to the invention, dried ethanol is used in excess, so that ethanol can simultaneously serve as solvent. The magnesium ethoxide arising in the reaction according to the invention is then preferably isolated by filtration or by concentrating the product mixture at a temperature in the range from 0° to 180° C. under reduced pressure. More preferably, the isolation temperature ranges from 5° to 150° C., even more particularly preferably 10° to 125° C., and most preferably 15° to 100° C. Prior to product isolation, the resulting product mixture can be preferably cooled to a temperature of 20° to 78° C. More preferably, the cooling temperature ranges from 25° to 75° C., even more particularly preferably 30° to 70° C., and most preferably 35° to 65° C.
Preferably, both the reaction according to the invention and the isolation of the magnesium ethoxide according to the invention are carried out under a protective gas. A CO
2
-free protective gas which has been dried in a manner known per se is preferably used, for example nitrogen or argon. Nitrogen, dried and CO
2
-free, is most preferred.
Most preferably, the present invention relates to a process for preparing particulate magnesium ethoxide having a coarse grain content, wherein metallic, optionally activated magnesium is reacted with ethanol in the liquid phase and subsequently the magnesium ethoxide is isolated, which includes carrying out the reactio:, under pressure at a temperature above 78° C.
Preferably, in the process according to the invention, the reaction temperature is set to a value of from >78 to 200° C., particularly preferably from 80 to 130° C., very particularly preferably from 100 to 130° C., and the pressure in the reaction space is set to a value above 1 bar absolute, particularly preferably to a value of from 2 to 6 bar absolute.
The metallic magnesium used in the process according to the invention preferably has a particle size of from 20 to 5000 &mgr;m. Preferably, it is used as pure magnesium metal. However, before the reaction, it can also be activated, for example by etching.
To start the reaction, a catalyst may be preferably added to the reaction mixture. The catalyst is preferably made of an inorganic or organic halogen compound, preferably a mercury halide, an inorganic or organic acid, such as HCl or acetic acid, or an alkyl orthoformate, such as tetraethyl orthoformate (TEOF).
Preferably, in the process according to the invention, the reaction is started by raising the temperature briefly to above 78° C., and more preferably >90° C. Preferably, in the further course of the reaction, the peak of hydrogen development proceeds at a temperature below 90° C.; the resulting hydrogen is conducted away from the reaction space; and the remaining reaction proceeds at a temperature above 90° C., likewise with ejection of the hydrogen formed. Preferably, the reaction has generally proceeded quantitatively after 16 hours, so that in an advantageous manner, virtually no magnesium metal residues remain in the product mixture. The product is generally isolated from the product mixture in the manner described above.
Particulate magnesium ethoxide prepared according to the invention advantageously has a high content of coarse grains. The grain content is generally determined under dry protective gas by screening analysis according to t
Frings Albert-Johannes
Horn Michael
Jenkner Peter
Monkiewicz Jaroslaw
Rauleder Hartwig
Degussa-Huels Aktiengesellschaft
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pasterczyk J.
Wood Elizabeth D.
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