Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2000-12-05
2001-06-05
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
Reexamination Certificate
active
06242627
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for preparing primary aminoorganosilanes. More particularly, the present invention relates to a process for preparing a primary aminoorganosilane by the catalyzed reaction of a cyanoorganosilane with hydrogen.
A process of the foregoing type is described in U.S. Pat. No. 5,117,024. In accordance with this process, a cyanoorganosilane is reacted with hydrogen gas in the presence of a supported cobalt catalyst at a temperature of from about 100EC to 200EC and a pressure within a range of from about 200 psig to 2000 psig. The process is said to provide near quantitative selectivity for the desired primary aminoorganosilane without the production of hydrogen chloride and without the addition of ammonia and solvent systems as in then prior known processes.
A significant disadvantage to the process for making primary aminoorganosilanes described in U.S. Pat. No. 5,117,024 lies in its use of a supported cobalt catalyst. Such a catalyst is typically supplied in the passivated state, i.e., the cobalt particles are covered with a layer of oxide, in order to reduce the hazard of spontaneous combustion of the metal in an oxygen-containing environment such as air. Before the catalyst can be used, it must be activated, generally by reduction with hydrogen at fairly high temperatures, e.g., 500EC and even higher.
SUMMARY OF THE INVENTION
In accordance with the present invention, a process for preparing a primary aminoorganosilane is provided which comprises reacting a cyanoorganosilane with hydrogen under hydrogenation conditions and in the substantial absence of water in the presence of a catalytically effective amount of sponge cobalt to produce the primary aminoorganosilane.
In contrast to a process which employs a passivated cobalt catalyst which is believed to be the case with the process of U.S. Pat. No. 5,117,024 discussed supra, there is no need to activate the sponge cobalt catalyst employed in the process of this invention. Thus, the process of this invention utilizes the catalyst directly and without any need for a prior treatment which would only add to the complexity and expense of the process.
It is further a feature of the invention to conduct the hydrogenation of a cyanoorganosilane to provide the corresponding primary aminoorganosilane employing any suitable catalyst wherein an alkali metal alkoxide is present in the reaction medium to inhibit or suppress the formation of secondary aminoorganosilane.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The starting cyanoorganosilane reactant herein is preferably one possessing the general formula
R
1
3
Si R
2
CN
in which case the product primary aminoorganosilane will conform to the general formula
R
1
3
Si R
2
CH
2
NH
2
wherein each R
1
group is independently selected from the group consisting of alkyl and alkoxy radical of from 1 to about 10 carbon atoms, and R
2
is a divalent hydrocarbon radical of from 1 to about 20 carbon atoms.
The R
1
radical can be, for example, methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, isobutyl, pentyl, dodecyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy, phenyl and phenoxy. R
1
is preferably selected from the group consisting of methyl, methoxy, ethyl and ethoxy.
The divalent radical R
2
can be, for example, a divalent radical of an alkane, cycloalkane, or an aromatic or aralkane compound. Thus, divalent radical R
2
can be, for example, a linear or branched alkylene group such as methylene, ethylene, 1,2-propylene, 1,3-propylene, 2-methyl-1,3-propylene, 3-methyl-1,3-propylene, 3,3-dimethyl-1,3-propylene, ethylidene or isopropylidene, a cycloalkylene group such as cyclohexylene or cycloheptylene, an arylene group such as phenylene, tolylene, xylylene or naphthylene, or the divalent group —C
6
H
4
—R
3
— in which R
3
is 10 methylene, ethylene, ptopylene, etc.
Examples of cyanoorganosilanes which can be hydrogenated by the process of this invention include 2-cyanoethyltrimethysilane, 2-cyanoethyldimethylmethoxysilane, 2-cyanoethylmetbyldimethoxysilane, 2-cyanoethyltrimethoxysilane, 2-cyanoethyldimethylsilane, 2yanoethyldimethoxylsilane, 2-cyanoethyltriethoxysilane, 2-cyanoethyldimethylethoxysilane, 2-cyanoethylphenymethylsilane, 2-cyanoethylphenylmethoxysilane, 3-cyanomethyltriethoxysilane, 3cyanopropyltrtethylsilane, 3-cyanopropylmethyldimethylsilane and 3-cyanopropylmethyldimethoxysilane.
The reaction of the starting cyanoorganosilane with hydrogen in the presence of sponge cobalt catalyst to provide the desired primary aminoorganosilane in accordance with this invention can be carried out in known and conventional high pressure reactors. The reactor can be, for example, a fixed bed, stirred-bed or fluidized-bed type reactor. The process can be run as a batch process or as a continuous process. A stirred-bed reactor is preferred. The reaction tends to be rapid and is generally determined by the amount of catalyst, the pressure of the reactor, reaction temperature and related factors as appreciated by those skilled in the art. In general, residence times of from about 0.2 hours to about 5.0 hours provide acceptable results When the process is run as a batch process, it is generally preferred to use residence times of from about 0.5 to about 3.0 hours accompanied by the addition of hydrogen as it is consumed by the reaction.
It is preferred that the process herein be carried out in the presence of a molar excess of hydrogen, preferably two or more moles of hydrogen per mole of the selected cyanoorganosilane starting reactant. In general, the greater the amount of hydrogen present, the faster the reaction. Therefore, in a preferred mode of operating the process, hydrogen is added in excess at a concentration sufficient to maintain the pressure within the reactor within the range of from about 200 psig to about 2000 psig, and more preferably within the range of from about 500 psig to about 1000 psig, since these pressures permit the use of standard high pressure reactors.
The present process can conventionally be conducted at a temperature within the range of from about 50EC to about 250EC, and preferably at from about 100EC to about 200EC.
The sponge cobalt catalyst employed in the process of this invention can conveniently be selected from among any of several kinds that are commercially available, e.g., Raney7 cobalt, type 2724, from W. R. Grace and Co-0138P from Englehard Corp. If desired and for particular applications, the sponge cobalt can be combined with one or more other catalytically active components, e.g., one or more metals of Group 6B and/or 8B of the Periodic Table of the Elements such as chromium, nickel and/or iron. These metals can be combined with the sponge cobalt catalyst employing any known or conventional process such as doping.
The amount of sponge cobalt catalyst employed in the process of this invention, can vary widely provided, of course, that a catalytically effective amount of the catalyst is present. Useful amounts of sponge-cobalt catalyst can range from about 0.05 to about 20 weight percent, and preferably from about 0.5 to about 1 weight percent, based on the weight of the cyanoorganosilane reactant.
It is convenient to add the sponge cobalt catalyst to the reactor as a slurry, e.g., in a quantity of the intended product primary aminoorganosilane. While the starting cyanoorganosilane could also be utilized for this purpose, it is preferable not to do so since on standing, there may be a tendency of the cyano functionality to result in some poisoning of the catalyst.
The presence of liquid water and/or water vapor is to be substantially avoided as water tends to result in polymerization of some product primary aminoorganosilane to a polysiloxane. It is therefore advantageous to purge the reactor, once sealed, with an inert gas such as nitrogen to substantially remove any water that may be present.
The process of this invention can, if desired, be conducted in the presence of an organic solvent as the use of an organic solvent may increase the rate and/or yield of the process without, however,
Gedon Steven
Hale Melinda
Crompton Company
Ma Shirley S.
Shaver Paul F.
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