US 3492112 A
Description (OCR text may contain errors)
United States Patent 3,492,112 PROCESS FOR PRODUCING BERYLLIUM POWDER Paul Kobetz and Roy J. Laran, Baton Rouge, La., assignors t0 Ethyl Corporation, New York, N.Y., a corporation of Virginia I No Drawing. Filed Mar. 4, 1966, Ser. No. 531,749
Int. Cl. B221? 1/00 US. Cl. 75.5 13 Claims ABSTRACT OF THE DISCLOSURE Finely divided beryllium metal is prepared by the low temperature reduction of a beryllium alkyl with alkali metal.
This invention relates to the preparation of metallic beryllium and, more particularly, to a method for the preparation of metallic beryllium in finely divided active form.
Beryllium metal has been prepared hitherto by the method of Stock and Goldschmidt, which involves the electrolysis of a fused mixture of the fluorides of sodium, beryllium and barium.
Alternatively, beryllium fluoride is reduced with magnesium metal at elevated temperatures to produce beryllium metal and magnesium fluoride. Both processes require elevated temperatures and produce the metal as massive lumps which must be ground into powder before the metal can be fabricated into useful shapes. In addition, the magnesium reduction route involves a difficult separation of the by-product magnesium fluoride from the product beryllium metal.
More recently, metallic beryllium has been obtained in the form of a powder by the cautious thermal decomposition of di-tert-butyl beryllium, which is expensive and troublesome to prepare and purify. This latter process is best used for the preparation of beryllium coatings.
Accordingly, it is an object of this invention to provide a simple and economical method for the preparation of metallic beryllium. Another object of this invention is to provide a method for the direct preparation of a chemically active powder form of beryllium metal. Still another object is to prepare beryllium metal in a chemically active form by reduction at relatively low temperatures. A further object of this invention is to provide a method for the preparation of beryllium metal which shall not be subject to the disadvantages of the abovedescribed methods. Other objects will appear hereinafter.
This invention, therefore, provides a process for the preparation of finely divided metallic beryllium by reacting a dialkyl beryllium of the general formula R Be, wherein R is a straight-chain or branched-chain aliphatic hydrocarbon radical containing from 1 to about 6 carbon atoms, with an alkali metal or mixture of alkali metals in the presence of an inert atmosphere. Accordingly, this process constitutes an embodiment of the present invention.
More specifically, finely divided metallic beryllium can be prepared by the reduction of di-tert-butyl beryllium with a suspension of finely divided metallic sodium in an inert medium. A further embodiment of this invention comprises the preparation of finely divided metallic beryllium by the reduction of di-tert-butyl beryllium with a'suspension of finely divided metallic seodium in xylene, the reduction being carried out under dry nitrogen at atmospheric pressure and at a temperature between ambient temperature and 145 C. This constitutes a preferred embodiment of the present invention.
The advantages of the present invention are associated principally with the low reaction temperature of the proc- "ice ess. This results in a highly active product consisting of extremely small particles of metallic beryllium which can be made even more active by coating with an alkali metal. Furthermore, the process is simple in operation and uses relatively inexpensive raw materials. The reaction proceeds according to the equation The by-product NaBeR can be reacted with BeCl to regenerate R Be(2NaBeR BeC1 3R Be+2NaCl) so that only beryllium chloride and sodium metal are consumed and the more expensive R Be is continuously recycled. The low-molecular-weight dial-kyl beryllium compounds are volatile liquids, readily purified by distillation. Distillation of the R Be prior to its reduction provides a beryllium compound which is free of the metal impurities commonly found in beryllium halides and therefore permits the preparation of beryllium metal free of these common impurities. The low reaction temperature makes possible the use of simple and inexpensive equipment. All the foregoing considerations point to a process which is simple and inexpensive to operate and which, therefore, shows marked advantages over methods hitherto known.
The invention will be more fully understood by reference to the following set of illustrative examples in which all parts and percentages are by weight, except where otherwise specified.
Example I In an atmosphere of dry nitrogen, 50.5 ml. of di-tertbutyl beryllium diethyl etherate, dissolved in 125 ml. of toluene, were added slowly, with vigorous stirring, to a suspension of 2.8 g. of finely divided sodium in 125 ml. of toluene. The reaction mixture was heated to reflux and stirring was continued. Blackening started, at once. Reflux was continued for 7 hours, after which the mixture was cooled and filtered with suction. The black solids were washed, taken up in toluene and treated with an isopropyl alcohol-benzene mixture to remove any residual sodium. The resulting powder was washed successively with pentane and ether, then dried under vacuum. X-ray analysis indicated beryllium metal of a purity of percent, the balance consisting largely of beryllium hydride.
Similar results are obtained when, in the above example, the di-tert-butyl beryllium is replaced by di-n-hexyl beryllium and the sodium by a liquid alloy of sodium and potassium.
Example II In a suitable reactor, previously flushed with dry methane, 123 parts of di-tert-butyl beryllium are introduced followed by a suspension of 13 parts of finely divided metallic potassium in parts of xylene. The reactor is sealed, heated to C. for one hour and cooled. The reaction mixture is filtered and the residue is washed successively with repeated portions of diethyl ether, toluene, isobutanol and (once more) diethyl ether and is then dried at 100 C. The product is metallic beryllium of a relatively high degree of purity.
When, in the above example, the di-tert-butyl beryllium and the xylene are replaced respectively by diisopropyl beryllium and toluene similar results are obtained.
Example III A rotatable reactor is flushed with dry argon and is then charged with 200 parts of normal octane. Thirty-nine parts of crystalline dimethyl beryllium are then introduced; the reactor is sealed and rotated to dissolve the dimethyl beryllium. It is then opened to permit the addition of 16 parts of lithium-potassium alloy (1:1 atom ratio) and rescaled. The reactor is then immersed in an oil bath at 50 C. Rotation is begun and continued for 4 hours at the stated temperature, after which the reactor is removed from the bath and cooled. The reaction mixture is filtered with suction. The filter cake is washed repeatedly with diethyl ether and hexane and is then treated with 75 parts of isopropanol for an hour at ambient temperature, after which the mixture is filtered and the residue is washed with ether and dried at 100 C. A highly pure metallic beryllium is obtained.
In carrying out the process of this invention a broad variety of reactants can be employed. The reducing metal may be any of the alkali metals, namely, lithium, sodium, potassium, rubidium, or cesium, or any alloy of the foregoing. Sodium is preferred because of its cheapness and availability and because it results in a rapid but easily controlled reduction.
The organo beryllium reactant can be any straightor branched-chain dialkyl beryllium containing not more than 6 carbon atoms in each alkyl group. Of these, di-tert-butyl beryllium is preferred because of the ease and smoothness of its reduction with alkali metal.
For the sake of ease in purifying the product, it is preferred to use the reactant in approximately stoichiometric proportions. However, successful use can be made of a 100 percent or greater excess of the organo beryllium compound or of a 100 percent or greater excess of the alkali metal.
The limits of reaction temperature are set by the slowness of the reaction at low temperature and the thermal decomposition of the organo beryllium compound at high temperature. In general, therefore, reaction temperatures can range from ambient temperature or below to the decomposition temperature of the organo beryllium compound, i.e., about 150 C. Temperatures ranging between 50135 C. are preferred because they yield smooth reactions and practical reaction rates.
The reaction is carried out under a protective atmosphere which may be any gas inert to both reactants and products.
Dry nitrogen, as the cheapest and most readily available inert atmosphere, is preferred but other possible atmospheres include saturated gaseous hydrocarbons, carbon monoxide, helium, neon, argon krypton and xenon.
The protective gases are normally used under atmospheric pressure. This pressure is preferred for reasons of ease of operation and simplicity of equipment, but pressures from 0.1 atmosphere or less to 100 atmospheres or more can be employed if desired.
The reaction can be carried out if desired in the absence of any solvent, but a solvent is normally used which may be an aliphatic, aromatic or alicyclic hydrocarbon or mixture thereof. Of these, toluene is preferred because of its ready availability and because its reflux temperature is in the desired range of reaction temperature.
The order of introduction of the reactant is immaterial. Normally, the suspension of alkali metal is added to the organo beryllium compound but the opposite order of addition is also satisfactory.
The finely divided beryllium product of this invention is useful in a number of ways. Beryllium metal has a low thermal neutron absorption cross-section which makes it a desirable moderator material for use in nuclear reactors. Its high strength-to-weight ratio renders it attractive for aeronautical applications. Its thermal properties are attractive for such applications as fins on high temperature motors. The ultrafine grain-sized beryllium powder produced in accordance with this invention can subsequently be consolidated into massive beryllium structural products by various well-known powder and metallurgical techniques, such as by first compressing the powder to form a bar, then subjecting this bar to fusion under vacuum, for example in an electronic beam furnace, or by hot pressing which comprises sintering under heavy pressure.
What is claimed is:
1. Process for the preparation of finely divided metallic beryllium which comprises reacting a dialkyl beryllium of the general formula R Be, wherein R represents a radical selected from the group consisting of straightchain and branched-chain aliphatic hydrocarbon radicals, each hydrocarbon radical containing from 1 to about 6 carbon atoms, with a reactant selected from the group consisting of alkali metals having atomic numbers in the range from 3 to 55, inclusive, and of mixtures of said alkali metals, the reaction being carried out under a pressure ranging from less than 0.1 atmosphere to more than atmospheres of a gas inert with respect to reactants and products and at a temperature ranging from ambient temperature to the temperature of thermal decomposition of the dialkyl beryllium reactant, and separating the metallic beryllium product.
2. The process of claim 1 wherein the alkali metal reactant is disposed in an inert solvent.
3. The process of claim 1 wherein the alkali metal is sodium.
4. The process of claim 1 wherein the dialkyl beryllium is diethyl beryllium.
5. The process of claim 1 wherein the reaction is carried out in a solvent.
6. The process of claim 1 wherein the reaction is carried out in a solvent selected from the group consisting of saturated aliphatic, alicyclic and aromatic hydrocarbons, liquid under the reaction conditions.
7. The process of claim 1 wherein the reaction is carried out in xylene as a solvent.
8. The process of claim 1 wherein the inert gas is selected from the group consisting of nitrogen, saturated aliphatic hydrocarbons which are gaseous under the reaction conditions, saturated aliphatic fluoro hydrocarbons which are gaseous under the reaction conditions, carbon monoxide, helium, neon, argon, krypton and xenon.
9. The process of claim 1 wherein the inert gas is nitrogen.
10. The process of claim 1 wherein the temperature range is'from about 50 to about C.
11. The process of claim 1 wherein said dialkyl beryllium is di-tert-butyl beryllium.
12. The process of claim 1 wherein said alkali metal is sodium and the temperature range is from about 50 to about 135 C.
13. The process of claim 1 wherein the alkali metal is sodium, the temperature range is from about 50 to about 135 C. and said dialkyl beryllium is di-tert-butyl beryllium.
References Cited UNITED STATES PATENTS 1,867,755 7/1932 Pelc 750.5
L. DEWAYNE RUTLEDGE, Primary Examiner W. W- TALLA s a t Exam ner