United States Patent [191 [11] 3,971,846 Skelcey [451 July 27‘, 1976

[54] PREPARATION OF HYDRIDE l. A novel process for preparing AND ALUMINUM HYDRIDE and aluminum hydride which comprises; [75] Inventor: James S. Skelcey, Midland, Mich. a. adding a solution of beryllium borohydride to a solution of lithium aluminum hydride such that [73] Assignee: The Dow Chemical Company, the ratio of lithium aluminum hydride to Midland, Mich. beryllium borohydride on a gram mole basis [22] Filed: Jan. 30, 1964 ranges from about 2 to about 5 and precipitating beryllium hydride in the resulting mixture, the [21] Appl. No.: 342,850 solvent for said lithium aluminum hydride and beryllium borohydride being a liquid material [52] US. Cl...... 423/645 inert to the reactants and products and dissolving [51] Int. Cl...... C0lb 6/00; C0lf l/00; said beryllium borohydride and lithium aluminum _ C0lf 3/00; C0lf 7/00 hydride but being a substantially non-solvent for [58] Field of Search ...... 23/204; 423/645, 122, beryllium hydride, 423/124 b. separating said solid beryllium hydride from the reaction mass, [56] References Cited c. stripping said solvent from the residual reaction mixture, UNITED STATES PATENTS d. heating the resulting substantially dry product 3,729,552 4/1973 Kratzner et a1...... 423/645 mass at an elevated temperature of from about 3,764,666 10/1973 .. 45° to about 140° C. for a period of from about 3,769,385 10/1973 0.25 to about 24 hours, and 3,780,169 12/1973 .. e. recovering a substantially ether free, 3,784,423 l/1974 Kobetz ...... 423/645 ether-insoluble aluminum hydride of hexagonal Primary Examiner-Leland A. Sebastian crystal structure. Assistant Examiner—R. E. Schafer Attorney, Agent, or Firm—-L. S. Jowanovitz 3 Claims, No Drawings EXEMPLARY CLAIM 3,971,846 . 2 The present process is carriedout under substantially PREPARATIONi _ OF BERYLLIUM HYDRIDE AND anhydrous ‘conditions in an inert atmosphere, such as 'nitrogenp'or argon, for example. " ALUMINUM'HYDRIDE ,j I Ordinarily thep'rocess is carried'out at atmospheric v This" invention relates to a method for preparinglight 5 pressures. However, superatmospheric pressures can metal hydrides and more particularly is concerned with _ be'employed if desired. a novel process for simultaneously preparing aluminum _Solvents suitable for use in the process are those hydride‘ and beryllium'hydride'. " ’ I ' I “ " liquid [materials inert to the reactants and products in The present novel process comprises reacting lithium ' which the beryllium borohydride and lithium aluminum aluminum hydride "and beryllium borohydride in 1 the hydride reactants as ‘well as the freshly prepared alumi presence of an inert solvent under substantially anhy num hydride producedby the metathesis reaction are drous conditions. Beryllium! hydride precipitates di ‘soluble, but in which beryllium hydride is substantially rectly in1 the reaction‘medium and is separated there completely insoluble. Organic liquids and particularly from, the vcoproduc‘ed, aluminum hydride remaining in aliphatic‘ethers such’ as , n-dipropyl ether solution. Subsequent to the separation of the beryllium and isodipropyl ether or mixtures of such ethers with hydride .- product substantially? '?solvent-free, "ether hydrocarbons, e.g. diethyl ether-‘, are particu insoluble aluminum hydride of hexagonal crystal struc larly suitable for use in the'process, diethyl ether being ture is recovered from the residual reaction solution. preferred. The quantities of solvent to be used in pre In actual practice of the‘ invention, usually an alkyl paring the reactant solutions are not critical except that ether solution of beryllium borohydride [Be(BH,,)'2] is 20 at a minimum the amount must be such that the reac . added to an'alky-l ether solution of lithium aluminum tants are ‘completely dissolved therein. Maximum hydride! (-LiAlH4) at atemper-ature of from about room amounts of solvent to be used ordinarily are limited to temperature-up to? about the boiling point of the solu those volumes such that the reaction mixture does not tion’ in an amount such that the ratio of LiAlH4. become unduly bulky and unwieldly ‘to handle both /'Be(BH4)2 on a gram mole basis- ranges from about 2 to 25 during the initial reaction and subsequent'solid-liquid about 5ior more-Thev precipitated beryllium hydride separation,’ solvent stripping and the like operations. product is separated from the reaction mass, ordinarily Conveniently solutions ranging from about 0.2 to about by ?ltration. The ether-solvent is then stripped from the l?rnolar in the reactant solute are employed. residual reaction mixture and the resulting’ substantially . ' The reactionsolutions can be used as prepared. How dry productmass heated with. agitation, of the product 30 ever for obtaining optimum yields and the highest pu mass at an elevated. temperatureof from aboutl45° to rity products'usually the reactant solutions are ?ltered about gl40° C. under reducedpressure for a period of or otherwise treated prior to mixing to'remove insolu .,about 025 to about 24-hours.» The resulting solid prod ble matter ~therefrom. ' uct is washed vwith ether and dried. Theso-ivashéd and The beryllium borohydride reactant readily can be dried product consists of a‘ high purity substantially prepared by reacting beryllium chloride and sodium ether-free, ether-insoluble aluminum hydride‘of hexag borohydride in' the solid state. High purity r'eactants, onal crystal structures . _ ,_ ,‘ v ' i.e. beryllium borohydride and lithium aluminum hy , In a preferred embodiment of the invention, a diethyl dride are preferred to assure a minimum of impurities ether solution of ,beryllium borohydride, ‘which-is sub in the ?nal product. stantially free‘from insoluble matte_r,§is added slowly The followingExample will serve to further illustrate with stirring at. vaboutreflux temperature't'o a diethyl the present invention but is not ‘meant to limit it‘ ethersolution .of- lithium aluminum hydride which, also thereto. is'substan'tially‘ ,free‘from insolubles,‘in_'an amount pro EXAMPLE 1 viding LiAlH4/Be(l3l~l4)2 in a gram mole ratioof about 45 About 6.5 gramsof lithium aluminum hydride was Beryllium hydride precipitates directly as the solu dissolved in about 200 cubic centimeters of diethyl . tion of beryllium borohydride is added to the lithium ether. The resulting solution, about 0.85 molar in con aluminum hydride solution. Following the completion centration was ?ltered to remove any insoluble matter of admixing the reactants, the solution is separated, therefrom. About 3 grams of beryllium borohydride ordinarily by ?ltration, from the solid beryllium hy 50 was dissolved in a separate portion of about 200 cubic dride product. This solid material which ordinarily has centimeters of diethyl ether to provide a solution about some residual solvent and aluminum hydride associated 0.31 molar in concentration. This also was ?ltered to therewith can be further puri?ed, if desired. remove insoluble matter therefrom. Solvent is stripped from the residual substantially The lithium aluminum hydride solution was heated to solid-free product solution and the resulting dry prod 55 reflux while being continually stirred. The beryllium uct heated at a temperature of from about 65° to about borohydride solution was‘ added slowly to this agitated 75° C. for a period of from about 4 to about 6 hours lithium aluminum hydride solution, a white, gelatinous ordinarily under a maximum pressure of about 0.1 precipitate forming substantially instantaneously as the millimeter mercury absolute. two solutions made contact. Following the completion The resulting solid product is washed with diethyl v60 of the beryllium borohydride solution, the reaction ether to remove any excess reactants and other ether mixture was stirred for an additional several minutes. soluble impurities therefrom. The so-washed product The solid product was removed by ?ltering through a consists substantially of a high purity, ether-free, ether glass frit. Characterization of this product after drying insoluble aluminum hydride of hexagonal crystal pat indicated it to be beryllium hydride of about 91 mole tern exhibiting a speci?c X-ray diffraction pattern pe 65 per cent purity withsome aluminum hydride and ether culiar to the novel aluminum hydride form disclosed occluded with or sorbed thereto. and claimed in a copending application Ser. No. The ?ltrate was placed in a distilling flask and the 179,509 by N. E. Matzek and D. F. Musinski. ether removed by subjecting the mass to a reduced 3,971,846 pressure of about 100 microns mercury absolute at hydride in the resulting mixture, the solvent for about room temperature. said lithium aluminum hydride and beryllium boro The resulting solid product mass was heated at a hydride being a liquid material inert to the reac temperature of about 65° C. for about 6 hours while tants and products and dissolving said beryllium maintaining an absolute pressure of about 0.1 millime borohydride and lithium aluminum hydride but ter mercury on the system. X-ray diffraction analysis of being a substantially non-solvent for beryllium hy the so-treated product indicated from about 50-70 dride, , percent of a hexagonal aluminum hydride, 20-30 per b. separating said solid beryllium hydride from the cent lithium borohydride and 10-20 percent lithium reaction mass, aluminum hydride. This product mass was washed with - c. stripping said solvent from the residual reaction 200 cubic centimeters of diethyl ether, ?ltered and mixture, dried for about 1 hour at about 65° C. at an absolute d. heating the resulting substantially dry product pressure of about 0.l millimeter mercury. X-ray dif mass at an elevated temperature of from about 45° fraction of the resulting solid indicated it to be substan to about 140° C. for a period of from about 0.25 to tially hexagonal aluminum hydride having a speci?c about 24 hours, and pattern peculiar to that disclosed and claimed in appli e. recovering a substantially ether free, ether-insolu cation Ser. No. 179,509. The recovery of the aluminum ble aluminum hydride of hexagonal crystal struc hydride based on the lithium aluminum hydride reac ture. tant was about 63 percent of theory. 2. A process for preparing beryllium hydride and a All operations were carried out with substantially 20 anhydrous materials under substantially anhydrous ‘ high purity aluminum hydride which comprises: conditions in an inert nitrogen atmosphere. a. adding a diethyl ether solution of beryllium boro By following the same general procedure as de hydride to a stirred diethyl ether solution of lithium scribed directly hereinbefore in the Example, beryllium aluminum hydride at about re?ux temperature in hydride and hexagonal crystalline aluminum hydride 25 an amount providing a lithium aluminum hydride were prepared using diethyl ether and benzene in a 121 to beryllium borohydride gram mole ratio of about volume ratio as solvent. Similarly, dipropyl ether suc 2.5 and precipitating beryllium hydride directly in cessfully can be used as a solvent. the reaction mixture, A number of runs were made wherein lithium alumi b. separating the solid beryllium hydride from the num hydride/beryllium borohydride reactants of mole residual product solution, ratio of from about 2 to about 2.5 were employed using c. stripping said diethyl ether solvent from the resid diethyl ether solution of concentration from about 0.25 ual product mass, to about 1 molar. Similar product recoveries and yields d. heating the resulting substantially dry product were realized. mass at'a temperature of from about 65° to about Various modi?cations can be made in the process of 35 75° C. for a period of from about 4 to about 6 hours the present invention without departing from‘the spirit at a maximum pressure of about 0.1 millimeter or scope thereof for it is understood that I limit myself mercury absolute, only as de?ned in the appended claims. e. washing the so-heated product mass with diethyl I claim: ether‘ and recovering the high purity ether free, 1. A novel process for preparing beryllium hydride 40 ether insoluble aluminum hydride of hexagonal and aluminum hydride which comprises: crystal pattern. a. adding a solution of beryllium borohydride to a 3. The process as de?ned in claim 2 and including the solution of lithium aluminum hydride such that the step of separating any solids from the diethyl ether ratio of lithium aluminum hydride to beryllium solutions of said lithium aluminum hydride and said borohydride on a gram mole basis ranges from 45 beryllium borohydride prior to admixing. about 2 to about 5 and precipitating beryllium * * * * *

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