US3707564A - Certain organic compounds containing beryllium and boron - Google Patents

Abstract

LIQUID BERYLLIUM COMPOUNDS, PREPARED BY THE REACTION OF TETRABORANE WITH ENUMERATED CLASSES OF ALKYL BERYLLIUM COMPOUNDS, AND USEFUL AS ROCKET FUELS, ARE DISCLOSED.

Description

3,707,564 CERTAIN ORGANIC COMPOUNDS CONTAINING BERYLLIUM AND BORON Cliff Y. Fujikawa, Encino, Calif., assignor to North American Rockwell Corporation No Drawing. Continuation-impart of application Ser. No. 603,405, Dec. 16, 1966. This application July 8, 1968, Ser. No. 743,261

Int. Cl. C07f /02 US. Cl. 260-6065 B 8 Claims ABSTRACT OF THE DISCLOSURE Liquid beryllium compounds, prepared by the reaction of tetraborane with enumerated classes of alkyl beryllium compounds, and useful as rocket fuels, are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuationdn-part of my earlier filed application, U.S. Pat. Oflice Ser. No. 603,405, filed Dec. 16, 1966 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to novel chemical compounds and to a novel method of making same. More specifically, the invention relates to organo-beryllium hydrides and novel method of preparing said organo-beryllium hydrides.

There is a constant search and an acute need in the field of liquid rocket propellant synthesis for suitable fuels. A suitable rocket fuel would preferably be a stable, nonvolatile, mobile liquid at ordinary temperatures. Additionally, it would preferably contain significant amounts of hydrogen and light metals in relation to its other components, and, in this respect, compounds containing beryllium and hydrogen are of particular interest in the field of rocket propulsion.

Generally, in the prior art, chemically simple hydrocarbons predominate among the prior art rocket fuels. Many of these prior art hydrocarbons cannot be classified as high energy fuels due to the inefficiency resulting from a high ratio of carbon to hydrogen in the molecules. An example of such prior art low energy fuel would be kerosene. Other prior art compounds, although possessing high energy fuel levels, are highly difficult to store at ambient States mt temperatures or extremely difficult to manufacture and are therefore not acceptable for rocket propulsion applications.

As a result of the unwanted and undesirable features associated with the prior art, effort is being directed toward the production of novel, energetic products suitable for fuels in rocket systems. Specifically, towards this goal of achieving acceptable energy fuels, liquid beryllium hydrides, for example, are of interest as advanced propellants having high calculated energetic impulse.

The herein invention relates to novel, energetic organoberyllium hydrides that overcome the difiiculties associated with the prior art compounds. The beryllium hydrides of this invention are important for utilization in propellant formulations wherein beryllium hydride can be more easily processed into the propellant formulations. Additionally, the liquid beryllium hydrides of this invention can SUMMARY OF THE INVENTION The liquid beryllium compounds of this invention are accomplished by reacting liquid or gaseous tetraborane, B H with alkyl beryllium compound selected from the group consisting of X BeX and wherein R is selected from the group of alkyl radicals containing from one to about six carbon atoms; X through X are individually selected from the group consisting of H and R; such that in the compound X BeX only one of the Xs can be H; further such that for any particular R each of X through X is selected from the group consisting of H and that particular R; m is from 1 to 10; and n is from 0 to about 6. Compound I will be more energetic if R and X contain few carbon atoms.

DETAILED DESCRIPTION The organo-beryllium compound resulting from the reaction of the described reactants is of a complex chemical nature. The reaction may be described as the hydridization of the alkyl beryllium compounds resulting in the liquefaction of the alkyl beryllium compounds. The formula of the resulting mobile product naturally is a func tion of the starting material. The formula may be ascertained on an empirical basis by hydrolysis and analysis. Such analyses are known in the prior art. A typical procedure, suitable for analysis of the products of the instant invention, would involve cooling the liquid borane terminated alkyl beryllium hydride product to less than C., adding a hydrolyzing agent, for instance, npropyl alcohol, and dilute hydrochloric acid to the cooled hydride. Gases evolved would be pumped off, measured and analyzed by means of a mass spectrometer. The ratio of H to CH in the gas can be ascertained. The remaining liquid can then be analyzed quantitatively for beryllium and boron. Simple calculations result in the relative ratios of beryllium, boron, hydrogen, and CH In any case, it appears that the liquid products of the described reaction are compounds containing a very high ratio of beryllium and hydrogen to carbon. Such compounds have very high theoretical specific impulses. In general, then, the reaction may be conducted so that the product will be a mobile liquid with a very high theoretical performance as a liquid fuel.

The reactants and products of the instant invention are highly reactive and should not be allowed to come in contact with air. Should such contact occur, spontaneous combustion will result. Accordingly, the reaction of the instant invention should be conducted either under a blanket of inert gases or, more preferably, in a vacuum. While an inert blanket prevents spontaneous combustion, it also has a diluent effect upon the reaction of the invention. Vacuum preparation is, therefore, the preferred mode of practicing this invention. Some pressure is generated by the vapors from tetraborane and the production of gaseous or volatile side products. A suitable means of conducting the reaction of the instant invention is to place the alkyl beryllium reactant in an evacuated reaction chamber. The chamber may be of, for example, glass. Tetraborane is then introduced into the reaction chamber. Since tetraboranes boiling point at atmospheric pressure is 18 C., it may be introduced at ambient temperatures as a gas or it may be introduced at temperatures below 18 C. as a liquid.

A typical liquid-solid synthesis would involve allowing tetraborane liquid to vaporize and the vapor to come in contact with a cooled alkyl beryllium reaction bed. The tetraborane would then condense and react with the alkyl beryllium. An alternative liquid synthesis would involve cooling the alkyl beryllium reaction bed below 120 C., such that the tetraborane vapor condenses as solid crystals. The reaction bed of alkyl beryllium compound and solid tetraborane may then be slowly warmed towards ambient temperatures, resulting in liquefaction of the tetraborane and reaction between the liquid tetraborane and the solid alkyl beryllium compound.

Alternative to a liquid tetraborane alkyl beryllium reaction system would be a gaseous tetraborane alkyl beryllium reaction system. Such a system would comprise an ambient temperature bed of alkyl beryllium being contacted by the vapors of a warming source of liquid tetraborane.

In the gas scheme, the reaction takes longer, but a higher percentage conversion of the initial reactants to liquid beryllium compounds is realized. In practice, this vapor reaction takes place by allowing the vapor from a source of warming liquid B H to contact the alkyl beryllium. As the reaction proceeds, the alkyl beryllium compound will be seen to liquefy, indicating reaction and conversion to the desired liquid hydride product.

If a liquid synthesis is used, reaction will be faster, but undesirable side reactions will occur more extensively. That is, solid beryllium compounds are extensively formed. Examples of such solid compounds would be BH polymers and impure BeH Either the liquid or the gas reaction can be stopped by quenching, Le, a rapid reduction to cryogenic temperatures. Tetraborane can then be removed from the system by means taking advantage of tetraboranes low melting and boiling point. Once the tetraborane is removed, of course, further hydriding of the alkyl beryllium compound is prevented.

It has been found that the rate of the hydridization reaction is afiected by the molar ratio of the reactants. As would be expected, if more B H is present, the reaction will proceed faster. While the use of larger tetraborane to alkyl beryllium molar ratios decreases, the time required to convert the alkyl beryllium to liquid products, further hydriding of the desired liquid products to undesirable solids also occurs more rapidly under these conditions. For example, in an experiment in which a B H Be(CH molar ratio of 1.0 was used, the Be(CH was completely liquefied after 26 hours. To ascertain if the reaction was complete, the mixture was allowed to remain at ambient temperatures for 3 /2 hours. At the end of this time, the mixture was still liquid and unreacted B H was still present. This indicated that further hydridization would not occur, and the liquid compound formed was stable. In a different experiment in which the same reactants were present in a molar ratio of B H /Be(CH of 2.0, liquefaction of the Be(CH was complete after 18 hours; however, at the end of 29 hours, the non-volatile beryllium product was primarily a solid. Similar extensive solid products at the molar ratio of B H /Be(CH of 1.0 have also been obtained when the reaction time was extended to 93 hours.

The organo-beryllium borohydride employed herein and having the formula is easily prepared according to one of the following reactions: (a) in the case wherein R is methyl (MeBeBI-LQ is mixed with a commercially available dialkyl beryllium, such as dimethyl beryllium, of the general formula RBeR 4 and with beryllium hydride of the formula BeH in a hydrocarbon solvent and stirred for several days at room temperature under normal atmospheric conditions. The BeH can be prepared by the reaction of beryllium borohydride, Be(BH. with an alkyl aluminum compound, AlRR'R", wherein R, R and R" are selected from a class consisting of H and alkyl radicals of 1 to 8 C atoms and wherein at least one of the Rs is an alkyl group. The reaction of the two compounds is generally carried out in the presence of a conventional hydrocarbon solvent at from about 0 to C. Particularly good yields have been obtained at reaction temperatures of 60 to 65 C. When the reactants are present in equal molar quantities the reaction proceeds according to the following equation:

The by-product compound remaining dissolved in the solvent has not been separated for characterization but is predicted to be A1B RRR"H The (BeH formed is a solid. The alkyl aluminum compounds include, for example, methyl aluminum dihydride, butyl aluminum dihydride, dipropyl aluminum hydride, trioctyl aluminum and the like. At the completion of the reaction period the unreacted solid material is removed by filtration and the solvent evaporated to leave behind a syrup of the general formula:

The reactant (MeBeRHQ is easily prepared by the reaction of equal molar quantities of Be(BH and (Me) Be. The reaction to form the organoberyllium borohydride is as follows: (Me) Be+Be(BH (MeBeBH The next reaction as set forth supra or (b) is wherein R is 2 to 6, that is straight or branched chain lower alkyl such as ethyl, propyl, isopropyl, isobutyl, hexyl and the like, then varying amounts of BeR are intimately mixed with Be(BH under normal atmospheric conditions and at room temperature to give the corresponding can also be prepared by (c) reacting Be(BH with BeR wherein R is a lower alkyl of 2 to 6 carbon atoms as defined immediately above and with BeH The intimate mixing of Be(BH BeR and BeH is carried out under conditions as set forth immediately above.

The following examples illustrate the spirit of the pres ent invention for preparing the novel compounds of the general formula (X B) (RBeH) (BeH B H wherein X is a member selected from the group consisting of hydrogen and lower alkyl of 1 to 6 carbon atoms, R is a lower alkyl of 1 to 6 carbon atoms, m is from 1 to 4 and n is from 0 to 3.

Example I A glass vessel containing a clear viscous liquid with an average empirical formula of was stirred with B H at ambient temperature and pressure. The compound CH H B(CH BeH) BeH- BH was prepared by intimately mixing 6.4 mmoles of 5.42 mmoles of Be(CH and 17.4 mmoles of BeH in 8 ml. of n-hexane in a glass reactor with constant stirring of the reaction medium for 15 days at room temperature under normal atmospheric conditions. Next, the unreacted solid was filtered off and the excess solvent evaporated to give the CH H B(CH BeH) BeH BH After stirring this latter compound with the former compound B H under ambient temperature and pressure for 16 hours a very mobile nonvolatile liquid was obtained. Analysis of this new liquid gave the following results: hydridic hydrogen, 5.18 mmoles (83.0 mmoles/gm); CH -bridge groups 1.05 mmoles (16.7 mmoles/gm); Be, 1.33 moles; and B, 1.35 mmoles. These results indicate the COmPQSitlOIl H3B(CH3BCH)3BBH2'B3H7.

Example II To 0.83 mmole of (CI-I BH(CH BeH) (BeH BH(CH was added 2.34 mmoles of B H and stirred at ambient temperature. The compound was prepared by thoroughly mixing 10.2 momles of Be(CH 4.63 mmoles of BeH and 11.5 mmoles of (CH BeBH in 13 ml. of n-hexane. The reaction mixture was stirred at 50 C. for 5 days and then the resulting mixture filtered with a glass-sintered funnel to remove the unreacted solid materials. Finally, the excess solvent was evaporated and the viscous liquid remaining was mixed with B H The final product was a very mobile, non-volatile liquid.

Example III 1.6 mmoles of B H was condensed at 196 C. in a conventional glass reactor containing 10.5 mmoles of (CH Be. After 36 hours at ambient temperatures, a moist solid was present in the reactor. Fractionation of volatiles from the moist solid gave B(CH and unreacted B H A second similar treatment with 3.05 mmoles of B H over a period of 48 hours at ambient temperatures resulted in the formation of a mobile liquid with a few specks of solid suspended in it. The by-product B(CH was again formed. A third treatment with B H resulted in a stirrable solid/liquid mixture.

The solid/ liquid mixture was extracted with n-hexane, filtered, and the filtrate concentrated by vacuum distillation, yielding 0.20 g. of a nonvolatile, clear liquid. Analysis of this liquid gave: Be, 17.2%; B, 39.0%; hydride hydrogen, 119 mmoles/g; and CH bridge groups 19.1 mmoles/ g. This corresponds to a formula of B H (CH BeH) -BI-I The solid was impure BeH EXAMPLE IV 22.7 mmoles of B H was condensed at 196 C. in a one liter reactor containing 7.5 mmoles of solid (CH Be. After 18 hours, a clear mobile liquid was obtained. Volatile components consisted of a noncondensable gas, B(CH (CH B H and unreacted B H Example V 6.9 mmoles of B H was condensed at -196 C. in an evacuated glass reactor containing 11.3 mmoles of solid Be(C H After 18 hours at ambient temperature, a solid-liquid mixture was present in the reaction. Approximately 24 hours after initiation of the reaction, the soldiliquid mixture reverted to a clear liquid. The reactor was opened and 12.03 mmoles of hydrogen was removed. The volatile products were then removed and identified as being primarily (C H BH The nonvolatile material consisted of a thick liquid which was extracted with n-hexane. This treatment resulted in the separation of the viscous material into an insoluble crystalline solid and a n-hexane soluble product. Concentration of the n-hexane afforded the nonvolatile liquid product B3H7'C2H5BCHB6H2'BH3.

Analyses for B3H7'C2H5BEHBCH2'BH3 were as follows: Calculated, in mmoles, were: Be, 0.68; B, 4.73; and C H 0.34. Found were: Be, 0.63; B, 4.42; and C H 0.30.

Example VI Into a glass reaction vessel containing 0.82 mole of CH H B(CH BeH) BH dissolved in n-hexane was added 2.6 mmoles B H The two reagents were intimately and thoroughly mixed for 16 hours at room temperature and normal atmospheric pressure to give a mobile non-volatile liquid. The compound CH H B(CH BeH) BH was prepared prior to its addition to B H by thoroughly mixing 10.7 mmoles of Be(CH 29.2 mmoles of BeH and 10.6 mmoles of (CH BeBH in 13 ml. of n-hexane for 5 days with mild stirring at room temperature and pressure condition.

The liquid beryllium compounds prepared according to the present invention can be used as rocket fuels and they are suitable for mixing with oxidizers for their energetic content. The specific impulse of a fuel oxidizer system at a chamber pressure of 1000 p.s.i.g. and the exit pressure of 14.7 p.s.i.g. was calculated for the compounds of this invention. The organoberyllium fuel compound H B(CH BeH) BeH -B H as prepared according to the procedure of Example I was combusted with H O oxidizer in a ratio of oxidizer to fuel of 1.62:1 exhibited a specific impulse of 326 seconds. The compound B H (CH BeH) BH was used in an H 0 fuel-oxidizer system had a specific impulse of 320 seconds. The fuel B3H7(C2H5BH)(BCH2)BH3 when mixed H202 cX- hibited a specific impulse of 326 seconds.

Since it is obvious that many changes and modifications can be made in the above described details without department from the nature and spirit of the invention, it is to be understood that the invention is not to be limited thereto except as set forth in the appended claims.

I claim:

1. The process of producing a high energy mobile liquid beryllium hydride compound comprising:

reacting B H and a compound selected from a group consisting of X BeX and wherein R is selected from the group of alkyl radicals containing from 1 to about 6 carbon atoms; X through X are individually selected from the group consisting of H and R; such that in the compound X BeX only one of the Xs can be H; further such that for any particular R each of X through X is selected from the group consisting of H and that particular R; m is from 1 to 7; and n is from 0 to about 6. 2. The process of claim 1 where B H is reacted with a compound selected from the group consisting of B CH3 2 and BE(C2H5)2.

3. The process of claim 1 where B l-I is reacted in a gaseous state.

4. The process of claim 1 where the B H is reacted in a liquid state.

5. A compound of the formula wherein X is a member selected from the group consisting of hydrogen and lower alkyl of 1 to 6 carbon atoms, R is a lower alkyl of 1 to 6 carbon atoms, m is from 1 to 4 and n is from 0 to 3.

6. A compound according to claim 5 of the formula 7. A compound according to claim 5 of the formula OTHER REFERENCES H B(CH BeH) B H Wiberg, AEC-tr-1931, New Results in Preparative 8. A compound according to claim 5 of the formula Hydride Research 1964 16 a H B(C H BeH)(BeH )B H 5 LELAND A. SEBASTIAN, Primary Examiner References Cited US. Cl. X.R.

UNITED STATES PATENTS 14922; 260-665 R 3,062,856 11/1962 DAlelio 14922UX l0

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