DE1792040A1 - Process for the production of sodium dodecahydro-dodecaborate - Google Patents

Description

Process for the production of Na'riiLr # i-dodecaLZdro-dodecaborate LI The dodecahydro-dodecaborate ion B 12 H 12 2- with the highly symmetrical icosahedral structure - with the known carboranes of the type B 10 C 2 H 12 (to B. o-Carborane, 1 -, - 2-Diearbaaloso-dodecaborane-12) st.-u., ctureil closely related (isoelek £ t.-ronisch) was 1gÖ0 for the first time as a by-product of the conversion of CD 2-iodine "decaborane-14 with -Triäthylamine discovered ".comp. Hawthorne et al, J. Am. Chem. Soe. 8 -;>, 3228- (1966). The unusual chemical and thermal stability of this system of 12 boron and 12 hydrogen atoms, however, was predicted beforehand from theoretical U considerations. See Longuett-Higgins et al, Proc. Roy. Soe. (London)., A 2_30., L'10 (195.5). A little later, some synthetic routes for the targeted production of the B 12 H 12 2 system could be shown, which in principle all proceed in a similar way, cf. Miller et al, Inorg. Chem.

3218 (1964) and US Pat. No. 328 134. One starts with either sodium boranate, .Natriünoetahydrotriborat or of tr-iäthylamin-borane or other amine.BH 3 adducts - and these borohydrides are exposed at higher temperatures in high-boiling solvents or under Printing with diborane, decaborane or other Bo-rdassersL-, open around, e.g. according to the following reaction equation. ' What these manufacturing processes have in common is that they not only start from complex borohydrides, but also from self-igniting and poisonous hydrogen boron compounds.

must be. These processes, which start from materials that are not readily available, are therefore unsuitable for an industrial synthesis of economic importance. A process has now been found for the production of sodium dodecahydro-dodecaborate (Iia 2 B 12 H 12 by thermal treatment of borohydrides in the presence of hydrogen, which is characterized by mixtures of sodium borates and / or boron oxides , Sodium and / or sodium hydride, if necessary as a counterpart to finely divided aluminum, silicon or CD their alloys, silicon dioxide and / or sodium boranate initially under the known conditions of sodium boranate production at Terüperati-u- ..i # i from --00 to 500 C under hydrogen pressures of 3-8 atmospheres until the end of the Wassers'tooffaufnahme Reaktionsgenisches, then at temperatures of 600 to 8500C and hydrogen pressures of 1-5 Atmosphi # ren until completion of the under hydrogen elimination of the reaction mixture taking place under these conditions ", and the sodium dodecahydro-dodecaborate thus obtained from the reaction mixture by extraction is won. As boron-containing starting products for the process according to the invention, BoraGe of any composition, such as sodium orthoborate Na .3.3-? Sodium metaborate NaBO., Dehydrated Borax Na 2B407 or mixtures of sodium oxide and boron oxide can be used. The boron-containing Aub-angsprodukte are reacted according to the known method of sodium boronate production with reducing agents in the presence of hydrogen, as z. - has been described in German patents 1 o88 93o, 1 o67 0052 1 053 476, 1 o_36 2221 1 241 421 and others. The quantity ratios of the reactants are varied depending on the reducing agents used with regard to the desired end product Na 2 B 12 H 12. When using sodium as a reducing agent, the reaction is preferably carried out in the presence of finely divided silicon dioxide as the sodium oxide-forming agent. If borax is used, the reaction then proceeds according to the following equation 1: 1 3 Na 2 B 407 + 38 Na + 21 gi02 + 6 H 2 - + Na 2 Bl, H12 + 21 Na 2 Sio 3 In the embodiment described above, it is expedient to use the boron-containing minerals in the form of previously melted borosilicate glasses.

In a more economical embodiment of the process, the sodium is at least partially replaced by aluminum or silicon or aluminum- or silicon-rich.Leglerungen. When using borax and aluminum, the reaction takes place z. B. according to the reaction equation IIc 11 3 Na 2B407 + 10.5 Al + 6 H, + 6.5 Na -----> Na 2 B 12H12 + 10.5 NaA1020 When using silicon, the reaction can be carried out according to reaction equation III: Ill 3 Na 2B4 () 7 + 1 0 Na + 7 Si + 6 H: - # Na B Hl,:, + 7 Na 2 2 12 12 2S'03 " The aluminum or. Silicon is used in finely divided form as powder, grit or flakes. Alloys rich in aluminum or silicon with a silicon or aluminum content of at least 50% can also be used. No high demands are died on the purity of the aluminum or S'iliciums ellt 'so that, for example, wastes of aluminum or siliciumv'erarbeitenden Indüstrie can be used. The sodium can be used in the form of metallic sodium or as a hydride. Finally, according to a less preferred embodiment, it is also possible to use sodium boranate as the sodium and hydrogen source. In this case, the reaction may e.g. B. be carried out according to the reaction equation IV: IV 24 NaBH4 + 18 Na.B40 62 Al + lg ua --- # 8 Na BH + 6-3 NaA10 7+ 2 12 12 2 * The reaction equations given above are only one of the possible embodiments. Deviations or combinations of the options listed above are easily possible. The starting materials are initially heated at temperatures of about 300 to 500 ° C. and hydrogen pressures of 3 to 8 atmospheres until the uptake of hydrogen has ceased.

When using aluminum, the reaction can take place in such a way that mixtures of finely divided sodium borates., 'Sodium and aluminum with stirring at a hydrogen pressure of, for. B. 4 # atmospheres are heated to the reaction temperature and kept at this temperature until the reaction mixture has no water . absorbs more material. One can, however, also proceed in such a way that one initially converts a mixture of sodium borate or aluminum and sodium into an intimate mixture of sodium borate or aluminum and sodium hydride by heating in a hydrogen atmosphere and then finely divided aluminum or Sodium borate is introduced and heated to the reaction temperature. After the hydrogen uptake has ended, the reaction mixture is then heated to temperatures of 600 to 8500 ° C. and kept at this temperature until hydrogen is no longer split off. The sodium do'decahydrododecaborate formed is then recovered from the reaction product obtained after cooling by extraction.

CD The reaction can also be carried out continuously by feeding the reactants continuously into one end of a reaction screw located on the reaction temperature (sodium, for example, in liquid form), the reaction being controlled by cooling or metering the reactants will. After completion of the What: #erstoffaufnahme is then further heated Reaktionsprodukt'im the subsequent portion of the screw to the desired temperature 600-850 0 C.

The reaction product obtained in the reaction according to the invention consists of a mixture of the desired sodium dodecahydro-dodecaborate with sodium aluminate and also of small amounts of unreacted starting materials, such as sodium borates . rm .

and aluminum and also from small proportions of sodium hydride and lower borohydride and sodium boronate. Corresponding conversion products will be according to-the other above-recorded embodiments of the method according to the invention obtain.

There are several ways to isolate the product according to the invention be taken: Once the crude product can be dissolved in water and through a positive-liquid extraction in countercurrent with an amine, e.g. isoproDylamine, the polyhedral borohydride can be obtained, or the crude product is directly using Ammonia or an amine extracted. Finally, the isolated Na 2 B 12 H karin ip off Water, an alcohol or an organic solvent, such as. Tetrahydroj4% Uran., To be recrystallized after any lower borohydrides were destroyed with small amounts of acids.

The sodium salt 'can easily be converted into other derivatives by known methods, e.g. B. in the free acid H 2 B 12 H 12 - comparable in strength to sulfuric acid - with the help of ion exchangers or a strong inorganic acid - cf. B. US Patent 3169 044. The free acid can be delayed, for example, as a precipitating agent for metal ions, especially heavy metals, Vprwendung find-.

B 12 H 12 2 salts with other n cations can also be easily produced either by neutralization of the free acid or directly by reaction the sodium salt, e.g. B. with amines-no ammonium halides or phosphonium halides.

Finally, the BH 2 ion can be converted into valuable derivatives by a number of electrophilic reagents such as halogens, oxalyl chloride, hydroxylamino-sulfonic acid, and thus represents an interesting intermediate product. In many cases it behaves like a aromatic system and can be subjected, for example, Friedel-Crafts reactions, in the case of using the acid H 2 B 12 H 12, the reaction z. B. with olefins (alkylation) is itself catalyzed. These derivatives can be used as surface active agents. Hydrogen halides also react with C> 0 - the B 12 H 12 - ion and give halogenated ions, e.g. B.

B 12 H 11 F 2, and finally be many f- Oxygen and sulfur-containing Verbirdungen derivatives with B-0 and BS bonds (cf. EL Muetterties, The Chemistry of Boron and its Com'Oounds, Nievi York 1967, pp. 287 ff.). Further arrete.ndunzsmöc-lieb-'tz.ei'ten are described in the US patent CD Schriften _3 350 324, 3 328 1'xu and 3 lo6 098 . The identification of the by the method according to the invention formed 1 '.' a '-P h' was made by the 11 B nuclear magnetic resonance 2 12 ip CII spectrum. The i-ia-aqueous solution of the substance shows -e in the spectrum a doublet with a chemical shift of ar = 15.2 f 0.2 pp., 1- (based on Bo-.1L-, rifluorid-m, ethyl etherate as external C2 Standard ( J = 0 ppm) with a coupling constant JEH 124 + 1 Hz. The fact that the spectrum consists of only one DubleiGt exists, indicates that all boron atoms-equiva, -; lent and thus the 1-1, olekUl s #, T = etric, accordingly der-icosahedral structure of the B 121 # 12 2 -ion. Other polyhedral Borohydrides, e.g. B. BloH102-, were in the entire measuring range -: t 250 ppm not detectable. The following examples are intended to illustrate the inventive method explain driving in more detail: Example 1 A mixture of 402 g (= 2 M4oles) of drained borax., 200 g 7.4 Mible, 5% excess) Al = iniumpulver and 100 g 4.35 I. #, ole) sodium were placed in a 4 1 autoclave under Stir n and under a hydrogen pressure of 3 atmospheres within heated from 2 hours to 6200C , initially from about 2000C - considerable amounts of hydrogen (r4a '(-, ritL-ahydride formation and subsequent sodium boronate formation). C> Then an exo;, - h.erme reaction set in (T rise up to 850oc; Elimination of hydrogen). !. After 2 hours it was cooled down and the reaction product, a gray powder, was examined. It contained 12.7% Na 2 B 12 H 12 (theor. 17.7% in the mixture, a yield of about 72 %) in addition to about 1% NaBH and 1.5% NaH 4 ' and 2.7% unused Aluminum. The educated. Sodium dodecahydro-dodecaborate was extracted with isopropylamine, the solution was evaporated and the residue was recrystallized from water after moistening with a little weakly acidic water, Na 2 B 12 H12 0 3-5 H 2 0 being obtained .

EXAMPLE 2 A mixture of 2.83 kg (= 105 moles) of aluminum powder and 1.5 kg (= 65 moles) of sodium was heated to 6000 ° C. in a pressure vessel under a hydrogen pressure of 4 atmospheres and with stirring. To this sodium hydride-containing mixture, 6 kg (approx. 30 moles) of dehydrated borax were added over the course of 3 hours while increasing the temperature to 650 ° C. and maintaining the hydrogen pressure. After heating for a further two hours, the mixture was cooled and the dark gray reaction mixture was extracted with tetrahydrofuran. After evaporation of the solvent and drying, it was possible to isolate about 80% Na BH 2.12 12 Example A mixture of 417 9 6 moles) of boron oxide, 253 9 (= 11 moles) sodium and .364 g (= 13.5 moles., 50% excess ) Aluminum shavings were heated up to 6000 ° C. within 2 hours under 3 atm. Hydrogen pressure. After a further 4 hours, the reaction mixture was cooled and examined: it contained 12 % Na 2 B 12 Hl. (Theor. 18 %, a yield of 67%) in addition to about 2 % NaBH 4 and 1.7% NaH and not converted aluminum in addition to sodium aluminate. BeisDiel 4 A mixture of 201 g 1 mol) dehydrated borax, 420 g 7 mol) very finely powdered quartz flour and 306 g (= 13.3 mol l # T 5% excess) i-sodium in a stirred autoclave under an 'elassersto- -, "- L" pressure of initially 1 atm, heated to 6000C within 1 hour. From about 2000C, hydrogen was continuously absorbed (Na.H, - and NaBH, formation). On further heating over 3 hours to 4 700 0 C was cleaved again hydrogen; the print was released by ab-cd on cai. 3 atü set. After cooling, CD, the solid, gray product was examined: in addition to approx. 4 % 11aH and approx. 1% NaBH4, it contained 4.4% Na 2 B 12 Hj., A yield of 65% of theory. Th.

EXAMPLE 5 402 g (= 2 moles) of dehydrated borax, 15-4 g (= 6.65 moles) of sodium and 132 g (= 4.7 1-Iole) of silicon metal powder were placed under a -t, of Irdruck initially 1 atm in a stirred autoclave heated at about 1800C hydrogen uptake began setzte.eine at about 3600C exothermic reaction, the temperature up to 550 0 C increased in 15 minutes Total -... were to 6000C in 1 hour and about 80 standard liters H 2 was added upon further heating pressure increase occurred;., the pressure was adjusted atm via a discharge valve 3 at about 6400C, a second exothermic reaction occurred, wherein the 0 temperature in 7 minutes down to. 710 C. After a further hour of reaction time, the elimination of hydrogen was complete. The product obtained, a homogeneous, white-gray powder with individual NaH components, was examined: it contained 1., 3% NaH, 1% liaaTi4 and 11.9% Na 2 B12H12 corresponding to a yield of 66% of theory ). For isolation, the crude product was dissolved in water dissolved, weakly acidified with dilute hydrochloric acid (to destroy hydrides) and the solution evaporated again. The dodecahydro-dodecaborate formed was then extracted with isopropylamine and finally isolated.

Claims (1)

Patent claim Process for the preparation of sodium dodecahydro-dodecaborate (Na 2 B 12 Hi.) By thermal treatment of borohydrides in the presence of hydrogen, characterized in that mixtures of sodium borates and / or boron oxides, sodium and / or sodium hydride, optionally in Presence of finely divided aluminum, silicon or their alloys, silicon dioxide and / or sodium boranate initially under the known conditions of sodium boranate production at temperatures of 300 to 600 ° C. and hydrogen pressures of 3 to 8 atmospheres until the reaction mixture has stopped absorbing hydrogen, then at temperatures of 600 to 850 ° C. and hydrogen pressures of 2 to 5 atmospheres until the elimination of hydrogen from the reaction mixture under these conditions has ended, the sodium dodecahydrododecaborate thus obtained is obtained from the reaction mixture by extraction.