DE1067005B - Process for the production of boranates - Google Patents

Description

φ st 9

F 23740 IVa / 12i

REGISTRATION DATE: AUGUST 12, 1957

NOTICE
THE REGISTRATION
AND ISSUE OF THE
4 EDITORIAL: OCTOBER 15, 1959

The chemical literature contains a large number of methods for the preparation of alkali boranates has been described by reacting metal hydrides with boron compounds.

Thus, by reacting sodium hydride with boric acid esters or sodium methoxyborate, one obtains or boric anhydride sodium boronate:

4NaH + B (O

NaBH ₄ + 3NaOCH ₃ Process for the production of boranates

Applicant:

Paint factories Bayer Aktiengesellschaft, Leverkusen-Bayerwerk

3NaH + NaBH (OCHg) ₃ -> NaBH ₄ + 3NaOCH ₃

4NaH

2B ₂ O ₃ -

NaBH ₄ + 3NaBO ₂ ,

instead of sodium hydride, sodium metal and hydrogen can also be used. the Reactions are carried out at high pressure.

Sodium can also be obtained by reacting hydrogen, at least one boron compound and a dispersion of one or more finely divided alkali metals at temperatures between 250 and 350 ° C, preferably under hydrogen pressure. Boron halides, organic addition products, serve as boron compounds Boron halides, boric acid esters, boron oxide, alkali metal boron halides:

4Na + 2H ₂ + BF ₃ - ^ NaB H ₄ + 3 NaF, 4 Na + 2 H ₂ + B (O CH ₃ ) ^ NaBH ₄ + 3 Na (OCH ₃ ),

^ NaBH ₄ + 3NaBO ₂ , 3 <>

Dr. Friedrich Schubert, Dr. Konrad Lang, Leverkusen,

and Dr. Werner Schabacher, Cologne-Mülheim,

have been named as inventors

halide generated in the presence of catalysts: B (OCH ₃ ) ₃ .

6LiH + 2BF ₃
2LiH + B ₂ H ₆

h- B ₂ H ₆ + 6LiF -> 2LiBH ₄ .

4Na + 2H ₂ + 2B ₂ O ₃ -4Na + 2H ₂ + NaBF ₄

-NaBH ₄ + 4NaF.

The reaction takes place in inert suspending agents, preferably mineral oils, in which the boranate is insoluble. The alkali metal must be very finely dispersed, what by application of high speed stirrers (3000 to 6000rpm) in reaction vessels of special construction is achieved. In the subsequent extraction of the pure boranate, the mineral oil must first be used 'Carefully removed by washing with petroleum ether, then the boranate with isopropylamine or ammonia is extracted from the reaction product.

According to US Pat. No. 2,729,540, boranates are produced by reacting alkali metal hydrides and alkaline earth metal hydrides or the free metals with boron trialkyls and hydrogen under high pressure and 200 to 300 ° C.

NaH + B (C ₂ H ₅ ) ₃ + 3H ₂ - ^ NaBH ₄ + 3 C ₂ H ₆ .

The reaction of diborane with lithium hydride also yields lithium boronate. Here is diborane by reaction of lithium hydride with boron-Likewise, the reaction of alkali metal hydrides yields or alkaline earth metal hydrides with boron oxide at 200 to 350 ° C in the presence of a metal alkoxide Boranate, the reaction being carried out in a steel ball mill.

All of these processes have disadvantages which impair their technical usability. The use of the relatively easily accessible boron oxide results in _{a theoretical boron yield of only 25% because of the formation of NaBO 2} ; the practical results are 19% of theory (without grinding) and 64% of theory (with simultaneous grinding). Boric acid methyl ester, the most important boron compound used for the production of boranates, forms an azeotrope with methanol that is difficult to break down, so its extraction is very laborious. The conversion of the borate ester with sodium metal and hydrogen in mineral oils is undoubtedly a significant advance, but it requires considerable technical effort: high-speed stirrers with specially shaped stirrers and tank walls, the stirrers have to work at 3000 to 6000 rpm against 7 to 10 atm hydrogen at 250 to 350 ° C can be safely sealed; the oil used as a dispersing agent must be able to withstand a permanent load of 250 to 350 ° C. in the presence of sodium or sodium hydride and optionally boron halides. Because of the solubility of the oils in isopropylamine or ammonia, the reaction product must be carefully freed from oil before it is extracted. These technical difficulties are expressed in the

909 638/360 a

relatively high price of the sodium boronate, which is obtained by the process described will.

One of the other methods described in the description of the prior art is implementation not yet known in the technical scope.

A process that has not been published in advance has brought about a significant advance in this area Production of boranates by reacting boron compounds with metal hydrides, which thereby it is characterized that a hydride of the metals A ^ ' Mg, Ca, Sr, Ba, Li, Na, K (Rb, Cs) with a metav borate (or a metal oxide-boron oxide mixture comparable Composition) of a metal this! Row that does not continue in the order listed on the left is the hydride metal that is reacted at temperatures above 100 ° C. The metal hydride can be generated during the reaction by processes known per se. The reaction mixture solid acid anhydrides can also be added. According to this procedure, boranates can be obtained much more economically than before.

The invention relates to a process for the preparation of alkali boronates by reacting metal hydrides with boron compounds, which is characterized in that alkali borates or metal oxide-boron oxide mixtures in a molar ratio other than IMe ₂ OzUlB ₂ O ₃ with alkali metal hydrides or alkali metals and hydrogen with or without Application of hydrogen overpressure at temperatures above 100 ° C can be implemented.

It has been found that for the production of alkali borates it is not necessary to start from metaborates, but that the reaction with alkali metal and hydrogen or alkali metal hydride can be subjected to alkali borates in general and with the best results: it is precisely advantageous to use higher borates , so to use those with a ratio Me ₂ O: B ₂ O ₃ <1: 1.

It has also been found that the yields are significantly improved if certain additives are added to the mixture of alkali borate and alkali metal or hydride. These additives +5 can be divided into two groups:

a) Substances that chemically react with the resulting alkali oxide. As such come into consideration z. B. calcium chloride (formation of alkali metal chloride and calcium oxide) or z. B. acid anhydrides, like silica.

b) Chemically inert substances, which dilute the reaction mixture, also have a reaction-promoting effect. Of the large number of substances that can be used for this purpose, table salt and feldspar are considered called.

The reactions then proceed according to the following scheme:

Na ₂ O: B ₂ O ₃ = I: 4

Na ₂ B ₈ O ₁₃ + 32 Na + 16 H ₂ +13 Si O ₂ ->-> 8NaBH ₄ + 13Na ₂ SiO ₃ .

It follows from the equations that the higher the boron content of the borate used, the less Silica must be used, in other words, the ballast of sodium silicate decreases. the end for this reason the use of higher borates is more advantageous. For reasons of economy However, if the use of the borax or lit is easily accessible by simply draining it, j η prefer sodium tetraborates. I.

It is known for the production of alkali hydrides an alkali metal with a finely divided inert solid and a relatively small one Amount of abietic acid to mix and this mixture exposure to hydrogen at temperatures subject to above the melting point of the alkali metal.

In the process according to the present invention, the reaction is carried out at temperatures above 100 ° C, advantageously between 350 and 550 ° C through.

In order to prevent decomposition of the sodium boronate, it is advantageous to work at hydrogen pressures from 2 to 6 atm. Since sodium boronate is resistant up to 400 ° C, the reaction can also be carried out without pressure if you take care of maintaining a correspondingly lower reaction temperature wearing.

In contrast to all previously known methods, this is the case with the method according to the invention not necessary, the range of existence of the alkali metal hydrides given by pressure and temperature to be observed. According to Gmelin, Handbook of Inorganic Chemistry, Syst. N / 21, p. 162, is the dissociation pressure of the sodium hydride in mm Hg given by the equation:

5700

+ 2.5 log T + 3.956.

An extrapolated dissociation pressure of

0 atü = 1 ata

1 atü = J. ata

2 atü = 3 ata

3 atü = 4 ata

4 atü = jTata

5 atü = h ata

6 atü = £ ata

7 atü = £ ata

at
at
at
at
at
at

424 ° C
447 ° C
462 ° C
472 ° C
480 ° C
487 ° C

at 493 ° C
at 498 ° C

Na ₂ O: B "O, = 3:

Na ₈ BO ₈ + 4Na + 2H ₂ + 3 SiO ₂

60

NaB H ₄ + 3 Na ₂ Si O ₃

Na ₂ O: B ₂ O ₃ = I: 2

Na ₂ B ₄ O ₇ + 16Na + 8H ₂ + 7 SiO ₂ ^ - ^ 4NaBH ₄ + 7Na ₂ SiO ₃ As example 1 shows, the reaction can easily be carried out at 500 ° C and 3 atmospheric pressure, i.e. outside the range of existence of sodium hydride (Decomposition pressure at 500 ° C: about 7.3 atmospheres). The conversion proceeds just as well within the range of existence of NaH, as shown in Example 2: 3 atmospheres, 450 ° C. (The dissociation pressure at 450 ° C. is approximately 1.2 atmospheres.)

According to J. Amer. Chem. Soc, 75, p. 208 (1953) the reaction of sodium hydride with boron oxide according to the equation

4NaH + 2B ₂ O ₃

NaB H ₄ + 3 NaB O ₂ ,

Na ₂ O: B ₂ O ₃ = I: 3

Na ₂ B ₆ O ₁₀ + 24Na + 12H ₂

where the yields 19% of theory (without equal-10SiO ₂ - ^ simultaneous grinding) or 64% of theory (under the same-

6NaBH ₄ + 10Na ₂ SiO ₃ 70 times grinding over 46 hours).

It must therefore be surprising that the implementation of higher borates, e.g. B. Tetraborate, not after equation

2Na ₂ B ₄ O ₇ + 4Na + 2H ₂

NaBH ₄ + 7 NaBO ₂ + χ SiO ₂

but according to the equation
Na ₂ B ₄ O ₇ + 16Na + 8H ₂ + 7SiO ₂

-> 4NaBH ₄ + 7Na ₂ SiO ₃

takes place with quantitative conversion of the boron introduced, and furthermore that since, according to the American literature cited above, sodium borate no longer reacts, the considerably more basic sodium orthoborate Na ₃ BO _{3 can be converted} to almost quantitative conversion. The method according to the invention also brings about a number of significant technical advances:

The reaction proceeds without or with the use of only a slight excess hydrogen pressure. she can can therefore be carried out in normal chemical apparatus.

The raw materials sodium metal and dehydrated borax are easily accessible and inexpensive Products. The reaction product does not need to be carried out in mineral oil as in the case of the one mentioned above Process to be cleaned laboriously before the extraction, but can practically directly to the leaching 3 « be subjected.

The sodium metasilicate obtained as a by-product when quartz flour is added is a valuable technical one Substance that can be put to further use directly.

example 1

In a stirred autoclave, an intimate mixture of 201 g of dehydrated borax ground in a ball mill, 368 g of metallic sodium and 420 g of extremely finely powdered quartz flour is heated to 500 ° C. for 4 hours. The reaction mixture is under a hydrogen pressure of 3 atmospheres. The Reakjftionsprodukt obtained is fhiert Extra -_ ^ ⁵ with flüssigem_Ammoniak. _{Sodium MxTranat with a NaBH 4} content of 96% is obtained in excellent yield.

As a by-product arises according to the equation

Na ₂ B ₄ O ₇ +16 Na

7 Si O ₂ + 8H ₂

= 4NaBH ₄ + 7Na ₂ SiO ₃

Sodium metasilicate which is profitably used for known industrial uses is used.

Example 2

An intimate mixture of 201 g of dehydrated and ground in a ball mill is placed in a stirred autoclave Borax, 368 g of metallic sodium and 400 g of feldspar at an excess hydrogen pressure of

Stirred 3 atmospheres at 450 ° C for 4 hours. The cooled reaction product is extracted with liquid ammonia. _{Sodium boronate with a NaBH 4} content of over 96% is obtained in excellent yield.

Example 3

Na ₃ BO ₃ + 4 Na

2 H ₂ + 3 SiO ₂ -

NaBH, + 3Na "SiO,

10 in a stirred autoclave, a mixture of 384 g of finely ground sodium orthoborate, Na ₃ BO _3, 540 g of quartz sand and 276 g of sodium is heated atm under a hydrogen pressure of 2 to 5 The exothermic reaction begins at 340 to 400.degree. C. and is controlled with the aid of the supply of hydrogen and by cooling so that the temperature does not exceed 500 to 550.degree. Implementation is "terminated after ό hours. After cooling, the sodium borohydride recovered in good yield from the Reaktionsm it on m oniak, or isopropyl extra Jj

mixture
here.

Na ₂ B ₆ O ₁₀

Example 4
■ 24Na + 10SiO _{2 2}

- ^ 6NaBH ₄ + 10Na ₂ SiO ₃

As in Example 3, a mixture of 271 g of finely ground sodium triborate Na ₂ B ₆ O ₁₀ with 552 g of sodium and 600 g of quartz sand is heated to 400 to 550 ° C. under a hydrogen pressure of 2 to 6 atmospheres. The sodium chloride yield is 75% of theory.

Example 5

Na ₂ B ₈ O ₁₃ 32 Na + 13SiO ₂ + 16H ₂ -

-8NaBH ₄

13Na ₂ SiO ₃

As in Examples 3 and 4, a mixture of 340.4 g of finely ground sodium tetraborate Na ₂ B ₈ O ₁₃ with 736 g of sodium and 780 g of quartz sand is heated to 400 to 550 ° C. under a hydrogen pressure of 2 to 6 atmospheres. The yield of sodium boronate corresponds to the result given in Example 4.

Claims (1)

Claim: A process for preparing Alkaliboranaten by reacting metal hydrides with boron compounds, characterized in that Alka ^ j- _bo £ ate od ^he metal oxide-boron oxide mixtures m a molar ratio other than 1 Me ₂ O to 1 B ₂ O ₃ with alkali metal hydrides or alkali metals, and Hydrogen can be reacted with or without the use of excess hydrogen pressure at temperatures above 100 ° C. Considered publications:
U.S. Patent No. 2,768,064. Cited older patents:
German Patent No. 1 036 222. 909 638 / 360a 10.59