Sciencemadness Discussion Board

Boron oxide reduction using sodium?

Steamboy - 29-1-2017 at 02:31

I recently had considered making elemental boron, however, my lack of magnesium (used in the typical process: 3Mg + B2O3 = 2B + 3MgO) made me look for alternative methods of manufacturing, including molten boron oxide electrolysis and Reduction with aluminum. Later I abandoned the idea because of the non-viability of these methods.

Now, I have been able to manufacture and purify metallic sodium from the electrolysis of molten caustic soda, and I wondered whether it was possible to reduce boron oxide and even boric acid using such.

The idea is to reduce boron using sodium:
B2O3 + 6 Na = 2 B + 3 Na2O
B (OH) 3 + 3 Na = B + 3 NaOH
This requires a little too much sodium, I know.

My questions are as follows:
Is this really viable (will there be many or few impurities)?
Is it possible to separate the resulting NaOH and Na2O from the metal boron?
What are the minimum temperatures to start the reaction?
Is it recommendable to compress the mixture of sodium and boron oxide in a pellet (or even confine it in a closed space, without air) to get the formation of larger boron droplets and minimize the reaction of sodium with air?
Is it advisable to use boron oxide powder in molten sodium?

[Edited on 29-1-2017 by Steamboy]

elementcollector1 - 29-1-2017 at 10:27

The NaOH and Na2O can be separated from the boron by washing with ice-cold water. They'll dissolve, though the sodium oxide will react violently.

Impurities in the boron would be mainly sodium, as I doubt this process is exothermic enough to produce the required energy to melt the boron into lump form. It will likely be a fine powder.

The minimum temperature to start the reaction will probably be pretty high - a blowtorch could likely set it off.

DO NOT compress the mixture of sodium and boron oxide. This could create an explosive mixture, and won't really help in protecting the sodium from air or increasing the boron particle size.

That idea could work, but you would have to be very careful.

Why not go out and buy some magnesium? It's about as cheap as the boron oxide and reagents required to make sodium.

Dan Vizine - 1-2-2017 at 19:36

I see two problems:

B (OH) 3 + 3 Na = B + 3 NaOH
This reaction scheme is imaginary. It won't proceed as written.

B2O3 + 6 Na = 2 B + 3 Na2O
Is this meant to be a Goldschmidt type reaction? If so, I don't know of any which proceed with sodium. Not because of thermodynamics, but because Na boils so much lower than the reaction proceeds at.

I've done it with magnesium, I think you should consider it, too.