Improved Method for Producing Nitrides and Ammonia.
Year: 1895

page_text: Date of Application, 27th June, 1895
Complete Specification Left, 26th Mar., 1896-Accepted, 23rd May, 1896
PROVISIONAL SPECIFICATION.
Improved Method for Producing Nitrides and Ammonia.
I, HERMANN MEHNER, of Savigny Platz 5, Charlottenburg in the Kingdom of
Prussia, and Empire of Germany, Doctor of Philosophy, do hereby declare the
nature of this invention to be as follows:-
The present invention relates to the production of nitrides, such for instance as
boron-nitride, silicium-nitride, titanium-nitride, magnesium-nitride, vanadium-nitride
and others, and it consists in exposing a mixture of carbon and oxygen compounds
of such radicles as will combine with nitrogen at high temperatures, to the heat of
an electric furnace and passing nitrogen gas, or a mixture of nitrogen gas with other
gases, or air, through the said mixture while being thus heated. The nitrogen
contained in the nitride formed can be obtained in the form of ammonia by treating
the nitride with steam, leaving behind an oxygen compound which can immediately
be used for a subsequent operation after having been mixed with carbon, by
preference with coke.
Dated this 27th day of June 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.
Improved Method for Producing Nitrides and Ammonia.
I, HERMANN MEHNER, of 5 Savigny Platz, Charlottenburg, in the Kingdom of
Prussia, and Empire of Germany, Doctor of Philosophy, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
The compounds of nitrogen known under the name of "nitrides" with other
radicles, such as boron nitride, silicon nitride, titanium nitride, magnesium nitride
and others, although they constitute among others an advantageous, rich and easily
accessible source of ammonia, have up to the present time received only scientific
attention. The industries were precluded from their manufacture and consequently
from their use, because no means were at disposal to supply to the said radicles the
enormous degree of heat necessary for the reaction, or to effect the reduction of
the compounds of the radicles to be combined with the nitrogen and the combination
of nitrogen by the said radicles in one operation, which alone is found to be a
rational mode. By the invention of the electrical furnace the industries have now
been placed in a position to produce an enormous heat within the substances to be
acted upon, thus providing also for the possibility of employing industrially an
advantageous means for utilizing elementary nitrogen, particularly also the
nitrogen of the air, a means the value of which is augmented by the fact that it
frees for instance the manufacture of ammonia from the troublesome and dangerous
handling of cyanides.
For manufacturing nitrides on a commercial scale I proceed by exposing oxygen
compounds of the radicles which, like boron, silicon, magnesium, titanium, vanadium,
and the like, are capable of combining with nitrogen at a high temperature, and
which I mix with carbon or coke, to the heat of an electric furnace, with the

page_text: simultaneous passage of nitrogen, air or an appropriate mixture of gas containing
nitrogen, for instance generator gas. Under these circumstances the carbon reduces
the oxygen compound to form boron, silicon, magnesium or the like by combining
with the oxygen of the same to form carbonic oxide or carbonic acid, and the
radicles set free unite with the nitrogen to form nitride. The latter is withdrawn
from the furnace at a suitable place below the zone of the electrodes.
For example in order to manufacture silicon nitride, carbon and sand (quartz)
are mixed in proper stocchiometric proportions, the mixture is introduced into an
electric furnace, and is heated in the same by means of a high-tension current,
while an ample quantity of generator gas is at the same time conducted through
the mixture. A high-tension current must be employed, because an extremely high
resistance has to be overcome. In case no high-tension current is at disposal the
object may be achieved in the following manner: An electric furnace is fed with
coarse pieces of coke, and a uniform jet of sand is blown in with the aid of an
appropriate mechanical device, generator gas being at the same time introduced; on
entering the hot zone the sand evaporates and then reacts as desired. The aforesaid
other substances are treated in like manner.
When effected by means of the electric furnace the manufacture of nitrides
becomes an industrial process capable of being carried out on a large scale, which
cannot be realized by heating the reaction vessels externally. So-called refractory
retorts, apart from being chemically acted upon by the charge, are found to be too
insufficient non-conductors of heat for the temperature necessary in the interior.
On the other hand iron retorts, by reason of the exceedingly rapid wear, are
rendered unfit for use in such a short time that the manufacture on a large scale is
out of the question. This wear is quite inevitable, for the use of gas-firing free
from ashes with a neutral flame is. precluded, because at the necessary high
temperature the carbonic acid has the same oxidizing action upon the iron as free
oxygen; but the employment of a reducing flame which would have to contain for
1 part of carbonic acid quite two parts of carbonic oxide, is not capable of
furnishing the heat required for the reaction on account of the incomplete
combustion of the heating gas necessary for obtaining the same. The covering of
iron retorts with refractory material. is precluded by reason of the bad heat
conducting property of the latter. I am aware that it has already been proposed
and attempted to effect the production of boron nitride on an industrial scale with
the aid of borates; this attempt has however failed because of the double action
upon the iron reaction vessels (those of chamotte being altogether excluded) by the
external heating and the charge, the latter eating away the iron even before the
reaction has properly commenced. In the case of internal heating by means of
the electric current, furnace walls made of quartzose slate and even of chamotte
are found to have scarcely melted at the surface.
The nitrogen contained in the nitrides manufactured can be easily converted into
ammonia by treating the same with water vapour, an oxygen compound being then
obtained as a residue which with the addition of the necessary carbon (coke) is
used directly for a fresh operation.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
A method of manufacturing nitrides characterized by the feature that oxygen
compounds of the radicles which, like boron, silicon, magnesium, titanium, vanadium
and the like, will combine with nitrogen at a high temperature, are exposed to the
heat of an electric furnace in the presence of free nitrogen and carbon.
Dahi och 1.
L ML 1000
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.