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Jan.‘ 14,
Filed Sept. 15, 1942
Patented Jan. 14, 1947
Roman R. Miller, Washington, D. ‘C.
Application September 15, 1942, Serial No. 458,439
5 Claims.
(Cl. 252-184)
(Granted under the act of March 3, 1883, as
amended April 30, 1928; 370 0. G. 757)
This invention relates to the oxidation of alkali
metals, and it is particularly directed to a method
of preparing potassium tetrcxide and mixed
higher oxides of sodium and potassium.
It has long been known that various alkali
metal higher oxides are capable of giving up oxy—
gen to the air, under certain conditions, and also
of absorbing carbon dioxide to V9. greater or less
extent. Therefore, these materials are used in
breathing equipment designed either to protect
the user from toxic gases or to purify or regen
crate a limited supply of air.
Of the various
higher oxides the most eilicient from the stand
point of ava-
e oxygen per weight of the oxide
is potassium tetroxide.
with oxygen, and in practice it is most con
venient to bring the metal vapor into contact
with an excess of air (which may be further di
luted or enriched with oxygen) so that all of the
vapor will be oxidized to the highest oxide. Al
though the oxidation may be carried out at re
duced or increased pressure there is no advantage
in doing so, and the temperature of the metal
vapor (before burning) is most conveniently reg
ulated by employing different concentrations of
an inert gas, such as nitrogen, to carry the vapor
into the burning chamber, if operation at the
boiling point of the metal is not desired. How
ever, in the preferred form of the invention the
Sodium peroxide yields 15 metal or mixture of metals (particularly a mix
less oxygen but it generally reacts more quickly,
ture of sodium and potassium) is vaporized at the
in the beginning of the reaction, with moisture in
boiling point.
the air, possibly due to the formation of hydrates.
In order that the invention may be more clear
Accordingly it is common practice to use a mix
ly understood a typical operation for the oxidation
ture of potassium tetrox" "o (K204) and sodium
of potassium is described, with reference to the
peroxide (NazGz)
eoui~ out for air regenera
accompanying drawing.
tion although the pure potassium tetroxide can
In the drawing, potassium metal is melted in a
be used alone to yield a greater quantity of oxy
heated reservoir Ill and the liquid metal ?ows
through a conduit ll, controlled by a valve l2,
It has heretofore been difficult to prepare po
tassium tetroxide, sodium peroxide and mixtures
'' into a furnace iii.
The furnace l3 consists of an
iron chamber l4 electrically heated by a coil l5
pure form on a commercially practi
and covered with heat insulation l6. In the
cable sea .
Various methods which have been
furnace 53 the potassium is vaporized and the
include dissolving the alkali metal in
vapor removed by passing nitrogen into the cham
liquid ammonia and bubbling oxygen through the 30 ber ill through a conduit IT. The nitrogen is presolution, and of course burning the metals and
heated in the conduit ll, by means of a heating
their alloys in either liquid or solid form in air
coil is, in order to prevent condensation of potas
or pure oxygen.
The former method yields a
sium vapor as it is removed for burning. The
mixture of nitrogen and potassium vapor passes
through an exit tube l9 which is also heated by a
coil Ell to prevent condensation of potassium.
From the exit tube It the nitrogen and potassium
vapor pass into a burning chamber 2| into which
the former, but it- is virtually impossible to obtain
air is introduced through a conduit 22. As the
a pure product. At best a mixture of higher and 40 air and potassium vapor meet the latter imme
lower oxides is produced, often including tiny
diately ignites and burns to the tetroxide which
particles of the unburned metal in the oxide ash.
appears as an extremely ?ne, ?u?y powder, most
This invention provides a method of preparing
of which settles slowly as the nitrogen and un
the alkali metal higher oxides substantially free
used air pass out of the burning chamber 2|.
from lower oxides and metal, simply and eco 45 Some of the tetroxide is so ?nely divided that it
Without the attendant hazards of
remains as a smoke, and it is removed as the exit
the prior known processes of preparing the pure
gases leave the chamber 2| and pass through a
material. the higher oxides (e. g. K204 and
conventional Cottrell precipitator 23. By scrap
fairly pure product but it is very expensive, re
quLes rigid control andvpresents an explosion
haz" rd in the unavoidable gaseous mixture of am
monia and oxygen. The latter method, on the
other hand, avoids the hazards and costliness of
N .09 may be obtained in pure form or in ad
ire with one another.
ing the sides of the precipitator 23 periodically
The method of this 50 the tetroxide particles are caused to fall into a
inv ltion is particularly useful for the prepara
collecting vessel Ell. The unused air and nitrogen
tion of potassium tetroxide.
pass out of the system through a vent 25. Other
The process of this invention comprises the di
collecting means than a Cottrell precipitator may
rect oxidation of the alkali metal in vapor form
be employed to collect the oxide. A series of col
by bringing the metal vapor directly into contact 55 lecting drums or entrainment traps have been
successfully used, especially in large scale op
It is desirable, although not essential, that the
nitrogen used to carry the potassium vapor from
the chamber Ill be free from oxygen, for if even
small amounts of oxygen are present there is a
as the vapors may be led directly from the reac
tion zone to the burning chamber.
Many other variations will be apparent to
those skilled in the art and the invention should
not be limited other than as de?ned by the ap
pended claims.
The invention described herein may be manu~
tendency for potassium tetroxide to build up in
factured and used by or for the Government of
the exit tube l9 and eventually plug it up. It is
the United States of America for governmental
essential that both the nitrogen and the air used
for burning the potassium be as free as possible 10 purposes without the payment of any royalties
thereon or therefor.
of moisture, as otherwise the tetroxide will be
I claim:
contaminated with lower oxides and sometimes
1. Process for making alkali metal higher
potassium hydroxide. Similarly these gases
oxides which comprises vaporizing the alkali
should be free of carbon dioxide if the presence
of carbonates in the product is to be avoided. 15 metal, carrying the vapor away from unvaporized
metal by means of an inert gas, bringing the
Other inert gases may be employed instead of
vapor into contact with oxygen and collecting
nitrogen, such as helium, but nitrogen is most
the alkali metal oxide thus formed.
practically obtainable. If desired the nitrogen
2. Process for making alkali metal higher
may be dispensed with and pure potassium vapor
brought into contact with the air in the burning 20 oxides which comprises vaporizing the alkali
metal, carrying the vapor away from unvaporized
metal by means of a stream of nitrogen, bringing
Above about 500° C. the vapor pressures of the
the mixture of nitrogen and alkali metal vapor
alkali oxides increase fairly rapidly with tem
into contact with dry air and collecting the alkali
perature and in the case of potassium it reaches
760 millimeters (the boiling point) at 760° C. 25 metal oxide thus formed.
3. Process for making mixed sodium and
Therefore it is most practicable to operate the
potassium higher oxides which comprises vapor~
furnace l3 at some temperature above about 500°
izing a mixture 01" sodium and potassium metals,
C., and for large scale operation the most satis
factory operating temperature is the boiling
point of the alkali metal or mixtures of alkali
metals. This is particularly true for mixtures
of sodium and potassium. However, the precise
operating temperature which is most ei?cient for
a given installation depends on a number of engi
neering factors, such as furnace size, cost of fuel 35
for heating, etc.,‘ and it is easily determined by
carrying the vapor mixture away from un
vaporized metal by means of a stream of nitrogen,
bringing the vapor mixture and nitrogen into
contact with dry air and collecting the mixed
oxide thus formed.
4. Process for making potassium tetroxide
which comprises vaporizing potassium metal,
carrying the vapor away from unvaporized metal
by means of a stream of nitrogen, bringing the
those skilled in the art.
mixture of vapor and nitrogen into contact with
Similarly sodium metal may be substituted for
dry air and collecting the oxide thus formed.
the potassium referred to in the above operation,
5, Process for making sodium peroxide which.
and, as already indicated, mixtures or alloys of 40
comprises vaporizing sodium metal, carrying the
sodium and potassium may be employed, the
vapor away from unvaporized metal by means of
composition of which depends on the proportion
a stream of nitrogen, bringing the mixture of
of potassium and sodium oxides desired in the
vapor and nitrogen into contact with dry air and
product; The process is particularly adapted for
the oxidation of the sodium-potassium vapor 45 collecting the oxide thus formed.
mixtures obtained by the decomposition of molten
potassium salts by contact with sodium metal,
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