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2,407,332
Patented Sept. 10, 1946
UNITED STATESPATENT OFFICE
I PURIFICATION OF ACETYLEN E BY MEANS
'
OF ARSENIC TRICHLORIDE
Richard B. Wearn and Gordon N. J arman,
'
. United States Army
No Drawing. Application April 21, 1945,
Serial No. 589,687
3 Claims. (01. 260-679)
_ (Granted under the act of March 3,1883, as
' ‘
amended April 30, 1928; '370 0. G. 757),, .
2
1
The invention described herein may be manu
factured and used by or for the Government, for
governmental purposes, without payment to us of
any royalty thereon.
This invention relates to the manufacture of
acetylene and particularly to the puri?cation of
acetylene produced by the usual carbide process.
The puri?cation of acetylene has also been af- '
fected by the use of other materials such as metal
chlorides, speci?cally I-IgCl2 and CuClz.
These
salts reacted readily with substances such as ar
sine and phosphine, but proved to be corrosive to
the steel towers, and the water formed in the
process was found objectionable.
The preferred embodiment of this invention
One of the objects of this invention is to pro
consists in using arsenic trichloride as the main
vide a puri?cation process which will remove sub
stantially all the impurities which are inherently 10 reagent since it combines readily with most of the
usual impurities found in acetylene without pro- ’
present in the gas due to its manufacture.
ducing water or moisture and without producing
A further object of this invention is to carry
undesirable side reactions which are ever present
out the puri?cation of acetylene by a method
in the scrubbing methods heretofore used com
which is cheap, e?icient, reliable, and wherein the
mercially.
material used is readily available.
Preliminary experiments showed that the re
The process forming the subject matter of this
invention consists essentially of using arsenic tri
chloride for the puri?cation of acetylene by the
countercurrent principle.
'
moval of phosphine, arsine, hydrogen sul?de and
ammonia in accordance with this invention is
substantially quantitative.
In practicing this invention the crude acetylene
Other and more speci?c objects of this inven 20
is passed upwardly through a packed tower while
tion will become readily apparent to persons
the arsenic trichloride is sprayed into the top of
skilled in thev ‘art from a consideration of the
the tower over the packing.
following description.
The material used in the packed tower is well
Acetylene made from crude calcium carbide or
dinarily contains the following impurities: phos
phine, arsine, ammonia, hydrogen sul?de and re
lated compounds. These will react with salts of
heavy metals such as are used as catalysts in some
chemical processes such as"v the preparation of
acetylene, vinyl chloride, chloroprene and other
25 known in this art. It may consist of Berl-saddles
or of sections of Raschig rings.
‘
To compare the e?iciency of the different ma
terials used, the following experiment was run.
A measured quantity of the crude gas was
passed through a 3% sodium hypochlorite solu
industrial processes.
These materials are also objectionable in proc
tion. The absorbed impurities, which are known
to be principally phosphine and arsine, were an
esses, in which acetylene is used for heating pur
poses because some of the impurities are trans~
methods. and were reported as “percent phos
posing it into its elements.
trichloride was sprayed downward into and
alyzed by standard colorimetric and gravimetric
formed into poisonous compounds of phosphorus 35 phine” for convenience. The average percentage
found was 0.1%.
and arsenic for instance. In addition, the com
The same quantity of the crude gas was passed
pressed acetylene is highly explosive by shock or
upwardly through a packed tower while arsenic
by catalytic action of the same impurities decom
-
The usual scrubbing with sulfuric acid in steel
towers is not entirely satisfactory because of:
(1) Incomplete removal of the impurities pres
through the tower and then the gas was led
through an adjacent tower containing 3% sodium
hypochlorite solution. The latter was then ana
lyzed to determine the amount of impurities not
ent shown by formation of sludge, when portions
absorbed by the arsenic trichloride. The concen
of puri?ed gas is tested with mercuric chloride re
agent, and
45 tration of these impurities had been reduced to
0.025%.
(2) Loss of an appreciable amount of acetylene
A soda-lime tube was placed in the train be
by reaction with the sulfuric acid.
tween the arsenic trichloride tower and the so
Sodium hypochlorite solutions used for puri?
dium hypochlorite solution to prevent the con
cation of acetylene, remove arsine, phosphine and
similar impurities. But this process possesses a 50 tamination of the latter by arsenic trichloride
vapors.
serious drawback in that it is dangerous, since
The results determined by gravimetric analysis
acetylene, which has been in intimate contact
showed that the removal had been quantitative.
with sodium hypochlorite solution is, under some
The deposit of arsenic and phosphine-arsenic
conditions, yet undetermined, spontaneously in
reduction
products of the absorbed arsine and
55
?ammable.
2,407,332
3
phosphine, took place on a very small area of
the tower packing and in the immediate vicinity
of the inlet tube. This indicates a rapid and
quantitative reaction.
The acetylene, after scrubbing byiarsenic tri
chloride, produced only a slight turbidity when
4
.
skilled in the art, Without departing from the
spirit of the invention or exceeding the scope of
the appended claims.
We claim:
1. A method‘of purifying crude acetylene com
prising intimately contacting the crude acetylene
passed through acidi?ed mercuric chloride solu
with arsenic trichloride.
tion, while the unscrubbed acetylene produced a
2. The process of removing impurities from
heavy precipitate. The ordinary puri?ed or “.cyl
crude acetylene, such as arsine and phosphine, V
inder grade” acetylene produced a slight precipi 10 which comprises intimately contacting the crude
tate in the same solution.
acetylene with arsenic trichloride, and removing
To complete the puri?cation of acetylene the
any'arseni'c trichloride from the puri?ed acet
vapors of arsenic trichloride can be removed by
ylene by scrubbing with water.
Washing the gas with Water or by passing it
3. The process of removing the impurities such
through an alkaline medium.
; as arsine and phosphine from crude acetylene,
While We have shown and described the pre
which comprises intimately contacting said crude
ferred embodiment of this invention, we'wish it
acetylene with arsenic trichloride and removing
to be understood that We do not con?ne ourselves
the: resultant undesirable materials by passing
to the precise details herein set forth, by wayiof
.’the gaseous mix through an alkaline medium.
illustration, as, it is apparent that many changes
RICHARD B. WEARN.
and variations may be'made therein by those
‘ GORDON N. JARMAN.
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