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.