Purification of hydrogen chloride

United States Patent Office 3,446,586 Patented May 27, 1969

3,446,586 0-100° C. Under these conditions, acetylene, ethylene PURIFICATION OF HYDROGEN CHILORDE and vinyl chloride have been found, surprisingly, to react David M. Young, Sarnia, Ontario, Canada, assignor to with the hydrogen chloride to the point where they are The Dow Chemical Company, Midland, Mich., a cor converted essentially entirely to ethylidene chloride and poration of Delaware V ethyl chloride. These chlorinated hydrocarbons, plus any No Drawing. Filed Dec. 19, 1966, Ser. No. 602,463 traces of Such compounds originally present in the gas Int. C. C01b 7/08, C07c 17/08 stream, are then removable by conventional means, such U.S. C. 23-154 7 Claims as contacting the effluent reacted stream with activated charcoal, by low temperature distillation or other suitable 0 means. By this process, the concentrations of unsaturated

ABSTRACT OF THE DISCLOSURE hydrocarbons and chlorinated hydrocarbons in the treated Hydrogen chloride contaminated with minor amounts hydrogen chloride can be reduced to less than 50 parts of unsaturated organic impurities such as that derived per million and if desired, to less than one part per mil from the thermal dehydrochlorination of ethylene di lion, thereby making available the above byproduct stream as a new and cheaper source of pure anhydrous hydrogen chloride is contacted in the vapor phase with anhydrous chloride.

aluminum chloride at 0-100° C. and under superatmos pheric pressure to convert the unsaturated contaminants Although this purification process is primarily useful to the corresponding Saturated chlorides. These chlorides in purifying the impure hydrogen chloride obtained from can be removed by adsorption on activated carbon or by the cracking of ethylene dichloride, it is obviously applica other Suitable means to produce a highly purified hydrogen 20 ble to any such hydrogen chloride product containing chloride. similar contaminating amounts of olefinic and acetylenic hydrocarbon impurities, particularly those of 2-3 carbon

This invention relates to an improved method for mak atoms, and their monochloro derivatives. In other words, ing highly purified hydrogen chloride. It relates particu 25 aallene, hydrogen chloride stream containing methylacetylene, larly to a method whereby an impure hydrogen chloride with or orwithout propylene and their monochloro derivatives, the additional presence of acetylene and stream derived from the thermal cracking of ethylene ethylene with a total hydrocarbon concentration of 0.01-1 dichloride can be freed from certain unsaturated percent, is also effectively purified by the present process. impurities.

The hydrogen chloride byproduct stream from the 30 withIt ishydrogenknown that ethylene and acetylene can be reacted chloride in the presence of a metal halide cracking of commercial ethylene dichloride to vinyl chlo catalyst to produce the corresponding adducts. For exam ride contains a number of gaseous impurities which can be ple, acetylene is reacted with hydrogen chloride on a com removed in large part by conventional procedures. The mercial scale in the presence of a mercuric chloride cata partially purified material thereby obtained is suitable as lyst to produce vinyl chloride and ethylidene chloride. a technical grade of hydrogen chloride for many uses, Another commercial process involves the liquid phase in which the minor quantities of remaining impurities are reaction of ethylene with hydrogen chloride in the pres inert or can be disregarded as insignificant. However, it ence has been considered to be economically impractical to presentof processaluminum chloride to make ethyl chloride. The has several points of difference from these purify this stream further to the point where essentially no known processes.

impurities remain, thereby making this byproduct stream 40 carried out in the gasForphase example, the present process is a source of Super-pure hydrogen chloride. The impurities ated at ambient temperaturethroughout and it can be oper present in such a stream after ordinary separation and the unsaturated impurities. Known gas phaseextinction to the practical of reactions of purification procedures consist essentially of the saturated this type are usually operated at elevated temperatures and unsaturated hydrocarbons methane, ethane, acetylene, and even under such conditions, the conversions obtained and ethylene present in contaminating amounts, i.e., a are often less than fifty percent of the theoretical. The total hydrocarbon concentration of no more than one per cent by volume. Traces of saturated and unsaturated essential completion of hydrochlorination and the mod erate reaction conditions required to obtain this result in chlorinated hydrocarbons may also be present. The un the present process, therefore, are unexpected and could saturated hydrocarbons acetylene and ethylene normally constitute the bulk of the total hydrocarbon impurities, 50 notTemperature have been predicted from the prior art.

of 0-100° C. can be employed for the running about 0.01-0.5 percent of the stream. Of these, hydrogen chloride reaction, but it is usually preferred acetylene is usually the major contaminant.

Economically practical removal of such impurities to carry out this reaction at about normal ambient tem presents a difficult problem. The Saturated hydrocarbons perature, that is, about 10-40 C. The reaction takes place to some extent at any pressure. However, essential can be separated by a low temperature distillation and the 55 completion traces of chlorinated hydrocarbons often present can be operation ofofthethepresent reaction is necessary to the practical process. It has been found that adsorbed on activated charcoal, but neither of these proce such essentially complete conversion is obtained at super dures is adequate for the required essentially complete atmospheric pressures, preferably of at least five atmos removal of acetylene and ethylene and vinyl chloride in pheres. At the preferred temperature range mentioned, order to make a high purity hydrogen chloride. Such 60 reaction pressures of 8–50 atmospheres are particularly hydrogen chloride has been made in the past by the direct preferred, the combination of pressure and temperature combustion of hydrogen in chlorine. being such that the hydrogen chloride is in the gas phase. It has now been found that a hydrogen chloride stream containing minor amounts of unsaturated hydrocarbon Contact times suitable to obtain complete reaction are contaminants such as that derived from the thermal 65 dependent upon pressure and temperature conditions; dehydrochlorination of ethylene dichloride as described also upon the amount, activity and state of Subdivision of above can be purified and the olefinic and acetylenic the catalyst. Contact times of at least 5 seconds are suit hydrocarbons and the unsaturated monochloro deriva able. Within the preferred limits of pressure and tem tives thereof can be removed essentially completely by a perature as described above and using smaller than 20 process which comprises contacting that stream in the 70 mesh aluminum chloride dispersed on glass wool, con gas phase and under essentially anhydrous conditions tact times of 10-600 seconds are sufficient, calculated on with solid aluminum chloride at a temperature of about the basis of the empty column.