GB822863A - Improvements in or relating to a process for the treatment of gases obtained by hydrocarbon pyrolysis - Google Patents

Abstract

Gases obtained by pyrolysis of hydrocarbons are treated to obtain acetylene and olefines separately in a substantially pure state by first washing the pyrolysis gas with liquid ammonia under atmospheric pressure and at - 70 DEG C. to - 60 DEG C. to form an ammoniacal solution containing substantially all of the acetylene and only a minor quantity of the olefines, and leaving a gas rich in olefinic hydrocarbons and substantially free from acetylene, compressing the ammoniacal solution to a pressure of several atmospheres and then subjecting it to a partial reduction of pressure at a temperature in the range of 25 DEG C. to 40 DEG C., thereby desorbing the olefines with a small quantity of acetylene which are returned to the washing zone and leaving an ammoniacal solution of acetylene substantially free from olefines, and thereafter distilling the ammoniacal solution to separate the acetylene from the ammonia. In an example a gas mixture obtained by the pyrolysis of light petrol containing 7% acetylene, 6% propylene and 16.5% of ethylene is treated at - 70 DEG C. at atmospheric pressure. The ammoniacal solution is compressed to 18 atmospheres and is then partially desorbed at 40 DEG C. and then distilled to give 99.9% acetylene. The gas issuing from the absorption tower comprises propylene and ethylene together with some acetylene and also ammonia which is removed by sulphuric acid treatment.