GB390863A - Improvements in the recovery of ethylene - Google Patents

Abstract

Ethylene is recovered from gases rich in ethylene and containing also propylene and/or other olefines, especially cracking still gases, by washing the gases with a mineral oil fraction approximating to kerosene and substantially all boiling above 200 DEG C. at ordinary pressure, the propylene and higher olefines being absorbed, while the ethylene remains undissolved. The washing may be effected at normal pressure, but is preferably effected at pressures above 10 atmospheres. The dissolved gases may subsequently be liberated from the kerosene by heating and/or reduction of pressure in stages, the resulting gas fraction or fractions poor in propylene being returned to the washing step, preferably to the appropriate stage of the multi-stage compressor when such is used, while the fraction or fractions rich in propylene are collected separately for the recovery of propylene therefrom. According to an example, cracking still gases are washed at 22 DEG C. with kerosene boiling between 200 and 300 DEG C. in countercurrent, in an unpacked tower 2 inches in diameter and 12 feet high. The gases are compressed before scrubbing to a pressure of 21 atmospheres, and the gases dissolved in the kerosene subsequently liberated in two stages by reduction of pressure, first to 7 atmospheres, then to atmospheric pressure. The ethylene and propylene obtained may be used for the manufacture of derivatives such as ethyl alcohol or ethylene glycol in known manner. The gas recovered from the kerosene may be used for the production of propylene and ethylene derivatives, or it may be treated according to Specification 374,510 for the production of additional ethyl alcohol. Specifications 106,080, 248,375, and 273,781, [all in Class 2 (iii), Dyes &c.], also are referred to. According to the Provisional Specification the initial gases may be subjected to a preliminary washing with ammoniacal cuprous formate, acetate, carbonate, or the like in order to concentrate the olefines. Cracking still gases may first be purified from sulphur at atmospheric pressure, for example, by means of an alkaline solution or suspension of ferric oxide or hydroxide, and preferably also from acetylene by washing with water. The gas is then compressed to 20 atmospheres and washed with ammoniacal copper formate. The gas obtained from the used formate on release of pressure and heating to about 65 DEG C. is compressed to about 60 atmospheres, and then washed with kerosene.