GB889297A - Improvements in and relating to the separation of a gaseous mixture of hydrocarbons into components - Google Patents

Abstract

Ethylene is separated from a mixture thereof with higher hydrocarbons, e.g. as obtained by the pyrolysis of hydrocarbons and containing, for example, 10-20% of ethylene by compressing to liquefy the normally liquid hydrocarbons, contacting the remaining gas with a hydrocarbon oil washing liquid boiling below 200 DEG C. to dissolve out hydrocarbons of 3 or more carbon atoms and dissolving ethylene from the residual gas with a solution containing a salt of monovalent copper. The condensation by compression may be regulated to condense C4 hydrocarbons also, conditions at this stage preferably being 10-50 atmospheres gauge and 15 DEG -50 DEG C. The washing oil used in the second stage preferably boils in the range 75 DEG -200 DEG C. and may be a fraction of liquid hydrocarbons obtained in the pyrolysis, e.g. the product from the first stage of the separation; hexane, heptane, octane, decane, undecane (each being normal or branched chain); benzene, toluene, xylene, ethylbenzene, cymene, cumene, diisopropyl benzene, pseudocumene, or mesitylene. The dissolved hydrocarbons may be recovered by reducing the pressure and this is preferably done in stages, the product from the first pressure reduction containing some ethylene being recycled to join the feed to the separation process first (compression) stage. The cuprous salt solution used in the final stage may be acid, neutral or basic and may contain hydrochloric acid, ammonia or organic nitrogen bases such as piperidine, pyridine, ethylene diamine or monoethanolamine. Conditions of 0 DEG -30 DEG C. and 10-25 atmospheres gauge may be used. The ethylene is recovered by lowering the pressure and/or raising the temperature, e.g. under conditions of 0,1-2 atmospheres (absolute) and 30 DEG -70 DEG C. Sulphur compounds should preferably be removed before the third stage, e.g. by washing with ethanolamine or caustic soda and acetylenes are preferably removed by selective hydrogenation. Specification 855,133 is referred to.ALSO:Ethylene is separated from a mixture thereof with higher hydrocarbons, e.g. as obtained by the pyrolysis of hydrocarbons and containing, for example, 10%-20% of ethylene, by compressing to liquefy the normally liquid hydrocarbons, contacting the remaining gas with a hydrocarbon oil washing liquid boiling below 200 DEG C. to dissolve out hydrocarbons of 3 or more carbon atoms and dissolving ethylene from the residual gas with a solution containing a salt of monovalent copper. The condensation by compression may be regulated to condense C4 hydrocarbons also, conditions at this stage preferably being 10-50 atmospheres gauge and 15 DEG C.-50 DEG C. The washing oil used in the second stage preferably boils in the range 75 DEG C.-200 DEG C. and may be a fraction of the liquid hydrocarbons obtained in the pyrolysis, e.g. the p product from the first stage of the separation; hexane, heptane, octane, decane, undecane (each being normal or branched chain); benzene, toluene, xylene, ethylbenzene, cymene, cumene, di-isopropyl benzene, pseudo-cumene, or mesitylene. The dissolved hydrocarbons may be recovered by reducing the pressure and this is preferably done in stages, the product from the first pressure reduction containing some ethylene being recycled to join the feed to the separation process first (compression) stage. The cuprous salt solution used in the final stage may be acid, neutral or basic and may contain hydrochloric acid ammonia or organic nitrogen bases such as piperidine pyridine, ethylene diamine or monoethanolamine. Conditions of 0 DEG C-30 DEG C. and 10-25 atmospheres gauge may be used. The ethylene is recovered by lowering the pressure and/or raising the temperature, e.g. under conditions of 0.1-2 atmospheres (absolute) and 30 DEG C.-70 DEG C. Sulphur compounds should preferably be removed before the third stage e.g. by washing with ethanolamine or caustic soda and acetylenes are preferably removed by selective hydrogenation. Specification 855,133 is referred to.