Chemical process

A process for the separation of lower-boiling hydrocarbons (i.e. C4 hydrocarbons and under which boil below 30 DEG C.) from a mixture containing isoprene, lower boiling hydrocarbons and water comprises adding an organic compound boiling in the range of from 5 DEG to 30 DEG C. and at a higher temperature than the lower-boiling hydrocarbons to said mixture and separating lower-boiling hydrocarbons from the resulting mixture by distillation. Specified organic compounds are acetaldehyde, neopentane, ethylamine, dimethylamine, ethylchloride, trichloromonofluoro-methane, dichloro-monofluoromethane, 2-chloropropylene, cyclobutane, methyl cyclopropane, dimethylcyclopropane, methyl ethyl ether and methyl mercaptan. In a preferred embodiment, a vapour stream obtained by quenching the effluent of a cracking unit containing isoprene, water vapour and methane, ethane, propylene and butane is passed through line 10 into distillation column 11. Acetaldehyde is added through line 12 and the downwardly flowing compound contacts the upwardly flowing lower boiling hydrocarbons in the packed zone 13. The overhead passes through line 14 into condenser 15 and thence through a line 16 to a separator 17. Uncondensed gases pass through a line 19. Water and crude isoprene pass downwardly through a packed zone 20 and are passed through line 21 into decanter 25 from which the hydrocarbon is withdrawn as crude product through line 27 and the aqueous phase is discharged through line 26. Heating is effected by steam through a coil 29.