GB1243959A - Method of extracting diolefins - Google Patents

Abstract

1,243,959. Extracting diolefins. INSTITUT FRANCAIS DU PETROLE DES CARBURANTE ET LUBRIFIANTS.- 3 March, 1970 [3 March, 1969], No. 10046/70. Heading C5E. A method of extraction in liquid phase to isolate butadiene and/or isoprene from a mixture of hydrocarbons having 4 and/or 5 carbon atoms, of various degrees of saturation, comprising the introduction of said feedstock into a counter-current extraction zone, at at least one intermediate point of said zone, the introduction of a polar extraction solvent with the addition of from 0 to 20% of its weight of water, at a first end of said zone in extractive contact with said feedstock, the introduction of an apolar auxiliary solvent incapable of dissolving a substantial amount of extractive solvent, being of a density lower than said solvent, and having a boiling point higher than that of the mixture of hydrocarbons to be separated, promoting reflux, at the other end of said extraction zone, so as to form a first extract phase containing a greater amount of the dienic hydrocarbon or hydrocarbons and a first refined phase containing a reduced amount of dienic hydrocarbons, bringing into countercurrent contact in a second extraction zone, the first extract phase with the auxiliary solvent which is capable of dissolving the dienic hydrocarbon or hydrocarbons and incapable of dissolving a substantial amount of the extraction solvent, so as to form a second extract phase containing an increased amount of dienic hydrocarbon or hydrocarbons and a second refined phase containing a reduced amount of dienic hydrocarbons and an increased amount of extraction solvent, the separation by distillation of the dienic hydrocarbon or hydrocarbons and the auxiliary solvent present in the second extract phase, the recycling of the recuperated auxiliary solvent to one or both of the two extraction zones and the recycling of the second refined phase to the first extraction zone as first extraction solvent. The polar extraction solvent may be N-methylpyrrolidone, butyrolactone, DMF, acetonitrile, dimethyl acetamide, furfurol, nitromethane, diethyl sulphoxide or, preferably, dimethylsulphoxide. The apolar auxiliary solvent may be a C 5 -C 10 paraffin or cycloparaffin or mixture thereof, preferably cyclohexane.