Process for the removal of polynuclear aromatic compounds from a vapor effluent from a normally gaseous hydrocarbon dehydrogenation reaction zone

A process for the removal of trace quantities of polynuclear aromatic compounds from the vapor effluent of a hydrocarbon dehydrogenation zone comprising normally gaseous olefinic hydrocarbons, trace mononuclear aromatic compounds and trace polynuclear aromatic compounds which process comprises:

• (a) cooling substantially all of said vapor effluent to condense at least a portion thereof up to about 5 weight percent;
• (b) introducing the resulting cooled stream from step (a) into a vapor-liquid separator to produce a vapor stream comprising normally gaseous olefinic hydrocarbons and having a reduced concentration of polynuclear aromatic compounds and a liquid stream comprising mononuclear and polynuclear aromatic compounds;
• (c) separating said liquid stream comprising mononuclear and polynuclear aromatic compounds recovered in step (b) in a separation zone to produce a stream rich in mononuclear aromatic compounds;
• and
• (d) recovering said vapor stream comprising normally gaseous olefinic hydrocarbons having a reduced concentration of polynuclear aromatic compounds.