FIELD: industrial organic synthesis. SUBSTANCE: polynuclear aromatic byproducts are isolated and removed from vapor stream coming out of reaction zone of hydrocarbon (commonly gaseous) dehydrogenation process by mixing above-mentioned vapor stream with loop recycling stream containing mononuclear aromatic compounds and bringing resulting mixture into contact with adsorbent to reduce concentration of mononuclear compounds and to form stream containing dehydrogenated hydrocarbons and dehydrogenable hydrocarbons. Spent adsorbent removed from adsorption stage and containing mononuclear aromatics is regenerated by being brought into contact with hot hydrogen-rich gas to remove at least part mononuclear and polynuclear aromatics. Hydrocarbon stream leaving regeneration zone is then separated into two streams one containing mononuclear compounds and the second polynuclear compounds. At least part of the former is recycled to mixing stage. EFFECT: increased purity of hydrocarbon dehydrogenation product. 6 cl, 1 dwg
