Producing a high-quality synthetic steamcracker feedstock from different aromatic model components of pyrolysis gasoline on bifunctional zeolite catalysts

Aromatics with 6-9 carbon atoms, i.e., model components of pyrolysis gasoline, are hydroconverted on bifunctional Pd/H-ZSM-5 zeolites into a high-quality synthetic steamcracker feedstock (consisting mainly of ethane, propane and n-butane). The yield of these desired n-alkanes with two or more carbon atoms depends strongly on the nature of the aromatic feed: at 400 C and 6 MPa in an excess of hydrogen, a yield of 72.8% is observed with toluene, but yields higher than 90% can be achieved with benzene or ethylbenzene as feed. These pronounced differences are rationalized in terms of varying types of classical beta-scission and different contributions of non-classical Haag-Dessau cracking. (C) 2002 Elsevier Science B.V. All rights reserved.