~'g~rnoll S0045-6535(96)00041-0 Chenu~sphere, Vol. 32, No. 7, pp. 1301-1305, 1996 Copyright © 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0045-6535/96 $15.00+0.00 FLUORANTHENE FORMATION OVER ZEOLITES Giorgio Perez* and Mariarosa Raimondo Istituto di Cromatografia del CNR. c.p. 10. 00016 Monterotondo Stazione (RM) Italy (Received in Germany 8 December 1995; accepted 23 January 1996) ABSTRACT Gaseous 1-phenylnaphthalene was allowed to react with two H+ZSM-5 zeolites distinguished by a different acidity. The isomerisation to 2-phenylnaphthalene was the principal reaction observed, but also fragmentation to benzene plus naphthalene and self-condensation to fluoranthene occurred. The yields of all the products were higher when the more acidic zeolite was used. A temperature dependence study showed that, varying the temperature from 390 to 450°C, the yield of fluoranthene increased. By the Arrhenius plots for fluoranthene formation it was concluded that the activation energy of this reaction is independent on the acidity ofzeolites. Copyright © 1996 Elsevier Science Ltd INTRODUCTION The family of polycyclic aromatic hydrocarbons is ubiquitously present in the environment. Their formation is generally ascribed to incomplete combustion processes. As suggested by Badger 1 many years ago, C-H bonds are cleaved and the intermediates formed undergo cyclisation processes through a radicalic mechanism. However, some years later report 2 concerning the chemistry of flames showed that also ionic species are formed. As a consequence, it was very tempting to demonstrate the existence of an ionic pathway to polycyclic aromatic hydrocarbon. Therefore, we investigated the reactions between phenylium ions and biphenyl 3 and between naphthyl ions and benzene 4 which led to the formation of triphenylene and fluoranthene, respectively, using i3-decay techniques. Furthermore, by the radiolytic technique introduced by Ausloos 5, the gas phase protonations of o-terphenyl 6, l-phenylnaphthalene 7, and 9-phenylanthracene 8 were studied and self- condensation reactions, leading to the formation of the correspondent self-condensation products were observed. The protonating agents, used in the cited investigations, were strong Bronsted acids, which led to the formation of excited protonated intermediates, which, if not stabilised by collision, could underwent either fragmentation, isomerisation, or self-condensation reactions. 1301