RETAINED PRODUCTS FROM THE REACTION OF BENZENE AND TOLUENE OVER H-ZSM5 ZEOLITE

Benzene or toluene react on H-ZSM5 zeolite in the absence of added oxygen at 593 K and 673 K to give retained residue which contains some anthracenes/(phenanthrenes) accompanied by biphenyls, diphenylmethanes, fiuorenes, alkanes/(olefins), alkylbenzenes, alkylnaphthalenes, and (at 673 K) some black insoluble carbonaceous polymer; it is inferred that the condensation reactions which have been identified as leading to fused-ring tricyclic aromatics form part of the pathway to this carbonaceous polymer. The retained aromatic components mostly carry methyl substituents. It is concluded that anthracenes/(phenanthrenes) are formed from benzene or toluene via biphenyls (the primary condensation product) and diphenylmethanes, the presence of methyl (or other alkyl) substituents being a necessary feature. This reaction may be a general one for the enlargement of fused, polycyclic, aromatic systems. In the presence of oxygen, the retained hydrocarbon products are generally similar to those formed without added oxygen, although aromatic oxygenates are coproduced. Reaction pathways are discussed. © 1991.