Influence of temperature on the product selectivity and distribution of aromatics and C8 aromatic isomers in the conversion of dilute ethene over H-galloaluminosilicate (ZSM-5 type) zeolite

Product selectivity and distribution of the total and C-8 aromatics at the different isoconversions (40, 60, and 80%) of dilute ethene (5 mol% C2H4 in N-2) over the H-GaAlMFI zeolite catalyst at different temperatures (300-500degreesC) have been investigated. A strong temperature dependence of the selectivity for aromatics, propene, and C-4 hydrocarbons and also of the distribution of aromatics and C-8-aromatic isomers has been observed. At lower temperatures (below 400degreesC) the aromatization involved mainly hydride transfer reactions, but at higher temperatures (greater than or equal to400degreesC) it involved mainly dehydrogenation reactions. The distribution of xylene isomers is controlled by steric factors at 300degreesC but kinetically at 500degreesC. (C) 2002 Elsevier Science.