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Naphthenes transformation over H-[Al]-ZSM-5 and Ga/[Al]-ZSM-5 catalysts

Abstract:

The transformations of propane, n-hexane, cyclohexane, n-neptane and methylcyclohexane were studied over acidic H[Al]-ZMS-5 and bifunctional Ga/[Al]-ZSM 5 catalysts at 530°C. 1 bar and with a N2/hydrocarbon molar ratio of 4. Results show that the aromatic molar product distribution (AMPD) is affected by the type of catalyst. On H-[Al]-ZSM-5 catalyst, propane, n-hexane and cyclohexane (as one group), and n-heptane and methylcyclohexane (as another group), show very similar AMPD. Over Ga/[Al]-ZSM-5 the AMPD for propane is almost the same as over H-[Al]-ZSM-5. However, for liquid hydrocarbons, the fraction of the aromatic isomer of the transformed molecule is higher than with acidic catalysts. This change is more pronunciated for cycloparaffins, and it is related to the dehydrogenating activity of gallium species, which catalyze the direct aromatization of hydrocarbons rather than initial cracking and subsequent aromatization.