Production of aromatics from heavier n-paraffins on hybrid cracking-reforming catalyst

Selective production of aromatics from the heavier n-paraffins was studied on nano-structured (ns) catalysts consisting of ns alumina and MFI-type H-galloaluminosilicate (H-GaAlMFI) zeolite. Performance of the hybrid H-GaAlMFI zeolite catalyst with ns Al2O3 was improved considerably from those of the zeolite sole catalyst and USY or H-ZSM-5 catalyst. It was observed that in the n-C16H34 conversion, the product selectivity for aromatics (including intermediate olefins and byproducts) and the degradation rate depended on either the ratios of Ga/(Ga + Al) and Si/(Ga + Al) in the zeolite component or on the co-existence of ns Al2O3. It was found that aromatics could be produced selectively by controlling the reaction time. In regards to the catalytic active sites, the ns species at the zeolite surface layer and the surface distributions were confirmed by X-ray photoelectron spectroscopy with the Ar-etching method. It was determined that non-framework Ga species existed as Ga oxides after calcining. It was also revealed that the ns alumina had an important role in forming the ns species of non-framework Ga by extracting it from the zeolite framework and stabilizing it as an ns oxide at the zeolite particle surface which opened into the nano-space.

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► H-GaAlMFI zeolite is effective to aromatic production from heavier n-paraffins.
► The zeolite is promoted by hybridization with nano-structured alumina.
► Ga of the zeolite is extracted near the surface from the framework by calcination.
► The Ga extraction is promoted by nano-structured alumina to be stabilized.
► The highly dispersed Ga protected by the alumina is active, selective and stable.