Aromatization of propene and n-butene over H-galloaluminosilicate (ZSM-5 type) zeolite

Abstract

Aromatization of propene and n-butene (at 400°C and atmospheric pressure) over H-GaAlMFI zeolite (bulk Si/Al=37.5, bulk Si/Ga=24.3, framework (FW) Si/Al=40.3, FW Si/Ga=49.9, non-FW Ga=0.32 mmol g^-1, crystal size=5.5±1.5 μm) having high acidity (pyridine chemisorbed at 400 °C=0.46 mmol g^-1) has been investigated at different space velocities (3100-58,100 cm³ g^-1 h^-1). The catalyst was found to have a high olefin aromatization activity and high aromatics selectivity, these are attributed to the presence of a large number of both non-framework Ga-species and protonic acid sites. The product selectivity and distribution were strongly influenced by the space velocity. The distributions of aromatics and xylene isomers are found to be similar for the aromatization of both propene and n-butene, but that of aliphatic hydrocarbons differed in the two cases. The propene and n-butene aromatization reactions involve both the protonic acid sites mediated hydride transfer reactions and the direct dehydrogenation reactions over non-framework Ga-species, probably in combination with the zeolitic protons. A reaction path for the propene/n-butene aromatization is proposed.