Influence of space velocity on product selectivity and distribution of aromatics in propane aromatization over H-GaAlMFI zeolite

Abstract

Aromatization of propane has been investigated over H-GaAlMFI zeolite at different space velocities (1500-49,000 cm³/g/h) in the temperature range of 450-600 ° C. The product selectivity and aromatic distribution was profoundly influenced by the space velocity. The aromatization/cracking ratio was found to pass through a maximum in the space velocity range of 5000-12,000 cm³/g/h at all the investigated temperatures. Selectivity for toluene increased, while that for benzene decreased with increasing aromatic yields (decreasing space velocity). Selectivity for C₈ and C₉ aromatic compounds passed through a maximum with increasing aromatic yields. The p-xylene selectivity decreased with increasing aromatic yields, while that for m-xylene increased. The following reaction pathway for the propane aromatization reaction over H-GaAlMFI has been proposed based on the observed product distribution. Propylene is the primary (intermediate) product of the propane aromatization reaction. Ethene is formed by the primary cracking of propane as well as from cracking of higher olefins. Benzene, p-xylene, and ethyl benzene are primary aromatic products, while m-xylene, o-xylene and C₉ compounds are formed via secondary transformations. Toluene is formed as a primary aromatic product and from secondary transformations.