Light Paraffinic Naphtha to BTX Aromatics over Metal-Modified Pt/ZSM-5

We investigated the conversion of light paraffinic naphtha (C5-C6) into BTX (benzene, toluene, and xylenes) aromatics using 1.0 wt % Pt-M/ZSM-5 (modifier M=1 wt% Zn, 2 wt % of Fe, La, Ga) prepared using wet-impregnation method. The effects of Pt and modifier on light naphtha conversion, yield and aromatic selectivity (benzene, toluene, xylene, C9+ aromatics) were studied in fixed-bed flow reactor in atmospheric pressure, at 550 °C, and WHSV 1.0 h⁻¹. Catalytic efficiency of modified Pt or Pt-M ZSM-5 catalysts has been equated to conventional ZSM-5 [Si/Al₂=30] catalyst. While the yield of total aromatics was slightly increased over Pt/ZSM-5 comparison to parent ZSM-5 from 32 wt % to 37 wt %, the value for in situ formed mesoporous Pt-Ga/ZSM-5 was significantly improved reaching 60 wt %. The higher selectivity to aromatics is attributed to the induced mesoporous volumes and dehydrogenation activity of Ga species. These species associated with Pt were effective in the conversion of light naphtha to olefins, which later converted into aromatics by secondary reactions: cracking, isomerization and dimerization. The Pt-Ga/ZSM-5 showed good stability toward the selective production of aromatics at a low toluene/benzene ratio ∼0.5 due to Pt component.