Gas condensate upgrade over hierarchical ZSM-5 zeolite synthesised via desilication and reassembly routes

This study investigates the influence of structural and acidic properties of ZSM-5 catalysts, specifically parent, desilicated, and cetyltrimethylammonium bromide (CTAB)-reassembled variants, on the catalytic cracking of Ogunu field gas condensate (containing 48.4% paraffins, 32.1% naphthenes, 9% aromatics, 5.7% isoparaffin, and 4.8% alkenes), toward enhancing gasoline-range products. The parent ZSM-5 zeolite was desilicated with 0.3 M NaOH and then reassembled at varying CTAB concentrations (0.01–0.17 M) to obtain samples with tailored pore architecture and acidity. Catalytic tests conducted in a fixed-bed reactor revealed a strong correlation between acidity, porosity, and product yields. Parent ZSM-5 with high Brønsted acidity (0.304 mmol/g) and microporosity (0.15 cm 3 /g), yielded 12.9% aromatics and 11.8% isoparaffins. Desilicated ZSM-5 exhibited reduced microporosity and Brønsted acidity, but larger mesopores (10 nm), resulting in an increased aromatics yield of 19.8%. Reassembled samples with moderate CTAB concentrations of 0.05 M and 0.09 M achieved the highest aromatics yields (27.6% and 28.9%, respectively) and isoparaffin yields (13.3 and 14.3%, respectively), due to balanced acidity and mesoporosity. Samples reassembled with higher CTAB concentrations (≥0.13 M) exhibited acidity collapse and poor aromatics yields (<9%), indicating a loss of catalytic activity. The results confirm that zeolite-treated samples with CTAB concentrations of 0.05 and 0.09 M, optimised for mesoporosity and the Brønsted/Lewis acid ratio, significantly enhance the formation of aromatics and isoparaffins, which are key components for high-octane gasoline blending. This positions hierarchical ZSM-5 as a superior catalyst for upgrading gas condensates into value-added gasoline-range fuels.