Selective shale oil upgrading to aviation kerosene- and diesel-range hydrocarbons: A tandem catalytic route over oil shale ash-derived nanocrystal-stacked Na-ZSM-5

Selective upgrading of shale oil requires removal of unstable alkenes and oxygenates while preserving valuable fuel-range alkanes. Here, nanocrystal-stacked Na-ZSM-5 zeolites derived from oil shale ash were evaluated for ex-situ tandem upgrading of shale-oil vapors. Density functional theory calculations showed that alkene protonation is kinetically more favorable than alkane protonation and supported a possible role of Na + -associated Lewis sites in polarizing unsaturated intermediates. SAZ-30 combined a higher Brønsted-acid density with greater textural accessibility, whereas SAZ-60 contained a larger fraction of strong Lewis acid sites and showed a stronger tendency toward fragmentation and chain-length redistribution. Under the present GC–MS conditions, alkenes and oxygenates were not detected after SAZ catalysis, while n-alkanes accounted for 77.6–85.3 area% of the detected products. The SAZ-60 → SAZ-30 sequence achieved a summed aviation kerosene range and diesel range selectivity of 88.6%, whereas the reverse sequence afforded isomerization efficiencies of 17.3% and 17.2%. Cyclic tests showed performance losses below 5%. This work demonstrates a synergistic approach for oil shale ash valorization and selective production of high-value fuel components.