Enhanced production of jet fuel precursors via furfural/cyclopentanone aldol condensation by synergistic pairing TiO2 with nano-ZSM-5 zeolite

Aldol condensation of biomass-derived compounds offers a sustainable route to jet fuel precursors. This study explores catalysts based on nanocrystalline ZSM-5 zeolite (n-ZSM-5) modified with various metals (Ca, Mg, Sn, Ti, Zr) for the aldol condensation of furfural (FFL) and cyclopentanone (CPO). While both reactants can enter the ZSM-5 micropores, the resulting C10 (FC) and C15 (F₂C) adducts are too large to be formed within or to exit the microporosity, being instead produced over the external acid sites. Metal modification significantly impacts catalytic activity: Ca and Mg reduce conversion, Sn is neutral, whereas Zr and Ti leads to enhanced performance. The TiO₂/n-ZSM-5 catalyst shows by far the best behavior, doubling FFL conversion and sharply increasing the FC + F₂C yield, which is attributed to a synergistic effect arising from the generation of accessible weak Lewis acid sites by highly dispersed TiO₂ that complement the external Brønsted acidity of ZSM-5.