Abstract
The increasing global demand for sustainable aviation fuel (SAF) and the urgent need to reduce greenhouse gas emissions have intensified efforts to develop renewable, carbon-neutral pathways for liquid hydrocarbon production. Lignocellulosic biomass offers a widely available and sustainable carbon resource; however, its recalcitrant structure, high oxygen content, and heterogeneous polymeric composition present significant challenges for catalytic upgrading.  Existing catalytic routes often suffer from high capital intensity, low carbon recovery, and poor selectivity toward jet-fuel-range hydrocarbons.  This work addresses these limitations through the development of efficient, and recyclable zeolite-based catalytic systems capable of converting raw biomass and biomass-derived intermediates into long-chain hydrocarbons. A critical review on the zeolite-based catalysis highlights the structural and functional constraints of conventional zeolites in processing bulky oxygenates and the advantages of hierarchical zeolite frameworks with enhanced mesoporosity and tailored acidity. Guided by these insights, the first set of investigations aimed to investigate the direct conversion of woody biomass using nickel-loaded zeolites. Among the catalysts evaluated, 10 wt% Ni/H-β showed the highest catalytic activity, achieving a 15.6 wt% carbon yield with high selectivity toward C7-C15 cycloalkanes (7.8 wt%) at 270 °C and 3 MPa H2.

To overcome the low carbon-number of C5-C9 lignocellulosic biomass intermediates, hydroxyalkylation–alkylation (HAA) of 2-methylfuran and furfural was explored.  Hierarchical H-Y made by the surfactant-templating technique demonstrated superior activity, which led to 72 mol% yield in the C15 jet-fuel precursor at 80 °C for 300 min of residence time. The good catalytic performance was attributed to the zeolite's strong Brønsted acidity and enhanced textural properties. Kinetic studies revealed second-order behavior, while catalyst deactivation studies identified coke formation and water-induced structural degradation during catalyst calcination as the main factors contributing to the catalyst deactivation.  The improved textural and acidic properties of hierarchically structured H-Y zeolite, together with an enhanced synthesis that stabilizes framework Al against water formed during HDO reactions, make it a promising catalyst support for impregnating metals such as Pt, Pd, Ru, or Ni, required to produce long-chain hydrocarbons from HDO of woody biomass.