Impact of zeolite properties on catalytic hydrodeoxygenation: Spatially segregated metal-acid site engineering for enhanced cascade efficiency

To reduce the environmental impact of hydrodeoxygenation (HDO) while enhancing process economics, it is crucial to develop advanced catalytic materials that enable HDO under milder conditions, suppress decarboxylation/decarbonylation (DCOx), and eliminate auxiliaries, all while maximising target product yield. Spatial segregation of metal and acid sites has emerged as an effective strategy for improving HDO efficiency in fatty acid conversion. This study explores the influence of zeolitic carrier porosity and acidity on HDO, employing Pd nanoparticles as the metal catalyst and lauric acid as the model substrate. The findings reveal that acidity and mesoporosity are key determinants of substrate conversion, product selectivity, and overall catalytic performance within the same zeolitic framework (MFI ZSM-5). High acidity and hydrophilicity in ZSM-5 zeolites hinder lauric acid conversion by retaining water within the framework, which would adversely affect reaction equilibria in the HDO cascade, whereas mesoporosity in hierarchical ZSM-5, which enhances mass transport, is beneficial for conversion and dodecane formation. For hierarchical ZSM-5, produced via desilication, the less acidic PdNP/HMZSM5-DA25 (25 reflecting the original Si:Al ratio) yields 2.5 times more dodecane than more acidic but less mesoporous PdNP/HMZSM5-DA15 (Si:Al of 15). Expanding this investigation to different zeolitic frameworks (Pd nanoparticles supported on USY, BETA, and ZSM-5) demonstrates that larger micropores further facilitate diffusion and improve catalytic efficiency. PdNP/HUSY-DA exhibits a 32% improvement over PdNP/HMZSM5-DA25, with a dodecane production rate of 6.1 mmol dodecane g catalyst −1 h −1 , ranking it among the most superior state-of-the-art HDO systems at comparable conditions. This study validates the spatial segregation of active sites as a robust strategy for stabilising Pd nanoparticles and improving catalyst durability in cascade HDO processes. Fine-tuning zeolite properties is essential for optimising catalyst design to achieve efficient and sustainable biofuel production via HDO.