Palladium supported over carbon nanotubes catalytic system for green diesel production

Addressing the urgent need for sustainable biofuels, for the first time in the literature a palladium catalyst supported on multi-walled carbon nanotubes (Pd@MWCNTs) was used for promoting deoxygenation (DO) of fatty acids and triglycerides to produce green diesel. Reaction was conducted in water as a green solvent under relatively mild conditions (250°C, 16 bar H2). The catalyst was prepared modifying known procedures, using oxidative pretreatment of nanotubes, and characterized by FTIR, SEM-EDX, BET, NH3-TPD, XPS, physi- and chemisorption techniques. Catalytic performances of Pd@MWCNTs were compared with those of commercial Pd/C and different reactivity was explained on the base of chemical and morphologic features. Pd@MWCNTs gave a complete conversion (100%) of soybean oil under the operative conditions and proved to be always more selective (>90%) than Pd/C in giving decarbonylation products (alkanes C15 and C17). The catalyst resilience was evident in aqueous-phase reactions, where it maintained 86% conversion upon reuse, while Pd/C deactivated rapidly. Finally, industrial relevance was demonstrated extending the protocol to unrefined feedstocks such as olein residues and sewage scum, achieving 50–95% alkane yields.