Zr-modified USY zeolite as an efficient catalyst for the production of bio-jet fuel precursors from levulinic acid and furfural in the absence of solvent

The high potential of using levulinic acid and furfural as platform molecules for the production of oxygenated adducts suitable as precursors for SAF synthesis is studied through the aldol condensation of both molecules. The research is the first-time demonstration of solventless acid-catalysed levulinic acid/furfural aldol condensation. The catalytic performance of a commercial H-USY zeolite and two post-synthetic variations thereof, with different dealumination degree and Zr loading, is analyzed, aiming at tuning the acid catalytic properties. The catalyst with an almost complete Al removal accompanied by the highest Zr wt% (Zr-USY-2) gave the best results in terms of selective conversion of furfural, pointing out to the Lewis acid sites as the main active sites to promote the aldol condensation reaction. An experimental design allowed to identify the optimal LA/FAL molar ratio (9/1) and reaction temperature (140 °C), while catalyst loading presented a minor significance. The optimization of the reaction parameters allowed to achieve a maximum furfural conversion of 88 %, combined with a yield towards the desired C10 adducts of 55 %. Furthermore, despite the catalytic performance of this material is slightly impaired in consecutive reaction cycles, it can be recovered with a thermal regeneration step, indicating a good reusability. • The aldol condensation of LA and FAL can be performed in a solvent-free environment. • Zeolite with the highest Zr content improves the production of C10 adducts. • Lewis acid sites are the main active sites to promote aldol condensation reaction. • The LA/FAL molar ratio and temperature are the most significant variables. • The catalytic activity of Zr-USY can be recovered with a thermal regeneration step.