Rational design of bifunctional hierarchical Pd/SAPO-5 for the synthesis of tetrahydrofuran derivatives from furfural

The one-pot aldol condensation/crotonization reaction between furfural and methyl isobutyl ketone (MIBK), followed by hydrogenation with molecular H₂, was implemented for preparing tetrahydrofuran derivatives. To this aim, we developed a robust Pd/HPSAPO-5 catalyst based on the crystalline silico-aluminophosphate SAPO-5 with hierarchical porosity and optimized silicon content. The hierarchical HPSAPO-5 catalyst was synthesized using a bottom-up method starting from pre-synthesized MCM-41, with the surfactant (CTAB) inside the mesopores, serving both as Si source and mesoporogen. NH₃-TPD and FT-IR spectroscopy of adsorbed probe molecules combined with solid-state ¹H MAS NMR were used to assess the nature, strength and accessibility of the acid sites. The structural and textural properties of the catalysts were investigated using X-ray diffraction (XRD) and N₂ adsorption. HR-TEM was used to assess the dispersion and location of Pd nanoparticles on HPSAPO-5. The spent catalyst could be restored and reused after calcination.