Shifting reaction path for levulinic acid aqueous-phase hydrogenation by Pt-TiO2 metal-support interaction

Levulinic acid (LA) aqueous-phase hydrogenation into gamma-valerolactone (GVL) is considered one of the pivotal reactions to convert biomass into renewable chemicals. Here we have deposited Pt on TiO2 nanofilm coated alpha-Al2O3 via atomic layer deposition (ALD) to synthesize Pt-TiO2/alpha-Al2O3. This catalyst shows excellent activity and stability (1000 h) in LA hydrogenation compared to Pt/alpha-Al2O3. By excluding the effect of Pt particle size, lattice plane, support morphology, pore structure, and electronic state, the critical role of Pt-TiO2 interaction is revealed by various characterization methods. CO diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in-situ Fourier transform Infrared spectra (FTIR) results indicate that Pt-TiO2 interaction provides new interfacial Pt sites for LA and intermediate adsorption and Ti-OH active sites for LA dehydration cyclization to alpha-angelica lactone intermediate, which leads to the shift of reaction pathways from direct LA C=O hydrogenation lactonization on Pt/alpha-Al2O3 to LA dehydration cyclization and hydrogenation on Pt-TiO2/alpha-Al2O3.It provides insight into the design of high-efficient catalysts for aqueous-phase hydrogenation.