S1-supported Pd@CeO2quasi-core@shell materials as advanced catalysts for selective hydrogenation of furfural

Abstract

Bare Pd metal nanoparticles invariably suffer from poor selectivity in furfural hydrogenation by forming flat configurations, with the aromatic ring of the substrate molecules parallel to the metal surface. Herein, we put forward a promising solution by using CeO2 as promoters to modify Pd nanoparticles for modulating the adsorption behaviors of furfural molecules. To achieve the highly-desired ultra-small Pd@CeO2 core@shell nanostructure, a “constrained auto-redox” synthesis is developed, in which silicalite-1 supports play the key role of providing their surface as the landing place of PdOx precursors for inhibiting the overgrowth and the deformation. To the best of our knowledge, this is one of the smallest core@shell materials obtained from aqueous synthesis. When evaluated as catalysts, Pd@CeO2/S-1 gives 98.9% conversion of furfural with 94.3% selectivity for furfural alcohol in 15 h, which is much better than that of Pd/S-1 (88.6% conversion with 44.3% selectively). The DFT simulation reveals a strong interaction between the defects of CeO2 and the oxygen atom of the –CHO group in furfural molecules, which benefits the selective hydrogenation occurred in the –CHO group rather than the furan ring.