Regulation of Strong Metal-Support Interaction by Alkaline Earth Metal Salts.

Classical strong metal-support interaction (SMSI) is of significant importance to heterogeneous catalysis, where electronic promotion and encapsulation of noble metal by reducible support are two main intrinsic properties of SMSI. However, the excessive encapsulation will inevitably hamper the contact between active sites and reactant, leading to reduced activity in catalysis. Herein, alkaline earth metal salts are employed to depress the encapsulation of Ru nanoparticles in Ru/TiO catalyst in the present study. Thermodynamic calculation, transmission electron microscopy (TEM) and chemisorption results show that the alkaline earth metal salts could successfully prevent the migration of TiO overlayer to Ru nanoparticles in Ru/TiO catalyst via in situ formation of titanates, resulting in high exposure of active metal. Meanwhile, X-ray photoelectron spectroscopy (XPS) and hydrogen temperature-programmed reduction (H -TPR) results reveal that an even stronger electron donation from the reduced support to Ru nanoparticles is achieved. As a result, the alkaline earth metal salts-doped Ru/TiO catalysts exhibit superior activity in catalytic hydrogenation of aromatics, which is in contrast to the pristine Ru/TiO catalyst that shows negligible activity under the same conditions due to the excess encapsulation of Ru nanoparticles in Ru/TiO catalyst.