Controlled One-pot Synthesis of PdAg Nanoparticles and Their Application in the Semi-hydrogenation of Acetylene in Ethylene-rich Mixtures

In the present paper, we report the synthesis of highly functionalized nanomaterials carefully nanoengineered to catalyze the semi-hydrogenation of acetylene in ethylene-rich mixtures. Surface functionalization and structure modification of a series of bimetallic PdAg nanoparticles was performed using HHDMA as stabilizer and alloying the active palladium phase with silver. Bimetallic PdAg NPs with adjustable Pd/Ag ratio were prepared in water through a novel one-pot methodology using hydrogen gas as a benign reducing agent and cyanide as additive. UV-Vis studies indicated the formation of the bimetallic nanostructures through a sequential displacement-galvanic reduction process mediated by cyanide. The series of colloidal NPs were deposited onto alumina and successfully applied as catalysts in the selective hydrogenation of acetylene in ethylene rich mixtures. Geometric and electronic promotion of Ag over Pd based catalysts was evidenced by the increase of the ethylene selectivity with the Ag content. The reactivity of these materials demonstrated the applicability of HHDMA stabilized NPs in a gas phase reaction of industrial interest and the success of combining several strategies for the enhancement of the alkene selectivity.