Structure and properties of bimetallic colloids formed in polystyrene-block-poly-4-vinylpyridine micelles: catalytic behavior in selective hydrogenation of dehydrolinalool

摘要

Catalytic properties of palladium and bimetallic (PdAu, PdPt, and PdZn) nanoparticles formed in block copolymer micelles derived from polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) were studied in dehydrolinalool (DHL) hydrogenation. FTIR spectroscopy on CO adsorption and XPS show that the second metal (Au, Pt, or Zn) acts as a modifier toward Pd, changing both its electronic structure and its surface geometry. In turn, this change provides higher catalytic activity of bimetallic particles formed in Ps-b-P4VP micelles compared to Pd micelles, which can be ascribed mainly to an increase in the number of active centers on the particle surface. High selectivity of DHL hydrogenation (99.8% at 100% conversion) was achieved for all the Pd and bimetallic micellar catalysts, by chemical modification of the nanoparticle surface with pyridine units. Kinetic study of DHL hydrogenation, along with computational kinetic models, allowed us to describe a hydrogenation mechanism with these catalysts.