(558w) Using Atomic Layer Deposition to Design Catalysts for Enhanced Pairwise Selectivity of Parahydrogen Addition to Unsaturated Hydrocarbons

Parahydrogen-induced polarization (PHIP) is a powerful method to increase signal intensities in proton NMR (nuclear magnetic resonance) measurements. However, a requirement for PHIP NMR signals is that the two hydrogen atoms in one parahydrogen molecule are added across an unsaturated bond. In a typical supported noble metal catalysts the fraction of hydrogen molecules that are added in a pairwise fashion is extremely small due to dissociative hydrogen chemisorption and rapid hydrogen diffusion on the noble metal particle. To reduce the rapid diffusion of hydrogen on the metal particles, we have used atomic layer deposition to synthesize catalysts with ultra-low noble metal loadings on different oxide supports. At these low loadings, on the order of 10-100 ppm of Pt, we have shown that the Pt is atomically dispersed and that the PHIP NMR signals are significantly enhanced compared with supported catalysts with higher Pt loadings.