02472nas a2200265 4500008004100000022001400041245008800055210006900143260000800212300001600220490000600236520163300242653001701875653001801892653003101910653002501941100001801966700001901984700001802003700002002021700002402041700001602065700001802081856010702099 2019 eng d a2168-048500aMechanistic insights into the pathways of phenol hydrogenation on Pd nanostructures0 aMechanistic insights into the pathways of phenol hydrogenation o cOCT a17126-171360 v73 a

Product selectivity in aqueous phase phenol hydrogenation on well-defined supported Pd nanostructures (spheres, cubes, and octahedra) was studied using defined experiments and density functional theory (DFT) simulations. On Pd spheres and octahedra, the reaction initially showed high selectivity (in the first 3 h, at 363 K and 5 bar H-2 pressure) toward the partially hydrogenated product cyclohexanone. On prolonged operation (>20 h of reaction time), a shift in the product selectivity (up to 100%) toward the completely hydrogenated product cyclohexanol was observed on Pd spheres and octahedra. In contrast, the reaction on Pd cubes, which only had {100} facets, showed a high selectivity (similar to 90%) toward the product cyclohexanone even after 40 h, at the same reaction conditions. Since the {111} facets are expected to be the majority sites on a spherical particle, we attribute the selectivity trend observed on spherical Pd particles to be primarily controlled by the selectivity trend on the Pd{111} facets. This observation was further confirmed on performing the hydrogenation reaction on a mixture of Pd cube and Pd octahedron particles in a ratio of 25:75 (representing the site ratio of a spherical particle). DFT simulations provided a mechanistic insight into the reactivity of the two different facets ({100} and {111}) toward phenol hydrogenation. The calculations revealed that the selectivity significantly depended on the activation barriers involved in cyclohexanone hydrogenation on the Pd{111} facets (77 and 57 kJ/mol) as compared to those on the Pd{100} facets (97 and 101 kJ/mol).

10aCyclohexanol10acyclohexanone10afacet-dependent reactivity10aphenol hydrogenation1 aPorwa, Govind1 aGupta, Shelaka1 aSreedhala, S.1 aElizabeth, Joes1 aIthan, Tuhin, Suvra1 aHaider, Ali1 aVinod, C., P. uhttp://library.ncl.res.in/content/mechanistic-insights-pathways-phenol-hydrogenation-pd-nanostructures01973nas a2200241 4500008004100000245014200041210006900183260000800252300001600260490000600276520110900282653001801391653001801409653002801427653003701455653002501492100001801517700001901535700001701554700001701571700001801588856012501606 2023 eng d00aPd nanoparticles supported on N-incorporated hybrid organosilica as an active and selective low-temperature phenol hydrogenation catalyst0 aPd nanoparticles supported on Nincorporated hybrid organosilica  cJUN a11500-115120 v63 a

A heterogeneous Pd-NPMO hybrid-silicacatalyst is synthesized andits application for aqueous phase selective hydrogenation of phenolto cyclohexanone at near ambient temperature (40 degrees C) and underatmospheric hydrogen pressure is demonstrated. The homogeneously distributedPd nanoparticles on N-bridged hybrid mesoporous organosilica showedremarkable activity and selectivity for cyclohexanone compared tothe unmodified Pd-SBA-15 catalyst. Control experiments strongly claimthe role of nitrogen domains in the organic framework of hybrid silicasupport in stabilizing small Pd nanoparticles and possibly modifyingthe Pd sites responsible for catalysis to activate the substrate moleculesin water. The hybrid silica catalyst was stable and reused severaltimes without any significant drop-in activity, proving the heterogeneityof the bifunctional Pd catalyst. Based on the density functional theorystudy and experimental interventions, a possible reaction mechanismfor the low-temperature phenol hydrogenation explaining the role oforganic domains in the hybrid-silica framework is proposed.

10acyclohexanone10aHybrid silica10apalladium nanoparticles10aPeriodic mesoporous organosilica10aphenol hydrogenation1 aBetsy, K., J.1 aBajpai, Priyam1 aLazar, Anish1 aVanka, Kumar1 aVinod, C., P. uhttp://library.ncl.res.in/content/pd-nanoparticles-supported-n-incorporated-hybrid-organosilica-active-and-selective-low01864nas a2200229 4500008004100000022001400041245008600055210006900141260000900210490000700219520109700226653001701323653002301340653002101363653001601384653002501400100002401425700002401449700002301473700002801496856011001524 2023 eng d a1861-472800aPhenol hydrogenation to cyclohexanol catalysed by palladium supported on CuO/CeO20 aPhenol hydrogenation to cyclohexanol catalysed by palladium supp cJUN 0 v183 a

Hydrogenation of phenol to cyclohexanone/cyclohexanol is an important reaction in production of nylon-6, nylon-66 and in petroleum industry. Liquid phase phenol hydrogenation over Pd-CuO/CeO2 was carried out under mild conditions. Palladium impregnated over CuO/CeO2 synthesized by co-precipitation method showed excellent catalytic activity for phenol hydrogenation (99% conversion with 80% cyclohexanol yield) at 90 degrees C and 10 bar H-2 pressure in water. Commercial 10%Pd/C showed only 8% phenol conversion under identical conditions. The detailed characterization revealed significant improvement in surface area of ceria after addition of CuO and decrease in crystallite size with creation of defects in CeO2 lattice. XPS analysis showed Pd loading on CuO/CeO2 to cause hydrogen spillover on the surface leading to increase in the oxygen vacancies. The interaction of phenol with catalyst surface studied by detailed FTIR analysis, revealed activation of phenol on oxygen vacancy of ceria as phenoxide ion with perpendicular orientation of aromatic ring on catalyst surface.

10aCyclohexanol10aHydrogen spillover10aoxygen vacancies10aPd-CuO/CeO210aphenol hydrogenation1 aKasabe, Mirabai, M.1 aKotkar, Vaibhav, R.1 aDongare, Mohan, K.1 aUmbarkar, Shubhangi, B. uhttp://library.ncl.res.in/content/phenol-hydrogenation-cyclohexanol-catalysed-palladium-supported-cuoceo2