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743363 
Journal Article 
Surface Chemistry Special Feature: Planar oxide supported rhodium nanoparticles as model catalysts 
Mcclure, SM; Lundwall, MJ; Goodman, DW 
2010 
1 
Proceedings of the National Academy of Sciences of the United States of America
ISSN: 0027-8424
EISSN: 1091-6490 
108 
3 
931-936 
English 
20947802 
WOS:000286310300012 
C(2)H(4)/CO/H(2) reaction is investigated on Rh/SiO(2) model catalyst surfaces. Kinetic reactivity and infrared spectroscopic measurements are investigated as a function of Rh particle size under near atmospheric reaction conditions. Results show that propionaldehyde turnover frequency (TOF) (CO insertion pathway) exhibits a maximum activity near <d(p)> = 2.5 nm. Polarization modulation infrared reflection absorption spectroscopy under CO and reaction (C(2)H(4)/CO/H(2)) conditions indicate the presence of Rh carbonyl species (Rh(CO)(2), Rh(CO)H) on small Rh particles, whereas larger particles appear resistant to dispersion and carbonyl formation. Combined these observations suggest the observed particle size dependence for propionaldehyde production via CO insertion is driven by two factors: (i) an increase in propionaldehyde formation on undercoordinated Rh sites and (ii) creation of carbonyl hydride species (Rh(CO)H)) on smaller Rh particles, whose presence correlates with the lower activity for propionaldehyde formation for <d(p)> < 2.5 nm. 
Ethylene hydroformylation; CO insertion; polarization modulation infrared reflection absorption spectroscopy; Rh/SiO2 
• Nanoscale Carbon