催化剂-Topsoe-Review2009.pdf

Top Catal (2009) 52:1303–1311 DOI 10.1007/s11244-009-9314-1 ORIGINAL PAPER Nano-Particles in Heterogeneous Catalysis Alfons M. Molenbroek Æ Stig Helveg Æ Henrik Topsøe Æ Bjerne S. Clausen Published online: 26 June 2009 Springer Science+Business Media, LLC 2009 Abstract The introduction of in situ techniques has had a 1 Introduction vast impact on research and development in the area of heterogeneous catalysis as emphasized in many reviews Solid particles with a size of below approximately 20 nm and monographs. Recently, the number of in situ tech- have a large fraction of their atoms present at the surface. niques that can give information at the atomic scale has The characteristics of the surface atoms are significantly increased significantly and new possibilities exist for different from atoms in deeper layers, as e.g. bond dis- making the measurements under industrially relevant con- tances, geometries, and bonding energies are altered by the ditions. In order to fully exploit the results from the in situ reduced local coordination at the surface. Also the atomic and operando studies, it has also become increasingly composition at the surface might be different than that in gainful to combine the experimental studies with theoret- the bulk of the particle. ical methodologies based on, for example, Density Func- In heterogeneous catalysis, the special properties of the tional Theory (DFT). This has allowed one to extract more surface atoms facilitate conversion of reactants into prod- detailed atomic-scale information from the measurements ucts at active surface sites. The properties of the active and it has also allowed the establishment of detailed surface sites depend among others on the type and number structure