Effect of Particle Size upon Pt/SiO 2 Catalytic Cracking of n ‐Dodecane under Supercritical Conditions: In situ SAXS and XANES Studies

The endothermic cracking and dehydrogenation of n ‐dodecane is investigated over well‐defined nanometer size platinum catalysts supported on SiO 2 to study the particle size effects in the catalytic cracking reaction, with simultaneous in situ monitoring of the particle size and oxidation state of the working catalysts by in situ SAXS (small angle X‐ray scattering) and XAS (X‐ray absorption spectroscopy). The selectivity toward olefins products was found dominant in the 1 nm size platinum catalysts, whereas paraffins are dominant in the 2 nm catalysts. This reveals a strong correlation between catalytic performance and catalyst size as well as the stability of the nanoparticles in supercritical condition of n ‐dodecane. The presented results suggest that controlling the size and geometric structure of platinum nanocatalysts could lead to a fundamentally new level of understanding of nanoscale materials by monitoring the catalysts in realistic reaction conditions.