Upon reduction at 975 degrees C, a strong metal-support interaction (SMSI) of CeO2 on Pt NPs leads to low rates for ethylene hydrogenation and propane dehydrogenation, but high olefin selectivity for the latter reaction. By contrast, reduction at 550 degrees C of Pt/CeO2, leads to 5 nm Pt NP's with ethylene hydrogenation and propane dehydrogenation TORs and low olefin selectivity similar to Pt/SiO2. X-ray absorption fine structure (EXAFS) and scanning transmission electron microscopy (STEM) shows formation of -15 nm monometallic Pt nanoparticles partially covered by SMSI CeO2. The propylene selectivity of Pt NP's covered by SMSI CeO2 was -95 % suggesting there were few Pt ensembles capable of catalysing propane hydrogenolysis; while the remaining exposed Pt remain active for dehydrogenation reactions.