Partial oxidation of propylene was investigated at 1 atm pressure over Rh/TiO2 catalysts as a function of reaction temperature, metal loading and particle size using high-throughput methods. Catalysts were prepared by ablating thin sheets of pure rhodium metal using an excimer laser and by collecting the nanoparticles created on the external surfaces of TiO2 pellets that were placed inside the ablation plume. Rh nanoparticles before the experiments were characterized by transmission electron microscopy (TEM) by collecting them on carbon film. Catalyst evaluations were performed using a high-throughput array channel microreactor system coupled to quadrupole mass spectrometry (MS) and gas chromatography (GC). The reaction conditions were 23% C3H6, 20% O2 and the balance helium in the feed, 20,000 h-1 GHSV and a temperature range of 250-325 oC. The reaction products included primarily acetone (AT) and to a lesser degree propionaldehyde (PaL) as the C3 products, together with deep oxidation products COx.