Platelet millimetric reactors (PMR, 18 mm x 5 mm x 24 or 120 mm) packed with open cell foam supporting Pt nanoparticles have been studied with a model reaction (formic acid oxidation). The hydrodynamics of the liquid phase was investigated as a function of gas and liquid superficial velocities and foam properties using classical residence time distribution (RTD) experiments. The gas-liquid mass transfer coefficient (k(L)a) was also studied by using an oxygen absorption in water for cocurrent up flow and down flow configurations with the velocities range of 1.1 < u(g) < 2.2 mm.s(-1) for air and 0.075 < u(l) < 0.2 m.s(-1) for liquid. It was found that an increase of gas velocity had no significant effect on gas-liquid mass transfer, contrary to an increase in liquid velocity. A correlation for k(L)a prediction was proposed based on a dimensionless numbers relation. A specific protocol was optimized to obtain an acceptable dispersion of Pt nanoparticles on SiC foam. Intrinsic catalytic activity was obtained in the chemical regime using a dedicated basket-type batch reactor adapted to solid foam in which the first-order kinetic constant was determined. Finally, experiments under a formic oxidation reaction with PMR have been performed. A simulation, based on the well-known axial-dispersion model for liquid phase and using hydrodynamic, mass transfer, and kinetic parameters determined in this work, was performed, and a good agreement was found with experiment without any parameters adjustments. The platelet configuration was also compared to a tubular configuration by simulation.