Selective CO methanation (S-MET) measurements were carried out in a Microactivity PID Eng&Tech equipment using a 9 mm internal diameter tubular AISI316 stainless steel reactor (Autoclave Engineers). The powder samples (140 mg sieved in the 100-200 µm range), were diluted in a volume of glass particles sieved in the same diameter range (100-200 µm) equal to that occupied by the micromonolithic devices (6 cm3). The feed gas simulating an output stream from PROX unit consists of 0.03% CO, 15 % CO2, 50% H2, 15% H2O and N2 as balance. The WHSV (Weight Hourly Space Velocity) was fixed at 80000 ml.g-1.min-1. For micromonoliths a tubular reactor (16 mm inner diameter) was employed and the total flows for methanation reaction were adjusted to achieve the same WHSV as for the powder tests. Before reaction the samples were in-situ pre-activated at 300oC for 2 h in 60 ml/min pure H2 flow, purged with N2, and then conditioned at 105oC for 1 h within the reaction mixture. The methanation activity was evaluated from 105oC to 270oC.