Mono (Ru or Co-based) and bimetallic (Co-Ru-based) silica supported catalysts have been prepared in order to evaluate the stability of metallic ruthenium after different thermal treatment. In all the samples the loading of cobalt is 10 wt% while the loading of ruthenium ranges from 0.5 to 10 wt%. Several analytic techniques (XRF, TGA, XRD, DRIFT) have been employed to shed light on the composition and the chemical-physical properties of prepared catalysts after calcination both in air or nitrogen atmosphere, in static environment or under dynamic flow. In particular, ruthenium resulted to be not stable in monometallic systems under calcination and air flow strongly favored the Ru loss. The behavior of bimetallic catalysts after thermal treatment was completely different thus indicating the role of cobalt as a stabilizer of metallic Ru phase probably due to the formation of a very stable spinel structure, as referenced in literature.