Anionic clays as precursors of noble metal based catalysts for methane activation

Rh, Ru, Ir, Pd and Pt based catalysts were prepared from hydrotalcite-type (HT) anionic clays, and their activity in the catalytic partial oxidation(CPO) or catalytic total oxidation (CTO) of methane was investigated. Pt2+ were the only ions which did not fully coprecipitate in the HT precursors. The nature of the noble metal ions determined also the amount that did not segregate by calcination at 900 degrees C and remained inside spinel-type phases. In the CPO reaction. the syngas synthesis decreased according to the order Rh > Ru congruent to Ir much greater than Pt > Pd. The best catalytic performances were observed for a 1% Ph content las atomic ratio) and Rh contents above 1% did not increase the activity? unlike that observed for Ru based catalysts. In the CTO of methane lower lightoff temperatures were observed for Pd, Ph and Ir based catalysts but good performances at high methane conversion were found only for the Pd based catalyst, while the Rh and, mainly, Lr based catalysts deactivated with time-on-stream, due to oxidation or sintering phenomena.