Ru, Pt and Co clusters in zeolite micropores; EXAFS/FTIR/TPD characterization and catalytic behaviors in methane homologation

Ru 3 (CO) 12 , H 4 Ru 4 (CO) 12 , [HRu 6 (CO) 18 ] - , Co 4 (CO) 12 , Rh 6 (CO) 16 and [Pt 12 (CO) 24 ] 2- were synthesized in NaY cages by a "ship-in-bottle" technique. Highly dispersed Ru, Rh, Pt and Co clusters (less than 10A size) in NaY were prepared by the oxidation and evacuation at 423K to remove CO, followed by H 2 reduction and were characterized by EXAFS and TPD/FTIR. Upon methane decomposition at 523-723K, the reactive Cα and Cβ species (with a negligible graphic Cγ) were preferentially formed on the Ru, Rh and Pt clusters in NaY, which were hydrogenated at 300-473K mainly to methane and ethane (less than 24% sel on carbon base). The selectivity of C 2 + products was varied in the following order; Ru 3 /NaY>Ru 4 /NaY>Ru 6 /NaY>Pt 12 /NaY, Rh 6 / NaY >Ru (50A) on NaY and Ru/Al 2 O 3 . The mechanism of homologation of ethene and propane with methane deposited on Ru 3 /NaY were discussed in conjunction with reactivities of carbon species(Cα and Cβ) as well as self-homologation.