Surface-grafted metal oxide clusters and metal carbonyl clusters in zeolite micropores; XAFS/FTIR/TPD characterization and catalytic behavior

Abstract SiO 2 -grafted [( μ 3 -C 4 H 7 ) 2 Rh] 2 V 6 O 12 and [(RhCp ∗ ) 4 V 6 O 19 ] as molecular models of supported Rh catalysts characterized by EXAFS, FTIR, and TPD exhibit high catalytic activities for selective oxidation of propene towards acetone. SiO 2 -impregnated triple cubane-type complete [(RhCp ∗ ) 4 Mo 4 O 16 ] and incomplete (RhCp ∗ ) 2 Mo 3 O 9 (OMe) 4 were reduced under photoillumination (> 365 nm) in CO at 300 K, forming two sets of the intense carbonyl bands at (2061 and 2021 cm −1 ) and (2092 and 2035 cm −1 ). All the carbonyls attracted to Rh and Mo sites were eliminated by the thermal evacuation at 330–440 K, leaving oxygen-deficient sites of Mo in the cubane-oxide clusters, which exhibited high catalytic activities for propene metathesis at 300–343 K. We have conducted the low-temperature homologation of methane on a series of zeolite-entrapped Ru, Rh, Co and Pt catalysts which were prepared from Ru 3 (CO) 12 /NaY, H 4 Ru 4 (CO) 12 /NaY, [HRu 6 (CO) 18 ] − /NaY, Co 4 (CO) 12 /NaY, Rh 6 (CO) 16 /NaY, [Pt 3 (CO) 3 ( μ 2 -CO) 3 ] n 2− ( n = 3, 4)/NaY. The carbon species [CH x ] ( x = 0–3) are deposited on naked metal clusters in NaY by admission of methane at 423–623 K, which are stoichiometrically converted by hydrogen at 300–423 K towards C 1 -C 5 hydrocarbons without any formation of graphic carbons. The yields of C 2 + hydrocarbons in methane homologation were affected by the size of Ru clusters and carbon coverage θc, as follows; Ru 3 /NaY 4 /NaY 6 /NaY