Surface organometallic chemistry on metals : kinetics of the hydrogenolysis of tetra n-butyl tin on silica and alumina supported rhodium catalysts

摘要: Abstract The stoichiometry and the kinetics of hydrogenolysis tetra n-butyl tin on silica alumina supported rhodium catalysts has been determined at 298 K in n-heptane. Various Rh/SiO 2 Rh/Al O 3 have prepared by exchange from [RhCl(NH ) 5 ] (OH) impregnation RhCl respectively. After reduction, metallic dispersions were found to vary 0.45 0.9 as hydrogen chemisorption measurements. Concerning organotin complex, amount grafted was depend introduced: since this is lower than value corresponding a ratio Sn/Rh s 0.7, all complex directly proportional number surface atoms; average, each atom able graft 0.8 Sn(n-C 4 H 9 x fragment. Above ratio, almost independent introduced. These results strongly support hypothesis that reaction occurs selectively surface. hydrogenolysis, butane evolved per mole tin, depends coverage surface: for low coverage, butyl groups are hydrogenolyzed, showing formation ‘naked’ atoms. For full some remain fixed presence species also time given concentration tin: short times which correspond coverages particles, removed whereas phenomenon not observed longer alkyl Kinetics indicates first order ‘free adsorption site’ zero tin.