Catalytic hydroformylation of olefins over the rhodium, bimetallic RhCo, and cobalt carbonyl clusters supported with some metal oxides

Abstract

Vapor-phase hydroformylation of ethylene and propene proceeded under atmospheric pressure at 25 to 180°C over the Rh and Co carbonyl clusters such as Rh 4 (CO) 12 , Rh 6 (CO) 16 , Rh 2 Co 2 (CO) 12 , RhCo 3 (CO) 12 , and Co 4 (CO) 12 supported with some specific metal oxides such as ZnO and MgO. It was suggested that the supported carbonyl clusters catalyzed the hydroformylation reactions when they were partially decarbonylated by subjecting to heat treatment in vacuo or under hydroformylation atmosphere. The activities and linear-isomer selectivities of aldehyde formation depend not only on the kinds of precursor carbonyl clusters but also on the metal oxides as supporting carriers: The specific activity order at 158°C for Rh carbonyl clusters supported on ZnO was Rh 4 (CO) 12 > Rh 6 (CO) 16 > Rh 7 (CO) 16 3NEt 4 > Rh 13 (CO) 23 H 2–3 2NBu 4 with a total range of ∼10. In contrast, the catalysts prepared from Rh(CO) 2 Cp, Rh 2 (CO) 3 Cp 2 , and RhCl 3 impregnated on ZnO showed negligible or small conversions in the reactions under similar conditions. The Rh carbonyl clusters were possibly stabilized with the basic oxides such as ZnO, MgO, TiO 2 , and La 2 O 3 , exhibiting higher hydroformylation activities. On the other hand, the hydroformylation reactions negligibly proceeded over the carbonyl clusters dispersed on acidic oxides such as alumina, silica-alumina, and V 2 O 5 . The bimetallic Rh Co cluster-derived catalysts exhibited higher selectivity of normal-isomer aldehyde, suggesting that Co atoms in the supported bimetallic Rh Co clusters behave as electronic “donor-ligand” to promote normal-intermediate on top of rhodium atom active for olefin hydroformylation reactions.