Effect of pore structure of amine-functionalized mesoporous silica-supported rhodium catalysts on 1-octene hydroformylation

Amine-functionalized mesoporous silicas with different pore sizes (MCM-41, SBA-15 and amorphous silica) were prepared using the post-synthesis method. Subsequently, rhodium was immobilized on the aminated mesoporous silica materials in order to be evaluated as a heterogeneous catalyst for 1-octene hydroformylation. Two kinds of amine compounds, namely (N(β-aminoethyl) γ-aminopropylmethyldimethoxysilane (AEAPMDMS) and 3-aminopropyltriethoxysilane (APTES) were compared as functional groups for the immobilization of the rhodium complex. Three kinds of rhodium-immobilized mesoporous silicas whose pore structure differs from one another, such as MCM-41 (pore size; 2.5-2.7 nm, ordered hexagonal pore structure), SBA-15 (pore size; 4.2-4.5 nm, ordered hexagonal pore structure) and amorphous silica (pore size; 8.8-9.2 nm, worm-like structure) were selected to elucidate the effect of the pore structure on the 1-octene hydroformylation. The larger pore and ordered pore structure would be favorable in terms of total aldehyde yield and activity. In addition, AEAPMDMS, which has two nitrogen atoms, was superior to APTES as a functional agent in the 1-octene hydroformylation due to its stronger electron-donating effect toward the Rh complex. Among the synthesized catalysts, SBA-15/AEAPMDMS/Rh represented the highest yield of aldehyde in the 1-octene hydroformylation at about 48%.