Structure, Activity, and Stability of Triphenyl Phosphine-Modified Rh/SBA-15 Catalyst for Hydroformylation of Propene: A High-Resolution Solid-State NMR Study

A ligand (triphenyl phosphine, PPh 3 )-modified heterogeneous PPh 3 −Rh(CO)/SBA-15 catalyst and supported Wilkinson complex HRh(CO)(PPh 3 ) 3 /SBA-15 catalyst were prepared and examined in the hydroformylation of propene. Heterogeneous PPh 3 −Rh(CO)/SBA-15 catalyst showed much higher activity and stability in this reaction. Multinuclear 1 H, 29 Si, 31 P, and 17 O MAS NMR and two-dimensional 17 O MQ MAS NMR together with XRD and N 2 adsorption were employed to study the local structures of these two catalysts. Quantitative 1 H and 29 Si MAS NMR and qualitative one- and two-dimensional 17 O MAS and MQ MAS NMR indicate that in the presence of CO the silanols on the surface of SBA-15 can react with rhodium carbonyls to form the Si−O−Rh bonds at the interface between the catalyst and the support. 31 P MAS NMR spectra demonstrate a similar Wilkinson complex structure is produced on the heterogeneous PPh 3 −Rh(CO)/SBA-15 catalyst. The formation of Si−O−Rh bonds at the interface may immobilize the Rh complex during the long reaction. These may be correlated to the higher performances of heterogeneous PPh 3 −Rh(CO)/SBA-15 catalyst in propene hydroformylation.