Aqueous phosphine–Rh complexes supported on non-porous fumed-silica nanoparticles for higher olefin hydroformylation Original Research Article

Non-porous fumed-silica nanoparticles were used as supports for the first time to immobilize water-soluble complex HRh(CO)(P(m-C6H4SO3Na)3 (1) [P(m-C6H4SO3Na)3, i.e. trisodium salt of tri-(m-sulfophenyl)-phosphine, TPPTS] to obtain supported aqueous-phase catalysts (SAPC) (fumed-SiO2-SAPC) for hydroformylation of 1-hexene. The experimental results proved that the structure of support and the support hydration were the determining factors contributing to the hydroformylation performance. The fumed-SiO2-SAPC where the water-soluble rhodium complexes were well dispersed onto the external surface of the silica nanoparticles presented a higher hydroformylation performance over a relatively wider range of support hydration as compared to the SAPC with conventional porous granular-SiO2 support (porous SiO2-SAPC). A positive effect on the reaction performance was observed from the particle size and surface area of the fumed-silica nanoparticles. The hydroformylation performance with fumed-SiO2-SAPC was promoted by an addition of basic alkali metal salts such as Na2CO3, K2CO3, and NaH2PO4, which depressed the oxidation of ligand TPPTS to OTPPTS [OTPPTS, i.e. trisodium salt of tri-(m-sulfophenyl)-phosphine oxide, OP(m-C6H4SO3Na)3] as evidenced by 31P NMR observation.