We synthesized phosphine-modified Rh/SiO2 catalysts for the gas-phase hydroformylation of propene to butanals.  Screening of different ligands showed that a bidentate xantphos (X) ligand was nearly two 2-fold more active than the monodentate phosphine ligand (PPh3) screened at a ligand-to-rhodium ratio of 15:1. Characterization studies using in- situ FT-IR and solid-state 31P MAS NMR provide evidence for the formation of HRh(CO)2(X) species on xantphos-modified Rh/SiO2 (X-Rh/SiO2). The kinetics of propene hydroformylation over X-promoted Rh/SiO2 is nearly identical to those for sulfoxantphos-modified rhodium-containing supported ionic liquid phase (SX-Rh SILP) catalysts, showing the formation of similar active species formed over the two class of supported phosphine-modified rhodium-silica catalysts. For example, the hydroformylation of propene at 393 K and 2 atm pressure using Rh- SX-SILP and X-Rh/SiO2 catalysts exhibits a turnover frequency of 100 h-1 and a regioselectivity (n/iso) ratio of 14.  Results from our experiments also indicate that a combination of X-Rh/SiO2 catalyst and a CO tolerant Shvo/SiO2 can perform the tandem conversion of propene to butanols with 15% propene conversion and greater than 90% selectivity to butanols at 413 K and a total pressure of 3 atm.

Tandem conversion of alkenes to alcohols using supported catalysts

246th National Meeting (2013)

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