(20d) Continuous Hydroformylation With Nanofilterable Rh Catalyst Bound to Polysiloxane Ligands in a Stirred Membrane Reactor

Recently, we reported continuous 1-octene
hydroformylation with bulky phosphite ligands¹
in a stirred reactor equipped with nanofiltration membranes under either syngas
pressure only²
or CO₂-expanded liquids (CXLs).³
It was shown that the Rh leaching from these reactors is less than 1ppm, which
easily exceeds the economic viability criterion.⁴
 While JanaPhos ligand has many benefits, it involves tedious synthesis
steps and is air- and moisture-sensitive, making cost-effective large-scale
synthesis difficult. Rh complex catalysts bound to inexpensive soluble polysiloxanes
ligands are investigated as alternatives for the hydroformylation of higher
olefins (C₅₊). Polysiloxanes containing two different functional
groups (amine- and phosphine-) were used for synthesis of Rh catalysts. Both
types of Rh complexes show good chemoselectivity and stability when tested in
batch and continuous hydroformylation experiments. The phosphine-functionalized
ligand exhibited higher activity than the amine functionalized one. Continuous
operation lasting several days was demonstrated in a stirred reactor equipped
with nanofiltration membrane with steady hydroformylation activity (TOF = 193 h^-1,
cumulative TON after 120 hours was 12,240) and high chemoselectivity (> 91
%) towards the aldehydes. The Rh concentrations in the reactor effluent were
less than a few ppm, which can be easily recovered by adsorption. In addition,
the idea of using gas-expanded liquids to enhance H₂/CO ratio and
reduce CO inhibition during hydroformylation reactions catalyzed by Co-based
complexes is also discussed.

1.            Jana R, Tunge JA. A Homogeneous, recyclable
rhodium(I) catalyst for the hydroarylation of Michael acceptors. Org Lett. 2009;11:971-974.

2.            Fang
J, Jana R, Tunge JA, Subramaniam B. Continuous homogeneous hydroformylation
with bulky rhodium catalyst complexes retained by nano-filtration membranes. Appl
Catal, A. 2011;393:294-301.

3.            Xie
Z, Fang J, Maiti S, Snavely W, Tunge J, Subramaniam B. Enhanced
Hydroformylation by Carbon Dioxide-Expanded Media with Soluble Rh Complexes in
Nanofiltration Membrane Reactors. AIChE Journal. 2013;in press.

4.            Fang
J, Jin H, Ruddy T, Pennybaker K, Fahey D, Subramaniam B. Economic and
environmental impact analyses of catalytic olefin hydroformylation in CO₂-expanded
liquid (CXL) media. Ind Eng Chem Res. 2007;46:8687-8692.