(674b) Continuous Homogeneous Hydroformylation of 1-Octene with in Situ Membrane Filtration for Separation of Soluble Polymer Bound Rhodium Complexes

In previous
work, it as shown that rhodium catalyzed hydroformylation of higher olefin
(1-octene as model substrate) was enhanced by CO₂ addition, giving
reasonable turnover frequency (~300 h^-1) and higher selectivity
towards the linear aldehyde (~90%) at mild pressures (~40 bar) and temperatures
(60 °C).[1]
Preliminary economical analysis indicates that greater than 99.8% of Rh-based
catalyst has to be recovered for economic viability.[2]
To achieve the targeted Rh recovery rate, CEBC researchers synthesized a series
of bulky, soluble and recyclable polymer bound phosphorus ligands to facilitate
quantitative Rh retention in homogeneous hydroformylation reaction mixtures
using nano/ultra-filtration membrane techniques.  Both batch and continuous filtrations were conducted in a
commercially available high-pressure MET cell under air-free operation equipped with a solvent-resistant, polyimide STARMEM^® membrane.  The retention of the catalyst
precursor Rh(acac)(CO)₂ bound to various ligands, including TPPine,
bidentate ligands and polymer bound ligands, were investigated.  As expected, the size of the ligands
significantly affects the Rh retention. During continuous filtration of a
toluene-based solution containing bidentate polymer bound Rh complexes, the Rh
and P concentrations in the permeate, quantified using ICP analysis, were on
the order of a few tens of ppb. The catalyst activity, regioselectivity and Rh
retention for continuous homogeneous hydroformylation of 1-olefin in stirred
reactors with in situ membrane
filtration of such catalyst complexes will be presented.

 

[1].
     H.
Jin, A. Ghosh, J. A. Tunge and B. Subramaniam, "Intensification of
Catalytic Olefin Hydroformylation in CO₂-expanded Media", AIChE Journal,  52(7), 2575-2591 (2006).