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.

 

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[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).

           

[2].      J. Fang, H. Jin, T. Ruddy, K. Pennybaker, D. Fahey and B. Subramaniam, “Economic and Environmental Impact Analyses of Catalytic Olefin Hydroformylation in CO₂-Expanded Liquid (CXL) Media,” Industrial and Engineering Chemistry Research, 46, 8687-8692 (2007).