Continuous Homogeneous Hydroformylation with Nanofiltration for Retention of Polymer Supported Rh Catalyst Complexes

Introduction Industrial higher olefin (> C5) hydroformylation processes require harsh temperatures and pressures (140 200 oC, 5 30 MPa) as well as tedious catalyst separation schemes involving hazardous reagents to recycle the cobalt catalyst [1]. The use of rhodium (Rh) as a catalyst would lower the operating temperature and pressure but requires almost quantitative recovery and recycle of the costly catalyst. In our previous work, higher olefin (1octene as model substrate) hydroformylation with a modified rhodium catalyst complex was performed in CO2-expanded liquid (CXL) media at mild pressures (tens of bars) and temperatures (< 100 oC) [2]. The batch experiments gave reasonable turnover frequency and high selectivity towards the linear C9 aldehyde. For economic viability, analysis suggests a maximum Rh loss of 0.2% per pass during continuous operation [3]. This paper shows how this target is achieved by employing nanofiltration with specially designed soluble polymer supported phosphite ligands.