PEG Biphasic System And Its Applications In The Hydroformylation Of Higher Olefins

In this paper, a novel thermoregulated nonaqueous liquid/liquid biphasic system, PEG biphasic system was proposed, which was composed of PEG organic solvents and phosphine ligand with PEG chains. The feature of PEG biphasic system was the combination PEG and phosphine ligand with PEG chains. So the solubility of catalyst in PEG phase was increased. PEG biphasic system with the property of "homogeneous reaction at high temperature, and heterogeneous separation at low temperature" had both advantages of high reactivity and easily separated catalyst from the products phase.A new kind of phophite ligand with PEG chains named tri-(methoxyl polyethylene glycol)-phosphite (TMPGP, I ) was designed and synthesized in this work. TMPGP and OPGPP( II), the later was previously synthesized in our group, were successfully applied in PEG biphasic system. PEG biphasic system have very well recycling efficiency on the catalyst of Rh complex on the hydroformylation of p-isobutylstyrene (IBS) and 1-dodecene.Based on the study of phase-diagram and the distribution of phosphite ligand between two phases, PEG biphasic system composed of PEG, toluene, heptane and OPGPP or TMPGP was established, which have the property of "two-phase at low temperature and one-phase at high temperature". The hydroformylation of higher olefins were investigated in three kinds of PEG biphasic systems which were PEG-4000/toluene-heptane/OPGPP (A), PEG-4000/toluene-heptane/TMPGP (B) and PEG-800/toluene-heptane/TMPGP (C). In the system (A), under the optimumconditions, the IBS conversion and aldehyde yield were up to 98.6% and 96.4% respectively, TOF was 386h-1. The PEG phase containing catalyst can be recycled 6 times no loss of activity. The average loss of Rh in upper products phase was about 6%(wt) at first six times running. However, the system (B) had higher activity and better recycling efficiency than system (A). At system (B), IBS converted completely and the aldehyde yield was 96.3%, TOF reached 500h-1 The catalyst was reused for the nine times without clearly loss of activity. The average loss of Rh in upper products phase was about 3%(wt). At system (C), hydroformylation of 1-dodecene was studied and the catalyst in PEG phase was recycled seven times without loss activity and the maximal loss of Rh in upper product phase only 2.1%(wt). Comparing with other biphasic systems with PEG as polar phase, PEG biphasic system was the best one for the catalyst holding and recycling. So, PEG biphasic system provided a possible way to resolve the problem of separation the catalyst from products in homogenous catalysis process.