Liquid/Liquid Two-phase Hydroformylation Of Oleyl Alcohol Based On Rhodium Catalysts

The high selectivity and mild conditions make the rhodium process more attractive than the cobalt one for the hydroformylation of olefins. However, the rhodium process with oil compounds encounter problems due to the thermal sensitivity of the high boiling point oxo-products, which cannot be isolated from the homogeneous reaction mixture by distillation. On the other hand, the high cost of rhodium makes near-complete catalyst recovery a must for the hydroformylation based on rhodium catalyst, which allows for a catalyst recycling and oxo-products separation by phase separation would be highly desirable.In this paper, we report three liquid/liquid two-phase solvent systems for the Rh catalyzed hydroformylation of oleyl alcohol (OA)(see the following Figure), which is a clean and atom economic "green" pathway for the utilization of successive vegetable resource.CO/H2 OHCOleyl Alcohol Formyloctadecyl alcoholIn a first series of experiments, we report four different water-soluble phosphine ligands on the aqueous biphasic Rh-catalyzed hydroformylation of OA for the first time. The aldehyde yield reached 83.6% within 6hrs under 140癈 and S.OMPa (CO/H2, 1/1) with Rh/PETPP-M (Structure I) complex; the separated catalyst dissolved in the aqueous phase could be reused for 3 times without evident changes in activity. In conclusion, although OA is absolutely insoluble in water, considerable high aldehyde yield was achieved in our experiments thanks to these special ligands. we presumed that this reaction proceeding effectively and steadily can only be based upon the thermoregulated phase transfer catalysis (TRPTC) concepts.(OCH2CH2)25OH PETPP-MIAlthough phosphites are well known ligands for the Rh-hydroformylation to afford higher reaction rates and we found1-3that the Rh/OPGPP (Structure II) complex formed in situ was highly active in the aqueous biphasic hydroformylation of OA and the aldehyde yield reached 85.4% at relatively low temperature 130癈; considerable loss in activity (in the 3nd run, the aldehyde yield only reached 40%) has been observed when recycling experiments were proceeded because of ligand's instability toward hydrolysis.oP?OCH2CH2)570C8H17n OPGPP OIIIn a second series of experiments to avoid using water as solvent in biphasic system due to the sensibilty of the O-P bond in OPGPP to water. Preliminary attempts to determine the solubility of PETPP-M in organic solvent at different temperature found surprisingly that PETPP-M could dissolve in certain hot solvent and it precipitated from the solution when cooling to room temperature. To ensure the P content in the organic phase at room temperature as little as possible, we selected heptane as the solvent because of a very low solubility of OPGPP in heptane at 16癈 . When OPGPP/Rh complex was applied to the hydroformylation of OA in heptane, the aldehyde yield reached 68.6% within 6hrs under 130 癈 and S.OMPa (CO/H2, 1/1); the precipitated catalyst could be recycled 4 times without loss in catalytic activity.Ionic liquids are salts that are liquid at low temperature (<100癈) which represent a new class of solvents for nonaqueous two phase reaction system.In a third series of experimnets, we have prepared a novel class of ionic liquid: polyether melt, whose most important structure feature is an ammonia salt with at least one polyether chain and is liquid at room temperature. PEM-1 (Structurelll)were prepared by directed neutration reaction starting from polyether-tailored 1-dodecylamine with p-toluenesulfonic acid. Interestingly, we found that PES-1 form biphasic systems with heptane. This gave rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. Thus, we performed OA hydroformylation based on Rh catalyst under PEM-1/heptane two-phase solvent system. Under 135 癈, 5.0MPa(CO/H2,l/l) and 8hrs reaction conditions, the aldehy...