【摘要】 用红外光谱考察了氢甲酰化反应过程中铑膦催化剂结构的变化,讨论了可能的催化活性物种和失活的原因。结果表明,氧的存在对氢甲酰化反应直接产生抑制作用,但在我们的实验条件下,催化剂的失活不能归因于三苯膦的氧化和碳膦键的断裂。失活可能主要是由于原位生成的活性物种在反应过程中不断缔合,生成了非活性的膦取代的铑原子簇。更多还原

【Abstract】 The deactivation mechanism of phosphine modified rhodium cluster catalyst for the hydroformylation of olefin under mild conditions (50℃, 0.1MPa)has been investigated by infrared spectroscopy and high performance liquid chromatography. The results show that the deactivation of the catalyst is neither due to the cleavage of P-C bond of the ligand nor due to the oxidation of PPh3. IR spectra show that the structure of Rh--PPh3 cluster system changes with time during the reaction and it is accompanied with the change of color of the catalyst solution from red to yellow and then to red again. Only when the toluene solution of the catalyst is yellow in color, the catalyst shows high activity, this yellow substance is only slightly soluble in heptane. It is suggested that the yellow solid separated from heptane solution is a mixture of Rh2(CO)4-(PPh3)4 and Rh2(CO)6(PPh3)2. It is considered that these dimers are the active species. Under atmospheric pressure, the decay of the catalyst activity is attributed to the instability of the active species.更多还原