制备方法对均相多相化钯催化剂活性物种的影响

近年来,多相化均相催化剂的研究,在有机合成、石油化工、精细化工等领域引起了广泛关注.和多相催化剂一样,负载化均相催化剂的性能也与制备技术有较大的关系.如在研究氯化钯、聚乙烯吡咯烷酮(PVP)和氧化铝所组成的双重负载催化剂时,虽然所用组分一样,比例相同,但由于负载顺序不同,所得催化剂的活性和重复使用性相差很大.国内外学者曾对类似催化剂的表征进行过讨论,认为催化剂的活性中心是在胶体保护的金属钯颗粒上.对于负载顺序的效应,则未见报道.我们以CO为探针

EFFECT OF PREPARATION PROCEDURE ON ACTIVE SPECIES IN IMMOBILIZED HOMOGENEOUS Pd CATALYST

The effect of immobilizing procedure on the active species in dual supported homogeneous catalysts, i. e. PdC12 supported on polyvinyl pyrrolidone (PVP) and A12O3, was studied by FT-IR spectroscopy using CO as probe. When Pd content in the catalyst was 0.2%, the catalyst prepared by coordinating PdCl2 with PVP and then supporting on A12O3 did not adsorb CO, indicating that Pd in this catalyst existed in coordinating atomic state, it exhibited high hydrogenation activity and stability. The catalyst obtained by supporting PVP on A12O3 and then coordinating with PdCl2 could adsorb CO, the CO stretching vibration of bridge and linear forms were observed in IR spectra at 1919 and 2064 cm-1 respectively, indicating that in this catalyst, besides the coordinating Pd atom, there existed partly the aggregated Pd particles as well.