担载液相催化剂的研究——Ⅴ. 担载液相催化剂的EXAFS表征

Study of Supported Liquid Phase Catalyst (SLPC) Ⅴ . EXAFS Characterization of SLPC

本文利用EXAFS(Extended X-ray Absorption Fine Structure)对铑基担载液相催化剂(Supported Liquid Phase Catalyst SLPC)进行了结构表征。采用球面波理论对SLPC的EXAFS结果进行了多参数拟合。结果表明,在新鲜催化剂上,铑络合物以二聚物形式存在,推测其结构为(PPh_3)_2(CO)Rh-Rah(CO)(PPh_3)_2,Rh-C-O偏离共线分布。在经过羰化反应活化的活性SLPC上,铑络合物为单核的HRh(CO)_2(PPh_3)或Rh(CO)_2(PPh_32)_3。文中还讨论了SLPC的XRD谱。

Rhodium based SLPCs (Supported Liquid Phase Catalyst) were characterized by EXAFS (Extended X-ray Absorption Fine Structure) in which multi-parameter fitting was carried out using spherical wave scattering theory. The SLPC was prepared by dry impregnation under nitrogen atmosphere. The catalyst solution was consisted of HRh(CO) (PPh3)3, PPh3and benzene. EXAFS data were taken at BL- 10B station of Photon Factory, Japan, with an electron beam energy of 2. 5GeV and average stored current of 250 mA. The measurement was made with Si(311) channel-cut as the monochrometer and in transmission mode. The data processing was done on a SUN 386/P9 microcomputer with the program library for EXAFS data processing written by the Institute of Physics, Chinese Academy of Sciences. The results indicated that rhodium complexes exist as a dimer on the fresh SLPC and its suggested structure is (PPh3)2(CO)Rh-Rh(CO)(PPh3)2. But only mononuclear rhodium complexes were found on the activated SLPC and its suggested structure is HRh(CO)2(PPh3)2 and/or Rh(CO)2(PPh3)3. XRD spectra of the SLPCs were also discussed in this paper.