摘要
用HP5988A型色谱-质谱仪的多离子选择检测器和310工程计算机系统考察了PtCl_(2-)(PPh_3)_2,Pt-3(CO)_3(PPh_3)_4和Pt_4(CO)_5(PPh_3)_4等化合物在γ-Al_2O_3,TiO_2和SiO_2载体上的程序升温热分解特性。结果表明:铂簇合物在TPDE-H_2下的脱羰基过程比TPDE-He下简单。在TPDE-H_2下,在373K能检测到单一的CO_2脱附峰,三苯基膦配体在不同载体上的分解和脱附时,苯是主要脱附产物(≥90mol％);在TPDE-He下,三苯基膦配体的分解和脱附特性同载体性质明显有关。若以脱附苯的mol％为指标,则TiO_2>γ-Al_2O_3>SiO_2。另外,在两种情况下,三苯基膦配体的分解和脱附,均因铂的存在而加速。在脱附产物中,均未发现任何含磷化合物,证明磷在铂簇合物分解后还残留在催化剂上。
Temperature programmed decomposition of y-Al2O3 , TiO2(P-25) and SiO2 (aerosol 200 ) supported PtCl2(PPh3)2 , Pt3(CO)3(PPh3)4 and Pt4(CO)5--(PPh3)4was studied by using a mass spectrometer under He(TPDE-He) and/or H2(TPDE-H2). Decarbonylation of the supported Pt cluster either in TPDE-He or in TPDE-H2 mainly leads to the formation of CO2. The desorption spectra of CO2 observed in TPDE-H2 is simpler than that in TPDE-He and only a simple desorption peak of CO2 is detected at 373 K in the former case . The PPh3 ligands in different samples mainly decompose into benzene and biphenyl during TPDE-He and/or TPDE-H2. The decomposition of PPh3 is accelerated in the presence of Pt-containing compounds and Pt metallic particles. Depending on the nature of support and cluster used, the decomposition of the PPh3 carries out Step by Step. In general the mole percent of benzene in the decomposition and desorption products in TPDE-He is in the Sequence of TiO2>Al2O3>SiO2, while in TPDE-H2, the sequence is TiO2≈SiO2>Al2O3 . And in the case of TPDE-H2 the mole percent of benzene in the decomposition and desorption products is always higher than that in TPDE-He, it is Suggested that the PPh3 decomposes during TPDE into phenyl group which is adsorbed on the sulface, and then hydrogenated and deSorbed in the form of benzene, or dimerized and desorbed in the form of biphenyl . No any P-containing compounds are detected in TPDE-He or in TPDE-H2, P is remained on the catalyst after TPDE.
