Showing papers by "Francis Verpoort published in 1997"
TL;DR: In this paper, the surface properties of the powder catalysts and a model catalyst have been determined by conventional XPS and Angle-Resolved XPS (AR-XPS), and the catalytic activity was related to the structure of the molecular entities on the surface of the precursor.
Abstract: Heterogeneous catalysts with respect to the metathesis of olefins has been prepared by a controlled thermal reaction between W(O-2,6-C 6 H 3 X 2 ) 2 Cl 4 (X = t-Bu, Me, Br, and Cl) or W(MBPD)Cl 4 and a silica support. Surface characteristics of the powder catalysts and a model catalyst have been determined by conventional XPS and Angle-Resolved XPS (AR-XPS). The catalytic activity has been related to the structure of the molecular entities on the surface of the precursor. Furthermore, a model for hydroxylated silica is described. The surface structure ( ? SiO)2W(O-2,6-C 6 H 3 X 2 ) 2 Cl 2 is modeled to determine the preferred arrangement of the tungsten diphenoxide species on the hydroxylated support.
17 citations
TL;DR: In this paper, the Varimax Promax transformation (VPT) technique for maximum likelihood common factor analysis (MLCFA) has been proposed as an alternative method to the traditional transformations.
Abstract: Model supports consisting of a thin layer of SiO2 on a silicon single crystal offer tremendous advantages for the study of heterogeneous catalysts. Using model supports, the use of angle-resolved and depth profiling X-ray photoelectron spectroscopy has now become meaningful. The Varimax Promax transformation (VPT) technique for maximum likelihood common factor analysis (MLCFA) has been proposed as an alternative method to the traditional transformations. The so-called VPT technique makes no use of spectral reference libraries. Both MLCFA and VPT are incorporated in a factor analysis software package which has been applied, in combination with XPS and AES, to the study of thin layers of SiO2 on Si(100).
12 citations
TL;DR: In this article, a catalyst precursor has been synthesized by modifying the silica surface with ClPPh2 followed by a surface reaction with RuCl3, where Sup- ports consisting of a thin layer of SiO2 on a silicon single crystal have been used.
Abstract: The catalyst precursor has been synthesized by modifying the silica surface with ClPPh2 followed by a surface reaction with RuCl3. Sup- ports consisting of a thin layer of SiO2 on a silicon single crystal have been used. Characterization of the different stages in the reaction procedure has been performed by a combination of conventional and angle-resolved X-ray photoelectron spectroscopy (XPS) using RuCl3/P(C6H5)2/SiO2/Si(100) model precursors. Different types of ruthenium centra have been identified.
2 citations