TPD characterization of surface adsorption sites of model Ziegler–Natta polymerization catalysts

The surface adsorption sites of titanium chloride films that can be used as model Ziegler–Natta polymerization catalysts have been investigated with temperature-programmed desorption TPD.of various probe molecules. The adsorption sites can be differentiated depending on the heat of desorption of the molecule. Two titanium chloride films were produced by electron-induced chemical vapor deposition of TiCl4and co-deposition of Mg and TiCl4on gold substrates. The surfaces of both films were chlorine-terminated. 1,3,5-Trimethylbenzene mesitylene.was found to be an effective and non-destructive molecule for TPD characterization of adsorption sites on the model catalysts. The film produced by the electron-induced chemical vapor deposition had a distribution of adsorption sites that were not thermodynamically stable and subject to high-temperature annealing, while the film prepared by the co-deposition had a stable surface structure that was composed of domains of the MgCl2 001.basal plane structure. q2000 Elsevier Science B.V. All rights reserved.