AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuM

Paper SS1-TuM1
Ethylene Polymerization on a CrOx/SiO2 Model Catalyst: XPS, SIMS, RBS and AFM

Tuesday, October 3, 2000, 8:20 am, Room 208

Session: Reactions on Oxides and Environmental Chemistry
Presenter: P.C. Thuene, Eindhoven University of Technology, The Netherlands
Authors: P.C. Thuene, Eindhoven University of Technology, The Netherlands
J. Loos, Eindhoven University of Technology, The Netherlands
J.W. Niemantsverdriet, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
Achieving realistic catalytic activity on a model catalyst consisting of Cr on 1 cm2 of planar SiO2 at a loading of 1 Cr per nm2 has proven to be the major challenge in designing a surface science model for the Phillips ethylene polymerization catalyst. Poisons like water or acetylene can deactivate the catalyst within a fraction of a second even if they are present in minute (1ppm) quantities. By using special filters we can now run polymerization reactions at 160°C for at least 30 minutes without deactivation of the catalyst. The polymer yield after each polymerization run is measured most conveniently by analyzing scalpel scratches with atomic force microscopy (AFM). The catalyst shows a constant activity with a pseudo turnover frequency of 2.5 C2H4 / Cr s. This corresponds to 250 g PE / gcat h atm if rescaled to the surface area of an industrial catalyst (286 m2/g, Crossfield) which represents a realistic catalytic activity. Owing to the planar geometry, the state of Cr can be determined in detail by using XPS and SIMS, while the polymer morphology can be analyzed with AFM.