IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Thursday Sessions
       Session SS1-ThP

Paper SS1-ThP8
Combustion of Hydrogen Over a Palladium Catalyst Studied with Laser Induced Fluorescence Imaging

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Catalysis on Model Systems Poster Session
Presenter: A. Johansson, Goteborg University and Chalmers University of Technology, Sweden
Authors: A. Johansson, Goteborg University and Chalmers University of Technology, Sweden
M. Forsth, Goteborg University and Chalmers University of Technology, Sweden
A. Rosen, Goteborg University and Chalmers University of Technology, Sweden
Correspondent: Click to Email
Catalysis is of great fundamental, practical and economical interest in today's society. Noble metals, such as palladium, is widely used as heterogeneous catalysts for reduction of emissions of car exhausts. It is therefore important to study the catalytic property of this metal. Combustion of hydrogen with oxygen was chosen as a model system to make it as simple as possible, avoiding hydrocarbons. The oxygen and hydrogen molecules adsorb and react via reaction intermediates to form water. An important intermediate is the OH molecule. The hydroxyl radical OH also has spectroscopic properties which make it convenient to study. Laser Induced Fluorescence (LIF) was used to investigate the gas-phase concentration of the OH molecule. An ICCD camera was used as detector to study the OH concentration profile in two dimensions outside the palladium surface. The polycrystalline palladium foil was resistively heated up to 1300K and nearby temperatures. The chamber was evacuated with roots and turbo pumps. The hydrogen and oxygen gas flow was regulated with two mass flow controllers, one for each gas. The mass flow controllers were calibrated with a quadropole mass spectrometer connected to the chamber. The working pressure in the chamber was varied from 0.1-100 Torr. The hydrogen/oxygen reaction on a hot palladium surface was also modelled using the Chemkin software package. Estimations of important reaction parameters could be achieved by comparing experimentally obtained OH-profiles with modelled profiles. Also, sensitivity analysis of the obtained model indicated which reactions that are rate-limiting and which reactions that are less important from a catalytic point-of-view. These last results should be taken as advises as to where future experimental efforts should be made. The water production rate is measured with micro calorimetry.