Characterising catalyst preparation : from adsorbed precursor complex to catalyst particle

摘要

Catalyst performance can be enhanced by the high dispersion of precious metals onto supports. The deposition of metal particles and the structural arrangement they adopt once impregnated on a support is therefore of interest in determining the necessary conditions required for maximum catalyst efficiency. The details of the relationship between precursor and the final catalyst structure have not been extensively investigated; therefore it is the aim of this project to examine this relationship using techniques such as EXAFS, XRD and TEM. A selection of Pt and Pd precursors has been deposited onto both Al2O3 and SiO2 supports and the resulting materials examined using these characterisation methods. Bimetallic combinations of these precursors have also been prepared and characterised. The EXAFS showed that the ligand stays intact during adsorption onto the support and that it is lost during heating. The type of support used had an effect on the dispersion of both the monometallic and bimetallic catalysts and also on the type of bimetallic particle formed. Al2O3 supported bimetallic particles consisted of a Pt rich core with a Pd outer shell whilst SiO2 supported bimetallic particles were made up of a mixture of monometallic Pt and Pd particles and bimetallic Pt/Pd particles.