Abstract
Two Pd/Al2O3 catalysts of different loadings and dispersions were modified by the addition of various amounts of Bi and studied in the hydrogenation of 1-hexyne and 2-hexyne and in the consecutive reactions of the products formed. Catalyst behaviour was compared with a commercial Lindlar catalyst and Pb-free Pd/CaCO3. Results are consistent with a preference of Bi to occupy step and edge sites while leaving the terraces and extended facets relatively unaffected. Results show that while Bi had little effect on the rate of the 1-hexyne hydrogenation, the rate of subsequent reactions of the 1-hexene formed were suppressed. In this context, Bi was a more effective modifier than Pb. This situation was reversed when reactions were performed using 2-hexyne. Results are discussed in terms of the reaction mechanism and key intermediates in the process and the roles of bismuth, relative to lead, in creating an appropriate ensemble of surface Pd atoms to permit control of selectivity. (C) 2008 Elsevier Inc. All rights reserved.
| Original language | English |
|---|---|
| Pages (from-to) | 208-216 |
| Number of pages | 9 |
| Journal | Journal of Catalysis |
| Volume | 261 |
| Issue number | 2 |
| Early online date | 17 Dec 2008 |
| DOIs | |
| Publication status | Published - 25 Jan 2009 |
Bibliographical note
We acknowledge fruitful discussions with Professors G.A. Attard and P.B. Wells, University of Cardiff and thank the College of Physical Sciences, University of Aberdeen for providing a research studentship (to J.M.). We thank Johnson Matthey for providing the Pd salt employed in catalyst preparation and for the gift of the Varian 3400 GC.Keywords
- Selective hydrogenation
- Hexyne
- Bi modified Pd catalyst
- liquid-phase oxidation
- selective hydrogenation
- alkyne hydrogenation
- co oxidation
- size
- platinum
- PD/AL2O3
- behavior
- alumina
- surface