Abstract
A series of Pt-exchanged molecular sieves was studied by X-ray absorption spectroscopy (XANES and EXAFS) in order to probe the effect of the structural and chemical characteristics of selected molecular sieves on the Pt particles. For each molecular sieve (LTL, MOR, and AFI) different preparation procedures (ion exchange, wet impregnation and vapor phase impregnation) were applied. For a particular molecular sieve the particle size increased in the order, ion exchange<vapor impregnation<wet impregnation. The hydrogen chemisorbed per Pt increases linearly with the fraction of Pt exposed as calculated from EXAFS analysis indicating that on the average one hydrogen atom is adsorbed per Pt on dense oxide supports, while Pt in acidic and neutral molecular sieves show an ≈25% lower value. For a given dispersion of Pt the amount of sorbed hydrogen per Pt is systematically lower for Pt supported on acid and neutral molecular sieves than for Pt supported on dense oxides. For Pt in alkali exchanged LTL, the results suggest that two hydrogen atoms are adsorbed per accessible Pt.
| Original language | Undefined |
|---|---|
| Pages (from-to) | 155-162 |
| Number of pages | 13 |
| Journal | Applied catalysis A: general |
| Volume | 174 |
| Issue number | 194 |
| DOIs | |
| Publication status | Published - 1998 |
Keywords
- METIS-105556
- IR-73633
- Ion exchange
- Impregnation
- Hydrogen chemisorption
- EXAFS
- Vapour impregnation
- Pt/Zeolites