| Popis: |
After calcination of ion exchanged Pd/Nay at 500°C, the Pd 2+ ions have lost their ligands and are located in sodalite cages, but after calcination at 250° Pd(NHY 3 ) 2+2 ions are present in supercages. Reduction leads to Pd atoms in sodalite cages or to Pd particles in supercages. An important difference between these cases is due to the co-product of hydrogen reduction: NH 4 + ions or protons. Probing these catalysts with the conversion of neopentane shows that Pd particle morphology has only a minor influence on the rate of conversion, but the presence of protons has a marked effect, increasing the activity per site by two orders of magnitude. This result is tentatively ascribed to electron deficient [Pd n -H x ] x+ clusters as superactive sites. |
Plný text