| Autor: |
D. S. Brands, Christian Oude Luttikhuis, Bart van der Linden, E.K. Poels, L.H. Staal, Frank Th. van de Scheur |
| Přispěvatelé: |
HIMS (FNWI) |
| Rok vydání: |
1994 |
| Předmět: |
|
| Zdroj: |
Applied Catalysis A-General, 116, 237-257. Elsevier |
| ISSN: |
0926-860X |
| DOI: |
10.1016/0926-860x(94)80292-0 |
| Popis: |
For silica-supported copper-zinc catalysts, a fivefold enhancement of the activity in the hydrogenolysis of methyl acetate has been obtained by high-temperature reductions in the range between 550 K and 700 K. Furthermore, simultaneously, the selectivity was significantly improved. At equal conversion of methyl acetate, catalysts reduced at high temperature make less side products than catalysts reduced at low temperature. The selectivities to methane and ethane as a function of the reduction temperature indicate that these side products are formed on copper metal sites. The formation of ethene most likely proceeds by dehydration of ethanol on acid sites. The presence of copper crystallites in the range of 3–5 nm and the absence of crystalline zinc oxide were established by X-ray diffraction. The activity increase is ascribed to the formation of additional highly active copper sites in interaction with the zinc-containing phase. Fourier-transform infrared spectroscopy of adsorbed carbon monoxide confirmed that metallic copper is more important in the activity than oxidized copper. Reduction at 750 K results in brass formation and catalyst deactivation by evaporation of zinc. The enhanced catalyst activity can be preserved by passivation and is therefore relevant to practical applications. After passivation and prolonged exposure to air the original high activity can be restored by low-temperature reduction. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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