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The genesis of the active phase in Raney-type catalysts: the role of leaching parameters
The morphology and microstructure of two commercial 50–50 wt.% nickel aluminium alloys (A and B) have been studied. As expected from the phase diagram, NiAl 3, Ni 2Al 3 and a small amount of metallic aluminium were observed. The distribution of the two main phases consists of a core of Ni 2Al 3 with...
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Published in: | Applied catalysis. A, General General, 2003-05, Vol.244 (2), p.291-300 |
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Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The morphology and microstructure of two commercial 50–50
wt.% nickel aluminium alloys (A and B) have been studied. As expected from the phase diagram, NiAl
3, Ni
2Al
3 and a small amount of metallic aluminium were observed. The distribution of the two main phases consists of a core of Ni
2Al
3 with a shell of NiAl
3. Even if the composition of the starting alloys was the same, the amounts of the different phases are different: more Ni
2Al
3 and less metallic aluminium were present in alloy B. Treatment with an aqueous sodium hydroxide solution (leaching process) leads to Raney-type nickel catalyst. Different leaching times were used in order to follow an evolution in the morphology of the catalysts. The activation process is very fast and after 10
s of leaching, most of the aluminium has been leached out and is present as alumina. The longer the leaching time, the better the catalytic performance (both activity and selectivity) of the catalysts. This evolution of catalytic performance as function of time is much more pronounced in the case of catalysts issued from alloy A. |
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ISSN: | 0926-860X 1873-3875 |
DOI: | 10.1016/S0926-860X(02)00601-4 |