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The reduction of copper in porous matrices

Author
Bandyopadhyay, M
Grunert, W
Yu, X
Grabowski, S
Gies, H
Tkachenko, OP
Klementiev, KV
Koc, N
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Abstract
The reduction of copper oxide species dispersed in microporous and mesoporous matrices has been studied by TPR, XPS/XAES, and XAFS. While the reduction of bulk CuO and of Cu(II) in mesoporous MCM-48 (5.6 wt-%) proceeded in one step without intermediate Cu(I) being detectable under the experimental conditions, Cu(II) in microporous matrices was reduced ill two steps. The two-step scheme cannot be identified with the reduction steps Cu(II) -> Cu(I) and CL(I) -> CU(0). Instead, highly disperse Cu(0) may be present already after the first reduction step. In siliceous matrices, coexistence of Cu(0), and Cu ions was observed over a wide temperature range, obviously due to the absence of ail autocatalytic reduction process. The latter occurred in Cu-ZSM-5, apparently involving simultaneous segregation of Cu metal from the matrix. This suggests that very small (oligorneric) Cu metal Clusters are unable to activate hydrogen. The reduction behaviour of Cu in Y zeolite depends critically on the thermal history of the sample due to the population of hidden sites by copper upon calcination. Highly disperse Cu particles are stable in MCM-48 up to 500 degrees C.
URI
http://hdl.handle.net/20.500.12627/122563
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Creative Commons Lisansı

İstanbul Üniversitesi Akademik Arşiv Sistemi (ilgili içerikte aksi belirtilmediği sürece) Creative Commons Alıntı-GayriTicari-Türetilemez 4.0 Uluslararası Lisansı ile lisanslanmıştır.

DSpace software copyright © 2002-2016  DuraSpace
Contact Us | Send Feedback
Theme by 
Atmire NV