Issue 43, 2012

In situ EDXRD study of the chemistry of aging of co-precipitated mixed Cu,Zn hydroxycarbonates – consequences for the preparation of Cu/ZnO catalysts

Abstract

In order to better understand the critical influence of the synthesis parameters during preparation of Cu/ZnO catalysts at the early stages of preparation, the aging process of mixed Cu,Zn hydroxide carbonate precursors was decoupled from the precipitation and studied independently under different conditions, i.e. variations in pH, temperature and additives, using in situ energy-dispersive XRD and in situ UV-Vis spectroscopy. Crystalline zincian malachite, the relevant precursor phase for industrial catalysts, was formed from the amorphous starting material in all experiments under controlled conditions by aging in solutions of similar composition to the mother liquor. The efficient incorporation of Zn into zincian malachite can be seen as the key to Cu/ZnO catalyst synthesis. Two pathways were observed: direct co-condensation of Cu2+ and Zn2+ into Zn-rich malachite at 5 ≥ pH ≥ 6.5, or simultaneous initial crystallization of Cu-rich malachite and a transient Zn-storage phase. This intermediate re-dissolved and allowed for enrichment of Zn into malachite at pH ≥ 7 at later stages of solid formation. The former mechanism generally yielded a higher Zn-incorporation. On the basis of these results, the effects of synthesis parameters like temperature and acidity are discussed and their effects on the final Cu/ZnO catalyst can be rationalized.

Graphical abstract: In situ EDXRD study of the chemistry of aging of co-precipitated mixed Cu,Zn hydroxycarbonates – consequences for the preparation of Cu/ZnO catalysts

Supplementary files

Article information

Article type
Paper
Submitted
08 Jun 2012
Accepted
28 Aug 2012
First published
31 Aug 2012

Dalton Trans., 2012,41, 13413-13422

In situ EDXRD study of the chemistry of aging of co-precipitated mixed Cu,Zn hydroxycarbonates – consequences for the preparation of Cu/ZnO catalysts

S. Zander, B. Seidlhofer and M. Behrens, Dalton Trans., 2012, 41, 13413 DOI: 10.1039/C2DT31236K

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