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Nature. 2016 Mar 3;531(7592):83-7. doi: 10.1038/nature16935. Epub 2016 Feb 15.

Stable amorphous georgeite as a precursor to a high-activity catalyst.

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Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK.
The UK Catalysis Hub, Research Complex at Harwell, Harwell, Oxon OX11 0FA, UK.
Kathleen Lonsdale Building, Department of Chemistry, University College London, Gordon Street, London WC1H 0AJ, UK.
Diamond Light Source, Didcot OX11 0DE, UK.
Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, UK.
Center for Electron Nanoscopy, Technical University of Denmark, Fysikvej 307, DK-2800 Kgs Lyngby, Denmark.
Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, Pennsylvania 18015, USA.
Johnson Matthey, PO Box 1, Belasis Avenue, Cleveland TS23 1LB, UK.


Copper and zinc form an important group of hydroxycarbonate minerals that include zincian malachite, aurichalcite, rosasite and the exceptionally rare and unstable--and hence little known and largely ignored--georgeite. The first three of these minerals are widely used as catalyst precursors for the industrially important methanol-synthesis and low-temperature water-gas shift (LTS) reactions, with the choice of precursor phase strongly influencing the activity of the final catalyst. The preferred phase is usually zincian malachite. This is prepared by a co-precipitation method that involves the transient formation of georgeite; with few exceptions it uses sodium carbonate as the carbonate source, but this also introduces sodium ions--a potential catalyst poison. Here we show that supercritical antisolvent (SAS) precipitation using carbon dioxide (refs 13, 14), a process that exploits the high diffusion rates and solvation power of supercritical carbon dioxide to rapidly expand and supersaturate solutions, can be used to prepare copper/zinc hydroxycarbonate precursors with low sodium content. These include stable georgeite, which we find to be a precursor to highly active methanol-synthesis and superior LTS catalysts. Our findings highlight the value of advanced synthesis methods in accessing unusual mineral phases, and show that there is room for exploring improvements to established industrial catalysts.


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