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

A new class of Cu/ZnO catalysts derived from zincian georgeite precursors prepared by co-precipitation

“…15 This is in agreement with our previous findings that zincian georgeite has a higher (CO 3 ) : (Cu + Zn) ratio than mixed zincian malachite/aurichalcite materials. 36 We also found that when Zn was excluded from the preparations, the georgeite formed rapidly aged into malachite, even when attempts were made to instantly isolate and dry the precipitate. Hence the presence of Zn enhances the stability of the resulting georgeite phase, and this also supresses the transformation into crystalline phases, 15 albeit only at very mild conditions.…”

“…In our previous studies on zincian georgeite materials prepared by the SAS method, 36 scanning transmission electron microscopy (STEM) revealed that the zincian georgeite was not completely amorphous. In fact, the amorphous matrix, which contains carbonate and hydroxyl species, also had approximately 10 vol% fraction of sub-2 nm crystalline CuO and Cu 2 O particles that were below the detection limit of the X-ray based characterization techniques employed.…”

“…The spectra of the materials prepared at 40 °C using metal acetates, regardless of the precipitant, can be assigned to zincian georgeite. 14,36 The broad band centred at 3419 cm –1 is associated with the O–H stretch, whilst carbonate peaks are present as the intense doublet at 1475 and 1408 cm –1 for the ν 3 asymmetric stretch, the weakly visible peak at 1049 cm –1 for the ν 1 symmetric stretch and at 836 cm –1 for the ν 2 bending mode. As expected, XRD showed no discernible reflections for these samples, as zincian georgeite is known to be amorphous (Fig.…”

“…2). A comparison was made against supercritical CO 2 anti-solvent (SAS) precipitated zincian georgeite, previously reported, 36 as well as a simulated PDF of zincian malachite. The PDFs of the SAS and co-precipitated zincian georgeite samples are similar, albeit with slightly more order obtained from using the co-precipitation route.…”

“…32–35 We have recently shown that disordered zincian georgeite can be readily synthesised using a specialised supercritical anti-solvent precipitation method, and this enables the preparation of a new class of Cu/ZnO catalysts which give catalytic performances that rival, or even exceed in some instances, those of catalysts prepared from crystalline hydroxycarbonates phases. 36 We have now extended this study and have prepared zincian georgeite by a more amenable co-precipitation method and tested its applicability as a catalyst precursor for methanol synthesis and the LTS reaction. To obtain zincian georgeite, the standard co-precipitation procedure was deliberately modified to avoid the utilisation of nitrates and Na + , which can lead to residual catalyst poisons being retained and crystalline malachite phases being formed.…”