Towards ‘greener’ catalyst manufacture: Reduction of wastewater from the preparation of Cu/ZnO/Al2O3 methanol synthesis catalysts

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

“…However, Cu deficient precursors with Cu : Zn molar ratios of 1.8 : 1 were achieved when using ammonium based reagents. This has also been reported in related studies, 37,38 whereby loss of metal is attributed to a leaching effect, caused by simultaneous formation of a blue copper–amine complex within the mother liquor. To get an estimate of the amount of metal lost from leaching, the resulting blue effluents were collected and analysed by MP-AES (Table 1).…”

“…A contributing factor to the differing impurity contents of these hydroxycarbonates was due to the reagents used in the preparations. Residual nitrates and alkali cations have been reported as catalyst poisons 14,37–40 so MP-AES analysis was used to determine the effect of both the precipitant and the washing procedure directly after co-precipitation on the amount of residual Na + (Table 3). Our findings show that residual Na + is present in all the materials even when Na 2 CO 3 is avoided in the preparation.…”

“…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. 14,37,38 …”

The effect of sodium species on methanol synthesis and water–gas shift Cu/ZnO catalysts: utilising high purity zincian georgeite

“…The presence of sodium nitrate within these zincian malachite precursors resulted in the evolution of NO x species during the calcination step, which caused CuO and ZnO crystal growth. 20,22 De Jongh and co-workers also showed that even when a Na + -free preparation method (using ammonium carbonate instead of sodium carbonate) was used, residual species resulted in CuO crystallite growth during calcination (unless a specic calcination environment is used). 22 Their observation of similar CuO crystallisation with sodium nitrate or ammonium nitrate residue indicates that the effect of Na + on catalyst performance was being masked by residual nitrate species decomposition.…”

Highly active Cu/ZnO–Al catalyst for methanol synthesis: effect of aging on its structure and activity

“…In this way new insights can be added to the known detrimental effect of Na + ions on the catalytic performance. 24,25 Domain sizes of the zincian-malachite phase on CZA precipitates calculated using the Scherrer equation applied to the (020) reection (Table 1) do not vary during aging. Only the position of the (20À1) reection of the malachite slightly shied to higher angles when the precursors were aged.…”