Oriented Isomorphous Substitution: An Efficient and Alternative Route to Fabricate the Zn Rich Phase Pure (Cu_1−x,Zn_x)₂(OH)₂CO₃ Precursor Catalyst for Methanol Synthesis

Abstract

A new methodology has been demonstrated for the synthesis of a series of phase pure (Cu1−x,Znx)2(OH)2CO3 precursors by isomorphous substitution of Zn2+ in the malachite structure. By following the present protocol, it was possible to synthesize the pure phase (Cu1−x,Znx)2(OH)2CO3 with substitution level as high as x=0.5, which is better than the maximum possible value achieved by coprecipitation method, i. e. x=0.31. The isomorphous substitution by Zn2+ leads to the change in the morphology of malachite crystals from flake‐like to regular needle‐like shape with high Zn dispersion. The activity of the calcined catalysts was increased by ∼1.5–1.7 fold for the hydrogenation of syngas to methanol as compared with those prepared from the traditional coprecipitation route. The synergy between Cu and ZnO was further demonstrated quantitatively by characterization of the catalysts treated with syngas at 250 °C.

Isomorphous substitution method to fabricating pure phase Al‐doped zinc malachite: defects driven promotion improvement and enhanced synergy between Cu−ZnO

“…The synthesis of Zn doped malachite was carried out by isomorphous substitution (IS) method as described in our previous publication. [48] The filtered and washed malachite was mixed with 100 mL deionised water and kept at constant temperature bath (60°C). According to the molar ratio of Zn/Cu = 45 : 100, the 0.05 M solution of Zn(NO 3 ) 2 × 6H 2 O was rapidly added to the slurry using peristaltic pump, and aged for 1.5 h with constant stirring.…”

“…Synthesis of zM, (Cu,Zn) 2 (OH) 2 CO 3 . The synthesis of Zn doped malachite was carried out by isomorphous substitution (IS) method as described in our previous publication [48] . The filtered and washed malachite was mixed with 100 mL deionised water and kept at constant temperature bath (60 °C).…”

Design of Cu/ZnO/Al2O3catalysts with a rich Cu–ZnO interface for enhanced CO2hydrogenation to methanol using zinc-malachite as the precursor

“…Recently, it was found that when the Cu/ZnO/Al 2 O 3 catalyst was prepared using a co-precipitation method, the precipitates formed mainly included zinc-malachite, aurichalcite and layered double hydroxides. [17][18][19][20][21] Catalysts derived from zinc-malachite often have excellent performance. By adjusting the pH value, Gao W et al prepared Cu-ZnO-ZrO 2 catalysts with aurichalcite and zinc-malachite as precursors, and found that the catalyst derived from zinc-malachite had an excellent catalytic performance for methanol synthesis.…”

“…25 The existence of single CuO and ZnO is inhibited after the calcination of the precursor, which promotes the formation of Cu-ZnO interfaces. 21 Hence, the use of zinc-malachite as the precursor to construct Cu/ZnO/Al 2 O 3 catalysts with rich Cu-ZnO interfaces is promising. As far as we know, the current research mainly focuses on the Cu/ ZnO/Al 2 O 3 catalysts prepared by adjusting the zinc substitution amount of zinc-malachite.…”

“…When zinc-malachite is used as the precursor, Cu 2+ and Zn 2+ are more uniformly dispersed at the atomic level with the increase of zinc substitution amount in zinc-malachite. 21 Due to the chemical memory effect, the arrangement of Cu and Zn atoms defined by the zinc-malachite lattice will be retained in the calcination process. 25 The existence of single CuO and ZnO is inhibited after the calcination of the precursor, which promotes the formation of Cu–ZnO interfaces.…”