Preparation of Cu/ZnO/Al₂O₃ catalyst by intercalated hydrotalcite precursor and its catalytic performance in methanol synthesis

The \rmCu(\rmC_\rm2\rmO_\rm4\rm)_2^2 - complexed anion intercalated ZnAl-LDH hydrotalcite pure phase precursors were prepared by co-precipitation, ion exchange and calcination-reconstruction methods; after that, the Cu-ZnAl-LDO catalysts with lamellar structure were obtained by calcination of the precursors. The precursors and catalysts were characterized by XRD, TEM, ICP, H₂-TPR, N₂O-H₂ TPD titrations and N₂ physisorption; the effect of preparation method on the confinement degree of intercalated active Cu species and the catalytic activity and stability of Cu-ZnAl-LDO in methanol synthesis was investigated. The results indicate that compared with the ion exchange and calcination-reconstruction methods, the CP-Cu-ZnAl-LDO catalyst prepared by co-precipitation method has a higher interlayer Cu content as well as a stronger confinement effect of layer plate on the Cu species. In addition, the unique ordered layered structure of hydrotalcite can also improve the dispersion of active Cu species between the layers and inhibit the sintering of Cu particles. As a result, the CP-Cu-ZnAl-LDO catalyst prepared by co-precipitation method exhibits excellent performance in methanol synthesis; the space-time yield of methanol reaches 3412 mg/(g_Cu·h) and basically no deactivation is observed after continuous reaction for 60 h.