Layered double hydroxides as precursors of Cu catalysts for hydrogen production by water-gas shift reaction

Various Cu catalysts were prepared by the calcination and reduction of Cu-containing layered double hydroxides (LDHs) including Cu-Al LDHs, Cu-Mg-Al LDHs, Cu-Zn-Al LDHs, and Cu-Zn-Cr LDHs. The catalysts were characterized by using ICP, N2 physisorption, TG, SEM, XRD, H2-TPR, and N2O chemisorption, and tested for the water-gas shift (WGS) reaction at 453-623 K. The characterization results reveal the formation of LDHs on the as-synthesized precursors. Upon calcination and reduction, highly dispersed Cu nanoparticles, particularly for Cu/MgO/Al2O3, were formed. The Cu0 surface area and Cu dispersion was found to be Cu/MgO/Al2O3 > Cu/Al2O3 > Cu/ZnO/Al2O3 > Cu/ZnO/Cr2O3. The activity of the LDHs-derived Cu catalysts for WGS decreased in the order of Cu/MgO/Al2O3 ∼ Cu/ZnO/Al2O3 > Cu/ZnO/Cr2O3 > Cu/Al2O3. The high activity of Cu/MgO/Al2O3 was attributed to its high Cu0 surface area and Cu dispersion, while the interaction between metallic Cu and ZnO on Cu/ZnO/Al2O3 might be responsible for the WGS activity. Interestingly, the highly dispersed Cu metal particles on the Cu/MgO/Al2O3 catalyst seemed stable during the WGS reaction.