Characterization and Catalytic Performance of Cu/ZnO/Al₂O₃ Water–Gas Shift Catalysts Derived from Cu–Zn–Al Layered Double Hydroxides

Cu/ZnO/Al₂O₃ catalysts with different compositions were prepared from Cu–Zn–Al layered double hydroxides (LDHs) and tested for the water–gas shift reaction. LDHs were synthesized by the coprecipitation method, and Cu–Zn–Al LDHs or Cu–Al LDHs could be formed depending on the (Cu + Zn)/Al atomic ratio. Upon calcination, LDHs decomposed to form mixed metal oxides consisting of CuO, ZnO, ZnAl₂O₄, CuAl₂O₄, and/or amorphous Al₂O₃. After reduction, well dispersed Cu metal particles with 18–48% dispersion and 2–6 nm size were formed. It was observed that the initial activity of Cu/ZnO/Al₂O₃ catalysts was proportional to the number of surface Cu⁰ atoms and the 30%Cu/Zn₁Al catalyst showed the highest activity. Moreover, this optimum catalyst exhibited better activity, thermal stability, and long-term stability than a commercial Cu/ZnO/Al₂O₃ catalyst. It was considered that a synergetic effect between Cu metal and ZnAl₂O₄ spinel might exist and play a key role for the high catalytic performance