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 Cu-0 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.