Magnesium-aluminum mixed metal oxide supported copper nanoparticles as catalysts for water-gas shift reaction

Abstract

Mg(Al)O mixed metal oxide (MMO) supported Cu nanoparticles catalysts have been prepared by calcination and reduction of Cu-Mg-Al layered double hydroxides (LDHs). By adjusting the chemical compositions of LDHs precursors, various catalysts with 10–40wt% Cu content and molar ratio of (Cu+Mg)/Al=1–4 were prepared. The catalysts were characterized by ICP, N2 physical adsorption, XRD, TEM, H2-TPR, and N2O chemisorption, and tested for the water-gas shift (WGS) reaction. The characterization results suggested that upon calcination Cu-Mg-Al LDHs were converted to Mg(Cu, Al)O MMOs, where both Cu2+ and Al3+ were incorporated into the MgO framework to form a solid solution; reduction of Mg(Cu, Al)O gave highly dispersed and uniform Cu metal nanoparticles. The Cu metal dispersion was as high as 22–78% and the particle size varied from 1.5 to 5nm depending on the chemical compositions. The WGS activity of the Cu catalysts increased with the increase of Cu0 surface area. Among the prepared catalysts, the 30%Cu/Mg2Al catalyst exhibited the highest Cu surface area and the highest WGS activity. The optimized catalyst also showed superior activity, thermal stability, and steady-state stability than a commercial Cu/ZnO/Al2O3 catalyst under the present reaction conditions. The characterization on the spent catalysts showed that the LDHs-derived Cu nanoparticles remained highly dispersed, suggesting that the Mg(Al)O supported Cu nanoparticles were stable and possessed good resistance against sintering.