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

摘要

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 10-40 wt% Cu content and molar ratio of (Cu + Mg)/Al = 1-4 were prepared. The catalysts were characterized by ICP, N-2 physical adsorption, XRD, TEM, H-2-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 5 nm depending on the chemical compositions. The WGS activity of the Cu catalysts increased with the increase of Cu-0 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. (C) 2016 Published by Elsevier Ltd.