Cu substituted ZnAl_2O_4 ex-LDH catalysts for medium-temperature WGS - effect of Cu/Zn ratio and thermal treatment on catalyst efficiency

摘要

The effect of Cu/Zn ratio of ex-LDH oxide-based catalysts for medium-temperature water-gas shift reaction (MT-WGS) was investigated. A series of CuZnAl-LDH precursors with different Cu/Zn molar ratio were synthesized by co-precipitation and oxide (Zn,Cu)(x)Al2O4 catalysts were prepared via subsequent calcinations at 380 degrees C or 700 degrees C. The prepared materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetry with evolved gas analysis (TG/DTG/EGA), N-2 adsorption, N2O chemisorption and temperature-programmed reduction (H-2-TPR). MT-WGS activity evaluation was carried out on the basis of measurements made in a differential reactor in kinetic regime. Catalysts' properties were investigated and effect of composition (Cu/Zn molar ratio) and the calcination temperature of CuZnAl-LDH precursors on structural transformation, active surface area and MT-WGS rate constant was shown. The highest activity of (Zn,Cu)(x)Al2O4 catalyst with Cu/Zn molar ratio of 1.5 calcined at mild conditions was attributed to easy reducible and accessible Cu surface. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.