Sulfur resistant LaxCe1−xNi0.5Cu0.5O3 catalysts for an ultra-high temperature water gas shift reaction

Abstract

A series of La_xCe_1−xNi_0.5Cu_0.5O₃ catalysts was synthesized to study the effect of Ce substitution for La. XRD results show that only a small amount of Ce (10%) is allowable to substitute La to maintain the perovskite structure. The La_0.9Ce_0.1Ni_0.5Cu_0.5O₃ catalyst has the smallest metal particle size and the highest oxygen mobility among all tested catalysts as observed from the XRD, TPD-O₂, and XPS results of reduced catalysts. These two factors are very important in achieving the highest catalytic activity of the La_0.9Ce_0.1Ni_0.5Cu_0.5O₃ catalyst in a water gas shift reaction at 450–650 °C. In the presence of H₂S, the catalytic activity at lower temperature was suppressed due to the formation of stable SO₄²⁻ species on the metal. However, since the amounts of surface oxygen species and adsorbed H₂S are much lower at high temperature, the formation of SO₄²⁻ species is not observed, resulting in higher catalytic activity. The presence of H₂S at high temperature enhances the formation of formate species, which can decompose to produce methane as the side product of the water gas shift reaction.