Enhancing catalytic activity of lanthanide oxysulfate (La2O2SO4/Pr2O2SO4) via facile manipulation of nanoscale catalyst synthesis process and reactor configuration

Abstract

We recently reported that a facile colloidal synthesis approach can be used to synthesize nanoscale Eu2O2S to significantly enhance activity of rare-earth based catalysts. While extending this method to synthesize other coordinated lanthanide complexes (La and Pr), we discovered that mixed phases of lanthanide monosulfide (LnS) and lanthanide oxysulfate (Ln2O2SO4) (Ln=La, Pr) co-existed in the product, instead of the desired single-phase complex. Utilizing the high oxophilicity of sulfur and Ln elements, we successfully converted LnS impurity to Ln2O2SO4 nanoparticles with unique morphologies by simply heating them in air. By impregnating the resultant nanocatalysts onto a commercial tubular oxide support (referred to as CCR), CO conversion of nanoscale La2O2SO4 for high temperature water-gas-shift (HTS) reaction increased from nearly zero in fixed-bed reactor (FBR) to 35% in CCR module at 500°C. Reactivity comparison among different catalyst size, morphology and type suggests that the enhanced catalytic activity of La2O2SO4/Pr2O2SO4 nanocatalysts in CCR derives from the increased surface area and minimized aggregation.