Low-Temperature Synthesis of Porous Praseodymium Oxysulfate Oxygen Storage Materials by Using a CTA Template

Abstract

Porous praseodymium oxysulfate, Pr2O2SO4, with a large oxygen storage capacity was prepared from precipitates, which were formed by adding (NH4)2SO4 to a mixed aqueous solution of Pr(NO3)3 and cationic surfactant, CTA (cetyltrimethyl ammonium ion). Heating the precipitate, Pr-SO4-CTA, yielded directly the single phase of Pr2O2SO4 at a low temperature of 300°C, compared to ≥800°C required for the decomposition of Pr2(SO4)3 (Pr-SO4), and compared to ≥500°C required for the mesophase of Pr and dodecyl sulfate (Pr-DS) in our previous study.1) The effect of preparation route on microstructure and oxygen release/storage property of Pr2O2SO4 was studied by using XRD, TG, SEM, N2 adsorption and catalytic reaction. In contrast to the macropores (≥30 nm in size, 8 m2g-1) of Pr-SO4 and mesopores (≤10 nm, 28 m2 g-1) of Pr-DS, Pr-SO4-CTA showed a wide pore size distribution in the range 2-40 nm and a larger surface area of 37 m2 g-1. The porous structure is very effective in increasing the rate of oxygen release as well as storage. The anaerobic CO oxidation of 1 mass% Pd-loaded Pr2O2SO4 was evaluated in CO/O2 cycled feed stream reactions. It was found that the catalyst prepared from Pr-SO4-CTA achieved the highest catalytic activity due to the high porosity and specific surface area.