Large-capacity oxygen storage of Pd-loaded Pr 2O 2SO 4 applied to anaerobic catalytic CO oxidation

Abstract

The oxygen release and storage properties of 1 wt% Pd-loaded Pr 2O 2SO 4 were studied using different cycled feed stream methods, namely a flow microbalance, in situ X-ray diffraction and anaerobic CO oxidation in a flow reactor. The redox between Pr 2O 2SO 4 and Pr 2O 2S exhibited a large oxygen storage of 2 (mol of O 2) mol −1 at high temperatures. Loading Pd can activate reducing gases (H 2/CO) so as to promote the oxygen release by the reduction of bulk Pr 2O 2SO 4 to Pr 2O 2S. In contrast, the oxygen storage by the reoxidation of Pr 2O 2S to Pr 2O 2SO 4 was much faster even in the absence of Pd, because the redox between Pr 3+ and Pr 4+ on the solid surface plays the role of a mediator. Pd species also formed active catalytic sites for an anaerobic CO oxidation, which consumed lattice oxygens released from Pr 2O 2SO 4. The full capacity oxygen storage of 2 (mol of O 2) mol −1 and anaerobic oxidation of 4 (mol of CO) mol −1 could be cycled. The CO/O 2 cycled feed stream reactions achieved CO conversion >85% at 700 °C, almost comparable to that of a steady-state CO-O 2 reaction. The catalytic activity was not affected by the presence of SO 2, which rather improved the stability of Pr 2O 2SO 4/Pr 2O 2S.