SO42− immobilization regulated by reaction atmosphere over ABS poisoned α-Fe2O3 catalysts for efficient NOx removal

Abstract

SO42- immobilization is pivotal for boosting the catalytic performance of iron oxides in NH3-SCR. However, the critical issue related to sulfate species enrichment on α-Fe2O3 is still elusive. Herein, by employing ammonium bisulfate (ABS) as the source of SO42-, we conducted a detailed investigation on the effect of reaction atmospheres (NH3, NO + O2 and NH3 + NO + O2) on the immobilization of sulfate species and their consequence for ABS poisoned Fe2O3/SiO2 (ABS/FeSi) catalysts in NH3-SCR. Results showed sulfate group could be transferred from ABS to FeSi under thermal treatment and the efficiency actually exhibited an atmosphere-dependent feature. The promotion effect from NO/O2 was most prominent due to accelerated consumption of NH4+, whereas NH3 treatment retarded ABS pyrolysis, resulting in reduced sulfate immobilization on FeSi surface. Besides, an unexpected effect on Fe2O3 disintegration was exhibited by NH3, which was detrimental to activity enhancement due to disruption of electronic property. By correlating catalytic performance with adsorption feature, we propose the occurrence of reaction via E-R pathway over sulfated FeSi catalysts. The result of present study can enrich our understanding on the controlled sulfate immobilization for robust SCR denitration.