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

[Display omitted] • The immobilization efficiency of sulfate species in ABS/FeSi catalyst exhibits a distinct atmosphere-dependent feature. • ABS/FeSi-NO displays the most remarkable activity enhancement due to the accelerated depletion of NH 4 +. • NH 3 treatment inhibits ABS decomposition and results in less SO 4 2- immobilization. • NH 3 treatment brings addition effect of α-Fe 2 O 3 disintegration, which was detrimental to activity enhancement. SO 4 2- immobilization is pivotal for boosting the catalytic performance of iron oxides in NH 3 -SCR. However, the critical issue related to sulfate species enrichment on α-Fe 2 O 3 is still elusive. Herein, by employing ammonium bisulfate (ABS) as the source of SO 4 2-, we conducted a detailed investigation on the effect of reaction atmospheres (NH 3 , NO + O 2 and NH 3 + NO + O 2) on the immobilization of sulfate species and their consequence for ABS poisoned Fe 2 O 3 /SiO 2 (ABS/FeSi) catalysts in NH 3 -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/O 2 was most prominent due to accelerated consumption of NH 4 +, whereas NH 3 treatment retarded ABS pyrolysis, resulting in reduced sulfate immobilization on FeSi surface. Besides, an unexpected effect on Fe 2 O 3 disintegration was exhibited by NH 3 , 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. [ABSTRACT FROM AUTHOR]