Unraveling SO_(2)-tolerant mechanism over Fe_(2)(SO_(4))_(3)/TiO_(2) catalysts for NO_(x) reduction

摘要

Developing low-temperature SO_(2)-tolerant catalysts for the selective catalytic reduction of NO_(x) is still a challenging task.The sulfation of active metal oxides and deposition of ammonium bisulfate deactivate catalysts,due to the difficult decomposition of the as-formed sulfate species at low temperatures(300℃);however,the SO_(2)-tolerant mechanism of metal sulfate catalysts is still ambiguous.In this study,Fe_(2)(SO_(4))_(3)/TiO_(2) and Ce_(2)(SO_(4))_(3)/TiO_(2) catalysts were prepared using the corresponding metal sulfate salt as the precursor.These catalysts were tested for their low-temperature activity and SO_(2) tolerance activity.Compared to Ce_(2)(SO_(4))_(3)/TiO_(2),Fe_(2)(SO_(4))_(3)/TiO_(2) showed significantly better low-temperature activity and SO_(2) tolerance.It was demonstrated that less surface sulfate species formed on Fe_(2)(SO_(4))_(3)/TiO_(2) and Ce_(2)(SO_(4))_(3)/TiO_(2).However,the presence of NO and O_(2) could assist the decomposition of NH_(4)HSO_(4) over Fe_(2)(SO_(4))_(3)/TiO_(2) at a lower temperature,endowing Fe_(2)(SO_(4))_(3)/TiO_(2) with better low-temperature SO_(2) tolerance than Ce_(2)(SO_(4))_(3)/TiO_(2).This study unraveled the SO_(2)-tolerant mechanism of Fe_(2)(SO_(4))_(3)/TiO_(2)at lower temperatures(<300℃),and a potential strategy is proposed for improving the low-temperature SO_(2)-tolerance of catalysts with Fe_(2)(SO_(4))_(3) as the main active component or functional promoter.