Low-temperature selective catalytic reduction of NO over manganese supported on TiO 2 nanotubes

Abstract

Titanate nanotubes were synthesized hydrothermally from commercial TiO 2 nanoparticles in the presence of NaOH; after calcination at 400°C, TiO 2 nanotubes were obtained, which were used as the support to prepare manganese catalyst (MnO x /TiNT) by wet impregnation for the low-temperature selective catalytic reduction (SCR) of NO. The results of Brunauer, Emmett and Teller study, transmission electron microscopy, X-ray diffraction, and thermogravimetric measurements showed that TiO 2 nanotubes exist in a well-defined TiO 2 anatase phase after calcination at 400°C and that manganese particles are highly dispersed on the wall of TiO 2 nanotubes. The effects of active-component loading, space velocity, oxygen content, [NH 3]/[NO] ratio, and NO concentration on the SCR performance of MnO x /TiNT were investigated in a simulated flue gas. Under the reaction conditions of 150°C, [NH 3]/[NO] of 1.2, [O 2] of 3%, [NO] of 0.06%, gas hour space velocity of 23613.8 h −1, and Mn loading of 5–15%, NO conversion exceeds 95%. The catalyst is deactivated in the presence of H 2O at 180°C, but its activity can be recovered almost completely by cutting off H 2O. Moreover, higher resistance to H 2O is observed at higher temperatures. The presence of SO 2 can also deactivate the catalyst gradually; however, the catalyst shows better resistance to SO 2 in the presence of H 2O than in its absence. The SCR activity of the MnO x /TiNT catalyst that is deactivated by SO 2 increases gradually after cutting off H 2O and SO 2 but cannot be restored to its initial level.