Low temperature selective catalytic reduction of NO over manganese supported on TiO₂ nanotubes

Titanate nanotubes were synthesized hydrothermally with commercial TiO₂ nanoparticles in NaOH; after calcination at 400℃, TiO₂ nanotubes were obtained and used as the support to prepare manganese catalyst (MnO_x/TiNT) by wet-impregnation for low temperature selective catalytic reduction of NO (SCR). The results of BET, TEM, XRD and TG measurements showed that TiO₂ nanotubes exhibit well-defined TiO₂ anatase phase after calcination at 400℃ and manganese particles are highly dispersed on the wall of TiO₂ nanotubes. The effects of active component loading, space velocity, oxygen content, \[NH₃\]/\[NO\] 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℃, \[NH₃\]/\[NO\] of 1.2, \[O₂\] of 3%, \[NO\] of 0.06%, GHSV of 23613.8h^-1 and Mn loading of 5%~15%(mass ratio), NO conversion exceeds 95%. The catalyst is deactivated in the presence of H₂O at 180℃, but its activity can be recovered almost completely when cutting off H₂O; higher resistance to H₂O is observed at higher temperature. The presence of SO₂ can also deactivate the catalyst gradually; however, the catalyst exhibits better resistance toward SO₂ in the presence of H₂O than that without H₂O. The SCR activity of MnO_x/TiNT catalyst deactivated by SO₂ rises gradually after cutting off H₂O + SO₂, but cannot be recovered to its initial level.