Performance of Low‐temperature SCR of NO with NH3 over MnOx/Ti‐based catalysts

Abstract

The effects of Mn loadings and precursors, catalyst preparation methods, incineration durations and temperatures, and the addition of Co and Ce on NO‐reduction efficiency and selectivity (N₂O formation) during the preparation of MnOx/Ti‐based catalysts were studied by micropore‐size analysis (XRD, XPS, SEM, and FTIR), while considering changeable parameters. Meanwhile, the performance of low‐temperature SCR of NO with NH₃ over the designed catalysts was tested under various gas hourly space velocities (GHSVs), NH₃/NO molar ratios, and contents of NO, NH₃, O₂, H₂O, and SO₂ in a lab‐scale reactor. Overall, the Mn(0.3)Ce(0.1)/Ti catalyst, which had high NO‐reduction efficiency and selectivity (low N₂O formation), was recommended, with the following preparation methods: ultrasonic impregnation; manganese acetate precursor; and incineration at 500 °C. Appropriate textural properties (high surface area and small pore and crystallite sizes), well‐dispersed amorphous manganese (rather than crystalline) on the anatase surface (rather than rutile), abundant active sites, and long residence time are essential for high NO‐reduction efficiency. In practice, NO‐reduction efficiency decreased with increasing GHSV and the NH₃ and NO contents; however, it initially increased and then became saturated with an increasing NH₃/NO molar ratio and O₂ content. Water deactivated the catalyst to a recoverable state, whereas SO₂ resulted in unrecoverable deactivation.