A study of the mechanism of low-temperature SCR of NO with NH3 on MnOx/CeO2

A MnOx/CeO2 supported catalyst was prepared using the deposition-precipitation (DP) method for low-temperature selective catalytic reduction (SCR) of NO with NH3. At short reaction time, nearly 100% NO conversion was obtained across the whole evaluated temperature range of 80-150 degrees C at a space velocity of 50,000 h(-1). The catalyst rapidly lost its activity at 80 degrees C, while stable activity was achieved at 120 degrees C at a space velocity of 120,000h(-1) in a 36 h test. A possible reaction pathway is proposed based on the results of an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study coupled with mass spectrometric (MS) data. It is suggested that the NH3-SCR reaction on the MnOx/CeO2 catalyst involves a [NH3...NO-] complex as an intermediate, the decomposition of which into N-2 and H2O is the rate-limiting step. The role of oxygen in the SCR reaction is to reoxidize the reduced catalyst surface, thereby completing the catalytic cycle. (C) 2013 Elsevier B.V. All rights reserved.