Removal of NO at low temperature and in the absence of ammonia over spherical activated carbon loaded with MnO_x-CeO₂ and urea

A complex catalyst was prepared by loading MnO_x-CeO₂ and urea on spherical activated carbon (SAC) for the selective catalytic reduction (SCR) of NO at low temperature (30-90 ℃) in the absence of ammonia. The complex catalyst was characterized by scanning electron microscopy-energy dispersive spectrum (SEM-EDS), X-ray diffraction (XRD), and N₂ sorption. The results show that at 30-50 ℃, the micropores of SAC acts as the main active sites for NO adsorption and reaction, whereas at 70-90 ℃, MnO_x-CeO₂ turns to be the main active sites for NO adsorption and reaction; the urea-SCR activity is enhanced by MnO_x-CeO₂ in a wide temperature range. Over the complex catalyst loaded with 8% Mn (the mole ratio of Mn to Ce is 1) and 10% urea, the steady conversion of MO_x reaches 85.6% in the absence of ammonia, under the conditions of 90 ℃, 0.05% NO, 20% O₂ and a space velocity of 6000 h^-1.