Mn-Ce Oxide Nanoparticles Supported on Nitrogen-Doped Graphene for Low-Temperature Catalytic Reduction of NOx: De-Nitration Characteristics and Kinetics

Abstract

Selective catalytic reduction (SCR) of NOx with NH3 as the reductant has been proven an efficient and cost-effective technology to remove NOx pollutants in industries. Traditional SCR catalysts usually operate above 300 °C and suffer from intoxication and limited lifetime. Nano-catalysts are attractive for their high catalytic activities at reduced operating temperatures. We have recently developed a series of nitrogen-doped graphene-supported Mn-Ce oxides (MnCeOx/NG). The influences of reaction temperature, space velocity, mole ratio of NH3/NO and O2 concentration on SCR de-nitration activity were assessed. The novel catalyst with optimal Mn/Ce ratio, at appropriate processing conditions, can achieve a NO conversion efficiency of 99.5% at a temperature of 180 °C, and 93.5% at 150 °C. The kinetics of the SCR reaction on this novel catalyst were also established, exhibiting first-order with respect to NO, zero-order to NH3, and nearly 0.5-order to O2 at low temperatures. In the presence of sufficient O2 content, the apparent activation energy of the NH3-SCR on MnCeOx/NG is 37.6 kJ/mol, which is promising for low-temperature applications.