Design of a dual-bed catalyst system with microporous carbons and urea-supported mesoporous carbons for highly effective removal of NOx at room temperature

ECO PHYSICS CLD 62

A dual-bed catalyst system is designed to remove NO_x at room temperature, which consists of a microporous spherical activated carbon (SAC) layer and a urea-supported spherical mesoporous carbon (SMC) layer. The SAC layer, with plenty of narrow micropores acting as a nano-cage for NO adsorption, could improve the oxidation of NO into NO₂, while the urea-supported SMC layer with large surface area could provide a sufficient channel for gas kinetic diffusion and a high gas/urea interfacial area for efficient NO₂ reduction. A high stationary-state NO_x conversion of 88% for 70 h is achieved through the dual-bed catalyst system with SAC and 100 wt% urea supported SMC as the catalyst. The selective catalytic reduction (SCR) activity could be improved by increasing the NO and O₂ feed concentration, due to the enhanced oxidation of NO to NO₂. A low reaction temperature is beneficial for the SCR reaction because of the increased NO adsorption. Moreover, the apparent activation energies are calculated to be −16.8 kJ mol⁻¹ for NO oxidation and 1.18 kJ mol⁻¹ for NO₂–urea SCR, respectively. The result reveals that the adsorption of reactants on SAC is of key importance for NO oxidation, while the surface reaction of NO₂ with urea could be the crucial step for the SCR reaction.

http://pubs.rsc.org/en/content/articlelanding/2016/ra/c5ra28131h#!divAbstract