Mn mixed oxide catalysts supported on Sn-doped CoAl-LDO for low-temperature NH3-SCR

Abstract

SCR technology is considered to be the most effective method for denitrification. However, the low NO_x conversion rate of the current catalysts at low temperatures limits their further application. Herein, Sn-doped modified CoAl-LDH carriers are synthesized by a hydrothermal method, and the typical hexagonal sheet structure of the MnO_x(0.25)/CoSn₃Al-LDO catalyst achieves 100% NO conversion at a wide range of 120–330 °C with a GHSV of 30 000 h⁻¹, and the 100% NO conversion may be maintained at 200 °C for 30 h. After the introduction of 150 ppm SO₂ at 200 °C, the NO conversion of the MnO_x(0.25)/CoSn₃Al-LDO catalyst is maintained at 73.4%, which is greatly improved compared with those of CoAl-LDO and MnO_x(0.25)/CoAL-LDO catalysts (64.8% and 38.6%, respectively). The active components such as MnO_x and Co₃O₄ are highly dispersed in the MnO_x(0.25)/CoSn₃Al-LDO catalyst. Sn doping increases the ratios of Mn⁴⁺/Mn³⁺ and Co³⁺/Co²⁺ as well as the adsorbed oxygen amount on the catalyst surface, and improves the redox capacity of the catalyst and increases the number of acid sites, resulting in the excellent low-temperature NH₃-SCR performance of MnO_x(0.25)/CoSn₃Al-LDO.