The ordered mesoporous transition metal oxides for selective catalytic reduction of NOx at low temperature

Abstract

The ordered mesoporous Co3O4, NiO and NiCo2O4 were synthesized by nanocasting method using mesoporous KIT-6 as a hard template. Their structural and textural properties were well characterized by powder X-ray diffraction, transmission electron microscopy and nitrogen physisorption. The surface areas of these catalysts are 380–426m2/g. Selective catalytic reduction (SCR) of NOx with hydrogen demonstrates that NiCo2O4 possesses the highest catalytic activity at 50–400°C, whose NOx conversion is more than 70% at 150°C, and N2 selectivity is more than 90% at 100–400°C. In addition, NiCo2O4 exhibits better stability in the presence of 100ppm SO2 and 10vol% H2O in SCR of NOx at 250°C. XPS analyses show that surface adsorption oxygen concentration in NiCo2O4 is higher than that in Co3O4 and NiO. The synergetic effect between Ni and Co is responsible for the enhancement of low-temperature SCR activity and the improvement of regeneration performance in NiCo2O4. In comparison with NiCo2O4-CP synthesized by co-precipitation method, the ordered mesoporous structure in NiCo2O4 provides larger surface area, more activated oxygen species and more reductive species, resulting in higher SCR performance at low temperature.