Enhanced performance in NOx reduction by NH3 over a mesoporous Ce–Ti–MoOx catalyst stabilized by a carbon template

Abstract

Mesoporous Ce–Ti–MoO_x catalysts have been prepared by stabilization with an in situ formed carbon template and used for selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The Ce–Ti–MoO_x catalysts were characterized by N₂ adsorption–desorption, XRD, HR-TEM, H₂-TPR and XPS analysis. It was found that the stabilization with a carbon template obviously improved the NO_x conversion of the Ce–Ti–MoO_x catalyst and the pore distribution. The Ce–Ti–MoO_x catalyst stabilized with a carbon template at 850 °C in N₂ exhibited the best NH₃-SCR activity and showed a uniform mesopore distribution, and more than 90% NO_x conversions were obtained at 175–425 °C with a GHSV of 60 000 h⁻¹. The high stabilization temperature with a carbon template in N₂ not only led to an increase in specific surface area, pore volume and low-temperature SCR activity, but also contributed to the enhanced redox properties, highly dispersed titanium or molybdenum species and narrow mesopore distribution. The treatment of Ce–Ti–MoO_x with a high calcination temperature for removal of the carbon template led to a drastic decrease in surface area, an abrupt decrease in surface oxygen and cerium, production of rutile TiO₂, and a correspondingly low SCR activity.