Preparation of CeO2-CePO4 Denitration Catalyst with Wide Temperature Window by a Citric Acid-Assisted Precipitation Method

Abstract

The catalytic activity window of conventional commercial V₂O₅-WO₃/TiO₂ is too narrow, which is a main problem for selective catalytic reduction of NO_x by NH₃ (NH₃-SCR) catalysts. Herein, a series of CeO₂-CePO₄-CA-x (x = 1–6) catalysts with wide temperature windows were prepared by a citric acid-assisted precipitation method. The series has the widest temperature window of 212.9-579.7^oC in which the NO conversion can exceed 80% when x is 4. Compared with the CeO₂-CePO₄ catalyst prepared without adding citric acid, CeO₂-CePO₄-CA-4 exhibits better water and sulfur resistance, lower SCR activation energy, and greater turnover frequency. The prepared catalysts were characterized by N₂ adsorption-desorption, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), temperature-programmed reduction of H₂ (H₂-TPR), and temperature-programmed desorption of NH₃ (NH₃-TPD). Results showed that the CeO₂-CePO₄-CA-4 composites had more uniform mesoporous pore size and higher Ce³⁺ and surface adsorbed oxygen content, higher H₂ consumption, and greater number of acidic sites than CeO₂-CePO₄. All of those are conducive to redox performance enhancement, thus improving the NH₃-SCR reactivity and water and sulfur resistance of the catalyst. CeO₂-CePO₄-CA-4 with a wide temperature window as well as good SO₂ resistance shows good prospects in industrial applications.

Graphical Abstract

Comparison of the NO conversions of the catalysts. We prepared a series of CeO₂-CePO₄-CA-x (x = 1–6) catalysts with wide temperature windows using a citric acid-assisted precipitation method. The series has the widest temperature window of 212.9-579.7^oC in which the NO conversion can exceed 80% when x is 4. Compared with the CeO₂-CePO₄ catalyst prepared without adding citric acid, CeO₂-CePO₄-CA-4 exhibits better water and sulfur resistance, lower SCR activation energy, and greater turnover frequency