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Morphology Effect of Ceria on the Ammonia Synthesis Activity of Ru/CeO2 Catalysts

  • Pengcheng Liu
  • Ruyue Niu
  • Wei Li
  • Shuang WangEmail author
  • Jinping LiEmail author
Article
  • 4 Downloads

Abstract

Three Ru/CeO2 catalysts with different morphologies of CeO2 (cube spheres, microspheres and nano rods) were used to evaluate the support-morphology-dependent ammonia synthesis activity. Catalytic experiments show that the Ru/CeO2–CS catalyst has higher catalytic activity (27,000 µmol g−1 h−1) than Ru/CeO2–MS (21,000 µmol g−1 h−1) and Ru/CeO2–NR (15,000 µmol g−1 h−1) under the reaction conditions of 450 °C, 3 MPa, H2/N2 = 3:1 (60 mL min−1). The transmission electron microscopy analysis showed that the dispersion of active metal Ru is affected by the morphology of CeO2. Brunauer–Emmett–Teller indicates that the 3–5 nm the pore size of CeO2 supports contributes to the active metal Ru enters the pores of the CeO2 support, which improves the dispersion of Ru and prevents the sintering and agglomeration of Ru in some extent. TPR studies shown that the reduction of ruthenium oxide is influenced by the morphology of CeO2. XPS and CO2-TPD demonstrated that the Ru/CeO2–CS catalyst exhibited higher surface oxygen vacancies, higher basic site density and lower Ru binding energy, indicating that Ru nanoparticles in Ru/CeO2–CS is more electron-rich and are more capable of back-donating electrons to adsorbed N2 and subsequently activate N2. Our results indicate that the morphology effect of the CeO2 supports on the Ru/CeO2 catalyst is related to the pore size distribution and the surface oxygen vacancies of the CeO2 supports, ratio of Run+, basic site density.

Graphical Abstract

The CeO2–CS (cube spheres) morphology facilitated the dispersion of the active metal Ru and the 3 nm the pore size of CeO2–CS contributed to the Ru enters the pores of the support. And the Ru/CeO2–CS catalyst exhibited higher surface oxygen vacancies and lower Ru binding energy, which enhanced the adsorption of hydrogen and nitrogen species and thus weakened the N≡N bond.

Keywords

Ammonia synthesis Ru-based catalyst Cerium oxide morphology Catalytic performance 

Notes

Acknowledgements

The authors acknowledge the financial support of the Natural Science Foundation of China (Grant No. 21671147), Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi, State Key Laboratory of Coal and CBM Co-mining (Grant No. 2016012004).

Supplementary material

10562_2019_2674_MOESM1_ESM.docx (1.5 mb)
Supplementary material 1 (DOCX 1535 KB)

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Shanxi Key Laboratory of Gas Energy Efficient and Clean UtilizationTaiyuan University of TechnologyTaiyuanPeople’s Republic of China
  2. 2.College of Environmental Science and EngineeringTaiyuan University of TechnologyJinzhongPeople’s Republic of China

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