Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature

Yuta Ogura, Katsutoshi Sato, Shin Ichiro Miyahara, Yukiko Kawano, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Saburo Hosokawa, Katsutoshi Nagaoka

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Abstract

Ammonia is an important feedstock for producing fertiliser and is also a potential energy carrier. However, the process currently used for ammonia synthesis, the Haber-Bosch process, consumes a huge amount of energy; therefore the development of new catalysts for synthesising ammonia at a high rate under mild conditions (low temperature and low pressure) is necessary. Here, we show that Ru/La0.5Ce0.5O1.75 pre-reduced at an unusually high temperature (650 °C) catalysed ammonia synthesis at extremely high rates under mild conditions; specifically, at a reaction temperature of 350 °C, the rates were 13.4, 31.3, and 44.4 mmol g-1 h-1 at 0.1, 1.0, and 3.0 MPa, respectively. Kinetic analysis revealed that this catalyst is free of hydrogen poisoning under the conditions tested. Electron energy loss spectroscopy combined with O2 absorption capacity measurements revealed that the reduced catalyst consisted of fine Ru particles (mean diameter < 2.0 nm) that were partially covered with partially reduced La0.5Ce0.5O1.75 and were dispersed on a thermostable support. Furthermore, Fourier transform infrared spectra measured after N2 addition to the catalyst revealed that N2 adsorption on Ru atoms that interacted directly with the reduced La0.5Ce0.5O1.75 weakened the NN bond and thus promoted its cleavage, which is the rate-determining step for ammonia synthesis. Our results indicate that high-temperature pre-reduction of this catalyst, which consists of Ru supported on a thermostable composite oxide with a cubic fluorite structure and containing reducible cerium, resulted in the formation of many sites that were highly active for N2 reduction by hydrogen.

Original languageEnglish
Pages (from-to)2230-2237
Number of pages8
JournalChemical Science
Volume9
Issue number8
DOIs
Publication statusPublished - Jan 1 2018

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Ammonia
Catalysts
Hydrogen
Temperature
Catalyst poisoning
Cerium
Fluorspar
Electron energy loss spectroscopy
Fertilizers
Potential energy
Oxides
Feedstocks
Fourier transforms
Infrared radiation
Adsorption
Atoms
Kinetics
Composite materials

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

Ogura, Y., Sato, K., Miyahara, S. I., Kawano, Y., Toriyama, T., Yamamoto, T., ... Nagaoka, K. (2018). Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature. Chemical Science, 9(8), 2230-2237. https://doi.org/10.1039/c7sc05343f

Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature. / Ogura, Yuta; Sato, Katsutoshi; Miyahara, Shin Ichiro; Kawano, Yukiko; Toriyama, Takaaki; Yamamoto, Tomokazu; Matsumura, Syo; Hosokawa, Saburo; Nagaoka, Katsutoshi.

In: Chemical Science, Vol. 9, No. 8, 01.01.2018, p. 2230-2237.

Research output: Contribution to journalArticle

Ogura, Y, Sato, K, Miyahara, SI, Kawano, Y, Toriyama, T, Yamamoto, T, Matsumura, S, Hosokawa, S & Nagaoka, K 2018, 'Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature', Chemical Science, vol. 9, no. 8, pp. 2230-2237. https://doi.org/10.1039/c7sc05343f
Ogura Y, Sato K, Miyahara SI, Kawano Y, Toriyama T, Yamamoto T et al. Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature. Chemical Science. 2018 Jan 1;9(8):2230-2237. https://doi.org/10.1039/c7sc05343f
Ogura, Yuta ; Sato, Katsutoshi ; Miyahara, Shin Ichiro ; Kawano, Yukiko ; Toriyama, Takaaki ; Yamamoto, Tomokazu ; Matsumura, Syo ; Hosokawa, Saburo ; Nagaoka, Katsutoshi. / Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature. In: Chemical Science. 2018 ; Vol. 9, No. 8. pp. 2230-2237.
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