Developing efficient catalysts for elimination of ammonia at room temperature for air quality improvement

2020 Fiscal Year Research-status Report

• Project/Area Number: 19K15363
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: 林 明月 東京都立大学, 都市環境科学研究科, 特任助教 (30813357)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: selective oxidation / ammonia / high N2 selectivity / precious metals / acid sites / niobium oxide

Outline of Annual Research Achievements

The research is proceeding steadily as planned.
(1) Important roles of Bronsted acid sites for the high N2 selectivity in the selective catalytic oxidation of NH3 have been further proved on Pt/Nb2O5 and Pd/Nb2O5 catalysts. The N2 selectivity at the full conversion of NH3 reached as high as 98% and 100% on Pt/Nb2O5 and Pd/Nb2O5, respectively, which break through the challenges of low N2 selectivity on precious metals catalysts. This work will provide a safe method to solve the NH3 pollution by avoiding the formation of harmful by-products of NOx. This work has been published on Journal of Catalysis （Lin, Mingyue, et al. "Features of Nb2O5 as a metal oxide support of Pt and Pd catalysts for selective catalytic oxidation of NH3 with high N2 selectivity." Journal of Catalysis 389, 366-374.）
(2) Except for the precious metals supported on Nb2O5, such as Au, Pt, and Pd that we have developed which showed good catalytic activity and high N2 selectivity, we are trying to develop cheaper catalysts for selective catalytic oxidation of NH3. Ag/MnO2 has been screened out to be a good candidate for the low-temperature highly N2 selective catalyst for NH3 oxidation. Size effect of Ag on activity and N2 selectivity has been studied in detail. This work has been submitted to ACS Catalysis and now is under revision.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

The research is proceeding rather steadily as planned. In addition to the precious metals (Au, Pt, and Pd) supported on Nb2O5 that have been screened out to be highly selective to N2 formation for selective catalytic oxidation of NH3 and the important roles of Bronsted acid sites in N2 selectivity have been proved, a cheaper catalyst Ag/MnO2 with good catalytic activity and N2 selectivity has been screened out. The effect of Ag size effect on catalytic activity and N2 selectivity has been studied in detail. In the research plan, the investigation of the water effect and the design of water-proof catalysts for selective catalytic oxidation of NH3 was not proceeding smoothly. It is because the balance of water-proof functional groups, the size of precious metals, and the amount of Bronsted acid sites is difficult to control. Therefore, the catalytic performances of these catalysts under the water atmosphere were not ideal. We will continue to develop suitable preparation methods for acidic metal oxides supported precious metals with water-proof functional groups.

Strategy for Future Research Activity

The future research plan will be focused on three points:
(1) Developing cheaper catalysts for selective catalytic oxidation of NH3 for commercialization in the air purification industry.
(2) Investigating the water effect of the developed catalysts such as Au/Nb2O5, Pt/Nb2O5, Pd/Nb2O5, and Ag/MnO2 on selective catalytic oxidation of NH3 for practical applications.
(3) Studying the structure-function effect between catalysts and catalytic performance for the better design of effective catalyst and for better understanding the reaction mechanism.

Research Products

• [Journal Article] Features of Nb2O5 as a metal oxide support of Pt and Pd catalysts for selective catalytic oxidation of NH3 with high N2 selectivity (2020)
  • Author(s): Lin, M., An, B., Takei, T., Shishido, T., Ishida, T., Haruta, M. and Murayama, T.
  • Journal Title: Journal of Catalysis Volume: 389 Pages: 366-374
  • DOI: 10.1016/j.jcat.2020.05.040
  • Peer Reviewed
• [Journal Article] Elucidation of Active Sites of Gold Nanoparticles on Acidic Ta2O5 Supports for CO Oxidation (2020)
  • Author(s): Lin, M., Mochizuki, C., An, B., Inomata, Y., Ishida, T., Haruta, M. and Murayama, T.
  • Journal Title: ACS Catalysis Volume: 10(16) Pages: 9328-9335
  • DOI: 10.1021/acscatal.0c01966
  • Peer Reviewed
• [Presentation] Effects of solid acidity of the support on the selective catalytic oxidation of NH3 by the niobium oxide supported precious metals catalysts (2020)
  • Author(s): Mingyue Lin,Baoxiang An, Yohei Jikihara, Fukui Yoko, Tsuruo Nakayama,Toru Murayama, Masatake Haruta, Tamao Ishida, Sadao Yasui, Takashi Takei,Tetsuya Shishido,
  • Organizer: 第126回触媒討論会
• [Presentation] Role of acid sites for selective catalytic oxidation of NH3: the case of niobium oxide supported precious metals catalysts (2020)
  • Author(s): Mingyue Lin, Baoxiang An,Takashi Takei, Tetsuya Shishido, Tamao Ishida, Masatake Haruta,Toru Murayama
  • Organizer: 熊本大会(第50回石油・石油化学討論会)
• [Patent(Industrial Property Rights)] 脱臭触媒 (2020)
  • Inventor(s): 2020
  • Industrial Property Rights Holder: 2020
  • Industrial Property Rights Type: 特許
  • Industrial Property Number: 特願2020-148138