Wang Haifeng君が中心となって行ったAg/MnO2触媒によるアンモニア選択酸化に関する研究成果がACS Applied Materials & Interfaces誌 (ACS)にAcceptされました。Our paper reports the selective oxidation of NH3 to N2 over Ag/MnO2 catalysts in ACS Applied Materials & Interfaces(ACS).


「The Development of the Regenerable Catalytic System in Selective Catalytic Oxidation of Ammonia with High N2 Selectivity」

Haifeng Wang, Toru Murayama, Tamao Ishida, Ken-ichi Shimizu, Norihito Sakaguchi, Kazuya Yamaguchi, Hiroki Miura, and Tetsuya Shishido

ACS Applied Materials & Interfaces, 2024, 16, 15, 18693–18702. DOI: 10.1021/acsami.3c17138


Supported particulate noble-metal catalysts are widely used in industrial catalytic reactions. However, these metal species, whether in the form of nanoparticles or highly dispersed entities, tend to aggregate during reactions, leading to a reduced activity or selectivity. Addressing the frequent necessity for the replacement of industrial catalysts remains a significant challenge. Herein, we demonstrate the feasibility of the ‘regenerable catalytic system’ exemplified by selective catalytic oxidation of ammonia (NH3–SCO) employing Ag/Al2O3 catalysts. Results demonstrate that our highly dispersed Ag catalyst (Ag HD) maintains >90% N2 selectivity at 80% NH3 conversion and >80% N2 selectivity at 100% NH3 conversion after enduring 5 cycles of reducible aggregation and oxidative dispersion. Moreover, it consistently upholds over 98% N2 selectivity at 100% NH3 conversion after 10 cycles of Ar treatment. During the aggregation–dispersion process, the Ag HD catalyst intentionally aggregated into Ag nanoparticles (Ag NP) after H2 reduction and exhibited remarkable regenerable capabilities, returning to the Ag HD state after calcination in the air. This structural evolution was characterized through in situ transmission electron microscopy, atomically resolved high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption spectroscopy, revealing the on-site oxidative dispersion of Ag NP. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy provided insights into the exceptional N2 selectivity on Ag HD catalysts, elucidating the critical role of NO+ intermediates. Our findings suggest a sustainable and cost-effective solution for various industry applications.