Premium
The Role of Alkali Metal in α‐MnO 2 Catalyzed Ammonia‐Selective Catalysis
Author(s) -
Hao Zhifei,
Shen Zhurui,
Li Yi,
Wang Haitao,
Zheng Lirong,
Wang Ruihua,
Liu Guoquan,
Zhan Sihui
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201901771
Subject(s) - catalysis , alkali metal , ammonia , chemistry , inorganic chemistry , metal , nox , adsorption , molecule , lewis acids and bases , population , organic chemistry , demography , sociology , combustion
Abstract The unexpected phenomenon and mechanism of the alkali metal involved NH 3 selective catalysis are reported. Incorporation of K + (4.22 wt %) in the tunnels of α‐MnO 2 greatly improved its activity at low temperature (50–200 °C, 100 % conversion of NO x vs. 50.6 % conversion over pristine α‐MnO 2 at 150 °C). Experiment and theory demonstrated the atomic role of incorporated K + in α‐MnO 2 . Results showed that K + in the tunnels could form a stable coordination with eight nearby Osp3atoms. The columbic interaction between the trapped K + and O atoms can rearrange the charge population of nearby Mn and O atoms, thus making the topmost five‐coordinated unsaturated Mn cations (Mn 5c , the Lewis acid sites) more positive. Therefore, the more positively charged Mn 5c can better chemically adsorb and activate the NH 3 molecules compared with its pristine counterpart, which is crucial for subsequent reactions.