The Role of Alkali Metal in α‐MnO₂ Catalyzed Ammonia‐Selective Catalysis

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 a-MnO 2 greatly improved its activity at lowt emperature (50-200 8 8C, 100 %c onversion of NO x vs.5 0.6 %c onversion over pristine a-MnO 2 at 150 8 8C). Experiment and theory demonstrated the atomic role of incorporated K + in a-MnO 2 .R esults showed that K + in the tunnels could form as table coordination with eight nearby O sp 3 atoms.The columbic interaction between the trapped K + and Oatoms can rearrange the charge population of nearby Mn and Oa toms,t hus making the topmost fivecoordinated unsaturated Mn cations (Mn 5c ,t he Lewis acid sites) more positive.T herefore,t he more positively charged Mn 5c can better chemically adsorb and activate the NH 3 molecules compared with its pristine counterpart, whichi s crucial for subsequent reactions.

Co-blending modification of activated coke using pyrolusite and titanium ore for low-temperature NOx removal

“…On the basis of the results of this work and previous reports, the Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms coexist in the NH 3 -SCR reaction over (P/Ti-1/2)15@AC 45 , 50 , 51 . Both the gaseous and adsorbed NO reacted to the surface adsorbed NH 3 due to the carbon and titanium composite structure.…”

“…In addition, the characterization peaks at 1460 and 875 cm −1 for both AC and (P/Ti-1/2)15@AC were intensified possibly because of the adsorbed NH 3 dehydrogenation process (Fig. 3 b, d), which was reported as the controlling step of denitrification 45 , 46 . On the basis of the XPS results, the additional surface oxygen of the sample after the SCR reaction increased by 4.66% and 0.94% of AC and (P/Ti-1/2)15@AC (Table 3 ).…”

Electrolytic Manganese Anode Mud as the Low Temperature NH3-Scr Catalyst: The Effect of K and Pb

“…In Table 1, after a long period leaching test, the content of K + remained a constant, which indicated that the K + incorporated in the tunnels of α-MnO2. The result is highly consistent with the conclusions of Ref [7]. K + ions in the tunnel would promote the adsorption and activation of NH3 has been proved.…”

“…In addition, the potassium ion in the EMAM remained a certain content after many times water wash process. It also should be taken into account because alkali metals generally have a certain effect on the SCR process [7]. In order to take full advantage of EMAM to produce low temperature SCR catalyst, it is much meaningful to figure out the effect of Pb and K ion on the low temperature SCR in the EMAM.…”

Synergistic Lewis acid-base sites of ultrathin porous Co3O4 nanosheets with enhanced peroxidase-like activity

“…Hence, nanozymes usually have active centers or electron transport structures similar to natural enzymes by regulation strategy, which endow the nanozymes with efficient activity [1,15]. Surface acid-base active sites of metal oxides have been investigated in interfacial catalysis, such as heterogeneous industrial catalytic reactions, organic synthesis, and polymerization reaction [16][17][18]. The surface Lewis acid sites have an unoccupied orbital and the Lewis base can provide a lone pair of electrons [19].…”