After-Treatment System of Medium Duty Engines Using Diesel Fuel as a Reducing Agent for NOx Reduction

Regeneration of atomic Ag sites over commercial γ-aluminas by oxidative dispersion of Ag metal particles

“…γ-Alumina-supported silver (Ag/Al 2 O 3 ) catalysts have long been studied as promising catalysts for the selective catalytic reduction (SCR) of NO x by hydrocarbons (HC-SCR). [1][2][3][4][5] HC-SCR by Ag/Al 2 O 3 has been once commercialized for NO x removal from diesel exhaust. 5 It is well known that H 2 promotes the activity of Ag/Al 2 O 3 for NH 3 -SCR and HC-SCR, [6][7][8][9][10][11][12][13] and many studies have focused on H 2 -assisted SCR by NH 3 (H 2 -NH 3 -SCR) [14][15][16][17][18][19][20] or by HC (H 2 -HC-SCR).…”

“…[1][2][3][4][5] HC-SCR by Ag/Al 2 O 3 has been once commercialized for NO x removal from diesel exhaust. 5 It is well known that H 2 promotes the activity of Ag/Al 2 O 3 for NH 3 -SCR and HC-SCR, [6][7][8][9][10][11][12][13] and many studies have focused on H 2 -assisted SCR by NH 3 (H 2 -NH 3 -SCR) [14][15][16][17][18][19][20] or by HC (H 2 -HC-SCR). [6][7][8][9][10][11][12][13] After a long debate on the active Ag species in HC-SCR reactions, 1,6,13,20 it was concluded that isolated Ag(I) sites are indispensable for achieving highperformance Ag/Al 2 O 3 catalysts for SCR.…”

Redox-Driven Reversible Structural Evolution of Isolated Silver Atoms Anchored to Specific Sites on γ-Al2O3

“…Appropriate designing of sintering-resistant (or regenerable) noble-metal catalysts with 100% dispersion of the active component is crucial for the development of efficient industrial catalysts such as automotive catalysts. − In this context, supported atomically dispersed metal catalysts, also known as single-atom catalysts (SACs), have received significant attention over the past decade as heterogeneous catalysts. − SACs can maximize the utilization of expensive precious metals and can tune the reactivity and stability of metal species by virtue of strong interactions between the metal center and the support . However, if the metal-support interaction is not strong enough to immobilize the isolated metals during a catalytic reaction, the isolated atoms are sintered to reduce the surface energy .…”

“…The alumina-supported silver (Ag/Al 2 O 3 ) catalyst is another example of commercialized SACs. Ag/Al 2 O 3 has long been studied as a promising catalyst for the selective catalytic reduction (SCR) of NO x by hydrocarbons (HC-SCR), − H 2 -assisted HC-SCR, − and H 2 -assisted SCR by NH 3 (H 2 –NH 3 -SCR). − Recently, HC-SCR in the presence of Ag/Al 2 O 3 has been commercialized by Hino Motors Ltd. for NO x removal from diesel exhaust . After a long debate on the active Ag species in HC-SCR reactions, ,,, it was concluded that isolated Ag­(I) sites were indispensable for achieving the high-performance Ag/Al 2 O 3 catalyst for SCR .…”

“…25−31 Al 2 O 3 has been commercialized by Hino Motors Ltd. for NO x removal from diesel exhaust. 1 After a long debate on the active Ag species in HC-SCR reactions, 13,17,24,28 it was concluded that isolated Ag(I) sites were indispensable for achieving the high-performance Ag/Al 2 O 3 catalyst for SCR. 24 Small Ag n δ+ clusters generated from the in situ reduction of Ag(I) species by H 2 or HCs during SCR promoted the reaction under some conditions, while Ag metal NPs had an adverse effect on NO x conversion as they promoted the nonselective oxidation of reductants.…”