The reaction mechanism for the SCR process on monomer V5+ sites and the effect of modified Bronsted acidity

TY - JOUR

T1 - The reaction mechanism for the SCR process on monomer V5+ sites and the effect of modified Bronsted acidity

AU - Arnarson, Logi

AU - Falsig, Hanne

AU - Rasmussen, Soren B.

AU - Lauritsen, Jeppe V.

AU - Moses, Poul Georg

PY - 2016/7/7

Y1 - 2016/7/7

N2 - The energetics, structures and activity of a monomeric VO 3H/TiO 2(001) catalyst are investigated for the selective catalytic reduction (SCR) reaction by the use of density functional theory (DFT). Furthermore we study the influences of a dopant substitute in the TiO 2 support and its effects on the known properties of the SCR system such as Brønsted acidity and reducibility of vanadium. We find for the reduction part of the SCR mechanism that it involves two Ti-O-V oxygen sites. One is a hydroxyl possessing Brønsted acidity which contributes to the formation of NH 4 +, while the other accepts a proton which charge stabilizes the reduced active site. In the reduction the proton is donated to the latter due to a reaction between NH 3 and NO that forms a H 2NNO molecule which decomposes into N 2(g) and H 2O(g). A dopant substitution of 10 different dopants: Si, Ge, Se, Zr, Sn, Te, Hf, V, Mo and W at each of the sites, which participate in the reaction, modifies the energetics and therefore the SCR activity. We find that Brønsted acidity is a descriptor for the SCR activity at low temperatures. Based on this descriptor we find that Zr, Hf and Sn have a positive effect as they decrease the activation energy for the SCR reaction.

AB - The energetics, structures and activity of a monomeric VO 3H/TiO 2(001) catalyst are investigated for the selective catalytic reduction (SCR) reaction by the use of density functional theory (DFT). Furthermore we study the influences of a dopant substitute in the TiO 2 support and its effects on the known properties of the SCR system such as Brønsted acidity and reducibility of vanadium. We find for the reduction part of the SCR mechanism that it involves two Ti-O-V oxygen sites. One is a hydroxyl possessing Brønsted acidity which contributes to the formation of NH 4 +, while the other accepts a proton which charge stabilizes the reduced active site. In the reduction the proton is donated to the latter due to a reaction between NH 3 and NO that forms a H 2NNO molecule which decomposes into N 2(g) and H 2O(g). A dopant substitution of 10 different dopants: Si, Ge, Se, Zr, Sn, Te, Hf, V, Mo and W at each of the sites, which participate in the reaction, modifies the energetics and therefore the SCR activity. We find that Brønsted acidity is a descriptor for the SCR activity at low temperatures. Based on this descriptor we find that Zr, Hf and Sn have a positive effect as they decrease the activation energy for the SCR reaction.

KW - SELECTIVE CATALYTIC-REDUCTION

KW - VANADIA-TITANIA CATALYSTS

KW - NITRIC-OXIDE

KW - PHOTOCATALYTIC ACTIVITY

KW - NO REDUCTION

KW - AMMONIA

KW - NH3

KW - ANATASE

KW - V2O5/TIO2

KW - SURFACE

UR - http://www.scopus.com/inward/record.url?scp=84976314602&partnerID=8YFLogxK

U2 - 10.1039/c6cp02274j

DO - 10.1039/c6cp02274j

M3 - Journal article

C2 - 27297567

SN - 1463-9076

VL - 18

SP - 17071

EP - 17080

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

IS - 25

ER -