Automobile exhaust emission control by catalysts

Belton, David N.; Taylor, Kathleen C.

doi:10.1016/s1359-0286(99)80017-5

Cited by 47 publications

(21 citation statements)

References 96 publications

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“…[1][2][3] One of the most common and established use of palladium catalyst is to control automobile exhaust gas emission. [4][5][6] Use of catalytic converter in automobile exhaust is a requirement to reach the recommended limits for emission of toxic byproducts. Although studies have been dedicated to the understanding of the catalytic conversion process in the exhaust emission, 7 more fundamental studies are still necessary for a full comprehension of the catalytic process, particularly at the molecular level.…”

Section: Introductionmentioning

confidence: 99%

“…[10][11][12] These supported catalysts are thus employed to remove carbon monoxide (CO), nitric oxide (NO), NO x and SO x contaminants, among others, from the exhaust engine. [4][5][6] Nitric oxide has an odd number of electrons and is one of the most versatile molecules, making its chemistry and adsorption process of particular interest. 13 The adsorption of NO on the supported catalyst surface has been investigated by both experimental 7,[14][15][16][17][18][19][20] and theoretical procedures.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Gamma-Al₂O₃Support on the NO Adsorption on Pd₄Cluster

Prates

Ferreira

Carneiro

et al. 2016

Journal of the Brazilian Chemical Society

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The effect of γ-Al 2 O 3 support on the NO adsorption on Pd 4 clusters was investigated by means of density functional theory (DFT) calculations. Pd 4 adsorbed on γ-Al 2 O 3 (represented by a Al 14 O 24 H 6 cluster) changes its preferential geometry from tetrahedral to a distorted planar structure. The alumina support promotes a higher dispersion in the palladium catalyst and reduces the NO adsorption energy to -25.6 kcal mol -1 (computed at B3LYP/LANL2DZ/6-311+G(d)), in close agreement with the experimental value of -27.2 kcal mol . Charge density analysis show that the electron flux between the NO molecule and Pd 4 depends on the adsorption form, with back-donation being stronger in the bridge adsorption mode.Keywords: Pd clusters, DFT, supported-Pd clusters, alumina, NO adsorption, back-donation IntroductionPalladium catalysts have found wide appllication in several areas of chemistry. [1][2][3] One of the most common and established use of palladium catalyst is to control automobile exhaust gas emission. [4][5][6] Use of catalytic converter in automobile exhaust is a requirement to reach the recommended limits for emission of toxic byproducts. Although studies have been dedicated to the understanding of the catalytic conversion process in the exhaust emission, 7 more fundamental studies are still necessary for a full comprehension of the catalytic process, particularly at the molecular level. 8,9 Commonly, the platinum and palladium catalysts are supported on metal oxides, among them γ-Al 2 O 3 , although oxides of cerium, zirconium and titanium are also frequently employed. [10][11][12] These supported catalysts are thus employed to remove carbon monoxide (CO), nitric oxide (NO), NO x and SO x contaminants, among others, from the exhaust engine. [4][5][6] Nitric oxide has an odd number of electrons and is one of the most versatile molecules, making its chemistry and adsorption process of particular interest. 13 The adsorption of NO on the supported catalyst surface has been investigated by both experimental 7,14-20 and theoretical procedures. [21][22][23][24][25][26][27][28][29] NO adsorbs on small Pd clusters through its nitrogen atom in a tilted orientation, preferentially in the hcp threefold and bridge sites, 27 although the relative binding energies are strongly dependent on the size and geometry of the cluster employed. 27 For adsorption of NO on an extended surface at low coverage the interaction is determined by electron donation and back-donation involving the 5σ/2π* antibonding orbital of the NO molecule and the d-bands of the transition metal, with a net charge transfer from the transition metal to the adsorbed NO. 29 However, the extent of the interaction via the back-donation process is strongly dependent on the coordination mode of the NO molecule. On a flat surface, the preferential adsorption occurs on a hollow-site. 29 Adsorption on the energetically less favorable top-site results in tilted orientation with the NO bent to the metal surface.In the vast literature on theoretical studies of N...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Gamma-Al₂O₃Support on the NO Adsorption on Pd₄Cluster

Prates

Ferreira

Carneiro

et al. 2016

Journal of the Brazilian Chemical Society

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show abstract

“…Thus, other technologies are being developped, including the SCR with the presence of reductants in the exhaust, e.g. hydrocarbon [26], and the NOx storage and reduction (NSR) [27][28][29][30][31][32][33][34], which seems to be the most promising technology and to which is dedicated in this chapter.…”

Section: Automobile Exhaust Aftertreatmentmentioning

confidence: 99%

NOx Storage and Reduction for Diesel Engine Exhaust Aftertreatment

Pereda-Ayo¹,

González-Velasco²

2013

Diesel Engine - Combustion, Emissions and Condition Monitoring

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“…Elementary surface reactions considered in the literature [3][4][5][6] could be summarized as follows:…”

Section: Mechanism Of the Surface Reactionmentioning

confidence: 99%

“…NO-CO reaction over noble metal catalysts (Pt, Pd, Rh, Ru and Ir) has been widely investigated for several decades since it is an important reaction occurring inside automotive catalytic converters [1][2][3][4][5][6][7]. Among the noble metal catalysts, Rh is the most appropriated catalyst since it has high stability and activity for reduction of NO with low NH 3 formation.…”

Section: Introductionmentioning

confidence: 99%