Selective reduction of NOx by hydrocarbons in excess oxygen by alumina- and silica-supported catalysts

Burch, Robbie; Millington, Paul

doi:10.1016/0920-5861(95)00257-x

Cited by 98 publications

(62 citation statements)

References 7 publications

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“…The rates for NO reduction over the (111) facets were found to be zero over all particle sizes. The results here clearly show that there is structure sensitivity for NO reduction reaction which is consistent with experimental results by Burch and Millingston, 53 Demicheli, 1 and Denton.…”

Section: Facet-dependent Kineticssupporting

confidence: 81%

First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions

Mei

Neurock

2010

Ind. Eng. Chem. Res.

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The kinetics for NO reduction over supported platinum under lean condition were investigated by firstprinciples-based kinetic Monte Carlo simulation over three-dimensional Pt nanoparticles. Model platinum nanoparticles with diameters ranging from 2.3 to 4.6 nm were constructed using a truncated octahedral cluster consisting of a two (100) facets and eight (111) facets. First-principles density functional theory (DFT) calculations were used to calculate the intrinsic kinetic parameters including the binding energies for all of the surface intermediates as well as the activation barriers and reaction energies that comprise the reaction mechanism over the (100) and (111) facets, as well as the (111)/(100) edge sites on the three-dimensional nanoparticle. Both intra-and inter-facet diffusion of adsorbates were included to model surface diffusion effects over the particle surface. The simulation results show that under lean conditions where there is excess oxygen, NO reduction to N 2 occurs solely on the (100) facets. The oxidation of NO to NO 2 , while much more favored on the (111) facets, can occur on both (100) and (111) facets. Only small amounts of N 2 O form over the (100) facets. The simulated apparent activation energies for N 2 and NO 2 formation over the entire particle are 45 and 42 kJ/mol, respectively. The latter is in agreement with experimentally measured value of 39 kJ/mol [Mulla, S. S., et al., Catal. Lett. 2005, 100, 267]. The effects of particle size on the activities of NO reduction to N 2 and NO oxidation to NO 2 depend upon the ratios of exposed surface sites. For the threedimensional model Pt nanoparticles examined here, the fractions of the (100) terrace sites are similar while the fraction of the (111) terrace sites increases with increasing particle size. As a result, the activity for NO reduction is somewhat insensitive to the particle size which symmetrically increases the numbers of (111) and (100) facets as the size increases. NO reduction, however, increases much more dramatically when the number of the (100) sites increases over the (111) sites. NO oxidation activity, on the other hand, appears to increase with increasing particle size regardless of the symmetry or shape of the particle as the reaction occurs predominantly over the (111) sites but can also take place on the (100) terrace sites. The structure insensitivity for NO oxidation is consistent with experimental results.

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Section: Facet-dependent Kineticssupporting

confidence: 81%

First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions

Mei

Neurock

2010

Ind. Eng. Chem. Res.

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“…This suggests that NO gas is partly reduced to N 2 O and N 2 , and that the O from the catalyst surface might be consumed to oxidize the incoming C 3 H 6 gas to generate CO 2 . This is exactly how HC-SCR catalysts are supposed to function via a redox process (Burch and Millington, 1996). A dramatic change is observed in every gas species when the temperature is increased further to 250°C: a sudden disappearance of C 3 H 6 , associated with a huge increase in CO 2 peak, a relatively large decrease in NO peak height, a noticeable increase of NO 2 peak, and a sudden stop to change in N 2 O peak.…”

Section: Test For Catalytic Activity Of No Reductionmentioning

confidence: 90%

“…In an attempt to resolve the issue of thermal stability, namely that Pt particles are easily sintered into large sizes, thereby significantly changing their behavior and catalytic performance (Suzuki et al, 2010), supporting materials such as silica and alumina have been introduced (Gonzalez et al, 1997;Nagai et al, 2006). As an example, Burch et al (1996) reported that the maximum conversion of NO for Pt/SiO 2 and Pt/Al 2 O 3 catalysts reached 75% and 60%, respectively. Furthermore, such metal oxide supports are known to lower the working temperatures of Pt catalysts and minimize the undesirable corrosion effect of water vapor and sulfur oxides (SO x ) (Burch and Watling, 1997;Gonzalez et al, 1997;Männikkö et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…In this prospect, developing various catalysts for HC-SCR has been an intensive research area, which was initiated by Iwamoto et al in 1990(Iwamoto, 1990Jayat et al, 1999). Then, Burch (Burch and Millington, 1995;Burch and Millington, 1996;Burch and Watling, 1997;Burch et al, 2002;Burch, 2004) performed a series of pioneering investigations for revealing catalytic performance and reaction kinetics of HC-SCR catalysts. Among various formulations of catalysts including Ag, Pd, Co, Ni, Au, Rh, and Cu, Pt-based catalysts showed excellent performance for NO x reduction at relatively low temperatures (Burch andMillington, 1995, 1996;Burch and Watling, 1997;Jayat et al, 1999;Burch et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Pt Catalyst over SiO2 and Al2O3 Supports Synthesized by Aerosol Method for HC-SCR DeNOx Application

Zahaf

Jung

Coker

et al. 2015

Aerosol Air Qual. Res.

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“…Because Pt-based catalysts are active at relatively low temperatures for active lean-NOx catalysis, numerous studies have identified these materials as excellent candidates for light-(and medium-) duty diesel exhaust applications [6][7][8][9][10][11][12]. This study will examine novel hydrous metal oxide-supported Pt catalysts for active lean-NOx catalysis.…”

Section: Introductionmentioning

confidence: 99%

Preparation Effects on the Performance of Silica-Doped Hydrous Titanium Oxide (HTO:Si)-Supported Pt Catalysts for Lean-Burn NOx Reduction by Hydrocarbons

Gardner¹,

McLaughlin²,

Mowery³

et al. 2002

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This report describes the development of bulk hydrous titanium oxide (HTO)-and silicadoped hydrous titanium oxide (HTO:Si)-supported Pt catalysts for lean-burn NOx catalyst applications. The effects of various preparation methods, including both anion and cation exchange, and specifically the effect of Na content on the performance of Pt/HTO:Si catalysts, were evaluated. Pt/HTO:Si catalysts with low Na content (< 0.5 wt.%) were found to be very active for NOx reduction in simulated lean-burn exhaust environments utilizing propylene as the major reductant species. The activity and performance of these low Na Pt/HTO:Si catalysts were comparable to supported Pt catalysts prepared using conventional oxide or zeolite supports. In ramp down temperature profile test conditions, Pt/HTO:Si catalysts with Na contents in the range of 3-5 wt.% showed a wide temperature window of appreciable NOx conversion relative to low Na Pt/HTO:Si catalysts. Full reactant species analysis using both ramp up and isothermal test conditions with the high Na Pt/HTO:Si catalysts, as well as diffuse reflectance FTIR studies, showed that this phenomenon was related to transient NOx storage effects associated with NaNO 2 /NaNO 3 formation. These nitrite/nitrate species were found to decompose and release NOx at temperatures above 300°C in the reaction environment (ramp up profile). A separate NOx uptake experiment at 275°C in NO/N 2 /O 2 showed that the Na phase was inefficiently utilized for NOx storage. Steady state tests showed that the effect of increased Na content was to delay NOx light-off and to decrease the maximum NOx conversion. Similar results were observed for high K Pt/HTO:Si catalysts, and the effects of high alkali content were found to be independent of the sample preparation technique. Catalyst characterization (BET surface area, H 2 chemisorption, and transmission electron microscopy) was performed to elucidate differences between the HTO-and HTO:Sisupported Pt catalysts and conventional oxide-or zeolite-supported Pt catalysts.4

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Selective reduction of NOx by hydrocarbons in excess oxygen by alumina- and silica-supported catalysts

Cited by 98 publications

References 7 publications

First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions

First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions

Pt Catalyst over SiO2 and Al2O3 Supports Synthesized by Aerosol Method for HC-SCR DeNOx Application

Preparation Effects on the Performance of Silica-Doped Hydrous Titanium Oxide (HTO:Si)-Supported Pt Catalysts for Lean-Burn NOx Reduction by Hydrocarbons

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