Role of the Nature of the Support (Alumina or Silica), of the Support Porosity, and of the Pt Dispersion in the Selective Reduction of NO by C3H6 under Lean-Burn Conditions

Denton, Patricia; Giroir‐Fendler, A.; Praliaud, H.; Primet, Michel

doi:10.1006/jcat.1999.2708

Cited by 99 publications

(28 citation statements)

References 41 publications

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“…1 were prepared on silicas with different surface area, the metal loadings were compared on the basis of Pt surface density (µmol/m 2 ). While there are only a few examples of catalysts calcined at higher temperatures, at the same Pt surface density, catalysts calcined below 300 • C generally have higher dispersions [2,3,5,7,8,11,16,17,19].…”

Section: Introductionmentioning

confidence: 97%

“…DI of PTA gives higher dispersions than those prepared from CPA, about 0.6-0.9 with higher dispersions at lower Pt loading [6,21]. Preparation of Pt on silica by WI with PTA, i.e., near neutral pH, also gives dispersions, which are moderate to low, generally about 0.3-0.5 [1,14,17]. The highest dispersions are achieved by SEA of PTA; i.e., the pH remains high throughout the metals deposition.…”

Section: Introductionmentioning

confidence: 98%

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A fundamental study of platinum tetraammine impregnation of silica2. The effect of method of preparation, loading, and calcination temperature on (reduced) particle size

Miller¹

2004

Journal of Catalysis

164

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

A fundamental study of platinum tetraammine impregnation of silica2. The effect of method of preparation, loading, and calcination temperature on (reduced) particle size

Miller¹

2004

Journal of Catalysis

164

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“…Conversely, SCR is a continuous process. It is described as an attractive way to reduce NOx in excess of O2, with the possible use of a large choice of reductants like hydrocarbons (HC) [3][4][5][6][7][8], ammonia [9][10][11][12], urea [13], hydrogen, alcohol [14,15], etc. While HC-SCR has been largely studied in the past decades for automotive applications, the NH3-SCR is now accepted as exhibiting the highest potential to reduce NOx emission in the lean condition, with different reaction pathways described by Equations (1)- (3).…”

Section: Introductionmentioning

confidence: 99%

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

et al. 2015

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Abstract:The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars requires the use of an ammonia precursor, provided by a urea aqueous solution in the conventional process. Although the thermal decomposition and hydrolysis mechanisms of urea are well documented in the literature, the influence of the direct use of urea on the NOx reduction over SCR catalysts may be problematic. With the aim to evaluate prototype powdered catalysts, a specific synthetic gas bench adjusted to powdered material was developed, allowing the use of NH3 or urea as reductant for direct comparison. The design of the experimental setup allows vaporization of liquid urea at 200 °C under 10 bar using an HPLC pump and a micro injector of 50 μm diameter. This work presents the experimental setup of the catalytic test and some remarkable catalytic results towards further development of new catalytic formulations specifically dedicated to urea-SCR. Indeed, a possible divergence in terms of DeNOx efficiency is evidenced depending on the nature of the reductant, NH3 or urea solution. Particularly, the evaluated catalyst may not allow an optimal NOx conversion because of a lack in ammonia availability when the urea residence time is shortened. This is attributed to insufficient activity of isocyanic acid (HNCO) hydrolysis, OPEN ACCESSCatalysts 2015, 5 1536 which can be improved by addition upstream of an active solid for the hydrolysis reaction such as ZrO2. Thus, this µ-scale synthetic gas bench adjusted to powdered materials enables the specific behaviour of urea use for NOx reduction to be demonstrated.

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“…While there have been a number of important studies on the factors that control NO reduction and oxidation, [1][2][3][4] there are still a number of unanswered questions concerning the mechanisms by which these reactions proceed and the influence of Pt particle size and structure.…”

Section: Introductionmentioning

confidence: 99%

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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Role of the Nature of the Support (Alumina or Silica), of the Support Porosity, and of the Pt Dispersion in the Selective Reduction of NO by C3H6 under Lean-Burn Conditions

Cited by 99 publications

References 41 publications

A fundamental study of platinum tetraammine impregnation of silica2. The effect of method of preparation, loading, and calcination temperature on (reduced) particle size

A fundamental study of platinum tetraammine impregnation of silica2. The effect of method of preparation, loading, and calcination temperature on (reduced) particle size

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

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

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