Micro-Kinetic Study of Reduction of NO on Pt Group Catalysts

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Dinesh B Mantri ◽  
Preeti Aghalayam
Keyword(s):  
Reaction Mechanism ◽  
Surface Coverage ◽  
No Reduction ◽  
Catalytic Reduction ◽  
Effect Of Temperature ◽  
Exponential Potential ◽  
Reactor Model ◽  
Reduction Activity ◽  
Stirred Reactor ◽  
High Durability

Catalytic reduction using CO has significant potential for the control of NOx using Pt group catalysts as CO is already present in the exhausts and Pt group catalysts have high durability in the presence of SO2 and H2O. Different reaction mechanisms are given in the literature for this reaction based on NO dissociation, -NCO formation and so on, but the exact reaction mechanism capable of capturing experimentally observed features is as yet unavailable. To determine the kinetics and reaction mechanism, we propose here an elementary reaction mechanism based on NO dissociation applicable to Pt group catalysts and simulated with CHEMKIN 4.0.2 using single and multiple PSR (Perfectly Stirred Reactor) model. The activation energies of the elementary steps are found from the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. Excellent agreement between literature experiments and our simulation results are observed for the NO-CO reaction on Pt and Rh catalysts and for the NO-CO-O2 reaction on Ir catalyst. The effect of temperature on the NO reduction activity is captured well by the model. Additionally the simulations can also point towards importance of particular reactions, selectivity to N2, effects of surface coverage, effects of residence time and catalytic surface area on NO reduction.

Mechanistic insight into the influence of O2 on N2O formation in the selective catalytic reduction of NO with NH3 over Pd/CeO2 catalyst

2021 ◽  
Author(s):  
Liping Sheng ◽  
Songda Li ◽  
Zhaoxia Ma ◽  
Fei Wang ◽  
Hu He ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
No Reduction ◽  
Catalytic Reduction ◽  
Temperature Dependent ◽  
N2o Formation ◽  
Reduction Of No ◽  
Mechanistic Insight ◽  
Insight Into

O2 greatly affected the pathway for NO reduction over the Pd/CeO2 catalyst and resulted in a temperature-dependent NH3-SCR performance and formation of N2O.

A Multidisciplinary Approach for the Comprehensive Assessment of Integrated Rotorcraft–Powerplant Systems at Mission Level

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Ioannis Goulos ◽  
Fakhre Ali ◽  
Konstantinos Tzanidakis ◽  
Vassilios Pachidis ◽  
Roberto d'Ippolito
Keyword(s):  
Environmental Impact ◽  
Fuel Consumption ◽  
Comprehensive Assessment ◽  
Pollutant Emissions ◽  
Operational Performance ◽  
Civil Aviation ◽  
Accurate Estimation ◽  
Nox Emissions ◽  
Reactor Model ◽  
Stirred Reactor

This paper presents an integrated methodology for the comprehensive assessment of combined rotorcraft–powerplant systems at mission level. Analytical evaluation of existing and conceptual designs is carried out in terms of operational performance and environmental impact. The proposed approach comprises a wide-range of individual modeling theories applicable to rotorcraft flight dynamics and gas turbine engine performance. A novel, physics-based, stirred reactor model is employed for the rapid estimation of nitrogen oxides (NOx) emissions. The individual mathematical models are implemented within an elaborate numerical procedure, solving for total mission fuel consumption and associated pollutant emissions. The combined approach is applied to the comprehensive analysis of a reference twin-engine light (TEL) aircraft modeled after the Eurocopter Bo 105 helicopter, operating on representative mission scenarios. Extensive comparisons with flight test data are carried out and presented in terms of main rotor trim control angles and power requirements, along with general flight performance charts including payload-range diagrams. Predictions of total mission fuel consumption and NOx emissions are compared with estimated values provided by the Swiss Federal Office of Civil Aviation (FOCA). Good agreement is exhibited between predictions made with the physics-based stirred reactor model and experimentally measured values of NOx emission indices. The obtained results suggest that the production rates of NOx pollutant emissions are predominantly influenced by the behavior of total air inlet pressure upstream of the combustion chamber, which is affected by the employed operational procedures and the time-dependent all-up mass (AUM) of the aircraft. It is demonstrated that accurate estimation of on-board fuel supplies ahead of flight is key to improving fuel economy as well as reducing environmental impact. The proposed methodology essentially constitutes an enabling technology for the comprehensive assessment of existing and conceptual rotorcraft–powerplant systems, in terms of operational performance and environmental impact.

scholarly journals Kinetics of Selective Catalytic Reduction of Nitric Oxide over Pt-Cu-Zsm5 Catalyst

1970 ◽  
Vol 4 (1) ◽  
Author(s):  
Ismail Mohd Saaid ◽  
Abdul Rahman Mohamed and Subhash Bhatia
Keyword(s):  
Nitric Oxide ◽  
Selective Catalytic Reduction ◽  
Active Sites ◽  
No Reduction ◽  
Bimetallic Catalyst ◽  
Catalytic Reduction ◽  
Covalent Bond ◽  
Reaction Parameters ◽  
Heterogeneous Model ◽  
Kinetics Of

Kinetics for the selective catalytic reduction (SCR) of nitric oxide (NO) using i-C4H10 as the reducing agent over Pt-Cu-ZSM5 has been investigated in the temperature range of 200 ?C – 450 oC. Langmuir-Hinshelwood-Hougen-Watson model was proposed for kinetics of the reaction and reaction parameters were evaluated.  The heat of adsorption of NO was found to be considerably high, attributed to strong covalent bond between NO gas molecules and metal active sites.  Using reaction parameters obtained from the experiment, the heterogeneous model could form a good correlation between experimental and simulated values of NO reduction. Key Words: Reaction kinetics, Selective catalytic reduction, NO reduction, Bimetallic catalyst, H-ZSM-5 zeolite.

scholarly journals A review of Mn-containing oxide catalysts for low temperature selective catalytic reduction of NOx with NH3: reaction mechanism and catalyst deactivation

RSC Advances ◽  
2017 ◽  
Vol 7 (42) ◽  
pp. 26226-26242 ◽  
Author(s):  
Shengen Zhang ◽  
Bolin Zhang ◽  
Bo Liu ◽  
Shuailing Sun
Keyword(s):  
Reaction Mechanism ◽  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Catalyst Deactivation ◽  
Catalytic Reduction ◽  
Oxide Catalysts ◽  
Scr Catalysts ◽  
Reduction Of Nox

The reactions over Mn-containing selective catalytic reduction (SCR) catalysts.

From the Understanding of the Reaction Mechanism Towards Optimizing the Deposition Rate and Optoelectronic Properties of a-Si:H

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Veprek ◽  
M. Heintze ◽  
R. Bayer ◽  
N. Jurčik-Rajman
Keyword(s):  
Reaction Mechanism ◽  
Surface Coverage ◽  
Kinetic Studies ◽  
Reactive Intermediates ◽  
Sticking Coefficient ◽  
High Quality ◽  
Rate Determining Step ◽  
Homogeneous Good ◽  
Good Agreement

ABSTRACTWe present new results of kinetic studies of the deposition of high quality a-Si:H which strongly support the reaction mechanism suggested in our earlier papers: 1. SiH4 → SiH2; 2. SiH2 + SiS4 → Si2H6 (SiH2 + Si2H6 → Si3H6); 3. Si2H6 → 2a-Si:H (Si3H8 → 3a-Si:H). The “SiH3 mechanism”, as promoted by several workers, is in contradiction with these experimental facts.The di- and trisilane, which have a much higher reactive sticking coefficient than monosilane, play the role of reactive intermediates which facilitate the heterogeneous decomposition of silicon carrying species at the surface of the growing film. The values of the reactive sticking coefficient of Si2H6 and Si3H8 depend on the surface coverage by chemisorbed hydrogen; they increase with decreasing surface coverage. Under the conditions of the growth of high quality a-Si:H films the reactive sticking coefficient of disilane amounts to 10−4 to 10−2 which is in a good agreement with recent data of other authors.The rate determining step of the growth of high quality a-Si:H films is the desorption of hydrogen from the surface of the growing film. This can be strongly enhanced by ion bombardment at impact energy of <100 eV. In this way, homogeneous, good quality films were deposited at rates up to 1800 Angströms/min, and there is a well justified hope that this rate can be further increased.

scholarly journals Study on Designing Sulfur Containing Bifunctional Building Block with Improved Refractive Index

2009 ◽  
Vol 6 (2) ◽  
pp. 399-411 ◽  
Author(s):  
G. S. Jha ◽  
P. Chhabra ◽  
G. Suri ◽  
M. Tyagi ◽  
P. Arora ◽  
...  
Keyword(s):  
Refractive Index ◽  
Reaction Mechanism ◽  
Reaction Time ◽  
Acid Number ◽  
Effect Of Temperature ◽  
Control Parameters ◽  
Reaction Parameters ◽  
Factors Affecting ◽  
Temperature Rate ◽  
Sulfur Containing

Sulfur and chlorine containing bifunctional diols with C-S bond has been prepared starting from chloroepoxy alkane and thioalcohol. The studies of FTIR, TLC, HPLC and NMR have been used to understand the reaction mechanism, as well as for optimization of the reaction parameters. The reaction is highly exothermic and the effect of temperature, rate of addition of reagents and reaction time are important factors affecting the formation of diol. Viscosity studies, HPLC, FTIR, NMR and acid number studies have shown that, these parameters could be used as process control parameters for the synthesis of diol. Refractive index of the synthesized diol is found to be higher than that of the reactants used.

Coherent Flame Model to Predict Formation Pollutants in Turbulent Premixed Flame

2010 ◽  
Author(s):  
Abdelhalim Bentebbiche ◽  
Denis Veynante
Keyword(s):  
Kinetic Scheme ◽  
Turbulent Flames ◽  
Premixed Flame ◽  
Reactive Flow ◽  
Reactor Model ◽  
Turbulent Premixed Flame ◽  
No Formation ◽  
Stirred Reactor ◽  
Good Issue ◽  
Turbulent Premixed

The objective of this work is to analyze and to model the turbulent flames in the context of coherent flame model. We present a detailed description of equations and the flamelet regimes in turbulent premixed flame. A surface density models proposed here represents a good issue for numerical simulation. Extension of coherent flame model and homogenous stilled reactor model is proposed to consider the dynamics behavior of flame and pollutants formation. From the results of this work it is concluded that the coherent flame model allows surpassing difficulties of the turbulent reactive flow modeling. Calculations based on a semi-global kinetic scheme and flamelet formulation combined with a well stirred reactor analysis of the burnt gases are used and provided reasonably accurate values of CO and NO formation. Also, we have observed that CO is formed near the reaction zone (front flame) but emission of CO2, H2O and NO are formed in the hot gases.

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