Dual-catalyst system to broaden the window of operability in the reduction of nitrogen oxides (NOx) with ammonia

1989 ◽  
Vol 28 (8) ◽  
pp. 1171-1177 ◽  
Author(s):  
F. G. Medros ◽  
J. W. Eldridge ◽  
J. R. Kittrell
Keyword(s):  
Nitrogen Oxides ◽  
Catalyst System

scholarly journals CATALYSTS TO TREAT POLLUTION GASES OF THE INCINERATORS

2011 ◽  
Vol 14 (1) ◽  
pp. 16-23
Author(s):  
Lu Van Le ◽  
Tiep Van Le
Keyword(s):  
Nitrogen Oxides ◽  
Combustion Process ◽  
Catalyst System ◽  
Medical Waste ◽  
Treatment System ◽  
Oxidation Catalyst ◽  
Good Prospect ◽  
Toxic Gases ◽  
Study Results

Incineration is a useful way to treat industrial and medical waste. However, the combustion process in the incinerators can produce many toxic gases like nitrogen oxides (NOx), monoxide carbon (CO), hydro cacbon (HC). In this paper we present the study and design of the deNOx and oxidation catalyst system, which can be used to treat pollution gases NOx, CO, HC that are produced in the incinerators. The study results show good prospect for applying the treatment system in Vietnam industry.

Catalyst system for the reduction of nitrogen oxides in diesel exhaust

Zeolites ◽  
1997 ◽  
Vol 18 (2-3) ◽  
pp. 234
Author(s):  
G. Schenkermayr ◽  
H. Eichiseder
Keyword(s):  
Nitrogen Oxides ◽  
Diesel Exhaust ◽  
Catalyst System

scholarly journals Mechanistic Studies of Catalytic Reduction of Nitrogen Oxides from Diesel Engine Exhaust over Manganese and Cerium Oxide Based Catalysts

2021 ◽  
pp. 40-50
Author(s):  
Russel C. L. De Silva ◽  
Darrell P. Eyman
Keyword(s):  
Nitrogen Oxides ◽  
Catalytic Reduction ◽  
Selective Reduction ◽  
Catalyst System ◽  
Mechanistic Studies ◽  
Engine Exhaust ◽  
Catalytic Sites ◽  
Selective Reduction Of Nox ◽  
Reduction Of Nox ◽  
Cerium Catalysts

Finding a catalyst system that is effective and consistent for the selective reduction of NOx during lean exhaust conditions has been a predominant challenge to both industrial and research institutions, despite the large number of reported catalysts tested. The selective catalytic reduction of NO + NO2 (NOx) with CO and C3 hydrocarbons at low temperatures (175-225 oC) is investigated over manganese and cerium catalysts with and without the presence of a precious metal. 1% Pt/Mn/Al catalysts show promising results for the reaction, with continuous NOx conversions well more than 35% in the period extending beyond 170 hours. The synthesis technique of the catalyst and the reaction temperature greatly effects the reaction. There is no evidence of the presence of other nitrogen oxides in the products except for a very small quantity of N2O only at the beginning of the reaction. Mechanistic studies reveal manganese to be the major catalytic sites, while the platinum plays a secondary role. Mn/Ce/Al also show continuous deNOx activity with NOx conversions of 28-35%.

WET BURNING – THE MODERN TREND IN ENVIRONMENTAL BENIGN FUEL COMBUSTION AND IN SOLUTION TO THE PROBLEM OF SUSTAINABLE DEVELOPMENT OF THE POWER GENERATION

2018 ◽  
pp. 96-117 ◽  
Author(s):  
B. S. Soroka
Keyword(s):  
Numerical Simulation ◽  
Nitrogen Oxides ◽  
Chemical Kinetics ◽  
Fuel Combustion ◽  
Transport Processes ◽  
Cfd Modeling ◽  
Furnace Chamber ◽  
Modern Trend ◽  
Atmospheric Air ◽  
No Formation

The article considers the role and place of water and water vapor in combustion processes with the purpose of reduction the effluents of nitrogen oxides and carbon oxide. We have carried out the complex of theoretical and computational researches on reduction of harmful nitrogen and carbon oxides by gas fuel combustion in dependence on humidity of atmospheric air by two approaches: CFD modeling with attraction of DRM 19 chemical kinetics mechanism of combustion for 19 components along with Bowman’s mechanism used as “postprocessor” to determine the [NO] concentration; different thermodynamic models of predicting the nitrogen oxides NO formation. The numerical simulation of the transport processes for momentum, mass and heat being solved simultaneously in the united equations’ system with the chemical kinetics equations in frame of GRI methane combustion mechanism and NO formation calculated afterwards as “postprocessor” allow calculating the absolute actual [CO] and [NO] concentrations in dependence on combustion operative conditions and on design of furnace facilities. Prediction in frame of thermodynamic equilibrium state for combustion products ensures only evaluation of the relative value of [NO] concentration by wet combustion the gas with humid air regarding that in case of dry air – oxidant. We have developed the methodology and have revealed the results of numerical simulation of impact of the relative humidity of atmospheric air on harmful gases formation. Range of relative air humidity under calculations of atmospheric air under impact on [NO] and [CO] concentrations at the furnace chamber exit makes φ = 0 – 100%. The results of CFD modeling have been verified both by author’s experimental data and due comparing with the trends stated in world literature. We have carried out the complex of the experimental investigations regarding atmospheric air humidification impact on flame structure and environmental characteristics at natural gas combustion with premixed flame formation in open air. The article also proposes the methodology for evaluation of the nitrogen oxides formation in dependence on moisture content of burning mixture. The results of measurements have been used for verification the calculation data. Coincidence of relative change the NO (NOx) yield due humidification the combustion air revealed by means of CFD prediction has confirmed the qualitative and the quantitative correspondence of physical and chemical kinetics mechanisms and the CFD modeling procedures with the processes to be studied. A sharp, more than an order of reduction in NO emissions and simultaneously approximately a two-fold decrease in the CO concentration during combustion of the methane-air mixture under conditions of humidification of the combustion air to a saturation state at a temperature of 325 K.

Direct Observation of Chain Lengths and Conformations in Oligofluorene Distributions from Controlled Polymerization by Double Electron-Electron Resonance

2019 ◽  
Author(s):  
Dennis Bücker ◽  
Annika Sickinger ◽  
Julian D. Ruiz Perez ◽  
Manuel Oestringer ◽  
Stefan Mecking ◽  
...  
Keyword(s):  
Chain Length ◽  
Length Distribution ◽  
Catalyst System ◽  
Chain Conformation ◽  
Controlled Polymerization ◽  
Chain Length Distribution ◽  
Electron Resonance ◽  
Double Electron ◽  
The Individual ◽  
Double Electron Electron Resonance

Synthetic polymers are mixtures of different length chains, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.

Mechanistic Insights into Fe Catalyzed α-C-H Oxidations of Tertiary Amines

2019 ◽  
Author(s):  
Christopher J. Legacy ◽  
Frederick T. Greenaway ◽  
Marion Emmert
Keyword(s):  
Free Radical ◽  
Catalytic Mechanism ◽  
Catalyst System ◽  
Oxidation Products ◽  
Tertiary Amines ◽  
Catalyst Activation ◽  
Rate Determining Step ◽  
Fe Catalyst ◽  
Ligand Coordination ◽  
Rate Kinetics

We report detailed mechanistic investigations of an iron-based catalyst system, which allows the α-C-H oxidation of a wide variety of amines, including acyclic tertiary aliphatic amines, to afford dealkylated or amide products. In contrast to other catalysts that affect α-C-H oxidations of tertiary amines, the system under investigation employs exclusively peroxy esters as oxidants. More common oxidants (e.g. tBuOOH) previously reported to affect amine oxidations via free radical pathways do not provide amine α-C-H oxidation products in combination with the herein described catalyst system. Motivated by this difference in reactivity to more common free radical systems, the investigations described herein employ initial rate kinetics, kinetic profiling, Eyring studies, kinetic isotope effect studies, Hammett studies, ligand coordination studies, and EPR studies to shed light on the Fe catalyst system. The obtained data suggest that the catalytic mechanism proceeds through C-H abstraction at a coordinated substrate molecule. This rate-determining step occurs either at an Fe(IV) oxo pathway or a 2-electron pathway at a Fe(II) intermediate with bound oxidant. We further show via kinetic profiling and EPR studies that catalyst activation follows a radical pathway, which is initiated by hydrolysis of PhCO3 tBu to tBuOOH in the reaction mixture. Overall, the obtained mechanistic data support a non-classical, Fe catalyzed pathway that requires substrate binding, thus inducing selectivity for α-C-H functionalization.<br>

Considerations on Ambient Levels of Ozone Concentrations and Relationship with NOx in an Urban Environment

2017 ◽  
Vol 68 (4) ◽  
pp. 824-829
Author(s):  
Cornel Ianache ◽  
Laurentiu Predescu ◽  
Mirela Predescu ◽  
Dumitru Dumitru
Keyword(s):  
Nitrogen Oxides ◽  
Urban Areas ◽  
Road Traffic ◽  
Temporal Distribution ◽  
Ground Level ◽  
Distinct Pattern ◽  
Weekend Effect ◽  
Monitoring Site ◽  
Ground Level Ozone ◽  
Ozone Concentrations

The serious air pollution problem has determined public concerns, worldwide. One of the main challenges for countries all over the world is caused by the elevated levels of ground-level ozone (O3) concentrations and its anthropogenic precursors. Ploiesti city, as one of the major urban area of Romania, is facing the same situation. This research aims to investigate spatial and temporal distribution characteristics of O3 in relationship with nitrogen oxides (NOx) using statistical analysis methods. Hourly O3 and NOx measurements were collected during 2014 year in Ploiesti. The results obtained showed that the ozone spatial distribution was non-normal for each month in 2014. The diurnal cycle of ground-level ozone concentrations showed a mid-day peak, while NOx diurnal variations presented 2 daily peaks, one in the morning (7:00 a.m.) and one in the afternoon (between 5:00 and 7:00 p.m.). In addition, it was observed a distinct pattern of weekly variations for O3 and NOx. Like in many other urban areas, the results indicated the presence of the �ozone weekend effect� in Ploiesti during the 2014 year, ozone concentrations being slightly higher on weekends compared to weekdays. For the same monitoring site, the nitrogen oxides were less prevalent on Saturdays and Sundays, probably due to reducing of road traffic and other pollution-generating activities on weekends than during the week.

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