André Nicolle

ENSTA ParisTech · Department of Chemical Engineering

In the present study, bond formation reactions between soot precursors and their role in the soot inception process are investigated. The soot precursors were generated in macroscopic detailed gas-phase kinetic calculations and according to certain criteria introduced in simulation boxes to model bond formation between soot precursor molecules with...

The reaction of ketene with hydroxyl radical is drawing growing attention, for it is found to be important steps during the combustion of hydrocarbon and oxygenated hydrocarbon fuels, e.g. acetylene, propyne, allene, acetone, gasoline, diesel, jet fuels and biofuels. We studied the potential energy surface (PES) of this reaction using B2PLYP-D3/cc-...

Liquid phase stability is a major concern in the transportation and the energy field where fuels, lubricants and additives have to be stable from their production site to their application (engine, combustors). Although alkanes are major constituents of commercial fuels and well-documented solvents, their respective reactivities and selectivities i...

Selective catalytic reduction (SCR) using Urea-Water Solution (UWS) is a NOx reduction method that many diesel engine manufacturers adopt to meet new regulations for mobile applications (cars, trucks, etc.,) throughout the world. However, this technology still faces many scientific and technological challenges. Indeed, the UWS injected spray can im...

The design of innovative combustion processes relies on a comprehensive understanding of biodiesel oxidation kinetics. The present study aims at unraveling the reaction mechanism involved in the epoxidation of a realistic biodiesel surrogate, methyl trans-3-hexenoate, by hydroperoxy radicals using a bottom-up theoretical kinetics methodology. The o...

A new detailed chemical kinetic mechanism was herein developed to describe accurately the combustion of liquid transportation fuels (gasoline, jet-A1 and diesel fuel) as well as laboratory fuels (single components) over an extended range of equivalence ratios, temperatures, pressures and dilution levels. This mechanism is able to simultaneously rep...

This study aims at validating a multi-scale modeling methodology based on an implicit solvent model for urea thermal decomposition pathways in aqueous solutions. The influence of the number of cooperative water molecules on kinetics was highlighted. The obtained kinetic model is able to accurately reproduce urea decomposition in aqueous phase under...

The addition of molecular oxygen to hydrocarbon radicals yields peroxy radicals (ROO), which are crucial species in both atmospheric and combustion chemistry. For aromatic radicals there is little known about the recombination kinetics, especially for the high temperatures of relevance to combustion. Here, we have employed direct CASPT2 based varia...

Modeling the behavior of catalytic systems at the molecular scale is a matter of importance regarding fundamental understanding, rational design of catalysts and applied chemical engineering. Herein, we propose a multi-scale modeling of experimental kinetic profiles in the case of the dehydration of an alcohol, isopropanol, on γ-alumina catalysts,...

The control of deposit precursors formation resulting from the oxidative degradation of alternative fuels relies strongly on the understanding of the underlying chemical pathways. Although C8-C16 n-alkanes are major constituents of commercial fuels and well-documented solvents, their respective reactivities and selectivities in autoxidation are poo...

Selective catalytic reduction (SCR) using Urea-Water Solution (UWS) is a NOx reduction method that many diesel engine manufacturers adopt to meet new regulations for mobile applications (cars, trucks, etc. ...) throughout the world. However, this technology still faces many scientific and technological challenges. Indeed, the UWS injected spray can...

In this work, unsteady gasification and oxidation of carbonaceous materials with gas-phase combustion under oxy-combustion conditions is studied. An original analytical solution is derived to validate the numerical species boundary condition for the heterogeneous surface reactions with frozen gas-phase. Direct Numerical Simulations accounting for m...

After-treatment systems for diesel vehicles face a challenge for upcoming emission regulations. Regarding the level of nitrogen oxides (NOx) and soot required, the global catalytic activity of the exhaust line needs to be improved. Hydrothermal aging conditions explored during particulate filter regeneration are very stringent for the deNOx catalys...

This experimental and modeling study aimed at better understanding the impact of the operating conditions on the interplay between ammonium nitrate (AN) decomposition pathways and their coupling with gas-phase chemistry. Experimental analysis and kinetic modeling were combined to elucidate the role of operating conditions on ammonium nitrate therma...

The present study extends the Nitrogen Oxide Relaxation Approach (NORA [Vervisch et al., Combust. Flame 158 (2011) 1480–1490]) for NOx modelling in engines by introducing alternative chemical routes to the thermal pathway as well as a speciation of nitrogen oxides into nitrogen monoxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O). Perturba...

Lean NOx Trap (LNT) catalysts, a promising solution for reducing the noxious nitrogen oxide emissions from the lean burn and Diesel engines, are technologically limited by the presence of sulfur in the exhaust gas stream. Sulfur stemming from both fuels and lubricating oils is oxidized during the combustion event and mainly exists as SOx (SO2 and S...

Because of the recent changes in the formulation and handling of middle-distillate fuels, oxidation stability is becoming an increasingly important issue. However, liquid-phase oxidation kinetics of middle-distillate fuels remains poorly understood. The purpose of this study was to gain an in-depth understanding of the impact of fatty acid methyl e...

Environmental concerns as well as economic and political issues triggered major changes in jet fuel formulation and quality including technological evolutions and new (bio) refining processes. These changes have affected fuel oxidative and thermal stability. Complex transport storage and blending logistics can induce fuel pollution lowering the sta...

The present paper presents a multiscale (DFT to mean-field) modeling approach for describing barium sulfate formation through the adsorption of sulfur oxides on BaO. Sulfur oxide emissions, a major environmental concern, also represent one of the technological issues for a large-scale implementation of alkaline-earth oxides as NOx abatement techniq...

A device for mixing and distributing two gases upstream of the catalytic zone of a reactor by producing a homogeneous mixture and a profile of velocities which are as flat as possible. The device uses a plurality of internal chambers (I) enclosed in an external chamber (II), the external chamber communicating with each of the internal chambers via...

Nitrogen oxide (NOx) abatement from lean-burning engines is a major environmental challenge for the upcoming years. With increasing regulations in terms of NOx emission, only sophisticated engine aftertreatment techniques can meet the required emissions. Lean NOx Traps (LNT) are one of those few catalytic techniques that are potential candidates fo...

Among different types of Fe-exchanged zeolites, Fe-BEA exhibits very promising surface properties for developing efficient urea or NH3-SCR systems. In this work, dedicated experimental and kinetic modeling studies were performed in order to elucidate mechanistic aspects related to NH3 storage and release on these catalysts. A series of NH3 adsorpti...

Reducing greenhouse gas emissions to limit global warming is becoming one of the main concern of the aeronautic industry. For example, in Europe, the Advisory Council for Aeronautics Research (ACARE) wishes a reduction of about 50% for the CO2 emissions of air transport before 2020 and about 65% in 20501. For low and medium power applications (<100...

Environmental concerns as well as economic and political issues triggered major changes for Jet fuel including production processes, formulation and logistics in one hand and its application fields with new technological evolutions in the other hand. These changes have affected fuel oxidative and thermal stability. Complex transport storage and ble...

The Selective Catalytic Reduction of nitrogen oxides (NOx) by NH3 is a well established after-treatment technology. The storage of NH3 is a key step of the overall SCR process, affecting the catalyst's deNOx efficiency. In the present study, the storage of NH3 over Fe- and Cu-zeolite based, Urea-SCR catalysts for mobile diesel engines was investiga...

The transition between catalytic and thermal soot oxidation mechanisms is of importance in diesel particulate filters (DPFs). The objective of this study is to develop and validate a new detailed kinetic model predicting reactivity and selectivity of soot oxidation by NOx + O2 over Pt/Ce0.73Zr0.27O2 over a wide range of catalyst/soot (c/s) ratios....

SO(3) -induced surface reconstruction: The SO(3) molecule as a multidentate ligand induces remarkable surface reconstruction phenomena on alkaline earth oxide surface. By using ab initio computations, adsorption properties are derived to elucidate the thermodynamics of the SO(3) -BaO system.

This work is aimed to develop a multicomponent evaporation model for droplets of urea-water solution (UWS) and a thermal decomposition model of urea for automotive exhausts by using the selective catalytic reduction systems. In the multicomponent evaporation model, the influence of urea on the UWS evaporation is taken into account using a nonrandom...

Blends of Fischer–Tropsch (F-T) fuels, biodiesel, and ethanol seem to be a promising fuel for compression ignition (CI) engine applications. An advanced control of current diesel engines requires a detailed comprehension of the fuel chemistry in terms of auto-ignition and pollutant formation. However, neither experimental data, nor convenient combu...

The storage of NH3 over Fe-ZSM5 catalysts was investigated through a multisite approach where the reaction rate expressions are based on the mean-field approximation. A kinetic model, including five different surface sites was formulated from literature data and validated over a broad range of NH3 adsorption and desorption experiments, showing the...

Kinetic parameters for soot oxidation by O2 and NOx are estimated by fitting for product selectivity and global rates. Depending on the gas mixture, the competition of two surface reactions for lumped C*(NO) complexes determines whether N2 or NO2 and CO2 are produced. NO adsorption and soot conversion are much improved when O2 is added to NO becaus...

A kinetic study of the oxidation of carbon materials and an analysis of their differing reactivities are presented. Oxidation experiments of diesel soot and graphite were carried out and kinetics-limited oxidation experiments of graphite and a range of low-mineral graphitic carbons – a carbon black, ethylene flame soot, diesel soot and coke – were...

Detailed kinetic modeling was used to interpret the kinetics of the global CO + O2 reaction in the presence of hydrogen on Pt/Al2O3, Rh/Al2O3, and Pt/Rh/Al2O3 catalysts. The rate parameters were compiled from the literature and optimized to improve the predictivity against multiple experimental data sets. The intrinsic kinetics of CO oxidation in t...

Technical limits of high pressure and temperature measurements as well as hydrodynamic and thermo-diffusive instabilities appearing in such conditions prevent the acquisition of reliable results in term of burning velocities, restraining the domain of validity of current laminar flame speed correlations to few bars and hundreds of Kelvin. These lim...

The modeling of the low temperature oxidation of large saturated methyl esters really representative of those found in biodiesel fuels has been investigated. Models have been developed for these species and then detailed kinetic mechanisms have been automatically generated using a new extended version of software EXGAS, which includes reactions spe...

The kinetics of NOx oxidation and storage were studied over Pt/Al2O3, CexZr1−xO2 and Pt/CeO2. A detailed kinetic mechanism involving lumped nitrate and nitrite species was proposed for the interaction of NOx and O2 with ceria(–zirconia) and its parameters estimated using oxidation and adsorption/desorption experiments. Important trends in the behav...

Following our work on modeling of monolith catalysts [1], we herein focus on developing a fixed-bed reactor model in the AMESim modeling platform. A kinetic model for NO oxidation and NOx storage over Pt/Ba/Al2O3 recently developed in the literature was successfully implemented and validated against the experimental data available in the previous w...

The concept of nitrogen oxide storage-reduction (NSR) is a promising aftertreatment technology for reducing NOx emissions from lean-burn engine exhaust. The present work focuses on the first two steps of the overall NSR mechanism, namely, NO to NO2 oxidation and NOx storage. The governing storage mechanisms are mainly elucidated on the model cataly...

The effect of the natural gas to H2 ratio on the flame structure and NOx formation in lean premixed porous combustion was determined by combining Comsol and Premix codes. The thermal pathway was of secondary importance while the NNH, N2O and prompt pathways were the most important routes involved in NO formation. H2 enrichment resulted in the penet...

A numerical study of the diluted oxidation of CH4 was performed to investigate the potential importance of the NO-reburning mechanism in conditions relevant to MILD combustion. It turns out that the NO–HCN conversion reactions are particularly active before auto-ignition. During this period, the nitrogen contained initially in NO is stored in HCN a...

New experimental results were obtained for the mutual sensitization of the oxidation of NO and ethane and NO and ethylene in fuel-lean conditions. An atmospheric fused-silica jet-stirred reactor operating over the temperature range 700–1150 K was used. The initial carbon mole fraction was 2500 ppm whereas that of NO varied from 0 to 1200 ppm. Sonic...

The effect of mutual sensitization of the oxidation of nitric oxide and methane was investigated. Probe sampling with online Fourier transform infrared spectroscopy (FTIR) analysis and off-line GC-TCD/FID analysis were used to measure concentration profiles for the reactants, stable intermediates and final products. The mutual sensitization of the...

New experimental results were obtained for the mutual sensitization of the oxidation of NO and methane in a fused silica jet-stirred reactor operating at 1–10 atm, over the temperature range 800–1150 K. Probe sampling followed by on-line FTIR analyses and off-line GC-TCD/FID analyses allowed the measurement of concentration profiles for the reactan...

The reduction of CO, CO2, and NOx emissions from combustion in gas turbines can be achieved using hydrogen-enriched fuels operation under very fuel-lean conditions where the emission of NOx is strongly reduced. New experimental results were obtained for the kinetic of oxidation of hydrogen–natural gas mixtures in a fused silica jet-stirred reactor...

The effect of SO2 addition on the reduction of NO by ammonia in simulated thermal de-NOx conditions was studied in a JSR at atmospheric pressure for various equivalence ratios (0.1–2) and initial concentrations of NO, NH3, and SO2 (0–1000 ppm). The experiments were performed at fixed residence times of 100 and 200 ms, and variable temperature, rang...

There is interest studying the kinetics of hydrogen-hydrocarbons mixtures since the combustion of hydrogen-enriched fuels under fuel-lean conditions in gas turbines could help reducing the emissions of CO, CO 2 and NOx. New experimental results were obtained for the kinetic of oxidation of hydrogen-natural gas mixtures in a fused silica jet-stirred...

Experimental results, consisting of mole fraction profiles versus temperature, were obtained for the mutual sensitization of the oxidation of NO and methane, ethane, ethene and NO in fuel-lean conditions. A fused silica jet-stirred reactor operating at constant residence time over the temperature range 700-1150 K, 1-10 atm was used. The initial car...