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Publications (124)
Increasingly stricter regulations for vehicle emissions require more competitive exhaust emission control systems. Three-way catalysis is a major up-to-date emission control technology, though the activity could be limited during the cold start as well as steady state operation including the three regimes: rich (λ<1), lean (λ>1), and stoichiometric...
The powerful combination of steady state isotopic transient kinetic analysis (SSITKA) and operando infrared spectroscopy (IR) was applied to study the CO oxidation reaction on Pd-supported Al2O3 catalyst at low temperature. The aim was to reveal the true role of hydrogen‑carbonate species in the reaction mechanism. The SSITKA-IR experiments, conduc...
The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm² and 9.5W/nm²) and different surface V density varying in the range 1–8V/nm² has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was...
The catalytic oxidation of CO by O2 to form CO2 over Pt based catalysis is one of the most studied catalytic reaction leading to controversial mechanism descriptions. Steady State Isotopic Transient Kinetic Analysis (SSITKA) coupled with InfraRed (IR) spectroscopy is a powerful technique to study heterogeneous reaction mechanisms combining both the...
Exhaust car emissions increase significantly at particular gasoline engine driving cycle such as cold-start when the three-way catalyst has not reached its light-off temperature. More efficient technologies are needed to reduce these extra emissions. This study focuses on comparing two strategies to lower cold-start pollutants on a commercial monol...
This research presents a novel approach for developing noble metal-free three-way catalysts by using ZnAl layered double hydroxide (LDH) co-precipitated with Mn and Ti. Cu was added as the catalytically active metal. Two methods were explored, namely the addition of Cu during the co-precipitation step and a post-synthesis method using the LDH memor...
Monolith-shaped three-way catalysts (TWC) are always at the edge of science and technology as a response to the stringent updates on the emission standards worldwide. In spite of rapid research on TWC materials, the exact compositions adapted by major automotive companies are not fully known. This study focuses on comparing two fresh commercial mon...
The ammonia-SCR catalytic activity of unsupported CeVO4 with an excess of CeO2 was investigated in standard and fast-SCR conditions. Solids were obtained from a hydrothermal synthesis route under a mild condition and then stabilized after aging in a wet atmosphere at 600 and 850 °C. Particular attention was paid to the role of excess CeO2 and the c...
The impact of La-deficiency and substitution by calcium and manganese in LaFeO3 has been investigated in Three-Way-Catalysis. Despite significant structural distortions, predominantly induced by calcium substitution, no significant phase segregation occurs. On the other hand, bulk and surface characterization revealed the stabilization of Mn⁴⁺ and...
Calcium and copper substitutions, in A-site and B-site respectively, of parent stoichiometric LaFeO3 and La-deficient La0.7FeO3 perovskites led to significant improvements in the kinetics of CO and propene oxidation in typical three-way operating conditions. La-deficient La0.7Fe1-yCuyO3 perovskites were found more prone to surface copper oxide segr...
The three-way catalytic performances of Pd-doped CexZr1-xO2 mixed oxides prepared according to a one pot Flame-Spray-Pyrolysis method and through a two steps preparation where Pd was subsequently impregnated on a commercial CexZr1-xO2 prepared by co-precipitation CZ(COP) were compared. Flame-Spray-Pyrolysis led to bare CexZr1-xO2 CZ(FSP) having hig...
Atomically dispersed metals promise the ultimate catalytic efficiency, but their stabilization onto suitable supports remains challenging owing to their aggregation tendency. Focusing on the industrially-relevant Pt/-Al2O3 catalyst, in situ X-ray absorption spectroscopy and environmental scanning transmission electron microscopy allow us to monito...
The development of more thermally stable vanadia-based SCR catalysts for combined end-of-pipe technologies, i.e. selective catalytic reduction catalysts wash-coated on a particulate filter, has been considered in this study. The impact of thermal aging at 850 °C in wet atmosphere has been investigated on bulk W-doped CeVO4 catalysts. Strong detrime...
This study compares the impact of A and B-substitution in parent stoichiometric and La-deficient LaFeO3 perovskites for subsequent development as suitable substrate in three-way catalysis. CO and propene oxidation were investigated to probe their oxidative behavior. It was found that the activity cannot be related neither to the specific surface ar...
A renewed interest of benchmark V2O5/WO3/TiO2 SCR-catalysts is discernible for the depollution of stationary sources jointly with the use of bio-fuels as substitute to fossil fuels. However, the resistance to deactivation has to be reconsidered according to additional alkaline contamination. This study tried to elucidate the impact of potassium on...
The understanding of the reactivity of supported platinum with oxygen is of paramount relevance in heterogeneous catalysis, inter alia. We present here a multi-scale investigation of the interaction of highly dispersed Pt/γ-Al2O3 catalysts with O2, through the combination of TPD (Temperature-Programmed Desorption) experiments, ab initio simulations...
The SCR performances of aged W-doped CeVO4 catalysts were investigated in fast-, NO2- and standard conditions. Bulk CeV1-xWxO4 catalysts were prepared in soft conditions, according to a hydrothermal synthesis route at 180 °C leading to the ad hoc tetragonal structure. The aging procedure consisted in exposing the samples to 10 vol.% H2O diluted in...
A series of La1-yFe1-xCuxO3 catalysts with y = 0, 0.33 and x = 0, 0.17, 0.2 was prepared by a conventional sol-gel method. The catalytic activity in Three-Way Catalysis (TWC) of perovskite-based solids was compared to a commercial reference which contains Pd and Rh. The combination of Lanthanum-deficient synthesis and iron substitution by copper in...
Bulk CeVO4 catalysts prepared by hydrothermal synthesis have been developed for the ammonia-selective catalytic reduction of NOx to nitrogen. The catalytic properties were evaluated in standard- and fast-SCR conditions for stationary and mobile applications. The coexistence of low concentration of Ce⁴⁺ species stabilized as CeO2 with bulk CeVO4 was...
LaFe1−xCuxO3 and La2CuO4 catalysts are investigated for three-way-catalysis application. LaFe1−xCuxO3 solids present interesting catalytic properties mainly with respect to hydrocarbon and CO oxidation and NO reduction in rich conditions with high N2 selectivity. The partial substitution of iron with copper leads to enhanced catalytic activity for...
Catalytic properties of Au-Ag/Al2O3 catalysts, prepared by successive impregnation, have been investigated for the hydrocarbon selective catalytic reduction (HC-SCR) of NOx. The performances of pre-reduced and aged catalysts were evaluated on synthetic reaction mixtures with gas compositions representative of the exhaust of Diesel powered engines....
The catalytic activity of unsupported CeVO4 solid was investigated in ammonia-SCR at various NO/NOx ratio. CeVO4 structure was obtained from a straightforward hydrothermal synthesis route under mild conditions and then stabilized after ageing in wet atmosphere at 600 °C. The influence of pH measured after the hydrothermal treatment could be a cruci...
We report here on an in situ Raman investigation of stoichiometric and La-deficient LaFeO3 solids along model treatments related to three-way catalysis. Whereas the Raman signature of the stoichiometric compound is only slightly modified by the sequence we have applied, the reversible formation of a new phase based on in the La-deficient solid was...
This chapter illustrates different strategies already implemented at laboratory or industrial scale devoted to the catalytic abatement of N2O from nitric acid plants. In this line, the adoption of catalytic end-of-pipe technologies implies a simultaneous conversion of trace amounts of N2O and NO x at rather low temperature before rejection in the a...
Fe-based perovskites prepared with purposely lowered La-content, La1−yFeO3±δ (y = 0, 0.1, 0.2, 0.33), by sol–gel synthesis were investigated for application in 3-way catalysis. It was proven by XPS that surface composition control can be achieved by controlling the bulk composition. The decrease of La-content leads to a lower La excess at the surfa...
Stability and deactivation phenomena are of utmost importance for metal nanocatalysts from both fundamental and industrial points of view. The presence of small amounts of sulfur at ppm and ppb levels in the synthesis gas produced from fossil and renewable sources (e.g., biomass, coal) is a major reason for deactivation of nickel catalysts for carb...
TiO2-anatase-supported rhenium catalysts were prepared by oxidative redispersion of metallic rhenium. The structure and the activity of the as-prepared catalysts were found to be similar to those prepared by the incipient wetness impregnation technique. Interestingly, our results suggest that the active phase of those catalysts retain oxorhenate sp...
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...
This study is dedicated to the development of thermally stable LaCo1−xFexO3 perovskite based catalysts for the decomposition of N2O at medium and high temperature, in representative compositions of exhaust gas from ammonia burner in nitric acid plants. In these specific conditions, N2O coexists with a large amount of NOx. Up to now, lab-scale inves...
This study is dedicated to a combined spectroscopic approach
for investigating bulk versus surface reconstructions that originated during
high-temperature catalytic applications on EuCo1−xFexO3 and to their related
impact on the catalytic properties. By way of illustration, the decomposition of
nitrous oxide (N2O) has been selected as a case study...
This study is devoted to an operando study of Pt–Rh/Al2O3–BaO lean-NOx trap catalyst during the regeneration with H2/CO reaction mixture. Particular attention was paid to the influence of CO coexisting with H2 during the regeneration that can simulate the regeneration step by using reformate composed of CO and H2. In rich H2 mixture ammonia predomi...
CFD modelling and tracer experiments were performed in order to improve the design of sample holder used for transmission IR experiments in flow conditions.The complexity of gas velocity field evidenced for the usual circular geometry is avoided with an alternative geometry. A new geometry involving a square pellet, multiple inlets and outlets and...
The regeneration of Lean NOx Trap catalyst (Pt–Rh/BaO–Al2O3) using H2 + CO was followed with operando IR spectroscopy methodology. The role of H2 was investigated from 2 to 20 vol.% H2. The increase of H2 partial pressure allowed a subsequent decrease of the regeneration duration. The quantity of NH3 formed during the regeneration was related to H2...
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...
Supported gold catalysts on γ-Al2O3 have been investigated in the catalytic reduction of NOx
in simulated Diesel exhaust gas conditions. Different parameters have been examined essentially the mode of gold incorporation via classical deposition–precipitation and anionic exchange methods and the nature of the pre-activation thermal treatment. The re...
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...
An operando spectroscopic study of the NO/H2 reaction has been achieved to relate spectral features to kinetic data in order to identify key intermediates involved in the production of N2, N2O and NH3 as the main reaction products. Transient experiments show that different nitrosyl species, essentially neutral, positively and negatively NO adsorbed...
1 Introduction NO x abatement from Diesel engine exhaust gas remains as one of the major challenges in environmental catalysis. Among the different strategies, the use of free noble metal catalyst is cost efficiency and the selective catalytic reduction of NO x from unburned hydrocarbons is one of the most feasible technologies. Supported silver-ba...
The catalysts were characterized by BET, UV-vis, XPS, LEIS, TOF-SIMS and elemental analysis. Temperature-programmed reaction experiments were performed in a fixed bed flow reactor with a gas mixture composed of 0.03%NO, 0.03%CO, 0.03%C 3 H 6 , 0.01%C 10 H 22 , 0.2%H 2 , 10%O 2 , 10%CO 2 , 5%H 2 O and He (18L.h-1). Thermal ageing was performed at 50...
Table 2: XPS and elemental results of calcined and tested samples XPS measurements • Presence of metallic gold on fresh catalysts • Higher concentration of gold on AE aged samples on the contrary to DP sample • Negative shift (~0.5 eV) observed on aged samples and on AuDAE calcined at 500 o C=> related to the extent of the metal/support interaction...
Catalytic activity for the N2O decomposition into N2 was investigated on perovskite-based materials in the presence of 5 vol% NO, 6 vol% O2 and 15 vol% H2O. This feed is typical of industrial conditions for nitric acid plants operating at high temperature (850–900 °C). The catalytic properties were found to be sensitive to the surface composition a...
NO x abatement from diesel engine exhaust gas remains as one of the major challenges in environmental catalysis. Among different
Catalytic properties of supported gold catalysts on γ-Al2O3 prepared by a conventional deposition–precipitation method were compared with those obtained by anionic‐exchange for the reduction of NOx by hydrocarbon under lean conditions that simulate Diesel engine exhaust gas. Interestingly, a catalytic activity enhancement is observed after thermal...
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...
Interaction of a Co-BEA catalyst with individual components (NO, C3H6, CO, O-2) and mixtures simulating the real feed of the selective catalytic reduction (SCR) of nitric oxide in static and pulse experiments at variable temperatures was investigated by means of IR, EPR, and operando DRIFT spectroscopy coupled with QMS/GC analysis of the products....
This present study deals with the development of thermally stable catalysts for the decomposition of nitrous oxide. There is actually a growing interest to minimise the emissions of nitrous oxide (N2O) as side-product from nitric acid plants due to a global warming potential of approximately 300 times higher than that of CO2. Different strategies h...
The Linear Solvation Energy Relationship approach has been developed in order to correlate adsorptive properties of LaCoO3 perovskite based materials with their catalytic performances. Particular attention was paid to the influence of palladium incorporation according to two different routes: (i) a sol–gel method leading to oxidic palladium species...
A comparative investigation of the catalytic performance in the simultaneous conversion of NOx and N2O has been achieved on supported nanosized Pt particles interacting with conventional alumina and perovskite based materials. Particular attention has been paid to successive thermal treatments under reductive and oxidative atmospheres which induce...
This study reports surface characterizations of Pd/LaFeO3 catalysts after aging in diesel engine simulated conditions. Thermal aging and support-induced effects on the nature of Pd species were investigated. LaFeO3 was prepared via a sol–gel method to promote relatively high specific surface area (19 m2 g−1). Subsequent impregnation from solutions...
This study investigates thermal aging induced effects on the surface properties of model and commercial automotive catalysts for Natural Gas Vehicles, by means of X-ray photoelectron spectroscopy and infrared spectroscopy of chemisorbed CO as a probe molecule for noble metals. Post-combustion catalysts for this application are essentially composed...
Gold supported on alumina was prepared by urea deposition-precipitation method and compared to silver supported on alumina for the selective catalytic reduction of NO by hydrocarbons under lean conditions. The catalyst showed activity in the reduction of NO and 100% selectivity towards N2 in the temperature range 300–350°C. At higher temperature th...
The simultaneous reduction of NO and N2O has been investigated on Pt-based catalysts supported on γ-Al2O3 and perovskite materials (LaFeO3). Particular attention has been paid to the catalyst resistance to thermal sintering processes occurring under reaction conditions at elevated temperature in the presence of oxygen and water. Bulk and surface mo...
Grafting of [Ln(BH(4))(3)(THF)(3)] (Ln = La, Nd) onto silica affords materials containing well-identified bis(borohydride) surface species. The neodymium-decorated silica converts the beta-butyrolactone monomer into highly isotactic poly(beta-hydroxybutyrate). Under similar conditions, the molecular precursor gives rise to an atactic polymer.
The influence of the support synthesis for the preparation of supported Pd/LaFeO3 perovskite based catalysts and the nature of the palladium precursor on the catalytic performances in the selective reduction
of NO to N2 by hydrocarbons have been investigated. According to the preparation method, subsequent surface and bulk characterisation
revealed...
This study reports the potential interest of LaCoO3 in the catalytic decomposition of N2O from nitric acid plants. Typically, the exhaust gas contains NO, water and O2 which usually induce strong inhibiting effects depending on the surface properties of the solids particularly the surface mobility of oxygen from LaCoO3. Different preparation method...
The methanol conversion to methylal over a series of TiO2-anatase supported oxorhenate catalysts was investigated using operando UV-visible and Raman spectroscopy and compared to the catalytic activities afforded by a classical test. In dehydrated catalysts, two distinct structures were clearly identified and correlated to different catalytic behav...
The catalytic reduction of NO by hydrogen has been studied over palladium-based catalysts supported on LaCoO3. Particular attention has been paid to the observation of chemisorbed N-containing species from operando infrared spectroscopic experiments during the NO/H2 reaction in the presence and in the absence of excess oxygen. X-ray photoelectron s...
This study is devoted to the catalytic decomposition of N2O over noble metal-based catalysts under lean conditions in the presence of O2, NO and water. A particular attention has been paid toward the influence of the support and the thermal ageing-induced effects on the catalytic properties of palladium species. In those operating conditions, the d...
26-30 mai 2008 Présentation : C. Dujardin
26-30 mai 2008 Présentation : C. Dujardin
Présentation : J.P. Dacquin ORAL 26-28/05/08
We report for the first time the use of an amorphous oxide catalyst for the selective oxidation of methanol in the gas phase, leading at 553 K to the production of dimethoxymethane with a selectivity as high as 90% at high methanol conversion (68%).
This study deals with the catalytic decomposition of N2O over noble metal based catalysts. The deposition of palladium on reducible supports such as LaCoO3 leads to higher activity from temperature-programmed experiments in comparison with conventional supports such as alumina. Such a different catalytic behaviour cannot be completely explained by...
Presently, a growing interest is focused on unregulated emissions of nitrous oxide (N2O) from stationary and mobile sources in order to anticipate future restrictive legislations, since N2O exhibits a significant higher global warming power than that of CO2.The adoption of end-of-pipe technologies is appropriate. However, the simultaneous conversio...
In situ X-ray diffraction (XRD) analysis was used to investigate structural evolutions of LaCoO3 catalysts and then further modified by palladium (Pd) addition, under various controlled atmospheres, particularly during the reduction of NO by hydrogen in lean conditions. Complementary, XPS measurements provided information about changes in the chemi...
A series of sulfided (Co)Mo/Al catalysts was examined using IR spectroscopy of CO adsorption (Tads ~ 100 K), thiophene hydrodesulfurization and 2,6-dimethylaniline hydrodenitrogenation. Spectroscopic analysis after treatments at H2S partial pressures and temperatures close to the working conditions allows one to establish relationship between the n...
25 et 26 janvier 2007 Présentation : P. Granger
In situ X-ray diffraction (XRD) and quasi in situ X-ray photoelectron spectroscopy (XPS) measurements were complementary used to investigate structural and surface modifications of a palladium-supported on LaCoO3 perovskite catalyst under various controlled atmospheres, particularly during the reduction of NO by hydrogen under lean conditions, in t...
20-23 september 2006 Présentation : C. Dujardin
Colloidal suspensions of rhodium nanoparticles have been easily prepared in aqueous solution by chemical reduction of the precursor RhCl3·3H2O in the presence of the surfactant N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride (HEA16Cl) and further used to immobilize rhodium nanoparticles on silica by simple impregnation. The obtained silica...
23-28 July 2006 Présentation : P. Granger
13 et 14 avril 2006 Présentation : J.P. Dacquin
4-6 avril 2006 Présentation : I. Twagirashema
13 et 14 avril 2006 Présentation : I. Twagirashema
The oxidation of methanol has been studied on Mo/Al2O3 catalyst in absence and presence of oxygen. Quasi-simultaneous IR and Raman spectroscopies were used to follow the evolution of the active phase and adsorbed species on the catalyst under reaction conditions.An increase of reduced Mo species on the active phase is observed by Raman spectroscopy...
Experimental IR spectra of carbon monoxide adsorbed on a series of Mo/Al2O3, CoMo/Al2O3, and NiMo/Al2O3 sulfided catalysts have been compared to ab initio DFT calculations of CO adsorption on CoMo and NiMo model surfaces. This approach allows the main IR features of CO adsorbed on the sulfide phase to be assigned with an uncertainty of 15 cm(-1). O...
Cited By (since 1996): 20, Export Date: 31 July 2012, Source: Scopus
29 mai au 1er juin 2006 Présentation : C. Dujardin
