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[Display omitted] • Competition between chemisorbed O species and surface lattice oxygen species as active oxygen species in methane activation. • K-doping suppresses the reactivity of surface lattice O species in C–H bond scission. • Competition between single site and dual sites reaction mechanisms strongly perturbated by thermal aging. • Detrimental effect of K-doping of methane combustion due to the growth of K 1.4 Mn 3 O 6. The kinetics of the CH 4 /O 2 reaction, occurring on post-combustion catalysts to treat the exhaust gases of natural gas-powered engines, has been investigated in lean conditions on model Pd catalysts supported on K-doped LaMnO 3. Experimental and predicted reaction rates have been compared according to a single site on Pd active sites and dual site reaction mechanism on active sites located at the Pd-perovskite interface. Comparisons with a benchmark Pd/LaMnO 3 emphasized significant changes induced by thermal aging at 750 °C in wet atmosphere (10 vol% H 2 O in 5 vol% O 2). Indeed, the contribution of the single site mechanism grows on aged Pd/LaMnO 3 emphasizing a deterioration of the Pd-LaMnO 3 interface. The opposite trend is observed on Pd/La 1− x K x MnO 3 with kinetics obeying to a single site mechanism on pre-reduced catalyst and then shifting to a quasi-exclusive dual site mechanism after aging. Such kinetic features have been discussed with respect to bulk and surface physicochemical characterization pointing out the key role of potassium in the stability of the Pd-support interface. [ABSTRACT FROM AUTHOR]

This paper reports a short review on the impact of poisoning effects and thermal aging on the reactivity of surface vanadate species on benchmark V2O5−WO3/TiO2 Selective‐Catalytic‐Reduction catalysts. A renewed interest of this SCR technology is related to its diversification notably as after‐treatment systems to treat the exhaust from Diesel engines with higher running temperature especially when SCR catalysts are coated on Diesel Particulates Filters. Particular attention is also paid to poisoning effects in conjunction with the progressive replacement of fossil fuels by bio‐fuels containing alkaline contaminants which drastically deactivate the catalyst through neutralization of strong acid sites. Most of the investigations show that better insight into the mechanisms of poisoning and aging processes is needed especially to understand the relative sensibility of various vanadate species. This could provide original guidelines to catalyst preparation and or the developments of more stable bulk systems as exemplified. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of methyl orange has been studied under visible light. The combination of polyaniline and montmorillonite doped by cobalt and nickel cations enhanced the photocatalytic activity compared to pristine polyaniline. Kinetic measurements have been tentatively explained on the basis of their composition, electronic structures, structural and textural properties. Separate experiments performed on doped montmorillonites show weak performances, reflecting their insulating behaviour, altered by diffusion limitations. A pseudo-first order agrees with a weak methyl orange adsorption. More open porosity of composite materials led to improved efficiency. Their superiority compared to doped montmorillonites has been preferentially related to surface heterogeneity, stronger methyl orange adsorption and lower band gap energy. [ABSTRACT FROM AUTHOR]

A combined temporal analysis of products (TAP) and steady-state kinetic study was achieved to characterize the surface reactivity of fresh and aged bimetallic Pd-Rh/AlO Natural-Gas Vehicle catalysts. Single NO pulse TAP experiments were performed on a stabilized surface after exposure to successive NO pulses until to get a steady-state NO conversion. Outlet flow curves recorded during such experiments show fast reaction steps taking place on noble metal particles and a slow process during NO desorption ascribed to the involvement of spill-over effect of chemisorbed NO molecules from the metal to the support. This slow process attenuates on the aged sample likely due to an alteration of the metal/support interface induced by particle sintering at high temperature. Thermal aging also alters the surface composition of bimetallic Pd-Rh particles which leads to changes in the products distribution from NO dissociation. A similar selectivity behavior is observed from steady-state kinetic measurements during the NO/H reaction. Interestingly, a weak partial pressure dependency of the selectivity reflects a surface Rh enrichment of Pd-Rh particles during aging. [ABSTRACT FROM AUTHOR]

Rhodium and platinum-rhodium based catalysts supported on La 2 O 3 and Al 2 O 3 doped with La 2 O 3 were investigated in the dry reforming of methane. The textural and structural properties were studied on calcined, reduced and used catalysts from nitrogen physisorption, X-ray diffraction, XPS, SEM, H 2 - and O 2 -temperature-programmed experiments. Rh is intrinsically more active than Pt independently of the support composition. Different types of interactions occur when Rh is incorporated in Pt on La 2 O 3 and La-modified α-Al 2 O 3 supports with the observations of synergistic effects on the activity of Pt-Rh/Al 2 O 3 -La 2 O 3 for methane conversion. Correlations between catalytic properties with structural and surface properties have been tentatively established and are discussed. A detrimental effect of alloyed Pt-Rh particles on La 2 O 3 and a beneficial effect on the catalytic activity of Pt-Rh/Al 2 O 3 -La 2 O 3 due to the formation of possible composite microstructures combining noble metals and the elements of the support is reported. [ABSTRACT FROM AUTHOR]

Kinetics has been proven to be a powerful method to probe catalytic surfaces under reaction conditions in order to elucidate, at molecular level, complex chemical processes. Numerous techniques and methodologies have been already implemented (surface science approaches, TAP, SSITKA...) running in very different pressure ranges (pressure gap) which led to controversial statements regarding suggested mechanism schemes, especially for DeNOx reactions. Two typical reactions taking place over NGV catalysts have been selected to illustrate which information can be tackled from kinetic measurements. Both reactions occur in different temperature ranges and are sensitive to the structure of the catalyst, to the surface composition of bimetallic particles, with possible surface enrichments, and to the participation of the support. Hence, it will be tentatively demonstrated that kinetic combined with spectroscopic or theoretical methods can be appropriate to establish relevant correlations between kinetic parameters and the topology of the catalyst surface. [ABSTRACT FROM AUTHOR]

Abstract: The dry reforming of CH4 by CO2 has been studied, between 300 and 900°C, over monometallic platinum and rhodium based catalysts supported on α-Al2O3 doped with La2O3 and BaO. Those catalysts were prepared by conventional wet impregnation and characterized by various physicochemical techniques (nitrogen adsorption, X-ray diffraction, XPS analysis and H2-temperature-programmed experiments). It was found that Pt and Rh incorporation leads to different types of interactions with La and Ba-modified α-Al2O3. As observed, Pt would preferentially interact with Ba inducing an inhibiting effect on the rate of the CH4/CO2 reaction reflected by a significant increase in the apparent activation energy. On the other hand, the preferential interaction of Rh with lanthanum oxide after Ba incorporation leads to the preservation of the catalyst activity. Such changes in catalytic properties have been discussed in the light of surface characterization and previous mechanistic information related to the occurrence of a bi-functional mechanism involving the metal/support interface. [Copyright &y& Elsevier]

The article presents a review of the study which describes the three-way catalysis of nitric oxide emissions and abatement systems in lean-burn engines. It explores the strategies in selective reduction of emissions from heavy duty vehicles using urea in the development of iron-based catalysis on acidic materials. The authors believe that a complex system is needed to reduce the bad effects of engine efficiency and fuel consumption through material catalysis or by adding reformates.

The oxidation of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) has been investigated on MO x @Nb-zeolite catalytic systems (where MO x = CoO x , MnO x or FeO x and zeolite - USY and Beta) with hierarchical texture and acid-base properties. These catalysts were exhaustively characterized by several techniques such as XRD, adsorption-desorption of liquid nitrogen at 77 K, CO 2 - and NH 3 -TPD, DRIFT, XPS, and SS NMR. The new hierarchically catalysts produced HMFCA with a selectivity of 97.0% for a X HMF = 95.0% (Mn@Nb-Y30). A synergetic effect between MO x and Nb species in the activation of t -BuOOH and oxidation of HMF has been identified. The absence of FDCA in the reaction products using MOx@Nb-zeolite catalysts can be due to the preponderant presence of the acidic sites (associated to both framework and extra framework AlO x) which prevent a further oxidation of HMFCA to FDCA. [Display omitted] • Multifunctional hierarchically zeolites with non-precious metals. • Selective oxidation of HMF to HMFCA intermediate • The new combination of oxides avoids the use of homogeneous bases • Selective oxidation control through the AlO x framework [ABSTRACT FROM AUTHOR]

[Display omitted] • Simple sonochemistry route to prepare single Pt atoms anchored on carbonaceous materials. • Unexpected NO decomposition on single Pt atoms related to weak O-inhibiting effect. • New mechanistic insights in NO decomposition: from nanoparticles to single atoms • High thermal resistance of single Pt atoms up to 650 °C in wet conditions Activated carbon containing highly dispersed platinum (Pt/C with ca. 1 wt.%) catalyst was synthesized according to the simple sonochemistry route followed by a drying step in air at 130 °C. STEM-HAADF micrographs indicate the presence of Pt single atoms (SAs) homogeneously dispersed on the activated carbon. The catalytic decomposition of NO has been investigated on samples pre-reduced at 250 °C and 500 °C. The Pt SAs remain stable and exhibit a surprisingly high activity which does not reflect the usually observed structure-sensitivity of NO dissociation. In addition, remarkable catalyst stability is observed after reaction at 650 °C in the presence of water. On the other hand, pre-reduction at 500 °C induces a strong deactivation related to a coalescence process with the subsequent generation of large Pt clusters, despite some small metal nanoparticles are still present in the sample. Accordingly, the structure-sensitivity of this reaction is restored. All these observations have been rationalized through the examinations of various reaction mechanisms. [ABSTRACT FROM AUTHOR]

Highlights from the article: Kinetics and reactor modeling for heterogeneous catalytic reactions are prominent tools for investigating, and understanding, the catalyst functionalities at nanoscale, and related rates of complex reaction networks. The objective of this special issue is to provide diverse contributions that can illustrate recent advances and new methodologies for elucidating the kinetics of heterogeneous reactions and the necessary multiscale approaches for optimizing the reactor design. Finally, two contributions report lab-scale experiments on structured catalysts, e.g., dense filamentous graphite [[7]], and illustrating the best practice at lab-scale through the comparison of catalysts in powder and tableted form to examine the impact of internal diffusion limitation on the determination of kinetic parameters.

The effect of La‐deficiency and Ce/Sr‐substitution in the benchmark LaCo0.8Fe0.2O3 has been investigated for the decomposition of N2O between 500 and 900 °C. Real inlet gas composition and space velocity reveal that La‐deficiency and Ce/Sr‐substitution can improve the thermal stability of catalyst, while La1‐xSrxCo0.8Fe0.2O3 with x≥0.1 was highlighted as a promising formula due to the strongest resistance to deactivation and suppressed undesired NOx decomposition at high space velocity. This phenomenon is mainly ascribed to the incorporation of Sr2+ into the perovskite lattice during the reaction consequently stabilizing the Co3+ species and creating the oxygen vacancies in La1‐xSrxCoO3‐δ. On the contrary, the loss of activity on Ce‐substituted LaCo0.8Fe0.2O3 has been preferentially related to the cobalt exsolution to extra framework of perovskite making the catalytic cycle with Co3+ unfavorable. All these bulk and surface changes are accompanied with opposite evolution of apparent activation energy and pre‐exponential factor which can be discussed based on a redox mechanism. [ABSTRACT FROM AUTHOR]

• Single versus dual-site reaction mechanism for methane combustion on Pd/La x MnO 3 governed by La-stoichiometry. • Mn/La ratio and Pd n+ species (with n > 2) as relevant descriptors of the efficacy of the Pd-La x MnO 3 interface. • Deleterious effect of water depending on thermodynamic and kinetic parameters. • Detrimental La-enrichment either on Pd accessibility and on the formation of reactive surface lattice oxygen species. The kinetics of the catalytic CH 4 /O 2 reaction has been studied on 1 wt% Pd/La x MnO 3 with x = 0.7, 1.0 and 1.3. Steady-state kinetic measurements have been performed in lean conditions at 400 °C on pre-reduced and on aged catalysts after exposure to wet atmosphere at 750 °C. A single site reaction mechanism occurs preferentially on Pd/La 1.3 MnO 3 exhibiting a La-rich surface. In contrast a dual-site reaction mechanism, combining Pd and surface reactive oxygen species from the support, is preferentially involved on Pd-La 0.7 MnO 3 characterized by a Mn-rich surface. Pd/LaMnO 3 exhibits a mixed regime but subsequent deterioration of the Pd-La x MnO 3 interface during thermal aging leads to increasing contribution of the single site reaction mechanism. High surface Pd/Mn ratio and high concentration of Pd n+ with n > 2 can be considered as good descriptors to probe the efficacy of Pd/La x MnO 3 catalysts. Remarkably, the high thermal stability of the Pd-La 0.7 MnO 3 interface, preserving the Pd dispersion on Pd/La 0.7 MnO 3 , leads to lower sensitivity to deactivation. [ABSTRACT FROM AUTHOR]

The dry reforming of methane was investigated using a novel catalyst based on natural illite clay to which nickel and magnesium has been added into moldable paste easily extrudated into honeycomb monolith. This approach can represent a significant breakthrough offering an alternative to conventional costly wash-coated ceramic substrates usually difficult to optimize, and a gain in efficiency thanks to the minimization of transfer limitations. The best catalytic performance were obtained with illite clay containing 8 wt.%Ni and 3 wt.%Mg, yielding to excellent conversions of CH 4 and CO 2 at 800 °C of respectively 81% and 76%. The catalytic enhancement observed on magnesium-doped systems was attributed to the stabilization of smaller Ni particles associated with the formation of NiO-MgO solid solution which slows down particle sintering. The obtained results suggest different types of nickel-support interactions in addition to improved basic properties inducing synergy effects on the rate of methane and CO 2 conversion and higher resistance to deactivation phenomena. [ABSTRACT FROM AUTHOR]

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 monolithic catalyst: (i) a high content of PGMs (Pd and Rh) loading with a variable concentration distribution along the catalyst, called zone-coating, was investigated in order to take advantages of an in situ pre-heating due to exothermic oxidation processes. And (ii) the use of external device for heating the monolith with the aim to shorten the laps of time to reach the required temperature for their conversion. Both approaches were compared below 300 °C in terms of NO, CO and hydrocarbons conversions as well as N2O formation with respect to homogeneously wash-coated catalyst. For evaluation, complex exhaust gas compositions were considered at different steady-state air-to-fuel λ ratios and high frequency transient lean/rich regime to mimic real operation in gasoline engine exhaust. Results show that a pre-heating of the catalyst at 300 °C is necessary to avoid completely N2O formation from NO reduction with CO. Remarkably higher NO and CH4 conversions were observed during transient regime rather than steady-state lean, rich or stoichiometric conditions at 200 and 300 °C. [ABSTRACT FROM AUTHOR]

Methane oxidation has been studied on Rh/CexZr1−xO2. Catalytic performances were found highly sensitive to the preparation method of CexZr1−xO2 support. Coprecipitation method leads to the highest conversion and the lowest activation barrier suggesting improved metal-support interaction. In contrast, weak resistance to thermal aging is observed. Finally aged coprecipitated Rh/CexZr1−xO2 mimics the kinetic behavior of catalysts prepared by crystal templating method. Kinetic measurements performed on this latter catalyst show that a single site reaction mechanism is more appropriate compared to dual site mechanism which agrees with the assumption that deactivation of coprecipitated samples would be related to the suppression of the metal-support interface. [ABSTRACT FROM AUTHOR]

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 found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study. [ABSTRACT FROM AUTHOR]

A series of Ni–Ce catalysts supported on illite clay containing different cerium loading were tested with respect to autothermal reforming of methane at 800 °C using a GHSV = 60,000 mL g −1 h −1 . The addition of oxygen in the gaseous reactant feed, under the used experimental condition was found to play a key role since the carbon balance is significantly higher as compared to CH 4 /CO 2 mixture. The addition of cerium was found to enhance the specific surface area as result of meso-porosity development. Furthermore, the nickel particles become smaller in the presence of Ce, decreasing the Ni° average size from 34.2 for 10Ni to 16.3 nm for 10Ni15Ce. The best catalytic activity and stability were obtained on the catalyst containing 15 wt.% of cerium, apparently attributed to its redox properties and further improvement on the nickel dispersion. It should be pointed out that the observed catalytic performance was high even after 24 h under reaction stream. [ABSTRACT FROM AUTHOR]

Bimetallic Ag–Au/Al 2 O 3 catalyst was synthesised by successive impregnation of 1% Au and 1% Ag on in-house prepared high surface area alumina (450 m 2 /g). The corresponding monometallic catalysts were also prepared by loading 1% Ag or 1% Au on the same high surface area alumina for comparison. The catalysts were characterised by various physico-chemical techniques and tested for SCR activity under lean burn engine exhaust conditions. Ag–Au/Al 2 O 3 catalyst prepared by successive impregnation method showed considerably higher NO reduction (100%) to N 2 compared to 1% Au/Al 2 O 3 (70%) whereas the activity was comparable with that of 1% Ag/Al 2 O 3 (96%). The effect of various pretreatments on SCR activity of Ag–Au/Al 2 O 3 was studied and pretreatment at 250 °C in flow of hydrogen was found to give the best results with 100% NO conversion to N 2 at 353 °C. Further ageing of the catalyst under reaction feed at 500 °C resulted in considerable increase in low temperature activity of bimetallic catalyst with ∼40% NO conversion at 222 °C. Even though the SCR activity of pretreated Ag–Au/Al 2 O 3 and Ag/Al 2 O 3 were comparable, after ageing the Ag–Au/Al 2 O 3 showed significantly higher NO conversion (95%) compared to Ag/Al 2 O 3 (83%) and Au/Al 2 O 3 (70%). The formation of H 2 and CO due to steam reforming of higher hydrocarbon (decane) was evidenced at the temperature of highest deNO x activity. Detailed investigation of the textural properties of the pretreated and aged catalysts showed presence of well dispersed metallic Au and Ag n δ+ clusters after pretreatment in hydrogen at 250 °C. [ABSTRACT FROM AUTHOR]

LaCo 1− y O 3 ( y = 0 and 0.2) and LaCo 1− x Fe x O 3 ( x = 0.6 and 1) perovskites were used as catalysts for the total oxidation of methane in the temperature range 300–800 °C and characterized by in situ electrical conductivity measurements. Their electrical conductivity was studied as a function of temperature and oxygen partial pressure and temporal responses during sequential exposures to air, methane–air mixture (reaction mixture) and pure methane in conditions similar to those of catalysis were analyzed. The intrinsic activity of the perovskites at 550 °C followed the order: LaFeO 3 < LaCo 0.8 O 3 < LaCo 0.4 Fe 0.6 O 3 < LaCoO 3 . LaCo 1− y O 3 perovskites were in a metallic conductivity state in the reaction temperature range while LaCo 1− x Fe x O 3 perovskites appeared to be p-type semiconductors both under air and under reaction mixture with positive holes as the main charge carriers. A transition from semiconducting state to the metallic state was observed for LaCo 0.4 Fe 0.6 O 3 in the reaction temperature range. Their electrical conductivity at 550 °C increased following the order: LaFeO 3 < LaCo 0.8 O 3 < LaCo 0.4 Fe 0.6 O 3 < LaCoO 3 . Correlations between their conducting behavior and redox properties, on one hand, and their catalytic behavior, on the other hand, have been evidenced. It was demonstrated that the reaction mechanism involves surface lattice O − species and can be assimilated to a Mars and van Krevelen mechanism for LaFeO 3 , while it involves only adsorbed oxygen species for LaCo 1− y O 3 , being assimilated to a suprafacial mechanism. Both suprafacial and redox mechanisms take place on LaCo 0.4 Fe 0.6 O 3 perovskite. [ABSTRACT FROM AUTHOR]

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 (λ=1). Periodic rich/lean switching emerges as a promising strategy to address this challenge. In this work, we investigate the influence of the switching process, using a fixed lambda air-to-fuel ratio amplitude of λ = 1±0.02 (0.5 Hz), on pollutant conversion from 100 to 400 °C, under a complex matrix including nitrogen monoxide (NO), carbon monoxide (CO), hydrogen (H2), and hydrocarbons (C1-C5), simulating the typical car exhaust gas. Moreover, two catalysts were tested: one homogeneously coated with Pd, and another zone-coated with Pd, both containing the same total amount of Pd, in order to identify the effect of the catalyst zone-coating and rationalize the use of increasingly scarce platinum group metals. Simple binary pollutant oxidation reactions were also performed to determine the reactivity of individual pollutant gases. Interestingly, NO, CH4 and C5H12 displayed highest conversions during the switching regime compared to steady-state periods, attributed to the beneficial balance between active site poisoning/regeneration during the rich/lean regimes respectively. The zone-coated catalyst showed an overall higher activity under the full gas mixture that could be explained by a slightly higher Pd content, more effective Pd-support interactions, exothermic effect or the better OSC properties. [ABSTRACT FROM AUTHOR]

LNE-CETIAT liquid flow laboratory is the French Designated Institute for liquid water flow rate from 1 g h−1 to 50 t h−1. Historically, its primary standards are based on the flying start and stop gravimetric method. The best relative expanded uncertainty for liquid mass flow rate is 0.05% (k = 2). In the scope of the Joint Research Project Metrowamet and its mission to maintain and develop the French standards for liquid flow, LNE-CETIAT has developed and validated a dynamic primary standard for unsteady liquid flow calibration. This paper will first present the developped system, which is composed of a dynamic flow generator and a dedicated measuring system together with its own software for data acquisition and processing. The validation, realized by intra and inter-laboratory comparisons for static and dynamic flows, is presented in the third chapter. Finally, the validation of the measurement and calibration capabilities, based on internal tests and inter-laboratory comparisons are presented. • Flow and water meters are calibrated under steady and controlled flow conditions. • Flow and water meters are often used in unsteady, uncontrolled flow conditions. • A dynamic calibration method has been developed for dynamic liquid flow calibrations. • Experimental validation shows an associated relative uncertainty of 0.2% (k = 2) under dynamic flow conditions. • The method can be adapted to higher and lower flow rates and to other physical quantities. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports a kinetic investigation of the global reduction of NO by H2 which has been considered as a probe reaction for characterising the adsorption properties of supported palladium based catalysts. A particular attention has been paid towards the influence of the support on the catalytic properties of Pd, particularly towards the production of undesirable by-products such as nitrous oxide (N2O) and ammonia (NH3). It has been found that the kinetics of the overall NO+H2 reaction on Pd/Al2O3 can be correctly depicted according to a Langmuir–Hinshelwood mechanism involving the dissociation of nitrosyl species assisted by chemisorbed hydrogen atoms. On the other hand, Pd/LaCoO3 exhibits a different kinetic behaviour towards the adsorption of hydrogen depending on the pre-activation thermal treatment. In that case, different mechanisms may occur. [Copyright &y& Elsevier]

[Display omitted] • Limited amount of Pd and dopants is required to optimize oxidative properties. • NO reduction is favored with higher Rh concentration. • Ce-Zr-Al distributions play a major role in OSC and catalytic activity. • Ba sulfates has even a limited or negative impact on performances. • Cost/effectiveness should be carefully considered in catalytic formulation strategy. 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 monolithic catalysts for gasoline engines, namely, monolith-A and monolith-B, to highlight the significance of their manufacturing strategies by its characterization and catalytic evaluation under realistic lean/rich/stoichiometric regimes. Firstly, monolith-A demonstrates a zoning on its front and back side with high Pd and Rh loading to enhance CO/HC oxidation and NO x reduction, respectively, having higher amounts of trace dopants like La, Y, Pr and S. Whereas, monolith-B has a homogeneous composition with much lower noble metal/trace elements content without any Pr and S. Secondly, the double-layer washcoating is employed by following different routes with distinct compositions of alumina and ceria-zirconia. Monolith-B showed better low temperature CO oxidation performance while monolith-A performed better for NOx reduction owing to higher Rh loading. Overall, the zoning strategy of monolith-A raises question on its cost effectiveness in regards to its performance while poor reduction capabilities is exhibited by monolith-B. This study highlights that the latest TWC strategies have a scope of further development particularly with respect to the catalytic performance/expense ratio. [ABSTRACT FROM AUTHOR]

[Display omitted] • Limited amount of Pd and dopants is required to optimize oxidative properties. • NO reduction is favored with higher Rh concentration. • Ce-Zr-Al distributions play a major role in OSC and catalytic activity. • Ba sulfates has even a limited or negative impact on performances. • Cost/effectiveness should be carefully considered in catalytic formulation strategy. 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 monolithic catalysts for gasoline engines, namely, monolith-A and monolith-B, to highlight the significance of their manufacturing strategies by its characterization and catalytic evaluation under realistic lean/rich/stoichiometric regimes. Firstly, monolith-A demonstrates a zoning on its front and back side with high Pd and Rh loading to enhance CO/HC oxidation and NO x reduction, respectively, having higher amounts of trace dopants like La, Y, Pr and S. Whereas, monolith-B has a homogeneous composition with much lower noble metal/trace elements content without any Pr and S. Secondly, the double-layer washcoating is employed by following different routes with distinct compositions of alumina and ceria-zirconia. Monolith-B showed better low temperature CO oxidation performance while monolith-A performed better for NOx reduction owing to higher Rh loading. Overall, the zoning strategy of monolith-A raises question on its cost effectiveness in regards to its performance while poor reduction capabilities is exhibited by monolith-B. This study highlights that the latest TWC strategies have a scope of further development particularly with respect to the catalytic performance/expense ratio. [ABSTRACT FROM AUTHOR]

Cyanosilylation, aldol coupling and asymmetric Henry reactions were carried out with L‐ and D‐valmet ligands in different configurations: i) coordinated to sodium ions, as organocatalysts, with week base properties, ii) complexes with copper(II), as homogeneous catalysts, and iii) immobilized copper(II) complexes onto graphene oxide (GO) as heterogeneous catalysts. For the reaction of benzaldehyde and nitromethane in water these afforded an asymmetric Henry reaction, with a spectacular increase of the conversion and ee (92.5 and 95.8 %, respectively) after the deposition on GO. Ligand complexed copper was also effective for cyanosilylation and Aldol coupling reaction. [ABSTRACT FROM AUTHOR]

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 consequences of hydrothermal aging on physical–chemical properties and catalytic activity. The XRD patterns put into evidence the formation of the zircon-type structure of CeVO4 in agreement with a segregation of cubic face-centered structure of ceria (CeO2). Along with adding an excess of CeO2, high specific surface area (102 m2/g) for the 11wt% CeO2/CeVO4 solid was obtained. The presence of CeO2 nanoparticles in addition to CeVO4 nanoparticles have limited the decrease in the specific surface area after aging at 600 and 850 °C. The catalyst with 11wt% CeO2/CeVO4 exhibited the best catalytic performances in standard and fast SCR conditions after thermal aging at 600 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pd-LaMnO 3 interface in CH 4 combustion on NGV catalyst modeled by a dual site reaction mechanism. • Nature of reactive oxygen species in CH 4 /O 2 reaction depending on the extent of Pd-LaMnO 3. • Role of thermal aging in the build up or reversely the deterioration of the Pd-LaMnO 3 interface. • Greater sensitivity of Pd to thermal sintering on impregnated Pd/LaMnO 3 catalyst compared to sol gel LaMn 1- x Pd x O 3. The kinetics of the CH 4 /O 2 reaction was studied in lean conditions on Natural-Gas-Vehicle Pd-doped LaMnO 3 catalysts. The impact of the method for Pd incorporation, sol–gel vs. impregnation, has been examined. The calcination temperature to obtain the perovskite structure turned out to be a key to determine the strength of the interaction between Pd and LaMnO 3. Steady-state kinetic measurements at 400 °C have been modeled according to a single site or a dual site reaction mechanism representative of the cooperation between Pd and surface lattice oxygen species supplied by the support material. Impregnated catalysts are found sensitive to particle sintering inducing a deterioration of the metal-support interface. On the contrary, aging leads to strenghening of the metal-support interaction on sol–gel Pd catalysts which promotes methane conversion notably near three-way operating conditions. [ABSTRACT FROM AUTHOR]

The SCR performances of aged W-doped CeVO 4 catalysts were investigated in fast-, NO 2 - and standard conditions. Bulk CeV 1-x W x O 4 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.% H 2 O diluted in air at 600 °C. The impact of this aging process was investigated as a function of tungsten loading, with x varying in the range 0.02–0.15. A clear beneficial effect is distinguishable at high temperature, i.e., above 300 °C, associated to a sharp selectivity enhancement irrespective of the operating conditions and tungsten loading. On the contrary, a slight detrimental effect on the reaction rate is clearly discernible in standard-conditions below 300 °C. It was found that the thermal aging induces more extensive diffusion of V 5+ species assisted by the presence of substituted W 6+ . It was also demonstrated that tungsten diffuses more readily than V 5+ leading ultimately to a significant surface enrichment and the formation of Ce 4 W 9 O 33 mixed oxide evidenced from XRD and Raman spectroscopy. Hence, tungsten would rather act as a stabilizer than promoter avoiding the sintering of monomeric VO x species to more active polyvanadate species but also less selective. The gain observed in selectivity at high temperature can be equally explained by a greater stabilization of Brønsted acid sites and the preservation of the dispersion of monomeric vanadate species preventing the occurrence of ammonia oxidation. [ABSTRACT FROM AUTHOR]

Zr 1-x Ce x O x has been prepared by hydrolysis, in neutral medium, starting from rough ZrO 2 and CeO 2 materials as simple and cheaper synthesis method compared to sol-gel routes. The oxy-hydroxide precursors thus obtained were calcined under air at 450 °C, 900 °C and 1200 °C. The impact of those thermal treatments on the structure, texture and related redox properties has been investigated. Higher specific surface area than those observed on ceria were observed after calcination at low temperature, i.e., 450 °C. Above that temperature thermal sintering occurs having a detrimental effect on the specific surface area related to crystal growth more accentuated on CeO 2 . The formation of several Zr Ce mixed oxide phases formed by incorporation and substitution of Zr in the structure of ceria was characterized. A complete loss of specific surface area is noticeable after calcination at 1200 °C. XRD and SEM analysis revealed the formation of two mixed oxides structure, i.e. Ce 2 Zr 2 O 7.04 and Ce 2 Zr 2 O 7 corresponding to different redox behavior evidenced from H 2 -TPR experiments. [ABSTRACT FROM AUTHOR]

Bulk CeVO 4 catalysts prepared by hydrothermal synthesis have been developed for the ammonia-selective catalytic reduction of NO x to nitrogen. The catalytic properties were evaluated in standard- and fast-SCR conditions for stationary and mobile applications. The coexistence of low concentration of Ce 4+ species stabilized as CeO 2 with bulk CeVO 4 was found to be crucial for enhancing the intermediate formation of NO 2 from NO oxidation. Such cooperative effects impact on the rate of NO conversion to nitrogen regardless of the operating conditions. Aging processes under wet atmosphere at 500 °C and 600 °C did not destabilize the bulk zircon-type structure of CeVO 4 . No loss of vanadium was observed due to significant sublimation of vanadium. Despite poorer textural properties with regard to fresh CeVO 4 , aged CeVO 4 catalysts exhibit better catalytic properties in terms of rate of NO conversion and selectivity thus providing an alternative to less stable supported vanadia-based catalysts. Indeed, higher TOF values were measured in standard-SCR conditions at 200 °C on aged samples at 600 °C whereas an aging at 500 °C leads to selectivity enhancement at high temperature. All these changes can be rationalized based on the surface modifications of redox and acidic properties of vanadium species due to a slight extraction and stabilization of VO x species. [ABSTRACT FROM AUTHOR]

The Review describes the most significant results achieved in France in the field of heterogeneous catalysis over the last 10 years and placed in the context of international research. The focus lies on the research conducted in French academic laboratories, often in close collaboration with industrial partners. A wide range of heterogeneous catalysis is covered, including ab initio calculations, biomass conversion, catalytic cracking, catalyst characterization, CO2 conversion, Fischer-Tropsch, pollution abatement, power-to-gas and kinetics. [ABSTRACT FROM AUTHOR]

The autothermal dry reforming of methane was performed using natural illite clay as catalyst support. Nickel containing Ce or La promoted catalysts were characterized by XRD and XPS analysis before reaction, after the reduction step and also after 24 h of reaction. The highest catalytic stability was obtained on the La-based catalyst. This result was attributed to the formation of a britholite phase during the reaction resulting from the migration of lanthanum into the bulk. This particular phase could prevent the formation of the FeNi 3 alloy mainly observed on Ce-based material which is presumably much less active than metallic Ni particles towards the dry reforming reaction. A deep surface reconstruction, evidenced by XPS, proceeds during the reaction which complement structural characterization showing significant surface changes in Ni species that cooperate with the basic sites leading to higher catalytic activity and stability. [ABSTRACT FROM AUTHOR]

We report here on an in situ Raman investigation of stoichiometric and La-deficient LaFeO 3 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 Fe 2 III O 3 in the La-deficient solid was evidenced. This new phase was found to be stabilized under the same experimental conditions which also favor the volumetric expansion of the LFO unit cell. Eventually, this new iron oxide phase was found to be reduced under CO/He mixture and subsequently regenerated under NO. [ABSTRACT FROM AUTHOR]

LaFeCuO and LaCuO catalysts are investigated for three-way-catalysis application. LaFeCuO solids present interesting catalytic properties mainly with respect to hydrocarbon and CO oxidation and NO reduction in rich conditions with high N selectivity. The partial substitution of iron with copper leads to enhanced catalytic activity for oxidation reactions. This can be attributed to the higher reducibility of the solid as evidenced earlier by H-temperature-programmed reduction. The orthorhombic structure associated with LaFeCuO solids (x up to 0.2) revealed good thermal stability during catalytic cycles in stoichiometric, lean and rich conditions whereas the Ruddlesden Popper phase associated with LaCuO completely decomposed in rich conditions. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (N-CNTs) with macroscopic shaping were synthesized by a coagulation route using alginate as a coagulating agent and the as-synthesized sample was used as metal-free catalysts in the partial oxidation of H 2 S into elemental sulfur. The N-CNT beads display a relatively high desulfurization activity along with a high stability as a function of time on stream. The desulfurization performance of the N-CNT beads was also measured and compared to that of the Fe 2 O 3 /SiC catalyst. The N-CNT beads display a higher desulfurization activity under the similar reaction conditions with, however, lower sulfur selectivity due to the problem of diffusion of the reactant through the bead porosity. [ABSTRACT FROM AUTHOR]

The catalytic activity of unsupported CeVO solid was investigated in ammonia-SCR at various NO/NO ratio. CeVO 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 crucial parameter to get optimal bulk and surface properties. The evolution of intrinsic catalytic activity was compared with regards to bulk and surface properties extracted from extensive characterization. The stabilization of V in CeVO structure during NH-SCR reactions was observed even after thermal aging at high temperature. This opens new perspectives for vanadium-based catalysts in mobile sources applications. [ABSTRACT FROM AUTHOR]

Hierarchical structure characterized by the decoration of few-layer graphene (FLG) surface with a dense network of carbon nanofibers (CNF) was synthesized by Chemical Vapor Deposition. This hierarchical composite was further used as host matrix for the dispersion of nanodiamonds (ND) to produce a metal-free catalyst for the direct dehydrogenation (DH) process of ethylbenzene (EB) to styrene. The as-synthesized three-dimension ND/CNF-FLG composite displays excellent dehydrogenation activity and stability, especially under severe reaction conditions similar to those in the industrial process. Up to 600 °C with EB concentration of 10 vol.%, the ND/CNF-FLG catalyst displays a significant high DH activity of 56 . 9 mmol ST g ND − 1 h − 1 along with 91.3% styrene selectivity. In addition, no deactivation is observed during more than 70 h of test. The outstanding catalytic performance and the superior stability of the hybrid ND/CNF-FLG composite compared to the conventional carbon-based and promoted iron industrial catalysts, render it among the most promising metal-free catalyst for industrial direct dehydrogenation process. [ABSTRACT FROM AUTHOR]

Fe-based perovskites prepared with purposely lowered La-content, La 1− y FeO 3± 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 surface whereas the orthorhombic perovskite structure with smaller crystallite sizes remains unaffected. Catalytic activity of La 1− y FeO 3± δ was investigated under 3-way catalytic conditions. Surface composition optimisation strongly enhanced the catalytic performance of the perovskite by increasing the accessibility of the active Fe 3+ sites on perovskite and segregated Fe 2 O 3 . The estimation of Arrhenius parameters showed that CO and propylene oxidation seemingly proceed on different sites. [ABSTRACT FROM AUTHOR]

The straightforward “dressing” of macroscopically shaped supports (i.e.β-SiC and α-Al2O3) with a mesoporous and highly nitrogen-doped carbon-phase starting from food-processing raw materials is described. The as-prepared composites serve as highly efficient and selective metal-free catalysts for promoting industrial key-processes at the heart of renewable energy technology and environmental protection. [ABSTRACT FROM AUTHOR]

Hybrid materials consisting of graphene and nanodiamonds (NDs) can potentially display not only the individual properties of ND and graphene, but also those resulting from synergism when they closely interact. Herein, synergistic effects between ND and few-layer-graphene (FLG) containing between 5 and 20 layers of graphene are examined. The ND/FLG composite was prepared by mixing a suspension of FLG in ethanol with NDs. In this case, FLG plays the role of 2D support for dispersing ND clusters while NDs acting as a nano-spacer for partly preventing the re-stacking of the FLG sheets. The as-synthesized hybrid material was further used as metal-free catalyst for the steam-free direct dehydrogenation (DH) of ethylbenzene (EB) to styrene (ST). The DH activity obtained on the ND/FLG catalyst was benchmarked with other catalysts, i.e. commercial K-promoted Fe-based catalysts and carbon-based catalysts. The ND/FLG catalyst exhibits the highest DH activity among the tested catalysts, especially with a dehydrogenation specific rate as high as 19 mmol ST g ND −1 h −1 along with a selectivity toward styrene up to 95% at reaction temperature at 600°C. The catalyst displays a relatively high stability as a function of time on stream while the deactivated catalyst can be easily regenerated by an oxidative treatment in mild temperature conditions. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (N-CNT) were synthesized at 700 °C via the chemical vapour deposition (CVD) method and were used as catalysts in the oxygen reduction reaction (ORR) in 0.1 M KOH. The activity toward the ORR and the stability of these N-CNTs in alkaline solution were studied as a function of the reaction temperature and of the chemical treatment applied to the catalyst. The kinetic analysis of these catalysts was also carried out and compared to the ORR performance of the commercial Pt/C Vulcan XC72 catalyst. N-CNT-700BW catalyst without any chemical treatment after the CVD synthesis, possesses a half-wave potential E 1/2 of approximately 0.82 V vs. RHE, 50 mV lower than the E 1/2 value of Pt/C catalyst and a specific current density J k at 0.9 V = 5.46 mA/mg at T = 25 °C. Removal of the major part of the iron growth catalyst by a chemical treatment resulted in a strongly decreased but still measurable activity. The activation energy of the N-CNT-based catalyst was calculated and is around 38 kJ mol −1 at an ORR overpotential of 300 mV. Increasing the temperature of the electrolyte up to 75 °C leads to a positive shift of the half-wave potential of the reaction as well as an increase of the H 2 O 2 escape. The long-term stability test has also been conducted and indicates a good stability of the activity of the N-CNT-based catalysts under operation in alkaline media. [ABSTRACT FROM AUTHOR]

Nanodiamonds (NDs), a typical sp 3 -like carbon, have an average size less than 10 nm with a large surface-to-volume ratio, which contributes to a high surface activity than other types of carbon. However, the powder form of the material renders it difficult to use in large-scale applications, especially in the field of heterogeneous catalysis in which high pressure drop across the catalytic bed and difficulty of handling powder are the main drawbacks. In this work, a new hybrid structure consisting of nanodiamond-decorated porous β-SiC foam matrix has been investigated as a metal-free catalyst in the steam-free dehydrogenation of ethylbenzene into styrene. The hybrid foam catalyst displays an excellent catalytic specific rate and stability in the direct catalytic dehydrogenation of ethylbenzene (EB) to styrene. The dehydrogenation activity (12.87 mmol ST /g ND / h, moles styrene products per gram of nanodiamonds per hour) is about 10 times higher with respect to the commercial K-Fe-based catalyst and 3.8 times higher than that of powder-form NDs without losing styrene selectivity (S ST = 98%) and thus demonstrates the high catalytic efficiency of this metal-free catalyst for the studied reaction. This study shows a new development towards the practical use of such structured composite catalysts in the field of catalysis where high performance and stable catalyst are still under scrutiny. [ABSTRACT FROM AUTHOR]

EuFeO3 perovskite was considered as a case study of the cooperative effects of the rare earth and transition metal elements in the total catalytic oxidation of aromatic hydrocarbons. For this purpose, a EuFeO3 perovskite was prepared using the citrate route. Extensive characterization was performed via ex situ and in situ methods. EXAFS revealed that oxygen vacancies are formed in the nearest neighborhood of Fe and next-nearest neighborhood of Eu. Combining 151Eu and 57Fe Mössbauer experiments also suggested local oxygen defects in the proximity of the Eu cations during the reaction, as well as cooperative electron delocalization effects between Eu and Fe. XPS has shown the +3 oxidation state of both Eu and Fe cations and the relatively strong ionicity of the Fe-O chemical bonds, as suggested by the weakened 2p3/2 satellite in the Fe2p spectrum. A systematic change of this satellite with the A cation in AFeO3 perovskites was also discussed. The thermal treatment of the catalyst at 623 K, in air or toluene, was accompanied by a partial reduction of Fe and a partial oxidation of Eu, respectively. The interaction between the two elements appeared to be influenced mainly by the temperature and only slightly by the sample environment during further treatments. Catalytic oxidation of toluene on this perovskite led only to the production of carbon dioxide and water with no side-product formation from partial oxidation reactions. All the characterization and catalytic results preferably agree with a Volkenstein mechanism. [ABSTRACT FROM AUTHOR]

Highlights: [•] Development of a condensed-phase kinetic mechanism for NH4NO3 decomposition. [•] Validation against original TGA-XRD-DSC experiments and literature data. [•] Impact of heating rate on reactions pathways and N-selectivity. [•] Impact of gas-phase reactions involving nitramide and nitric acid. [ABSTRACT FROM AUTHOR]

Highlights: [ • ] NO x storage and NO oxidation on Fe-BEA was studied through FTIR-spectroscopy. [•] Nitrites were thermally stable at temperatures up to 100°C. [•] NO3 were formed on Al atoms, as well as on Fe sites. [•] NO uptake on Fe-BEA was limited and NO oxidation was observed on Al and Fe sites. [ • ] IR observations were modeled through a multi-site kinetic model. [ABSTRACT FROM AUTHOR]

New insights into reaction mechanism for catalytic methane combustion are provided in broad operating conditions on Pd/La 0.7 MnO 3 as model natural gas vehicle catalyst. Under lean and dry conditions, a dual mechanism is suggested with active sites combining reactive oxygen species from La 0.7 MnO 3 and palladium instead of single site reaction mechanism. Aging in wet atmosphere has no consequence on the kinetic behavior. On the other hand, in wet atmosphere near the stoichiometry, strong accumulation of hydroxyl groups on the support would suppress the metal-support interface. Accordingly, methane combustion would take place only on Pd particles. [Display omitted] • C-H bond breaking during methane activation assisted by reactive oxygen species from La 0.7 MnO 3. • High stability of Pd-La 0.7 MnO 3 interface upon aging in wet and lean conditions. • Suppression of reactive O species on La 0.7 MnO 3 in the presence of steam due to OH accumulation. • Single Pd sites versus dual sites at Pd-La 0.7 MnO 3 interface governed by the presence of steam. [ABSTRACT FROM AUTHOR]