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Molecular imprinting of polymer matrices enables the creation of template-shaped cavities with high affinity for molecules of given shape and size. Here we introduce a surface molecular imprinting strategy to control the hydrogenation selectivity of various aromatic molecules over a supported palladium catalyst. This strategy involves the sequential adsorption over the metal surface of an aromatic template molecule followed by poisoners, resulting in the formation of non-poisoned active islands of predetermined shape and size. Because of steric constraints, these active islands exhibit high selectivity in the chemical conversion of aromatic molecules that correspond in size and shape to the templates. The elaborated strategy enables a practical application relevant to selective hydrogenation and removal of carcinogenic benzene from mixtures of aromatics. Molecular imprinting can facilitate size- and shape-selective reactions beyond traditional approaches based on porous materials, but is still not fully established for heterogeneous catalysts. Here a molecular imprinting approach is introduced to generate a supported palladium catalyst for the selective hydrogenation of benzene from mixtures of aromatic molecules.

The aerobic oxidation of monoalcohols and diols to acetals is an important academic and industrial challenge for the production of fine chemicals and intermediates. The existing methods usually rely on a two-step process in which alcohols are first oxidized to aldehydes over metal catalysts (Ru, Pt, Pd) and then acetalized using acids. Due to the instability of aldehydes, how to avoid over-oxidation to their respective carboxylic acids and esters is a long-standing challenge. For this reason, certain non-conjugated dialdehydes have never been successfully produced from diol oxidation. Hereby we report a Ru@metal-organic framework (MOF) tandem catalyst containing ultra-fine Ru nanoparticles (< 2 nm) for direct alcohol to acetal conversion of monoalcohol and diols with no formation of carboxylic acids. Mechanistic study reveals that the presence of Lewis acid sites in the MOF work in concert with Ru active sites to promptly convert aldehydes to acetals thereby effectively suppressing the formation of over-oxidation byproducts.

International audience; Today development of efficient catalytic systems for selective oxidation of alcohols to aldehydes remains not only a major concern in basic chemistry research but also a significant challenge for the chemical industry. One promising green and sustainable approach to increase the selectivity as well as waste reduction and to minimize the use of toxic and/or hazardous substances is the development of selective electro-catalytic acceptorless dehydrogenation method. By that, it will be possible to facilitate catalyst recovery and reutilization as well as producing only hydrogen as the by-product. Quinones as principal redox-active moieties within natural organic materials play a key role in electron-transport processes of biological systems. Herein, by taking the oxidation of furfuryl alcohol (FA) in dimethyl sulfoxide (DMSO) as a model reaction, 14 quinone derivatives from 3 families (benzoquinones (BQs), naphthoquinones (NQs), and anthraquinones (AQs)) have been surveyed as a hydrogen acceptor mediators. We demonstrate that, only for three-member ring quinones such as 9,10-anthraquinone-2,6-disulfonic acid (AQDS), which are stable during electrocatalysis, a significant increase of the selectivity to furfural with addition of AQDS is achieved. The effect is assigned to strong intermolecular interaction between FA and quinone dianion (Q 2−) with selective transformation to aldehyde its regeneration to quinone and hydrogen production over cathode surface. This study assesses and validates the potential of quinones as electrocatalytic hydrogen acceptor mediators to impel the selective oxidation of alcohol to aldehydes.

International audience; Selective aerobic oxidation of alcohols to corresponding carbonyl compounds is one of the most important challenges in the modern chemical industry. The existing metal based heterogeneous catalysts provide low selectivity due to over-oxidation of aldehydes to acids and esters. We have found that coating of Ru nanoparticles by disodium anthraquinone-2,6-disulfonate (SQ) results in selective oxidation of aliphatic, unsaturated and aromatic alcohols to aldehydes. Analysis of core-shell Ru@SQ catalyst shows strong interaction between Ru and SQ leading to change of their electronic state and structure. In-situ study of alcohol oxidation using FTIR and electrochemistry indicates on hydrogen abstraction by shell quinone species with hydrogen transfer by quinone to Ru core for water generation. Thus, the catalyst behavior mimics nano-electrocell by separation of oxidation reaction over quinone and reduction of oxygen over Ru providing higher selectivity to aldehyde.

This work presents a highly efficient catalytic hydrogenation system developed for the selective transformation of tertiary N,N-dimethyldodecanamide and secondary azepan-2-one amides to the corresponding amines. Industrial hydrogenation catalysts Pd/Al2O3, Pt/Al2O3 and Rh/Al2O3 were modified with vanadium (V) or molybdenum (Mo) species as oxophilic centres. The modified catalysts were prepared by deposition of V or Mo precursor on supported catalysts via impregnation method. The catalysts were characterized by ICP-OES, XRD, XPS, H2-TPR, FTIR, CO-chemisorption, TEM, SEM-EDX and TGA. Modified Rh-V/Al2O3 catalyst displayed the best performance affording high yield and selectivity > 95 % to the desired tertiary and secondary amines at moderate reaction conditions of T O bond of the carboxamides into the desired amines.

International audience; The catalytic hydrogenation of CO2 to formic acid is one of the most promising pathways towards a renewable hydrogen-storage system. The reaction is usually performed in aqueous phase in the presence of basic molecules over homogeneous or heterogeneous catalysts, generating relatively dilute formate solutions (

This paper reports on the “in-situ” preparation-deposition and reduction of Ni-Cu nanoparticles (NPs) on γ-Al 2 O 3 as support, using a green and elegant one-pot synthesis approach. Pristine and supported Ni-Cu NPs were evaluated as (de)hydrogenation catalysts for the Guerbet reaction of 1-octanol and compared with a classic impregnated and “ex-situ” reduced NiCu on γ-Al 2 O 3 catalyst. XRD reavealed that the degree of Ni-Cu nano-alloying was insignificant in the one-pot preparation method, resulting in Ni-Cu nanocomposites, while the degree of nano-alloying was resp. low and very high in the pristine nanoparticles (NPs) and the classic impregnated catalyst. The degree of reduction was very similar for both the in-situ and ex-situ reduction treatments of the supported catalysts as demonstrated by H 2 chemisorption. The “in-situ” prepared supported Ni-Cu NPs showed an enhanced kinetics when compared to the unsupported pristine Ni-Cu NPs, showing a beneficial effect of the metal-support interaction, however the classic impregnated catalyst showed overall the best kinetics, selectivity and stability for the Guerbet reaction of 1-octanol.

Supported metal catalysts have found broad applications in heterogeneous catalysis. In the conventional bifunctional catalyst, the active metal sites are associated with the metal nanoparticles, while the acid sites are usually localized over the oxide support. Herein, we report a novel type of supported metal bifunctional catalyst, which combined the advantages of the promotion and bifunctionality. The catalyst was designed by the pretreatment of supported palladium catalysts with bromobenzene. The promotion with bromine creates Bronsted acid sites, which are localized directly on the surface of metal nanoparticles. An intimacy between metal and acid functions in this bifunctional catalyst generates unique catalytic properties in hydrodeoxygenation of 5-hydroxymethylfurfural to dimethylfuran, occurring with the yield up to 96% at ambient temperature under 5 bar of H-2. The catalyst exhibits stable catalytic performance.

Selective synthesis of ethers from biomass derived carbonyl compounds is an important academic and industrial challenge. The existing processes based on strong acid or metallic catalysts cannot provide high selectivity to ethers due to the occurrence of side reactions. Hereby we propose a Pd-I bifunctional heterogeneous catalyst for the selective reductive etherification of aldehydes with alcohols. Extensive catalyst characterizations uncovered the presence of iodine species on the surface of Pd nanoparticles. Heterolytic dissociation of hydrogen on the I-Pd surface sites leads to the "in situ" generation of a Bronsted acid, which promotes the reaction toward the corresponding ethers with extremely high selectivity under very mild reaction conditions.

Au/MgO and Au/Mg(OH)-type catalysts for CO oxidation reaction were prepared by using two different synthesis methods in presence of either an aqueous or methanol phase. The influence of the porous and morphological properties of the starting magnesium oxide supports was analyzed and correlated with the catalytic performances of the final gold-supported catalysts. It was found that the deposition of gold in the presence of methanol as a solvent avoids the total rehydration of the MgO support and maintains the textural and morphological properties of the starting oxides. The support synthesized by a surfactant-assisted hydrothermal route, having a combined meso-macroporous structure (i.e., MgO-P) showed a positive influence on the CO oxidation reaction as it favored the dispersion of gold and the surface-to-gas phase interaction during the catalytic process., This work was partially funded by the IWT—Belgium.

A series of Ni-Cu hydrotalcite-derived mixed oxides have been synthesized and evaluated as heterogeneous catalysts for the dimerization of linear aliphatic alcohols to afford beta-branched Guerbet alcohols. The use of the hydrotalcite-structured catalyst precursor highly favors the catalyst stability. This Cu/Ni catalyst has an enhanced reducibility of Ni2+ species under reaction conditions, favoring the hydrogen transfer and hydrogenation capacity of the catalyst system. Catalytic results are reported for C-8, mixed C-8/C-10, and C-18 alcohol feeds, with full conversions and Guerbet product purities of 72.5-96 %.

International audience; We report here that CC coupling in tertiary amines for the synthesis of long chain and hindered amines might be efficiently performed over Pt and Pd catalysts. The mechanism study confirms similarity with the Guerbet reaction through dehydrogenation of the alkyl group and subsequent attack of the acarbon atom by an alkyl group of another molecule. Finally, secondary amines and tertiary amines with longer alkyl chains are formed.

Silver modified manganite (LaSrAgMn) and ferrite (LaSrAgFe) perovskites were synthesized with different Ag loadings and tested for the soot oxidation reaction at low oxygen concentrations (i.e. 1 vol%), as encountered in gasoline direct injection (GDI) engines application. The state and location of Ag determine the catalytic performances of perovskites. On ferrites, Ag is either partially incorporated on the structure or present on the surface as large agglomerates. Lattice Ag+ cations are not catalytically active. Furthermore, large surface Ag particles partially cover surface oxygen vacancies and block their ability to adsorb oxygen. On the other hand, small clusters of Ag and AgO as well as a surface Ag1.8Mn8O16 additional hollandite-type phase are stabilized on manganites surface, improving the reducibility and acting as active sites for soot oxidation.

The catalytic performances of substituted anthraquinones were investigated in catalytic oxidation of alcohols like cyclohexanol, benzyl alcohol and 5-hydroxymethylfurfural (HMF) to carbonyl compounds (cyclohexanone, benzyl aldehyde and diformylfuran). The reduction potential of anthraquinone plays the key role in the oxidation reactions. TOF numbers and selectivities to carbonyl compounds pass through the maximum with increase of the reduction potential. The maximum activity and selectivity (>80 %) is observed for sulfonated and carboxylated anthraquinones having intermediate reduction potentials (≈ 0.1-0.2 V vs SHE). Grafted 2-carboxyanthraquinone catalyst has demonstrated comparable catalytic performance to the parent molecule and might be used as heterogeneous catalyst. The oxidation reaction was found to have radical character with transfer of hydrogen from alcohol to anthraquinone and subsequent oxidation of hydrogenated anthraquinone by oxygen.

Layered double hydroxides (LDHs) and derived materials have been widely used as heterogeneous catalysts for different types of reactions either in gas or in liquid phase. Among these processes, the valorization/upgrading of lignocellulosic biomass and derived molecules have attracted enormous attention because it constitutes a pivotal axis in the transition from an economic model based on fossil resources to one based on renewable biomass resources with preference for biomass waste streams. Proof of this is the increasing amount of literature reports regarding the rational design and implementation of LDHs and related materials in catalytic processes such as: depolymerization, hydrogenation, selective oxidations, and C–C coupling reactions, among others, where biomass-derived compounds are used. The major aim of this contribution is to situate the most recent advances on the implementation of these types of catalysts into a lignocellulosic-feedstock biorefinery scheme, highlighting the versatility of LDHs and derived materials as multifunctional, tunable, cheap and easy to produce heterogeneous catalysts.

Analytical chemistry 89(3), 2123 - 2130 (2017). doi:10.1021/acs.analchem.6b04828, Using X-ray absorption near edge structure (XANES) spectroscopy, information on the local chemical structure and oxidation state of an element of interest can be acquired. Conventionally, this information can be obtained in a spatially resolved manner by scanning a sample through a focused X-ray beam. Recently, full-field methods have been developed to obtain direct 2D chemical state information by imaging a large sample area. These methods are usually in transmission mode, thus restricting the use to thin and transmitting samples. Here, a fluorescence method is displayed using an energy-dispersive pnCCD detector, the SLcam, characterized by measurement times far superior to what is generally applicable. Additionally, this method operates in confocal mode, thus providing direct 3D spatially resolved chemical state information from a selected subvolume of a sample, without the need of rotating a sample. The method is applied to two samples: a gold-supported magnesia catalyst (Au/MgO) and a natural diamond containing Fe-rich inclusions. Both samples provide XANES spectra that can be overlapped with reference XANES spectra, allowing this method to be used for fingerprinting and linear combination analysis of known XANES reference compounds., Published by American Chemical Society, Columbus, Ohio

Mg-Zn-Al hydrotalcites and derived mixed oxides with different Mg2+-to-Zn2+ ratios were prepared by co-precipitation in super-saturated conditions, followed by thermal decomposition at 500 A degrees C. The synthesized materials were evaluated as catalysts for the self-condensation of octanal in order to establish structure-to-functionality properties of the prepared materials. The presence of zinc affects the structural and textural properties of the as-synthesized hydrotalcites and derived mixed oxides, and provokes a remarkable modification on the acidic-basic properties of the materials as studied by CO2 and NH3-TPD. The presence of Zn2+ caused an increment in the concentration of surface acidic sites compared to the binary Mg-Al system. The samples characterized by a Zn/Mg ratio aecurrency sign1 showed the optimal ratio of acidic and basic sites and the best catalytic performance for the production of the alpha,beta-unsaturated aldehyde. The reconstruction of the layered materials (starting from the mixed oxides) caused an increment in the concentration of surface OH- groups, further modifying the selectivity of the reaction.

Ce{sub 0.9}M{sub 0.1}O{sub 2-{delta}} mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO{sub 2} (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F{sub 2g} Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce{sup 4+}/Ce{sup 3+}. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO{sub 2}, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area. - Graphical abstract: In this work, Ce{sub 0.9}M{sub 0.1}O{sub 2-{delta}} mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO{sub 2} (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shiftmore » of the F{sub 2g} Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce{sup 4+}/Ce{sup 3+}. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO{sub 2}, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area. Highlights: > Lanthanide doped ceria as catalytic supports for CO oxidation reaction. > A higher concentration of oxygen vacancies promotes a higher catalytic activity. > Eu-doped ceria shows improved catalytic properties for the CO oxidation reaction.« less

Transition metal (Cu, Co, Ni and Zn)-modified cryptomelane-type manganese dioxide nanomaterials were synthesized by the milling method. The obtained solids have been characterized by means of X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy (SEM and TEM), N2 adsorption–desorption measurements at 77 K, Raman spectroscopy and temperature programmed reduction (TPR-H2) showing similar structural and textural properties. All the solids were active in the preferential oxidation of CO in the presence of hydrogen (PROX), being the modified with copper the most active. The catalytic activity correlates fairly well with the TPR results, finding higher CO conversion for the material with higher reducibility (OMS-Cu). The O2 selectivity, measured as ([CO]in − [CO]out/2[O2]in − [O2]out) × 100, is very similar for all synthesized materials.

A series of commercial Mg–Al hydrotalcites have been used as catalyst precursors for the methanolysis of sunflower oil. The solids were characterized by low Mg/Al molar ratios in the 0.5–2.3 range. Additionally, a solid consisting mainly of Mg(OH) 2 but containing some Al (4.2 wt.%) was also employed. The as-received materials were inactive for biodiesel synthesis so calcination and rehydration in boiling water were considered as activation treatments. Among the calcined solids, only the material consisting of MgO was significantly active, achieving about 50% oil conversion after 24 h at 60 °C, methanol/oil molar ratio of 12 and 2 wt.% of catalyst. The effects of the calcination temperature in the 350–700 °C range have been investigated; calcination at 500 °C led to the best catalytic performance. In the case of the rehydrated materials, only the solids with the highest Mg/Al molar ratios recovered a well-ordered layered double hydroxide structure. These samples showed an improved catalytic activity compared with their calcined counterparts. A good correlation between catalytic activity and the basic properties determined using Hammett indicators and benzoic acid titration has been found. Rehydrated hydrotalcites were slightly more selective to biodiesel (75%) at intermediate levels of oil conversion than the calcined counterparts (66%). It has been verified that no Mg or Al leaching in the reaction mixture took place; however, the rehydrated samples deactivated significantly. In the case of MgO, after washing and calcination, the recycled catalyst gave 68% of the original oil conversion.

Gold-supported ceria and europium-doped ceria catalysts were prepared by the deposition−precipitation method. The influence of the pretreatment atmosphere and temperature on the concentration of oxygen vacancies and gold dispersion on the Au/CeEu(10) catalyst under actual reaction conditions was investigated by “in situ” X-ray diffraction and Raman analysis. By Raman spectroscopy, a preferential interaction of the gold with the support across the oxygen vacancies was established and correlated with the gold dispersion. The increase in the concentration of oxygen vacancies in the presence of hydrogen induces changes in the gold crystallite size by breaking-off and migration of gold nanoparticles toward the oxygen vacancies on the CeEu(10) support. The activity of the Au/CeEu(10) solid in the CO oxidation reaction was significantly improved when the catalyst was preactivated in a reducing atmosphere. This trend could be associated with the redispersion of gold together with the increase in the concentration...

© The Royal Society of Chemistry 2015. The Guerbet condensation reaction is an alcohol coupling reaction that has been known for more than a century. Because of the increasing availability of bio-based alcohol feedstock, this reaction is of growing importance and interest in terms of value chains of renewable chemical and biofuel production. Due to the specific branching pattern of the alcohol products, the Guerbet reaction has many interesting applications. In comparison to their linear isomers, branched-chain Guerbet alcohols have extremely low melting points and excellent fluidity. This review provides thermodynamic insights and unravels the various mechanistic steps involved. A comprehensive overview of the homogeneous, heterogeneous and combined homogeneous and heterogeneous catalytic systems described in published reports and patents is also given. Technological considerations, challenges and perspectives for the Guerbet chemistry are discussed. ispartof: Catalysis Science & Technology vol:5 issue:8 pages:3876-3902 status: published

Nanometric yttria-stabilized zirconia (3 mol% yttria, SC-3YSZ) was synthesized using an innovative supercritical carbon dioxide-aided sol–gel process and used as a support for NOx storage catalysts. Wash-coats composed of noble metals (Pt and Rh) dispersed on 3YSZ were deposited inside the porosity of mini-diesel particulate filters. Commercial and SC-3YSZ powders were used as supports independently and mixed. NOx storage/reduction performances were compared under cycling conditions according to the YSZ support surface area, the washcoat localization inside the DPF and the metallic dispersions. All the results emphasize that the presence of high specific surface area SC-3YSZ inside the DPF improves the NOx conversion, the N2 selectivity and the NOx storage capacity. This enhancement of the catalytic properties was linked with the increase in both the metallic dispersion and the number of storage sites on the catalyst surface.

RX+CARE+MTS:CZA:ABO:FBS:PVE; International audience; La0.6Sr0.4BO3 type-perovskites (with B = Fe, Mn or Ti) were synthesized by a complex route from the thermal decomposition of the chelated nitrate precursors, as soot oxidation catalysts under low oxygen partial pressures. The nature of the B-site cation modifies the morphology, the structural symmetry, the charge compensation mechanism and the redox properties. The generation of oxygen vacancies is predominant in LSF while an increase in the oxidation state of B cations occurs in LSM and LST, respectively. A direct link was established between the reducibility of the perovskites and their ability to oxidize soot. Fe and Mn-based perovskites exhibit similar catalytic behaviors, superior to LET, which are attributed to the presence of oxygen vacancies in LSF and Mn4+ cations in ISM. This latter redox property is particularly suitable to oxidize soot at low oxygen partial pressures, as encountered in gasoline direct injection engine exhausts. (C) 2014 Elsevier B.V. All rights reserved.

The catalytic activity of metal hexacyanometallates (Prussian blue-type coordination polymers) was tested in photoactivated water oxidation by [Ru(2-2′-bpy)3]2+/persulfate system at pH close to neutrality. This screening shows that manganese and cobalt N-coordinated compounds are able to catalyze the oxygen evolution reaction. Mn hexacyanometalates show low activity. Co hexacyanometalates, in contrast, appear highly active and promote robust catalysis with excellent quantum yield (≤88%), even in acidic media. Our results indicate that these catalysts are viable candidates for a photoactivated water oxidation process as part of an artificial photosynthesis scheme.

Hydrogen produced from the conversion of hydrocarbons or alcohols contains variable amounts of CO that should be removed for some applications such as feeding low-temperature polymer electrolyte membrane fuel cells (PEMFCs). The CO preferential oxidation reaction (PROX) is particularly well-suited for hydrogen purification for portable and on-board applications. In this work, the synthesis and characterization by XRF, BET, XRD, Raman spectroscopy and H 2-TPR of a gold catalyst supported on a copper-cerium mixed oxide (AuCeCu) for the PROX reaction are presented. The comparison of this catalyst with the copper-cerium mixed oxide (CeCu) revealed that the experimental procedure used for the deposition of gold gave rise to the loss of reducible material by copper lixiviation. However, the AuCeCu solid was more active for CO oxidation at low temperature. A kinetic study has been carried over the AuCeCu catalyst for the PROX reaction and compared with that of the CeCu catalyst. The main difference between the models affected the contribution of the CO adsorption term. This fact may be related to the surface electronic activity produced by the interaction of the cationic species in the AuCeCu solid, able to create more active sites for the CO adsorption and activation in the presence of gold.

AIR+WHE; Manganese oxide octahedral molecular sieves (cryptomelane structure) were synthesized by a solvent-free method and tested in the total oxidation of CO (TOX), and preferential oxidation of CO in presence of hydrogen (PROX). The influence of Cu in the cryptomelane structure was evaluated by several characterization techniques such as: X-ray fluorescence (XRF), thermogravimetric analysis (TGA), hydrogen temperature programmed reduction (TPR-H-2) and X-ray photoelectron spectroscopy (XPS). The Cu-modified manganese oxide material (OMS-Cu) showed very high catalytic activity for CO oxidation in comparison to the bare manganese oxide octahedral molecular sieve (OMS). The improved catalytic activity observed in OMS-Cu catalyst was associated to a high lattice oxygen mobility and availability due to the formation of Cu-Mn-O bridges. In addition, under PROX reaction conditions the catalytic activity considerably decreases in the presence of 10% (v/v) CO2 in the feed while the same amount of water provokes an improvement in the CO conversion and O-2 selectivity. (c) 2012 Elsevier B.V. All rights reserved.

A kinetic study of the preferential oxidation of CO in H2 rich streams (CO-PrOx) over a cerium-copper oxide (CeCu) and a gold catalyst supported on cerium-iron oxide (Au/CeFe) is presented. The gold catalyst is very active but the CeCu oxide is more selective. A kinetic model describing the CO-PrOx system with CO2 and H2O in the feed has been formulated considering the oxidation of CO and H2 and the reverse water-gas shift reaction. The rate equations have been implemented in computational fluid dynamics codes to study the influence of the operating variables on the CO-PrOx in microchannels and microslits. The CeCu catalyst is the only one capable of achieving final CO contents below 10-100ppmv. Due to the opposite effect of temperature on activity and selectivity there is an optimal temperature at which the CO content is minimal over CeCu. This temperature varies between 170 and 200°C as the GHSV increases from 10,000 to 50,000h-1. Simulations have evidenced the very good heat transfer performance of the microdevices showing that the CO-PrOx temperature can be controlled using air as cooling fluid although the inlet temperature and flow rate should be carefully controlled to avoid reaction extinction. Both microchannels and microslits behaved similarly. The fact that the microslits are much easier to fabricate may be an interesting advantage in favour of that geometry in this case.

9 Hadjar, A. Hernandez, W. Y. Princivalle, A. Tardivat, C. Guizard, C. Vernoux, P.; The NO(x) abatement efficiency of an electrochemical NO(x)TRAP catalyst Pt-Ba/YSZ was investigated at 500 degrees C with different oxygen partial pressures in the storage phase. Cathodic polarization was found to promote the NO(x) storage capacity even under lean-burn conditions. The duration until full NO(x) storage was drastically increased by similar to 80 s in the presence of 6% of oxygen. During regeneration phases. NO electrochemical reduction occurs and can remove similar to 10% of NO(x). Electrochemical activation of the NO(x) storage capacity was linked with the generation of oxygen vacancies on the YSZ surface induced by negative polarization. (C) 2011 Elsevier B.V. All rights reserved.