Search

The adsorption of CO in the temperature range of 300–713 K on the PtSn particles of a reduced (H2, 713 K) 1.2%Pt-2.7%Sn/Al2O3 catalyst is studied by FTIR spectroscopy to reveal the geometric and electronic effects of Sn on the Pt sites. By comparison with a 1.2% Pt/Al2O3 it is shown that Sn (a) suppresses the Pt sites forming bridged CO species due to a geometric effect and (b) displaces the IR band of a linear CO species on Pt sites at 300 K from 2066 cm−1 to 2044 cm−1 due to an electronic effect. According to the AEIR method, the change in the IR band on the PtSn particles with the increase in Ta in isobaric condition (PCO = 1 kPa) provides the heats of adsorption of the linear CO species (named L1PtSn) at high (58 kJ/mol) and low (130 kJ/mol) coverages. By comparison with the values of the linear CO species on Pt particles (named LPt): 220 and 106 kJ/mol at low and high coverages, respectively, these values reveal the strong impact of the electronic effect of Sn on the heats of adsorption of CO. For Ta > 463 K there is a reconstruction of the PtSn particles due to the segregation of Sn as SnOx species associated with an enrichment of the surface in Pt. On the reconstructed PtSn particles, a new IR band is observed at 2057 cm−1 after adsorption of CO at 300 K ascribed to a new L2PtSn CO species. Its heats of adsorption are significantly higher than those of the L1PtSn species: 165 and 65 kJ/mol at low and high coverages. Moreover, successive reconstruction/H2 reduction at 713 K cycles leads to a sintering of the PtSn particles associated to the progressive increase in the heats of the L2PtSn CO species until a value at low coverage: 210 kJ/mol similar to that of the LPt species whereas at high coverage a significant difference exists between the two species (70 and 115 kJ/mol for L2PtSn and LPt, respectively). These data show that the impacts of Sn on the heat of adsorption of the linear CO species on the Pt sites are dependent on (a) the Pt/Sn surface ratio which changes with reconstruction and the particle size and (b) the coverage of the Pt sites. The comparison of the heats of adsorption of the L CO species on the fresh, reconstructed and aged PtSn particles with experimental and theoretical literature data reveals that they are consistent with some of them.

The influence of gas/liquid mass transfer on the valorisation reaction of CO2 with epoxides using epichlorohydrin in a stirred batch reactor was investigated in this study. The rate of absorption of CO2 into the liquid was studied in a dynamic way between 50 and 90 °C and at different stirring speeds (100–500 rpm). Two different systems were observed: (i) CO2/epichlorohydrin and (ii) CO2/epichlorohydrin/catalyst, in order to compare and determine the mass transfer coefficient and the enhancement of the absorption when the latter takes place in the presence of a catalyst. The results suggest that the valorisation reaction followed a slow reaction regime in which the reaction did not occur in the mass transfer film but instead took place within the liquid bulk. Therefore, the reaction rate seemed to control the overall process, but according to the specific reaction regime found, both the liquid holdup and the interfacial area should be enhanced to increase the rate of the reaction and the efficiency of the process. Under the conditions studied in this work, the mass transfer coefficient of the liquid phase (kLa) was found to be in the range of 1.0 × 10−3 to 1.0 × 10−2 s−1 and the enhancement factor (E) was between 0.4 and 0.9.

International audience; Cheap and readily available 2-aminopyridine and related compounds can be used as organocatalysts for the conversion of epoxides into cyclic carbonates. This reaction gives high conversions under solvent-free conditions and is amenable to a kilogram-scale conversion under mild conditions.

A structured catalyst consisting of carbon nanofibers grown on the surface of cordierite monoliths was applied in the catalytic ozonation of emerging organic micropollutants. The stability of the catalyst was tested in a long term experiment, showing some initial deactivation related to the formation of oxygenated groups on the carbon surface, but proving to be stable in the long run. The application of the monolith in a triphasic system was demonstrated to be favorable when compared to a biphasic system. The addition of catalyst did not improve the removal of the parent pollutants, but improves the mineralization degree, which is relevant, since the resulting by-products may be more harmful than the parent compounds. The application of the process using a natural water matrix showed some inhibition of the catalytic activity for some pollutants, mainly connected to the radical scavenging properties of some inorganic compounds. However, the catalyst still showed significant activity during these experiments.

We present a study on CoCr–MCM-41 catalysts with stable nm-sized particles. The focus is their promoting effect on the synthesis of Single-Wall Carbon Nanotubes (SWNT). Bimetallic CoCr–MCM-41 catalysts were synthesized by combined grafting and incorporation of metals in the framework. This synthesis allowed an increase in the maximum metal loading in the MCM-41 framework while maintaining nm-sized Co particles stable in high-temperature reactive environments. The SWNT yield was increased by more than 100% from the Co–MCM-41 catalyst. Cobalt is responsible for SWNT nucleation. The role of chromium is to anchor small cobalt particles during reduction and prevent their sintering into large unreactive particles. A larger fraction of the cobalt in the bimetallic catalysts becomes available for the SWNT synthesis when compared to the monometallic one, leading to a significant yield increase. Another effect of the addition of Cr was a shift of the SWNT diameter distribution to smaller nanotubes.

Different synthesis procedures including hydrothermal, solvothermal, and chemical reduction routes have been previously developed by our group for the production of bismuth nanotubes (BiNTs). It has been shown that a post synthesis treatment with sodium borohydride greatly improves nanotube structure and yield. High-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy were employed to characterize the bismuth nanotubes. Bismuth has a low melting point and this contributes to energy induced structural changes during in situ TEM and Raman observations. Here, HRTEM and Raman techniques were employed to characterize the products and to gain more insight by using in situ observation of an energy-induced morphology change (EiMC) of the bismuth nanotubes. It is shown that the change of the morphology of the bismuth nanotubes is accompanied by (a) an oxidation process (Bi° → Bi3+) and (b) a progressive rhombohedral-Bi → β-Bi2O3 → α-Bi2O3 phase transformation.

A silica-supported cobalt catalyst has been developed via incipient wetness impregnation for high-yield synthesis of single-walled carbon nanotubes (SWNTs). Co/SiO2-impregnated catalysts have not been observed to be efficient for SWNT synthesis. Using an appropriately chosen precursor, we show that effective catalysts can be obtained for SWNT synthesis with yields up to 75 wt %. Detailed characterization indicates that the active sites for SWNT synthesis are small cobalt particles resulting from the reduction of a highly dispersed surface cobalt silicate species. The SWNTs produced by this catalyst are of high quality and easy to purify, and the process is simple and scalable.

In this paper, we demonstrate a new route for synthesis of bismuth nanotubes (BiNTs) based on chemical reduction using sodium borohydride. A comparison and an optimization of different synthesis procedures including hydrothermal and solvothermal synthesis for the production of BiNTs are presented. The effects of parameters such as the bismuth precursor, temperature, and reagent mixing process on nanomaterial structure were evaluated. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy were employed to characterize the products from the different reaction schemes. A postsynthesis sodium borohydride treatment improved both yield and nanotube structure for all syntheses studied. Different morphologies of the bismuth nanostructures were observed depending on the synthesis method selected.

The effect of manganese addition to the Co-MCM-41 catalyst on the synthesis of single wall carbon nanotubes (SWNT) by CO disproportionation was characterized. The ratio between the two metals in the MCM-41 framework was varied, and its effect on the resultant SWNT distribution was studied and compared with the results obtained for the monometallic Co-MCM-41 catalyst. Methods including temperature-programmed reduction, X-ray absorption fine structure, thermogravimetric analysis, TEM imaging, and Raman and fluorescence spectroscopy were employed to characterize the behavior of the catalysts under the SWNT synthesis conditions and the diameter and structure distribution of the resultant nanotubes. We found that addition of Mn to the Co-MCM-41 catalyst promotes the growth of SWNT, leading to synthesis of high yield, small diameter SWNT. Manganese does not act in the nucleation of SWNT but acts as an anchoring site for cobalt particles formed during the synthesis process as shown by X-ray absorption.

This paper studies the effect of chromium addition to the Co-MCM-41 catalyst in the synthesis of single wall carbon nanotubes (SWNT). The molecular ratios between the two metals have been varied in the catalyst template and their effect on the synthesized SWNT distribution has been studied. By adding Cr to the Co-MCM-41 monometallic catalyst, the diameter distribution of the synthesized SWNT has shifted towards smaller diameter tubes. This shift was correlated with the development of a bimetallic oxide in the MCM-41 framework during catalyst synthesis. By use of fluorescence spectroscopy, the relative abundance of certain tube chiralities has been seen to increase in the bimetallic samples compared to the monometallic ones as for example the (6,5) nanotube. X-ray absorption analysis of the catalyst before, during and after the SWNT synthesis, suggested that the use of a less reducible oxide (chromium oxide) to anchor clusters of a nanotube growth catalyst (cobalt clusters) is an important general tool for engineering the resultant nanotube properties. The addition of chromium has been seen to affect both the reducibility of the cobalt ions and the size of the resultant particles during the SWNT synthesis process.

Highly dispersed cobalt on SBA-15 was successfully prepared by a post synthesis grafting of cobalt. Of the cobalt precursors tested, Co(II) acetylacetonate was found to be the best source for high dispersion of cobalt. The Co-SBA-15 catalysts were characterized with different techniques: N2 physisorption, XRD, TPR, TEM, and X-ray adsorption analysis. The mesoporous structure of SBA-15 was retained after cobalt grafting with up to 10 wt % Co loading. There were no large cobalt oxide particles formed, which indicates all the cobalt ions are highly dispersed on the surface and the direct bonding to the silica surfaces results in a high reduction temperature (1123 K) relative to Co oxides. X-ray absorption analysis demonstrates a local structure of Co ions with all Co ions isolated and bonded with oxygen. XANES analysis requires that the local environment for Co ions be that of either a distorted tetrahedral or an octahedral structure and the fitting of EXAFS data further shows a Co−O bond coordination number...

Major challenges in the area of wet transportation of radioactive materials are reliability and safety of transportation casks. In most cases, the bottom part of the cask is filled with water whereas a gaseous mixture is contained in the upper part. In such a configuration, water radiolysis leads to the formation of hydrogen and oxygen, which continuously enriches the gaseous mixture. Among the functions to be satisfied, wet transportation systems shall thus allow the control of the hydrogen content below its flammability limit. This is currently achieved by limiting the transportation duration so as to reopen the cask before the critical hydrogen concentration is reached. Development of new technologies that would mitigate the hydrogen risk is all the more motivated because it would allow an extension of the transportation duration. AREVA-TN International and the Institut de recherches sur la catalyse et l'environnement de Lyon have developed a catalytic system which aims at buffering the hydroge...

International audience; The reaction of selective hydrogenation of butadiene performed in an excess of propene, which has been extensively studied over gold supported on different oxides and exhibited high selectivity to butenes, has been applied to the case of gold (1 wt%) supported on zinc oxide (8 m2 g−1), a strongly basic oxide, in order to try to thwart deactivation. Our results revealed, for the first time, a catalytic behaviour drastically different from what was previously observed over gold catalysts supported on alumina or titania, i.e. a much poorer activity when the catalyst was activated under usual conditions under hydrogen but a “normal” activity when it was activated in air. An in-depth characterisation study based on different hypotheses to explain the unusual result revealed that at variance with the other catalysts, Au1Zn1 alloy particles formed during activation under hydrogen at 300 °C and were responsible for the loss of activity.

The heats of adsorption of linear and bridged CO species adsorbed on Ag0 sites of a reduced 3% Ag/Al2O3 catalyst and of the linear CO species on Ag+ sites of the oxidized catalyst are determined as the function of their respective coverages by using the adsorption equilibrium infrared spectroscopy method previously developed. The evolutions of the intensities of the IR bands of each adsorbed species: 2045 cm-1 and 2000 cm-1 at 300 K, for the linear and bridged CO species, respectively, on Ag0 sites of the reduced solid and 2168 cm-1 for a linear CO species on Ag+ sites of the oxidized solid are determined as a function of the adsorption temperature Ta, at a constant CO adsorption pressure PCO. This provides the evolutions of the coverages of each adsorbed CO species with Ta in isobar conditions that give the individual heats of adsorption of the three adsorbed CO species at several coverages according to an adsorption model. The heats of adsorption of the linear and bridged adsorbed CO species on Ag0 sit...

International audience; The heats of adsorption at several coverages of the linear and bridged CO species (denoted L and B, respectively) adsorbed on the Pt0 sites of the 2.9 wt% Pt/10% K/Al2O3 catalyst are determined using the Adsorption Equilibrium Infrared spectroscopy method. The addition of K on 2.9% Pt/Al2O3 modifies significantly the adsorption of CO on the Pt particles: (a) the ratio L/B is decreased from 8.4 to 1, (b) a new adsorbed CO species is detected with an IR band at 1763 cm−1, (c) the heats of adsorption of L and B CO species are significantly altered and the positions of their IR bands are shifted. The heats of adsorption of L CO species are decreased: i.e. 206 and 105 kJ/mol at low coverages on Pt/Al2O3 and Pt/K/Al2O3 respectively. Two B CO species denoted B1 and B2, with different heats of adsorption are observed on Pt/K/Al2O3. The heats of adsorption of B2 CO species (major B CO species) are significantly larger than those measured in the absence of K: i.e. 94 and 160 kJ/mol at low coverages on Pt/Al2O3 and Pt/K/Al2O3 respectively, whereas those of B1 CO species (minor species) are similar: 90 kJ/mol at low coverages. These values are consistent with the qualitative High Resolution Electron Energy Loss Spectrometry literature data on Pt(1 1 1) modified by potassium.

The heats of adsorption of the adsorbed CO species on Ni supported catalysts are rarely studied by using classical analytical methods (i.e. microcalorimetry and temperature programmed desorption (TPD)) due to experimental difficulties linked to different parallel surface reactions to the adsorption/desorption processes. In the present study, the heats of adsorption of the linear and bridged CO species (denoted L and B CO, respectively) on a reduced 20% Ni/Al2O3 catalyst are studied by using the adsorption equilibrium infra red method developed previously. After a stabilization procedure of the catalyst, the evolutions of the IR bands of the L and B CO species: 2053 and 1927 cm−1, respectively, at Ta = 500 K and Pa = 1 kPa, with the adsorption temperature Ta are studied at a constant adsorption pressure Pa. These data provide the evolutions of the coverages θL = f(Ta) and θB = f(Ta) of the two adsorbed CO species with the increase in Ta in isobar conditions. These curves allow us to determine the heats of adsorption E L θ L and E L θ B of the L and B CO species for several values of the coverage θL and θB according to an adsorption model, i.e. EL1 = 100, EL0 = 153, EB1 = 106 and EB0 = 147 kJ/mol at coverages 1 and 0, respectively. These values are consistent with literature data on Ni single crystals. In particular, it is shown that the mathematical formalism of the AEIR method can be applied to literature data on Ni(1 1 1) providing ECOθ values similar to those of the present study showing the limited impact of the Ni particle size on the CO adsorption properties. The presence of hydrogen (2% CO/10% H2/He) during the measurement decreases slightly the coverages of the two CO species at high temperatures due to either a decrease in the heats of adsorption (i.e. EL1 = 97, EL0 = 131, EB1 = 89 and EB0 = 138 kJ/mol) or the perturbation of the adsorption equilibrium by hydrogenation of the adsorbed CO species.

The study concerns modifications of the elementary steps involved in the isothermal oxidation with O2 of linear and bridged CO species adsorbed on a reduced 2.9% Pt/Al2O3 catalyst in the presence of co-adsorbed N-containing species. The rate of the CO2 production at T 350 K : RCO2(t) with time on stream, t, in x% O2/y% Ar/He ( x , y 3 ) presents a decreasing exponential-like profile for a Pt dispersion D 0.26 in the absence of N-containing species. This profile is significantly modified if NO is adsorbed before oxidation of the adsorbed CO species. An induction period is observed, with a characteristic peak defined by the coordinates of its maximum, t m and RCO2 m. This new RCO2(t) profile is unchanged during successive reduction in CO/oxidation in O2 cycles, indicating that the perturbation created by the NO adsorption is permanent at T 350 K . The impact of NO adsorption on RCO2(t) is ascribed to Nads species formed by NO dissociation. Previous studies allow us to show that the modification of the RCO2(t) profile is due to the decreased rate constants of two elementary steps after the adsorption of NO: (a) the desorption of the bridged CO species, which leads to fewer Pt° sites for the activation of oxygen, and (b) the Langmuir–Hinshelwood steps involved in the oxidation of the adsorbed CO species.

The present study concerns the characterization, by experiments in the transient regime, at atmospheric pressure, with either a Fourier transform infrared or a mass spectrometer as a detector, of the elementary steps involved in the isothermal oxidation at TOTO lower than 360 K of the superficial species formed by adsorption of CO on reduced Pt/Al2O3 catalysts: linear, bridged, and threefold coordinated CO species. The coverages of the adsorbed species and the rate of the CO2 production are determined during successive adsorption, desorption, and oxidation reactions for different durations. The evolution of the rate of the CO2 production with the duration of the oxidation, RCO2(t), presents a variety of profiles, depending on the Pt dispersion of the catalysts. For Pt dispersions higher than 0.6, an induction period is observed and the RCO2(t ) profile is characterized by a peak with a maximum defined by tmtm and RCO2m. The greater the Pt dispersion is, the longer tmtm is and the lower RCO2m is. For Pt dispersions lower than 0.6, the RCO2(t ) profile is similar to a decreasing exponential, and its highest value is observed at time 0 of the oxidation. The induction period observed for Pt dispersions higher than 0.6 allows us to characterize the Langmuir–Hinshelwood steps between the adsorbed CO and oxygen species by studying the impacts on tmtm and RCO2m of different experimental parameters such as the Pt dispersion, the oxidation temperature, the oxygen partial pressure, and the duration of a desorption stage before oxidation. A kinetic model based on the oxidation of the L CO species by a weakly adsorbed oxygen species formed on the Pt0 sites liberated by the removal of the bridged CO species provides a set of mathematical expressions that provide a reasonable explanation of the impacts of the various experimental parameters on tmtm and RCO2m. As a consequence, this kinetic model reveals how the Pt dispersion affects the elementary step and the turnover frequency of the CO/O2 reaction. A comparison of the present study with similar literature data on a single Pt crystal shows that the differences in the experimental conditions, material and pressure gaps, may lead to a situation in which the Langmuir–Hinshelwood steps that are studied are not the same.

It has been previously shown that the individual heats of adsorption of each adsorbed CO species (linear, bridged and three-fold coordinated) on Pt/Al 2 O 3 catalysts can be obtained from the change of their characteristic IR bands with the adsorption temperature T a (in the range of 300–800 K) at a constant CO partial pressure P a according to a procedure denoted adsorption equilibrium infrared spectroscopy. In the present study, this procedure is used to reveal the impact of the nature of the support TiO 2 , CeO 2 and Y 2 O 3 /ZrO 2 (two solids with high (104 m 2 /g) and low (14 m 2 /g) BET surface area) on the heat of the adsorption of the L CO species that dominates the CO adsorption. These reducible supports have been selected because of their expected interactions with Pt particles according to different SMSI effects. In the wavenumber range characteristic of the L CO species on Pt sites, the FT-IR spectra are dependent on the nature of the support: two strongly overlapped IR bands are detected with an intensity ratio depending on the support. However, it is shown that the nature of the support only has a slight impact on the average heats of adsorption of the L CO species ( 2 O 3 ).

The impact of Pt dispersion (denoted by D ) of Pt/Al 2 O 3 catalysts on the turnover frequency (TOF) of the CO/O 2 reaction and on the elementary steps involved in the catalytic reaction is studied using transient experiments with either a mass or a FTIR spectrometer as a detector. Similar to literature data, it is observed that TOF decreases with an increase in D . The aim of the present study is to correlate this observation with the modifications of the surface elementary steps of two kinetic models, M1 and M2, developed previously for D ≲ 0.6 . The elementary steps considered are (1) adsorption of CO as a linear CO species (denoted by L and involved in models M1 and M2) and as a bridged CO species (denoted by B); (2) the oxidation by O 2 of the adsorbed CO species; and (3) the reduction by CO of the strongly adsorbed oxygen species (denoted by O sads ) involved in model M2. It is shown that D has no significant impact on the heat of adsorption of the L CO species and on the mechanism of the reduction of O sads species by CO. For oxidation of the L CO species by O 2 , it is shown that there is an induction period in the CO 2 production for D ≳ 0.60 not observed for a lower dispersion. This is explained by considering that the rate of formation of the Pt sites, which adsorb O 2 during oxidation, depends on D . These sites, which represent a small fraction of the Pt 0 sites, are associated with the B CO species. It is shown that the heat of adsorption of the B CO species increases with an increase in D . It is suggested that it is the removal of the B CO species (by desorption and oxidation) that controls the induction duration.

The heats of adsorption of two linear CO species adsorbed on the Au degrees particles (denoted L(Au degrees)) and on the Ti(+delta) sites (denoted L(Ti+delta)) of a 1% Au/TiO(2) catalyst are determined as the function of their respective coverage by using the AEIR procedure (adsorption equilibrium infrared spectroscopy) previously developed. Mainly, the evolutions of the IR band area of each adsorbed species (2184 cm(-1) for L(Ti+delta) and at 2110 cm(-1) for L(Au degrees)) as a function of the adsorption temperature T(a), at a constant CO adsorption pressure P(CO), provide the evolutions of the coverages theta(LTi+delta) and theta(LAu degrees ) of each adsorbed CO species with T(a) in isobar conditions that give the individual heats of adsorption. It is shown that they linearly vary from 74 to 47 kJ/mol for L(Au degrees ) and from 50 to 40 kJ/mol for L(Ti+delta) at coverages 0 and 1, respectively. These values are consistent with literature data on model Au particles and TiO(2). In particular, it is shown that the mathematical formalism supporting the AEIR procedure can be applied to literature data on Au-containing solids (single crystals and model particles).

A new simple analytical procedure is described that allows the determination of the heats of adsorption (denoted Eθ) of adsorbed species at several coverages (θ's) using a single experiment. This procedure is an extension of an original method previously developed (denoted AEIR: adsorption equilibrium infrared spectroscopy). A mass spectrometer is used to determine the amounts of gas (in the present study, CO and H2) either desorbed from or adsorbed on a metal supported catalyst (4.7% Cu/Al2O3 and 2.9% Pt/Al2O3) during the perturbation of the adsorption equilibrium due to a controlled change of the adsorption temperature (Ta) at a quasi-constant adsorption pressure (Pa). These amounts allow us to follow the evolution of the adsorption equilibrium coverage (θe) with Ta at the quasi-constant partial pressure (Pa). Then, the curve θe = f(Ta) provides Eθ = f(θ) with the support of an adsorption model. This procedure presents several advantages as compared to the TPD methods, in particular, considering the th...

The adsorption of CO at several adsorption temperatures (T a ) in the range of 300-550 K on several reduced 5 wt % Cu/Al 2 O 3 solids, with and without residual chlorine, is studied by FTIR spectroscopy. Whatever the solid,the main adsorbed species is a linear (denoted by L) CO species adsorbed on Cu° sites. On the Cl-free solids, the L CO species is detected at 2095 cm - 1 , while the presence of Cl leads to a shift to higher wavenumbers. The evolution of the coverage θ L of the L CO species with the adsorption temperature for a constant CO partial pressure (P C O = 1 kPa) allows us to determine the heat of adsorption of the L CO species as a function of the coverage on the various Cu-containing solids by using the AEIR method. It is shown that the presence of residual Cl has no impact on the heat of adsorption at low coverages (82 kJ/mol), while it decreases slightly the heat of adsorption at high coverages from 57 to 45 kJ/mol.

[EN] Structured hierarchical catalysts were developed for efficient reduction of bromates in water. In the catalysts a small amount of active metal, 0.3 wt.% Pd, is supported onto carbon nanofibres grown either on sintered metal fibres or on a carbon cloth. In both cases high rates of reaction and high selectivity were achieved, allowing a significant reduction in the amount of catalyst required for the treatment of a set volumetric flow of polluted water, compared to a conventional Pd/Al2O3 catalyst. Manufacture of carbon nanofibres grown on a hierarchical structured support was scaled to 10 g batches. Cradle-to-gate life cycle assessment (LCA) study was performed to compare potential water treatment processes based on two catalyst types, and to identify the areas for future optimisation of the novel technology based on structured hierarchical catalysts., The research leading to these results has received funding from the European Community's Seventh Framework Programme [FP7/2007-2013] for MONACAT under Grant agreement no NMP4-SL-2009-226347. We would like to thank Drs Dana Kralisch and Denise Ott for their advice on Umberto LCA methods.

Emerging micropollutants have been recently the target of interest for their potential harmful effects in the environment and their resistance to conventional water treatments. Catalytic ozonation is an advanced oxidation process consisting of the formation of highly reactive radicals from the decomposition of ozone promoted by a catalyst. Nanocarbon materials have been shown to be effective catalysts for this process, either in powder form or grown on the surface of a monolithic structure. In this work, carbon nanofibers grown on the surface of a cordierite honeycomb monolith are tested as catalyst for the ozonation of five selected micropollutants: atrazine (ATZ), bezafibrate, erythromycin, metolachlor, and nonylphenol. The process is tested both in laboratorial and real conditions. Later on, ATZ was selected as a target pollutant to further investigate the role of the catalytic material. It is shown that the inclusion of a catalyst improves the mineralization degree compared to single ozonation.

6 pages, 2 tables., The aim of this work is to study the activity of new Pd catalysts, supported on two different nano structured carbon materials, for bromate catalytic hydrogenation. The influence of the support has been studied, obtaining the best results with a palladium catalyst supported on carbon nanofibers (CNF) grown in sintered metal fibers (SMF). The results have shown the importance of the catalyst support in order to minimize the mass-transfer limitations ensuring an efficient catalyst use. In this way the most active catalysts are those with a mesoporous structure containing high dispersed Pd nanoparticles. The activity of this catalyst for bromate reduction has been tested in different types of water, namely, distilled water, natural water and industrial wastewater. It has been shown that the catalyst activity depends on the water matrix and bromate reduction rate depends on the hydrogen partial pressure. The potential use of the catalyst has been studied in a continuous reactor. It has been observed that the catalyst is active without any important deactivation at least during 100. h of reaction, but is necessary to avoid salt precipitation and plugging problems., The authors thank the European Union (European Community’s Seventh Framework Programme FP7/2007-2013 under Grant Agreement No. 226347 Project) for financial support.

International audience; This paper deals with the study of the conditions of obtention of small metal copper particles on ZnO using easy synthesis methods and activation treatments, which were found "efficient" for the preparation of copper particles on silica, that is, deposition-precipitation with urea and incipient wetness impregnation. For the latter, four different copper precursors were used: copper(II) nitrate, acetylacetonate, bis-ethylenediamine, and tetraamine. Activation treatments were performed under different gas reducing conditions (H2 or CO in N2), temperatures between 280 and 350 °C, and isotherm between 1 min and 2 h, with or without a precalcination step. Transmission electron microscopy (TEM), UV-visible spectroscopy, and X-ray diffraction (XRD) techniques were used to characterize the samples at the different stages of the synthesis route. The TEM results showed that it is not as easy as on silica to make small copper particles on ZnO. However, some experimental conditions were found to lead to particles around 4 nm: impregnation with copper acetylacetonate or copper bis-ethylenediamine, followed by calcination before reduction in H2. The important result of this work is that depending on the final temperature of reduction under hydrogen, it was possible to form either metal Cu particles (280 °C) or Cu3Zn alloy particles (350 °C); this was directly proved by XRD and indirectly by UV-visible spectroscopy. However, the formation of Cu3Zn could be avoided if the reducing gas H2 was replaced by CO in N2. To our knowledge, this is the first time that the formation of Cu3Zn alloy particles is evidenced in Cu/ZnO samples.

A new simple analytical procedure is described that allows the determination of the heats of adsorption (denoted E(theta)) of adsorbed species at several coverages (theta's) using a single experiment. This procedure is an extension of an original method previously developed (denoted AEIR: adsorption equilibrium infrared spectroscopy). A mass spectrometer is used to determine the amounts of gas (in the present study, CO and H2) either desorbed from or adsorbed on a metal supported catalyst (4.7% Cu/Al2O3 and 2.9% Pt/Al2O3) during the perturbation of the adsorption equilibrium due to a controlled change of the adsorption temperature (Ta) at a quasi-constant adsorption pressure (Pa). These amounts allow us to follow the evolution of the adsorption equilibrium coverage (theta(e)) with Ta at the quasi-constant partial pressure (Pa). Then, the curve theta(e) = f(Ta) provides Etheta = f(theta) with the support of an adsorption model. This procedure presents several advantages as compared to the TPD methods, in particular, considering the theoretical supports linked to the exploitation of the experimental data. As compared to AEIR, the TPAE procedure allows one to study the heats of adsorption of adsorbed species that are not detectable by IR. However, it is not adapted if surface reactions occur in parallel to adsorption/desorption processes.