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A key step in creating efficient and long-lasting catalysts is understanding their deactivation mechanism(s). On this basis, the behavior of a series of Pd/corundum materials during several hydrogen adsorption/desorption cycles was studied using temperature-programmed desorption coupled with mass spectrometry and aberration-corrected transmission electron microscopy. The materials, prepared by impregnation and by sputtering, presented uniform well-dispersed Pd nanoparticles. In addition, single atoms and small clusters of Pd were only detected in the materials prepared by impregnation. Upon exposure to hydrogen, the Pd nanoparticles smaller than 2 nm and the single atoms did not present any change, while the larger ones presented a core–shell morphology, where the core was Pd and the shell was PdHx. The results suggest that the long-term activity of the materials prepared by impregnation can be attributed solely to the presence of small clusters and single atoms of Pd.

The oil sands industry generates large volumes of oil sands process water (OSPW). There is an urgent need for OSPW treatment to reduce process water inventories and to support current reclamation approaches. This study discusses how efficient ozone (O

International audience; CoAl‐spinel nanoparticles prepared by liquid‐feed flame spray pyrolysis (L−F FSP) and activated by reduction at different temperatures were used to investigate the hydrogenation process of furfural (FA) under mild conditions. Reduction of the spinel at 500 °C resulted in high FA conversion and selectivity to furfuryl alcohol (FFA, 81 % yield, in 1 hour). Reduction at higher temperatures (i. e., 700 and 850 °C) led to the direct formation of diols (i. e., 1,5‐PeD and 1,2‐PeD) from FA. The differences in activity are attributed to the formation of surface metallic cobalt nanoparticles upon reduction at high temperature. A maximum of 30 % 1,5‐PeD was yielded after 8 hours of reaction under the optimized conditions of150 °C, 30 bar of H2 and with 40 mg of catalyst reduced at 700 °C. This is the first report on the direct catalytic conversion of furfural to1,5‐pentanediol with a non‐noble metal solid catalyst.

International audience; The catalytic properties of ZnAlVO mixed oxides derived from decavanadate-exchanged ZnAl–layered double hydroxide (LDH) precursors prepared by a sol–gel method (ZnAlVO–LDHx,y) were investigated in the oxidative dehydrogenation of propane and compared with those of supported catalysts obtained by conventional impregnation of NH4VO3 on ZnO (ZnVO-I,y) and ZnAlO mixed oxide (ZnAlVO-I,y) supports. The effects of composition and calcination time on the catalytic behavior were particularly examined. Higher propane conversions were achieved at higher vanadium content and calcination time of the precursors. The LDH-derived catalysts were the most active ones in all the temperature range studied (300–425 °C). The order of activity for propane conversion for the different catalyst families varies as ZnAlVO–LDHx,y > ZnAlVO-I > ZnVO-I and follows the strength of the Lewis and Brønsted acid sites determined by monitoring of pyridine adsorption by Fourier transform infrared spectroscopy, whereas the propene selectivities are close together in agreement with the similar densities of basic sites determined by CO2–temperature-programmed desorption measurements. It was indeed established that the acidity, rather than the nature of the crystalline phases, the reducibility, or the specific surface area of the samples, governs the catalytic activity.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are usually suitable candidates for the development of drug delivery devices. Sol-gel chemistry represents an easy method to obtain porous silica nanoparticles. Mesoporous silica nanomaterials have been widely used for drug delivery purposes. In this work we synthesized silica based materials using two molar alkoxide:water ratios 1:4 and 1:8, incorporating paracetamol to develop a nano-sized matrix for controlled release purposes. The samples exhibited different values for surface area, porosity, particle size and distinct punctual defects. Infrared and UV-visible spectroscopic studies were carried out to demonstrate the effect of water concentration and the adequate incorporation of paracetamol molecules. Nitrogen adsorption characterization was realized and the estimated BET surface values were from 532 to 825 m2/g. Kinetic analysis of drug release profiles was performed using the hyperbola model. Transmission electron micrographs showed that all the materials formed aggregates of small particles with size between 10 - 60 nm. Mesoporous SiO2 materials were proved to be a suitable system for controlled release of paracetamol.

Graphene like-TiO2 nanocomposites (rGO-TiO2) are prepared via hydrothermal route by following different synthetic protocols. The as-prepared nanostructured materials exhibit higher photocatalytic activity than bare TiO2 in the treatment of synthetic produced water containing high salinity levels and different compositions of recalcitrant dissolved organic matter. The effect of the preparation method on the physico-chemical properties is assessed by performing a wide characterization combining different analyses, such as nitrogen physic-adsorption (BET), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), UV-VIS Diffuse Reflectance Spectroscopy (DRUV) and Electron Paramagnetic Resonance (EPR). The effect of several operative variables (i.e., TiO2/rGO weight ratios, and addition of hydrogen peroxide) on the photocatalytic activity is also critically evaluated. The highest photocatalytic activity is obtained for a rGO/TiO2 weight ratio of about 10%, for which a good compromise between uniformity of dispersion of the TiO2 particles on the rGO layers and covering degree of the titania photoactive surface is achieved. This study can contribute to open new perspectives in the design of high performance graphene like-based TiO2 photocatalysts for removing hydrophobic bio-recalcitrant pollutants from saline water.

10.1016/j.clay.2014.02.012 Improving the adsorption of long-term radioactive species in the underground disposal of waste waters from nuclear reactors is a key issue. The natural metal oxides or hydroxides underground have the low retention ability of anionic species. Here, calcined Mg/Al LDHs were used as adsorbents. The influence on the adsorption capacity of different intercalated guest anions (carbonate (CO32 -) and nitrate (NO3-)) in the parent LDH was investigated, along with the effect of ultrasonication. Two Mg/Al molar ratios (3/1 and 2/1) were compared. Adsorption capacity was strongly affected by material textural properties, and the carbonate LDH-derived mixed oxides showed the largest adsorption capacity. Mixed oxides with an Mg/Al molar ratio equal to 3 presented higher iodide adsorption due to their lower charge density. The adsorption assisted by ultrasound increased iodide removal efficiency by reducing internal diffusion limitation. Two models were used to determine adsorption capacity: Langmuir and Freundlich. The iodide adsorption was best fitted by the Langmuir equilibrium model.

URL: https://www-sciencedirect-com.sabidi.urv.cat/science/article/pii/S0025540817325722?via%3Dihub DOI: 10.1016/j.materresbull.2017.08.029 Filiació URV: SI In this study, two different preparation methods of titanium dioxide nanoparticles/reduced graphene oxide nanocomposites were investigated using direct sol-gel method followed by hydrothermal treatment or simple hydrothermal route. A different amount of graphene (1- 20%) was mixed with TiO2 for both series of samples in order to improve the photocatalytic activity. The influence of the preparation method on the physico-chemical properties was established by different characterization methods and the photocatalytic degradation of methylene blue (MB) under UV light irradiation was used as test reaction. The highest photocatalytic activity was observed for the nanocomposites containing 10 wt% of graphene. The elimination of MB can reach 93% and 82% for the nanocomposites with 10 wt% graphene prepared by the sol-gel and hydrothermal methods, respectively. These photocatalysts are promising for practical application in nanotechnology.

DOI: 10.1016/j.apsusc.2016.11.037 URL: http://www.sciencedirect.com/science/article/pii/S0169433216323959 Filiació URV: SI Inclòs a la memòria: SI Layered double hydroxides (LDH or HT) or their derived mixed oxides present marked acid-base properties useful in catalysis, but they lead to agglomerate inducing a weak accessibility to the active sites. In this study we report the preparation and characterization of HT/Graphene (HT/rGO) nanocomposites as active and selective basic catalysts for the acetone condensation reaction. The graphene high specific surface area and structural compatibility with the HT allowed increasing the number and accessibility of the active sites and activity of this later. Two series of HT/rGO nanocomposites with 0.5 ≤ HT/rGO ≤ 10 mass ratio were prepared by: i) direct HT coprecipitation in the presence of GO; ii) self-assembly of preformed HT with GO. The prepared HT/rGO nanocomposites were dried either in air at 80 °C or freeze-dried. A series of characterizations showed the great influence of the preparation method and HT/rGO mass ratio on both the nanocomposite structure and catalytic activity. An optimum activity was observed for a HT/rGO = 10 catalyst. Particularly, the highest catalytic activity was found in those nanocomposites obtained by coprecipitation and freeze dried (3 times more active than bulk HT) which can be connected to their structure with a better accessibility to the basic sites.

The catalytic properties of Co-Al spinel nanoparticles prepared by liquid-feed flame spray pyrolysis (L-F FSP) were investigated in the glycerol conversion in gas phase in an atmosphere of hydrogen. Reduction at 1123¿K of the as-synthesized spinel nanoparticles induced the formation a new phase containing metallic cobalt species. Although, the reducibility of cobalt oxides is greatly decreased due to interaction with aluminium species, this strong interaction may prevent the aggregation of Co particles under the harsh reduction conditions. X-ray photoelectron spectroscopy (XPS) of the reduced spinel nanoparticles at 1123¿K revealed that the Co/Al atomic ratio has decreased to Co/Al¿=¿0.11, which may indicate a redistribution of the aluminum and cobalt species at the surface of the sample submitted to the reduction in a flow of hydrogen at 1123¿K. X-ray diffraction (XRD) and high resolution electron microscopy (HRTEM) also reinforced the formation of metallic cobalt species after reduction of cobalt from the spinel nanoparticles at 1123¿K. The main products obtained from the conversion of glycerol in the gas phase were hydroxyacetone, pyruvaldehyde, lactic acid and lactide. FSP ensured uniform dispersion of the active metal on a support material.

Glycerol carbonate and glycerol dicarbonate were synthesised as glycerol value-added products via a transesterification reaction using diethyl carbonate as co-substrate. This green, efficient and selective process involved catalysis with different hydrotalcite-like compounds containing a Mg/Al molar ratio between 2 and 4 that were activated by calcination, by calcination followed by rehydration under ultrasound or by anion exchange (F−, Cl−, CO32 −). The correlation between the basic properties of the solid catalysts and the activity in the glycolysis reaction was investigated. The catalytic activity shown by the different activated Mg/Al solids was proportional to the surface density of basic sites (number of medium and strong-strength basic sites presented in the catalyst per square meter). The highest activity was found for the rehydrated hydrotalcite catalysts, which showed basic Bronsted sites and which can be reused several times without significant loss of activity. Tuning the basic properties of hydrotalcites by means of changing the nature of the anion also offered interesting changes in the catalytic performance.

BIOVERT+FFI; MgAl hydrotalcites have been grown onto alpha- and gamma-Al2O3 and characterized by XR diffraction, N-2 and CO2 adsorption. XRD patterns show the crystallization of hydrotalcites as nanometric crystals. On the calcined supported materials, the thermal desorption of CO2 evidences the presence of relatively strong basic sites which are absent on the pure supports. The samples supported by alpha-Al2O3 exhibit a higher basic strength than those supported on gamma-Al2O3. After rehydration, the total number of sites changes only little, but the original sites, presumed to be of Lewis type are converted to stronger Bronsted sites. The synthesis of glycerol carbonate and dicarbonate has been performed by transesterification of glycerol by diethyl carbonate in a green, efficient and selective process catalyzed by these hydrotalcites supported on alpha- and gamma-Al2O3. The control of grain size of the support allows to operate in a flow reactor, then to evaluate the extent of deactivation as a function of time on stream at full conversion of glycerol. Stable catalysts are obtained when a-Al2O3 is the support. (C) 2011 Elsevier B.V. All rights reserved.

The increase in bio-diesel production is generating high quantities of glycerol as by-product. Glycerol carbonate and its esters are key multifunctional compounds employed as chemical intermediates, monomers, solvents, additives and fuel contents. In this study, glycerol carbonate and glycerol dicarbonate were synthesized as glycerol value-added products via a transesterification reaction using diethyl carbonate as co-substrate. This green, efficient and selective process involved catalysis with different hydrotalcite-like compounds containing a Mg/Al molar ratio of 4 that were activated by calcination and by calcination followed by rehydratation under ultrasound. The correlation between the basic properties of the solid catalysts and the activity in the glycolysis reaction was investigated. The catalytic activity shown by the different activated Mg/Al solids was not proportional to the number of basic sites present in the catalyst. The highest activity was found for the rehydrated hydrotalcite catalyst, which showed basic Bronsted sites and which can be reused several times without significant loss of activity.

Aluminum was incorporated into SBA-15 supports at molar ratios Si/Al = 10 and 2 by the pH-adjusting method. The calcined mesoporous Al-SBA-15 supports, as well as the Al-free SBA-15 support, were impregnated with ammonium paratungstate ((NH4)(10)center dot[H2W12O42]center dot 4H(2)O) aqueous solution. Tungsten carbide (W2C) was synthesized by temperature programmed carburization (TPC) from the. WO3 supported on AI-SBA-15 and SBA-15 in a flow of CH4/H-2. These resultant materials were characterized by powder X-ray diffraction (XRD), N-2 adsorption/desorption, Al-27 NMR and Raman spectroscopies, and transmission electron microscopies (TEM and HRTEM). W2C species were obtained after the carburization process in all the materials. The mesoporous structure of the SBA-15 supports was preserved at all synthesis steps. XRD and TEM analyses revealed that the introduction of aluminum species into the SBA-15 greatly enhanced the dispersion of WO3 and W2C phases during the calcination and carburization steps, respectively. In situ XRD measured during the carburization in a synchrotron facility provided further details of the reduction of tungsten trioxide species as a function of temperature. The presence of aluminum in the SBA-15 notably affected the distribution and the reduction temperature of the tungsten oxide species. (C) 2015 Elsevier Inc. All rights reserved.

We explored the use of selected layered double hydroxides (LDHs) of different compositions and obtained by means of different routes (i.e., coprecipitation, anionic exchange and reconstruction) as iodine/iodate adsorbents. The influence of speciation (iodide vs. iodate) on iodine uptake was rather strong, resulting in much lower iodide incorporation. The Fourier transform of iodine K X-ray absorption edge data (EXAFS) of all iodate-LDHs showed a single I–O scattering path of 1.8 A ° . Thermal stability and leaching experiments showed that the incorporated iodate and iodide were rather loosely bound in the interlayer space and were easily released under heating to 180 C and leaching with Milli-Q water and brine solution.

Catalytic wet air oxidation using heterogeneous catalysts is a promising technology for treatment of wastewaters. Wastewaters from olive oil mills are difficult to clean because effluents contain high levels of phenolic compounds that cannot be removed by biological treatment or incineration. Therefore, we tested the catalytic wet air oxidation of p-hydroxybenzoic acid, as model molecule of olive oil mills wastewaters, over Ru-supported CeO2–TiO2 mixed oxides. We focussed on the Ce/Ti molar ratio because this ratio modifies the properties of the Ru catalysts. Supports were prepared by using the sol–gel method. The Ru catalysts were prepared by impregnation. Those products were characterized by N2 adsorption–desorption, X-ray diffraction, H2 chemisorption, transmission electron microscopy and inductively coupled plasma. Catalytic wet air oxidation of p-hydroxybenzoic acid was performed in a batch reactor at 140 °C and 50 bar of air. Our results show that the most efficient catalyst was Ru with a Ce/Ti ratio of 1/5, which converted totally p-hydroxybenzoic after 7 h of reaction without Ru leaching. We explain this finding by an enhanced dispersion of Ru due to better structural properties of the CeO2–TiO2 support.© 2015, Springer International Publishing Switzerland.

Hydrotalcite (HT) nanolayers have been grown directly on carbon fibers by carbonization and subsequent hydration of electrospun PVA/PEO/MgAl-nitrate fibers. The growth of the layered material was ascertained by X-ray diffraction and electron microscopy techniques. High resolution transmission electron microscopy indicated that HTs are adhered on the carbon fibers. The HTs presented very small crystallite sizes, which enhance the accessibility of their basic centers compared to bulk HTs, leading to significant differences in terms of catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.

International audience; Reconstruction of mixed oxides resulting from the thermal decomposition at 723 K of ZnAl and ZnMgAl layered double hydroxides (LDHs) has been studied performing mechanical stirring or ultrasonic treatments for different periods of time in aqueous media. Thesematerialswere fully characterized by several physico-chemicalmethods including powder X-Ray diffraction and Rietveld refinements, XANES and XASF spectroscopies. The results show that the crystallinity increases in the LDH samples after the reconstruction. The crystallite sizes of the reconstructed LDHs increase in comparison to the as-prepared LDHs and this effect is improved upon ultrasound treatments. Moreover, reconstructed samples did not completely recover the original structure and ZnO phase was formed at the expense of an amorphous phase present in the as-prepared LDH. The application of ultrasound favors the formation of ZnO. Incorporation ofMg as ternary cation to obtain Mg/Zn/Al LDH decreases the crystallinity and leads to more disordered materials. The Mg/Zn/Al LDHs present lower amount of amorphous phase than ZnAl LDHs which also decreases in the reconstructed samples. But, in contrast to the behavior observed for Zn/Al, ultrasonication alters the crystallinity and increase of the amount of amorphous phasewhen sonication timeincreases. The basicity (number, strength and nature of sites) increases after reconstruction of themixed oxides into the LDH structures as well as with the sonication time; while the opposite trend was observed for the acid sites. Moreover the basicity is greatly enhanced upon introduction ofMg in the LDH. The changes in the population of acid-base sites affect the behavior of the catalysts in the carbonylation of glycerol.

9 p., 11 figures, 2 tables and references., Novel nanostructured TiO 2 and SiO 2 based biocatalysts, with 3-4 wt. % of Pt have been developed. The obtained materials exhibit a high surface area together with a broad pore size distribution. The method of synthesis allowed obtaining high dispersed platinum metal nanoparticles. In vitro DNA reactivity test of the biocatalysts were carried out by electrophoresis and formation of DNA adducts was observed. The most active biocatalyst was H 2PtCl 6/SiO 2. These biocatalysts were also tested in an experimental model of C6 brain tumours in Wistar rats. Administration of the material was made by stereotactic brain surgery to place it directly in the malignant tissue. A significant decrease in tumour size and weight as well as morphologic changes in cancer cells were observed., Authors want to thank to FONCICYT-CONACyT-México Project 95095, INNN and UAM for financial support.

Different Advanced Oxidation Processes (AOPs) such as photocatalysis, Fenton-based processes and ozonation were studied to include one of these technologies within an integrated solution for produced water (PW) polishing. Synthetic PW was prepared adding toluene, xylene, naphthalene, phenol, acetic and malonic acids to a seawater matrix. Despite that in all AOPs studied in this work BTEX and naphthalene were removed, the efficiency (in terms of TOC removal) of each treatment varied largely. Among these techniques, photocatalysis was found to be the less effective for the treatment of PW, as TOC removals lower than 20% were obtained for the best scenario after 4 h treatment. In the contrary, best results were obtained by ozonation combined with H2O2, where all the organic components were removed, including a high percentage of acetic acid, which was not abated by the rest of the AOPs studied. The optimum conditions for ozonation were 4 g h−1 O3 and 1500 mg L−1 H2O2 at pH 10, where after 2 h a 74% of TOC removal was achieved and the acetic acid elimination was 78%. This condition enabled that ozonation process accounted for the lowest electric energy consumption per order of target compound destruction regarding total organic carbon (TOC).

To undertake a better water management in Oil&Gas sector, it is essential to decrease the wastewater generation by increasing the current reused water rates. Focused on this motivation, this study presents the performances of solar-assisted photo-Fenton and heterogeneous photo-catalysis on refinery wastewater treatment for reuse purposes with the aim of zero discharge. While initial tests were made on synthetic refinery wastewater, real case studies were performed with two types of refinery effluent in order to test the feasibility of using AOPs either as a secondary or tertiary treatment. Even though heterogeneous photo-catalysis and a combined process showed promising results for the treatment of the refinery effluents, photo-Fenton treatment revealed a superior effectiveness for application in both secondary and tertiary treatment, considering the improvements on TOC removal, toxicity and biodegradability. Photo-Fenton as secondary treatment resulted as efficient as the biological treatment, reaching final TOC values ca. 20 mg/L and 88% of COD removal presenting values lower than those achieved after the biological treatment. Moreover, a marked increase in the BOD5/COD ratio from 0.38 to 0.83 was obtained. Furthermore, as a tertiary treatment, photo-Fenton process either with H2O2/COD = 10 and H2O2/Fe2+ = 50 or H2O2/COD = 4 and H2O2/Fe2+ = 10 provided a final TOC value

This paper is built on the Fenton-like oxidation of p-hydroxybenzoic acid (p–HBZ) in the presence of H2O2 and 3%Fe supported on CeO2-TiO2 aerogels under mild conditions. These catalysts were deeply characterized by X-ray diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The effect of thermal treatment, pH (2–3, 5, 7), H2O2/p–HBZ molar ratio (5, 15, 20, 25) and reaction temperature (25 °C, 40 °C and 60 °C) on the catalytic properties of supported Fe catalysts are studied. Our results highlight the role of CeO2 and the calcination of the catalyst to obtain the highest catalytic properties after 10 min: 73% of p–HBZ conversion and 52% of total organic carbon (TOC) abatement.