In this work, the influence of the porous structure of the catalyst, as well as the effect of La doping on the performance of Ni-ceria-based catalysts for the reverse water-gas shift reaction (rWGS) has been studied. Thus, Ni-ceria and Ni-La doped ceria catalysts have been prepared using nanocasting or hard-templating method, also studying the influence of the incorporation method of the nickel phase. Samples prepared by sol-gel were also prepared for comparison. The catalysts were tested in the rWGS and characterized by different techniques: X-ray diffraction (XRD), electron microscopy (TEM and STEM-EDX), adsorption-desorption N2 isotherms (BET), temperature programmed reduction (TPR-H2), and X-ray photoelectron spectroscopy. The results obtained indicate that the mesoporous catalysts prepared by hard-templating, regardless of the nickel incorporation method have developed a mesoporous structure and a relatively large specific surface area that increases CO formation per catalyst weight, compared to those prepared by sol-gel. The method of incorporating Ni into mesoporous catalysts influences the level of catalyst deactivation and the evolution of CO selectivity with reaction time.

K10 montmorillonite (K10), zirconia (ZrO2), ZrO2 modified with K10 (K10/ZrO2), and K10 modified with ZrO2 (ZrO2/K10) were used as heterogeneous catalysts in the dehydration of ethanol. This process is of major significance in green chemistry for obtaining value-added products. The K10-ZrO2 materials were synthesized by a pathway using a sol-gel method, introducing particles of K10 or ZrO2 over ZrO2 or K10, respectively. While ZrO2 synthesized presents monoclinic/tetragonal crystalline phases and absence of porous structure, the inclusion of K10 particles into the ZrO2 bulk generated the stabilization of the tetragonal phase and create a micro/mesoporous structured material, whilst the incorporation of ZrO2 in K10 did not show considerable change in the laminar-mesoporous structure and surface area of K10. Furthermore, K10-based catalyst exhibit activity in ethanol dehydration, at relatively mild conditions, for producing either ethylene or diethyl ether (80 %, 40 %, and 30 %, respectively), while minor alcohol conversion rates were observed using K10-ZrO2-based materials (>30 %, >5 %, and >20 %, respectively). The catalyst activity was related to the quantity of acid sites, where the K10 (1.22 meq/g, 80 %) and ZrO2/K10 (2.2 meq/g, 25 %) shows the highest acidity and conversion, as well as to the structural and physicochemical properties. In this preliminary report the application of a novel material is highlighted, where K10 is used as a stabilizer of crystalline phases and porosity properties in ZrO2.

In this work, key factors that affect catalytic activity of Ni/La-doped ceria catalysts for the reverse water gas shift reaction (RWGS) have been revealed by applying in situ advanced synchrotron techniques, such as X-ray Absorption Spectroscopy (XAS) and Near-ambient pressure X-ray Photoelectron spectroscopy (NAP-XPS). Complementary ex situ characterization techniques have been also used, adding valuable insights on different physicochemical properties of the catalysts. Lanthanum incorporates into the ceria lattice, increasing oxygen mobility, which has a role in the formation of H2O during the reaction. The optimum substitution degree of Ce by La that maximizes CO yield is close to 10 %. It is found that both bulk and surface Ce3+ proportions depend on the proportion of La, increasing with La content. At a reaction temperature of 873 K, bulk Ce3+ proportions are higher than surface ones. These differences are due to oxidative phenomena, associated to the reactive mixture that take place on the surface, such as CO2 adsorption and H2O formation. Concerning Ni phase, NiO bulk reduction to metallic Ni is very fast (in the range 573-623 K), however, Ni0 and Ni2+ species coexist on the surface during the reaction. It is found that a higher proportion of surface metallic Ni promotes the selectivity towards the RWGS, inhibiting the competing methanation reaction. On the other hand, La doping is relevant for the formation of lanthanum oxycarbonate, which has a role gasifying carbon deposits.

This research aimed to contribute to the pollution remediation by investing an agricultural food residue developed from Algerian melon (Cucumis melo) fruit peels into novel efficient low-cost biosorbent (AML). Ni(II) metal was selected for the batch biosorption by the AML solid, from aqua system. The impact of different parameters was performed including shaking time, biomass dosage, pH, temperature, and Ni(II) concentration. Interestingly, the biosorption process achieved equilibrium within only 180 min. The kinetic obeyed the pseudo-second order model with high correlation coefficient (0.999). The intraparticle diffusion approach gave R2 equals to 0.829 and 0.75. The Ni(II) uptake was strongly dependent on the dosage increment, attaining 88.8

The KSF-clay is a material that presents a high density of acidic active sites, ideal for being a heterogeneous acid catalyst with outstanding activity. For this study, KSF-clay was characterized by X-ray photoelectron spectroscopy and temperature-programmed desorption of ammonia. Additionally, studies of the adsorption of ethanol, propan-2-ol, and acetic acid molecules over KSF-clay surface to establish their thermal stability species were studied by diffuse reflectance infrared Fourier transform spectroscopy. The relationship between the properties of KSF-clay and the adsorption-interaction process with organic molecules is related to its performance as an acid catalyst.

The modification of montmorillonite with metallic species affects directly its crystalline structure, texture, porosity, and surface. The interaction of the metallic molecules with the clay matrix, derived from the modification pathway and the characteristics of the adsorbate, modifies the physicochemical properties of montmorillonite, enabling the creation of materials with varied characteristics to be used both as catalysts and adsorbents. Small amounts of metallic species can confer various structural and physicochemical characteristics on the same montmorillonite matrix, depending on the metal incorporated. The objective of the present study was to create an acid-base catalyst based on montmorillonite K10 (K10 Mnt), modified with Ti, Ce, and Ni, for the catalytic esterification of acetic acid and penta-1-ol. K10-Mnt was modified using particles of Ti and of Ti modified with Ce and Ni. The effect of the inclusion of Ti and modified Ti species on the transformation of the physicochemical properties of the K10 Mnt and their contributions to the catalytic esterification syntheses were investigated. Samples were characterized by scanning electron microscopy coupled to an energy-dispersive X-ray spectroscopy system (SEM-EDS), powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), physisorption of N-2 at 77 K (BET and BJH), and thermogravimetric analysis (TGA-DTGA). Finally, the original and modified K10 Mnt samples were tested for their catalytic esterification of acetic acid and penta-1-ol in the liquid phase.

The design of an active, effective, and economically viable catalyst for CO2 conversion into value-added products is crucial in the fight against global warming and energy demand. We have developed very efficient catalysts for reverse water-gas shift (rWGS) reaction. Specific conditions of the synthesis by combustion allow the obtention of macroporous materials based on nanosized Ni particles supported on a mixed oxide of high purity and crystallinity. Here, we show that Ni/La-doped CeO2 catalysts-with the "right" Ni and La proportions-have an unprecedented catalytic performance per unit mass of catalyst for the rWGS reaction as the first step toward CO2 valorization. Correlations between physicochemical properties and catalytic activity, obtained using a combination of different techniques such as X-ray and neutron powder diffraction, Raman spectroscopy, in situ near ambient pressure X-ray photoelectron spectroscopy, electron microscopy, and catalytic testing, point out to optimum values for the Ni loading and the La proportion. Density functional theory calculations of elementary steps of the reaction on model Ni/ ceria catalysts aid toward the microscopic understanding of the nature of the active sites. This finding offers a fundamental basis for developing economical catalysts that can be effectively used for CO2 reduction with hydrogen. A catalyst based on Ni0.07/ (Ce0.9La0.1Ox)0.93 shows a CO production of 58 x 10-5 molCO center dot gcat-1 center dot s-1 (700 degrees C, H2/CO2 = 2; selectivity to CO > 99.5), being stable for 100 h under continuous reaction.

The KSF-clay is a montmorillonite-based solid this is widely used as catalyst, shows a great catalytic activity during the esterification reactions . The present investigation aims are to understand with more detail the physicochemical properties of KSF-clay as a catalyst in the esterification in the liquid-liquid phase to obtain pentyl acetate of the reaction of penta-1-ol and acetic acid. KSF-clay was characterized by scanning-electron microscopy integrated to an energy-dispersive X-ray spectroscopy system device (SEM-EDS), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of ammonia (NH3-TPD), and propan-2-ol decomposition test reaction. Additionally, studies of the adsorption of ethanol, propan-2-ol, and acetic acid molecules over KSF-clay surface to establish their thermal stability species, were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) are presents. The effect of the surface and physicochemical properties and their implication in the catalytic performance and deactivation process was discussing.

Abstract The modification of clays including montmorillonites, is a common procedure that gives to the resulting material additional properties compared to the pristine clay. One of these procedures is the modification of the surface/matrix of the clay with inorganic species, to enhance their catalytic and adsorptive properties. In the present study, montmorillonite-clay K10 modified with particles of Ti species and Ti additionally modified with Ce and Ni species, were characterized by X-ray diffraction of powders (XRD), Fourier transform infrared spectroscopy (FTIR), physisorption of N2 at 77K (BET and BJH), and thermal analysis (TA). Finally, clays were tested in the esterification of acetic acid and penta-1-ol in the liquid-phase. The effect of the inclusion of Ti species and the modified of Ti with Ce and Ni species was discussed in terms of the transformation of the nanostructure of the modified clay, and their contribution to the catalytic esterification performance.

Phenol removal as organic pollutant model has been studied on new composite adsorbents prepared from carbon and natural diatomaceous silica mixtures in different proportions (KCp1, KCp2, and KCp3 with 10, 20, and 30% of carbonaceous matter, respectively). SEM observations clearly showed the porous aspect evolution when mixing carbon with the macroporous diatomite skeleton, further proved by TEM images that revealed a co-existence of two distinct pore sizes. FTIR and XRD characterization mainly demonstrated the disappearance of calcium carbonate species as consequence of the undertaken treatments in presence of carbon. N-2 sorption analysis at 77 K confirmed the obtaining of more developed textural properties with enhanced BET surfaces, and the creation of narrower porosity. The best area was obtained for KCp3 (336 m(2)/g) as compared to the starting carbon and diatomite surfaces (118 and 8 m(2)/g, respectively). The influence of several parameters such as contact time, temperature, pH, and initial concentration on the performance of the resultant materials in terms of phenol adsorption was investigated. The pH <= 8 favored the phenol removal, whereas the temperature did not have a great impact in the selected range (30-60 degrees C). The sorption isotherms followed well the Freundlich and, more accurately, Langmuir models with the highest adsorption capacity recorded for KCp3 (98.5 mg.g(-1)). A fast kinetic was revealed whose data best fitted with the pseudo-second-order model with a correlation factors values of R2=0.996, 0.999, and 0.992 for KCp1, KCp2, and KCp3 respectively. More than 50% of the maximum adsorption ratio was achieved in half the time needed for saturation. The new composites offer promising prospects as inexpensive sorbents for use with competitive capacities in the industrial water treatment.

In this study, commercial carbon nanofibers with different graphitic structure and commercial multiwall carbon nanotubes (CNT) were used. Palladium catalysts were prepared using these supports. Subsequently, they were tested in the hydrodechloration reaction of 2,4-dichlorophenoxyacetic acid under ambient-like conditions. Thermogravimetric analyses (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and nitrogen adsorption at 77 K techniques were applied to characterize the different materials. The results have demonstrated the efficiency of a bifunctional material in an integrated process that synergically combines physical adsorption and catalytic degradation. During the process, the carbon surface provides active sites to get chlorophenoxyacetic adsorbed. After saturation of the nanocarbon, the compound was decomposed by the catalytic function of supported Palladium catalysts. The study is focused on analyzing the effects of the support surfaces and electronic state of supported palladium nanoparticles on the catalytic performances. High selectivity to dechlorinated product was obtained with the catalysts prepared over more graphitic supports, whereas no-selectivity to dechlorinated products took place over oxygen-containing support. The mechanistic aspects of this bifunctional process were postulated based on the characterisation of these catalytic materials.

Highly efficient photoactive antimicrobial coatings were obtained using zinc oxide-reduced graphene oxide nanocomposites (ZnO-rGO). Their remarkable antibacterial activity and high stability demonstrated their potential use for photoactive biocide surfaces. The ZnO-rGO nanocomposites were prepared by the sol-gel technique to create photocatalytic surfaces by spin-coating. The coatings were deeply characterised and several tests were performed to assess the antibacterial mechanisms. rGO was homogeneously distributed as thin sheets decorated with ZnO nanoparticles. The surface roughness and the hydrophobicity increased with the incorporation of graphene. The ZnO-rGO coatings exhibited high activity against the Gram-positive bacteriumStaphylococcus aureus. The 1 wt% rGO coated surfaces showed the highest antibacterial effect in only a few minutes of illumination with up to 5-log reduction in colony forming units, which remained essentially free of bacterial colonization and biofilm formation. We demonstrated that these coatings impaired the bacterial cells due to cell membrane damage and intracellular oxidative stress produced by the photogenerated reactive-oxygen species (ROS). The enhancement of the ZnO photocatalytic performance upon rGO incorporation is due to the increased detected generation of hydroxyl radicals, attributed to the reduction of electron-hole pair recombination. This intimate contact between both components also conveyed stability against zinc leaching and improved the coating adhesion.

Novel composite photo-catalysts having (NH4)(4)[NiMo6O24H6]center dot 5H(2)O Polyoxometalate (POM) species deposited over g-C3N4 are synthesized. Materials were characterized through a multitechnique approach showing the stability of the carbon nitride component both through the synthesis process and under reaction. Contrarily, the POM component evolves under reaction conditions to maximize the interaction with the support. Such a behavior renders, as measured by the quantum efficiency, highly active photo-catalysts in the photo-oxidation of 2-propanol and styrene both under UV and sunlight illumination, setting up the basis for a green catalytic process. The material having a 4 wt. % POM showed improved activity with respect to both parent constituents but also higher selectivity to the partial oxidation of the alcohol and the aromatic hydrocarbon to generate added value chemical compounds. A multitechnique approach investigating charge carrier fate demonstrates the key role played by the interaction between components to promote activity and selectivity in selective oxidation reactions.

The effect of the ZnO morphology on the properties of Pd–Au bimetallic catalysts has been discussed.

Trabajo presentado en la XXXIV Reunion Bienal de la Real Sociedad Espanola de Quimica, celebrada en Santander (Espana) del 15 al 18 de septiembre de 2013.

Background: Ruthenium catalysts supported over various carbon materials differing in the nanostructure, grade of graphitization and surface area values have been synthesized and used in the hydrogenation of levulinic acid (LA), biomass platform molecule, in aqueous media. Methods: The prepared Ru catalysts were characterized by temperature programmed reduction (TPR), transmission electron microscopy (TEM) and CO chemisorption coupled with microcalorimetry. The reduced catalysts were studied in a batch reactor and in continuous-flow reactors at 100ºC under 40-50 bar hydrogen pressure for the hydrogenation of LA. Results: A linear correlation between turnover frequency (TOF) for LA conversion and Ru particle size was found in the 1.2-2.9 nm range. TOF increasing with the decreasing Ru particle size, which suggests hydrogenation of LA is a structure-sensitive reaction on Ru nanoparticles. Reduced graphite oxide (rGO) supported Ru catalyst with the lowest metal particle size (1.2 nm) also showed high activity at ambient temperature. Remarkably, this catalyst also displayed high stability in a continuous-flow reactor at 40 bar hydrogen and 100ºC. Conclusion: The improved catalytic performance (activity, selectivity and stability) of the carbon supported Ru catalyst (Ru/rGO-700 sample) for the LA hydrogenation reaction is attributed to the low metal particle size (1.2 nm) obtained over the high surface area and non-acidic rGO-750 carbon support. Keywords: Ru catalyst, carbon support, levulinic acid hydrogenation, structure-sensitive reaction, batch reactor, packed bed reactor.

Au nanoparticles of different sizes were supported by the deposition-precipitation method on two metal oxides: ZnO and TiO2. The resulting catalysts were tested in the ethanol catalytic transformation reaction. Both metal oxide support materials exerted a different influence on the achieved Au particle size as well as on the behavior of the subsequent catalyst, with regard to their initial conversion values, product distribution and stability. While TiO2 favors the formation of smaller nanoparticles, ZnO offers larger Au particle sizes when prepared under similar conditions. At the same time, TiO2 produced catalysts which displayed higher initial conversions in comparison with AuZnO catalysts, even when observing catalysts of each series with similar particle sizes. At the same time, catalysts supported on ZnO exhibited higher resistance to deactivation caused by coke formation. These results were evidenced employing different characterization techniques on both used and fresh catalyst samples. The decline in deactivation was generally accompanied by an increase in the carbon content on the catalyst's surface.

The effect of alkali promotion (Li, Na, K and Cs) on the CO preferential oxidation (CO PROX) reaction has been studied over Cu-CeO2 catalyst supported on carbon nanotubes (CNT). The catalysts were prepared with 2.5 wt.% Cu and 20 wt.% CeO2 loadings, and alkali/Cu atomic ratios of 0.68. The catalytic performance and the characterization by powder X-ray diffraction (XRD), TEM-STEM, H2-temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) has been presented. TEM and XRD analyses showed that the addition of alkali reduces the size of ceria crystallites. It was found that in general the incorporation of alkali favored the conversion of CO at low temperatures, being more pronounced for the K-doped catalyst. The characterization showed that the addition of K favored the Cu-CeO2 interaction, the activity of the catalyst was enhanced and the opposite was observed for Cs-doped sample. The characterization results reveal that the observed increase in the Cu+ species proportion and in lattice oxygen are related to the better catalytic performance.

This work reports on the design of novel mixed valence hybrid N-doped carbon nanotubes/metal ferrite nanomaterials (MFe2O4, M(ii) = Mn, Fe, Co) with tailored composition, and magnetic and electrical properties through a straightforward eco-sustainable and less time consuming one-pot in situ coprecipitation process. The potentialities of this strategy rely on the lack of oxidative treatments to the support and thermal annealing, besides the use of aqueous conditions, a chelating base (isopropanolamine) and low temperatures. The process afforded the controlled nucleation/growth of the MFe2O4 nanoparticles (NPs), with sizes of 3.2-5.4 nm and superparamagnetic properties, on the surface of the N-doped carbon nanotubes (CNT-N) and their immobilization by covalent bonding. The nitrogen-based functionalities of CNT-N allied with the use of a coprecipitation agent with coordinating properties towards M(ii)/Fe(iii) cations were responsible for these achievements. To unravel the potentialities of the novel nanohybrids (CNT-N@M), they were tested as electrode active nanomaterials in the fabrication of all-solid-state asymmetric paper supercapacitors (SCs). All asymmetric SCs presented significantly higher performance than the symmetric CNT-N based one, with an enhancement of the energy density to up to 6.0× and of the power density to up to 4.3× due to the occurrence of both non-faradaic and faradaic charge storage mechanisms. Moreover, they led to enhanced volumetric energy density (up to 11.1×) and power density (up to 5.2×) compared with other solid-state hybrid paper SCs based on carbon materials recently reported in the literature. These results highlight the importance of conjugating a conductive support bearing N-based functionalities with MFe2O4 NPs featuring redox properties towards synergistically enhanced energy storage.

A series of carbon supported polyoxometalates have been prepared and studied as acid catalysts for the fructose dehydration. The catalytic supports, microporous activated carbon (AC, S-BET=1190m(2)/g) and high surface area graphite (HSAG, S-BET=400m(2)/g), were loaded with 15wt% of polyoxometalates: phosphotungstic acid (TPA) or tungstosilicic acid (STA). The four resulting catalysts were tested in the fructose reaction at moderate temperature 140 degrees C, using water and ethanol solvents. Catalytic properties have been compared with those of an acidic resin, Amberlyst 15. As relevant findings the specific interactions of carbon supports and polyoxometalates let the inhibition of active phase lixiviation. An improved catalyst (STA-HSAG) in terms of selectivity to valuable products (ethoxymethylfurfural and ethyl levulinate) and high specific catalytic activity using ethanol as solvent has been developed. This catalyst can be reused after regeneration by washing with organic solvents.