Au-Cu/SBA(Ti) based catalysts for photocatalytic applications

Comunicación a congresoIn this work, it has been synthesized several Au and Au-Cu alloy photocatalysts supported on two different mesoporous supports: a non-commercial SBA-15 and a post-synthesis TiO2 modified SBA-15 (TiSBA-15), with which a high dispersion of TiO2 species have been achieved maintaining the SBA-15 structure. In addition, it has also been obtained highly dispersed Au nanoparticles confined in SBA-15 pore channels, as can be observed in Figure 1. The photocatalysts have been preliminary tested in the preferential CO oxidation in a H2-rich stream (CO-PROX) at room temperature and atmospheric pressure under simulated solar light irradiation. In spite of the very low gold and copper loading (1.5 wt% and 0.5wt% respectively), the catalysts resulted active and selective in the low temperature photo-CO-PROX.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tec

Role of Mo in catalysts based on noble metals in hydrodeoxygenation reactions

The use of bio-energy as a renewable alternative to fossil fuels is nowadays attracting more and more attention. The bio-fuel from biomass seems to be a potential energy substitute for fossil fuels since it is a renewable resource that could contribute to sustainable development and global environmental preservation and it appears to have significant economic potential1. The problem is its high oxygen content, which gives undesirable properties for combustion. To remove oxygen, catalytic hydrodeoxygenation (HDO) reactions are carried out. Monometallic Mo/Si, Pt/Si as well as bimetallic PtMo/Si catalysts were prepared and evaluated in the hydrodeoxygenation (HDO)reaction of dibenzofurane (DBF) as a model molecule in biomass derived bio-oil.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Sustainable organic dyes from winemaking lees for photoelectrochemical dye-sensitized solar cells

During the last two decades, Dye Sensitized Solar Cells (DSSCs) have received a great deal of attention as a promising, low-cost alternative to conventional silicon photovoltaic devices. Natural dye molecules can be used as a sensitizer for their low cost, good light absorbance, easy preparation process, and biodegradability. In this study, dyes were obtained from wine lees, the last by-product of winemaking process, supplied by a venetian winery (Italy). Polyphenols, like tannins and anthocyanins, which were extracted from winemaking lees, were adsorbed on a nanostructured ordered mesoporous titanium dioxide, previously treated at different temperatures (400-600 ffiC). Both dyes and titania semiconductor samples were studied with different techniques. The tests were carried out on prototypes to evaluate the cell power and the photocurrent generated under simulated solar light irradiation. The obtained solar energy conversion efficiencies are comparable to those that were reported in literature by using organic dyes extracted from vegetables, fruits, and plants. It is significant that these dyes are largely available and cost effective, since recovered from a waste otherwise to be disposed of, opening up a perspective of feasibility for inexpensive and environmentally friendly dye solar cells to generate green electricity and transforming agri-food waste into a resource

Nanoestructuras de ceria-titania para fotodegradar azul de metileno con luz solar simulada

En los últimos años la protección ambiental y el uso de fuentes de energía renovables son dos objetivos principales en la investigación química. La energía solar se puede aprovechar para la degradación fotocatalítica de moléculas orgánicas contaminantes, hormonas o medicamentos, tanto en el aire, en el agua, como en las superficies, porque la luz solar es capaz de descomponerlas [1]. A pesar de la gran cantidad de aplicaciones fotocatalíticas de la titania (TiO2), fotocatalizador no tóxico, de bajo costo y muy prometedor [2], hay algunos factores críticos que limitan su fotoactividad. El principal es el valor de su salto de energía, que limita su uso como fotocatalizador en la región UV del espectro. Con el objetivo principal de extender su uso a la región visible del espectro, en literatura se ha propuesto el depósito de metales nobles en su superficie, modificaciones superficiales, así como el dopaje con iones de metales de transición o elementos de tierras raras. En este sentido, el uso de ceria (CeO2) ha atraído una gran atención debido a propiedades como su biocompatibilidad, inercia química así como su actividad en reacciones de oxidación, relacionada con la formación vacantes de oxígeno en su superficie [3]. Se ha comprobado que el sistema oxídico mixto CeO2-TiO2 es más fotoactivo que la titania pura debido a la disminución del salto de energía y a la mejora en la movilidad de los excitones. Este trabajo tiene como objetivo desarrollar fotocatalizadores basados en nanoestructuras de titania que sean activas en el visible, dopando la matriz de titania con cerio. Principalmente se pretende evaluar tanto el papel del cerio como la morfología del nanomaterial en la respuesta fotocatalítica bajo luz UV y solar.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

CO2 hydrogenation over Ru hydrotalcite-derived catalysts

The hydrogenation of CO2 over Ru catalysts is structure sensitive, the selectivity of the process can be driven either to the production of CH4 or CO depending on Ru particles and support features. Herein, Ru-based MgAl-HT (HT=hydrotalcite) derived catalysts with different Ru loadings (0.5, 1.0 and 2.0 wt%) and promoted with La3+ were prepared, characterized, and tested for CO2 methanation at high Gas Hourly Space Velocity values (480 L/gcat h) feeding a CO2/H2/N2 = 1/4/1 v/v mixture. The MgAlOx mixed oxide obtained after calcination at 600 °C and reduction provided weak, medium and mainly strong basic sites, able to activate the CO2 molecule, and hosted very small Ru nanoparticles (1–3 nm). However, the catalysts displayed a low activity in the low temperature range and a poor selectivity to CH4. The addition of La3+, despite contributing to the basicity, did not have any significant effect on performance. In a comparison between Ru- and Ni-HT-derived catalysts, tested under similar reaction conditions, Ni largely overperformed Ru

NiO diluted in high surface area TiO2 as efficient catalysts for the oxidative dehydrogenation of ethane

[EN] Catalysts consisting of NiO diluted in high surface area TiO2 can be as efficient in the oxidative dehydrogenation of ethane as the most selective NiO-promoted catalysts reported previously in the literature. By selecting the titania matrix and the NiO loading, yields to ethylene over 40% have been obtained. In the present article, three different titanium oxides (TiO2) have been employed as supports or diluters of nickel oxide and have been tested in the oxidative dehydrogenation of ethane to ethylene. All TiO2 used present anatase as the main crystalline phase and different surface areas of 11,55 and 85 m(2) g(-1). It has been observed that by selecting an appropriate nickel loading and the titanium oxide extremely high selectivity towards ethylene can be obtained. Thus, nickel oxide supported on TiO2 with high surface areas (i.e. 55 and 85 m(2) g(-1)) have resulted to give the best catalytic performance although the optimal nickel loading is different for each case. The optimal catalyst has been obtained for NiO-loadings up to 5-10 theoretical monolayers regardless of the TiO2 employed. Free TiO2 is inactive whereas unsupported NiO is active and unselective (forming mainly carbon dioxide) and, therefore, unmodified NiO particles have to be avoided in order to obtain the optimal catalytic performance. The use of low surface area titania (11 m(2) g(-1)) have led to the lowest selectivity to olefin due to the presence of an excess of free NiO particles. (C) 2017 Elsevier B.V. All rights reserved.The authors would like to acknowledge the DGICYT in Spain CTQ2012-37925-C03-2, CTQ2015-68951-C3-1-R, CTQ2015-68951-C3-3-R and SEV-2012-0267 Projects for financial support. D.D. also thanks Severo Ochoa Excellence fellowship (SVP-2014-068669). We also thank the University of Valencia (UV-INV-AE-16-484416 project) and SCSIE-UV for assistanceSanchis, R.; Delgado-Muñoz, D.; Agouram, S.; Soriano Rodríguez, MD.; Vázquez, MI.; Rodriguez-Castellon, E.; Solsona, B.... (2017). NiO diluted in high surface area TiO2 as efficient catalysts for the oxidative dehydrogenation of ethane. Applied Catalysis A General. 536:18-26. https://doi.org/10.1016/j.apcata.2017.02.012S182653

Porous clays heterostructures as supports of iron oxide for environmental catalysis

[EN] Porous Clays Heterostructures (PCH) from natural pillared clays (bentonite with a high proportion of montmorillonite) have been used as supports of iron oxide for two reactions of environmental interest: i) the elimination of toluene (a representative compound of one of the most toxic subsets of volatile organic compounds, aromatics) by total oxidation and ii) the selective oxidation of H2S to elemental sulfur. For both reactions these catalysts have resulted to be remarkably more efficient than similar catalysts prepared using conventional silica as a support. Thus, in the total oxidation of toluene it has been observed that the catalytic activity obtained using siliceous PCH is two orders of magnitude higher than that with conventional silica. The catalytic activity has shown to be dependant of the capacity of the support for dispersing iron oxide in a way that the higher the dispersion of iron oxide on the surface of the support, the higher is the activity. In the case of the selective oxidation of H2S to S both higher catalytic activity and higher selectivity to S have been observed using siliceous porous clays heterostructures than using conventional silica. Highly dispersed FeOx species have been shown as highly selective towards elemental sulfur whereas more aggregated FeOx species favour the formation of sulphur oxides decreasing the selectivity to S. Analyses of the surface by XPS have shown the predominance of sulfate species in the catalysts presenting low selectivity to elemental sulfur.The authors would like to acknowledge the DGICYT in Spain (CTQ2015-68951-C3-1-R, CTQ2015-68951-C3-3-R, CTQ2012-37925-C03-2, CTQ2012-37925-C03-3 and CTQ2012-37984-C02-01) and FEDER for financial support. We also thank the University of Valencia for funding (UV-INV-AE-16-484416) and SCSIE-UV for assistance.Sanchis Martinez, R.; Cecilia, J.; Soriano Rodríguez, MD.; Vazquez, I.; Dejoz, A.; López Nieto, JM.; Rodriguez-Castellon, E.... (2008). Porous clays heterostructures as supports of iron oxide for environmental catalysis. Chemical Engineering Journal. 334:1159-1168. https://doi.org/10.1016/j.cej.2017.11.060S1159116833

The Carnegie Supernova Project I: photometry data release of low-redshift stripped-envelope supernovae

The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated supernova follow-up program based at the Las Campanas Observatory that collected science data of young, low-redshift supernovae between 2004 and 2009. Presented in this paper is the CSP-I photometric data release of low-redshift stripped-envelope core-collapse supernovae. The data consist of optical (uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared (YJH) photometry. Twenty objects have optical pre-maximum coverage with a subset of 12 beginning at least five days prior to the epoch of B-band maximum brightness. In the near-infrared, 17 objects have pre-maximum observations with a subset of 14 beginning at least five days prior to the epoch of J-band maximum brightness. Analysis of this photometric data release is presented in companion papers focusing on techniques to estimate host-galaxy extinction (Stritzinger et al., submitted) and the light-curve and progenitor star properties of the sample (Taddia et al., submitted). The analysis of an accompanying visual-wavelength spectroscopy sample of ~150 spectra will be the subject of a future paper.Comment: Updated a couple of small error

The Carnegie Supernova Project-I. Optical spectroscopy of stripped-envelope supernovae

We present 170 optical spectra of 35 low-redshift stripped-envelope core-collapse supernovae observed by the Carnegie Supernova Project-I between 2004 and 2009. The data extend from as early as -19 days (d) prior to the epoch of B-band maximum to +322 d, with the vast majority obtained during the so-called photospheric phase covering the weeks around peak luminosity. In addition to histogram plots characterizing the red-shift distribution, number of spectra per object, and the phase distribution of the sample, spectroscopic classification is also provided following standard criteria. The CSP-I spectra are electronically available and a detailed analysis of the data set is presented in a companion paper being the fifth and final paper of the seriesComment: Resubmitted to A&A after address referee's comments. Comments welcomed, and let us know if we missed to reference your paper