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Fraile J.M.,University of Zaragoza | Garcia-Bordeje E.,Institute Carboquimica ICB CSIC | Roldan L.,University of Zaragoza
Journal of Catalysis | Year: 2012

Sulfonated hydrothermal carbons present high activity for esterification of palmitic acid with alcohols. However, the catalyst is significantly deactivated upon recovery. Leaching of sulfonated species does not account for this deactivation, which is observed even by pretreatment only with the alcohol under reflux. Solid state NMR shows the presence of chemically bound alkyl groups coming from the alcohol, clearly different from strongly physisorbed species obtained by pretreatment at room temperature. The formation of sulfonate esters accounts for the deactivation behavior in reactions taking place in alcohols as solvents, mainly with methanol due to its higher reactivity. © 2012 Elsevier Inc. All rights reserved. Source


Callen M.S.,Institute Carboquimica ICB CSIC | Iturmendi A.,Institute Carboquimica ICB CSIC | Lopez J.M.,Institute Carboquimica ICB CSIC
Environmental Pollution | Year: 2014

One year sampling (2011-2012) campaign of airborne PM2.5-bound PAH was performed in Zaragoza, Spain. A source apportionment of total PAH by Positive Matrix Factorization (PMF) was applied in order to quantify potential PAH pollution sources.Four sources were apportioned: coal combustion, vehicular emissions, stationary emissions and unburned/evaporative emissions. Although Directive 2004/107/EC was fulfilled regarding benzo(a)pyrene (BaP), episodes exceeding the limit value of PM2.5 according to Directive 2008/50/EC were found. These episodes of high negative potential for human health were studied, obtaining a different pattern for the exceedances of PM2.5 and the lower assessment threshold of BaP (LATBaP). In both cases, stationary emissions contributed majority to total PAH. Lifetime cancer risk exceeded the unit risk recommended by the World Health Organization for those episodes exceeding the LATBaP and the PM2.5 exceedances for the warm season. For the cold season, the risk was higher for the LATBaP than for the PM2.5 exceedances. © 2014 Elsevier Ltd. All rights reserved. Source


Garcia-Bordeje E.,Institute Carboquimica ICB CSIC | Armenise S.,Institute Carboquimica ICB CSIC | Roldan L.,Institute Carboquimica ICB CSIC
Catalysis Reviews - Science and Engineering | Year: 2014

This perspective article focuses on the recent advances in the rational design of catalyst for NH3 decomposition at different length scales, from catalyst nanoparticles to reactor design. For an overall optimum performance, all scales should be optimized in a concerted manner. The study of the mechanism of reaction has given guidelines for the catalyst design. As far as reactor design is concerned, a structured reactor is beneficial for this reaction because it minimizes the inhibiting effect of produced H2 besides other inherent advantages. This holistic optimization of catalysts is expected to pave the way for application of NH3 as H2 storage media. © 2014 Taylor and Francis Group, LLC. Source


Martin A.,University of Alcala | Hernandez-Ferrer J.,Institute Carboquimica ICB CSIC | Vazquez L.,CSIC - Institute of Materials Science | Martinez M.-T.,Institute Carboquimica ICB CSIC | Escarpa A.,University of Alcala
RSC Advances | Year: 2014

This work describes a rationalization of the interactions between two fully characterized graphene nanoribbons (GNRs) and a set of significant target molecules. The GNRs were carefully synthesized by unzipping multi-walled carbon nanotubes (MWCNTs) to yield graphene oxide nanoribbons (GNRox) containing 44 wt% oxygen. The GNRox were reduced to yield reduced graphene oxide nanoribbons (GNRred) containing 14 wt%. Each material was characterized by atomic force microscopy, transmission electronic microscopy, Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and voltammetry techniques. Differential pulse voltammetry was used to assess the detection of two strategically selected groups of molecules, including benzenediols, hydroquinone, catechol, and resorcinol, as well as, l-dopa, ascorbic acid, uric acid, and l-tyrosine. The results showed that GNRs provided significantly better electrochemical responses compared to MWCNTs and the non-modified glassy carbon electrode. The chemistry of the few layers of graphene strongly influenced the electrochemical properties of the material. GNRox may be the material of choice for sensing molecules having high oxidation potentials. GNRred, on the other hand, yielded an excellent sensitivity for aromatic molecules in which π-π interactions were dominant or the number of conjugated 1,2-diols present was high. GNRred combines the advantages of the high proportion of sp2-carbon atoms with the presence of a few oxygen moieties remaining in the lattice after the reduction step. The primary interactions responsible for the shift in oxidation potentials were elucidated. This work presents new opportunities for tailoring graphene to a particular sensing application based on the specific chemistry of the molecule. © 2014 The Royal Society of Chemistry. Source


Martinez J.D.,Institute Carboquimica ICB CSIC | Martinez J.D.,Pontifical Bolivarian University | Puy N.,Institute Carboquimica ICB CSIC | Murillo R.,Institute Carboquimica ICB CSIC | And 3 more authors.
Renewable and Sustainable Energy Reviews | Year: 2013

This review deals with the state-of-the-art of waste tyre pyrolysis for the first time in literature. Pyrolysis has been addressed as an attractive thermochemical process to tackle the waste tyre disposal problem while allowing energy recovery. Pyrolysis enables the separation of carbon black from tyres and the volatile matter released (condensable and non-condensable compounds) has the potential of renewable energy recovery given the significant proportion of natural rubber present in the tyre. Given this waste-to-energy pathway, a comprehensive review has been carried out in order to show the effects of the main process conditions (heating rate, temperature, pressure, carrier gas flow rate and type, volatiles residence time and pyrolysis time) on the physicochemical properties and distributions of the resulting products (gas, liquid and solid fractions). It has also been reviewed the influence of the size and composition of the feedstock. All reported results have been framed regarding the type of reactor as well as the experimental conditions used to avoid contradictions among the large number of publications on the subject. It is shown that the occurrence of secondary reactions is very sensitive to the interaction of the aforementioned variables. Also, the main properties of the pyrolytic products are pointed out. The liquid and gaseous fractions obtained are a valuable fuel source; while the solid fraction (char) has the recovery potential of low- grade carbon black or as carbon adsorbent after applying an activation step. Special attention has been given to the liquid fraction, highlighting its properties as alternative fuel in compression ignition engines. © Copyright 2013 Published by Elsevier Ltd. All rights reserved. Source

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