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Barcelona, Spain

Lopez-Aranguren P.,CSIC - Institute of Materials Science | Lopez-Aranguren P.,Research Center | Saurina J.,University of Barcelona | Vega L.F.,Research Center | And 2 more authors.
Microporous and Mesoporous Materials | Year: 2012

The internal surface of micro and nanoporous substrates can be modified in terms of charge, functionality or even reactivity or stability by means of bifunctional organic molecules able to self-assembly. This work investigates the impregnation with trialkoxysilanes of porous systems using supercritical carbon dioxide (scCO2) as a solvent, which combines several advantages such as liquid-like density and high solvating power with gas-like transport properties. Moreover, scCO2 does not have specific interactions with the substrate and there is no competition for absorption between added reagents and solvent molecules. The work aims at describing a generic liquid-solventless impregnation method applicable to macro (perlite), meso (silica gels and agglomerated nanoparticles) and microporous (zeolite) silica-based substrates using scCO2. The hydrophobic octyltriethoxysilane was used to impregnate the internal surface of the chosen substrates with the objective of obtaining high capacity oil adsorbents. FTIR, TGA and N2 adsorption isotherms were used to determine the interactions between the substrate and the silane deposited monolayer. The acquired hydrophobic character was evaluated using the Karl Fischer method to measure the loss in water adsorption capacity after silane grafting. © 2011 Elsevier Inc. All rights reserved. Source

Lopez-Aranguren P.,CSIC - Institute of Materials Science | Lopez-Aranguren P.,Research Center | Vega L.F.,Research Center | Vega L.F.,Air Products Group | Domingo C.,CSIC - Institute of Materials Science
Chemical Communications | Year: 2013

The present work focuses on the development of a new eco-efficient method, based on the use of compressed CO2 as a solvent, reaction medium and catalyst, for the in situ polymerization of ethyleneimine inside mesoporous silica. © 2013 The Royal Society of Chemistry. Source

Builes S.,Research Center | Lopez-Aranguren P.,Research Center | Lopez-Aranguren P.,CSIC - Institute of Materials Science | Fraile J.,CSIC - Institute of Materials Science | And 3 more authors.
Journal of Physical Chemistry C | Year: 2012

Solid sorbents are considered as a potentially less-energy-intensive alternative to the use of liquids for the removal and separation of liquid and gaseous fluids. The control of the surface characteristics of porous inorganic materials via the deposition of an organic layer is of great interest for tailoring the properties of the sorbent. For instance, organic functionalization of traditional solid sorbents (micro- and mesoporous silica and silicates) allows tuning their surface properties, such as hydrophilicity or hydrophobicity and surface reactivity. However, the underlying mechanism of the sorption process in highly complex organic functionalized materials is not yet fully understood. This incomplete understanding limits the possibilities of designing optimal adsorbents for different applications increasing the interest in performing complementary experimental-simulation studies. In this work, the adsorption of N 2 in alkylsilane-modified disordered mesoporous silica (silica gel 40) and crystalline aluminosilicate (zeolite Y) is analyzed by a combination of experiments and simulations. The goal of the adsorption simulation study was two-fold: first, to assess the ability of using grand canonical Monte Carlo to obtain quantitative predictions of the adsorption characteristics of gases on alkylsilane postfunctionalized products and, second, to provide new insights into the adsorption mechanism. A supercritical silanization experimental method was used for the postmodification of the internal surface of the studied porous substrates. This work demonstrates that even though the models of amorphous hybrid materials require simplifications related to the cell size and silane polymerization modes, it is possible to use these models to obtain an adequate insight of what happens in the macroscopic systems. These models allow us to acquire information on the mechanisms of silane functionalization and the interactions of the support and silane chains with the adsorbed gases. © 2012 American Chemical Society. Source

Builes S.,Research Center Carburos Metalicos Air Products | Vega L.F.,Research Center Carburos Metalicos Air Products | Vega L.F.,Air Products Group
Journal of Physical Chemistry C | Year: 2012

It has been demonstrated that merging the inherent sorptive behavior of amorphous silica with organic groups increases the adsorption capabilities of the solid silica. However, the underlying mechanism of the adsorption process in the functionalized materials is not fully understood, limiting the possibility of designing optimal adsorbent materials for different applications; hence, the availability of complementary methods to advance in this field is of great interest. Here we present results concerning the adsorption of CO 2 in amine-functionalized silica materials, by Monte Carlo simulations, providing new insight into the capture mechanism. We propose a simulation methodology for the design of postsynthesis-functionalized silica materials in which realistic model adsorbents are generated using an energy bias selection scheme for the possible grafting sites. This methodology can be applied to different materials. In this work, we evaluate a model MCM-41 for CO 2 adsorption using grand canonical Monte Carlo simulations, and compared the results with available experimental data. A new methodology is presented, which allows accounting for the chemisorbed CO 2 on the adsorption isotherms. The results indicate that although chemisorption is an important part of this process at low pressures, physisorption also plays a significant role in the capture of CO 2 in these materials. Functionalization increases the interactions of the CO 2 molecules with the surface, whereas it decreases the available space for adsorption of CO 2; the overall efficiency of the improved adsorption lies on the availability of adsorption space versus stronger interactions. In addition to the adsorption isotherms, we studied the configurations of the amine chains during the adsorption process for different degrees of functionalization as well as the effect of the concentration of grafted amines on the adsorption isotherm. The overall results show that molecular simulations serve as a guide to quantify the CO 2 amount that can be easily sorbed for carbon capture applications, highlighting the importance of this approach. © 2012 American Chemical Society. Source

Llovell F.,CSIC - Institute of Materials Science | Llovell F.,Research Center | Vilaseca O.,CSIC - Institute of Materials Science | Vilaseca O.,Research Center | And 2 more authors.
Separation Science and Technology | Year: 2012

There is an increased interest in developing accurate tools to relate the physicochemical properties of ionic liquids (ILs) to their microscopic structure as this information is needed to speed up the design of new ionic liquids for chemical and industrial processes. Molecular models can be used for this purpose. We explore here the extended capabilities of a model previously developed in the context of soft-SAFT, by Andreu and Vega in 2007 to reproduce the thermodynamic behavior of imidazolium hexafluorophosphate-based ([C nmim][PF 6]) ionic liquids. The molecular parameters optimized in the previous work have been used here in a transferable manner; some new members of the [C nmim][PF 6] family have also been added, as new recent experimental data has been published. The interfacial tensions have been calculated using a Density Gradient Approach and the results have been compared with available experimental data. The solubility of carbon monoxide and hydrogen in those ILs has been studied in the range of temperatures and pressures of application for separation processes. Binary mixtures with other imidazolium ionic liquids with different anions have been calculated, in a predictive manner. Finally, calculations of mixtures of ionic liquids with water also show very good agreement with experimental data. This work highlights the importance of using a simple but robust thermodynamic model, including the right level of interactions, to accurately describe the properties of these highly non-ideal systems. © 2012 Copyright Taylor and Francis Group, LLC. Source

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