WorldCat Identities

Sayós Ortega, Ramón

Works: 14 works in 24 publications in 2 languages and 21 library holdings
Roles: Author
Publication Timeline
Most widely held works by Ramón Sayós Ortega
Models and computational methods applied to industrial gas separation processes and enhanced oil recovery by Gerard Alonso Benito( Book )

2 editions published in 2019 in English and held by 2 WorldCat member libraries worldwide

"Two main topics are treated in this doctoral thesis from a theoretical and computational point of view: the gas capture and separation from post-combustion flue gases, and the enhanced oil recovery from oil reservoirs. The first topic evaluates the separation of CO2 using three different materials. First, several zeolites from the Faujasite family are studied with a combination of Density Functional Theory (DFT) and Monte Carlo methods. The former is employed to understand the driving mechanisms of adsorption, whereas the latter served to assess the separation of CO2 from a flue gas formed by a ternary mixture of CO2, N2 and O2. Second, the adsorption of CO2, N2 and SO2 into Mg-MOF-74 obtained through DFT calculations is presented to determine the most fundamental gas/MOF interactions. The results are then coupled to a Langmuir isotherm model to derive the macroscopic adsorption isotherms of the three gases in Mg-MOF-74. Finally, the absorption of CO2 and SO2 into three different phosphonium-based Ionic Liquids (ILs) is addressed by using the soft-SAFT equation of state and the COSMO-RS model. From the calculated adsorption/absorption isotherms several properties are obtained, such as the purity in the recovered gas, the working capacity of the materials and their selectivity to capture CO2 in the presence of other contaminant species. The main results obtained from this part of the thesis reveal that the cations of microporous materials are very strong sites of absorption for polar gases (i.e., the Na+ cations in Faujasites or the Mg2+ cations in Mg-MOF-74). This feature makes them very good candidates for CO2 capture, but they can be easily poisoned by other polar gases such as SO2. For this reason, it is highly recommended to desulphurize the flue gas before using any of these adsorbents. Similarly, ILs have higher affinity for SO2 than for CO2. However, the gas/IL interactions are significantly weaker, so they do not become poisoned by SO2. This fact implies that SO2 can be captured and separated from the flue gas by using a phosphonium-based IL.The second topic describes via Molecular Dynamics simulations the interactions of several model oils with different rocks and brines. The obtained insight can be applied in better understanding the interactions of the species present at oil reservoirs, with direct application in enhanced oil recovery processes. To that end, two wettability indicators are monitored to determine the potential recovery of the model oils. First, the oil/water interfacial tension (IFT) under different conditions of temperature, pressure and salinity (i.e., from pure water to 2.0 mol/kg of NaCl or CaCl2). And second, the oil/water/rock contact angle (CA) on calcite (10-14) and kaolinite (001) also as a function of salinity (i.e., from pure water to 2.0 mol/kg of NaCl or CaCl2). The different model oils are built with molecules of different chemical nature representing the Saturate/Aromatic/Resin/Asphaltene (SARA) fractionation model. In a final stage of the doctoral thesis the effect of non-ionic surfactants at the oil/brine IFT is also included. The main results obtained show that the most polar components of oil migrate to the oil/water interface and reduce the IFT. However, the same compounds feel attracted to the rock, who increase the CA and hamper the oil recovery. Some of these interactions are affected by the presence of salt. Specifically, if a water layer is formed between the oil and the rock in a reservoir, electrolytes can diffuse into it and attract the polar components of oil, ultimately increasing the CA. Finally, cations can be attracted to the oil/water interface due to salt/surfactant interactions. Both species interact synergistically to modify their orientation/distribution at the interface and reduce the oil/water IFT." -- TDX
Theoretical modeling of heterogeneous catalysts based on platinum and cerium oxide by Albert Bruix Fusté( Book )

2 editions published in 2014 in English and held by 2 WorldCat member libraries worldwide

En aquesta tesi s'han utilitzat mètodes teòrics basats en la DFT per estudiar les propietats de sistemes formats per Pt i CeO2. Mitjançant un anàlisi de l'estructura electrònica i geomètrica dels models considerats, s'ha contribuït a la comprensió a nivell microscòpic de les interaccions entre Pt i CeO2. Així, s'han descrit els processos de transferència de càrrega entre diferents espècies de Pt i substrats de CeO2, resultant en l'oxidació de les espècies metàl·liques i la reducció de cations Ce. A més, s'ha demostrat que la presència del platí facilita la reducció de l'òxid de ceri a través de processos de migració (spillover) d'àtoms d'oxigen i que aquest efecte és més pronunciat quan el CeO2 és nanoestructurat. Això ha permès explicar per primera vegada els mecanismes de formació de vacants en catalitzadors basats en Pt i CeO2, que són responsables de la seva capacitat d'emmagatzemar oxigen i per tant, de la seva activitat catalítica. Amb els models de nanopartícules de CeO2, s'ha descrit l'existència de complexos d'adsorció on el Pt es troba dispersat atòmicament i en forma de catió a la superfície de les nanopartícules de cèria. A més, aquestes espècies es poden utilitzar com a electrocatalitzadors en els ànodes de cel·les de combustible, permetent el desenvolupament de dispositius que utilitzin platí de forma més eficient i, per tant, reduint-ne dràsticament els costos. L'estudi de la reactivitat de diferents espècies de Pt envers la reacció WGS mitjançant la determinació del perfil energètic de la dissociació de l'H2O ha permès caracteritzar els efectes que tenen la mida de la partícula de Pt i les interaccions metall-suport amb l'òxid de ceri en l'activitat d'aquests catalitzadors. S'ha demostrat l'excepcional activitat catalítica d'aquests sistemes i s'han identificat les propietats que els fan més reactius, superant en rendiment als catalitzadors que s'utilitzen industrialment per a catalitzar la WGS. Els estudis realitzats durant aquesta tesi han permès descriure detalladament propietats de sistemes formats per Pt i CeO2. Aquesta caracterització serveix per comprendre els sistemes catalítics basats en aquests materials i per guiar el disseny racional de nous materials amb les propietats catalítiques idònies per a cada aplicació
Procesos químicos con oxígeno y nitrógeno sobre [beta]-cristobalita : estudio teórico desde primeros principios by Carina Arasa Cid( Book )

2 editions published in 2007 in Spanish and held by 2 WorldCat member libraries worldwide

Atomic and molecular oxygen collision processes over some crystalline solids by Víctor Morón Tejero( Book )

3 editions published between 2011 and 2012 in English and held by 2 WorldCat member libraries worldwide

Estudio teórico de procesos elementales reactivos reacciones del O(3P) con CS(X1E+) y CS2(X1Eg+) by Ramón Sayós Ortega( Book )

2 editions published between 1988 and 1990 in Spanish and held by 2 WorldCat member libraries worldwide

Monte Carlo based methods applied to heterogeneous catalysis and gas separation by Hèctor Prats Garcia( Book )

2 editions published in 2019 in English and held by 2 WorldCat member libraries worldwide

"The research work presented in this thesis is divided in two main topics: gas separation and heterogeneous catalysis. Although the systems studied in one part and another are quite different, they share two fundamental features: both topics have a special industrial interest and they have been studied through stochastic Monte Carlo based methods. The present work on gas separation aims to assess the performance of several faujasite structures, a well-known family of zeolites, in CO2 capture processes. Concretely, ten faujasite structures with different Al content have been evaluated in the separation of post-combustion CO2 mixtures via simulation of swing adsorption processes. Through GCMC simulations performed on a wide range of pressures and temperatures, the pure and mixture adsorption isotherms and isobars for the different structures are obtained. This data is used to calculate several performance criteria such as purity, working capacity, selectivity and energy required per ton of CO2 captured. The results show that high Al content structures are suitable for operating under a TSA unit, while intermediate and low Al content structures show better performance in PSA and VSA units, respectively. On the other hand, the research work on chemical reactivity focus on the study of the water-gas shift reaction (WGSR) on copper surfaces both from a thermodynamic and from a kinetic point of view. First, a kMC study is performed on the flat Cu(111) surface. The lattice model is quite simple, consisting on an hexagonal periodic grid of points. All sites are considered equivalent, and only repulsive lateral interactions between neighboring CO adsorbed species are included. However, even with this simple model, the kMC results agree quite well to the available experimental data, and demonstrate that the dominant reaction mechanism is the COOH mediated associative mechanism. The effect of van der Waals interactions is then studied, by performing DFT calculations of the WGSR on Cu(321) using the Grimme D2 correction accounting for the dispersion forces. The results obtained are compared with previous DFT results published in the literature where no van der Waals corrections were included. The comparison shows big differences on the adsorption energies of some gas species, as well as important differences in some energy barriers, hence demonstrating the importance of including dispersion terms in order to obtain a meaningful description of the energetics of the WGSR. New kMC simulations are then performed for the WGSR on Cu(321) surface to study the effect of step sites on the WGSR activity. The recently developed graph- theoretical kMC framework is used, coupled with cluster expansion Hamiltonians to account for the lateral interactions between neighboring species. The simulation results show that the activity is much lower on the stepped Cu(321) surface. Analysis of the kMC simulations suggests that the reason in the poisoning of step sites by CO species, as well as the presence of low energy barriers for some key steps on the reverse direction (e.g. water dissociation and COOH formation). Finally, the thesis ends with a brief tutorial on kMC simulations where several issues are discussed, like the importance of including diffusion processes of the effect of lateral interactions." -- TDX
Theoretical reaction and relaxation dynamics in superfluid helium nanodroplets by Miquel Blancafort Jorquera( Book )

2 editions published in 2019 in English and held by 2 WorldCat member libraries worldwide

The study of superfluid helium has been carried out mainly by physicists. In recent years, taking advantage of the potentialities presented by superfluid helium nanodroplets (HeNDs) as inert matrices at very low temperatures (0.37 K), the chemical community became involved in its application to high-resolution spectroscopy. More recently (early 2000s), this community began to be involved in research using HeNDs to investigate chemical reactivity in this quantum solvent. As for the theoretical studies on the dynamics of physicochemical processes in HeNDs, they have been possible about five years ago and the number of theoretical dynamics studies, despite their interest, is very scarce. The main objective of this thesis is to contribute to the development of the research in this area.To introduce the reader into the topic, Chapter 1 is divided into four sections: the first one describes the properties of helium, the second one considers the history of the discovery and research carried out on the superfluidity phenomenon, the third one outlines the properties of superfluid helium nanodroplets, and the last one gives an overview of the applications and fields of study implying HeNDs.The theoretical and numerical methods used to describe superfluid liquid helium are detailed in Chapter 2. In the first section attention has been paid on the density functional theory (DFT) and its time dependent extension for real-time simulations (TDDFT). The second section describes the main density functionals used and the third section is aimed to present the numerical methods employed to perform the TDDFT calculations.The following four chapters contain the original studies carried out in this thesis. The investigation of the capture process of a Ne atom by a HeND can be found in Chapter 3. Here, the atom is treated using classical mechanics and the influence of energy and angular momentum is examined for a wide set of initial conditions. The microscopic mechanism, energy and angular momentum exchanges and vortex formation have been extensively analysed. The present contribution corresponds to the first systematic analysis of the influence of angular momentum in the capture process and vortex formation.Chapter 4 represents a natural evolution from Chapter 3 and describes the formation of a neon dimer or neon adduct inside a superfluid helium nanodroplet, treating both atoms classically. Analogously as in the previous chapter, angular momentum has also been taken into consideration and the mechanism, energy an angular momentum exchanges and vortex formation are analysed. These two chapters complement and extend two previous investigations of our group where the Ne atoms were treated using standard quantum mechanics at zero angular momentum. The contents of Chapter 4 correspond to the second theoretical investigation on bimolecular reaction dynamics in HeNDs.The following two chapters use a full quantum hybrid approach to explore rotational and vibrational energy relaxation dynamics. Chapter 5 corresponds to the first theoretical study reported so far on the rotational energy relaxation dynamics of molecules in HeNDs. This process has been studied using several isotopes of the H2 molecule (fast rotors) and considering a set of initial excitations and nanodroplet sizes.The last investigation (Chapter 6) is centred on the study of the vibrational energy relaxation in HeNDs. Thus, the influence of the energy gap between the vibrational levels, molecule-helium interaction energy and nanodroplet size on the vibrational relaxation dynamics has been analysed, taking as a reference the I2@(4He)100 doped nanodroplet which was recently studied in our group. To the best of our knowledge it is the first time that the influence of these key factors has been examined.Finally, in Chapters 7 and 8 the main conclusions and a summary in Catalan are presented
Estudio teórico de procesos elementales radiactivos : reacciones del O(3P) con CS(X1[sigma]+) y CS2(X1[sigma]g+) by Ramón Sayós Ortega( Book )

1 edition published in 1990 in Spanish and held by 1 WorldCat member library worldwide

Estudio experimental y teórico de reacciones químicas relevantes para la química atmosférica entre O(1D) e hidrocarburos by Jordi Hernando Campos( )

1 edition published in 2000 in Spanish and held by 1 WorldCat member library worldwide

The Atmospheric reaction of the excited nitrogen atom with molecular oxygen : ab initio study of the potential energy surfaces and classical and quantum dynamincs by Irene Miquel Plana( )

1 edition published in 2002 in English and held by 1 WorldCat member library worldwide

Atomic and molecular data for spacecraft re-entry plasmas( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

Abstract: The modeling of atmospheric gas, interacting with the space vehicles in re-entry conditions in planetary exploration missions, requires a large set of scattering data for all those elementary processes occurring in the system. A fundamental aspect of re-entry problems is represented by the strong non-equilibrium conditions met in the atmospheric plasma close to the surface of the thermal shield, where numerous interconnected relaxation processes determine the evolution of the gaseous system towards equilibrium conditions. A central role is played by the vibrational exchanges of energy, so that collisional processes involving vibrationally excited molecules assume a particular importance. In the present paper, theoretical calculations of complete sets of vibrationally state-resolved cross sections and rate coefficients are reviewed, focusing on the relevant classes of collisional processes: resonant and non-resonant electron-impact excitation of molecules, atom-diatom and molecule-molecule collisions as well as gas-surface interaction. In particular, collisional processes involving atomic and molecular species, relevant to Earth (N2, O2, NO), Mars (CO2, CO, N2) and Jupiter (H2, He) atmospheres are considered
Ab initio study of the O(1D), O(3P) + N2O and N(2D) + NO reactions of interest in atmospheric chemistry and combustion processes by Rosendo Valero Montero( )

2 editions published in 1997 in English and held by 1 WorldCat member library worldwide

Estudio teórico de reacciones en fase gas y gas-superficie de interés atmosférico y tecnológico : tesis doctoral by Pablo Gamallo Belmonte( Book )

2 editions published in 2007 in Spanish and held by 1 WorldCat member library worldwide

De la estructura electrónica a la dinámica de reacciones : estudio teórico de los sistemas O(3P,1D)+H2O y N(4S)+O2 by Carolina Oliva García( )

1 edition published in 2001 in Spanish and held by 1 WorldCat member library worldwide

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Sayós R onderzoeker