Publications
307 results found
Chremos A, Forte E, Papaioannou V, et al., 2015, Modelling the phase and chemical equilibria of aqueous solutions of alkanolamines and carbon dioxide using the SAFT-γ SW group contribution approach, Fluid Phase Equilibria, Vol: 407, Pages: 280-297, ISSN: 0378-3812
The speciation reactions that take place in mixtures of water, carbon dioxide (CO2), and alka-nolamines make the modelling of the chemical and uid-phase equilibria of these systems chal-lenging. We demonstrate for the rst time that the statistical associating uid theory (SAFT),formulated within a group-contribution (GC) framework based on transferable intermolecularsquare-well (SW) potentials (SAFT- SW) can be used to model successfully such complexreacting systems. The chemical reactions in these mixtures are described via a physical associ-ation model. The concept of second-order groups is introduced in the SAFT- SW approach inorder to deal with the multifunctional nature of the alkanolamines. In developing the models,several compounds including ethylamine, propylamine, ethanol, propanol, 2-aminoethanol and3-amino-1-propanol are considered. We present calculations and predictions of the uid-phasebehaviour of these compounds and a number of their aqueous mixtures with and without CO2.The group-contribution nature of the models can be used to predict the absorption of carbondioxide in aqueous solutions of 5-amino-1-pentanol and 6-amino-1-hexanol. The proposed pre-dictive approach offers a robust platform for the identi cation of new solvents and mixturesthat are viable candidates for CO2 absorption, thereby guiding experimental studies.
Sadeqzadeh M, Papaioannou V, Dufal S, et al., 2015, The development of unlike induced association-site models to study the phase behaviour of aqueous mixtures comprising acetone, alkanes and alkyl carboxylic acids with the SAFT-γ Mie group contribution methodology, Fluid Phase Equilibria, Vol: 407, Pages: 39-57, ISSN: 0378-3812
Providing accurate predictions of the thermodynamic properties of highly polar and hydrogen bonding compounds and their mixtures is challenging from a theoretical perspective. The combination of an equation of state (EoS) based on the statistical associating fluid theory (SAFT) with a group contribution (GC) methodology offers both accuracy and predictive capability for the thermodynamic properties of mixtures. In our current work, the SAFT-γ Mie equation of state is used to capture the underlying complexity of systems in which specific interactions (e.g. hydrogen bonding, dipolar interactions, chemical association) play an important role, by incorporating highly versatile association-site schemes to model mixtures in which unlike induced association interactions occur; this is done by assigning to the functional groups a number of association sites that are inactive in the pure fluid, but become active in certain mixtures. We refer to this type of association mechanism as "unlike induced" association and to the sites involved in this interaction as "unlike induced" association sites. The concept of unlike induced association sites is applied here to develop reliable SAFT-γ Mie group contribution models to describe the properties of acetone, alkyl carboxylic acids, and their mixtures with water and n-alkanes. The parameter table of available SAFT-γ Mie models is expanded to incorporate the corresponding group interaction parameters for acetone, which is treated as a molecular group, the carboxyl group COOH, and their unlike interaction group parameters with water, and the methyl CH<inf>3</inf>, methanediyl CH<inf>2</inf>, and methanetriyl CH alkyl groups. In particular, one unlike induced site is used with the acetone model to mediate hydrogen bonding of the acetone oxygen in mixtures containing hydrogen bond donors, and two pairs of unlike induced sites are included on the COOH group to mediate hydrogen
Papadokonstantakis S, Badr S, Hungerbühler K, et al., 2015, Toward Sustainable Solvent-Based Postcombustion CO<inf>2</inf> Capture: From Molecules to Conceptual Flowsheet Design, Computer Aided Chemical Engineering, Vol: 36, Pages: 279-310, ISSN: 1570-7946
Solvent-based postcombustion carbon dioxide (CO<inf>2</inf>) capture requires minimum retrofitting of current CO<inf>2</inf>-emitting power plants but is challenging because of the high energy penalty in solvent regeneration and the environmental impacts of solvent degradation. Research efforts are predominantly based on lab and pilot-scale experiments to select solvents and process systems which improve the overall performance of this technology. Notwithstanding the value of the experimental efforts, this study proposes an efficient computational approach for screening a vast number of commercial and novel solvents and process configurations. Computer-aided molecular design, advanced group contribution methods, process synthesis, and multicriteria sustainability assessment are combined to provide new insights in solvent-based CO<inf>2</inf> capture. This study provides details of the data requirements, highlights several high-performance solvents and process configurations, and quantifies the benefits from economic, life cycle, and hazard assessment perspective. Thus, it also provides information for the experimental approaches, focusing on a narrower, near-optimum design space.
Habgood M, Sugden IJ, Kazantsev AV, et al., 2015, Efficient handling of molecular flexibility in ab initio generation of crystal structures, Journal of Chemical Theory and Computation, Vol: 11, Pages: 1957-1969, ISSN: 1549-9618
A key step in many approaches to crystal structure prediction (CSP) is the initial generation of large numbers of candidate crystal structures via the exploration of the lattice energy surface. By using a relatively simple lattice energy approximation, this global search step aims to identify, in a computationally tractable manner, a limited number of likely candidate structures for further refinement using more detailed models. This paper presents an effective and efficient approach to modeling the effects of molecular flexibility during this initial global search. Local approximate models (LAMs), constructed via quantum mechanical (QM) calculations, are used to model the conformational energy, molecular geometry, and atomic charge distributions as functions of a subset of the conformational degrees of freedom (e.g., flexible torsion angles). The effectiveness of the new algorithm is demonstrated via its application to the recently studied 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) molecule and to two molecules, β-d-glucose and 1-(4-benzoylpiperazin-1-yl)-2-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)ethane-1,2-dione, a Bristol Myers Squibb molecule referenced as BMS-488043. All three molecules present significant challenges due to their high degree of flexibility.
Rhazaoui K, Cai Q, Kishimoto M, et al., 2015, Towards the 3D Modelling of the Effective Conductivity of Solid Oxide Fuel Cell Electrodes - Validation against experimental measurements and prediction of electrochemical performance, Electrochimica Acta, Vol: 168, Pages: 139-147, ISSN: 1873-3859
The effective conductivity of thick-film solid oxide fuel cell (SOFC) electrodes plays a key role in their performance. It determines the ability of the electrode to transport charge to/from reaction sites to the current collector and electrolyte. In this paper, the validity of the recently proposed 3D resistor network model for the prediction of effective conductivity, the ResNet model, is investigated by comparison to experimental data. The 3D microstructures of Ni/10ScSZ anodes are reconstructed using tomography through the focused ion beam and scanning electron microscopy (FIB-SEM) technique. This is used as geometric input to the ResNet model to predict the effective conductivities, which are then compared against the experimentally measured values on the same electrodes. Good agreement is observed, supporting the validity of the ResNet model for predicting the effective conductivity of SOFC electrodes. The ResNet model is then combined with the volume-of-fluid (VOF) method to integrate the description of the local conductivity (electronic and ionic) in the prediction of electrochemical performance. The results show that the electrochemical performance is in particular sensitive to the ionic conductivity of the electrode microstructure, highlighting the importance of an accurate description of the local ionic conductivity.
Kleniati P-M, Adjiman CS, 2015, A generalization of the Branch-and-Sandwich algorithm: From continuous to mixed-integer nonlinear bilevel problems, COMPUTERS & CHEMICAL ENGINEERING, Vol: 72, Pages: 373-386, ISSN: 0098-1354
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- Citations: 36
Burger J, Papaioannou V, Gopinath S, et al., 2015, A hierarchical method to integrated solvent and process design of physical CO<inf>2</inf> absorption using the SAFT-γ Mie approach, AIChE Journal, Vol: 61, Pages: 3249-3269, ISSN: 0001-1541
Molecular-level decisions are increasingly recognized as an integral part of process design. Finding the optimal process performance requires the integrated optimization of process and solvent chemical structure, leading to a challenging mixed-integer nonlinear programming (MINLP) problem. The formulation of such problems when using a group contribution version of the statistical associating fluid theory, SAFT-γ Mie, to predict the physical properties of the relevant mixtures reliably over process conditions is presented. To solve the challenging MINLP, a novel hierarchical methodology for integrated process and solvent design (hierarchical optimization) is presented. Reduced models of the process units are developed and used to generate a set of initial guesses for the MINLP solution. The methodology is applied to the design of a physical absorption process to separate carbon dioxide from methane, using a broad selection of ethers as the molecular design space. The solvents with best process performance are found to be poly(oxymethylene)dimethylethers.
Gopinath S, Galindo A, Jackson G, et al., 2015, Computer aided molecular and process design using complex process and thermodynamic models: A screening based approach, Pages: 107-109
The design of optimal processing materials (molecules) and optimal process variables for a given process is referred to as Computer Aided Molecular and Process Design (CAMPD). Processing materials used to achieve process goals include mass separating agents (such as solvents for absorption, extraction, leaching and adsorbents), catalysts, heat transfer fluids and reaction medium solvents. Choosing processing molecules influences the optimal process variables and vice versa. Molecular and process decision variables are linked, interacting with each other in a complex manner. Hence, neither of these decisions can be made in isolation.
Nerantzis D, Adjiman CS, 2015, Deterministic Global Optimization and Transition States, 12TH INTERNATIONAL SYMPOSIUM ON PROCESS SYSTEMS ENGINEERING (PSE) AND 25TH EUROPEAN SYMPOSIUM ON COMPUTER AIDED PROCESS ENGINEERING (ESCAPE), PT A, Vol: 37, Pages: 851-856, ISSN: 1570-7946
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- Citations: 2
Cai Q, Adjiman CS, Brandon NP, 2014, Optimal control strategies for hydrogen production when coupling solid oxide electrolysers with intermittent renewable energies, JOURNAL OF POWER SOURCES, Vol: 268, Pages: 212-224, ISSN: 0378-7753
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- Citations: 44
Pereira FE, Galindo A, Jackson G, et al., 2014, On the impact of using volume as an independent variable for the solution of <i>P</i>-<i>T</i> fluid-phase equilibrium with equations of state, COMPUTERS & CHEMICAL ENGINEERING, Vol: 71, Pages: 67-76, ISSN: 0098-1354
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- Citations: 10
Kleniati P-M, Adjiman CS, 2014, Branch-and-Sandwich: a deterministic global optimization algorithm for optimistic bilevel programming problems. Part I: Theoretical development, Journal of Global Optimization, Vol: 60, Pages: 425-458, ISSN: 0925-5001
We present a global optimization algorithm, Branch-and-Sandwich, for optimistic bilevel programming problems that satisfy a regularity condition in the inner problem. The functions involved are assumed to be nonconvex and twice continuously differentiable. The proposed approach can be interpreted as the exploration of two solution spaces (corresponding to the inner and the outer problems) using a single branch-and-bound tree. A novel branching scheme is developed such that classical branch-and-bound is applied to both spaces without violating the hierarchy in the decisions and the requirement for (global) optimality in the inner problem. To achieve this, the well-known features of branch-and-bound algorithms are customized appropriately. For instance, two pairs of lower and upper bounds are computed: one for the outer optimal objective value and the other for the inner value function. The proposed bounding problems do not grow in size during the algorithm and are obtained from the corresponding problems at the parent node.
Kleniati P-M, Adjiman CS, 2014, Branch-and-Sandwich: a deterministic global optimization algorithm for optimistic bilevel programming problems. Part II: Convergence analysis and numerical results, JOURNAL OF GLOBAL OPTIMIZATION, Vol: 60, Pages: 459-481, ISSN: 0925-5001
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- Citations: 24
Dufal S, Papaioannou V, Sadeqzadeh M, et al., 2014, Prediction of Thermodynamic Properties and Phase Behavior of Fluids and Mixtures with the SAFT-γ Mie Group-Contribution Equation of State, JOURNAL OF CHEMICAL AND ENGINEERING DATA, Vol: 59, Pages: 3272-3288, ISSN: 0021-9568
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- Citations: 94
Vasileiadis M, Pantelides CC, Adjiman CS, 2014, Prediction of the crystal structures of axitinib, a polymorphic pharmaceutical molecule, Chemical Engineering Science, Vol: 121, Pages: 60-76, ISSN: 0009-2509
Organic molecules can crystallize in multiple structures or polymorphs, yielding crystals with very different physical and mechanical properties. The prediction of the polymorphs that may appear in nature is a challenge with great potential benefits for the development of new products and processes. A multistage crystal structure prediction (CSP) methodology is applied to axitinib, a pharmaceutical molecule with significant polymorphism arising from molecular flexibility. The CSP study is focused on those polymorphs with one molecule in the asymmetric unit. The approach successfully identifies all four known polymorphs within this class, as well as a large number of other low-energy structures. The important role of conformational flexibility is highlighted. The performance of the approach is discussed in terms of both the quality of the results and various algorithmic and computational aspects, and some key priorities for further work in this area are identified.
Rhazaoui K, Cai Q, Adjiman CS, et al., 2014, Towards the 3D modeling of the effective conductivity of solid oxide fuel cell electrodes - II. Computational parameters, CHEMICAL ENGINEERING SCIENCE, Vol: 116, Pages: 781-792, ISSN: 0009-2509
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- Citations: 9
Schreckenberg JMA, Dufal S, Haslam AJ, et al., 2014, Modelling of the thermodynamic and solvation properties of electrolyte solutions with the statistical associating fluid theory for potentials of variable range, Molecular Physics: An International Journal at the Interface Between Chemistry and Physics, Vol: 112, Pages: 2339-2364, ISSN: 0026-8976
An improved formulation of the extension of the statistical associating fluid theory for potentials of variable range to electrolytes (SAFT-VRE) is presented, incorporating a representation for the dielectric constant of the solution that takes into account the temperature, density and composition of the solvent. The proposed approach provides an excellent correlation of the dielectric-constant data available for a number of solvents including water, representative alcohols and carbon dioxide, and it is shown that the methodology can be used to treat mixed-solvent electrolyte solutions. Models for strong electrolytes of the metal-halide family are considered here. The salts are treated as fully dissociated and ion-specific interaction parameters are presented. Vapour pressure, density, and mean ionic activity coefficient data are used to determine the ion–ion and solvent–ion parameters, and mixed-salt electrolyte solutions (brines) are then treated predictively. We find that the resulting intermolecular potential models follow physical trends in terms of energies and ion sizes with a close relationship observed with well-established ionic diameters. A good description is obtained for the densities, mean ionic activity coefficients, and vapour pressures of the electrolyte solutions studied. The theory is also seen to provide excellent predictions of the osmotic coefficient and of the depression of the freezing temperature, and provides a qualitative estimate of the solvation free energy. The vapour pressure of aqueous brines is predicted accurately, as is the density of these solutions, although not at the highest pressures considered. Calculations for the vapour–liquid and liquid–liquid equilibria of salts in water+methanol and water+n-butan-1-ol are presented. In addition, it is shown that the salting-out of carbon dioxide in sodium chloride solutions is captured well using a predictive model.
Diamanti A, Adjiman C, Galindo A, 2014, Systematic study of the accuracy of Conventional Transition State Theory in the calculations of the kinetics of a gas-phase reaction, 248th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Siougkrou E, Galindo A, Adjiman CS, 2014, On the optimal design of gas-expanded liquids based on process performance, CHEMICAL ENGINEERING SCIENCE, Vol: 115, Pages: 19-30, ISSN: 0009-2509
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- Citations: 28
Papaioannou V, Adjiman CS, Jackson G, et al., 2014, Group Contribution Methodologies for the Prediction of Thermodynamic Properties and Phase Behavior in Mixtures, Process Systems Engineering, Pages: 135-172, ISBN: 9783527316847
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- Citations: 1
Pereira FE, Keskes E, Galindo A, et al., 2014, Integrated Design of CO<inf>2</inf> Capture Processes from Natural Gas, Process Systems Engineering, Pages: 231-248, ISBN: 9783527316847
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- Citations: 2
Adjiman CS, Galindo A, 2014, Preface: Volume 6: Molecular Systems Engineering, ISBN: 9783527316847
Strübing H, Konstantinidis S, Karamertzanis PG, et al., 2014, Computer-Aided Methodologies for the Design of Reaction Solvents, Process Systems Engineering, Pages: 267-305, ISBN: 9783527316847
Kazantsev AV, Karamertzanis PG, Pantelides CC, et al., 2014, CrystalOptimizer: An Efficient Algorithm for Lattice Energy Minimization of Organic Crystals Using Isolated-Molecule Quantum Mechanical Calculations, Process Systems Engineering, Pages: 1-42, ISBN: 9783527316847
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- Citations: 1
Papaioannou V, Lafitte T, Avendano C, et al., 2014, Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments, Journal of Chemical Physics, Vol: 140, ISSN: 0021-9606
A generalization of the recent version of the statistical associating fluid theory for variable range Mie potentials [Lafitte et al., J. Chem. Phys. 139, 154504 (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH3, CH2, and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative propert
Papadopoulos AI, Badr S, Chremos A, et al., 2014, On the efficient screening and selection of post-combustion C02 capture solvents
Gu B, Adjiman C, Xu Y, 2014, An integrated model of a spiral-wound membrane module for reverse osmosis considering the effects of winding and spacers, Pages: 566-568
Papadopoulos AI, Badr S, Chremos A, et al., 2014, Molecular design of optimum CO<inf>2</inf> capture solvents: From conceptual screening to SAFT-based validation, Pages: 382-383
The wide adoption of chemical absorption/desorption systems for post-combustion CO2 capture in industry is currently challenged by the high energy penalty in solvent regeneration and the environmental impacts associated with solvents and their derivatives. Intense research efforts reported in recent years are predominantly based on lab and pilot-scale experiments to select solvents which may potentially improve the overall performance of absorption/desorption CO2 capture. However, this is very challenging due to a) the highly non-ideal solvent-CO2-water chemical interactions, b) the countless combinations of potential capture solvent and blend candidates and c) the need for combined consideration of numerous thermodynamic, kinetic and sustainability properties as performance criteria prior to selecting solvents with optimum capture features. Computer-aided molecular design methods (CAMD) can help address these challenges and have been successful in supporting the synthesis of molecules with desired physical, chemical and environmental properties in non-CO2 separations [1]. Despite extensive developments in CAMD methods, few recent works have reported their utilization in the design of CO2 capture solvents or mixtures for chemical and physical absorption using the Statistical Associating Fluid Theory with potentials of Variable Range (SAFT-VR) [2, 3] and for physical absorption using the Perturbed Chain Polar Statistical Associating Fluid Theory (PCP-SAFT) [4]. While these approaches enable an accurate and reliable determination of solvent-process vapour-liquid equilibria, the set of few solvents screened to date will be further expanded as research efforts extend the rigorous predictive capabilities of SAFT-based models towards additional molecular structures. On the other hand, few CAMD approaches have also been reported [5, 6, 7] that use less accurate, but well-established group contribution methods to screen a much wider set of molecular structures by approximat
Papadopoulos AI, Badr S, Chremos A, et al., 2014, Efficient Screening and Selection of Post-Combustion CO2 Capture Solvents, 17TH INTERNATIONAL CONFERENCE ON PROCESS INTEGRATION, MODELLING AND OPTIMISATION FOR ENERGY SAVING AND POLLUTION REDUCTION (PRES'14), Vol: 39, Pages: 211-216, ISSN: 2283-9216
We develop an approach for the screening and selection of post combustion CO2 capture solvents usingas the performance criteria the molecular and mixture properties associated with thermodynamics,reactivity and sustainability. The proposed approach involves a fast screening stage in which numeroussolvents are evaluated based on the simultaneous consideration of pure component properties. Severalproperties are specifically selected to represent the effects of molecular chemistry on the capture process.A few high-performing solvents are further evaluated using predictive models accounting for the very non-ideal mixture behaviour. The prediction of pure component properties is supported by standard groupcontribution models. The solvent-water-CO2 interactions are represented within the SAFT-VR and SAFT-γ equations of state to predict accurately the mixture vapour-liquid equilibrium behaviour. The proposed developments are tested successfully on a dataset consisting of 126 potential solvent candidates.
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