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Damage to porous materials in heritage buildings caused by salt mixture crystallization is driven by the surrounding environmental conditions. To understand the crystallization behavior of a mixed salt solution as a function of changing climatic conditions (i.e., relative humidity and temperature), excluding factors such as the internal pore structure, the thermodynamic model ECOS/RUNSALT is the only freeware available that requires simple input and includes the most relevant ions for heritage buildings and solids. We suggest the use of specific terminology and describe how to use the model and how to interpret the output, with emphasis on key limitations for which solutions are provided. When used correctly, the model output can be trusted, specifically when it is used to inform preventive conservation (e.g., environmental conditions in which salt crystallization cycles should not occur). However, salt mixture kinetics and the internal pore structure remain crucial parameters that are not considered in the model. These aspects need further attention to develop a better understanding and correctly model salt damage in relation to climatic changes.

The goal of this work is to accurately measure the viscosity of an industrial secondary copper smelting slag. Established literature commonly performed such measurements in non-inert labware, such as alumina. Despite the fact that the dissolution of alumina into the slag was addressed as a source for errors, a comprehensive analysis of how this interaction affects the measurement reliability is hitherto lacking. Furthermore, the type of dissolution (direct or indirect) will influence the interaction kinetics. This work aims to verify a possible relation between the dissolution and viscosity measurement reliability. For this purpose, the infiltration depth during and time stability of four different slag ( $${\text{{PbO}-{SiO}}}_{2}{\text {{-CaO}-{Al}}}_{2}{\text {{O}}_{3}}{\text {{-ZnO}-{Fe}}}_{2}{\text {O}}_{3}$$ ) viscosity measurements were analyzed. Both in-situ viscosity measurements and post mortem SEM images of the interface were therefore analyzed. It was observed that a multiphase interfacial layer was formed upon alumina dissolution. This layer consisted of a spinel intermediate layer and an enclosed interfacial slag. EDX measurements confirmed the difference between the latter layer’s composition and the bulk slag. Samples with a high interfacial slag viscosity yielded a dense spinel layer. As a result, alumina dissolved indirectly and more reliable viscosity measurements were obtained that were more stable over time. While samples with a low interfacial slag viscosity yielded a discontinuous spinel layer and therefore alumina could dissolve fast into the bulk slag, resulting in more unreliable viscosity measurements that varied over time.

Phase equilibria modeling is a powerful petrological tool to address both forward and inverse geological problems over a broad range of crustal and upper mantle conditions of pressure (P), temperature (T), composition (X), and redox (fO2). The development of thermodynamic databases, relatively realistic activity−composition (a−X) relations for solids, melts and fluids, pressure-volume-temperature (PVT) equations of state (EOS), and efficient numerical algorithms represent an inflection point in our ability to understand the nexus between tectonics and petrogenesis. While developed—and typically applied in isolation—by either metamorphic or igneous petrologists, some of the published thermodynamic models have overlapping P-T-X calibration ranges, which enables comparisons of model outcomes for similar conditions within the range of applicability. In this paper, we systematically compare the results of two such models that are routinely used for calculating phase equilibria in melt-bearing systems: rhyolite-MELTS (Gualda et al. 2012; Ghiorso and Gualda 2015) and the metabasite set of Green et al. (2016) using the thermodynamic database ds62 (Holland and Powell 2011) (hereafter denoted as “HPx-mb16”). We selected a N-MORB composition and modeled closed system equilibrium phase relations as a function of temperature at 0.25 and 1 GPa for N-MORB with 0.5 and 4 wt% H2O. Our results show that phase relations exhibit some key differences that, in some instances, impact geological inferences. For example, clinopyroxene and plagioclase stabilities are expanded to higher temperatures in HPx-mb16 compared to predictions from rhyolite-MELTS. Orthopyroxene and olivine are stable in greater proportions and at wider temperature ranges in rhyolite-MELTS compared to HPx-mb16. Importantly, HPx-mb16 predicts amphibole in all runs presented here, whereas amphibole is only predicted at high-P–high-H2O (1 GPa and 4 wt% H2O) in rhyolite-MELTS, and in lesser amounts. Garnet stability is systematically expanded at higher temperatures, and the proportion is greater in rhyolite-MELTS. In addition to phase assemblage differences, phase compositions may differ. For example, plagioclase anorthite content is systematically higher in HPx-mb16 (for the same set of conditions), whereas garnet Mg# is higher in rhyolite-MELTS. Calculated amphibole compositions are substantially different between the two models as well. Liquid compositions also show important differences. High-T liquids are generally similar in SiO2 contents but diverge at lower temperatures; in these cases, HPx-mb16 liquids are SiO2-depleted compared to those produced by rhyolite-MELTS. Liquids are also systematically and substantially more mafic in HPx-mb16, and alumina and the alkali concentrations are relatively different and show different trends as a function of temperature at constant pressure. Overall, liquid compositions show the greatest differences near the solidus. Differences in modal abundances of phases and liquid compositions influence liquid trace-element signatures, and these differences can affect geological interpretations. Finally, a comparison between melting experiments of basaltic bulk composition and both thermodynamic models shows that rhyolite-MELTS better reproduces the higher temperature experiments, whereas HPx-mb16 better reproduces the lower temperature experiments. We discuss these and other similarities and differences to highlight the strengths and limitations of each model and to recognize that modeling results have important implications for interpretations of geologic processes. We recognize that our results are informed by a small subset of calculations over a limited range of conditions—but encourage further comparisons over a wider range of conditions and compositions.

Antimony is attracting interest as an addition to Pb-free solders to improve thermal cycling performance in harsher conditions. Here, we investigate microstructure evolution and failure in harsh accelerated thermal cycling (ATC) of a Sn-3.8Ag-0.9Cu solder with 5.5 wt.% antimony as the major addition in two ball grid array (BGA) packages. SbSn particles are shown to precipitate on both Cu6Sn5 and as cuboids in β-Sn, with reproducible orientation relationships and a good lattice match. Similar to Sn-Ag-Cu solders, the microstructure and damage evolution were generally localised in the β-Sn near the component side where localised β-Sn misorientations and subgrains, accelerated SbSn and Ag3Sn particle coarsening, and β-Sn recrystallisation occurred. Cracks grew along the network of recrystallised grain boundaries to failure. The improved ATC performance is mostly attributed to SbSn solid-state precipitation within β-Sn dendrites, which supplements the Ag3Sn that formed in a eutectic reaction between β-Sn dendrites, providing populations of strengthening particles in both the dendritic and eutectic β-Sn.

Photocurable polymers are used ubiquitously in 3D printing, coatings, adhesives, and composite fillers. In the present work, the free radical polymerization of photocurable compounds is studied using reactive classical molecular dynamics combined with a dynamical approach of the nonequilibrium molecular dynamics (D-NEMD). Different concentrations of radicals and reaction velocities are considered. The mechanical properties of the polymer resulting from 1,6-hexanediol dimethacrylate systems are characterized in terms of viscosity, diffusion constant, and activation energy, whereas the topological ones through the number of cycles (polymer loops) and cyclomatic complexity. Effects like volume shrinkage and delaying of the gel point for increasing monomer concentration are also predicted, as well as the stress-strain curve and Young's modulus. Combining ab initio, reactive molecular dynamics, and the D-NEMD method might lead to a novel and powerful tool to describe photopolymerization processes and to original routes to optimize additive manufacturing methods relying on photosensitive macromolecular systems.

The chemistry of erupted magmas provides a crucial window into the composition and structure of Earth's convecting mantle. However, magmatic evolution in the crust makes it challenging to reconstruct mantle properties from volcanic rocks in important but incompletely understood ways. Here we investigate how mantle-derived compositional variability in primary oceanic basalts determines their phase equilibria relations and the nature of the geochemical signals they record. By performing experiments on synthetic analogues of compositionally extreme primitive lavas from the Reykjanes Peninsula of Iceland at realistic magma storage conditions (300 MPa, 1140–1260 °C), we show that melts from enriched mantle domains retain higher melt fractions as they cool than those generated by melting of typical fertile lherzolite (i.e. they crystallise less mass over any interval of decreasing temperature). These melt fraction differences arise because plagioclase crystallisation is suppressed in Na- and H2O-rich but Ca- and Al-poor liquids derived from enriched source lithologies. Thus, compositional characteristics inherited from the mantle have a first-order control on the efficiency with which cooling basalts crystallise. This means that enriched melts will be more likely to survive crustal processing than depleted melts. Basalt chemistry will therefore be disproportionately influenced by melts from volumetrically minor enriched lithologies compared with melts from the upper mantle's most common lithology, lherzolite, systematically biasing basaltic records towards melts from recycled mantle sources. We combine our experimental observations from Iceland with thermodynamic simulations on mid-ocean ridge basalt compositions and show that mantle-derived variability in crystallisation efficiency can explain two enigmatic features of the global oceanic basalt record: firstly, the anomalous over-enrichment of incompatible elements during the differentiation of mid-ocean ridge basalts, which may reflect a progressive bias towards enriched compositions as differentiation proceeds; and secondly, the frequently documented cargoes of highly anorthitic plagioclase crystals carried by evolved and enriched liquids from which they cannot have crystallised. These crystals can now be understood as the solidified remnants of depleted, lherzolite-derived melts that have been entrained into melt mixtures from more enriched sources. Increases in the degree of enrichment of cumulate rocks sampled from progressively shallower horizons of the oceanic crust can also be interpreted in terms of enriched melts surviving crustal processing in preference to depleted melts.

The predictive simulation of molecular liquids requires potential energy surface (PES) models that are not only accurate but also computationally efficient enough to handle the large systems and long time scales required for reliable prediction of macroscopic properties. We present a new approach to the systematic approximation of the first-principles PES of molecular liquids using the GAP (Gaussian Approximation Potential) framework. The approach allows us to create potentials at several different levels of accuracy in reproducing the true PES and thus to determine the level of quantum chemistry that is necessary to accurately predict macroscopic properties. We test the approach by building a series of many-body potentials for liquid methane (CH4), which is difficult to model from first principles because its behavior is dominated by weak dispersion interactions with a significant many-body component. The increasing accuracy of the potentials in predicting the bulk density correlates with their fidelity to the true PES, whereas the trend with the empirical potentials tested is surprisingly the opposite. We conclude that an accurate, consistent prediction of its bulk density across wide ranges of temperature and pressure requires not only many-body dispersion but also quantum nuclear effects to be modeled accurately.

The solubility of water in liquid n-perfluorohexane and in an equimolar mixture of n-hexane + n-perfluorohexane is experimentally determined as a function of temperature. The solubility of water in the equimolar mixture is significantly higher than the average of the solubilities in the pure solvents suggesting, for the first time, that mixing hydrogenated and perfluorinated chains enhances the solubility of water. The solubility in the equimolar mixture of n-hexane + n-perfluorohexane is also determined theoretically with the SAFT-γ Mie group-contribution approach, allowing a direct quantitative estimate of how much the large deviations from ideality contribute to the solubility of water in the mixture. In addition, the SAFT-γ Mie approach is used to represent the solubility of water in a number of n-perfluoroalkylalkanes, covering a range of relative lengths of the hydrogenated and perfluorinated chains. The theory can be used to predict the relative extent of the solubility of water in the different solvents, in good agreement with the experimental data. This is accomplished by using a single parameter to describe the strong attractive interaction between water and the CH2CF2 group at the junction between the hydrogenated and perfluorinated segments, which is known to be responsible for the increased solubility of water in these substances.

Phosphorus has a detrimental effect on the quality of steel as it reduces its ductility and toughness. In order to ensure a good quality of the final product, the requirements for steel regarding the phosphorus content are very strict. Recently, it has been reported that the levels of phosphorus in iron ores are increasing due to a gradual shortage of low phosphorus iron ores. Thus, the phosphorus content of the hot metal charged into the BOF (Basic Oxygen Furnace) process will be increasing, which will sharpen the challenges associated with meeting the end phosphorus requirements. Steelmakers are therefore exploring the possibilities for refining high phosphorus iron ore and aim at developing solutions that ensure controlling the final phosphorus contents within the target range under those new circumstances. A detailed study of the thermodynamics of dephosphorization reaction at conditions relevant for the BOF process is necessary in order to point out the potential as well as the limitations of phosphorus removal for different starting conditions and blowing strategies. This is important for deriving the appropriate process solution, for example, in deciding whether a single or a double slag treatment is required, or for the development of innovative process technologies and new control methods. Even though the quaternary system CaO-FeOx-SiO2-P2O5 is the fundamental oxide system for low and high phosphorus refining processes, its thermochemical behavior remains unclear. Instead, it is common practice to reduce this system to its ternary sub-systems CaO-FeOx-SiO2 and CaO-FeOx-P2O5 when studying the thermochemical behavior of low and high phosphorus systems. However, the phase diagrams available in the literature do not always cover the total temperature range of the industrial process. In addition, the effect of the oxidation state of FeOx and that of minor oxides such as MgO or MnO on the phase boundaries of those ternary systems remains unclear. By means of carrying out extensive evaluations of the oxide systems relevant for both low and high phosphorus refining processes, this thesis aims at providing a deep understanding of the state of industrial slags in the composition, temperature, and p(O2) ranges relevant for the entire process. In addition, an assessment of the dephosphorization potential of industrial slags under those conditions is provided. The extent of phosphorus removal from the metal phase is controlled by the dephosphorization potential of the slag phase, which is generally believed to be a strong function of the composition and temperature of the relevant oxide system. A computational thermodynamics approach is used for the thermodynamic evaluations carried out in the present work, which involves coupling the newly developed thermodynamic database BOFdePhos to the software package FactSage TM. The non-ideal associate solution model is used for the description of the Gibbs energy of the liquid phase and the Compound Energy Formalism (CEF) for the description of the Gibbs energy of the solid solution phases while the solid stoichiometric compounds are treated with simple temperature-dependent Gibbs energy functions. This approach has been selected due to the fact that modeling approaches developed according to the CALPHAD (CALculation of PHAse Diagrams) method have a good capability for extrapolating from assessed binary and ternary sub-systems to higher-order systems. Thus, it is possible to generate new phase diagrams using experimental data from lower-order systems. The thermodynamic evaluation of the oxide system CaO-FeOx-SiO2-P2O5 and its ternary subsystems were carried out for the total composition, temperature, and p(O2) ranges relevant for the process. The results were used for the assessment of the state of industrial slags by means of the analysis of plant trial measurements. The assessments indicate that industrial slags are heterogeneous throughout the major part of the process and, in most cases, saturated with the solid C2S_C3P (2CaO.SiO2_3CaO.P2O5) phase. However, most phosphorus distribution approaches (Lp-approaches) reported in the literature were developed for purely liquid slags. Thus, a new Lp-approach has been developed in the present work, which considers the effect of the amount, type, and composition of the different slag phases. The type and amount of phases formed during the process are found to be highly sensitive to the composition, temperature, and oxidation state of FeOx. The risk involved with simplifying the oxide system to its main components, as well as with the non-consideration of the effect of p(O2) is underlined in this work. This work demonstrates how new methods and strategies for enhancing dephosphorization control can be developed based on a combination of thermodynamic, experimental, and industrial evaluations. Those methods include an implementation concept for the thermodynamic database into dynamic models, the specification of a new target slag region for achieving optimal dephosphorization results, as well as the development of a new BOF method for ensuring a flexible, yet accurate, control of the slag composition towards the target region. Dissertation, Universität Duisburg-Essen, 2021

Storing methane in clathrates is one of the most promising alternatives for transporting natural gas (NG) as it offers similar gas densities to liquefied and compressed NG while offering lower safety risks. However, the practical use of clathrates is limited given the extremely low temperatures and high pressures necessary to form these structures. Therefore, it has been suggested to confine clathrates in nanoporous materials, as this can facilitate clathrate's formation conditions while preserving its CH4 volumetric storage. Yet, the choice of nanoporous materials to be employed as the clathrate growing platform is still rather arbitrary. Herein, we tackle this challenge in a systematic way by computationally exploring the stability of clathrates confined in alkyl-grafted silica materials with different pore sizes, ligand densities and ligand types. Based on our findings, we are able to propose key design criteria for nanoporous materials favoring the stability of a neighbouring clathrate phase, namely large pore sizes, high ligand densities, and smooth pore walls. We hope that the atomistic insight provided in this work will guide and facilitate the development of new nanomaterials designed to promote the formation of clathrates., Unravelling structure–property relationships allowing clathrate stability on hydrophobized silica pores. Cyclic and medium-sized chain alkane ligands form suitable ligands for clathrate stabilization.

Ferromagnetic shape-memory CoNiGa alloys have attracted much scientific interest due to their potential alternative use as high-temperature shape-memory alloys, bearing a high prospect for actuation and damping applications at elevated temperatures. Yet, polycrystalline CoNiGa, due to strong orientation dependence of transformation strains, suffers from intergranular fracture. Here, two multi-grain CoNiGa samples were prepared by a novel hot extrusion process that can promote favourable grain-boundary orientation distribution and improve the material's mechanical behaviour. The samples were investigated by multiple methods and their micro structural, magnetic, and mechanical properties are reported. It is found that a post-extrusion solutionising heat treatment leads to the formation of a two-phase oligocrystalline homogeneous microstructure consisting of an austenitic parent B2 phase and gamma-CoNiGa precipitates. Reconstruction of the full 3D grain morphology revealed large, nearly spherical grains with no low-angle grain boundaries throughout the entire sample volume. The presence of gamma precipitation affects the transformation behaviour of the samples, by lowering the martensitic transformation temperature, while, in conjunction with the oligocrystalline microstructure, it improves the ductility. Controlling the composition of the B2 matrix, as well as the phase fraction of the gamma phase, is thus crucial for the optimal behaviour of the alloys. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

The structural and thermodynamic properties of Na+ - Cl- ion-pair association in water-CO2 binary mixtures in supercritical conditions for infinitely dilute solutions are studied using constrained molecular dynamics simulations over a wide range of compositions. It is found that solvation structure varies dramatically with the solvent composition. Contact ion pairs (CIPs) are found to be more stable than all other configurations as seen from the potentials of mean force (PMFs). PMFs of the NaCl ion pair in pure CO2 look almost like the pair potential between the ion pair. Stabilities of CIPs increase with increase in the mole fraction of CO2. An increment in the average number of hydrogen bonds with an increase in the mole fraction of H2O in the bulk as well as in the solvation shell of the ions is observed. Ion-pair association in aqueous CO2 mixtures in supercritical conditions is found to be endothermic and driven by entropy. Preferential solvation analysis shows that both Na+ and Cl- ions are preferentially solvated by water and even a small percentage of water in the mixture prevents CO2 molecules from entering the first solvation shell of ions due to the strong hydrophilicity of the ions. (C) 2018 Elsevier B.V. All rights reserved.

The prediction of the solubility of active pharmaceutical ingredients (APIs) is a significant challenge which is of importance in pharmaceutical applications and solvent selection. Here, we extend the table of group interactions (3 like interactions, 47 unlike interactions) of the SAFT- γ Mie group-contribution equation of state to model the phase behaviour and solubility of mefenamic acid, a nonsteroidal anti-inflammatory drug, in a range of solvents. In addition to mefenamic acid, we also consider its molecular synthons: benzoic acid and diphenylamine. New experimental solubility data are presented for the three molecules in a range of solvents, and three new SAFT- γ Mie functional groups are defined (aCCOOH, aCNHaC and CH 3 CO) and characterised, together with their interactions with solvent groups. Literature data for the vapour pressure, single-phase density, saturation density, vapourisation enthalpy, bubble temperature, dew temperature, and bubble pressure are used to characterise the new group interactions. Solubility data are used to characterise the new group-group interactions only if there are no other experimental data available. The transferability and predictive accuracy of the new models are assessed by comparing the theoretical predictions with the experimental solubility data. Our comparison includes alcohols, ketones, and esters as families of solvents and mixed-solvent solubility predictions.

Various changes in seismic structures across the mantle transition zone (MTZ) indicate that it may hamper thermal and chemical circulation. Here we show how thermal elevation of the postspinel phase transition at 660 km depth plus harzburgite segregation below this depth can project as narrow high-velocity anomalies in tomographic images of continuous thermochemical mantle upwellings. Model S40RTS features a narrow high-velocity anomaly of +0.8% near 660 km depth within the broad low-velocity structure beneath the Samoa hot spot. Our analyses indicate that elevation of the 660 phase boundary in a hot pyrolitic plume alone is insufficient to explain this anomaly. An additional effect of harzburgite enrichment is required and consistent with geodynamic simulations that predict compositional segregation in the MTZ, especially within thermochemical upwellings. The Samoa anomaly can be modeled with a 125–175°C excess temperature and a harzburgite enrichment below 660 of least 60% compared to a pyrolitic mantle.

Atomistic molecular dynamics simulations were carried out to obtain the diffusion coefficients of CO2 in n-hexane, n-decane, n-hexadecane, cyclohexane, and squalane at temperatures up to 423.15 K and pressures up to 65 MPa. Three popular models were used for the representation of hydrocarbons: the united atom TraPPE (TraPPE-UA), the all-atom OPLS, and an optimized version of OPLS, namely, L-OPLS. All models qualitatively reproduce the pressure dependence of the diffusion coefficient of CO2 in hydrocarbons measured recently, and L-OPLS was found to be the most accurate. Specifically for n-alkanes, L-OPLS also reproduced the measured viscosities and densities much more accurately than the original OPLS and TraPPE-UA models, indicating that the optimization of the torsional potential is crucial for the accurate description of transport properties of long chain molecules. The three force fields predict different microscopic properties such as the mean square radius of gyration for the n-alkane molecules and pair correlation functions for the CO2–n-alkane interactions. CO2 diffusion coefficients in all hydrocarbons studied are shown to deviate significantly from the Stokes–Einstein behavior.

We use a high-pressure semicontinuous batch electrochemical reactor with a tin-based cathode to demonstrate that it is possible to efficiently convert CO2 to formic acid (FA) in low-pH (i.e., pH < pKa) electrolyte solutions. The effects of CO2 pressure (up to 50 bar), bipolar membranes, and electrolyte (K2SO4) concentration on the current density (CD) and the Faraday efficiency (FE) of formic acid were investigated. The highest FE (?80%) of FA was achieved at a pressure of around 50 bar at a cell potential of 3.5 V and a CD of ?30 mA/cm2. To suppress the hydrogen evolution reaction (HER), the electrochemical reduction of CO2 in aqueous media is typically performed at alkaline conditions. The consequence of this is that products like formic acid, which has a pKa of 3.75, will almost completely dissociate into the formate form. The pH of the electrolyte solution has a strong influence not only on the electrochemical reduction process of CO2 but also on the downstream separation of (dilute) acid products like formic acid. The selection of separation processes depends on the dissociation state of the acids. A review of separation technologies for formic acid/formate removal from aqueous dilute streams is provided. By applying common separation heuristics, we have selected liquid-liquid extraction and electrodialysis for formic acid and formate separation, respectively. An economic evaluation of both separation processes shows that the formic acid route is more attractive than the formate one. These results urge for a better design of (1) CO2 electrocatalysts that can operate at low pH without affecting the selectivity of the desired products and (2) technologies for efficient separation of dilute products from (photo)electrochemical reactors.

We present a perturbation theory that combines the use of a third-order Barker–Henderson expansion of the Helmholtz energy with Miepotentials that include first- (Mie-FH1) and second-order (Mie-FH2) Feynman–Hibbs quantum corrections. The resulting equation of state, the statistical associating fluid theory for Mie potentials of variable range corrected for quantum effects (SAFT-VRQ-Mie), is compared to molecular simulations and is seen to reproduce the thermodynamic properties of generic Mie-FH1 and Mie-FH2 fluids accurately. SAFTVRQ Mie is exploited to obtain optimal parameters for the intermolecular potentials of neon, helium, deuterium, ortho-, para-, and normalhydrogen for the Mie-FH1 and Mie-FH2 formulations. For helium, hydrogen, and deuterium, the use of either the first- or second-order corrections yields significantly higher accuracy in the representation of supercritical densities, heat capacities, and speed of sounds when compared to classical Mie fluids, although the Mie-FH2 is slightly more accurate than Mie-FH1 for supercritical properties. The Mie-FH1 potential is recommended for most of the fluids since it yields a more accurate representation of the pure-component phase equilibria and extrapolates better to low temperatures. Notwithstanding, for helium, where the quantum effects are largest, we find that none of the potentials give an accurate representation of the entire phase envelope, and its thermodynamic properties are represented accurately only at temperatures above 20 K. Overall, supercritical heat capacities are well represented, with some deviations from experiments seen in the liquid phase region for helium and hydrogen. Equation of state and force fields for Feynman–Hibbs-corrected Mie fluids. I.Application to pure helium, neon, hydrogen, and deuterium

High-tech metals, including Ga, Ge and In, are critical for the performance of electrical and electronic equipment (EEE). None of these three metals exist in mineable levels in natural minerals, and thus their availability and production are dependent on the primary and secondary base metals (including Zn, Al and Cu) production. To secure the supply of high-tech metals in the future, their behavior, including distribution coefficients (L-Cu/s = [wt% M](in copper)/(wt% M)(in slag)), in primary and secondary processes need to be characterized. This study reports three series of copper-slag distribution experiments for Ga, Ge and In in simulated secondary copper smelting and refining process conditions (T = 1300 degrees C, pO(2) = 10(-9)-10(-5) atm) using a well-developed drop-quench technique followed by EPMA and LA-ICP-MS analyses. This study shows how an analytical technique more traditionally applied to the characterization of ores or minerals can also be applied to metallurgical process investigation. The LA-ICP-MS analysis was used for the first time for measuring the concentrations of these minor elements in metallurgical glasses, i.e., slags, and the results were compared to the geological literature. The distribution coefficient of indium increased as a function of decreasing oxygen partial pressure from 0.03 to 10, whereas the distribution coefficient of gallium was 0.1 at 10(-9) atm and decreased as the pO(2) increased. The concentrations of gallium in slags were between 0.4 and 0.6 wt% and germanium around 1 ppm. Germanium was vaporized almost entirely from the samples.

Understanding the molecular-scale behavior of fluids confined and sheared between solid surfaces is important for many applications, particularly tribology where this often governs the macroscopic frictional response. In this study, nonequilibrium molecular dynamics simulations are performed to investigate the effects of fluid and surface properties on the spatially resolved temperature and flow profiles, as well as friction. The severe pressure and shear rate conditions studied are representative of the elastohydrodynamic lubrication regime. In agreement with tribology experiments, flexible lubricant molecules give low friction, which increases linearly with logarithmic shear rate, while bulky traction fluids show higher friction, but a weaker shear rate dependence. Compared to lubricants, traction fluids show more significant shear heating and stronger shear localization. Models developed for macroscopic systems can be used to describe both the spatially resolved temperature profile shape and the mean film temperature rise. The thermal conductivity of the fluids increases with pressure and is significantly higher for lubricants compared to traction fluids, in agreement with experimental results. In a subset of simulations, the efficiency of the thermostat in one of the surfaces is reduced to represent surfaces with lower thermal conductivity. For these unsymmetrical systems, the flow and the temperature profiles become strongly asymmetric and some thermal slip can occur at the solid-fluid interface, despite the absence of velocity slip. The larger temperature rises and steeper velocity gradients in these cases lead to large reductions in friction, particularly at high pressure and shear rate.

Monte Carlo simulations are the foundational technique for predicting thermodynamic properties of open systems where the process of interest involves the exchange of particles. Thus, they have been used extensively to computationally evaluate the adsorption properties of nanoporous materials and are critical for the in silico identification of promising materials for a variety of gas storage and chemical separation applications. In this work we demonstrate that a well-known biasing technique, known as "flat-histogram" sampling, can be combined with temperature extrapolation of the free energy landscape to efficiently provide significantly more useful thermodynamic information than standard open ensemble MC simulations. Namely, we can accurately compute the isosteric heat of adsorption and number of particles adsorbed for various adsorbates over an extremely wide range of temperatures and pressures from a set of simulations at just one temperature. We extend this derivation of the temperature extrapolation to adsorbates with intramolecular degrees of freedom when Rosenbluth sampling is employed. Consequently, the working capacity and isosteric heat can be computed for any given combined temperature/pressure swing adsorption process for a large range of operating conditions with both rigid and deformable adsorbates. Continuous thermodynamic properties can be computed with this technique at very moderate computational cost, thereby providing a strong case for its application to the in silico identification of promising nanoporous adsorbents.

The SAFT-γ Mie group-contribution equation of state [ Papaioannou et al. J. Chem. Phys. 2014, 140, 054107 ] is used to develop a transferable coarse-grained (CG) force-field suitable for the molecular simulation of linear alkanes. A heterogroup model is fashioned at the resolution of three carbon atoms per bead in which different Mie (generalized Lennard-Jones) interactions are used to characterize the terminal (CH3-CH2-CH2-) and middle (-CH2-CH2-CH2-) beads. The force field is developed by combining the SAFT-γ CG top-down approach [ Avendaño et al. J. Phys. Chem. B 2011, 115, 11154 ], using experimental phase-equilibrium data for n-alkanes ranging from n-nonane to n-pentadecane to parametrize the intermolecular (nonbonded) bead-bead interactions, with a bottom-up approach relying on simulations based on the higher resolution TraPPE united-atom (UA) model [ Martin;, Siepmann J. Phys. Chem. B 1998, 102, 2569 ] to establish the intramolecular (bonded) interactions. The transferability of the SAFT-γ CG model is assessed from a detailed examination of the properties of linear alkanes ranging from n-hexane (n-C6H14) to n-octadecane (n-C18H38), including an additional evaluation of the reliability of the description for longer chains such as n-hexacontane (n-C60H122) and a prototypical linear polyethylene of moderate molecular weight (n-C900H1802). A variety of structural, thermodynamic, and transport properties are examined, including the pair distribution functions, vapor-liquid equilibria, interfacial tension, viscosity, and diffusivity. Particular focus is placed on the impact of incorporating intramolecular interactions on the accuracy, transferability, and representability of the CG model. The novel SAFT-γ CG force field is shown to provide a reliable description of the thermophysical properties of the n-alkanes, in most cases at a level comparable to the that obtained with higher resolution models.

Precise knowledge of vapor–liquid equilibrium (VLE) data of (CO2 + diluent) mixtures is crucial in the design and operation of carbon capture, transportation and storage processes. VLE measurements of the (CO2 + CO) system are reported along seven isotherms at temperatures ranging from just above the triple-point temperature of CO2 to 302.93 K and at pressures from the vapor pressure of pure CO2 to approximately 15 MPa, including near-critical mixture states for all isotherms. The measurements are associated with estimated standard uncertainties of 0.006 K for temperature, 0.009 MPa for pressure and 0.011x(1 − x) for mole fraction x. The new VLE data have been compared with two thermodynamic models: the Peng-Robinson equation of state (PR-EOS) and a multi-fluid Helmholtz-energy equation of state known as EOS-CG. The PR-EOS was used with a single temperature-dependent binary interaction parameter, which was fitted to the experimental data. In contrast, EOS-CG was used in a purely-predictive mode with no parameters fitted to the present results. While PR-EOS generally agrees fairly well with the experimental data, EOS-CG showed significantly better agreement, especially close to the critical point.

Experimental determination and theoretical predictions of the isothermal (344.15 K) mass densities and interfacial tensions for the sys tem carbon dioxide (CO2) with heptol (n - heptane + toluene) mixtures varying liquid volume fraction compositions of toluene (0, 25, 50, 75, 100 % v/v) and over the pressure range 0.1 to 8 MPa are reported. Measurements are carried out on a high - pressure dev ice that includes a vibrating tube densimeter and a pendant drop tensiometer. Theoretical modeling of mass densities phase equilibria and interfacial properties (i.e., interfacial tension and interfacial concentration profiles) are performed by employing t he Square Gradient Theory using an extension of the Statistical Associating Fluid Theory equation of state that accounts for ring fluids. The experimental bulk phase equilibrium densities and interfacial tensions obtained are in very good agreement with th e theoretical predictions. Although there are no previous experimental data of these mixtures at the conditions explored herein, the results follow the same trends observed from experimental data at other conditions. The combination of experimental and mod eling approaches provides a route to simultaneously predict phase equilibrium and interfacial properties within acceptable statistical deviations. For the systems and conditions studied here, we observe that the phase equilibrium of the mixtures display z eotropic vapor - liquid equilibria with positive deviations from ideal behavior. The mass bulk densities behave ordinarily whereas the interfacial tensions decrease as the pressure or liquid mole fraction of CO2 increases and/or the ratio toluene/heptane dec reases. The interfacial concentration along the interfacial region exhibits a remarkable high excess adsorption of CO2, which increases with pressure and it is larger in n - heptane than in toluene. Toluene does not exhibit any special adsorption activity wh ereas n - heptane displays surface activity only at low pressure in a very narrow range for the case of CO2 + (25% n - heptane + 75% toluene) mixture.

Global seismic discontinuities near 410 and 660 km depth in Earth's mantle are expressions of solid-state phase transitions. These transitions modulate thermal and material fluxes across the mantle and variations in their depth are often attributed to temperature anomalies. Here we use novel seismic array analysis of SS waves reflecting off the 410 and 660 below the Hawaiian hotspot. We find amplitude-distance trends in reflectivity that imply lateral variations in wavespeed and density contrasts across 660 for which thermodynamic modeling precludes a thermal origin. No such variations are found along the 410. The inferred 660 contrasts can be explained by mantle composition varying from average (pyrolitic) mantle beneath Hawaii to a mixture with more melt-depleted harzburgite southeast of the hotspot. Such compositional segregation was predicted, from petrological and numerical convection studies, to occur near hot deep mantle upwellings like the one often invoked to cause volcanic activity on Hawaii., Simons Foundation, National Science Foundation (U.S.). Division of Mathematical Sciences (1559587), Natural Environment Research Council (Great Britain) (NE/J008028/1), Royal Society (Great Britain) (Fellowship)

International audience; The E-PPR78 model is a predictive version of the widely used Peng-Robinson equation of state in which the binary interaction parameters are estimated by a group-contribution method. With the 24 groups available before the writing of this paper, such a model could be used to predict fluid phase equilibrium of systems containing hydrocarbons, permanent gases (CO2, N-2, H2S, H-2, CO, He, and Ar), mercaptans, alkenes, and water. During the process of the Carbon dioxide Capture and Storage (CCS), it is often necessary to know thermodynamic properties of mixtures containing carbon dioxide, water, hydrocarbons, and trace gases, such as nitrogen, argon, hydrogen, carbon monoxide, sulfur dioxide, oxygen, or nitric oxide. Basically, except sulfur dioxide, oxygen, and nitric oxide, most components encountered in systems regarding CCS processes could be modeled with the E-PPR78 model. So in order to predict the phase behavior and estimate energetic properties (e.g., enthalpy or heat capacity changes on mixing) of such systems, the applicability range of the E-PPR78 model is extended through the addition of three new groups: "SO2," "O-2," and "NO."

Molecular simulations were used to compute the equilibrium concentrations of the different species in CO2/monoethanolamine solutions for different CO2 loadings. Simulations were performed in the Reaction Ensemble using the continuous fractional component Monte Carlo method at temperatures of 293, 333, and 353 K. The resulting computed equilibrium concentrations are in excellent agreement with experimental data. The effect of different reaction pathways was investigated. For a complete understanding of the equilibrium speciation, it is essential to take all elementary reactions into account because considering only the overall reaction of CO2 with MEA is insufficient. The effects of electrostatics and intermolecular van der Waals interactions were also studied, clearly showing that solvation of reactants and products is essential for the reaction. The Reaction Ensemble Monte Carlo using the continuous fractional component method opens the possibility of investigating the effects of the solvent on CO2 chemisorption by eliminating the need to study different reaction pathways and concentrate only on the thermodynamics of the system.

International audience; The strongest evidence to support the classical plume hypothesis comes from seismic imaging of the mantle beneath hot spots. However, imaging results are often ambiguous and it is questionable whether narrow plume tails can be detected by present-day seismological techniques. Here we carry out synthetic tomography experiments based on spectral element method simulations of seismic waves with period T > 10 s propagating through geodynamically derived plume structures. We vary the source-receiver geometry in order to explore the conditions under which lower mantle plume tails may be detected seismically. We determine that wide-aperture (4,000–6,000 km) networks with dense station coverage (

A coarse-grained (CG) model for atactic polystyrene is presented and studied with classical molecular-dynamics simulations. The interactions between the CG segments are described by Mie potentials, with parameters obtained from a top-down approach using the SAFT-γ methodology. The model is developed by taking a CG model for linear-chain-like backbones with parameters corresponding to those of an alkane and decorating it with side branches with parameters from a force field of toluene, which incorporate an “aromatic-like” nature. The model is validated by comparison with the properties of monodisperse melts, including the effect of temperature and pressure on density, as well as structural properties (the radius of gyration and end-to-end distance as functions of chain length). The model is employed within large-scale simulations that describe the temperature–composition fluid-phase behavior of binary mixtures of polystyrene in n-hexane and n-heptane. A single temperature-independent unlike interaction energy parameter is employed for each solvent to reproduce experimental solubility behavior; this is sufficient for the quantitative prediction of both upper and lower critical solution points and the transition to the characteristic “hourglass” phase behavior for these systems.

NASA’s MESSENGER spacecraft has revealed geochemical diversity across Mercury’s volcanic crust. Near-infrared to ultraviolet spectra and images have provided evidence for the Fe2+-poor nature of silicate minerals, magnesium sulfide minerals in hollows and a darkening component attributed to graphite, but existing spectral data is insufficient to build a mineralogical map for the planet. Here we investigate the mineralogical variability of silicates in Mercury’s crust using crystallization experiments on magmas with compositions and under reducing conditions expected for Mercury. We find a common crystallization sequence consisting of olivine, plagioclase, pyroxenes and tridymite for all magmas tested. Depending on the cooling rate, we suggest that lavas on Mercury are either fully crystallized or made of a glassy matrix with phenocrysts. Combining the experimental results with geochemical mapping, we can identify several mineralogical provinces: the Northern Volcanic Plains and Smooth Plains, dominated by plagioclase, the High-Mg province, strongly dominated by forsterite, and the Intermediate Plains, comprised of forsterite, plagioclase and enstatite. This implies a temporal evolution of the mineralogy from the oldest lavas, dominated by mafic minerals, to the youngest lavas, dominated by plagioclase, consistent with progressive shallowing and decreasing degree of mantle melting over time. The MESSENGER spacecraft has revealed geochemical diversity across Mercury’s surface. Magma crystallization experiments suggest a crustal mineralogy consistent with a transition towards shallower and cooler mantle melting conditions.

The solubilities of d-glucose, d-arabinose, d-xylose, d-fructose, d-mannose, and sucrose in methanol and methanol–water mixtures (

A naturally occurring aromatic organic compound, p-cymene, finds applications as reaction intermediate, solvent in production of pharmaceuticals, fragrances, and fine chemicals. The experimental vapor liquid equilibria (VLE) data p-cymene, is available at pressures up to 537.4 kPa. In this study, the thermodynamic properties of p-cymene are determined using structure property correlations combined with equations of state (EoS) and molecular simulation techniques. Two molecular simulation techniques, Gibbs ensemble Monte Carlo (GEMC) and grand canoncial transition matrix Monte Carlo (GC-TMMC) have been employed for prediction of VLE. The estimates of properties, including vapor pressures, heats of vaporization, coexistence densities, and critical properties have been compared withavailable experimental data. The thermodynamic properties predicted by molecular simulations and also that obtained from Peng-robinson (PR) and volume translated Peng-Robinson (VTPR) EoS are generally, in broad agreement with the experimental data. Furter, GEMC results for coexistence densities and saturation vapor pressures are compared with that from GC-TMMC technique.

Isobaric vapor-liquid equilibrium (VLE) data have been measured for the binary system 2,2'-oxybis[propane] + 2,5-Dimethylfuran at 50, 75, and 94 kPa and over the temperature range 321-364 K using a vapor-liquid equilibrium still with circulation of both phases. Atmospheric surface tension (ST) data have been also determined at 283.15 and 330.15 K using a maximum bubble pressure tensiometer. Experimental results show that the mixture is zeotropic and exhibits slight positive deviation from ideal behavior over the experimental range. Surface tensions, in turn, exhibit negative deviation from the linear behavior. For each isothermal condition, it is observed that the surface tension decreases as the mole fraction of 2,2'-oxybis[propane] increases, whereas at a fixed mole fraction, the surface tension decreases as the temperature increases. The VLE data of the binary mixture satisfy the Fredenlund's consistency test, and the dependence of ST on mole fraction was satisfactorily smoothed using the Redlich-Kister equation. The experimental VLE and ST data were accurately described by applying the square gradient theory to the Cubic-Plus-Association equation of state. This theoretical model was also applied to describe the surface activity of species along the interfacial region, from which it is possible to conclude that only the 2,2'-oxybis[propane] presents an interfacial accumulation which decreases as the concentration of DIPE or temperature increases. (C) 2013 Elsevier B.V. All rights reserved.

Novel filled skutterudites BayNi4Sb12−xSnx (ymax = 0.93) have been prepared by arc melting followed by annealing at 250, 350 and 450 °C up to 30 days in vacuum-sealed quartz vials. Extension of the homogeneity region, solidus temperatures and structural investigations were performed for the skutterudite phase in the ternary Ni–Sn–Sb and in the quaternary Ba–Ni–Sb–Sn systems. Phase equilibria in the Ni–Sn–Sb system at 450 °C were established by means of Electron Probe Microanalysis (EPMA) and X-ray Powder Diffraction (XPD). With rather small cages Ni4(Sb,Sn)12, the Ba–Ni–Sn–Sb skutterudite system is perfectly suited to study the influence of filler atoms on the phonon thermal conductivity. Single-phase samples with the composition Ni4Sb8.2Sn3.8, Ba0.42Ni4Sb8.2Sn3.8 and Ba0.92Ni4Sb6.7Sn5.3 were used to measure their physical properties, i.e. temperature dependent electrical resistivity, Seebeck coefficient and thermal conductivity. The resistivity data demonstrate a crossover from metallic to semiconducting behaviour. The corresponding gap width was extracted from the maxima in the Seebeck coefficient data as a function of temperature. Single crystal X-ray structure analyses at 100, 200 and 300 K revealed the thermal expansion coefficients as well as Einstein and Debye temperatures for Ba0.73Ni4Sb8.1Sn3.9 and Ba0.95Ni4Sb6.1Sn5.9. These data were in accordance with the Debye temperatures obtained from the specific heat (4.4 K < T < 140 K) and Mössbauer spectroscopy (10 K < T < 290 K). Rather small atom displacement parameters for the Ba filler atoms indicate a severe reduction in the “rattling behaviour” consistent with the high levels of lattice thermal conductivity. The elastic moduli, collected from Resonant Ultrasonic Spectroscopy ranged from 100 GPa for Ni4Sb8.2Sn3.8 to 116 GPa for Ba0.92Ni4Sb6.7Sn5.3. The thermal expansion coefficients were 11.8 × 10−6 K−1 for Ni4Sb8.2Sn3.8 and 13.8 × 10−6 K−1 for Ba0.92Ni4Sb6.7Sn5.3. The room temperature Vickers hardness values vary within the range from 2.6 GPa to 4.7 GPa. Severe plastic deformation via high-pressure torsion was used to introduce nanostructuring; however, the physical properties before and after HPT showed no significant effect on the materials thermoelectric behaviour.

Here, we present a simple method for optimizing the fitting of molecular parameters involving vapor-liquid equilibria (VLE) and selected second-order thermodynamic properties and experimental data. The procedure is applied, as an example to the soft Statistical Associating Fluid Theory (soft-SAFT) equation of state. The method involves the introduction and testing of coupling factors ranging from 0 (only one selected derivative property) to 1 (only VLE), to change the weight of one set of properties over the other in the fitting procedure; this allows one to assess the role of derivative properties in the robustness of the parameters and molecular model. The technique is illustrated by calculating a large number of thermodynamic properties of different compounds: the n-alkanes, n-perfluoroalkanes, and 1-alkanols families, and water, as representative of different types of molecular interactions, and in a wide range of thermodynamic conditions. The most relevant thermodynamic properties to be included in the parameters fitting, the weight they should have in the regression procedure, and the influence of association are discussed in detail. It has been found that the use of just VLE data in the fitting procedure for regular nonassociating compounds, such as n-alkanes or perfluoroalkanes, is enough to provide good predictions of derivative properties. The use of derivative properties helped in identifying the best fitting strategy for the perfluoroalkanes family, as some limitations of the original parameters showed up when used for estimating the derivative properties. In contrast, association plays a major role in derivative properties of associating compounds such as alkanols and water. A coupling factor of 0.5 (equal weight of derivative property coupled with VLE data to fit the molecular parameters) is required to regress robust pure compound parameters that are able to simultaneously describe vapor pressures, phase densities, and derivative properties for 1-alkanols and water. The method presented here is robust, simple, and straightforward to implement; since it is not equation-dependent, it can be transferred to any other equation, providing robust molecular parameters for global equations.

The society and industry commitment to progressively reduce Green House Gases (GHGs) emissions forged important challenges that conventional gas separation processes are unable to overcome. Ionic liquids (ILs) have been attracting an outstanding attention during the last decade as a promising class of viable solvents to capture pollutants and for gas separation processes. Being the IL-based membranes gas separation controlled by the gas solubility in the IL rather than by its diffusivity, the solubility of gases in ILs stands as highly relevant input for their application in liquid membranes. As part of a continuing effort to develop an IL based process for high pressure capture of GHGs, the phase equilibria of nitrous oxide (N2O), methane (CH4) and nitrogen (N-2) were investigated in this work. Experimental gas-liquid equilibrium data for N2O, CH4 and N-2 in [C4C1 im][N(CN)(2)] were determined in the (293 to 363) K temperature range, for pressures up to 70 MPa and gas mole fractions up to 35 %. Unfavorable interactions towards the studied gases, with positive deviations to ideality, were observed for all the studied gases, placing the studied IL among those with the lowest selectivities reported. The observed behavior highlights that a delicate balance between the solvent polarity and its molar volume must be ascertained when a highly selective solvent for N-2 or CH4 separation is envisaged. The soft-SAFT EoS successfully described the high pressure phase behavior data using the molecular model and parameters sets reported in previous works. A good description of the binary systems studied, including the small CH4 temperature dependency and the N-2 reverse temperature dependency on the solubility were achieved using just one binary interaction parameter. This reinforces the use of soft-SAFT as an accurate model to describe the behavior of gases in ILs for different applications. (C) 2015 Elsevier B.V. All rights reserved.

International audience; In 2008, the PPR78 model (Predictive Peng-Robinson 1978) was extended to mercaptan-containing systems by adding the sulfhydryl group (-SH). that is, by determining the values of the group-interaction parameters between the group -SH and the fourteen other groups already present in the PPR78 model. Unfortunately, due to a lack of experimental data reported in the open literature, it was not possible to characterize interactions between the group -SH and the three groups: ethane, CO2 and N-2. Very recently, vapor-liquid equilibrium data for three binary systems containing methanethiol and respectively methane, nitrogen and carbon dioxide were however measured. It was thus decided to use these data to estimate two of the missing group-interaction parameters (-SH/CO2 and -SH/N-2). For such systems, deviations observed with the PPR78 model are compared to those obtained with the CPA equation of state.

In this paper the experimental setup of a new apparatus able to provide the critical properties of pure components and mixtures using either a dynamic or a static method is described. Critical temperatures ( T c ) and critical pressures ( P c ) of pure components ( n -pentane, n -heptane and n -decane) and critical loci of three binary mixtures ( n -pentane + n -heptane, n -pentane + n -decane and n -heptane + n -decane) are investigated using the dynamic method. For the system n -pentane + n -heptane, the results obtained with the dynamic method are compared with those obtained with the static method. The critical points are visually determined by observing the critical opalescence and the simultaneous disappearance and reappearance of the meniscus in the middle of the view cell which withstands operations up to 673 K and 20 MPa. The experimental critical data are compared with success to literature database and with their prediction from the PPR78 thermodynamic model.

One of the most promising renewable fuels proposed as an alternative to fossil diesel is biodiesel. The competitive potential of biodiesel is limited by the price of vegetable oils, which strongly influences the final price of this biofuel. On the other hand, extensive use of vegetable oils may cause other significant problems such as starvation in developing countries. Appropriately planning and designing the whole production process, from the seed to the biodiesel end-product, is essential to contain the influence of energy inefficiencies on the high price of the end-product. The present study reviews the technologies currently used in the production of biodiesel. We first discuss the technologies for extracting the vegetable oil from the seed, and its subsequent refining and conversion into biodiesel. This study focuses on the characteristics of the production processes currently used in the sector, illustrating the technological options and emphasizing the drawbacks of certain practices and the best choices available. The vegetable oils tend to be processed using procedures that are well established, but oriented more towards obtaining products suitable for the foodstuffs industry, and that consequently use technologies that are sometimes excessive for energetic purposes. The processes for extracting the vegetable oil from the seed generally include a set of steps, the complexity of which depends on the raw material. Basically, the two extraction technologies involved rely on the use of pressure or solvents. In practice, the two systems are often combined. Using the vegetable oils as a source of energy makes some of these steps superfluous and enables technologies to be used that would be unsuitable for foodstuffs production. This study focuses on feasible technological improvements that would give rise to oil that is still suitable for use as a source of energy, but at a lower cost. The refined vegetable oil can subsequently be converted into biodiesel by means of a great variety of technologies, many of which are still not suitable for applications on an industrial scale. The solution that has met with the greatest favor is homogeneous alkaline transesterification with KOH and methanol. Even when dealing with this type of conversion alone, it is impossible to establish a universal schema to describe the conversion or purification stages because there are numerous possible different solutions. When we then look more closely at the state of the art in industrial biodiesel production plants, we encounter the potential problems introduced by the type and characteristics of the original raw material. Comparing some of the reference solutions that have inspired numerous installations, a sensitivity analysis is conducted on the main elements involved in the process, focusing on their behavior in different working conditions to obtain products with the characteristics required by the international standards (EN 14214:2008, ASTM D 6751 07b). (C) 2011 Elsevier Ltd. All rights reserved.