Examinando por Autor "Suárez, Inmaculada"

Mostrando 1 - 12 de 12

Acidity reduction using ionic liquids: Extraction, kinetic, and theoretical study
(Elsevier, 2023-07-15) Arenas-Fernández, Plácido; Aguilar-Galindo, Fernando; Suárez, Inmaculada; Coto, Baudilio
Naphthenic acids (NAs) are toxic compounds naturally present in most petroleum sources with a highly variable concentration depending on their origin. Their occurrence in crude oil can produce severe corrosion problems and catalyst deactivation in oil refineries, consequently impacting their economic value and productivity. Thus, extracting and recovering the NA from crude oil is necessary. In this work, the extraction capacity of two ionic liquids (ILs) of different nature has been studied: 1-ethyl-3-methylimidazolium acetate, [EMIm][OAc], and trihexyltetradecylphosphonium dicyanamide, [P14,6,6,6][CCN2]. In addition, kinetic data were obtained for [P14,6,6,6][CCN2], and a theoretical kinetic model was developed to adjust the experimental data. Two extraction mechanisms have been analyzed using molecular dynamics computational simulations and quantum mechanical calculations. Molecular dynamic results show that a cluster of IL is first formed in each extraction process, and NA molecules are deposited on its surface. Different outcomes are obtained for diffusion coefficient values and radial distribution function. Furthermore, the quantum chemistry calculations show that a proton transfer is thermodynamically favorable in the case of [EMIm][OAc], thus extraction mechanism occurs through a neutralization reaction, whereas for [P14,6,6,6][CCN2], it is not, pointing to a physical extraction.
Combination of molecular dynamics simulation and COSMO to understand asphaltenes aggregation
(Taylor and Francis Ltd., 2023-05-28) Arenas-Fernández, Plácido; Suárez, Inmaculada; Coto, Baudilio
Asphaltenes interaction produces problems in oil transport and recovery, and understanding the association process is vital to improving economic and industrial production. Here, we propose the COSMO model in combination with molecular dynamics (MD) simulations to complement the results obtained by Newtonian mechanics with quantum results to get reliable association data. Four asphaltene molecules were studied with toluene and heptane solvents. COSMO showed molecular interaction tendencies, which were later verified with MD. The average aggregation number was calculated through MD and turned out to be entirely dependent on the aromaticity due to π-π stacking. The aromatic rings are responsible for aggregation, while the sulfur heteroatom plays a less fundamental role. Viscosity is also related to the aggregation process; a higher tendency in aggregation increases the dynamic viscosity. Diffusion coefficients were correlated with the aromaticity, dipole moment, and molecular weight. Finally, a mathematical comparison between COSMO and MD results is accomplished.
Combination of molecular dynamics simulation, COSMO-RS, and experimental study to understand extraction of naphthenic acid
(Elsevier, 2021-09-27) Arenas, Plácido; Suárez, Inmaculada; Coto, Baudilio
The forecast of an increase in the consumption of petroleum products, together with the growing scarcity of new deposits, makes it necessary to take full advantage of existing ones. The main problem faced by the petrochemical industry is high acid crude oils, which produce corrosion in equipment and high monetary losses. Crude oil acidity is usually calculated by making use of the total acid number (TAN). Current operations for the elimination of naphthenic acid (NA) have several drawbacks so at present this has led to new lines of research, among which the application of ionic liquids (ILs) in the extraction of this compound stands out. In this work, the extractive behavior of 6 different ILs has been analyzed with simulations of molecular dynamics (MD), a technique based on classical mechanics that allows visualizing the movement of molecules while they interact. This allows us to study the extraction mechanism of NA by ILs, as well as transport properties such as diffusion coefficients. In addition, it will be experimented in the laboratory with the same cases to contrast the results obtained, making use of a synthetic crude oil (SC, 150 g/mol, TAN equal to 3.8), which was treated with every IL at four different temperatures (30, 70, 90 and 120 °C). The IL/NA ratio implemented was 1:1 mol/mol, which corresponded more or less with the IL/crude ratio of 0.015 g/g. To support (MD) results and experimental results, the COSMO-RS model was used to characterize ILs analyzing the results obtained by the σ-profile. COSMO-Therm was put into practice to study the theoretical predictions of the TAN in the liquid/liquid phase equilibria where results were in agreement with the experimental ones except for acetate, whose extraction mechanism is supposed to be different (neutralization). Computer simulation suggests that a longer alkyl chain of [BMIm] respect [EMIm] behaves better in extraction, and it seems that the anion plays a major role in the extraction process of the NA than the cation of the ILs. This tendency has been correlated with the experimental results.
Engineered PP impact copolymers in a single reactor as efficient method for determining their structure and properties
(Elsevier, 2021) Pastor-García, María Teresa; Suárez, Inmaculada; Expósito, María Teresa; Coto, Baudilio; García-Muñoz, Rafael A.
Impact polypropylene (PP) copolymers (IPCs) are important materials for many commercial applications. These materials are usually synthetized through different methods involving two consecutive reactions in the same phase or in different phases. Here, a laboratory-scale synthesis method based on a sequential liquid- and gas-phase two-step process in a single reactor is developed. Propylene homopolymers and IPCs were synthesized with varying amounts of comonomers and hydrogen. The IPC materials obtained were fully characterized via analytical temperature rising elution fractionation (TREF), differential scanning calorimetry (DSC), 13C nuclear magnetic resonance (13C NMR), gel permeation chromatography with an infrared detector (GPC-IR5), Charpy impact, scanning electron microscopy (SEM), and cross-fractionation chromatography (CFC). The addition of only ethylene to the second step in the absence of hydrogen led to the creation of an ethylene-propylene (EP) copolymer with similar impact strength to that of a propylene homopolymer. The addition of hydrogen to the first step dramatically shortened the length of the PP chains and inhibited catalytic active centers that led to EP copolymer synthesis. This material exhibited very low molecular weight, low ethylene incorporation, and rubbery phases irregularly distributed along the isotactic polypropylene (iPP) matrix, resulting in the formation of an EP copolymer material with poor impact properties. IPCs synthesized without hydrogen and with a 50/50 (v/v) mixture of propylene/ethylene monomers in the second step enhance ethylene incorporation, facilitating adequate homogeneous and heterogeneous ethylene distribution and resulting in a high increment of amorphous ethylene-propylene-rubber (EPR) domains, which remarkably improves impact properties. Additionally, a criterion based on the ratio between EEE and EPE + PEP triads ranging between 1 and 2 was also established to predict the impact resistance of any heterophasic PP. Fractionation of the optimal sample provided a detailed understanding about the microstructure of this copolymer through the study of the molecular weight and composition of the fractions via GPC-IR, analytical TREF, and DSC measurements. Finally, the liquid–gas-phase two-step IPC material was compared, by means of SEM and CFC measurements, with synthesized IPC using liquid–liquid-phase two-step polymerization, and the results showed that the range of EP composition as well as ethylene distribution in the molar mass molecules of the IPCs was correlated to their mechanical behavior. This proves that crystalline families composed of high-molecular-weight EP copolymers in the liquid–gas-phase process can act as a compatibilizing agent between the iPP matrix and the elastomeric rubbery phase, allowing one to improve the impact resistance of the IPC, more so than that of IPCs obtained in the gas–gas and liquid–liquid phases. The results indicate that the synthesis of IPC resins in a single reactor is an efficient experimental method for fundamental research on IPCs.
Experimental data and modeling of viscosities and densities of pyrene + toluene + heptane mixtures at T = (293.15 to 343.15) K
(Elsevier, 2023) Tenorio, Maria José; Suárez, Inmaculada; Díaz Magdaleno, Julia; González, Miguel A.; Coto, Baudilio
Oil mixtures are a complex system that remains unclear. Its study is particularly challenging due to the many variables involved in their properties. These include, for instance, the compositions of the mixture and the nature of their compounds. To simplify the study of these systems, it is proposed to model them with simpler mixtures, as in the case of using hydrocarbon mixtures to describe the behavior of crude oil. Two mixtures have been prepared; the one hand, a binary mixture of pyrene in toluene, and on the other hand, a ternary mixture of pyrene in toluene/heptane has been prepared. Their densities and dynamic and kinematic viscosities have been measured from (293.15 to 343.15) K at atmospheric pressure. The compositions of binary and ternary systems are 1.0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 % weight fraction of pyrene. In the case of ternary systems, several toluene/heptane mass ratios have been studied, from 0.1 to 10. This article presents new experimental results of density and viscosity for the mixtures studied. Therefore, a theoretical study has been carried out to describe experimental data. Viscosity models, such as Ideal, Refutas, Ratcliff, UNIFAC-Visco, and Krieger, have been checked and, in some cases, have been modified to analyze the dependence of viscosity on temperature, composition, and possible association of pyrene. Standard deviations for each model and system have been calculated. Modified Ratcliff and Krieger models presented an excellent agreement with experiments.
Extraction of aromatic and polyaromatic compounds with NMP: experimental and model description
(Elsevier, 2021) Coto, Baudilio; Suárez, Inmaculada; Tenorio, Maria José; Huerga, Isabel
Optimization of the extraction process for reducing aromatic and/or polyaromatic compounds is of primary interest in crude oil refining. Several solvents are described for carrying out such operations (furfural, N-methyl-pyrrolidone -NMP-, dimethyl-sulfoxide -DMSO-, …) and experimental data and model description are required for the correct design of the separation operations and the optimization of the conditions. In this work, liquid-liquid equilibria (LLE) data were determined for oil multicomponent mixtures formed by n-dodecane + mono-aromatic + poly-aromatic with NMP at ambient temperature (298.15 K) and pressure and covering a wide range of the solvent/oil ratios. A new analytical method based on NMR was developed, calibrated, and tested to fully determine the composition of equilibrium phases despite the high number of compounds. Obtained values for distribution constants and selectivities are higher than one and ranging 1-15, respectively, for aromatic compounds and even higher for polyaromatic components. Thus NMP appears as a suitable solvent for carrying both separations. The experimental data were predicted by several versions of the UNIFAC model, including the UNIFAC, modified UNIFAC (Dortmund), modified UNIFAC (NIST), and UNIFAC, including fitting parameters. Overall, modified UNIFAC (Dortmund) yields the best results, even when deviations obtained for some of the compositions are around 40% of the value, and simulations carried out with such models should be considered cautiously
Fast and simplified determination of PCA and aromatic carbon content of treated distilled aromatic extract (TDAE) by NMR
(Springer, 2022-02-24) Coto, Baudilio; Huerga, Isabel; Suárez, Inmaculada; Contreras, Verónica; Pérez, Ponciano
Aromatic oils obtained during lubricants production (DAE) have high value as rubber extenders in tire manufacturing, but they have high carcinogenic potential due to the content of polycyclic aromatic compounds (PCA). Legislation on PCA content requires additional treatment to reach treated oils (TDAE) with PCA content lower than 3% according to the IP-346 method. IP-346 is a highly time-consuming and high uncertainty method, and several proposals have tried to replace it, but nowadays, there is no standard alternative. In this work, an extensive collection of samples covering a broad PCA content were obtained and characterized by physical properties, NMR, and aromatic and PCA content. Several correlations were tested to establish an optimum procedure to estimate the aromatic and the PCA content according to the requirement of high accuracy and low time and effort. The combination of several properties does not improve the accuracy of the correlation, and simpler equations were preferred. Integrated spectra appear as an acceptable characterization method as NMR percent of the total aromatic proton and polycyclic aromatic proton correlates satisfactory with the number of aromatic carbons and PCA content, respectively. The Refractive index yields the best results for the correlation to PCA content. Obtained deviations compare favorably with methods previously described in the literature and with the uncertainty involved in the experimental method. They can be considered adequate methods to analyze such magnitudes routinely.
Influence of the carboxylate anion on the CO2 absorption mechanism using based-imidazolium ionic liquid
(Elsevier, 2025-01) Murillo-Criado; Aguilar-Galindo, Fernando; Serrano, Isabel; Gonzalez, Miguel A.; Tojo, Emilia; Suárez, Inmaculada; Coto, Baudillo; Tenorio, Maria Jose
The reduction of atmospheric carbon dioxide (CO₂) levels is contingent upon the implementation of strategies such as the curtailment of fossil fuel usage, the adoption of renewable energy sources, and the utilization of CO₂ capture and utilization technologies. Although direct air capture (DAC) presents a significant opportunity for global mitigation, industrial efforts have primarily concentrated on pre-combustion, oxyfuel, and post-combustion capture methods to enhance environmental sustainability. Nevertheless, the economic viability of CO₂ reuse remains a significant concern, and the development of innovative solutions is imperative. In this study, the influence of the carboxylate anion on CO2 absorption process using imidazolium-derived ionic liquids (ILs) is compared. 1-Butyl-3-methylimidazolium formate ([BMIm][HCOO]), 1-butyl-3-methylimidazolium acetate ([BMIm][OAc]), and 1-butyl-3-methylimidazolium propionate ([BMIm][C3H5OO]) have been analyzed. The efficacy of the capture process was assessed by quantifying the formation of an IL-CO₂ adduct using nuclear magnetic resonance (NMR) and attenuated total reflection infrared spectroscopy (ATR-IR). Furthermore, this work studies, using Density Functional Theory (DFT) and COSMO modelling, the difference in the spontaneity of the proton transfer from the cation [BMIm]+ to the carboxylate anions of the ionic liquids used in CO2 absorption process. Based on experimental and modelling data, [BMIm][OAc] was identified as the optimal IL candidate, presents a CO2 molar fraction absorbed at 30 °C and 1 bar of 0.203, compared to 0.083 for [BMIm][HCOO] and 0.190 for [BMIm][C3H5OO]. Moreover, theoretical simulations support these results with the calculation of the acid deprotonation equilibrium constants with the highest value being obtained for [BMIm][OAc]
Liquid-Liquid Extraction of polyaromatic compounds with ionic liquid. A theoretical and experimental approach
(Elsevier, 2022) Arenas-Fernández, Plácido; Suárez, Inmaculada; Coto, Baudilio
Recent legislation worldwide aims to reduce the levels of polyaromatics compounds in lubricant bases due to their harmful effect on health. Ionic liquids have obtained broad interest as green recyclable extractants. Here, we presented new experimental data of liquid-liquid extraction implementing ionic liquids for the removal of aromatics compounds of synthetic crude oil in a 1:1 mass/mass ratio for temperatures ranging from 303.15 to 293.15 K. Selectivity and distribution constant data are obtained to know the extractive potential of each ionic liquid. To support the experimental results, several computational calculations have been performed. First, two predictive thermodynamic models COSMO-SAC and UNIFAC, have been applied, and the reliability of both models has been compared with experimental results. The results show that using UNIFAC is more accurate than using COSMO to predict extraction behavior. Second, the extractive process has been studied using molecular dynamics. This tool allows us to understand better how the extraction process occurs and the molecules’ situation when they reach equilibrium. It is shown that the cation of the ionic liquid is the primary driver of liquid–liquid extraction. In addition, molecular dynamics will enable a qualitative comparison between the performance of ionic liquids and the experimental results. It is a helpful tool to save time and material resources before laboratory experimentation.
Práctica de laboratorio virtual de Química General: ácido-base
(Educación Química, 2024-07-01) Rodríguez Montoro, Óscar; Suárez, Inmaculada; Coto, Baudilio
Virtualization of Laboratory Practices Using Visual Basic Excel
(American Chemical Society, 2022-11-16) Coto, Baudilio; Suárez, Inmaculada; Tenorio, Maria José; Gonzalez, Miguel Ángel
The COVID-19 pandemic and its related restrictions forced the reorganization of learning methodology and gave a central role to remote learning. Laboratory experiments are the most affected activity, and several alternatives were described. This work proposes to create calculation tools by simply programming in Visual Basic of Excel to emulate the data acquisition of specific laboratory experiments. The approach appears useful in experiments with a simple setup followed by data analysis. The experiment of gas volumetric properties allows fixing pressure and temperature conditions and measuring the occupied volume. The developed program emulates such operations and reports a computed volume. Further data reduction is the same in both procedures. Such a virtual experience was successfully used with groups of over 100 students. The results obtained were satisfactory compared with those obtained in the laboratory. Detailed analysis of the grades shows that acquired skills are comparable in both methodologies. Consequently, the virtual approach is a flexible option for remote laboratory teaching to complement traditional experimentation.
Viscosities and Densities of Binary and Ternary Mixtures of Aliphatic and Polyaromatic Hydrocarbons: Pyrene +1-Methylnaphthalene + Dodecane at T = (293.15 to 343.15) K. Experiment and Modeling
(American Chemical Society, 2024-03-18) Tenorio, María José; González, Miguel A.; Magdaleno, Julia D.; Suárez, Inmaculada; Coto, Baudilio
This work presents new experimental viscosity and density data for aromatic and polyaromatic compounds in binary and ternary pyrene, 1-methylnaphthalene, and dodecane mixtures. The lack of experimental viscosity data for these mixtures requires the development of a new database, which is vital for understanding the behavior of mixtures in more complex systems, such as asphaltenes and fuels. The mixtures proposed in this work have been measured over a temperature range of (293.15 to 343.15) K at atmospheric pressure. Several mixture compositions have been studied at these conditions: 1.0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0% pyrene mass fraction. The concentration of pyrene correlates with an increase in the viscosity and density values. At the lowest temperature in binary mixtures, the corresponding values reach 4.4217 mPa·s for viscosity and 1.0447 × 103 kg·m–3 for density, respectively. In ternary mixtures, the introduction of dodecane leads to the lowest maximum values of 3.5555 mPa·s for viscosity and 1.0112 × 103 kg·m–3 for density at the same temperature. The experimental data have been employed for the specific modification of viscosity models. These modifications could facilitate the prediction of the viscosity of mixtures that are more complex than those presented in this work. Various viscosity models have been employed, such as Linear, Ratcliff and Khan, modified UNIFAC-Visco, and Krieger–Dougherty. The settings in the models used reliably reproduce the experiment reliably. However, the Ratcliff model agrees excellently with the experiment, having a low standard deviation (2.0%) compared to other models. Furthermore, a model based on the equation of state of Guo is proposed to predict the viscosity values by modifying the specific parameters and adjusting them to the mixtures proposed in this work. The results from this study are compared to previous work, where pyrene, toluene, and heptane mixtures were analyzed. In this case, we find that the decrease of aggregation grade in the present systems is predicted by the model fixed in this work.