Loading...
8 results
Search Results
Now showing 1 - 8 of 8
- Thermodynamic description of aqueous solutions of silver nitrate: Experimental and modelingPublication . Arrad, Mouad; Aliyeva, Mehriban; Martins, Mónia A. R.; Thomsen, Kaj; Pinho, SimãoThe water activity of silver nitrate solutions was measured at 298.2 K and 313.2 K using a humidity sensor instrument. Concentrations of silver nitrate up to almost saturation were included. The thermodynamic properties of the system were described by the Pitzer model, the specific interaction theory (SIT), and the Extended UNIQUAC model. The interaction parameters for the models were estimated using experimental freezing points, osmotic coefficients, and solubility for silver nitrate aqueous solutions collected from the open literature, as well as the water activity data measured in this work. Pitzer and SIT parameters were applied by introducing a temperature dependency, enabling these models to cover a more comprehensive temperature range and extrapolate the calculation to higher molalities. Both approaches represent the data satisfactorily up to moderate molalities. The Extended UNIQUAC model, with its built-in temperature dependence, provides the best thermodynamic description of this binary system. It has a very satisfactory solubility diagram and a good description of the osmotic and activity coefficients.
- Evaluation of ionic liquids for the sustainable fractionation of essential oilsPublication . Vilas-Boas, Sérgio M.; Coelho, Aline Zambom; Martins, Mónia A. R.; Coutinho, João A.P.; Ferreira, Olga; Pinho, SimãoFractionation of terpenes from natural complex matrices is economically attractive due to the wide use of these compounds in the cosmetic, food, and pharmaceutical industries. In this study, the potentialities of ionic liquids (ILs), and their mixtures, as separation agents in the fractionation of essential oils, were assessed through experimental and modeling approaches. Inverse gas chromatography was used to investigate solute-solvent interactions, and the COSMO-RS predic t i v e model was applied to describe the experimental data and to search for other potential ILs by selecting the appropriate cation-anion combination. Both the experimental and predicted approaches demonstrate that chloride-based ILs are very good options for fractionating essential oi l s containing hydrogen-bond donor monoterpenoids. In particular, the experimental and COSMO-RS screenings suggest that [P6,6,6,14]Cl gives the best performance for the separation of the main components present in citrus, mentha, and basil essential oils. The results gathered herein allow a deep understanding of terpene-IL interactions, and support the prediction of the ILs performance in the extraction and separation of natural products, optimizing resources and promoting sustainability.
- Tetraalkylammonium Chlorides as Melting Point Depressants of Ionic LiquidsPublication . Martins, Mónia A. R.; Abranches, Dinis O.; Silva, Liliana P.; Pinho, Simão; Coutinho, João A.P.With the (re)advent of eutectic mixtures within the field of deep eutectic solvents, special attention has been given to the measurement of solid–liquid equilibrium (SLE) phase diagrams, supported by the relevant information they can provide on the molecular interactions and melting temperature depression of any given system. As such, this work investigates the SLE phase diagrams of mixtures between ionic liquids and tetraalkylammonium chlorides (methyl, ethyl, and propyl), with the goal of decreasing the melting temperature of ionic liquids and ammonium salts, thus, expanding their application scope. Results show that tetraalkylammonium salts exhibit negative deviations from thermodynamic ideality when mixed with ionic liquids, which are increased by increasing their alkyl chain length and are interpreted in terms of anion exchange mechanisms. In turn, this nonideality contributes greatly to depression of the melting point of the ionic liquids examined. Overall, this work demonstrates that the correct combination of tetraalkylammonium/ILs anions and cations can lead to significant melting point depressions in both species, thus creating new ionic liquid mixtures using an approach akin to that used to form deep eutectic solvents.
- The role of the anion in imidazolium-based ionic liquids for fuel and terpenes processingPublication . Zambom, Aline; Vilas-Boas, Sérgio M.; Silva, Liliana P.; Martins, Mónia A. R.; Ferreira, Olga; Pinho, SimãoAbstract: The potentialities of methylimidazolium-based ionic liquids (ILs) as solvents were evaluated for some relevant separation problems—terpene fractionation and fuel processing—studying selectivities, capacities, and solvent performance indices. The activity coefficients at infinite dilution of the solute (1) in the IL (3), g¥ 13, of 52 organic solutes were measured by inverse gas chromatography over a temperature range of 333.2–453.2 K. The selected ILs are 1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim][PF6], and the equimolar mixture of [C4mim][PF6] and 1-butyl-3-methylimidazolium chloride, [C4mim]Cl. Generally, low polar solutes follow g¥ 1,[C4mim]Cl > g¥ 1,[C4mim][PF6]+[C4mim]Cl > g¥ 1,[C4mim][PF6] while the opposite behavior is observed for alcohols and water. For citrus essential oil deterpenation, the results suggest that cations with long alkyl chains, such as [C12mim]+, promote capacity, while selectivity depends on the solute polarity. Promising results were obtained for the separation of several model mixtures relevant to fuel industries using the equimolar mixture of [C4mim][PF6] and [C4mim]Cl. This work demonstrates the importance of tailoring the polarity of the solvents, suggesting the use of ILs with mixed anions as alternative solvents for the removal of aliphatic hydrocarbons and contaminants from fuels.
- Densities and speed of sound in aqueous ammonium sulfate solutions containing glycine or alaninePublication . Martins, Mónia A. R.; Pinho, Simão; Ferreira, Olga; Cibulka, IvanThe main objectives of this work are the measurement of the densities and speed of sound in aqueous ammonium sulfate solutions containing glycine or alanine. The study of mixtures containing charged electric species is of great relevance for the chemical industry. In this work the new experimental information is combined with that collected from the open literature in order to contribute for an understanding of the forces that rule biologically important structures. A systematic experimental program is implemented to measure the densities and speed of sound in aqueous and in mixed aqueous solutions of ammonium sulfate, (0.1, 0.3, 0.7, 1.0, 1.3, and 2.0) mol•kg-1, containing glycine or alanine, using a digital densimeter at (278.15, 288.15, 298.15, 308.15, and 318.15) K. Density data have been used to calculate the partial molar volumes at infinite dilution which are evaluated and further used to obtain the corresponding transfer volumes for amino acids. Hydration numbers, temperature dependence, and side chain group contributions of amino acids have also been studied. The parameters obtained from the volumetric study are used to understand various mixing effects due to the interactions between amino acids and ammonium sulfate in aqueous solutions. The V(∅,tr)^0 data suggest that ion charged/hydrophilic group interactions are predominant and applying the McMillan and Mayer formalism it was concluded that they are mainly pair wise. According to Hepler (1969) all amino acids, in water and in aqueous ammonium sulfate solutions, can be considered as a structure breaking solutes. These results represent a step in building up an empirical database of different volumetric parameters of protein functional groups in ammonium sulfate and water. Os principais objectivos deste trabalho são a medição da densidade e da velocidade do som em soluções aquosas de sulfato de amónio contendo os aminoácidos glicina ou alanina. O estudo de misturas contendo espécies eléctricas carregadas é de grande relevância para a indústria química. Neste trabalho a nova informação experimental é combinada com informação recolhida na literatura de forma a contribuir para uma melhor compreensão das forças que regem estruturas biológicas importantes. Neste trabalho, foi implementado um programa experimental sistemático para medir as densidades e a velocidade do som em água e em soluções aquosas de sulfato de amónio, (0.1, 0.3, 0.7, 1.0, 1.3 e 2.0) mol•kg-1, contendo glicina ou alanina, usando um densímetro digital a (278.15, 288.15, 298.15, 308.15 e 318.15) K. Os dados da densidade foram utilizados para calcular os volumes molares parciais a diluição infinita, os quais foram avaliados e posteriormente utilizados para obter os correspondentes volumes de transferência para os aminoácidos. Os números de hidratação, a dependência com a temperatura e as contribuições de grupo da cadeia lateral dos aminoácidos foram também estudados. Os parâmetros obtidos a partir do estudo volumétrico foram utilizados para compreender vários efeitos de mistura devido às interacções entre os aminoácidos e o sulfato de amónio em soluções aquosas. Os dados de V(∅,tr)^0 sugerem que as interacções ião carregado/grupo hidrofílico são predominantes, e aplicando o formalismo de McMillan e Mayer concluiu-se que elas são maioritariamente do tipo dupleto. De acordo com Hepler (1969) ambos os aminoácidos, em água e em soluções aquosas de sulfato de amónio, podem ser considerados como solutos que provocam a rutura da solução. Estes resultados representam um passo na construção de uma base de dados empírica de parâmetros volumétricos de diferentes grupos funcionais das proteínas, em sulfato de amónio e água. Hlavním cílem této práce je měření hustot a rychlostí zvuku ve vodných roztocích síranu amonného obsahující glycin nebo alanin. Studium směsí obsahujících nabité elektrické částice je velmi významné pro chemický průmysl. V této práci jsou obsaženy nové informace podložené experimentem a údaji z odborné literatury, které mohou přispět k pochopení sil, které působí na biologicky důležité struktury. Systematický experimentální program je založen na měření hustoty a rychlosti zvuku vodných a smíšených vodných roztoků síranu amonného (0.1, 0.3, 0.7, 1.0, 1.3, a 2.0) mol•kg-1 obsahujících glycin a alanin pomocí vibrační trubice digitálního hustoměru a zvukové cely při teplotách (278.15, 288.15, 298.15, 308.15 a 318.15) K. Údaje o hustotě byly použity pro výpočet parciálních molárních objemů při nekonečném zředění, které dále slouží k získání odpovídajících přenosových objemů aminokyselin. Dále byla zkoumána hydratační čísla, teplotní závislost a skupinové příspěvky vedlejších řetězců aminokyselin. Tyto parametry získané na základě studia objemových vlastností jsou použity k pochopení různých směšovacích efektů, které jsou způsobeny interakcemi mezi aminokyselinami a síranem amonným ve vodném prostředí. Tyto údaje o V(∅,tr)^0 naznačují, že interakce nabitý ion/hydrofilní skupina mají převládající vliv, a na základě použití formalismu McMiliana a Mayera lze odvodit, že jsou převážně párové. Podle Heplera (1969) mohou být všechny aminokyseliny ve vodě a vodných roztocích síranu považovány za látky rozrušující strukturu. Tyto výsledky představují krok při budování empirické databáze různých objemových parametrů proteinových skupin v síranu amonném a vodě.
- Selection and characterization of non-ideal ionic liquids mixtures to be used in COPublication . Martins, Mónia A. R.; Sharma, Gyanendra; Pinho, Simão; Gardas, Ramesh L.; Coutinho, João A.P.; Carvalho, Pedro J.Due to the costs involved, the capture of CO2 in post-combustion is not currently seen as economically viable. Aiming at changing the perception of post-combustion CO2 from a costly and non-profitable process to a valuable commodity and fostering the development of the next-generation of technologies, novel solvents and their mixtures have been investigated. In this work, mixtures of non-volatile ionic liquids were screened by COSMO-RS aiming to find mixtures with positive excess volumes that could present an increased CO2 capture by physical sorption. The most promising mixtures identified by COSMO-RS, [C4C1im][DMP] or [C4C1im][NTf2] þ carboxylate-based protic ILs were characterized through the measurement of their thermophysical properties, namely density and viscosity. Both properties were measured for pure ILs and their binary mixtures at different temperatures and compositions. The temperature dependence of density of pure ILs was described using the Gardas and Coutinho model while viscosity was accurately described using the Vogel Tammann Fulcher equation. The Redlich-Kister equation was used to predict the excess molar volumes and the non-ideality of the mixtures’ viscosity was assessed using the Grunberg and Nissan mixing law. The excess molar volumes for mixtures containing [C4C1im][DMP] show large positive values all over the range of compositions and temperatures, making them good candidates for CO2 capture. To the best of our knowledge, the excess molar volumes obtained in this work were the highest reported so far. COSMO-RS was able to correctly predict the trend of the experimental excess molar volumes for these mixtures. Regarding viscosity, mixtures of [C4C1im] [DMP] with the carboxylate-based protic ILs led to the desired viscosity decrease compared to the pure aprotic IL, and large deviations from ideality were observed. The mixing of ILs is thus an efficient way to fine-tune the properties, in this case decreasing the viscosity while increasing the sorption capacity.
- Solubility of olive oil phenolic compounds in green solventsPublication . Vale, Mariana Ribeiro de Paula; Zambom, Aline; Krüger, Felipe; Martins, Mónia A. R.; Coutinho, João A.P.; Pinho, Simão; Peres, António M.; Ferreira, OlgaOlive oil production yields by-products rich in bioactive phenolics with potential uses in several types of industries
- Solubility of olive oil phenolic compounds in green solventsPublication . Vale, Mariana Ribeiro de Paula; Zambom, Aline; Krüger, Felipe; Martins, Mónia A. R.; Coutinho, João A.P.; Pinho, Simão; Peres, António M.; Ferreira, OlgaThe production of olive oil generates various by-products that are rich in phenyl alcohols, secoiridoids, phenolic acids and aldehydes, flavonoids, and other bioactive compounds. Due to their diverse biological activities, these compounds have promising potential as functional additives in the food, pharmaceutical, and cosmetics industries.1 However, data on their solubility in water and common volatile organic solvents, as well as partitioning behavior—critical for optimizing extraction, purification, and formulation processes—remains very limited. In this study, the solubility of tyrosol (a phenyl alcohol) was experimentally determined in ten pure solvents and five aqueous binary solvent mixtures, using acetone, ethanol, 2-propanol, 1,3-butanediol, and 1,3-propanediol as co-solvents. Measurements were performed at 298 K using the analytical isothermal shake flask method. Additionally, the COnductor-like Screening MOdel for Real Solvents (COSMO-RS)3 using the default conformer distribution was employed to predict the solubility of tyrosol, hydroxytyrosol, and oleuropein in a wide range of pure organic solvents varying in polarity and functional groups, as well as in aqueous binary solvent mixtures. For tyrosol, the influence of solvent conformers and their apolar, hydrogen bond donor, and acceptor characteristics on COSMO-RS predictions was analyzed, as illustrated in Figure 1 for water–ethanol mixtures. Overall, the model effectively captures general solubility trends, though with reduced quantitative accuracy in polar aprotic solvents, indicating its utility for preliminary solvent selection.