Thermodynamics of mixtures containing aromatic nitriles

The coexistence curves of liquid-liquid equilibrium (LLE) for the mixtures: phenylacetonitrile + heptane, + octane, + nonane, + cyclooctane, or + 2,2,4-trimethylpentane and for 3-phenylpropionitrile + heptane, or + octane are reported. Aromatic nitrile + alkane, + aromatic hydrocarbon or + 1 alkanol systems are investigated using a set of thermophysical properties: phase equilibria (solid-liquid, SLE, vapour-liquid, VLE and LLE), excess molar functions, enthalpies (), isochoric internal energies (), isobaric heat capacities () and volumes (), and the Kirkwood’s correlation factor. Due to proximity effects between the phenyl and the CN groups, dipolar interactions between molecules of aromatic nitriles are stronger than those between molecules of isomeric linear nitriles. Dipolar interactions become weaker in the order: 3-phenylpropionitrile > phenylacetonitrile > benzonitrile. Benzonitrile + aromatic hydrocarbon mixtures are characterized by dispersive interactions and structural effects. The latter are more important in systems with phenylacetonitrile. Structural effects are also present in benzonitrile + n-alkane, or + 1-alkanol + mixtures. The systems mentioned above have been studied using DISQUAC. Interaction parameters for contacts where the CN group in aromatic nitriles participates are given. DISQUAC describes correctly any type of phase equilibria, of benzonitrile + hydrocarbon mixtures and of benzonitrile + cyclohexane, or 1-alkanol systems. Large differences encountered between theoretical values and experimental data for some solutions are discussed. 1-Alkanol + benzonitrile mixtures are also investigated by means of the ERAS model. ERAS represents well of these systems. The curves of solutions with longer 1-alkanols are more poorly described, which has been explained in terms of the existence of structural effects.Consejería de Educación y Cultura of Junta de Castilla y León, under Project BU034U1

Thermodynamics and remediation techniques for fuel oxygenates

In the last years, due to an increasing concern about the possible harmful effects of the gas emissions of the continuous gasoline use, their compositions have changed considerably. The lead additives ban and the aromatic compounds content limitation has caused the worldwide expansion of the use of fuel oxygenates. These compounds are mainly molecules with an atom of oxygen inside its structure. Usually they are ethers or alcohols. The most used worldwide is methyl tert-butyl ether (MTBE) followed by ethyl tert-butyl ether (ETBE). These compounds because of their physical and chemical properties have become persistent and recalcitrant pollutants in the groundwaters of the entire world.Due to the problem generate by the contamination of water resources is important to go deeper in the knowledge of the behaviour of fuel oxygenates in the environment in order to obtain tools that let us model and study their environmental dispersion and remediation. This doctoral thesis offers an important thermodynamical study of these compounds and analyzes different remediation techniques.The work is structured in four chapter well differentiated. The first one consists of an introduction to the problem, the current situation of thermodynamical information and the existent techniques for the water treatment.The second chapter is focused on obtaining and improving the thermodynamical information. It is studied how temperature affect to the interactions of fuel oxygenates with different gasoline compounds such us BTEX (benzene, toluene, ethylbenzene and xylenes), alcans or degradation products like tert-butyl alcohol. In this chapter is included new thermodynamical information in terms of physical properties (density and speed of sound), vapor-liquid equilibria and liquid-liquid equilibria (as water solubility). As a result have been characterized 25 binary systems and their pure compounds in terms of physical property, 3 vapor liquid equilibria and finally the study of water solubility of the ethers most used in gasoline blending as temperature function.The third chapter is focused from a technological point of view. Here it is studied thermodynamically, different conventional remediation techniques fort he MTBE and ETBE like the adsorption onto activated carbon and batch air stripping. It is observed that the temperature increases the efficiency in both processes and that ETBE is easier treated. On the other hand, it has been analyzed the use of new solvents, in this case ionic liquids, in order to dehydrate fuel oxygenates obtaining satisfactory results. Finally, studies of advanced oxidation processes have been carried out using Fe-zeolites as catalyst. The use of these materials let oxidize MTBE and their most problematic degradation products, like tert-butyl alcohol and tert-butyl formate at environmental conditions and neutral pH in reasonable times.Finally in the fourth and last chapter are summarized the conclusions obtained during the development of this work and the research directions to follow in the future.En els darrers anys, degut a una creixent preocupació sobre els possibles efectes nocius de les emissions de gasos procedents de l'ús continu de gasolines, la composició d'aquestes ha patit canvis importants. La prohibició dels additius amb plom així com la limitació de compostos aromàtics han donat lloc a una gran expansió arreu del món de l'ús del que es coneixen com additius oxigenats de la gasolina. Aquest compostos son principalment molècules que tenen dins la seva estructura almenys un àtom d'oxigen. Normalment acostumen a ser èters o alcohols. De tots els més utilitzats a nivell mundial son el metil tert butil èter (MTBE), seguit pel etil tert butil èter (ETBE). Aquests compostos degut a les seves propietats físiques i químiques han esdevingut uns contaminants persistents i recalcitrants de les aigues a tot el món.Degut a la problemàtica generada per la contaminació del recursos hídrics és important aprofundir en el coneixement del seu comportament en el medi ambient per tal de obtenir eines que permetin modelitzar i estudiar tant la seva dispersió com la seva remediació. La present tesi doctoral ofereix un estudi termodinàmic important d'aquest compostos i estudia diferents tècniques de remediació.Aquest treball s'estructura en quatre capítols ben diferenciats. El primer d'ells consisteix en una introducció a la problemàtica, la situació actual de la informació física i química de la qual es disposa i de les tècniques existents per al tractament d'aigües contaminades.El segon capítol està enfocat a obtenir i millorar la informació termodinàmica. S'estudia com la temperatura afecta a les interaccions dels additius oxigenats amb diferents constituents de les benzines com son els BTEX(benzè, toluè, etilbenzè i xilens), alcans o compostos de degradació dels oxigenats com pot ser el tert butil alcohol. En aquest capítol s'aporta nova informació termodinàmica prèviament no reportada en la literatura en termes de propietat físiques (densitat i velocitat de so), equilibri vapor líquid i equilibri líquid líquid (en forma de solubilitat en aigua). Com a resultat d'aquest capítol cal remarcar la caracterització de 25 sistemes binaris i els seus compostos purs en termes de propietat física, 3 equilibris binaris líquid vapor i finalment l'estudi de la solubilitat dels èters més utilitzats com additius oxigenats com a funció de la temperatura.El tercer capítol està enfocat des d'un punt de vista tecnològic. En aquest s'estudia termodinàmicament diferent tècniques convencionals per l'eliminació de MTBE i ETBE com son l'adsorció en carbó actiu i l'aireació. S'observa que l'increment de la temperatura augmenta l'eficiència en tot dos processos i que l'ETBE es més fàcilment eliminat. Per altra banda s'ha analitzat l'ús de nous solvents, com son els líquids iònics, per tal de deshidratar additius oxigenats obtenint-se resultats satisfactoris. Finalment s'han realitzat estudis d'oxidació avançada utilitzant zeolites amb contingut fèrric. L'ús d'aquest materials permet oxidar l'MTBE i els seus compostos de degradació més problemàtics, com son el tert butil alcohol i el tert butil formiat en condicions ambientals i pH neutres en temps raonables.Finalment en el quart i últim capítol es resumeixen les conclusions obtingudes durant aquest treball i es donen ressenyes a seguir en investigacions futures en aquest camp

Thermophysical properties, interactions and structure in organic liquid mixtures including polar and/or associated compounds: N, N-dialkylamides, amines, 1-alkanols, ketones and organic carbonates

Una forma de aproximarse al estudio de moléculas orgánicas de gran complejidad, tales como proteínas o aminoácidos, es la investigación de moléculas orgánicas pequeñas cuyos grupos funcionales son similares a aquellos presentes en dichas moléculas. En este contexto, el estudio físico y químico sistemático de mezclas que las contienen en términos de propiedades termodinámicas, dieléctricas o de transporte es necesario para comprender adecuadamente su comportamiento colectivo. Dicho estudio sistemático permite al mismo tiempo elaborar modelos teóricos que se ajusten a las características físicas y comprobar la eficacia de otros ya existentes. Este tipo de estudios, además de su importancia desde el punto de vista fundamental, también es útil desde el punto de vista práctico, ya que los datos experimentales obtenidos y los modelos desarrollados son empleados por la industria. En este trabajo se estudian experimental y teóricamente mezclas líquidas de los tipos: i) N,N-dialquilamida (N,N-dimetilformamida o N,N-dimetilacetamida) + amina (butan-1-amina, hexan-1-amina, N-propilpropan-1-amina, N-butilbutan-1-amina o anilina); y ii) 1-alcanol (metanol, 1-propanol, 1-butanol, 1-pentanol o 1-heptanol) + amina (hexan-1-amina, N-propilpropan-1-amina o N,N,N-trietilamina). En concreto, se determinan experimentalmente propiedades calorimétricas, volumétricas, refractivas o dieléctricas de dichas mezclas, y se estudian teóricamente por medio del modelo de Flory, el modelo ERAS y el modelo de Kirkwood-Fröhlich. También se lleva a cabo una revisión cuidadosa del modelo de Kirkwood-Fröhlich y sus distintas extensiones a sistemas pluricomponentes. Además, se estudian efectos orientacionales por medio de datos experimentales, el modelo de Flory y el formalismo del factor de estructura concentración-concentración en mezclas líquidas de los tipos: i) alcanona, alcanal o dialquil carbonato + alcano y alcanona + alcanona o dialquil carbonato; y ii) carbonatos orgánicos + alcanos o 1-alcanoles. Complementariamente, se mide la entalpía de disolución del dióxido de azufre y del monóxido de nitrógeno en agua, y se evalúa la validez de un modelo teórico presente en la literatura del proceso de disolución del dióxido de azufre en agua. En consecuencia, la presente Tesis Doctoral presenta contribuciones que amplían el conocimiento experimental y teórico existente en el campo de la Termodinámica de Mezclas y Disoluciones.Departamento de Física AplicadaDoctorado en Físic

Experimental Characterization and Molecular Study of Natural Gas Mixtures

Natural Gas (NG) plays an important role in the energy demand in the United States and throughout the world. Its characteristics as a clean, versatile and a sustainable source of energy makes it an important alternative within the spectra of energy resources. Addressing industrial and academic needs in the natural gas research area requires an integrated plan of research among experimentation, modeling and simulation. In this work, high accuracy PpT data have been measured with a high pressure single sinker magnetic suspension densimeter. An entire uncertainty analysis of this apparatus reveals that the uncertainty of the density data is less that 0.05% across the entire ranges of temperature (200 to 500) K and pressure (up to 200 MPa). These characteristics make the PpT data measured in this study unique in the world. Additionally, both a low pressure (up to 35 MPa) and a high pressure (up to 200 MPa) isochoric apparatus have been developed during the execution of this project. These apparatuses, in conjunction with a recently improved isochoric technique, allow determination of the phase envelope for NG mixtures with an uncertainty of 0.45% in temperature, 0.05% in pressure and 0.12% in density. Additionally, an innovative technique, based upon Coherent Anti-Stokes Raman Scattering (CARS) and Gas Chromatography (GC), was proposed in this research to minimize the high uncertainty introduced by the composition analyses of NG mixtures. The collected set of P?T and saturation data are fundamental for thermodynamic formulations of these mixtures. A study at the molecular level has provided molecular data for a selected set of main constituents of natural gas. A 50-50% methane-ethane mixture was studied by molecular dynamics simulations. The result of this study showed that simulation time higher than 2 ns was necessary to obtain reasonable deviations for the density determinations when compared to accurate standards. Finally, this work proposed a new mixing rule to incorporate isomeric effects into cubic equations of state

Predicting solvation free energies using parameter-free solvent models

We present a new approach for predicting solvation free energies in non-aqueous solvents. Utilizing the corresponding states principle, we estimate solvent Lennard-Jones parameters directly from their critical points. Combined with atomic solutes and pressure corrected three-dimensional reference interaction site model (3D-RISM/PC+), the model gives accurate predictions for a wide range of non-polar solvents, including olive oil. The results, obtained without electrostatic interactions and with a very coarse-grained solvent provide an interesting alternative to widely used and heavily parametrized models

Isolation of enantiomers via diastereomer crystallisation

Enantiomer separation remains an important technique for obtaining optically active materials. Even though the enantiomers have identical physical properties, the difference in their biological activities make it important to separate them, in order to use single enantiomer products in the pharmaceutical and fine chemical industries. In this project, the separations of three pairs of diastereomer salts (Fig1) by crystallisation are studied, as examples of the ‘classical’ resolution of enantiomers via conversion to diastereomers. The lattice energies of these diastereomer compounds are calculated computationally (based on realistic potentials for the dominant electrostatic interactions and ab initio conformational energies). Then the experimental data are compared with the theoretical data to study the efficiency of the resolving agent. All three fractional crystallisations occurred relatively slowly, and appeared to be thermodynamically controlled. Separabilities by crystallisation have been compared with measured phase equilibrium data for the three systems studied. All crystallisations appear to be consistent with ternary phase diagrams. In the case of R = CH3, where the salt-solvent ternaries exhibited eutonic behaviour, the direction of isomeric enrichment changed abruptly on passing through the eutonic composition. In another example, R = OH, the ternaries indicated near-ideal solubility behaviour of the salt mixtures, and the separation by crystallisation again corresponded. Further, new polymorphic structures and generally better structure predictions have been obtained through out this study. In the case of R = CH3, an improved structure of the p-salt has been determined. In the case of R = C2H5, new polymorphic forms of the n-salts, II and III, have been both discovered and predicted. This work also demonstrates that chemically related organic molecules can exhibit different patterns of the relative energies of the theoretical low energy crystal structures, along with differences in the experimental polymorphic behaviour. This joint experimental and computational investigation provides a stringent test of the reliability of lattice modelling to explain the origins of chiral resolution via diastereomer formation. All the experimental and computational works investigated in this thesis are published (see APPENDIX 1)

Research on the physics of solid materials Semiannual status report, 15 May - 31 Oct. 1966

Defect structure, mechanical behavior, electrical and optical properties, magnetic, thermodynamic, and thin film properties of solid materials and crystal

Thermodynamics of mixtures containing a very strongly polar compound. 12. Systems with nitrobenzene or 1-nitroalkane and hydrocarbons or 1-alkanols

Mixtures involving nitrobenzene and hydrocarbons, or 1-alkanols and 1-nitroalkane, or nitrobenzene have been investigated on the basis of a whole set of thermophysical properties available in the literature. The properties considered are: excess molar functions (enthalpies, entropies, isobaric heat capacities, and volumes), vapour-liquid and liquid-liquid equilibria, permittivities or dynamic viscosities. In addition, the mixtures have been studied by means of the application of the DISQUAC, ERAS, and UNIFAC models, and using the formalism of the concentration-concentration structure factor. The corresponding interaction parameters in the framework of the DISQUAC and ERAS models are reported. In alkane mixtures, dipolar interactions between 1-nitroalkane molecules are weakened when the size of the polar compound increases, accordingly with the relative variation of their effective dipolar moment. Dipolar interactions are stronger in nitrobenzene solutions than in those containing the smaller 1-nitropropane, although both nitroalkanes have very similar effective dipole moment (aromaticity effect). Systems with 1-alkanols are characterized by dipolar interactions between like molecules which sharply increases when the alkanol size increases. Simultaneously, interactions between unlike molecules become weaker, as the OH group is then more sterically hindered. Interactions between unlike molecules are stronger in systems with nitromethane than in nitrobenzene solutions. The replacement of nitromethane by nitroethane in systems with a given 1-alkanol leads to strengthen those effects related with the alcohol self-association. Permittivity data and results on Kirkwood's correlation factors show that the addition of 1-alkanol to a nitroalkane leads to cooperative effects, which increase the dipolar polarization of the solution, in such way that the destruction of the existing structure in pure liquids is partially counterbalanced. This effect is less important when longer 1-alkanols are involved.Consejería de Educacion y Cultura of Junta deCastilla y Leon, under Project BU034U1

Contributions to the selection of solvents in the extraction of phenolic acids

Naturally occurring phenolic acids are well-known and studied for their bioactive properties and wide distribution in plants, where they can be found in free form, or conjugated to other molecules. The study of the solubility of phenolic compounds in water and organic solvents is thus fundamental for the design of extraction, separation, crystallization and purification processes of great importance in the pharmaceutical, cosmetics and food industries. In this context, the main objective of this work is to measure the solubility of trans-cinnamic, p-coumaric and ferulic acids in water and in seven organic solvents (methanol, ethanol, 1-propanol, 2-propanol, 2-butanone, ethyl acetate and acetonitrile) at 298.2 K and 313.2 K and test the ability of the NRTL-SAC model, with or without the Reference Solvent Approach (RSA), and the Abraham solvation model to correlate, and preferably, predict the solubility data. To accomplish the objectives above the shake-flask method experimental method was combined with UV-Visible spectroscopy and gravimetric methods of analysis to perform the solubility measurements. In general, the results obtained were in close agreement with the very scarce information available in literature. After, the NRTL-SAC segment descriptors of each solute were fitted to solubility data in seven solvents, obtaining average relative errors (ARD) between 23% and 39%. The model was then applied to predict the solubility in other eight solvents, with ARD between 42% and 61%. The RSA was also applied, but no significant improvements were obtained relatively to the first approach. The optimization parameters of the Abraham solutes were also obtained by fitting the solubility data in six solvents for the trans-cinnamic and p-coumaric acids, and seven solvents for the ferulic acid, obtaining ARD between 7% and 24% for correlations and between 4% and 33% for the predictions in the remaining solvents. These values indicate Abraham's solvation model as the most suitable and very satisfactory model to predict the solubility of the selected solutes at 298.2 K.Os ácidos fenólicos de ocorrência natural são bem conhecidos e estudados por suas propriedades bioativas e ampla distribuição em plantas, onde podem ser encontrados na forma livre ou conjugados com outras moléculas. O estudo da solubilidade de compostos fenólicos em água e solventes orgânicos é fundamental para a conceção de seus processos de extração, separação, cristalização e purificação de grande importância nas indústrias farmacêutica, cosmética e alimentar. Nesse contexto, o principal objetivo deste trabalho é a medição de solubilidade dos ácidos trans-cinâmico, p-cumárico e ferúlico em água, e em diferentes solventes orgânicos (metanol, etanol, 1-propanol, 2-propanol, 2-butanona, acetato de etilo e acetonitrilo) a 298,2 K e 313,2 K e testar a capacidade dos modelos NRTL-SAC, combinado ou não com a metodologia do Solvente Referência (RSA), e do modelo de solvatação de Abraham para correlacionar e, preferencialmente prever, os dados de solubilidade. Para atingir esses objetivos, o método dos frascos agitados, combinado com os métodos de espectroscopia de UV-Visível e o gravimétrico, foram selecionados para efetuar as medições de solubilidade. Em geral, os resultados obtidos são bem consistentes com as escassas informações disponíveis na literatura. Finalmente, os descritores de segmentos do soluto NRTL-SAC foram obtidos através do ajuste de dados de solubilidade em sete solventes, obtendo-se um erro relativo médio (ARD) entre 23% e 39%. O modelo foi então avaliado quanto à sua capacidade para prever a solubilidade em oito solventes, obtendo-se um ARD entre 42% e 61%. Os parâmetros dos solutos no modelo de Abraham foram obtidos através do ajuste de dados de solubilidade em seis solventes para os ácidos trans-cinâmico e p-cumárico, e sete solventes para o ácido ferúlico, obtendo-se um ARD entre 7% e 24% para as correlações e entre 4% e 33% para as previsões em sete solventes. Esses valores indicam o modelo de solvatação de Abraham como o mais promissor para prever a solubilidade dos solutos estudados a 298,2 K.This work is a result of: Project “AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); Associate Laboratory LSRE-LCM - UID/EQU/50020/2019 - funded by national funds through FCT/MCTES (PIDDAC); Project AllNat - POCI-01-0145-FEDER-030463, financed by COMPETE and Portugal2020 and national funds through FCT