Dados experimentais de algumas propriedades de componentes do biodiesel nÃo podem ser obtidos experimentalmente ou sÃo escassos. Com isso, a utilizaÃÃo de mÃtodos preditivos torna-se fundamental para o cÃlculo de propriedades fÃsicas e termodinÃmicas de Ãsteres que compÃem o biodiesel. Neste trabalho, foram avaliados mÃtodos para o cÃlculo de propriedades crÃticas e do fator acÃntrico atravÃs do cÃlculo da densidade utilizando a equaÃÃo de Rackett-Soave. MÃtodos para o cÃlculo da temperatura normal de fusÃo e temperatura normal de ebuliÃÃo tambÃm foram avaliados. Os mÃtodos avaliados para a temperatura normal de fusÃo nÃo apresentaram bons resultados, com isso correlaÃÃes para esta propriedade foram propostas. TrÃs versÃes do mÃtodo GCVOL foram avaliadas, juntamente com a equaÃÃo de Rackett-Soave, para o cÃlculo da densidade de biodiesel. As quatro equaÃÃes apresentaram-se satisfatÃrias. PorÃm, a equaÃÃo de Rackett-Soave foi a Ãnica que apresentou comportamento fisicamente consistente para a densidade a altas temperaturas. A partir disso, a equaÃÃo de Rackett-Soave foi estendida para altas pressÃes. Dois modelos baseados no princÃpio dos estados correspondentes (Carmo1F e Carmo2F) foram propostos para a prediÃÃo de viscosidade de Ãsteres e biodiesel. O modelo de Ceriani tambÃm foi avaliado. Os modelos Carmo1F e Carmo2F apresentaram bons resultados para a viscosidade de biodiesel. No entanto, para Ãsteres o modelo de Carmo1F nÃo apresentou bons resultado e por isso nÃo deve ser utilizado para esse tipo de composto. O modelo de Carmo2F apresentou bons resultados apenas para Ãsteres saturados. O modelo de Ceriani apresentou bons resultados para Ãsteres, mas resultados piores que os modelos de Carmo1F e Carmo2F foram encontrados para biodiesel. AlÃm disso, quatro mÃtodos de contribuiÃÃo de grupos para o coeficiente de atividade foram avaliados para sistemas de equilÃbrio lÃquido-lÃquido contendo biodiesel + glicerol + Ãlcool (metanol ou etanol). Os mÃtodos que apresentaram as melhores prediÃÃes foram o UNIFAC-Dortmund e ASOG. Por isso, eles sÃo os mÃtodos indicados para a simulaÃÃo de equilÃbrio lÃquido-lÃquido de sistemas contendo biodiesel. / Experimental data for some properties of biodiesel components cannot be obtained or are scarce. Therefore predictive methods are fundamental tools for calculating physical and thermodynamic properties of esters in biodiesel. In this work, methods for critical properties and acentric factor were evaluated by the Rackett-Soave for density calculations. Methods for freezing temperature and boiling temperature have also been evaluated. Freezing temperature methods did not present good results. Therefore correlations were proposed for this property. Three versions of GCVOL method and the Rackett-Soave equation were evaluated for biodiesel density predictions. These four models presented satisfactory results. However, Rackett-Soave equation was the only that presented a physically consistent behavior for the density at high temperatures. Thereat, Rackett-Soave equation was extended to high pressures. Two models based on corresponding states principle (Carmo1F and Carmo2F) were proposed for viscosity predictions of esters and biodiesel. The Cerianiâs model was evaluated too. Carmo1F and Carmo2F models obtained good results for biodiesel viscosity. However, the Carmo1F model did not present good results for esters and, for this reason, this model should not be used for these components. The Carmo2F model presented good predictions for saturated esters viscosity. The Cerianiâs model presented good results for ester, but in comparison to Carmo1F and Carmo2F models, worse results have been obtained for biodiesel. Furthermore, four group contributions methods for activity coefficient were evaluated for liquid-liquid equilibrium systems composed of biodiesel + glycerol + alcohol (methanol or ethanol). The models that have output the best predictions were the UNIFAC-Dortmund and ASOG models. As such, these two models are recommended to simulated liquid-liquid equilibrium of biodiesel containing systems.

O objetivo deste trabalho é estudar e identificar as não idealidades do sistema água, etanol e glicerina, solução resultante do processo de purificação da glicerina bruta obtida do biodiesel. A proposta é avaliar uma relação de equilíbrio líquido-vapor que contemple todas as não idealidades. O coeficiente de atividade foi calculado pelo método de contribuição de grupos UNIFAC, utilizando parâmetros propostos por Marcolli e Peter (2005) para sistemas de polióis e água. O cálculo do fator de Poynting utilizou a equação de Rackett modificada, pois foi considerado que os fluidos do sistema são líquidos incompressíveis. Após pesquisa na literatura, não foram encontrados dados experimentais do coeficiente de fugacidade da glicerina. Admitiu-se que a fase vapor é uma mistura ideal de gases reais. Portanto, o cálculo do coeficiente de fugacidade não considerou o efeito de mistura. Foram avaliados os métodos: equação cúbica de estado de Peng e Robinson e segundo coeficiente da equação de estado Virial, que foi estimado através de um método de contribuição de grupos e métodos baseados no teorema de estados correspondentes. A proposta de Lee e Chen (1998) foi escolhida e aplicada no resultado final deste estudo, uma proposta do equilíbrio líquido-vapor do sistema água, etanol e glicerina. A sua análise apresentou relevância de não idealidades na fase líquida e na fase vapor. / This research aims to investigate the non-ideality of the system water, ethanol and glycerol from the purification process of the waste of biodiesel production, using rigorous relation for vapor-liquid equilibrium. The activity coefficient was calculated with the group contribution method UNIFAC, with new parameters for polyols/water systems proposed by Marcolli and Peter (2005). The Poynting factor was calculated using the Rackett Equation, assuming incompressible fluid for all components of the system. No experimental results for the fugacity coefficient of the vapor phase of glycerol are available in the literature. The calculation of the fugacity coefficient of the vapor phase for all components of the system was made by the Peng-Robinson equation of state and estimation of second Virial coefficient, using the group contribution and corresponding states methods and assuming ideal mixture of real gases. Lee and Chen (1998) method for the fugacity coefficient were applied for a final vapor-liquid equilibrium model for the system water, ethanol e glycerol. This study indicates strong non-idealities on both liquid and vapor phases.

O objetivo deste trabalho é estudar e identificar as não idealidades do sistema água, etanol e glicerina, solução resultante do processo de purificação da glicerina bruta obtida do biodiesel. A proposta é avaliar uma relação de equilíbrio líquido-vapor que contemple todas as não idealidades. O coeficiente de atividade foi calculado pelo método de contribuição de grupos UNIFAC, utilizando parâmetros propostos por Marcolli e Peter (2005) para sistemas de polióis e água. O cálculo do fator de Poynting utilizou a equação de Rackett modificada, pois foi considerado que os fluidos do sistema são líquidos incompressíveis. Após pesquisa na literatura, não foram encontrados dados experimentais do coeficiente de fugacidade da glicerina. Admitiu-se que a fase vapor é uma mistura ideal de gases reais. Portanto, o cálculo do coeficiente de fugacidade não considerou o efeito de mistura. Foram avaliados os métodos: equação cúbica de estado de Peng e Robinson e segundo coeficiente da equação de estado Virial, que foi estimado através de um método de contribuição de grupos e métodos baseados no teorema de estados correspondentes. A proposta de Lee e Chen (1998) foi escolhida e aplicada no resultado final deste estudo, uma proposta do equilíbrio líquido-vapor do sistema água, etanol e glicerina. A sua análise apresentou relevância de não idealidades na fase líquida e na fase vapor. / This research aims to investigate the non-ideality of the system water, ethanol and glycerol from the purification process of the waste of biodiesel production, using rigorous relation for vapor-liquid equilibrium. The activity coefficient was calculated with the group contribution method UNIFAC, with new parameters for polyols/water systems proposed by Marcolli and Peter (2005). The Poynting factor was calculated using the Rackett Equation, assuming incompressible fluid for all components of the system. No experimental results for the fugacity coefficient of the vapor phase of glycerol are available in the literature. The calculation of the fugacity coefficient of the vapor phase for all components of the system was made by the Peng-Robinson equation of state and estimation of second Virial coefficient, using the group contribution and corresponding states methods and assuming ideal mixture of real gases. Lee and Chen (1998) method for the fugacity coefficient were applied for a final vapor-liquid equilibrium model for the system water, ethanol e glycerol. This study indicates strong non-idealities on both liquid and vapor phases.

Graduation date: 1994

The work conducted in this thesis is two-fold. First, binary vapor liquid equilibria of several solvent/CO2 systems are measured at 40 ?? The systems analyzed are all gas-expanded liquids (GXLs) characterized with a Jerguson Cell apparatus. A Jerguson cell is a windowed pressure vessel that allows one to measure the height of the condensed liquid. Using this height and the known overall contents in the cell, one can calculate the liquid composition without using any external sampling. Secondly, this same setup is attached to a sampling system, and solid solubility (fractional crystallization) is measured for various GXL systems. The CO2 acts as an antisolvent in what is commonly known as a gaseous antisolvent (GAS) system. Essentially, this work shows that expansion of the tested solvents with CO2 will cause the precipitation of the solid solute. This work also analyzes the affect two solutes have on each other in a quaternary GAS system. Gas-expanded liquids combine desirable gaseous properties and liquid properties to yield a very useful solvent for many applications. An advantage of GXLs is that a relatively small change in pressure or temperature can greatly affect the solvation properties. The tunability of GXLs increases as the amount of the gas (usually CO2) increases in the liquid phase. With the benign chemical nature and environmental impact of CO2 processing, GXLs and supercritical fluids (SCFs) have garnered a lot of attention for industry and academia. Supercritical fluids in this work refer to pure CO2 above its critical temperature and pressure.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 187-190.

This thesis is an investigation of the anode of a direct methanol fuel cell (DMFC) through numerical modeling and simulation. This model attempts to help better understand the two phase flow phenomena in the anode as well as to explain some of the many problems on the anode side of a DMFC and show how changing some of the anode side properties could alleviate these problems. This type of modeling is important for designing and optimizing the DMFC for specific applications like portable electronics. Understanding the losses within the DMFC like removable of carbon dioxide, conversion losses, and methanol crossover from the anode to the cathode will help the DMFC become more commercially viable. The model is based on two phase flow in porous media combined with equilibrium between phases in a porous media with contributions from a capillary pressure difference. The effect of the physical parameters of the fuel cell like the thickness, permeability, and contact angle as well as the operating conditions like the temperature and methanol feed concentration, have on the performance of the DMFC during operation will be investigated. This will show how to remove the gas phase from the anode while enabling methanol to reach the catalyst layer and minimizing methanol crossover. / text

In this work VLE data was measured on three different pieces of equipment. Measurements were undertaken in the laboratory of Professor Gmehling in Oldenburg, Germany using two different static cells and in the Thermodynamics Research Unit (TRU), University of Natal, South Africa using a specially designed dynamic still. The three pieces of equipment used are as follows: i.) Static apparatus of Rarey and Gmehling (1993), ii.) Static apparatus of Kolbe and Gmehling (1985) as modified by Fischer and Wilken (2001), and, iii.) Dynamic apparatus ofHarris et al. (2003b). In total 370 data points were measured; fourteen sets of VLE data and eight vapour pressure data sets were measured. The work undertaken in Germany measured the systems hexane (1) + N-methylformarnide (2), benzene (1) + N-methylformamide (2), cWorobenzene (1) + N-methylformarnide (2) and acetonitrile (1) + N-methylformamide (2), at 363.15 K using the equipment of Rarey and Gmehling (1993). The systems CO2 (1) + Napthalene (2) at T = 372.45 K, 403.85 K and 430.65 K and CO2 (1) + Benzoic acid (2) at T= 403.28 K, 432.62 K and 458.37 K were measured on the equipment of Kolbe and GmeWing (1985) (as modified by Fischer and Wilken (2001)). Apart from the CO2 (1) + Napthalene (2) system at T = 372.45 K, all the above-mentioned data are new data. The equipment designed in the TRU was designed to operate between 300 and 700 K and between 1 kPa and 30 MPa. The equipment is of the dynamic recirculating VLE still type (DRVS) and is based on the principles of low-pressure stills. The still is constructed from uniquely machined Stainless-steel components and standard commercial Stainless-steel tubing and valves and is computer controlled to operate either isobarically or isothermally. Vapour pressures were measured on the new equipment for n-heptane, n-decane, n-dodecane, n-hexadecane, l-octadecene, 1-hexadecanol and d,l-menthol at low pressures and for acetone at high pressures. These vapour pressure measurements were used as test systems and ranged from 1.00 kPa to 1 000 kPa and from 308.33 K to 583.90 K. Cyclohexane (1) + ethanol (2) at 40 kPa and n-dodecane (1) + l-octadecene (2) at 26.66 kPa were measured as two isobaric VLE test systems. The VLE data measured for d,l-menthol (1) + l-isomenthol (2) at T= 448.15 K and n-dodecane (1) + l-octadecene (2) at P = 3.0 kPa represent new data measured on the equipment. All the VLE systems were modeled. Two data reduction methods were investigated: i.) the combined (r-rf) method, and, ii.) the direct method (H) method. Several different Gibbs excess models (Wilson, NRTL and UNIQUAC), equations of state (PengRobinson and virial) and mixing rules (Huron-Vidal, Wong-Sandler and Twu-Coon) were used in different combinations to find the best fit for the data. The Maher and Smith (1979) method was used to determine infinite dilution activity coefficients from the very smooth data of the N-methylformamide systems. Excess properties were determined for the CO2 (1) + Napthalene (2) and the CO2 (1) + Benzoic acid (2) systems. Although the equipment of Hams et al. (2003b) was able to measure data at high temperatures and elevated pressures, the precission of the data was not as good as was expected. Measuring the system temperature at elevated temperatures was especially problematic. The problem is attributed to the large mass of Stainless-steel used in the construction of the apparatus. To rectify this problem it is suggested that the equipment be modified to be lighter in weight and only capable of measuring VLE at moderate pressures (less than 3 MPa). / Thesis (Ph.D.)-University of Natal, Durban, 2004.

Vapour-liquid equilibrium (VLE) data of high accuracy and reliability is essential in the development and optimization of separation and chemical processes. This study focuses on satisfying the growing demand for precise VLE data at low to moderate pressures, by development of a computer-aided dynamic glass still which is semi-automated. The modified dynamic glass still of Joseph et al. (2001) was employed to achieve precise measurement of phase equilibrium data for a pressure range of 0 to 500 kPa. The study involved the assembling and commissioning of a new moderate pressure dynamic still and various peripheral apparati. The digital measurement and control systems were developed in the object-oriented graphical programming language LabVIEW. The digital proportional controller with integral action developed by Eitelberg (2009) was adapted for the control of pressure and temperature. Pressure and temperature measurements were obtained by using a WIKA TXM pressure transducer and Pt-100 temperature sensor respectively. The calculated combined standard uncertainties in pressure measurements were ±0.005 kPa, ±0.013kPa and ±0.15kPa for the 0-10 kPa, 10-100 kPa and 100-500 kPa pressure ranges respectively. A combined standard uncertainty in temperature of ±0.02 K was calculated. The published data of Joseph et al., (2001) and Gmehling et al,. (1995) for the cyclohexane (1) and ethanol (2) system at 40kPa and 1-hexene (1) + N-methyl pyrrolidone-2 (NMP) (2) system at 363.15 K respectively served as test systems. NMP is regarded as one of the most commonly used solvents in the chemical industry due to its unique properties such as low volatility, thermal and chemical stability. As a result the isothermal measurement of 1-hexene (1) + N-methyl pyrrolidone-2 (NMP) (2) system were conducted at 373.15 K constituting new VLE data. A further system comprising 1-propanol (1) and 2-butanol (2) was also measured at an isothermal temperature of 393.15 K. The measured data were regressed using the combined and direct methods. The equations of state of Peng-Robinson (1976) and Soave-Redlich-Kwong (1972) combined with the mixing rules of Wong-Sandler (1992) in conjunction with a Gibbs excess energy model was utilized for the direct method. The activity coefficient models namely Wilson (1964) and NRTL (Renon and Prausnitz, 1968) were chosen to describe the liquid non-idealities while the vapour phase non-ideality was described with the virial equation of state with the Hayden and O’ Connell (1975) correlation. Thermodynamic consistency of the measured data was confirmed using the point test of Van Ness et al. (1973) and the direct test of Van Ness (1995). / M.Sc.Eng. University of KwaZulu-Natal, Durban 2014.

O equilíbrio sólido-líquido de sistemas binários de alcoóis graxos e de ésteres graxos foi descrito por meio de modelagem termodinâmica baseada na análise de estabilidade da fase líquida. A metodologia foi aplicada a três tipos de diagramas de fases: (a) sistemas cujos constituintes apresentam miscibilidade completa, em que as substâncias são miscíveis tanto na fase sólida quanto na líquida, (b) sistemas que apresentam ponto eutético simples, (c) sistemas que apresentam ponto eutético e reação peritética. A caracterização da não-idealidade foi feita com o modelo de coeficientes de atividade de Flory-Huggins para descrição dos diferentes comportamentos, que resultou em bom ajuste dos dados. A uniformidade do valor dos parâmetros ajustados mostra que há diferentes interações moleculares comparando-se as funções químicas álcool, éster etílico e éster metílico e a presença de insaturação na cadeia carbônica. Observa-se que os resultados são fortemente afetados pelos valores de entalpia e temperatura de fusão dos compostos puros. A metodologia desenvolvida foi implementada em linguagem Fortran. Do ponto de vista formal, a análise apresentada mostra que a ocorrência de peritéticos pode ser descrita sem que seja necessário postular um modelo de coeficiente de atividade para a fase sólida quando houver imiscibilidade total. / In this work, the modeling of solid-liquid equilibrium of binary systems containing fatty alcohols or fatty esters is presented. Phase equilibrium calculations were carried out using a phase stability analysis which describes the onset of the solid phase formation. The developed methodology was applied to the modeling of three distinct types of phase diagrams: (a) systems wherein the components are miscible in both phases, (b) systems with a single eutectic point, (c) systems with eutectic point and peritectic reaction. The liquid phase non-ideality was accounted for through the Flory- Huggins model for the excess Gibbs energy. It was possible to describe the different types of phase diagrams with excellent agreement with the experimental data. The values of the adjustable parameters are rather low and depend on both the chemical function of the species considered (alcohol, methyl ester or ethyl ester) and the presence of unsaturation in their molecules. The calculated phase diagrams are strongly affected by the experimental values of enthalpy of fusion and temperature of fusion of the pure compounds. Concerning the thermodynamic description of the solid-liquid equilibrium, the presented analysis showed that it is possible to account for the peritectic reaction without assigning a model for the solid phase activity coefficient when the compounds are not miscible in this phase.