Accurate and reliable vapour-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE) data are the key to a successful design and simulation of most important industrial separation processes (traditional distillation, extractive and azeotropic distillation). This work focuses on measurement of new phase equilibrium data for systems comprising of propan-1-ol, water and diisopropyl ether which are of important use in the petrochemical industry. In addition, an investigation of phase equilibrium behavior for systems of interest constituted by solvents and high added-value oxygenated compounds deriving from lignocelluloses biomasses (bio-fuels) was conducted at the Ecole des Mines de Paris CEP/TEP laboratories (France).Various data bases such as Science Direct, ACS publications and Dortmund Data Bank (DDB, 2009) were used to confirm that no literature data is available for these systems. The VLE data measurements for the system of propan-1ol + water and propan-1ol + diisopropyl ether (DIPE) ( 333.15, 353.15 and 373.15 K ) were carried out using a dynamic still of Lilwanth (2011), with a test system (ethanol + cyclohexane at 40 kPa) undertaken prior measurements to confirm the accuracy of the method and apparatus.The phase equilibrium (VLE and LLE) behaviours for furan + n-hexane and furan + Methylbenzene, furfural + n-hexane and furan + water were determined at 101.3 kPa. The atmospheric dynamic ebulliometry was used to measure VLE systems at 101.3 kPa. A set of LLE data for furfural + n-hexane and furan + water systems were obtained using a static analytical method, with a newly commissioned LLE apparatus. Furfural + n-hexane system was compared used as test system, to verify the reliability of the new equipment. The NRTL model was used to correlate the LLE data, with Cox- Herington model used to predict the entire LLE curve for furfural+ n-hexane system. The experimental VLE data were correlated using the combined y − y method. The vapour phase non idealities were described using the methods from Nothnagel et al. (1973), Hayden and O’Connell (1975) and the Peng-Robinson (1976) model. The activity coefficients were correlated using the NRTL model of Renon and Prausnitz (1968) and the modified UNIQUAC model of Abrams and Prausnitz (1976). A propan-1-ol dehydration process was simulated using Aspen to illustrate the use and importance of thermodynamic models in industrial process design and simulation. The model used in the simulation was validated with measured VLE and literature LLE data. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

Vapour-Liquid Equilibrium (VLE), Liquid-Liquid Equilibrium (LLE) and Vapour-Liquid-Liquid Equilibrium (VLLE) are of special interest in chemical engineering as these types of data form the basis for the design and optimization of separation processes such as distillation and extraction, which involve phase contacting. Of recent, chemical companies/industries have required thermodynamic data (especially phase equilibrium data) for chemicals that are expensive or costly to synthesize. Phase equilibrium data for such chemicals are scarce in the open literature since most apparatus used for phase equilibrium measurements require large volumes (on average 120 cm3) of chemicals. Therefore, new techniques and equipment have to be developed to measure phase equilibrium for small volumes across reasonable temperature and pressure ranges. This study covers the design of a new apparatus that enables reliable vapour pressure and equilibria measurements for multiple liquid and vapour phases of small volumes (a maximum of 18 cm3). These phase equilibria measurements include: VLE, LLE and VLLE. The operating temperature of the apparatus ranges from 253 to 473 K and the operating pressure ranges from absolute vacuum to 1600 kPa. The sampling of the phases are accomplished using a single Rapid-OnLine-Sampler- Injector (ROLSITM) that is capable of withdrawing as little as 1μl of sample from each phase. This ensures that the equilibrium condition is not disturbed during the sampling and analysis process. As an added advantage, a short equilibrium time is generally associated with a small volume apparatus. This enables rapid measurement of multiple phase equilibria. A novel technique is used to achieve sampling for each phase. The technique made use of a metallic rod (similar in dimension to the capillary of the ROLSITM) in an arrangement to compensate for volume changes during sampling. As part of this study, vapour pressure and phase equilibrium data were measured to test the operation of the newly developed apparatus that include the following systems: • VLE for 2-methoxy-2-methylpropane + ethyl acetate at 373.17 K • LLE for methanol + heptane at 350 kPa • LLE for hexane + acetonitrile at 350 kPa • VLLE for hexane + acetonitrile at 348.20 K New experimental vapour pressure and VLE data were also measured for systems of interest to petrochemical companies. These measurements include: • VLE for methanol + butan-2-one at 383.25, 398.14 and 413.20 K ABSTRACT • VLE for ethanol + butan-2-one at 383.26, 398.23 and 413.21 K • VLE for ethanol + 2-methoxy-2-methylbutane at 398.25 and 413.19 K • VLE for ethanol + 2-methylpent-2-ene at 383.20 K These measurements were undertaken to understand the thermodynamic interactions of light alcohols and carbonyls as part of a number of distillation systems in synthetic fuel refining processes which are currently not well described. Two of these above mentioned systems include expensive chemicals: 2-methoxy-2-methylbutane and 2-methylpent-2-ene. The experimental vapour pressure data obtained were regressed using the extended Antoine and Wagner equations. The experimental VLE data measured were regressed with thermodynamic models using the direct and combined methods. For the direct method the Soave-Redlich-Kwong and Peng-Robinson equations of state were used with the temperature dependent function (α) of Mathias and Copeman (1983). For the combined method, the virial equation of state with the second virial coefficient correlation of Tsonopoulos (1974) was used together with one of the following liquid-phase activity coefficient model: TK-Wilson, NRTL and modified UNIQUAC. Thermodynamic consistency testing was also performed for all the VLE experimental data measured where almost all the systems measured showed good thermodynamic consistency for the point test of Van Ness et al. (1973) and direct test of Van Ness (1995). / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2011.

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The South African based petrochemical company, SASOL, operates three large plants for the recovery and purification of the chemical 1-hexene. The thermodynamic models available in commercial simulation packages fail to predict or correlate the plant data presently observed by SASOL. The focus of this project is the accruement of comprehensive and accurate modelling parameters that would assist SASOL in optimizing the operation of the three plants and meet their purity specifications. The experimental requirements of the project are the measurement of isothermal vapour-liquid equilibrium (VLE) data for selected binary systems, using a dynamic still. The binary systems investigated were 1-hexene + n-methylpyrrolidone (NMP) at 40, 62 and 90 °C, water + NMP at 70, 90 and 107 °C and 1-hexene + 3methylcyclopentene (3MCP) at 40, 50 and 60 °C. With respect to the modelling of the VLE data, the combined (gamma-phi) and direct (phi-phi) regression procedures were utilized. The results of the analysis show the combined method as the more flexible of the two, when used for low pressure systems. The excess Gibbs energy correlations investigated were the Margules, Van Laar, Wilson, NRTL and UNIQUAC. The NRTL and Van Laar models dominated the modelling results across the range of temperatures for each binary system and for both the direct and combined methods of data regression. The experimental data for the systems of water (1) + NMP (2) at 107 °C and at 70 °C were compared to literature data. The first system showed excellent correlation with the literature results while the second plot at 70 °C showed a positive bias of the experimental data between xj of 0.3 and 0.8. Thermodynamic consistency tests for the VLE data are also required to verify the accuracy of the data. For this project, the point and direct (Van Ness) consistency tests were used as the area test was considered as too mild. All systems passed the point and direct tests for the combined method and therefore verify the thermodynamic consistency of the experimental data. The systems failed in most cases for the direct method as the combined method is the more flexible of the two modelling methods. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

VLE data is essential for the design and optimisation of industrial separation processes. Carboxylic acids are of significant interest because of their importance in both industrial and biological processes. Carboxylic acids are used as raw materials for a wide range of products, which include soaps , detergents, nylon , biodegradable plastics, medical drugs and food additives, They are also used both as solvents and as additives and co solvents under a wide range of conditions. Carboxylic acids exhibit strong self and cross -association through hydrogen bonds in both liquid and vapour phases. A thorough understanding of how these molecules interact both with themselves and with other solvents becomes necessary if existing processes may be optimised and new processes developed. Vapour-liquid equilibrium (VLE) data were measured for carboxylic acid systems ranging from C3 to C6• New vapour-liquid equilibrium data were measured for the following binary carboxylic acid systems: • Propionic acid + Hexanoic acid at 20 kPa, 403.15 K, 408.15 K and 413.15 K. • Isobutyric acid + Hexanoic acids at 20 kPa, 413.15 K and 423.15 K. • Valerie acid + Hexanoic acid at 15 kPa, 423 .15 K and 433.15 K. • Hexanoic acid + Heptanoic acid at 10 kPa and 443.15 K. A highly refined dynamic VLE Still by Raal (Raal and Muhlbauer [1998]) was used to undertake the VLE measurements. The still was operated either isothermally or isobarically using a computer control scheme. The isobaric and isothermal control was measured to be ±0.03 kPa and ±0.02 K respectively. The experimental procedure was verified with the highly volatile cyclohexane (l) + ethanol (2) system. The cyclohexane (l) + ethanol (2) measured VLE data was found to be in good agreement with that of Joseph (2001) and passed both the direct test and point test for thermodynamic consistency. A high degree of confidence was then placed on the equipment set-up and experimental procedure, as well as the new carboxylic acids VLE data . The VLE data for all the systems measured were modelled. Two data reduction methods were used: I. The combined ( r- ¢ ) method u. The direct method (¢ - ¢ ) method. In the combined method, the vapour phase non-idea lity was corrected using the Pitzer-Curl (1957) correlation and the Hayden and O' Connell (1975) chemical theory approach. Three liquid phase activity coefficient models were used namely the Wilson, NRTL, and UNIQUAC equations. The Peng-Robinson equation of state (Peng and Robinson [1976]) in combination with the Twu and Coon mixin g rule was used in the direct method. Thermodynamic consistency tests were done on all the systems measured. The point test (Van Ness et a!. [1973]) and the direct test Van Ness ([ 1995]) were used for consistency tests . The direct test could not be carried out on the carboxylic acids data because of the model's inability to adequately characterise the experimental activity coefficients. Generally the models fitted the data well but failed to accurately predict the "S" shape of the carboxylic acids phase diagrams. Considerable work still exists for further investigation into carboxylic acids. Currently, many experimentalists are working in this area . Penget a!. (2004) present ed their progress on developing an equation of state incorporating chemical theory to specifically handle carboxylic acids at the ICCT conference in Beijing, 2004. Raal and Clifford (University of Kwa-Zulu Natal, Thermodynamics Research Unit) are currently developing activity coefficient models incorporating chemical theory for a binary mixture of carboxylic acids. This work is part of the continuing research to under stand the phase behaviour of carboxylic acids. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.

The dynamic still originally designed by Raal (Raal and Muhlbauer [1998]) has been transformed into a valuable still that can now be used for measuring both low pressure vapour-liquid equilibria (VLE) for systems that are completely miscible and vapour-liquid-liquid equilibria (VLLE) for systems that are partially miscible. The resultant equilibrium data are important in the design and analysis of distillation and allied separation process equipment, with VLLE data, in particular, being useful in the design of heterogeneous azeotropic distillation columns. The original Raal still was based on the designs of Heertjies [1960] and Yerazunis [1964], who successfully used a packed equilibrium chamber where the liquid and vapour phases are forced downward co-currently to achieve rapid and dynamic equilibrium (Joseph et al [2001]). Direct analysis of the vapour composition prior to condensation through a new heated valving system with superheated sample conveyance to a gas chromatograph, a modification incorporated into the Raal still, ensured that accurate and reproducible equilibrium data were obtained. This new arrangement dispenses with the impossible task of getting the actual vapour composition that would result were the vapours allowed to condense and form two liquid phases. The initial testing of the still which established the operating procedures was conducted on two previously measured systems - the first which was homogeneous and the second heterogeneous. For the homogeneous system the new vapour sampling system was tested by comparing the measured composition to that of a condensed sample sent manually to the GC using a gas-tight syringe. In order to completely describe the VLLE for the systems studied, the liquid-liquid equilibrium (LLE) data for these systems were also measured. The LLE measurements were conducted in a newly-developed small jacketed glass cell with temperatures maintained constant by circulating water from a bath maintained at the desired temperatures. The main focus of this project was thus the development of an apparatus and procedures for measuring low pressure vapour-liquid-liquid equilibria. The project also went on to measuring and modeling VLE, VLLE and LLE data for selected binary and ternary systems. Both the Gamma-Phi and the Phi-Phi methods of VLE analysis were carried out on the measured data. The NRTL, Wilson, TK-Wi1son and UNIQUAC activity coefficient models were used in the Gamma- Phi method together with the Virial equation of state for vapour phase non-idealities. In the Phi-Phi method, The Peng and Robinson Equation of State (EOS), the Soave Redlich-Kwong EOS and the Stryjek and Vera modified Peng and Robinson EOS were all used, first with the classical mixing rules and then with the theoretically correct Wong and Sandler [1992] mixing rules. Ternary LLE binodal curves were correlated to the Hlavaty correlation, the beta function and the log gamma function while the corresponding tie-lines were fitted to the NRTL model. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.

The thermodynamic knowledge of accurate phase equilibrium data plays an important role in the design and optimization of separation processes in chemical and engineering industries. Vapour-liquid equilibrium data are essential for the design of efficient separation processes such as distillation. The presented research study is mainly focused on the vapour-liquid equilibrium data measurement of fluorochemical and hydrocarbon binary systems at various temperatures and at high pressures. A new static analytical apparatus was constructed and commissioned for the measurement of accurate and precise vapour-liquid equilibrium data at temperatures and absolute pressures ranging from low temperatures to 323.15 K and 0 to 10 MPa respectively. The new apparatus incorporates the ROLSI TM sampler, a sampling technique developed by the CEP/TEP laboratory in Fontainebleau, France. Isothermal high pressure VLE data were measured for three binary systems comprising of hexafluoroethane (R116) + propane, HFPO + propane and ethane + octafluoropropane (R218). The R116 + propane system at 263.15 K was measured as a test system using the new static apparatus. These measurements helped to confirm the functioning of the experimental apparatus. The reliability and the reproducibility of the experimental procedure were also checked. The data obtained were in excellent agreement with data in the literature. Thereafter, measurements of previously unmeasured systems were undertaken. Isothermal vapour-liquid equilibrium data measurements for the ethane + octafluoropropane system were performed at five isotherms with temperatures and pressures ranging from 264.05 to 308.04 K and 0.298 to 4.600 MPa respectively. The five isotherms constitute new experimental data. The HFPO + propane system was also investigated and vapour-liquid equilibrium data were measured at three isotherms (283.05, 303.05 and 323.05 K) with pressures ranging from 0.437 to 2.000 MPa. The data measured also constitute a set of a new HPVLE data. The uncertainties in the measurement for both systems were within ± 0.09 K, ± 0.0016 MPa and less than 2% for temperatures, pressures and mole fractions, respectively. All experimental data were correlated via the direct method using the Peng-Robinson equation of state with the Mathias-Copeman alpha function and the Wong-Sandler mixing rules incorporating the NRTL activity coefficient model. The consistency of the measured VLE data was tested using the Van Ness point test which yielded few points of difference between the measured and calculated data, suggesting a low error rate. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

This thesis involves a study of the thermodynamics of liquid mixtures containing N-methyl-2pyrrolidone (NMP) and hydrocarbons or ethers. NMP is a polar liquid which is used in liquid extraction procedures for the separation of polar and nonpolar hydrocarbons. It was considered important enough to devote an entire thesis to the properties of NMP related to its interactions with simple hydrocarbons and ethers. The thesis consists of four parts: Part one is devoted to liquid-liquid equilibria. Experimental results at 298.2 K, are presented for the mixtures: NMP + an aromatic hydrocarbon + an n-alkane. Firstly, the effect increasing the chain length of the alkane has on the liquid-liquid equilibria was investigated, by studying mixtures of the type: an n-alkane + toluene + NMP; where the n-alkane refers to n-hexane or n-nonane or n-tetradecane or n-hexadecane. Secondly, the effect of substitution on the benzene ring on the equilibria was studied by measuring the liquid-liquid equilibria for the mixtures: n-hexadecane + an aromatic hydrocarbon + NMP; where the aromatic hydrocarbon refers to toluene or o-xylene or m-xylene or p-xylene or mesitylene or ethyl benzene. The chain length of the n-alkane had a significant effect on the liquid-liquid equilibria. Methyl substitution on the benzene ring had a small effect on the liquid-liquid equilibria. Part two is devoted to activity coefficients at infinite dilution. Experimental results at 298,15 K, determined using gas-liquid chromatography, are presented for the mixtures: NMP (solvent) + n-pentane or n-hexane or n-heptane or n-octane or cyclopentane or cyclohexane or cycloheptane or I-hexene or 1-heptene or l-octene or diethyl ether or diisopropyl ether. The magnitudes of the infinite dilution activity coefficients had the following order: n-alkanes > cycloalkanes > l-alkenes > ethers. Part three is devoted to excess molar enthalpies. Experimental results at 298.15 K are presented for the mixtures: NMP + an aromatic hydrocarbon. Here, an aromatic hydrocarbon refers to one of benzene or toluene or o-xylene or m-xylene or p-xylene or mesitylene or ethyl benzene. Isothermal flow microcalorimetry was used to determine the excess molar enthalpies. Increased methyl substitution on the' benzene ring manifests itself as a reduction in the association between NMP and the aromatic hydrocarbon. Part four is devoted to excess molar volumes. Experimental results at 298.15 K are presented for the mixtures: NMP + an aromatic hydrocarbon. Here, an aromatic hydrocarbon refers to one of benzene or toluene or o-xylene or m-xylene or p-xylene or mesitylene or ethyl benzene. Densitometry was used to determine the excess molar volumes. The excess molar volumes were negative for all the mixtures. / Thesis (M.Sc.)-University of Natal, 1997.

Acetylpropionyl (2,3-pentanedione) and diacetyl (2,3-butanedione) are by-products of sugar manufacture. Both diketones have many uses, mainly food related. Vapour-liquid equilibrium data and infinite dilution activity coefficients are required to design purification processes for these chemicals. A review of available experimental methods revealed that the vapour and liquid recirculating still is most appropriate when both isobaric and isothermal VLE are required. The low-pressure dynamic still of Raal and Muhlbauer (1998) used in this study incorporates many features to ensure that measurements are of excellent quality (as demonstrated by Joseph et al., 2001). VLE measurements were made for the following systems: • Acetone with diacetyl at 30 C, 40 C, 50 C and 40 kPa • Methanol with diacetyl at 40 C, 50 C, 60 C and 40 kPa • Diacetyl with 2,3-pentanedione at 60 C, 70 C, 80 C and 40 kPa • Acetone with 2,3-pentanedione at 50 C, 30 kPa and 40 kPa. All the systems, except for methanol with diacetyl, displayed close to ideal behaviour. This was expected as they are mixtures of ketones. Solution thermodynamics allows one to perform data reduction of the measured VLE data to ensure accurate extrapolation and interpolation of the measurements. Furthermore, the quality of the data can be judged using thermodynamic consistency tests. The data were represented by the Gamma-Phi approach to VLE (the preferred method for low-pressure VLE computations). The two-term virial equation of state was used to account for vapour phase non-ideality. Second virial coefficients were calculated by the method of Hayden and 0'Connell (1975). The liquid phase non-ideality was accounted for by the Wilson, NRTL or UNIQUAC models. The best fit models are proposed for each system, as are parameters as functions of temperature for the isobaric data. The data were judged to be of high thermodynamic consistency by the stringent point test (Van Ness and Abbott, 1982) and the direct test (Van Ness, 1995) for thermodynamic consistency. The data sets were rated, at worst, "3" on the consistency index proposed by Van Ness (1995). A rating of "I" is given for a perfectly consistent data set and "10" for an unacceptable data set. For the system acetone with 2,3-pentanedione, isobars at 30 kPa and 40 kPa were measured. The results from the reduction of the 30 kPa set were used to accurately predict the 40 kPa data set. Infinite dilution activity coefficients were measured by the inert gas stripping method (based on the principle of exponential dilution). In order to specify the appropriate dilutor flask height (to ensure equilibrium is achieved), mass transfer considerations were made. These computations ensured that the gas phase was in equilibrium with the liquid phase at the gas exit point. The following infinite dilution activity coefficients were measured: • Acetone in diacetyl at 30 C • Methanol in diacetyl at 40 C • Diacetyl in 2,3-pentanedione at 60°C • Acetone in 2,3-pentanedione at 50 C. The ketone mixtures, once again, displayed close to ideal behaviour. / Thesis (M.Sc.)-University of Natal, Durban, 2003.

Experimental vapour-liquid equilibria (VLE) data is required for the design of separation / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.