Faculty of Engineering and Built Environment
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Item Vapor-liquid equilibrium data for binary systems of 1-Methyl-4-(1-methylethenyl)-cyclohexene plus {Ethanol, Propan-1-ol, Propan-2-ol, Butan-1-ol, Pentan-1-ol, or Hexan-1-ol} at 40 kPa(American Chemical Society (ACS), 2012-07) Ngema, Peterson Thokozani; Matkowska, Dobrochna; Naidoo, Paramespri; Hofman, Tadeusz; Ramjugernath, DereshIsobaric binary vapor-liquid equilibrium (VLE) data were measured for the 1-methyl-4-(1-methylethenyl)-cyclohexene (d-limonene) + {ethanol, propan-1-ol, propan-2-ol, butan-1-ol, pentan-1-ol, or hexan-1-ol} systems at 40 kPa. A low pressure dynamic still was used for the measurements. The experimental data were regressed using the nonrandom two-liquid (NRTL) and Wilson activity coefficient models. Both models correlated the data well. The 1-methyl-4-(1-methylethenyl)- cyclohexene + {butan-1-ol or pentan-1-ol or hexan-1-ol} systems exhibit a minimum temperature azeotrope. The 1-methyl-4-(1-methylethenyl)-cyclohexene + {ethanol or propan-1-ol or propan-2-ol} systems show the largest positive deviation from Raoult's law, and these systems exhibit no azeotropic behavior. © 2012 American Chemical Society.Item Infinite dilution activity coefficients and thermodynamic properties of selected organic solutes and water dissolved in 1, 6-hexanediol(Elsevier BV, 2020-12) Nkosi, Nkululeko; Tumba, Kaniki; Ngema, Peterson; Ramsuroop, SureshThe experimental activity coefficients (γ13∞) and gas-to-liquid partition coefficients (KL) at infinite dilution for 34 organic solutes and water were determined in 1.6-hexanediol (HDO) by the gas–liquid chromatography technique (GLC) in the temperature range from (323.15 to 353.15) K. Fundamental thermodynamic functions such as excess partial molar enthalpy (ΔHiE,(∞)), excess partial molar Gibbs energy, (ΔGiE,∞) and entropy, (TrefΔSiE,∞) at infinite dilution were calculated from experimental values of γ13∞. Reported data were discussed in terms of solvent-solute interactions, heat effects and mixing spontaneity. Selectivity (Sij∞) and capacity (kj∞) related to different separation problems were calculated from γ13∞ data and compared to the literature values for selected ionic liquids (ILs), deep eutectic solvents (DESs) and industrial solvents. New data reported in this study suggest that HDO may be proposed as an alternative solvent for the separation of alkanes-pyridine and alkanes-thiophene systems. Furthermore, it was found that adding a hydrogen bond acceptor to HDO enhances its performance as a separation solvent.Item Thermodynamic stability conditions of clathrate hydrates for refrigerant (R134a or R410a or R507) with MgCl2 aqueous solution(Elsevier BV, 2016-04-15) Ngema, Peterson Thokozani; Naidoo, Paramespri; Mohammadi, Amir H.; Richon, Dominique; Ramjugernath, DereshClathrate hydrate dissociation data were measured for systems comprising of refrigerants (R134a, R410a and R507) + water + MgCl2 at varying salt concentrations. The ternary system for R134a + water + MgCl2 was measured at salt concentrations of (0.259, 0.546, and 0.868) mol.kg-1 in the temperature range of (277.1-283) K and a pressure range of (0.114-0.428) MPa. Hydrate measurements for the {R410a or R507} + water + MgCl2 systems were measured at salt concentrations of (0.259 and 0.546) mol.kg-1 in the temperature range of (274.3-293) K and a pressure range of (0.154-1.421) MPa. The isochoric pressure-search method was used to measure the hydrate dissociation data. This study is a continuation of previous investigations which focused on obtaining hydrate dissociation data for R134a, R410a and R507 refrigerants in NaCl and CaCl2 aqueous solutions. The measured hydrate dissociation data can be used to design industrial wastewater treatment and desalination processes. The results show that the effect of salt concentration on hydrate formation is smaller for MgCl2 aqueous solutions compared to CaCl2 and NaCl as salt concentration increases. Modelling of the measured data is performed using a combination of the solid solution theory of van der Waals and Platteeuw, the Aasberg-Petersen et al. model, and the Peng-Robinson equation of state with classical mixing rules. The model is in good agreement with the measured hydrate dissociation data.Item Vapor-liquid equilibrium data for binary systems of n-Dodecane + {Propan-1-ol, Butan-1-ol, 2-Methylpropan-1-ol} at 40 kPa(American Chemical Society (ACS), 2014-05) Tebbal, Zoubir; Ngema, Peterson Thokozani; Narasigadu, Caleb; Negadi, Latifa; Ramjugernath, DereshIsobaric (T-x-y) binary vapor-liquid equilibrium (VLE) data were measured and modeled for the n-dodecane + {propan-1-ol, butan-1-ol, or 2-methylpropan-1-ol} systems at 40 kPa. A low pressure dynamic still, capable of measuring systems of high relative volatility, was used for the measurements. The vapor and liquid equilibrium compositions were determined using a gas chromatograph with a thermal conductivity detector. The experimental data were regressed using the combined method (γ-φ approach). The nonrandom two-liquid (NRTL) activity coefficient model was used to describe the liquid phase nonideality, and the vapor phase was assumed to be ideal. The NRTL model parameters were determined using nonlinear least-squares regression. The experimental data were found to be well correlated with the thermodynamic modeling. No azeotropic behavior has been observed. The three investigated systems show a large positive deviation from Raoult's law. © 2014 American Chemical Society.Item Vapor-liquid equilibrium data for binary systems of 1H-Pyrrole with Butan-1-ol, Propan-1-ol, or Pentan-1-ol(American Chemical Society (ACS), 2012-09) Zawadzki, Maciej; Ngema, Peterson Thokozani; Domanska, Urszula; Naidoo, Paramespri; Ramjugernath, DereshIsobaric and isothermal vapor-liquid equilibrium (VLE) data are presented for binary systems comprising 1H-pyrrole (pyrolle) with light alcohols. The systems measured include 1H-pyrrole + butan-1-ol at 40 kPa and T = (353.2, 363.2, and 373.2) K; 1H-pyrrole + propan-1-ol at 40 kPa and T = (348.2, 358.2, and 368.2) K; and 1H-pyrrole + pentan-1-ol at 40 kPa and T = (353.2, 363.2, and 373.2) K. Measurements were undertaken on a low-pressure dynamic still, with analysis of the equilibrium samples by gas chromatography. The 1H-pyrolle + butan-1-ol and 1H-pyrolle + pentan-1-ol systems exhibited azeotropic behavior for both the isobaric and the isothermal measurements. The measured data were modeled using the Wilson and nonrandom two-liquid (NRTL) excess Gibbs energy models, with both models correlating the data well. © 2012 American Chemical Society.Item Infinite dilution activity coefficient measurements for 1-Methyl-4-(1-methylethenyl)-cyclohexene as a green solvent for separation(American Chemical Society (ACS), 2022-04-14) Mbatha, Banzi Patrick; Ngema, Peterson Thokozani; Nkosi, Nkululeko; Ramsuroop, SureshInfinite dilution activity coefficients for various solutes, which include alkanes, alkenes, alkynes, cycloalkanes, heterocycles, alcohols, aromatics, ketones, ethers, nitrile, and water, in a 1-methyl-4-(1-methylethenyl)-cyclohexene solvent were measured using gas-liquid chromatography at 303.15, 313.15, and 323.15 K. The focus of this study was to assess 1-methyl-4-(1-methylethenyl)-cyclohexene as a green solvent for separation processes. 1-Methyl-4-(1-methylethenyl)-cyclohexene, a nonpolar monoterpene solvent extracted from essential oils of citrus peels, was investigated as an alternative solvent to currently employed conventional organic solvents in separation processes. Through experimental infinite dilution activity coefficients, γ13∞, the values of partial molar excess enthalpy at infinite (δHiE,∞) were obtained using the Gibbs-Helmholtz equation. The infinite dilution selectivity (Sij∞) and capacity (δkj∞) values were calculated from the experimental limiting activity coefficients and were compared with deep eutectic solvents, ionic liquids, and industrial solvents. From this study, it was observed that 1-methyl-4-(1-methylethenyl)-cyclohexene is not suitable to be used as an alternative for separation processes. In addition, activity coefficients at infinite dilution of different organic solutes in hexadecane were measured at various temperatures to validate the reliability and accuracy of gas-liquid chromatography. Finally, the experimental data were modeled using Aspen Plus, compared with experimental data, and found to be in good agreement.Item Phase stability conditions for clathrate hydrate formation in (fluorinated refrigerant plus water plus single and mixed electrolytes plus cyclopentane) systems : experimental measurements and thermodynamic modelling(Elsevier BV, 2019-09) Ngema, Peterson Thokozani; Naidoo, Paramespri; Mohammadi, Amir H.; Ramjugernath, DereshPhase equilibrium conditions (dissociation data) for clathrate hydrates (gas hydrates) were studied for systems involving fluorinated refrigerants + water + single and mixed electrolytes (NaCl, CaCl2, MgCl2 and Na2SO4) at varying salt concentrations in the absence and presence of cyclopentane (CP). The ternary systems for (R410a or R507) + water + CP were performed in the temperature and pressures ranges of (279.8–294.4) K and (0.158–1.385) MPa, respectively. Measurements for {R410a + water + (NaCl or CaCl2) + CP} were undertaken at salt concentrations of (0.10, 0.15 and 0.20) mass fractions in the temperature and pressure ranges of (278.4–293.7) K and (0.214–1.179) MPa, respectively. The temperature and pressure conditions for the (R410a + water + Na2SO4) system were investigated at salt concentration of 0.10 mass fraction in range of (283.3–291.6) K and (0.483–1.373) MPa respectively. Measurements for {(R410a or R507) + water + mixed electrolytes NaCl, CaCl2, MgCl2} were undertaken at various salt concentrations of (0.002–0.15) mass fractions in the temperature and pressure ranges of (274.5–292.9) K and (0.149–1.119) MPa in the absence and presence of CP, for which there are no published data related to mixed salt and a promoter. The phase equilibrium measurements were performed using a non-visual isochoric equilibrium cell and the pressure-search technique. This study was focused on obtaining equilibrium data that can be utilized to design and optimize for water desalination process and the development of a Hydrate Electrolyte–Cubic Plus Association (HE–CPA) Equation of State based model. The results indicate hydrate dissociation pressure reduction/hydrate dissociation temperature increase up to ambient conditions in the presence of promoter (CP). The experimental results were then modelled. The modelling results are in good agreement with the measured hydrate dissociation data.