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In this study, the pollution levels, sources, and ecological risks associated with five selected heavy metals (chromium, copper, iron, lead, and zinc)were evaluated in surface water, soil, and sediment systems along the Isipingo River, KwaZulu-Natal, South Africa. The surface water, soil and sediment samples collected along the river, were preserved, transported, and stored followed the standard procedures. Soil and sediment samples were digested for heavy metal determination using a microwave digestion system. The digested samples were quantitatively analysed using an inductively coupled plasma optical emission spectrometer (ICP-OES). The results demonstrate that majority of the targeted heavy metals were found below the detection limits in surface water except for iron (Fe), which was found within the concentration range of 9.54 to 46.76 µg/L. Lead was found below the detection limit in water, soil, and sediment samples, while other heavy metals were within the range not detected(ND)to 0.222 µg/kg dry weight and 0.212 µg/kg dry weight in soil and sediment respectively. The ecological risk assessment of the studied metals in soil and sediment systems from this riversignified that water from this river had less probable potential adverse effects on both animals and humans as well as benthic organisms.
Gbadebo Clement Adeyinka; Babatunde Femi Bakare; Samuel Ayodele Iwarere. Evaluation and risk assessment of heavy metals in surface water collected along the Isipingo River, KwaZulu-Natal, South Africa. International Journal of Environmental Analytical Chemistry 2021, 1 -17.
AMA StyleGbadebo Clement Adeyinka, Babatunde Femi Bakare, Samuel Ayodele Iwarere. Evaluation and risk assessment of heavy metals in surface water collected along the Isipingo River, KwaZulu-Natal, South Africa. International Journal of Environmental Analytical Chemistry. 2021; ():1-17.
Chicago/Turabian StyleGbadebo Clement Adeyinka; Babatunde Femi Bakare; Samuel Ayodele Iwarere. 2021. "Evaluation and risk assessment of heavy metals in surface water collected along the Isipingo River, KwaZulu-Natal, South Africa." International Journal of Environmental Analytical Chemistry , no. : 1-17.
This study explored Fischer–Tropsch synthesis (FTS) by combining a non-thermal plasma (NTP), generated by an arc discharge reactor at pressures >> 1 MPa, coupled with a mullite-coated 2 wt%-Co/5 wt%-Al2O3 catalyst. The FTS product yields and electrical energy consumption for the pure plasma (no catalyst) and plasma-catalytic FTS processes were compared under the scope of various reactor operating parameters, namely, pressure (0.5 to 10 MPa), current (250 to 450 mA) and inter-electrode gap (0.5 to 2 mm). The major products, obtained in low concentrations for both processes, were gaseous C1–C3 hydrocarbons, synthesised in the order: methane >> ethane > ethylene > propane. The hydrocarbon product yields were observed to increase, while the specific required energy generally decreased with increasing pressure, decreasing current and increasing inter-electrode gap. Plasma-catalysis improved the FTS performance, with the optimum conditions as: (i) 10 MPa at 10 s and 2 MPa at 60 s for the pressure variation study with the longer treatment time producing higher yields; (ii) 250 mA for the current variation study; (iii) 2 mm for the inter-electrode gap variation study. Plasma-catalysis at a gap of 2 mm yielded the highest concentrations of methane (15,202 ppm), ethane (352 ppm), ethylene (121 ppm) and propane (20 ppm), thereby indicating the inter-electrode gap as the most influential parameter.
Byron Govender; Samuel Iwarere; Deresh Ramjugernath. Plasma-Catalytic Fischer–Tropsch Synthesis at Very High Pressure. Catalysts 2021, 11, 297 .
AMA StyleByron Govender, Samuel Iwarere, Deresh Ramjugernath. Plasma-Catalytic Fischer–Tropsch Synthesis at Very High Pressure. Catalysts. 2021; 11 (3):297.
Chicago/Turabian StyleByron Govender; Samuel Iwarere; Deresh Ramjugernath. 2021. "Plasma-Catalytic Fischer–Tropsch Synthesis at Very High Pressure." Catalysts 11, no. 3: 297.
A thermo-chemical treatment method was used to produce biogenic amorphous silica from South African sugarcane and maize residues. Different fractions of South African sugarcane (leaves, pith, and fiber) were processed for silica production. The biomass samples were leached with either 7 wt% citric acid or 7 wt% sulfuric acid at 353 K for 2 h prior to being rinsed, dried and combusted using a four-step program ranging from room temperature to 873 K in a furnace. The characterization of the pre-treated biomass samples was conducted using thermogravimetric analysis (TG/DTA), X-ray fluorescence analysis (XRF) and elemental analysis (CHN), while the final products were characterized by XRF, X-ray diffraction (XRD), elemental analysis, nitrogen physisorption and scanning electron microscopy (SEM). Citric acid pre-treatment proved to be an attractive alternative to mineral acids. Amorphous biogenic silica was produced from sugarcane leaves in good quality (0.1 wt% residual carbon and up to 99.3 wt% silica content). The produced biogenic silica also had great textural properties such as a surface area of up to 323 m2 g−1, average pore diameter of 5.0 nm, and a pore volume of 0.41 cm3 g−1.
Ncamisile Nondumiso Maseko; Denise Schneider; Susan Wassersleben; Dirk Enke; Samuel Ayodele Iwarere; Jonathan Pocock; Annegret Stark. The Production of Biogenic Silica from Different South African Agricultural Residues through a Thermo-Chemical Treatment Method. Sustainability 2021, 13, 577 .
AMA StyleNcamisile Nondumiso Maseko, Denise Schneider, Susan Wassersleben, Dirk Enke, Samuel Ayodele Iwarere, Jonathan Pocock, Annegret Stark. The Production of Biogenic Silica from Different South African Agricultural Residues through a Thermo-Chemical Treatment Method. Sustainability. 2021; 13 (2):577.
Chicago/Turabian StyleNcamisile Nondumiso Maseko; Denise Schneider; Susan Wassersleben; Dirk Enke; Samuel Ayodele Iwarere; Jonathan Pocock; Annegret Stark. 2021. "The Production of Biogenic Silica from Different South African Agricultural Residues through a Thermo-Chemical Treatment Method." Sustainability 13, no. 2: 577.
The present study entails investigating the fractional devolatilisation effect on the passenger car tyre (PCT) and truck tyre (TT). Thermograms and their first derivatives are used to profile devolatilisation of the passenger and truck tyres rubbery fractions. Both tyre types rubbery fractions consist of mainly natural rubber (or polyisoprene, NR) and synthetic rubber (polybutadiene, BR and styrene-butadiene, SBR). The NR is relatively significant compared to the BR and SBR in the TT. In the PCT, the rubbery fraction showed equal distributions between the NR and BR-SBR. Unlike conventional waste resources pyrolysis processes where the aim is towards energy recovery, novel pyrolysis is designed based on the characteristics of the materials in order to promote the production of the valuable products in addition to the energy recovery. Therefore, kinetic mechanisms pathways of the rubbery fraction devolatilisation from waste tyre pyrolysis are studied and models are developed. Model-free methods, such as Friedman and Kissinger are used to model the kinetics parameters.
Samuel Ayodele Iwarere; Ntandoyenkosi Malusi Mkhize. PYROLYSIS OF VARIOUS TYRE TYPES: CHARACTERISTICS AND KINETIC STUDIES USING THERMOGRAVIMETRIC ANALYSIS. Detritus 2019, 165 -173.
AMA StyleSamuel Ayodele Iwarere, Ntandoyenkosi Malusi Mkhize. PYROLYSIS OF VARIOUS TYRE TYPES: CHARACTERISTICS AND KINETIC STUDIES USING THERMOGRAVIMETRIC ANALYSIS. Detritus. 2019; (9):165-173.
Chicago/Turabian StyleSamuel Ayodele Iwarere; Ntandoyenkosi Malusi Mkhize. 2019. "PYROLYSIS OF VARIOUS TYRE TYPES: CHARACTERISTICS AND KINETIC STUDIES USING THERMOGRAVIMETRIC ANALYSIS." Detritus , no. 9: 165-173.
2,3-Pentanedione, acetaldehyde, and acetone are by-products found downstream in the sugar manufacturing process. 2,3-Pentanedione has various food and industrial-related uses, making it a product of interest. It can be recovered using extractive distillation recovery processes, whereby chemicals of similar boiling points are separated. Vapor–liquid equilibrium (VLE) measurements were conducted isobarically for the systems 2,3-pentanedione + {acetaldehyde or acetone} at 100, 150, and 200 kPa. Measurements were undertaken using a moderate pressure recirculating VLE still, capable of withstanding pressures up to 350 kPa. The measured VLE data were regressed using the gamma–phi (γ–φ) approach and the nonrandom two-liquid activity coefficient model, which displayed satisfactory representation of the system behavior. None of the binary systems exhibit azeotropic behavior. All the binary systems displayed a positive deviation from Raoult’s law.
Sivanna Naicker; Samuel A. Iwarere; Paramespri Naidoo; Deresh Ramjugernath. Vapor Liquid Equilibrium Data for 2,3-Pentanedione + (Acetaldehyde or Acetone) at (100, 150, and 200) kPa. Journal of Chemical & Engineering Data 2019, 64, 2388 -2394.
AMA StyleSivanna Naicker, Samuel A. Iwarere, Paramespri Naidoo, Deresh Ramjugernath. Vapor Liquid Equilibrium Data for 2,3-Pentanedione + (Acetaldehyde or Acetone) at (100, 150, and 200) kPa. Journal of Chemical & Engineering Data. 2019; 64 (6):2388-2394.
Chicago/Turabian StyleSivanna Naicker; Samuel A. Iwarere; Paramespri Naidoo; Deresh Ramjugernath. 2019. "Vapor Liquid Equilibrium Data for 2,3-Pentanedione + (Acetaldehyde or Acetone) at (100, 150, and 200) kPa." Journal of Chemical & Engineering Data 64, no. 6: 2388-2394.
New isothermal binary vapor–liquid equilibrium (VLE) systems of 1-pentanol + 2,2,4-trimethylpentane at 350.2, 360.2, and 370.2 K, methyl-tert-butyl-ether + 2,2,4-trimethylpentane at 307.2, 317.2, and 327.2 K, and methyl-tert-butyl-ether + 1-pentanol at 317.2 and 327.2 K were measured. The vapor–liquid equilibrium data were measured using a dynamic low pressure glass still. The experimental data were regressed using the γ–Φ approach (combined method) with the Wilson, NRTL, and UNIQUAC activity coefficient models for description of the liquid phase nonideality. The virial equation of state with the Hayden and O’Connell correlation for the second virial coefficient was used to describe the vapor phase nonideality. The system of 2,2,4- trimethylpentane + 1-pentanol exhibited a minimum boiling azeotrope. The methyl-tert-butyl-ether + (2,2,4-trimethylpentane/1-pentanol) systems showed positive deviation from Raoult’s law. The aforementioned activity coefficient models correlated the experimental data well. The thermodynamic consistency of the experimental data was determined using the point test of Van Ness and the Herrington area test.
Travis Pio Benecke; Caleb Narasigadu; Samuel A. Iwarere; Wayne M. Nelson; Deresh Ramjugernath. Vapor–Liquid Equilibrium Measurements of Ether Alcohol Blends for Investigation on Reformulated Gas. Journal of Chemical & Engineering Data 2018, 64, 115 -123.
AMA StyleTravis Pio Benecke, Caleb Narasigadu, Samuel A. Iwarere, Wayne M. Nelson, Deresh Ramjugernath. Vapor–Liquid Equilibrium Measurements of Ether Alcohol Blends for Investigation on Reformulated Gas. Journal of Chemical & Engineering Data. 2018; 64 (1):115-123.
Chicago/Turabian StyleTravis Pio Benecke; Caleb Narasigadu; Samuel A. Iwarere; Wayne M. Nelson; Deresh Ramjugernath. 2018. "Vapor–Liquid Equilibrium Measurements of Ether Alcohol Blends for Investigation on Reformulated Gas." Journal of Chemical & Engineering Data 64, no. 1: 115-123.
Isothermal vapor–liquid equilibrium (VLE) data were measured for binary mixtures of 2-pentanone + 2-methylpropan-1-ol at (343.15, 358.15, and 363.15) K. A glass dynamic recirculating still suitable for a subatmospheric to atmospheric pressure range was used for the VLE measurements. The excess thermodynamic properties, namely, the molar excess Gibbs energy (GE), heat of mixing (HE), and molar excess entropy (SE) were derived from the measured isothermal VLE data. The calculated infinite dilution activity coefficients for the system are also presented. The measured isothermal VLE data for the binary system was regressed using the gamma–phi (γ–Φ) approach. The Wilson and the nonrandom two-liquid (NRTL) activity coefficient models were employed for the data regression, while the Hayden and O’Connell correlation was used to account for the nonidealities in the vapor phase. Satisfactory results were obtained using the Wilson and NRTL models to represent the measured data. The measured VLE data were considered to be thermodynamically consistent following the point test of Van Ness et al. (Van Ness, H. C.; Byer, S. M.; Gibbs, R. E. AIChE J. 1973, 19, 238–244) and the more rigorous direct test (Van Ness, H. C. Pure Appl. Chem. 1995, 67, 859–872).
Funmilola Avoseh; Samuel A. Iwarere; Caleb Narasigadu; Deresh Ramjugernath. Isothermal Vapor–Liquid Equilibrium for the 2-Pentanone (MPK) + 2-Methyl Propan-1-ol Binary Mixture. Journal of Chemical & Engineering Data 2018, 63, 4076 -4084.
AMA StyleFunmilola Avoseh, Samuel A. Iwarere, Caleb Narasigadu, Deresh Ramjugernath. Isothermal Vapor–Liquid Equilibrium for the 2-Pentanone (MPK) + 2-Methyl Propan-1-ol Binary Mixture. Journal of Chemical & Engineering Data. 2018; 63 (11):4076-4084.
Chicago/Turabian StyleFunmilola Avoseh; Samuel A. Iwarere; Caleb Narasigadu; Deresh Ramjugernath. 2018. "Isothermal Vapor–Liquid Equilibrium for the 2-Pentanone (MPK) + 2-Methyl Propan-1-ol Binary Mixture." Journal of Chemical & Engineering Data 63, no. 11: 4076-4084.
Isothermal vapor–liquid equilibrium (VLE) data for 1-propanol + methyl isobutyl ketone at 338.15, 353.15, and 368.15 K and 2-propanol + methyl isobutyl ketone were measured at 323.15, 338.15, and 353.15 K. All the measurements were undertaken on a recirculating VLE glass still operated at isothermal conditions. The experimental VLE data for all the measured binary systems were correlated with the Wilson and NRTL activity coefficient models using the gamma–phi approach (γ–Φ) with the Hayden and O’Connell correlation employed for calculating the second virial coefficients that are used in accounting for nonidealities in the vapor phase. The models provided satisfactory correlation of the measured alcohol–ketone-binary mixtures at all the temperatures reported. The thermodynamic consistency of the data was checked using the point test method of Van Ness et al. (Van Ness, H. C., Byer, S. M., and Gibbs, R. E.AIChE J.1973, 19, 238−244) as well as the more rigorous direct test of Van Ness (Van Ness, H. C.Pure Appl. Chem.1995, 67, 859−872).
Funmilola Avoseh; Samuel A. Iwarere; Caleb Narasigadu; Deresh Ramjugernath. Vapor–Liquid Equilibrium for Methyl Isobutyl Ketone (MIBK) + (1-Propanol or 2-Propanol) Binary Mixtures. Journal of Chemical & Engineering Data 2017, 62, 2014 -2020.
AMA StyleFunmilola Avoseh, Samuel A. Iwarere, Caleb Narasigadu, Deresh Ramjugernath. Vapor–Liquid Equilibrium for Methyl Isobutyl Ketone (MIBK) + (1-Propanol or 2-Propanol) Binary Mixtures. Journal of Chemical & Engineering Data. 2017; 62 (7):2014-2020.
Chicago/Turabian StyleFunmilola Avoseh; Samuel A. Iwarere; Caleb Narasigadu; Deresh Ramjugernath. 2017. "Vapor–Liquid Equilibrium for Methyl Isobutyl Ketone (MIBK) + (1-Propanol or 2-Propanol) Binary Mixtures." Journal of Chemical & Engineering Data 62, no. 7: 2014-2020.
Carbon dioxide (CO2) is regarded as one of the arch villains in the long debate on global warming, or what has now been more correctly termed climate change, as it accounts for approximately 85 % of the total greenhouse gases that are emitted annually. The majority of sources are from the combustion of fossil fuels. With a growing global population and consequently a growing demand for energy, there has been extensive research on alternative fuels and energy sources, as well technologies for the combustion of fossil fuels. In order to mitigate the environmental effects of carbon dioxide, numerous strategies have been proposed which focus on limitation of emissions from sources, capture, and degradation. Carbon dioxide in theory could be a potential feedstock for the production of fuel, energy, and value-added chemicals. In effect, carbon dioxide could be turned from a villain to a hero, i.e. producing energy while reducing greenhouse gases. It is therefore important that researchers continue to look for practically feasible, inexpensive, environmentally friendly, and energy efficient technologies that can utilize CO2 by converting it into energy, liquid hydrocarbon fuels, and value-added chemicals. This review presents the current state of the art in this regard, with emphasis on technological improvements to make carbon dioxide a viable feedstock for energy and value-added chemical production.
Samuel Iwarere; Deresh Ramjugernath. Carbon Dioxide to Energy: Killing Two Birds with One Stone. Energy Engineering 2016, 93 -103.
AMA StyleSamuel Iwarere, Deresh Ramjugernath. Carbon Dioxide to Energy: Killing Two Birds with One Stone. Energy Engineering. 2016; ():93-103.
Chicago/Turabian StyleSamuel Iwarere; Deresh Ramjugernath. 2016. "Carbon Dioxide to Energy: Killing Two Birds with One Stone." Energy Engineering , no. : 93-103.
Isothermal vapour-liquid equilibrium (VLE) data were measured for 2-propanone + 2-butanol at (333.15 and 353.15) K and 2-propanone + propanoic acid at (333.15, 353.15, and 373.15) K. For the sub-atmospheric pressure measurements, a dynamic recirculating VLE glass still operated isothermally was used, whilst a novel recirculating stainless steel of similar architecture, capable of operating at pressures up to 750 kPa was used for measurements above atmospheric pressures. The experimental VLE data for the 2-propanone + 2-butanol system at (333.15 and 353.15) K were correlated to the Wilson and NRTL models using the gamma-phi approach with the Hayden and O'Connell correlation employed for calculating the second virial coefficients. For the 2-propanone + propanoic acid system, the considerably more complex iterative procedure of Prausnitz et al. [J.M. Prausnitz, T.F. Anderson, E.A. Grens, C.A. Eckert, R. Hsieh, J.P. O'Connell, Computer Calculations for Multicomponent Vapour-Liquid and Liquid-Liquid Equilibrium, Prentice- Hall, New Jersey, 1980] was utilized to account for acid dimerization in the vapour phase. In the computational procedure for finding liquid phase activity coefficients, true species vapour phase mole fractions (ηi) are solved for, with the equilibrium association constant, Ki emerging from the computations. The thermodynamic consistency of the data was verified through the point and direct test methods of Van Ness.
Jeremy Pillay; Samuel Iwarere; J. David Raal; Paramespri Naidoo; Deresh Ramjugernath. Isothermal vapour-liquid equilibrium data for the binary systems 2-propanone + (2-butanol or propanoic acid). Fluid Phase Equilibria 2016, 433, 119 -125.
AMA StyleJeremy Pillay, Samuel Iwarere, J. David Raal, Paramespri Naidoo, Deresh Ramjugernath. Isothermal vapour-liquid equilibrium data for the binary systems 2-propanone + (2-butanol or propanoic acid). Fluid Phase Equilibria. 2016; 433 ():119-125.
Chicago/Turabian StyleJeremy Pillay; Samuel Iwarere; J. David Raal; Paramespri Naidoo; Deresh Ramjugernath. 2016. "Isothermal vapour-liquid equilibrium data for the binary systems 2-propanone + (2-butanol or propanoic acid)." Fluid Phase Equilibria 433, no. : 119-125.
Over the last two decades there has been growing research interest in the oxidative reforming of methane using carbon dioxide (CO2), with the aim of producing syngas (mixture of H2 and CO) which can be converted to synthetic fuels via the Fischer–Trospch process. Among the different options investigated, non-thermal plasma technology is considered to have a high potential for natural gas to syngas (and higher hydrocarbons) conversion at relatively lower energy consumption and cost. While many studies on plasma dry reforming of methane have been carried out over the years using different non-thermal plasma technologies, almost all these studies have been undertaken at near-atmospheric pressure. The aim of this paper is to study the influence of the pressure on the plasma dry reforming of methane. For this purpose, a tip–tip plasma batch-reactor connected to a high voltage direct current power supply has been used. This reactor has a maximum pressure limit of 20 MPa. All experiments were carried out with a CH4/CO2 reactant gas ratio of 1.8, a current of 350 mA, an interelectrode gap of 0.4 mm, and discharge duration of 60 s. The results presented in this paper show the variation of the concentration of the different obtained products: CO, H2, C2 and C3 hydrocarbons versus the operating pressure. From these results, the selectivity, chemical yield, H2/CO ratios and energy balances have been determined. The results from this study are compared to other plasma dry reforming studies in the literature. The high pressure reactor shows a high potential in terms of energy efficiency despite the low conversion due to the specific energy consumed by the reactant and the small discharge volume. The conversion could possibly be improved by increasing the interelectrode gap, and thus create a larger arc discharge reaction zone.
Samuel A. Iwarere; Vandad-Julien Rohani; Deresh Ramjugernath; Laurent Fulcheri. Dry reforming of methane in a tip–tip arc discharge reactor at very high pressure. International Journal of Hydrogen Energy 2015, 40, 3388 -3401.
AMA StyleSamuel A. Iwarere, Vandad-Julien Rohani, Deresh Ramjugernath, Laurent Fulcheri. Dry reforming of methane in a tip–tip arc discharge reactor at very high pressure. International Journal of Hydrogen Energy. 2015; 40 (8):3388-3401.
Chicago/Turabian StyleSamuel A. Iwarere; Vandad-Julien Rohani; Deresh Ramjugernath; Laurent Fulcheri. 2015. "Dry reforming of methane in a tip–tip arc discharge reactor at very high pressure." International Journal of Hydrogen Energy 40, no. 8: 3388-3401.
In this paper, the behaviour of a tetrafluoromethane (CF4) plasma arc under conditions of low current (0.25–0.4 A) and very high pressure (10 and 50 atm) in a batch reactor is presented using a three-dimensional magnetohydrodynamic model. Our previous study provided an understanding to the influence of pressure on the experimentally observed instabilities in the horizontal configuration. For a deeper understanding of the influence of other plasma operating parameters on the instabilities observed for pure CF4, the interelectrode gap, as well as the operating current was investigated in this study. The interelectrode distance is investigated since, experimentally, the longer the arc, the more unstable. In case of a stable arc, it has been observed with the model that a higher pressure and a higher interelectrode distance leads to higher values in terms of quantity of gas treated and volumetric power; two parameters of significant interest to improve the efficiency of the process. In order to validate the results of the previous paper, original experiments were carried out successfully in a vertical configuration at pressures ranging from 10 to 50 atm. Indeed, the horizontal configuration does not permit the ignition of the arc discharge for pure CF4 at pressure higher than 3 atm. Thus, the potential of the high-pressure arc discharge for pure CF4 using the vertical configuration against the horizontal configuration is demonstrated.
A. Lebouvier; S. A. Iwarere; D. Ramjugernath; Laurent Fulcheri. MHD Modeling of the Tip-to-Plane Plasma Arc Behaviour at Very High Pressure in CF4. Plasma Chemistry and Plasma Processing 2014, 35, 91 -106.
AMA StyleA. Lebouvier, S. A. Iwarere, D. Ramjugernath, Laurent Fulcheri. MHD Modeling of the Tip-to-Plane Plasma Arc Behaviour at Very High Pressure in CF4. Plasma Chemistry and Plasma Processing. 2014; 35 (1):91-106.
Chicago/Turabian StyleA. Lebouvier; S. A. Iwarere; D. Ramjugernath; Laurent Fulcheri. 2014. "MHD Modeling of the Tip-to-Plane Plasma Arc Behaviour at Very High Pressure in CF4." Plasma Chemistry and Plasma Processing 35, no. 1: 91-106.
This work presents the study of the synthesis of higher fluorocarbons from tetrafluoromethane (CF4) with a plasma process based on the generation of a tip–tip electrical discharge at very high pressure. A series of experiments were performed using a He/CF4 mixture with a ratio 60/40% at a pressure of 2 MPa to investigate the effects of two modes of treatment: a continuous mode and an intermittent mode including a 30 s relaxation time between two successive discharges. The study shows the production of low quantities of saturated fluorocarbons (C2F6 and C3F8) at the experimental conditions employed. It also shows the intermittent mode of treatment to be more efficient in the synthesis of the saturated C2 and C3 fluorocarbon molecules in comparison to the continuous mode. The continuous treatment mode leads to unfavorable kinetics of synthesis for a given discharge duration while the intermittent treatment mode leads to an increase of higher fluorocarbon production with the number of discharges.
Samuel A. Iwarere; Alexandre Lebouvier; Laurent Fulcheri; Deresh Ramjugernath. Experimental study on the formation of higher fluorocarbons from CF4 by a tip–tip electrical arc discharge at very high pressure. Journal of Fluorine Chemistry 2014, 166, 96 -103.
AMA StyleSamuel A. Iwarere, Alexandre Lebouvier, Laurent Fulcheri, Deresh Ramjugernath. Experimental study on the formation of higher fluorocarbons from CF4 by a tip–tip electrical arc discharge at very high pressure. Journal of Fluorine Chemistry. 2014; 166 ():96-103.
Chicago/Turabian StyleSamuel A. Iwarere; Alexandre Lebouvier; Laurent Fulcheri; Deresh Ramjugernath. 2014. "Experimental study on the formation of higher fluorocarbons from CF4 by a tip–tip electrical arc discharge at very high pressure." Journal of Fluorine Chemistry 166, no. : 96-103.
Isothermal vapour–liquid equilibrium (VLE) data were measured for alcohol–carboxylic acid systems using a dynamic recirculating apparatus operated isothermally. For super-atmospheric pressures, a stainless steel version of the apparatus was used with sight glasses in the Cottrell pump and liquid and condensate sampling chambers to observe flow patterns. Data are presented for 2-propanol + butyric acid, 2-butanol + butyric acid, and 2-methyl-1-propanol + butyric acid at 333.15 K, 353.15 K, and 373.15 K. To account for vapour phase non-ideality the iterative procedure of Prausnitz et al. [J.M. Prausnitz, T.F. Anderson, E.A. Grens, C.A. Eckert, H. Seih, J.P. O’Connell, Multicomponent Vapor–Liquid and Liquid–Liquid Equilibria, Prentice Hall, Englewood Cliffs, NJ, 1980], based on the chemical theory and corresponding states correlations, was used to obtain true species concentrations, association constants (Kii), and from these liquid phase activity coefficients. The Lewis fugacity rule was used for the true species fugacity coefficient. For the low pressures and moderate temperatures of the study, only dimerization of the acid in the vapour phase was considered. Satisfactory modelling of the data was obtained with the NRTL equation and also, for the direct (EOS) method, with the cubic-based Soave–Redlich–Kwong equation of state and the Wong–Sandler mixing rules. The high non-ideality of the vapour phase for the mixtures studied was confirmed by the considerable departure of the vapour phase correction factors, Φi, from unity. The thermodynamic consistency of the data is shown by the area test and the more rigorous Van Ness point and direct tests.
Samuel A. Iwarere; J. David Raal; Paramespri Naidoo; Deresh Ramjugernath. Vapour–liquid equilibrium of carboxylic acid–alcohol binary systems: 2-Propanol+butyric acid, 2-butanol+butyric acid and 2-methyl-1-propanol+butyric acid. Fluid Phase Equilibria 2014, 380, 18 -27.
AMA StyleSamuel A. Iwarere, J. David Raal, Paramespri Naidoo, Deresh Ramjugernath. Vapour–liquid equilibrium of carboxylic acid–alcohol binary systems: 2-Propanol+butyric acid, 2-butanol+butyric acid and 2-methyl-1-propanol+butyric acid. Fluid Phase Equilibria. 2014; 380 ():18-27.
Chicago/Turabian StyleSamuel A. Iwarere; J. David Raal; Paramespri Naidoo; Deresh Ramjugernath. 2014. "Vapour–liquid equilibrium of carboxylic acid–alcohol binary systems: 2-Propanol+butyric acid, 2-butanol+butyric acid and 2-methyl-1-propanol+butyric acid." Fluid Phase Equilibria 380, no. : 18-27.
Isothermal vapour–liquid equilibrium data (VLE) were measured for propionic acid + caproic acid, isobutyric acid + caproic acid, valeric acid + caproic acid, and caproic acid + enanthoic acid at several temperatures. A refined glass recirculating still with a packed equilibrium chamber and a vacuum-insulated, centrally located Cottrell pump was used for the measurements. Using the chemical theory for the vapour phase, true species concentrations (zi) were calculated for the monomers and dimers and from these liquid-phase activity coefficients by the methods of Prausnitz et al. [J.M. Prausnitz, T.F. Anderson, E.A. Grens, C.A. Eckert, R. Hsieh, J.P. O’Connell, Computer Calculations for Multicomponent Vapor-Liquid and Liquid-Liquid Equilibrium, Prentice-Hall, New Jersey, 1980], based on corresponding states theory and the Lewis fugacity rule for species fugacities. Rigorous tests showed the thermodynamic consistencies to be unusually high for all data sets. All systems showed positive deviations from Raoult's law and were satisfactorily modelled with the NRTL equation.
Alex Hlengwere; Samuel A. Iwarere; Paramespri Naidoo; J. David Raal; Deresh Ramjugernath. Vapour–liquid equilibrium of propionic acid+caproic acid, isobutyric acid+caproic acid, valeric acid+caproic acid and caproic acid+enanthoic acid binary mixtures. Fluid Phase Equilibria 2014, 375, 201 -208.
AMA StyleAlex Hlengwere, Samuel A. Iwarere, Paramespri Naidoo, J. David Raal, Deresh Ramjugernath. Vapour–liquid equilibrium of propionic acid+caproic acid, isobutyric acid+caproic acid, valeric acid+caproic acid and caproic acid+enanthoic acid binary mixtures. Fluid Phase Equilibria. 2014; 375 ():201-208.
Chicago/Turabian StyleAlex Hlengwere; Samuel A. Iwarere; Paramespri Naidoo; J. David Raal; Deresh Ramjugernath. 2014. "Vapour–liquid equilibrium of propionic acid+caproic acid, isobutyric acid+caproic acid, valeric acid+caproic acid and caproic acid+enanthoic acid binary mixtures." Fluid Phase Equilibria 375, no. : 201-208.
The unusual properties of 1-methyl-2-pyrrolidone or N-methyl-2-pyrrolidone (NMP) make it a solvent of interest in industrial extractive distillation processes. To augment available data, vapor–liquid equilibrium (VLE) measurements were made for NMP + 1-hexene at (313.15, 335.15, and 363.15) K, for NMP + water at (343.15, 363.15, and 380.15) K, and for NMP + 1-butanol at (10, 25, and 50) kPa using a dynamic recirculating apparatus. Limiting activity coefficients are reported for water and n-hexene as solutes in NMP. Activity coefficient minima were found for 1-butanol as solvent in NMP in the very dilute regions at (10 and 25) kPa. All systems were modeled satisfactorily with the nonrandom two-liquid (NRTL) equation for the Gibbs excess energy with a variable alpha parameter. Thermodynamic consistency testing of the isothermal data with the Van Ness (Van Ness, H. C. Pure Appl. Chem. 1995, 67, 859–872) direct test is discussed.
Ranjeetha Hirawan; Sumit Sinha; Samuel A. Iwarere; J. David Raal; Paramespri Naidoo; Deresh Ramjugernath. Vapor–Liquid Equilibrium Data for 1-Methyl-2-Pyrrolidone + (1-Butanol or 1-Hexene or Water) Binary Mixtures. Journal of Chemical & Engineering Data 2014, 59, 1643 -1650.
AMA StyleRanjeetha Hirawan, Sumit Sinha, Samuel A. Iwarere, J. David Raal, Paramespri Naidoo, Deresh Ramjugernath. Vapor–Liquid Equilibrium Data for 1-Methyl-2-Pyrrolidone + (1-Butanol or 1-Hexene or Water) Binary Mixtures. Journal of Chemical & Engineering Data. 2014; 59 (5):1643-1650.
Chicago/Turabian StyleRanjeetha Hirawan; Sumit Sinha; Samuel A. Iwarere; J. David Raal; Paramespri Naidoo; Deresh Ramjugernath. 2014. "Vapor–Liquid Equilibrium Data for 1-Methyl-2-Pyrrolidone + (1-Butanol or 1-Hexene or Water) Binary Mixtures." Journal of Chemical & Engineering Data 59, no. 5: 1643-1650.
Experimental studies related to chemical processes based on the use of very high pressure plasma are scarce. In the domain of chemical synthesis enhanced by plasma, the influence of pressure has not been yet reported in literature for conversion of syngas into hydrocarbons. This may be attributed to the difficulties of ignition and sustaining a stable electric discharge at pressures higher than 1 MPa. Yet, the use of high pressure plasma could constitute a new route to synthesize hydrocarbons in gaseous phase. Thus, this paper presents experimental results of hydrocarbons synthesis from a syngas having a H2:CO ratio of 2.2:1, i.e. close to the one commonly met in the classical Fischer–Tropsch process, in a tip-tip non-thermal arc discharge reactor at very high pressure (in the range 0.5–15 MPa) supplied by a high-voltage DC power supply without any catalyst. The molecular synthesis is here studied through the influence of two process setting parameters: operating pressure and supplying current. The results show that C1–C3 molecules can be synthesized by this way and their concentration significantly varies with the two studied parameters. The best results in terms of products concentration after 60 s treatment were obtained: (i) for 12 MPa pressure at 0.35 A current, with concentration of C1 and C2 + C3 around 6000 ppm and 90 ppm respectively, (ii) for 0.2 A current at 0.5 MPa pressure, with concentration of C1 and C2 + C3 around 4500 ppm and 5000 ppm respectively. In addition, the energy efficiency of the process was evaluated, based on the determination of specific energies as they are defined in the classical Fischer–Tropsch process. The results demonstrate that the optima in terms of chemical conversion and energy efficiency coincide together.
Samuel Iwarere; Vandad Rohani; Deresh Ramjugernath; Frédéric Fabry; Laurent Fulcheri. Hydrocarbons synthesis from syngas by very high pressure plasma. Chemical Engineering Journal 2013, 241, 1 -8.
AMA StyleSamuel Iwarere, Vandad Rohani, Deresh Ramjugernath, Frédéric Fabry, Laurent Fulcheri. Hydrocarbons synthesis from syngas by very high pressure plasma. Chemical Engineering Journal. 2013; 241 ():1-8.
Chicago/Turabian StyleSamuel Iwarere; Vandad Rohani; Deresh Ramjugernath; Frédéric Fabry; Laurent Fulcheri. 2013. "Hydrocarbons synthesis from syngas by very high pressure plasma." Chemical Engineering Journal 241, no. : 1-8.
This paper deals with 3D MHD modelling of the behaviour of a tetrafluoromethane (CF4) plasma arc in a batch reactor under peculiar conditions of low current (0.35 A) and very high pressure (50 atm).The first part of the manuscript presents results for a horizontal configuration of the reactor, as is undertaken experimentally. The model has led to the understanding of the instabilities observed experimentally for such unusual operating conditions. The curved shape of the arc and the sliding of the anodic arc root along the electrode have been revealed to be the source of the experimental instabilities.The latter part of the manuscript investigates the effect of two vertical configurations of the reactor; with a cathode at the top and cathode at the bottom to overcome the instabilities. In these reactor configurations, the arc is much more stable and stays centred in the middle of the electrodes. These configurations are more suitable for the stability of the arc discharge, but have to be verified experimentally.
A Lebouvier; S A Iwarere; D Ramjugernath; Laurent Fulcheri. Investigation of tetrafluoromethane as a plasma gas in a very high pressure/low current dc batch reactor by means of 3D MHD modelling. Journal of Physics D: Applied Physics 2013, 46, 355206 .
AMA StyleA Lebouvier, S A Iwarere, D Ramjugernath, Laurent Fulcheri. Investigation of tetrafluoromethane as a plasma gas in a very high pressure/low current dc batch reactor by means of 3D MHD modelling. Journal of Physics D: Applied Physics. 2013; 46 (35):355206.
Chicago/Turabian StyleA Lebouvier; S A Iwarere; D Ramjugernath; Laurent Fulcheri. 2013. "Investigation of tetrafluoromethane as a plasma gas in a very high pressure/low current dc batch reactor by means of 3D MHD modelling." Journal of Physics D: Applied Physics 46, no. 35: 355206.
Coal gasification and natural gas reforming are regarded as mature technologies for syngas production. These technologies are however highly polluting in terms of greenhouse gas emissions, mainly carbon dioxide. Natural gas reforming is considered cleaner than coal gasification but has some disadvantages in terms of higher plant maintenance and processing costs. It utilizes catalysts that are prone to poisoning, are costly, and require regular regeneration. In mitigation of these issues, plasma-based CO2 dissociation technologies could probably offer a new alternative for syngas production. The plasma-based technologies are more compact, have faster response and reaction times, and are relatively cheaper compared to conventional gasification and reforming. Assuming that electricity is produced by a low carbon emitting (renewable or nuclear) power plant, a comparative review of CO2 dissociation technology for syngas production shows that CO2 dissociation can be competitive from an environmental point of view but would face several challenges with the current plasma technologies available. Indeed, the results show that, for current plasma processes to be competitive with conventional processes for syngas production, the energy efficiency, conversion rate, and processing mass flow rates of the unit operations would have to be simultaneously increased. Syngas production would also be highly dependent on the specific energy input and characteristics of the plasma (technology, electric field, power, etc.). CO2 dissociation would give value to carbon dioxide as it consumes 0.33 mol of CO2 for each mole of syngas produced. Therefore, CO2 dissociation can be attractive as a possible option for the conversion of electrical energy to chemical energy, especially when the electrical energy is from a renewable and low cost electricity source.
Alexandre Lebouvier; Samuel Iwarere; Philippe D’Argenlieu; Deresh Ramjugernath; Laurent Fulcheri. Assessment of Carbon Dioxide Dissociation as a New Route for Syngas Production: A Comparative Review and Potential of Plasma-Based Technologies. Energy & Fuels 2013, 27, 2712 -2722.
AMA StyleAlexandre Lebouvier, Samuel Iwarere, Philippe D’Argenlieu, Deresh Ramjugernath, Laurent Fulcheri. Assessment of Carbon Dioxide Dissociation as a New Route for Syngas Production: A Comparative Review and Potential of Plasma-Based Technologies. Energy & Fuels. 2013; 27 (5):2712-2722.
Chicago/Turabian StyleAlexandre Lebouvier; Samuel Iwarere; Philippe D’Argenlieu; Deresh Ramjugernath; Laurent Fulcheri. 2013. "Assessment of Carbon Dioxide Dissociation as a New Route for Syngas Production: A Comparative Review and Potential of Plasma-Based Technologies." Energy & Fuels 27, no. 5: 2712-2722.
A Lebouvier; S A Iwarere; D Ramjugernath; Laurent Fulcheri. 3D magnetohydrodynamic modelling of a dc low-current plasma arc batch reactor at very high pressure in helium. Journal of Physics D: Applied Physics 2013, 46, 145203 .
AMA StyleA Lebouvier, S A Iwarere, D Ramjugernath, Laurent Fulcheri. 3D magnetohydrodynamic modelling of a dc low-current plasma arc batch reactor at very high pressure in helium. Journal of Physics D: Applied Physics. 2013; 46 (14):145203.
Chicago/Turabian StyleA Lebouvier; S A Iwarere; D Ramjugernath; Laurent Fulcheri. 2013. "3D magnetohydrodynamic modelling of a dc low-current plasma arc batch reactor at very high pressure in helium." Journal of Physics D: Applied Physics 46, no. 14: 145203.