Theses and dissertations (Applied Sciences)
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Item A comparative study of supercritical fluid extraction and accelerated solvent extraction of lipophilic compounds from lignocellulosic biomass(2022-09) Khanyile Andile; Sithole, B.B.; Paul, Vimla; Andrew, Jerome EdwardLipophilic compounds are non-structural, heterogeneous compounds rich in terpenes, sterols, fatty acids, hydrocarbons, and glycerides. They have found widespread uses in different industries, such as the pharmaceutical, medical, cosmetic and nutraceutical sectors. They are typically extracted from wood using traditional techniques such as solvent extraction hydro- and steam- distillation. However, these techniques have several drawbacks such as long extraction times, high energy consumption, extensive solvent use and degradation of thermosensitive compounds, which are highly volatile. In this study, supercritical fluid extraction (SFE) and accelerated solvent extraction (ASE) were evaluated to extract lipophilic compounds from lignocellulosic biomass such as pinewood sawdust and Cannabis Sativa L. Their advantages of using low amounts of solvent, short extraction times and high selectivity allow them to be used as an alternative extraction technique to traditional methods. Moreover, SFE uses carbon dioxide, which is safe, cheap and readily available, and it does not alter the structure of the compounds. In contrast, ASE uses elevated temperatures and high pressures to prevent the evaporation of highly volatile compounds. In order to solve challenges from both an economic and an environmental perspective, the interaction of process conditions on lipophilic compounds extraction efficiency was modelled and optimized using Response Surface Methodology (RSM) and BoxBehnken design (BBD). The extraction variables optimized for pinewood sawdust compounds were, SFE: co-solvent (ethanol) flow rate (1-2 ml/min), carbon dioxide (CO2) flow rate (1-3 ml/min), Temperature (40-60 °C) and pressure (200-300 bar), and for ASE: static time (10-15 mins), static cycle (1-3) and temperature (80-160 °C). The process parameters were optimized, and the experimental data was modelled using RSM for statistical analysis of the BBD extraction process. The experimental data's quadratic polynomial models gave a coefficient of determination (R2 ) of 0.87 and 0.80 for ASE and SFE, respectively. The optimum conditions of ASE were temperature (160 °C), static time (12.5 mins), and static cycle (1), which resulted in a maximum yield of 4.2%. The optimum SFE conditions were temperature (50 °C), pressure (300 bar), CO2 flow rate (3.2 ml/min), and a 2 ml/min co-solvent (ethanol) flow rate that yielded 2.5% lipophilic compounds. The extraction efficiency of pinewood sawdust lipophilic compounds with ASE was higher compared to the SFE. Although ASE uses high temperatures that may degrade thermolabile compounds, the short extraction times may work in their favor since the extracts are not exposed to high temperatures for long periods. SFE uses low temperatures and long extraction times compared to ASE. Several properties affect the extraction efficiency, such as volatility, dissolving power, solubility, and fluid density of the extracting solvent. The extraction efficiency of lipophilic compounds by SFE may be affected by the supercritical fluid's solubility and differences in densities at different pressures. In ASE, the high yields were influenced by the high polarity of the solvent mixture and temperature with a short extraction time. The extraction variables optimized using RSM for Cannabis Sativa L. for SFE were pressure (200-300 bar), co-solvent (ethanol) flow rate (1-2 ml/min) and CO2 flow rate (1-2 ml/min). The R2 was determined to be 0.9108. The optimum conditions were 300 bar pressure, 1 ml/min co-solvent (ethanol) flowrate, and 2 ml/min CO2 flowrate, which gave a maximum yield of 88%. The high efficiency observed was brought by the increase in the flow rate of CO2 at high pressures, which reduces the mass transfer resistance, while the cosolvent enhanced the solvating power of CO2. The ASE had a high extraction efficiency for the pinewood sawdust lipophilic compounds. However, the method's selectivity was very low according to the results obtained by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). The thermosensitive compounds, such as terpenes, decreased from 2.01% to 1.69% upon the addition of Tetramethylammonium hydroxide (TMAH). The initial concentration of terpenes was 7.21% in pinewood sawdust by SFE. Upon the addition of TMAH, the concentration of terpenes of the pinewood sawdust decreased to undetectable levels. The initial concentration of the terpenes of Cannabis Sativa L. was 14.29% and decreased in the presence of TMAH to 0.39%. The Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of lipophilic compounds functional groups and a fingerprint region of lipophilic compounds of pinewood sawdust and Cannabis Sativa L. Thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) showed high thermal stability (250 – 400 ℃). This research demonstrated the ability of SFE to extract lipophilic compounds from pinewood sawdust Cannabis Sativa L.Item Use of 1-ethyl-3-methylimidazolium ethyl sulfate for liquid-liquid equilibria for ternary mixtures(2017) Mohale, Tshepang; Deenadayalu, NirmalaThis thesis forms part of the Durban University of Technology Thermodynamics Research Unit’s project which is aimed at developing a method for determination of the liquid-liquid equilibria (LLE) data for the azeotrope {methanol + water} with an ionic-liquid (IL) using DSA5000M to assess the efficiency of the ionic liquid to be used in liquid-liquid extractions for the recovery and recycling of methanol from petroleum refinery. The objective of this study was to determine the liquid-liquid equilibria data of the azeotrope {methanol + water} using 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid with the intention to recycle methanol from the Fischer-Tropsch (FT) process by- products in petroleum industries and to utilize it in gasoline additives in a new methanol to gasoline (MTG) petroleum process. LLE studies of systems containing alcohols and water are important due to the increasing demands of oxygenated compounds to produce lead free gasoline. Light alkanols such as methanol and ethanol are reported to be suitable compounds in order to produce lead free gasoline, but the use of methanol in gasoline blends can cause phase separation problems in: 1. dry conditions, these are due to its partial solubility in saturated hydrocarbons. 2. the presence of water from ambient humidity or in storage tanks, this depend on unfavourable distribution factor between aqueous and the hydrocarbon phase. To determine the possibility of separating methanol from water using ionic liquid, the liquid-liquid equilibria data was determined at room temperature, T = 298.15 K and atmospheric pressure to investigate whether it separate from water and/or a non-phase separation if it is used as an additive. The experimental data generated was compared to that of the literature for the system {methanol (1) +toluene (2) + dodecane (3)} and showed good agreement with the literature data with only maximum deviation of ± 0.0015 in the mole fraction using density calculations and ± 0.0092 in the mole fraction when using refractive index calculations The selectivities and distribution coefficients for this system were also calculated and the maximum deviation between the two methods (nD and ρ) was ± 1.33 in selectivities and found to be ±0.001 for distribution coefficients. The maximum deviation in distribution coefficients from literature when using nD calculations for system 1 was ±0.04 and ±0.01 for ρ. For the selectivity values the deviation from that of literature of nD when compared was found to be ± 1.28 and 0.29 for ρ respectively. The selectivity values from the density calculations were found to be in the range 2.82 – 7.66 for this system with the distribution coefficient values reported in the range 0.17 – 0.23. In the second system (system 2) the generated experimental data was also compared to that of the literature for the system {water (1) + methanol (2) + cyclohexane (3)} and in good agreement with literature values with only maximum deviation of ± 0.0091 in the weight fraction based on density calculations. The selectivities and distribution coefficients were also calculated and the maximum deviation between the literature and the experimental data was computed to be at ± 0.0003 for selectivity and ±0.09 in distribution coefficient. The selectivity values were found to be in a range 0.00 - 0.04 for this system and were constant throughout the phases but significantly less than one; with the distribution coefficient values in the range 0.00 – 0.008. For 1-ethyl-3-methylimidazolium ethyl sulfate system (Ionic liquid system) the selectivity values were not constant throughout the two-phase region and the values were found to be in the range 0.63 -0.99 still below one which indicates that the ionic liquid used in this study could not be considered as a potential solvent for the separation of the investigated azeotrope. The distribution coefficients for this system were determined and found to be in the range 0.23 – 0.74. The certainty and reliability of experimentally measured tie-line data was ascertained by applying Othmer-Tobias (OT) correlations and the Non-Random, Two Liquid (NRTL) parameters. The OT correlations for system 1 was linear and indicated the certainty of the five tie-lines prepared for this system. In system 2 the OT correlation was not linear and indicated extensively high errors as well as high systematic multiplicative and additive errors in calculations of mole fractions. For the IL system the OT correlation was linear throughout the whole tie-line range and indicated the adequate precision, which denotes that the investigation was carried out with minimal random and systematic errors and indicated the efficiency of the DSA 5000 M to generate the liquid-liquid equilibria data. All the ternary systems were well correlated and in good agreement with the estimated NRTL data. It was only system 1{methanol (1) + toluene (2) + dodecane (3)} that gave a high maximum deviation ( %RSMD) of 1.288 when using the RI measurements with the minimum error margin of 0.6320, this account as to why RI measurements were not applied in other systems (system 2 and ionic liquid system). Similarly for the same system; system 1{methanol (1) + toluene (2) + dodecane (3)} when using the density measurements; the NRTL model gave a maximum deviation of 0.5620 and minimum error margin of 0.2590. The NRTL obtained for system 2 {water (1) + methanol (2) + cyclohexane (3)} gave the maximum deviation of 0.5752 and minimum error margin of 0.0127. The NRTL for the ionic liquid ternary system {[EMIM][EtSO4](1) + methanol (2) + water (3)}showed a good agreement between the experimental data and the NRTL model tie- line data with the %RSMD of 1.0201 on the upper limit and 0.1620 as a lower deviation.Item Extraction of aromatic solvents from reformates and paint solvent wastes during ionic liquids(2016) Mabaso, Mbongeni Hezekia; Redhi, Gyanasivan Govindsamy; Moodley, K. G.The work conducted in this study comprised three aspects: syntheses, characterizations, and multi-component liquid-liquid extractions. The main objectives of the project were: (1) to evaluate the efficacy and efficiency of ionic liquids to extract aromatic components from catalytic reformates and paint solvent wastes, and (2) to validate the method(s) used in this project to qualitatively and quantitatively analyze the aromatic molecules (BTEX) in multi-component mixtures. Therefore, this research critically investigated the major effects of the chosen ionic liquids as extractive solvents for the recovery of BTEX components from model and industrial organic mixtures. The project was concerned with the nature of solvents currently used in most industries for the separation by extraction of aromatic hydrocarbons from non-aqueous or organic mixtures. Most solvents currently employed for this purpose are highly volatile; hence they contribute significantly towards environment pollution. In addition, the extraction efficiency of these conventional solvents is limited only to mixtures containing aromatic hydrocarbons of 20% or more. Furthermore, conventional solvents are organic compounds which are generally toxic, flammable, and expensive to recover or regenerate from extract phases due to methods which involve several steps. In addition, they demand high energy input for the distillation steps. used in the analysis of aromatic components were evaluated for validity. According to the literature no such work was carried out by previous researchers. The study targeted four ionic liquids, namely, 1-ethyl-3-methylimidazolium ethyl sulphate [EMIM][ESO4], 1-ethyl-3-methylpyridinium ethyl sulphate [EMpy][ESO4], 1- Butyl-1-methyl-2-pyrrolidonium bromide [BNMP][Br], and 1,1-Dimethyl-2- pyrrolidonium iodide [MNMP][I] in an attempt to address this concern. These ionic liquids were synthesized and characterized in our laboratories using previously accepted methods. After synthesis and purification, they were characterized by techniques including FTIR, 1H-NMR, and 13C-NMR. The densities and moisture content of both the synthesized and standard ionic liquids were also determined using density meters and Karl-Fischer apparatus, respectively. The extractions were carried out on both the model and industrial mixtures using ionic liquids. Each ionic liquid was mixed with a target mixture in a water-jacketed vessel and then stirred vigorously at constant temperature achieved by a thermostatically controlled water-bath. After a selected period of time the operation was stopped and the resulting mixture was left to stand overnight to allow phase equilibration to be reached. The two phases were then separated and analyzed for the content of individual aromatic components in each phase using GC-FID calibrated with external standards of the components present in the mixtures being investigated. According to the results obtained from the synthesis and characterization methods the percentages yield of ionic liquids were reasonably high (> 95%). In addition, spectral studies showed high purity with fewer traces of impurities based on the observed relative intensities. Results from GC-FID indicated a relatively lower concentration of aliphatic hydrocarbons in the extract phase. On the other hand, the concentrations of aromatic II components in the extract phase were relatively higher than those of aliphatic hydrocarbons. The results obtained from the three extraction stages showed the total recovery of greater than 50% for the aromatic components. This suggests that at least six extraction stages would be required in order to achieve a total recovery of 100% aromatic components which is an indication of good efficiency. Also noticeable was that the first extraction stages for all ionic liquids recovery values were much higher than those values obtained from successive stages which showed approximately the same extraction results. In most experiments, 1-ethyl-3-methylpyridinium ethyl sulphate gave higher recovery values than the other three ionic liquids. It was also noted that the recovery values obtained from the extractions performed on model mixtures of the entire concentration range (0.5 – 25%) of individual aromatic components did not show any significant difference. Proportional difference in recoveries occurred across the entire concentration range of model mixtures. The results also indicated that the solubility of aromatic hydrocarbons in the ionic liquids decreases in the order: benzene > toluene > ethyl benzene >xylenes. This phenomenon is attributed to a decrease in π-π, cation- π, cation- anion interactions occurring between the ionic liquid and each of the aromatic molecules in this order. The recovery values for BTEX ranged from 80 to 120 % by volume for the three extraction stages. This is in line with results previous research studies carried out on liquid-liquid extractions involving ternary systems containing only one aromatic component in each mixture. Therefore this study shows that ionic liquids are capable extraction solvents for simultaneous recovery of the aromatic components from any organic mixtures containing low to high BTEX concentrations. In addition, the outcomes of this project have proved that ionic liquids are economically viable as potential extraction solvents since they can be easily recycled and reusable many times without any noticeable degradation. The results of this study are envisaged to make significant contributions to the current research efforts aimed at achieving greener environments and minimization of global warming. The findings of this project are also geared to boost the economy of our country through job creation using economically viable methods.