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An investigation of the solvent extraction kinetics of Germanium by 7- alkylated.-8-hydroxyquinoline extractants.Foster, Stephen James. January 1990 (has links)
Equilibrium and kinetic data for the solvent extraction of
germanium by three impure commercial 7-alkylated-8hydroxyquinoline
extractants which vary in structure at the 7alkyl
group, are evaluated in order to elucidate an holistic
kinetic extraction model which accounts for the various
reactions and partition effects occurring during the metal-ion
chelation process.
It is proposed that for the extraction process, which is first
order in germanium concentration, by the ligand reagents
Lix 26, TN 01787 and TN 02181, the rate-determining step, on
stereochemical grounds, is the attachment of either a neutral
ligand or a protonated ligand species-to the biligand
intermediate GeL2
2+ (L:ligand) at the interface.
In high speed shaking/mixing assemblies the extraction process
was observed to occur in two discrete reaction regimes : a
fast initial rate for which the orders with respect to ligand
reagent are 1,06, 2,10 and 1,77 for TN 02181, Lix 26 and
TN 0178-7 respectively, and a slower subsequent rate for which
the apparent reaction orders with respect to ligand
concentration are 1,12, 2,70 and 3,08 for TN 02181, Lix 26 and
TN 01787 respectively. For the slower reaction regime, orders
between 1 and 3 are explicable if the steady state
approximation is invoked for the intermediate germanium
species GeL3+ and GeL2
2+ formed at the interface. In the fast
reaction regime, it is proposed that the accelerated
extraction rates are a function of (i) the speciation of
germanium and (ii) participation in the rate-determining step
by the protonated ligand moiety H2L+HS04- which is rapidly
formed after phase contact.
At low ligand concentration, the following order of ligand
efficacy has been observed :
TN 01787 < Lix 26 < TN 02181
whereas at high concentration ligand efficacies are similar
because the interface is saturated with ligand.
Orders with respect to [H+] for the reagents vary from -1 to -
3 during the course of reaction, indicating complex mixedorder
behaviour.
The effects upon extraction of ionic strength, temperature,
the addition of organic modifiers and diluent nature are
investigated as well as the kinetics of germanium stripping by
aqueous hydroxide.
The physical effects of interfacial tension, viscosity and
relative dielectric constant are also reported and suggestions
are made as to their effect upon the extraction
characteristics. Computer modelling of the extractants has
been used as an aid in describing size, structure and
stereochemical considerations of the ligands and the chelate
products. / Thesis (Ph.D.)-University of Natal, Durban, 1990.
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Synthesis of tetrahydroisoquinoline (TIQ) ligands and their applications in ayymmetric catalysis.Chakka, Sai Kumar. January 2010 (has links)
A series of 88 novel tetrahydroisoquinoline (TIQ) compounds have been synthesised for
applications in asymmetric catalysis. Several chiral TIQ ligands, possessing N,O and N,N
donor atoms, have been prepared and evaluated for the catalytic asymmetric transfer
hydrogenation (ATH) of pro-chiral ketones. The highest selectivity obtained for the
asymmetric transfer hydrogenation of acetophenone with the N,O donor atom ligands was
>99 % ee at low temperatures in iso-propanol with [Ru(p-cymene)Cl2]2 as a pre-catalyst. The
observed enantioselectivity was supported by theoretical calculations using the Jaguar
interphase program (Paper I). An enantioselectivity of 70 % was obtained with the ligands
possessing the N,N donor atoms with the observation that water played a significant role in
the enantioselectivity of the ATH reaction of acetophenone (Paper II).
An investigation into the usefulness of the TIQ scaffold with other donor atoms was also
undertaken. A series of novel P,N oxazoline ligands were synthesised and coordinated to
Iridium BArF. These complexes were screened as chiral catalysts for the high pressure
asymmetric hydrogenation of unsymmetrical olefins. The reactions proceeded readily at
ambient temperature and provided selectivities of up to >91 % ee with excellent conversion
rates (>99 %) for the benchmark reactions. Based upon these favorable results, the ligands
providing the best results were further screened on a variety of functionalized and unfunctionalised
olefins (Paper III).
The success of the TIQ backbone in ATH reactions prompted an investigation into its
applications in carbon-carbon (C-C) bond forming reactions. The Henry (nitroaldol) reaction
is an important C-C bond forming reaction with the chiral oxazoline class of ligands being
widely utilised. A series of novel, chiral TIQ oxazoline ligands were synthesised and
complexed to various metals (Cu, Sc, Co, Zn, Ni and Mn). These complexes were screened
as chiral catalysts in the asymmetric Henry reaction. The highest enantioselectivity (>77 %)
was obtained when Cu(OAc)2was employed as a pre-catalyst and iso-propanol as a solvent
(Paper IV).
The final chapter deals with carbon-sulphur bond formations facilitated by the conjugate
addition of thioglycolate to various chalcones. A series of novel, chiral TIQ N-oxide ligands
were synthesised and complexed to lanthanum. The complexes were screened for activity
against the benchmark reaction and an enantioselectivity of 81 % was obtained. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2010.
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Synthesis and analysis of Eriosema isoflavonoids and derivatives thereof.Selepe, Mamoalosi Alix-Maria. January 2011 (has links)
Kraussianone 1 and kraussianone 2 were previously isolated as active compounds from the roots of Eriosema kraussianum Meisn., a plant used for the treatment of male impotence and urinary complaints in KwaZulu-Natal. The objectives of this study were firstly, to develop a method for the analysis of metabolites from E. kraussianum and other Eriosema plants that are used for erectile dysfunction and secondly, to develop synthetic methods for
kraussianone 1 and structurally related compounds.
A reversed-phase HPLC-PDA method was developed for the analysis of the extracts of plants from different sources, two of which were authentic E. kraussianum collected from the Drakensberg and Pietermaritzburg. The roots of other Eriosema species called ubangalala and uqonsi in Isizulu were also analysed. These plants were bought from the local herbal traders. The extracts of the two E. kraussianum plants and one uqonsi sample
showed a similar chemical profile, even though there were variations in the relative concentrations of the metabolites within each plant. In these three plants, kraussianone 1, the most active metabolite of E. kraussianum, occurred in relatively low quantities, whereas kraussianone 2 was one of the major constituents. The other commercial plants that were analysed contained different compounds from those found in E. kraussianum.
The HPLC method developed herein facilitates rapid identification and relative quantification of metabolites from E. kraussianum.
Strategies based on semi-synthesis and total synthesis were employed for the preparation of kraussianone 1. The semi-synthetic route was based on the transformation of the prenyl side chain of kraussianone 2 into a linear dimethylpyran scaffold fused to the A-ring. Two routes were investigated for the semi-synthesis of kraussianone 1 from kraussianone 2. In
the first route, the dimethylchromene ring was to be prepared by the acid-catalysed cyclisation of the prenyl group of kraussianone 2, followed by dehydrogenation of the resulting dimethylchroman chromophore. This route was abandoned due to poor regioselectivity of the cyclisation reaction and the difficulty of oxidising the dimethylchroman scaffold on the phloroglucinol moiety into a dimethylchromene. The second strategy involved selective protection of the OH-2', followed by DDQ-mediated oxidative cyclisation of the prenyl group to OH-7. This was the most viable route and
kraussianone 1 was prepared in an overall yield of 54% from kraussianone 2.
The total synthesis of kraussianone 1, on the other hand, employed the Suzuki-Miyaura reaction for the construction of the isoflavone nucleus and the regioselective introduction of the dimethylpyran scaffolds to the A- and B-rings. The key precursors in this synthesis were 3-iodo-5,7-dimethoxymethoxychromone and a boronic acid coupling partner, 7-
benzyloxy-2,2-dimethylchromene-6-boronic acid, already bearing the prerequisite chromene scaffold attached to the B-ring. The isoflavones genistein, 2-hydroxygenistein, eriosemaone D and a geranyl analogue of kraussianone 1 were prepared via the route developed for the total synthesis of kraussianone 1 by structural modifications of rings A and B. Furthermore, this synthetic approach was expanded to the synthesis of the
coumarochromones lupinalbin A and lupinalbin H. The development of the feasible semi-synthetic and total synthetic routes described herein
for kraussianone 1 is of importance for the production of material for an in depth study of the pharmacological activities and the structure-activity relationship studies of kraussianone 1 and related compounds. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2011.
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Rhodium-catalyzed and uncatalyzed synthesis of boronate esters and their subsequent utility in the Suzuki realm.Hadebe, Siphamandla Wiseman. January 2008 (has links)
This study has shown that alkythioboranes 1,3,2-dithiaborolane and 1,3,2-dithiaborinane, disproportionated significantly during their synthesis. Their interaction with 1-octene has been investigated, and the rate constants, enthalpies and entropies of the hydroboration process, have been determined. The thermodynamic and kinetic parameters obtained have shown that the hydroboration reaction is sluggish and proceeded via an associative mechanism. / Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2008.
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Synthesis and characterisation of new Schiff base chelates of platinum group metals.Salmond, Rosanne C. January 2011 (has links)
The principal goal of this work was to synthesise and fully characterise a range of
platinum group metal chelates of bis(pyridine-imine) ligands. These four-nitrogen donor
Schiff base ligands are underdeveloped relative to their salen (ONNO donor)
counterparts. The purified metal complexes were to be tested for their cytotoxicity
against cancer cell lines and their mode of interaction (expected to be intercalation)
studied.
The syntheses, spectroscopic and structural properties of some novel and some already
known bis(pyridine-imine) ligands are described. Furthermore, UV-Vis, IR and NMR
spectroscopy, as well as electrospray ionisation mass spectrometry, have been used to
characterize the ligands and comparisons were made with relevant literature. Fifteen
Schiff base ligands were successfully condensed from a 2-formyl or 2-ketopyridine
starting material and a diamine bridging group, while the attempted syntheses of a
further three are described. Literature methods or variations thereof were employed in
the syntheses of these derivatives, which generally resulted in good yields. X-ray quality
crystals were obtained and X-ray structures were determined for four novel ligands and
five unexpected cyclised hexahydropyrimidine- and imidazole-containing bidentate
ligands, of which three were novel structures.
The series of bicationic palladium and platinum complexes synthesised here were
analysed by NMR, IR and UV-Vis techniques, as well as X-ray crystallography when
possible. The complexes were prepared by reacting the free ligands with platinum group
metal salts in refluxing acetonitrile. The complexes exhibit infrared bands for the imine
C=N stretch between 1604–1670 cm-1; around 15–40 cm-1 lower than the free ligands.
The 1H NMR spectra in the CH=N chemical shift region also display shifts (0.1 to 0.8
ppm for the palladium complexes or 0.4 to 0.9 ppm for the platinum complexes) which
are consistent with metallation.
X-ray crystal structures were obtained for eight novel metal complexes, which all
crystallised in the monoclinic crystal system. The solid state analysis shows changes in
the free ligands upon introduction of the metal ions, caused by the coordination process.
Metallation of the free ligands led to twisting of the ligands due to size effects and the
spatial restrictions of the coordination geometry of the central metal ions. The structures
were generally solved by direct methods and refined to R1 = 0.0729 or less. Singlecrystal
X-ray diffraction analysis confirmed that the mononuclear complexes exhibit a
distorted square planar coordination sphere composed of the four donor nitrogen atoms
(two imine and two pyridyl nitrogen atoms) from the Schiff base ligands. The complexes
were generally very stable and differed by the type of metal ion (platinum(II) or
palladium(II)) and the diamine bridging group (2-carbon or 3-carbon linking chain with
various substituted groups). A range of unconventional F···H−C contacts is revealed to
play an important role in the overall bonding and crystal packing of many complexes.
To better understand our measured data and to separate the intrinsic properties of our
molecules from intermolecular interactions, theoretical calculations at the DFT (B3LYP)
level were carried out. These calculations predict the structural and spectroscopic
properties for the free ligands and their metallated counterparts. DFT simulations were
performed for the fifteen synthesised ligands (B3LYP functional, 6-31G** basis set), as
well as three projected ligands that could not be synthesised, and for all proposed thirtysix
metal complexes (B3LYP functional, SDD basis set). DFT simulations were used to
obtain theoretical IR frequency data which was compared to the literature and used to
prove the location of a local minimum energy structure in the geometry optimisation
rather than a transition state. Our results collectively showed the B3LYP level of theory to
be useful in the prediction of IR frequencies for these Schiff base ligands as well as the
platinum(II) and palladium(II) complexes.
Geometry optimisations performed using density functional theory for the free ligands
and metal complexes were compared, where possible, with X-ray data. For the free
ligands the main structural differences were observed for the position of the pyridyl-imine
"arms" of the ligands with relatively good agreement between the two structures for the
bridging groups. On the other hand, the metal complexes showed greater discrepancies
for the bridging groups rather than for the pyridine rings. These differences were also
affected by the length of the carbon bridge; the longer the carbon bridge, the less
variation was observed. The trends in the variation of bond distances and angles with the
metal ion identity and ligand structure delineated by DFT simulations were matched by
similar trends in the X-ray data.
Differences between the gas phase calculated geometries and those determined by Xray
diffraction were attributed to packing effects in the solid state and intermolecular
interactions not being accounted for during DFT computations. The impressive similarity
observed between the structures obtained from X-ray crystallography and computed by
DFT shows the applicability of these computations at the B3LYP level of theory. They
were able to accurately predict structural and spectroscopic properties for the ligands
and complexes presented in this work.
The in vitro cytotoxicities of some of the metal complexes were evaluated against two
mouse cancer cell lines. The compounds tested had lower than expected cytotoxicity
towards the cell lines studied with IC50 values > 100 μM. The interaction of the
complexes with calf thymus DNA has been explored by using absorption studies. From
the observed changes in absorption possible modes of binding to DNA have been
proposed for the metal complexes. Significant changes were observed in the absorption
spectra upon interaction of the complexes with DNA, from which large binding constants
were determined. The changes were, however, not as intense as expected nor were the
spectral variations typical of intercalating drugs. There were also no bathochromic shifts
nor any isobestic points observed for most of the metal complexes, except one. For the
cationic PGM chelates studied, the lack of shift in the wavelength of the visible range
MLCT band maximum and small changes in the band intensity were more indicative of
weak electrostatic interactions. Our spectral data were thus interpreted as being
consistent with non-intercalative binding; either simple electrostatic adduct formation or
major/minor groove binding.
The binding constant values (Kb) of the metal complexes estimated from the titration with
calf thymus DNA monitored by absorption spectroscopy were all in the range of 105 M-1.
This is within the range of those reported for other platinum(II) and palladium(II) metal
complexes that have shown intercalation and/or groove binding. With the lack of
inhibition of growth of the selected cancer cell lines it is possible that the compounds do
not reach nuclear DNA in living cells or that such compounds are possibly substrates for
efflux transporters. All the metal complexes in this work were determined to not be pure
DNA intercalators as had been expected; however, in some cases partial intercalation
cannot be ruled out from the spectral data. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
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A powder diffraction study of problems in platinum group metal extraction.Smith, Ian William Sands. January 1994 (has links)
The base metal and platinum group metal extractive processes for two South African
refineries were examined using x-ray powder diffraction.
Base metal refinery matte contained nickel sulphide (Ni3S2), copper sulphide (Cu2S),
nickel-copper alloy (Ni-Cu), iron oxide (Fe3O4) - nickel iron oxide (NiFe2O4) and nickel
oxide (NiO). Nickel iron oxide and cobalt sulphide (CO3S4) were found in matte
aeration cavities. Matte fast cooling caused alloy zoning.
Alloy stoichiometry and weight percentages of matte constituents were calculated.
Magnetic separation of the alloy phase was unfeasible due to high bulk and poor
separation from Ni3S2. Sulphuric acid matte leaching produced residues containing
copper sulphide (Cul.8S) and nickel sulphides (Ni3S4, NiS). Potassium cyanide residue
leaching produced NiS-rich residues, while thiourea / hydrochloric acid leaching
produced residues almost free of copper sulphide. PGM concentrates were examined. Base metals occurred as: copper sulphate pentahydrate; copper sulphate hydroxide hydrate (CU4SO4(OH)6'H2O); copper sulphide (CuS); copper platinum (Cu3Pt); nickel oxide (NiO); nickel iron oxide (NiFe2O4). Lead occurred as lead sulphate and silicon as quartz and enstatite ((Mg,Fe,Al)SiO3). Heating the concentrate to 260°C with sulphuric acid converted copper sulphide to copper sulphate. PGMs were mostly metallic. Overdrying concentrates caused pgm sintering. Drying with sulphuric acid reduced sintering. PGM oxidative leach solubility was examined. Platinum sulphide (Pt,Pd)S caused low platinum and palladium solubility. (Ru,Rh,Ir,Pt)AsS caused low rhodium and ruthenium solubility. Platinum-rhodium (Rh0.57Pt0.43), ruthenium-osmium (~Ru16Os), iridosmine (Os,Ir,Ru) also caused low pgm solubility. Silver chloride remained in residues. Concentrate overdrying produced insoluble sintered platinum, palladium monoxide, and ruthenium dioxide. In minor concentrates sintered platinum, rhodium selenide (RhSe2+x), ruthenium dioxide and possibly palladium monoxide lowered pgm solubility. Precipitates and salts were examined. Iron precipitated as iron oxide hydroxide (B-FeOOH); gold as metallic gold; lead as lead chloride. Common salts were: sodium chloride; sodium iron hydroxide sulphate hydrate (Na2Fe(SO4)2(OH)'3H2O); ammonium chloride; sodium carbonate monohydrate. PGM-Iead fusion was examined. Fusion produced the insoluble alloy Pb(Pd,Pt)3. Ruthenium dioxide reacted with lead carbonate forming lead ruthenium oxide (Pb2Ru2O6.5). Nitric acid insoluble residues also contained lead sulphate and iron oxide (Fe3O4). This study demonstrated that solution problems can be understood by identifying the crystalline insoluble phases in intractable residues. / Thesis (Ph.D.)-University of Natal, Durban, 1994.
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Asymmetric synthesis with an ephedrine based chiral auxilliary.Malissar, Dean Graham Shane. January 1992 (has links)
Abstract available in pdf file.
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An application of modern analytical solution techniques to nonlinear partial differential equations.Augustine, Jashan M. 20 May 2014 (has links)
Many physics and engineering problems are modeled by differential equations. In
many instances these equations are nonlinear and exact solutions are difficult to
obtain. Numerical schemes are often used to find approximate solutions. However,
numerical solutions do not describe the qualitative behaviour of mechanical systems
and are insufficient in determining the general properties of certain systems of
equations. The need for analytical methods is self-evident and major developments
were seen in the 1990’s. With the aid of faster processing equipment today, we are
able to compute analytical solutions to highly nonlinear equations that are more
accurate than numerical solutions.
In this study we discuss solutions to nonlinear partial differential equations with
focus on non-perturbation analytical methods. The non-perturbation methods of
choice are the homotopy analysis method (HAM) developed by Shijun Liao and the
variational iteration method (VIM) developed by Ji-Huan He. The aim is to compare the solutions obtained by these modern day analytical methods against each other
focusing on accuracy, convergence and computational efficiency.
The methods were applied to three test problems, namely, the heat equation, Burgers
equation and the Bratu equation. The solutions were compared against both the exact
results as well as solutions generated using the finite difference method, in some cases.
The results obtained show that the HAM successfully produces solutions which are
accurate, faster converging and requires less computational resources than the VIM.
However, the VIM still provides accurate solutions that are also in good agreement
with the closed form solutions of the test problems. The FDM also produced good
results which were used as a further comparison to the analytical solutions. The
findings of this study is in agreement with those published in the literature. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
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An investigation into air stable analogues of Wilkinson's catalyst.Naicker, Serina. 22 May 2014 (has links)
Since the discovery of Wilkinson’s catalyst and its usefulness in the homogeneous hydrogenation of olefins many investigations have been carried out on trivalent, tertiary phosphine–rhodium complexes.¹ Studies have shown that N-Heterocyclic carbenes as ligands offer increased stability to the complex and possess similar electronic properties as phosphine ligands.² The applications of the traditional catalyst are limited due to the limited stability of its solutions and its susceptibility to attack from the environment i.e. oxygen and moisture. The hydrogenation of olefins and other unsaturated compound is of great importance for the fine chemical and petroleum industries. The aim is to produce more stable and active versions of the traditional catalyst and also to demonstrate their improved stability and activity in catalytic applications. This study involves the investigation of the effects of ligand modification on Wilkinson type hydrogenation catalysts. Five Rhodium-phosphine complexes 1a: Rh(PPh₃)₃Cl, 1b: Rh(PPh₂Me)₃Cl, 1c: Rh(PPh₂Et)₃Cl, 1d: Rh(PPhMe₂)₃Cl, 1e: Rh(PPhMe₂)₃Cl have been synthesised and characterised by means of melting point,¹H NMR, ¹³C NMR, ³¹P NMR, IR and Mass Spectroscopy. Complexes 1d and 1e have also been characterised by means of elemental analysis and single crystal XRD. Five rhodium-N-heterocyclic carbene complexes 2a: Rh(COD)ImesCl [Imes =1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] , 2b: Rh(COD)(diisopropylphenyl)₂Cl 2c: Rh(COD)(adamantyl)²Cl, 2d: Rh(COD)(diisopropyl)²Cl 2e: Rh(COD)(ditertbutyl)²Cl have been synthesised and characterised by means of melting point, ¹H NMR, ¹³C NMR, IR and Mass Spectroscopy. Five rhodium-NHC-CO complexes 3a: Rh(CO)₂ImesCl, 3b: Rh(CO)₂(diisopropylphenyl)₂Cl, 3c: Rh(CO)₂(adamantyl)₂Cl , 3d: Rh(CO)₂(diisopropyl)₂Cl, 3e: Rh(CO)₂(ditertbutyl)₂Cl, have been synthesised and characterised by means of ¹H NMR, ¹³C NMR, IR and Mass Spectroscopy.
Complexes 1a, 1d, 1e, 2a, 2b, 2c, 2d, 2e were tested in the hydrogenation of simple alkenes under mild conditions. For the rhodium-phosphine complexes the catalyst efficiency based on TOF increases in the following order: 1a > 1d > 1e or RhCl₃(PPhMe₂)₃ > RhCl₃(PPhEt₂)₃ > RhCl(PPh₃)₃. For the rhodium-(COD)-NHC complexes catalyst efficiency based on TOF increases in the following order: 2d > 2b > 2e > 2a > 2c. While rhodium-phosphine complexes are far more active than rhodium-(COD)-NHC complexes, the latter seem to be active for a longer time and hence more stable under mild hydrogenation conditions. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.
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Physico-chemical analysis of transformer oil and stability studies of their blends with synthetic and natural antioxidants.Dukhi, Veresha. January 2012 (has links)
This study is focused on the analysis of transformer oil commonly used in South African
transformers and the characterisation of the blends of these oils with either synthetic antioxidants
or those extracted from natural sources.
The virgin naphthenic based uninhibited transformer oil was shown to have no acidic or
saponifiable constituents. Although the oil used in this study is naphthenic based it was found to
contain bicyclic compounds identified as tetralin (aromatic) and decalin by GC-MS. The oils
were void of typical wear metals and only additive metals/non-metals were present. The blending
of transformer oils with synthetic antioxidants was successful as confirmed by ¹H NMR, ¹³C
NMR and FT-IR data. The blending showed increased antioxidant activity of the oils as well as
thermal stabilities (DPPH assay and TGA respectively). Apparent activation energy for the
decomposition reaction was determined by means of the Ozawa, Flynn and Wall (OFW) and
Kissinger models. The apparent activation energy for BHT-B, DBP-B and VO were found to be
57.0, 63.7 and 69.3 kJ molˉ¹
, respectively for 10% mass conversion obtained from TGA data
(OFW model). The dissipation factor for the oil blends was established to be favourably lower
than that of unblended oils; however an undesirable decrease in the dielectric breakdown voltage
of the blends was observed (16, 26 and 50 kV for BHT-B, DBP-B and VO respectively).
The blending of transformer oil with synthetic antioxidants is a common practice, however
greener approaches are always favoured. In this study, a greener approach was employed by
blending the transformer oil with turmeric plant extract in an effort to improve the oil’s
performance. Turmeric is known for its antimicrobial, antioxidant and anticarcinogenic
properties. Solvent extraction of turmeric powder and subsequent blending into transformer oils,
revealed the dissolution of 5 components from turmeric into the oil, viz., curcumene,
sesquiphellandrene, ar-turmerone, α-turmerone and β-turmerone (curlone). In this work, we
analysed novel turmeric-oil blends in terms of oxidation and thermal stability in comparison to
that of virgin transformer oil. The DPPH assay confirmed that addition of these blends into the
oil increased its ability to scavenge the free radical DPPH. Thermogravimetric analysis showed
an increase in thermal stability when compared to that of virgin unblended oil. Evidently
blending of synthetic antioxidants/turmeric extract has potential to enhance the performance and
increase the life-span of transformer oils. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2012.
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