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Liquid-liquid equilibria related to the separation of organic acidsXhakaza, Nokukhanya Mavis January 2012 (has links)
Submitted in fulfilment of the requirements of the Masters Degree in Technology: Chemistry, Durban University of Technology, 2012. / The thesis involves a study of the thermodynamics of ternary liquid mixtures involving carboxylic acids with sulfolane, hydrocarbons and acetonitrile. Carboxylic acids are an important group of polar compounds with many industrial and commercial uses and applications. In South Africa, these carboxylic acids together with many other oxygenates and hydrocarbons are manufactured by SASOL using the Fischer–Tropsch process. The separation of these acids from hydrocarbons is a commercially viable option, and is an important reason for this study. This work focuses on the use of sulfolane in effecting separation by solvent extraction and not by the more common and energy intensive method of distillation. Sulfolane was chosen because of its high polarity and good solvent extraction properties.
The first part of this study involves the determination of excess molar volumes (VmE) of binary mixtures of sulfolane (1) + carboxylic acids (2) at different temperatures of 303.15 K and 308.15 K, where carboxylic acids refer to acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid respectively. The densities of the binary systems of sulfolane (1) + carboxylic acids (2) were measured at T = 303.15 K and 308.15 K. The excess molar volumes were calculated from the experimental densities at each temperature. The VmE were negative for the entire mole fractions for all the binary systems. It was found that the VmE in the systems studied increase with an increase in temperature, and also VmE decreases with an increase in the carbon chain length of the carboxylic acid. The VmE data results were correlated using Redlich-Kister equation.
Abstract ii
The second part was the study of the binodal or solubility curves and tie line data for the ternary systems of [sulfolane (1) + carboxylic acids (2) + hydrocarbons (3)] and [acetonitrile (1) + carboxylic acids (2) + hydrocarbon (3)].
Hydrocarbons refer to pentane, hexane, dodecane and hexadecane. The binodal curve experimental data was determined by the cloud point technique. Liquid-liquid equilibrium (LLE) phase diagrams were constructed using the mole fractions and refractive indices (nD). Tie line data were obtained for the sulfolane-rich and hydrocarbon-rich phases as well as the acetonitrile-rich and hydrocarbon-rich phases respectively. The tie lines in both cases were skewed towards the hydrocarbon-rich phases indicating that relative mutual solubility of carboxylic acids is higher in the hydrocarbon-rich phase than in the solvent-rich phase. Selectivity values were calculated from the tie-lines to determine the extraction capabilities of solvents sulfolane and acetonitrile. Selectivity values in all cases were greater than one, meaning that both sulfolane and acetonitrile can be used to separate carboxylic acids from hydrocarbons. Binodal curve data were correlated by the Hlavatý, beta (𝛽) and log𝛾 equations; average standard deviation error for Hlavatý was 0.012, for beta (𝛽), 0.023 and for log𝛾, 0.021. The NRTL and UNIQUAC models were used to correlate the experimental tie-lines. The calculated values based on the NRTL equation were found to be better than those based on UNIQUAC equation; the average root-mean square deviation, (rmsd), between the phase composition obtained from experiment and that from calculation was 0.061 for the NRTL model, as compared to 0.358 for UNIQUAC model for the ternary systems involving sulfolane. For ternary systems of acetonitrile, the NRTL equation was better than the UNIQUAC with the rsmd of 0.003 and 0.287for UNIQUAC equation. / DUT Postgraduate Development and Support Directorate (PGDS)
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Phase equilibrium studies of sulfolane mixtures containing carboxylic acidsSithole, Nompumelelo Pretty January 2012 (has links)
Submitted in fulfilment of the academic requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, 2012. / In this work, the thermodynamics of ternary liquid mixtures involving carboxylic acids with sulfolane, hydrocarbons including cycloalkane, and alcohols are presented. In South Africa, Sasol is one of the leading companies that produce synthesis gas from low grade coal. Carboxylic acids together with many other oxygenate and hydrocarbons are produced by Sasol using the Fischer-Tropsch process. Carboxylic acids class is one of the important classes of compounds with great number of industrial uses and applications. The efficient separation of carboxylic acids from hydrocarbons and alcohols from hydrocarbons is of economic importance in the chemical industry, and many solvents have been tried and tested to improve such recovery. This work focussed on the use of the polar solvent sulfolane in the effective separation by solvent extraction and not by more common energy intensive method of distillation.
The first part of the experimental work focussed on ternary liquid-liquid equilibria of mixtures of [sulfolane (1) + carboxylic acid (2) + heptane (3) or cyclohexane or dodecane] at T = 303.15 K, [sulfolane (1) + alcohol (2) + heptane (3)] at T = 303.15 K. Carboxylic acid refers to acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid. Alcohol refers to methanol, ethanol, 1- propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol and 2-methyl-2-propanol. Ternary liquid- liquid equilibrium data are essential for the design and selection of solvents used from liquid- liquid extraction process.
Abstract vi
The separation of carboxylic acids from hydrocarbons and the alcohols from hydrocarbons is commercially lucrative consideration and is an important reason of this study. The separation of carboxylic acids or alcohols from hydrocarbons by extraction with sulfolane was found to be feasible as all selectivity values obtained are greater than 1.
The modified Hlavatý, beta (β) and log equations were fitted to the experimental binodal data measured in this work. Hlavatý gave the best overall fit as compared to beta ( ) and log function.
The NRTL (Non-Random, Two Liquid) and UNIQUAC Universal Quasichemical) model were used to correlate the experimental tie-lines and calculate the phase compositions of the ternary systems. The correlation work served three purposes:
to summarise experimental data
to test theories of liquid mixtures
prediction of related thermodynamics properties.
The final part of the study was devoted to the determination of the excess molar volumes of mixtures of [sulfolane (1) + alcohol (2)] at T = 298.15 K, T = 303.15 K and T = 309.15 K. Density was used to determine the excess molar volumes of the mixtures of [sulfolane (1) + alcohols (2)]. Alcohol refers to methanol, ethanol, 1- propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol.
The work was done to investigate the effect of temperature on excess molar volumes of binary mixtures of alcohols and sulfolane, as well as to get some idea of interactions involved between an alcohol and sulfolane. The excess molar volume data for each binary mixture was fitted in the Redlich–Kister equation to correlate the composition dependence of the excess property. / National Research Foundation
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Phase equilibrium studies of sulfolane mixtures containing carboxylic acidsSithole, Nompumelelo Pretty 20 August 2012 (has links)
Submitted in fulfilment of the academic requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, 2012. / National Research Foundation
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The adsorption characteristics of precious and base metals on four different ion-exchange resinsEls, Ellis Raymond 12 1900 (has links)
Dissertation PhD--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Adsorption tests were conducted with four different ion-exchange resins to determine
the equilibrium adsorption of a range of precious and base metals. The adsorption
characteristics were determined for synthetic single metal, as well as for multicomponent
and base metal solutions. The effect of the el- concentration on the
equilibrium adsorption was established for three different Hel concentrations in the
above solutions. From the ion-exchange characteristics determined, a selective
adsorption sequence is proposed for the separation of precious and base metals.
Pure platinum, palladium and gold were dissolved in aqua regia and diluted to 2000
ppm (as metal) in 4M Hel. Ruthenium, rhodium and iridium were dissolved from
pure salts in Hel. A 2000 ppm base metal solution was prepared by dissolving all the
required components, including precious metals, to match an in-plant industrial basemetals
solution composition. For each precious metal the equilibrium adsorption was
determined for a couple of solution concentrations. Data points for adsorption curves
were established by varying the amount of resin added to the test solution of a specific
concentration. The equilibrium solution concentrations were determined by Iep
analysis after 24 hours of exposure, using the bottle-roll technique.
The experimental results obtained indicate a possible process route for the separation
of precious metals with ion-exchange resin. The XAD7 resin is highly selective for
gold from mixed solutions containing precious and base metals. It is also evident that,
with the gold removed from the solution, the A22 resin adsorbs only palladium.
IR200 resin adsorbs only the base metals from the solution. With all other precious
metals removed from the solution (platinum and ruthenium must be extracted by other
means), iridium can be adsorbed from the solution by IRA900 resin which is highly
selective for iridium over rhodium. For all of the anion resins, XAD7, IRA900, and
A22, the chloride concentration of the solution did not have a big effect on the
adsorption capacity. However, the adsorption of base metals on IR200 is sensitive to
chloride concentration, with a rapid reduction in adsorption at higher chloride
concentrations. Statistical models were developed for the adsorption of each of the precious metals,
as well as for the base metal solution. All adsorption data, obtained for a resin
(typically 250 equilibrium data points), was used in the development of the model.
The SPSS statistical software package was used to develop linear regression models.
The interaction between all the input parameters, e.g. the interaction of gold and
chloride ions, was modelled by specifying the product of the gold and the chloride
concentrations as an input variable. The variables that determine the adsorption
quantities were identified.
High solution concentrations of the target adsorption component increase the
adsorption quantity. It has been established that a higher platinum concentration
increases the adsorption quantity of gold on XAD7 resin. However, the adsorption
quantity is reduced at higher ruthenium concentrations. The adsorption quantity of
iridium on IRA900 is reduced with increased rhodium concentration. The adsorption
quantity of palladium on A22 is increased by the presence of rhodium and decreased
by larger concentrations of iridium and platinum. The adsorption of base metals on
IR200 is decreased at higher acid concentrations. Higher concentrations of gold in the
base metal solution also decrease the adsorption quantity of base metals. The model
predicted adsorption of each component compares well with the actual measured
values.
In batch adsorption tests the counter ion is not removed from the resin. The resin
capacity for a specific ion concentration could therefore not be determined. As such,
the adsorption models are only valid for the initial part of the ion-exchange process.
The effect of kinetics on the adsorption was not determined. / AFRIKAANSE OPSOMMING: Adsorpsietoetse is gedoen met vier verskillende ioonuitruilharse om die ewewig
adsorpsie van edelmetale en basismetale te bepaal. Die adsorpsie karakteristieke is
bepaal vir sintetiese enkelmetaal-, meermetaal-, en basismetaaloplossings. Die effek
van die Cl konsentrasie op die ewewigadsorpsie is bepaal vir drie
soutsuurkonsentrasies in al die bogenoemde oplossings. 'n Prosesvloeidiagram vir die
selektiewe adsorpsie van edelmetale en basismetale met behulp van die vier
verskillende ioonuitruilharse word voorgestel.
Suiwer platinum, palladium en goud is opgelos in koningswater en verdun na 2000
dpm (uitgedruk as metaal) in 4 molaar HCl. Rutenium-, rodium- en
iridiumoplossings is verkry deur die oplos van suiwer edelmetaalsoute in HCl. 'n
Basismetaaloplossing van 2000 dpm is voorberei deur die individuele komponente,
wat die edelmetale ingesluit het, in die regte verhouding te kombineer om die
samestelling van 'n industriële basismetaaloplossing te verkry. Vir elke edelmetaal is
die ewewigadsorpsie bepaal vir tipies twee konsentrasies van edelmetaaloplossings.
Verskillende data punte by 'n spesifieke edelmetaalkonsentrasie is bepaal deur die
hoeveelheid hars wat by die toets oplossing gevoeg word te varieer. Die
oplossingkonsentrasies by ewewig is bepaal deur IGP analise na 24 uur blootstelling
met die roterende botteltegniek.
Die resultate wat verkry is dui op 'n moontlike ioonuitruiigebaseerde proses vir die
skeiding van edelmetale. Die XAD hars is selektief vir goudadsorpsie uit gemengde
oplossings wat al die edelmetale, asook basismetale bevat. Dit is ook bevind dat
indien goud uit die gemengde oplossing verwyder word, die A22 hars slegs
palladium adsorbeer uit die oplossing. Die IR200 hars adsorbeer slegs basismetale.
Wanneer al die ander edelmetale uit die oplossing verwyder is (platinum en rutenium
moet met alternatiewe prosesse verwyder word) kan iridium geadsorbeer word met
!RA900 hars vanuit 'n iridium- en rodium- gemengde oplossing. Vir al drie die
anioonharse wat getoets is, naamlik, XAD7, !RA900 en A22, het die
chloriedkonsentrasie nie 'n groot effek op die adsorpsie gehad nie. Die hoeveelheid basismetale wat op IR200 hars geadsorbeer word is egter baie sensitief vir die
chloriedkonsentrasie, met 'n vinmge afname In adsorpsie by hoër
chloriedkonsentrasies.
Statistiese modelle is ontwikkel vir elke hars en vir elk van die edelmetale, asook die
basismetaaloplossing. Al die eksperimentele data wat vir elke hars verkry is, tipies
250 ewewigspunte, is gebruik in die ontwikkeling van lineêre regressie modelle vir
die primêre absorberende spesie op die hars.
Hoër konsentrasies van die teiken adsorpsie komponent verhoog die adsorpsie
daarvan. Hoër platinumkonsentrasies verhoog die adsorpsie van goud op XAD7,
maar die teenwoordigheid van rutenium verlaag adsorpsie. Die adsorpsie van iridium
op IRA900 word verlaag met hoër rodiumkonsentrasies. Die adsorpsie van palladium
op A22 verhoog met die teenwoordigheid van rodium, maar neem af met hoër
konsentrasies van iridium en platinum. Die adsorpsie van basismetale op IR200 neem
af by hoër suurkonsentrasies. 'n Hoër goudkonsentrasie verlaag ook die adsorpsie van
basismetale. Die gemodelleerde adsorpsie hoeveelhede vergelyk goed met die gemete
waardes.
Aangesien die uitgeruilde ioon nie verwyder word uit die toetsoplossing nie, kon die
harskapasiteit vir 'n spesifieke ioonkonsentrasie nie bepaal word nie. Die modelle is
derhalwe slegs getoets vir die aanvanklike deel van die ewewigsdata en die kinetika
van adsorpsie is nie in ag geneem nie.
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The use of ion-exchange resins for the recovery of valuable species from slurries of sparingly soluble solidsDe Villiers, Pieter Gabriel Retief 12 1900 (has links)
Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The availability of vast deposits of high-grade ore bodies are rapidly becoming
something of the past in the modern mining and metallurgical scenario. Apart from the
lower grade content of these ore bodies, complex mineralogy are an even greater
obstacle in the recovery of valuable metal species. The development of new technology to
deal with these type of ore bodies is therefore critical and worth investigating, as the
world's easily exploitable high grade ore deposits are decreasing.
Valuable species can be recovered from sparingly soluble solids, which slightly
dissociate to give traces of the valuable ions in solution, with the use of ion-exchange
resins in a slurry mixture. A dissociation equilibrium exists between the dissolved ions in
solution and the solid ore body. Jf the dissolved ions are removed from the solution by
ion-exchange, the solid / liquid dissociation equilibrium is continually displaced.
According to Le Chatelier's principle further dissolution of the sparingly soluble solid is
required to restore the equilibrium concentration of the valuable species in solution.
It is possible to recover valuable metal species from metal precipitates, such as metal
sulphides, by contacting a slurry of the precipitate with a suitable ion-exchange resin.
The resulting ion exchange reaction between the valuable metal species and counter ions
creates electrolyte solutions that may facilitate the further dissolution of the metal
precipitate. These counter ion electrolyte solutions may easily become significantly
concentrated. This occurs in the event of a Resin-in-Leach (RIL) mixture that results in a
continuous ion-exchange reaction taking place due to the continually changing
electrolyte composition of the mixture, which significantly changes the activities and
hence the solubility of the valuable metal species in solution. Complete dissolution and
liberation of the metal precipitate can often be achieved provided that a sufficient amount of a suitable high capacity ion-exchange resin is used in a properly engineered Resin-in-
Leach (RIL) circuit.
The simultaneous dissolution and adsorption of various base metal precipitates were
tested. Various interactions that take place in the slurry at molecular level as well as the
effects of various variables on the "adsorption by dissolution process" are discussed
through the development of fundamental thermodynamic models. These thermodynamic
mathematical models are developed for the three phase system that exists in a Resin-in-
Leach mixture, i.e. the solid ore body, the electrolyte solution and the ion-exchange resin,
and can be used for possible other applications such as the recovery of rare earths from
low grade ores in the minerals processing industry. A typical example of an industrial
process for the recovery of rare earth species is the percolation leaching of rare earths
from low-grade kaolinitic ores, which continually shifts the solid / liquid dissociation
equilibrium condition. The rare earth content of these ores is usually between 0.05%and
0.3 %, which is very low by any modern industrial extraction and refining standards. / AFRIKAANSE OPSOMMING: Die beskikbaarheid van ryk mineraal ertsneerslae is spoedig besig om iets van die
verlede te word in die huidige mineraalontginning en metallurgiese veredelings
industrie. Afgesien van die lae graad van die huidige mineraal ertsneerslae, blyk die
komplekse mineralogiese samestelling van hierdie neerslae In veel groter struikelblok te
wees in die herwinning en veredeling van die edelmetale teenwoordig in hierdie ertse.
Die ontwikkeling van nuwe veredelings en ekstratiewe tegnologie vir die herwinning van
edel metale, vanuit hierdie lae graad mineraal ertsneerslae, word dus benodig wat
verdere navorsing in hierdie gebied regverdig.
Dit is wel moontlik om metaal spesies afkomstig van ertse met 'n baie lae oplosbaarheid
in waterige oplossings te herwin met ioon-uitruilings harse vanweë die feit dat die metaal
spesies wel teen baie lae konsentrasies in die waterige oplossings teenwoordig is. Die
metaal spesies los op in die waterige oplossings volgens hulle karakteristieke oplossings
termodinamika. Indien die opgeloste metaal spesies vanuit die waterige oplossing
verwyder word, sal die vaste stof / vloeistof ewewigs balans weer herstel word deurdat
die vaste stof verder saloplos as gevolg van Le Chatelier se beginsel.
Dit is dus moontlik om metaalagtige spesies, soos metaal sulfiedes, te herwin deur 'n
waterige oplossing wat die metaal erts bevat in kontak te bring met 'n ioon-uitruilings
hars. Die daaropvolgende ioon-uitruilings reaksie tussen die metaalagtige spesies en die
spesies teenswoordig op die ioon-uitruilingshars het tot gevolg dat die elektrolitiese
samestelling van die waterige oplossing verander. Dit is die gevolg van die migrasie van
spesies aanvanklik teenswoordig op die hars wat in die waterige fase eindig. Die
veranderende samestelling van die waterige oplossing mag verder tot gevolg hê dat die
oplosbaarheid van die metaalagtige spesie verder verhoog mag word. Die gevolg van bogenoemde reaksies is dat die waterige oplossing ionies sterk gekonsentreerd kan word
soos meer en meer spesies aanvanklik teenswoordig op die hars migreer na die oplossing.
Die ioniese verandering van die waterige oplossing van 'n suiwer waterige fase tot 'n
ionies sterk gekonsentreerde oplossing vind plaas tydens die oplos van erste in 'n hars-inpulp
(HIP) oplossing. Die nuwe ioniese aktiwiteit in die oplossing kan die oplosbaarheid
van die vaste stof drasties verander. Die volledige oplossing van 'n bepaalde kwantiteit
van die vaste stof kan bereik word deur die genoegsame toevoeging van 'n geskikte hars
tot die waterige oplossing wat die vaste stofbevat.
Die gelyktydige oplossing en absorpsie van die metaalagtige vastestowwe vanuit waterige
oplossings met behulp van ioon-uitruilings harse is eksperimenteel getoets vir die
doeleindes van hierdie werkstuk. Verskeie interaksies wat op molekulêre vlak in die pulp
plaasvind asook die adsorpsie proses van die spesies vanuit die waterige oplossing op die
harse word bespreek en gemodelleer. Wiskundige modelle wat die termodinamika van
die verskillende fases wiskundig verteenwoordig is ontwikkel vanaf bestaande
termodinamiese beginsels. Die drie verskillende fases wat in ag geneem is, is die
waterige fase met opgeloste metaal spesies, die vaste stof fase wat as die erts in bostaande
paragrawe beskryf is en die ioon-uitruilings fase wat 'n komplekse vastestof en water fase
gekombineerd is. Die doel van die werkstuk is om die basis te skep vir die ontwikkeling
van modelle wat gebruik kan word om die herwinning van skaars-aarde mertale vanuit lae
oplosbare erstse te modelleer en beskryf. 'n Tipiese industriële voorbeeld is die
herwinning van skaars-aarde metale van lae-graadse kalkagtige erste deur gebruik te
maak van perkolerende logings reaksies wat geduring die vastestof / vloeistof ewewig
versteur. Die konsentrasie van die skaars-aarde metale in hierde erts gesteentes kan
wissel vanaf so laag as 0.05% tot 0.3% per massa. Hierdie konsentrasies is uiters laag
gesien vanuit enige industriële herwinnings proses oogpunt.
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A de-coupled level controller for cascaded flotation processesVan Heerden, Jacobus P. (Jacobus Petrus) 03 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Flotation was introduced early in the zo" century as a separation process for
extracting valuable minerals from grinded ore. Today flotation is a dominant mineral
concentration method and is used for almost all sulphide minerals and also for nonsulphide
metallic minerals, industrial minerals, and coal.
Automation and control has become a basic requirement in flotation plants. Effective
control of pulp levels plays a very important role in stabilising the flotation process
and therefore requires careful attention.
This thesis presents a de-coupled level controller that has been developed for the
control of levels in cascaded flow processes, including multi-tank cascaded flotation
processes. The controller was developed on a two tank cascaded pilot plant using
water as a flow medium. A simulation model was constructed for the cascaded flow
process. The simulation model made it possible to develop and evaluate a decoupled
level controller in a simulation environment. Finally independent loop PIO
control and integrated PIO control loops with feed-forward de-coupling were
compared through simulation, as control strategies for the pilot plant. / AFRIKAANSE OPSOMMING: Flotasie is vroeg in die 20ste eeu bekend gestel as 'n skeidingsproses om
waardevolle minerale te onttrek uit fyngemaalde erts. Vandag is flotasie die
dominante proses om minerale te konsentrasie en word gebruik vir byna aile sulfied
minerale sowel as nie-sulfied metaal minerale, industriele minerale and steenkool.
Outomatisasie en beheer het 'n basiese vereiste geword in flotasie aanlegte. Die
effektiewe beheer van pulpvlakke speel 'n baie belangrike rol in die stabilisering van
die flotasie proses en verdien om hierdie rede deeglike aandag.
Hierdie tesis stel 'n ontkoppelde vlakbeheerstelsel voor wat ontwikkel is vir die
beheer van vlakke in kaskade vloei prosesse byvoorbeeld multi-tenk flotasie
prosesse. Die beheerstelsel is ontwikkel op 'n twee-tenk kaskade toetsaanleg met
water as vloeimedium. 'n Volledige simulasiemodel is ontwikkel wat dit moontlik
gemaak het om die vlakbeheerstelsel te ontwerp, toets en verfyn in 'n simulasie
omgewing. Verder is die verskil tussen onafhanklike enkellus PID beheerders en
ontkoppelde PID beheerlusse ondersoek en word in die tesis geillustreer.
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Preparation and characterisation of palladium composite membranes.Keuler, Johan Nico 12 1900 (has links)
Thesis (MScEng (Process Engineering))--University of Stellenbosch, 1997. / This study focuses on the preparation and characterization of palladium-silver-nickel composite membranes. Electroless plating was used to deposit thin metal films on aluminazirconia membrane supports. Palladium conversion, in the electroless palladium plating process, was optimized with the aim of minimizing expensive palladium losses. The effect of deposition order on alloy composition and heat treatment on structural characteristics of the composite membrane was investigated.
The inorganic support membranes were thoroughly cleaned and pretreated prior to plating to catalyze the surface. Factorial designs were used to obtain the maximum palladium conversion. Tetra amine palladium nitrate gave better solution stability and resulted in higher conversions than tetra amine palladium chloride. Buffer pH values of 9 to 11 caused little variation in palladium conversion. Moving outside this range resulted in a sharp decline in palladium conversion. At a pH of 9 to 11 the stabilizer is in the correct ionic form (EDTA3 and EDTA4,) to best stabilize the palladium ions, and hydrazine acts as a proper reducing agent. Significant interactions existed between the EDTA concentration (stabilizer) and hydrazine concentration (reducing agent) and between EDTA and temperature. The EDTA concentration was the most sensitive variable. A 27.5 g 10% tetra amine palladium nitrate solution per liter plating solution was used. Conversions exceeding 80% were obtained after three hours plating with 20 ml plating solution at the following conditions: temperatures from 71 to 77 DC, 40-60% molar excess hydrazine, EDTA:Pd-salt molar ratios between 30:1 and 40: 1 and buffer pH = 11.
Silver plating rates for two hours plating of up to 2 mg/cm2 were obtained using a dilute silver nitrate solution with hydrazine as reducing agent. Electroless nickel plating was performed in a low temperature bath (40 DC) with nickel sulphate as source of metal ions and sodium hypophosphite as reducing agent.
Metal films were fully characterized before and after heat treatment for 5 hours in a hydrogen atmosphere at 650 dc. Scanning electron microscopy (SEM) was used to analyze the surface structure. X-ray diffraction (XRD) patterns were taken to examine alloying and detect changes in the crystal structure .after heating. Energy dispersive X-ray maps (EDS) were used to visualize the diffusion process and particle induced X-ray emission (PIXE) was used to construct concentration profiles across the thickness of the metal films.
Palladium deposits were dense, but columnlike, with a purity of 99.75%. Silver deposits were non-homogeneous, in other words it did not cover the entire substrate. The purity of the silver films was 99.5%. The nickel films were about 97% pure, very dense and defect free. When silver was deposited on palladium, the alloy penetrated more than 3 microns into the support and the palladium and silver concentrations varied across the thickness of the film after heating. By depositing palladium on silver, there was very little penetration into the support membrane pores (about 1 micron) and the palladium to silver ratio remained constant across the thickness of the film after heating.
Silver-palladium-nickel alloy films call be prepared by first depositing silver, then palladium and finally nickel. During heat treatment, a counter diffusion process took place and the smaller nickel atoms penetrated into pores and defects that might be present in the palladium-silver solid solution. By adding more than 3% nickel, dense defect free films can be prepared, which is much thinner than conventional palladium-silver films. This method makes it possible to reduce the film thickness of dense, non-porous films to less than 5 microns, reducing fabrication cost and increasing the hydrogen flux through the film. Dense, non-porous palladium-silver films are usually in the range of 10-15 microns.
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The use of multidimensional GC techniques for the analysis of complex petrochemical productsVan der Westhuizen, Rina 12 1900 (has links)
90 leaves on CD format, preliminary i-ix pages and numbered pages 1-81. Includes bibliography, list of figures in color to pdf format (OCR). / Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The composition of petrochemical products obtained from Fischer Tropsch (FT) technologies is of the highest complexity possible and may contain thousands of components. Chemicals produced from FT feedstocks often contain trace level contaminants that can poison catalysts or that affect product performance in down-line processes. Single dimension GC analysis of these mixtures provides incomplete information because of lack of separation power. This study evaluates the separation power of heart-cut GC-GC, comprehensive GCxGC and sequential GC-GC for three selected challenging petrochemical applications. The fundamental theoretical aspects of the techniques are discussed. Oxygenates are removed as far as possible in C10 – C13 alkylation feedstocks, used in the production of linear alkyl benzenes, because the oxygenates may have deactivating effects on some expensive alkylation catalysts. Residual oxygenates may still be present and can consist of hundreds of components. Detection of individual components at ng/g levels is required. Heart-cut GC-GC is used to illustrate the separation and enrichment power for oxygenates in an alkylation feedstock. The stationary phase in the first dimension column was selected to provide separation of the oxygenates from the hydrocarbons in a relatively narrow window. The oxygenate fraction is then enriched by repeated injections and collection on the cryotrap. After sufficient enrichment, the trap is heated and the oxygenates are analysed on the second dimension column. Comprehensive GCxGC and Sequential GC-GC are compared for the separation and analysis of the oxygenated chemical component classes in the alkylation feedstock, before removal of oxygenates. Cyclic alcohols can occur in detergent alcohols produced from FT feedstocks. These cyclics are regarded as impurities because they affect the physical properties of the detergents. The cyclic and noncyclic alcohols in a narrow C12 – C13 detergent alcohol distillation cut have similar boiling points and polarities, and separation of individual components is thus difficult to achieve. Comprehensive GCxGC and sequential GC-GC are evaluated for the separation of the alcohol component classes. The study shows that both approaches provide component class separation but the high resolving power of the second column and the optimal chromatographic operating conditions of sequential GC-GC provide better separation of the individual components. The study illustrates the immense power of the three multidimensional GC techniques namely heart-cut GC-GC, comprehensive GCxGC and sequential GC-GC. The three multidimensional GC techniques each have their own advantages, disadvantages and unique applications and should be used as complementary rather than as competitive analytical tools. / AFRIKAANSE OPSOMMING: Fischer Tropsch (FT) petrochemiese produkte is van baie hoë kompleksiteit en kan uit duisende komponente bestaan. Chemikalië afkomstig van dié voerstrome bevat soms spoorhoeveelhede onsuiwerhede wat deaktiverend op kataliste kan inwerk of wat die werkverrrigting van finale produkte kan beïnvloed. Enkeldimensie GC analises van die komplekse mengsels is meesal onakkuraat as gevolg van geweldige piekoorvleueling. Die studie evalueer die skeidingsvermoë van drie multidimensionele tegnieke, Heart-cut GC-GC, Comprehensive GCxGC en Sequential GC-GC vir geselekteerde petrochemiese toepassings. Die fundamentele teoretiese aspekte van die tegnieke word bespreek en drie analitiese toepassings word beskryf. Oksigenate word so ver moontlik verwyder uit C10 – C13 paraffien-voerstrome, wat gebruik word in die vervaardiging van liniêre alkielbenzene, aangesien dit deaktiverend kan inwerk op alkileringskataliste. Die oorblywende oksigenate kan uit honderde komponente bestaan sodat analise van individuele komponente tot op lae ng/g vlakke nodig is. Heart-cut GC-GC word gebruik om die skeiding en verryking van die oksigenate in die alkileringsvoerstroom te illustreer. Die stationêre fase in die eerste-dimensie kolom is so gekies dat skeiding tussen oksigenate en koolwaterstowwe verkry word. Met herhaalde inspuitings verhoog die oksigenaat-konsentrasie op die cryo val en - na voldoende verryking - word die val verhit en die oksigenate geanaliseer op die tweede dimensie kolom. Die skeiding en analises verkry met Comprehensive GCxGC en Sequential GC-GC word vergelyk vir die chemiese klasse-skeiding van die alkileringsvoer (voor verwydering van oksigenate). Sikliese alkohole kan voorkom in detergent-alkohole vervaardig vanaf FT voerstrome. Dit word as onsuiwerhede beskou aangesien dit die fisiese eienskappe van die finale produkte beïnvloed. Die sikliese en nie-sikliese alkohole se kookpunte en polariteite is baie naby aanmekaar sodat skeiding van individuele komponente moeilik verkry word. Comprehensive GCxGC en Sequential GC-GC word evalueer vir die skeiding van die alkohol. Die studie toon aan dat albei die tegnieke skeiding gee van die chemiese komponent-klasse maar dat die hoë-resolusie tweede-dimensie kolom en die optimisering van die experimentele kondisies van die Sequential GC-GC sisteem beter skeiding van individuele komponente gee. Die uitsonderlike skeidingsvermoë van die drie multidimensionele tegnieke, Heart-cut GC-GC, Comprehensive GCxGC en Sequential GC-GC word geïllustreer in die studie. Elke tegniek het sy eie voordele, nadele en unieke toepassings en die drie tegnieke behoort as komplementêre eerder as kompeterende tegnieke gebruik te word.
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Evaluation of pressure- and electrodriven separation techniques for the determination of phenolic compounds in wineDe Villiers, A. J. (Andre Joubert) 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The phenolic content of wine is responsible for determining characteristics such as the
organoleptic qualities, colour stability, ageing properties and health-beneficial effects
associated with wine. The aim ofthis study was to investigate the possibilities offered by
capillary electrophoresis (CE) as an alternative separation technique to high performance
liquid chromatography (HPLC) for the analysis of polyphenols in wine. The complexity
of wine samples was the cause that neither technique was capable of a satisfactory singlestep
analysis of wine. Suitable sample preparation techniques such as Sephadex- and Sep-
Pak fractionation and ether extraction of wine polyphenols were investigated. These
techniques did not, however, prove to be universal. A novel form of sample preparation
namely a process analogous to lyophylization used to separate wine volatiles from nonvolatiles
was introduced.
The versatility of CE was further investigated in an attempt to eliminate the need for
sample preparation. The use of polyvinylalcohol (PVA) coated capillaries, micellar
electrokinetic chromatography (MEKC) and capillary gel electrophoresis (CGE) were
investigated in this regard. Although none of these techniques could offer conclusive
results, useful applications were forthcoming and routes for further investigation were
outlined. Liquid chromatography coupled to electro spray ionisation mass spectroscopy
(LC-ESI-MS) and capillary electrophoresis coupled to electro spray ionisation mass
spectroscopy (CE-ESI-MS) were compared for the analysis of polyphenols in wine.
While the latter technique could not produce sufficient separation compared to the
former, future development ofCE-ESI-MS should make it a powerful technique for these
analyses. / AFRIKAANSE OPSOMMING: Die fenoliese komponente in wyn speel 'n bepalende rol by eienskappe soos die
organoleptiese karakter, kleur stabiliteit, verouderingspotensiaal en gesondheids-voordele
wat met wyn geassosieër word. Die doel van hierdie projek was om ondersoek in te stel
na die potensiaal wat kapillêre elektroforese (CE, "capillary electrophoresis") as 'n
alternatiewe skeidingstegniek teenoor hoë druk vloeistof chromatografie (HDVC) vir die
analise van die polifenole in wyn bied. Die kompleksiteit van wyn monsters is van so 'n
aard dat 'n bevredigend enkelstap analise met geeneen van die tegnieke moontlik is nie.
Gepaste monster-voorbereidingstappe soos Sephadex- en Sep-Pak fraksionering asook
eter ekstraksie van die polifenole in wyn is ondersoek. Geeneen van die tegnieke was
egter universeel toepaslik nie. 'n Nuwe metode van monster-voorbereiding, naamlik 'n
proses analoog aan liofilisasie wat gebruik word om die wyn te skei in vlugtige en nievlugtige
komponente is gedemonstreer.
Die veelsydigheid van CE was gevolglik ondersoek in 'n poging om
monstervoorbereiding uit te skakel. Die gebruik van polyvinielalkohol-(pVA) bedekte
kapillêre, missellêre elektrokinetiese chromatografie (MEKC) en kapillêre gel
elektroforese (CGE, "capillary gel electrophoresis) is in hierdie verband ondersoek.
Alhoewel geeneen van hierdie tegnieke onweerlegbare resultate gelewer het nie, het
bruikbare toepassings hieruit voortgespruit en is die grondslag vir verdere navorsing gelê.
Vloeistof chromatografie gekoppel aan eIektrosproei ionisasie massaspektroskopie (LCESI-
MS) en kapillêre elektroforese gekoppel aan elektrosproei ionisasie massaspektroskopie
(CE-ESI-MS) is vergelyk vir die analise van polifenole in wyn. Alhoewel
laasgenoemde tegniek onvoldoende skeiding lewer vergeleke met eersgenoemde, behoort
toekomstige ontwikkelinge op die gebied van CE-ESI-MS dit 'n kragtige tegniek vir die
analise van hierdie monsters te maak.
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A study on the reversible photo-induced isomerisation of platinum(II) and palladium(II) complexes of the N,N-dialkyl-N’-acyl(aroyl)thioureas with reversed-phase HPLC separation from related rhodium(III), ruthenium(III) and iridium(III) complexesNkabyo, Henry Ane 04 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: See item for full text / AFRIKAANSE OPSOMMING: Sien item vir volteks
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