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Reaction kinetics of the iron-catalysed decomposition of SO3 / Abraham Frederik van der MerweVan der Merwe, Abraham Frederik January 2014 (has links)
In this study the performance of pure, very fine iron (III) oxide powder was investigated as catalyst for the decomposition of sulphur trioxide into sulphur dioxide and oxygen. This highly endothermic reaction requires a catalyst to lower the reaction temperature. This reaction forms part of the HyS (Hybrid Sulphur) cycle, a proposed thermochemical process for the industrial scale production of hydrogen and oxygen from water.
The study aimed at obtaining reaction kinetics for this reaction employing pure, unsupported iron (III) oxide as catalyst as a cheaper alternative compared to supported iron catalysts.
It was found that the SO3 conversion was carried out in the absence of diffusion limitations and that the reverse reaction did not play a significant role. By assuming plug flow conditions in the reactor and 1st order kinetics, the kinetic parameters of the reaction were obtained.
These parameters that form part of the Arrhenius law in describing the reaction rate constant, were determined to be 118(±23) kj / mol for the activation energy ( Ea ), and a value of 3(±0.5) x 108hr-1 was obtained for the Arrhenius frequency factor ( A ). Both values correspond to literature, although in general larger activation energies were published for iron (III) oxide derived supported catalysts.
A comparison of the performance of the pure, unsupported iron (III) oxide catalyst with other iron (III) oxide derived supported catalysts (or pellets) has shown that the pure iron (III) oxide catalyst exhibit similar activities. Avoiding expensive catalyst preparation will be an initial step in the direction of developing a cost effective catalyst for the decomposition of sulphur trioxide. It is, however, recommended to investigate different particle sizes as well as purity levels of the unsupported iron (III) oxide to find an optimum cost to performance ratio, as the degree of fineness and the degree of purity will largely influence the final catalyst cost.
A qualitative investigation with various reaction product species as well as water in the reactor feed was conducted to assess the influence of these species on the reaction rate. The addition of these species seems to have a larger influence on the reaction rate at low reaction temperatures around 700°C than at higher reaction temperatures (i.e. 750°C and 825°C). This can be attributed to adsorption rates of such species that reduce at higher temperatures. Observations at higher reaction temperatures also suggest that the reaction is of a first-order nature. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2014
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Reaction kinetics of the iron-catalysed decomposition of SO3 / Abraham Frederik van der MerweVan der Merwe, Abraham Frederik January 2014 (has links)
In this study the performance of pure, very fine iron (III) oxide powder was investigated as catalyst for the decomposition of sulphur trioxide into sulphur dioxide and oxygen. This highly endothermic reaction requires a catalyst to lower the reaction temperature. This reaction forms part of the HyS (Hybrid Sulphur) cycle, a proposed thermochemical process for the industrial scale production of hydrogen and oxygen from water.
The study aimed at obtaining reaction kinetics for this reaction employing pure, unsupported iron (III) oxide as catalyst as a cheaper alternative compared to supported iron catalysts.
It was found that the SO3 conversion was carried out in the absence of diffusion limitations and that the reverse reaction did not play a significant role. By assuming plug flow conditions in the reactor and 1st order kinetics, the kinetic parameters of the reaction were obtained.
These parameters that form part of the Arrhenius law in describing the reaction rate constant, were determined to be 118(±23) kj / mol for the activation energy ( Ea ), and a value of 3(±0.5) x 108hr-1 was obtained for the Arrhenius frequency factor ( A ). Both values correspond to literature, although in general larger activation energies were published for iron (III) oxide derived supported catalysts.
A comparison of the performance of the pure, unsupported iron (III) oxide catalyst with other iron (III) oxide derived supported catalysts (or pellets) has shown that the pure iron (III) oxide catalyst exhibit similar activities. Avoiding expensive catalyst preparation will be an initial step in the direction of developing a cost effective catalyst for the decomposition of sulphur trioxide. It is, however, recommended to investigate different particle sizes as well as purity levels of the unsupported iron (III) oxide to find an optimum cost to performance ratio, as the degree of fineness and the degree of purity will largely influence the final catalyst cost.
A qualitative investigation with various reaction product species as well as water in the reactor feed was conducted to assess the influence of these species on the reaction rate. The addition of these species seems to have a larger influence on the reaction rate at low reaction temperatures around 700°C than at higher reaction temperatures (i.e. 750°C and 825°C). This can be attributed to adsorption rates of such species that reduce at higher temperatures. Observations at higher reaction temperatures also suggest that the reaction is of a first-order nature. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2014
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Thermodynamic and kinetic modelling of iron (III) reduction with sulfur dioxide gasBiley, Chris 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Recent developments in the atmospheric treatment of low-grade nickel laterite ores at
Anglo American plc has culminated in the conceptual iron-focused laterite (ARFe) process.
In addition to the recovery of nickel and cobalt from laterite ore, this process
uniquely aims to recover iron as a saleable by-product. The reduction of soluble iron(III)
(Fe(III)) by sulfur dioxide gas (SO2) is central to the ARFe concept and represents a complex,
multiphase system involving simultaneous gas-liquid mass transfer, thermodynamic
speciation and chemical reaction. The chemistry of iron-containing systems is generally
poorly understood and accurately predicting their behaviour is challenging, especially
under aggressive hydrometallurgical conditions.
The primary objective of this work is the development of an engineering model capable
of describing the rate and extent of ferric reduction with SO2 under conditions
typical of the ARFe process. Thermodynamic considerations provide a rigorous framework
for the interpretation of chemical reactions, however little experimental data are
openly available for the associated solution species in acidic iron sulfate systems.
A key contribution of this work, and critical for the development of the overall model,
is the direct measurement of speciation in iron sulfate solutions. Raman and UV-vis
spectroscopy were utilised to make direct speciation measurements in the various subsystems
of the Fe2(SO4)3-FeSO4-H2SO4-H2O system that were previously unavailable in
the open literature. The FeSO+4 and Fe(SO4)–
2 species were explicitly identified and measurements
were supported and rationalised by static computational quantum mechanical
calculations and ultimately permit the calibration of a robust, ion-interaction solution model with the explicit recognition of the important solution species up to 1.6 mol/kg
Fe2(SO4)3, 0.8 mol/kg H2SO4 over 25 – 90 C.
Batch and continuous Fe(III) reduction kinetics were measured and the effects of initial
Fe2(SO4)3 and H2SO4 concentrations, temperature and in-situ neutralisation quantified.
The retardation effect of sulfuric acid was observed to be the most significant
factor influencing the initial reaction rate and the achievable extent of reduction at fixed
residence time, which varied between about 20 and 80 % after 180 minutes of reaction.
A reaction mechanism that is limited by the slow ligand-to-metal electron transfer
in the FeIIISO+3 solution species’ decomposition is proposed and spectroscopic measurements
and computational quantum mechanical calculations are used to support this
mechanism. A kinetic model, comprising a system of differential mass-balance equations,
is incorporated into the thermodynamic framework. This reaction model permits
the prediction of kinetic profiles over the full range of experimental conditions and can
be incorporated into more elaborate simulation models of the ARFe circuit.
The specific original contributions of this work are
• The direct measurement of aqueous speciation in the Fe2(SO4)3-H2SO4-H2O system
by Raman and UV-vis spectroscopy
• The development of a modelling framework to characterise speciation, activity coefficients
and solubility in the mixed Fe2(SO4)3-FeSO4-H2SO4-H2O system.
• The measurement of Fe(III) reduction kinetics using SO2 in concentrated sulfate
solutions as a function of initial composition and temperature.
• The development of a solution reaction model of Fe(III) reduction with SO2 that
accurately predicts the solution speciation and reaction rate with time as a function
of composition and temperature.
Lastly, the vast complexity of industrial systems will nearly always result in a lack
of specific experimental data that are required for the development of phenomenological
models. This work emphasises the crucial role that engineering studies hold in the generation
of such data to derive maximum practical value for industrial process development
and optimisation. / AFRIKAANSE OPSOMMING: Onlangse ontwikkelinge in die atmosferiese behandeling van lae-graad nikkel lateriet erts
by Anglo American plc het gelei tot die konseptuele yster gefokus lateriet (ARFe) proses.
Bykommend tot die herwinning van nikkel en kobalt uit laterite erts is hierdie proses
uniek en daarop gemik om yster te herwin as ’n verkoopbare by-produk. Die vermindering
van oplosbare yster(III) (Fe(III)) met swaeldioksied (SO2) is sentraal tot die ARFe
konsep en verteenwoordig ’n komplekse, multifase stelsel wat gelyktydige gas-vloeistof
massa-oordrag, termodinamiese spesiasie en chemiese reaksie behels. Die oplossingschemie
van ysterstelsels word, oor die algemeen, swak verstaan en om hul gedrag akuraat
te voorspel is ’n uitdaging, veral onder aggressiewe hidrometallurgiese kondisies.
Die primêre doel van hierdie werk is die ontwikkeling van ’n ingenieursmodel wat
die tempo en omvang van yster(III) vermindering met SO2 onder tipiese ARFe proses
toestande beskryf. Termodinamiese oorwegings stel ’n streng raamwerk voor vir die interpretasie
van chemiese reaksies, alhoewel daar egter min eksperimentele data openlik
beskikbaar is vir die gepaardgaande oplossing spesies in suur yster(III) sulfaat stelsels.
’n Belangrike bydrae van hierdie werk, en van kritieke belang vir die ontwikkeling van
die algehele model, is die direkte meting van spesiasie in yster(III) sulfaat oplossings.
Raman en UV-vis spektroskopie is gebruik om direkte spesiasie metings te maak in die
verskillende subsisteme van die Fe2(SO4)3-FeSO4-H2SO4-H2O stelsel wat voorheen nie
in die oop literatuur beskikbaar was nie. Die FeSO+4 en Fe(SO4)–
2 spesies is ekplisiet geïdentifiseer, terwyl die metings ondersteun en gerasionaliseer is deur statiese kwantummeganiese
berekeninge wat uiteindelik die kalibrasie van ’n robuuste, ioon-interaksie
model tot gevolg hê wat ook die belangrike oplossingspesies duidelik beklemtoon tot en
met 1.6 mol/kg Fe2(SO4)3, 0.8 mol/kg H2SO4 en tussen 25 – 90°C.
Enkellading en kontinue yster(III) verminderingskinetika is gemeet en die gevolge
van die aanvanklike Fe2(SO4)3 en H2SO4 konsentrasies, temperatuur en in-situ neutralisasie
is gekwantifiseer. Die waargeneemde vertragingseffek van swaelsuur is die mees
beduidende faktor wat die aanvanklike reaksietempo en die haalbare reaksie omvangsvermindering
na ’n vaste residensietyd van 180 minute bepaal, wat wissel tussen ongeveer
20 en 80%.
’n Reaksiemeganisme word voorgestel wat beperk word deur die stadige ligand-totmetaal
elektronoordrag in ontbinding van die Fe(III)SO+3 oplossing-spesies en wat verder
deur spektroskopiese metings en kwantummeganiese berekenings ondersteun word. A
kinetiese model, wat bestaan uit ’n stelsel van gedifferensieerde massa-balans vergelykings,
is in die termodinamiese raamwerk geïnkorporeer. Hierdie reaksie-model laat die
voorspelling van kinetiese profiele toe oor die volle omvang van die eksperimentele toestande
en kan in meer uitgebreide simulasie modelle van die ARFe proces geinkorporeer word.
Die spesifieke en oorspronklike bydraes van hierdie werk is
• Die direkte meting van die spesiasie in die Fe2(SO4)3-H2SO4-H2O stelsel deur
Raman en UV-vis spektroskopie
• Die ontwikkeling van ’n modelraamwerk om spesiasie, aktiwiteitskoëffisiënte en
oplosbaarheid in die gemengde Fe2(SO4)3-FeSO4-H2SO4-H2O stelsel te karakteriseer.
• Die meting van yster(III) vermideringskinetieka deur SO2 in gekonsentreerde sulfate
oplossings te gebruik as ’n funksie van die aanvanklike samestelling en temperatuur.
• Die ontwikkeling van ’n oplossingsreaksie-model van yster(III) vermindering met
SO2 wat die oplossing-spesiasie en reaksietempo met die tyd as ’n funksie van samestelling
en temperatuur akkuraat voorspel.
Laastens, die oorgrote kompleksiteit van industriële stelsels sal byna altyd lei tot ’n
gebrek van spesifieke eksperimentele data wat nodig is vir die ontwikkeling van fenomenologiese
modelle. Hierdie werk beklemtoon die belangrike rol wat ingenieursstudies
speel in die generasie van data wat sodanig tot maksimum praktiese waarde vir industriële
prosesontwikkeling en optimalisering lei.
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Estudo potenciométrico sobre a formação de complexos no sistema ferro (III)/azoteto, em meio não totalmente aquoso / Potentiometric study on the complexes formation in the iron (III)/azide system, in non totally aqueous mediumPimenta, Adriano Cesar 28 April 2006 (has links)
Neste trabalho, a complexação do sistema ferro-III/azoteto em meio áqüeo-orgânico foi estudada para avaliar a formação dessas espécies sob diferentes forças iônicas: 1,00; 2,00 e 3,00 mol L-1 e em presença de diferentes solventes: tetraidrofurano, acetona e p-dioxano (T = 20 °C). Além disso, em meio contendo tetraidrofurano, as constantes de formação condicionais (b) foram determinadas sob diferentes percentagens deste solvente: 20, 30 e 40 % (v/v). O método empregado na determinação de tais constantes baseia-se na competição entre o metal e o íon hidrogênio pelo azoteto, no sistema tampão formado entre o ligante e o ácido azotídrico (N3-/HN3). Os parâmetros necessários para o cálculo das constantes de formação foram obtidos potenciometricamente por meio de variações de pH, provocadas pela complexação após a introdução do metal à célula. Tais parâmetros foram tratados preliminarmente pelo método de Leden e, posteriormente, refinados com alguns programas computacionais visando à caracterização das espécies e a determinação dos valores das constantes de formação globais dos complexos coexistentes no sistema Fe (III)/N3-. Os resultados mostraram evidências de que até quatro espécies complexas estáveis: [Fe(N3)]2+, [Fe(N3)2]+, [Fe(N3)3] e [Fe(N3)4]- podem coexistir tanto em meio contendo acetona quanto naquele contendo p-dioxano. Porém, em meio contendo tetraidrofurano, somente as três primeiras espécies foram detectadas (evidenciadas). Isto indica que uma maior competição entre o solvente orgânico e o ligante azoteto, na esfera de coordenação do íon metálico, ocorre em meios contendo tetraidrofurano, nestas condições estudadas. Verificou-se ainda que tanto a percentagem de solvente orgânico quanto a força iônica do meio têm forte influência na formação dos complexos sucessivos investigados, sendo que os complexos de maior estabilidade foram obtidos em soluções contendo 40 % (v/v) de tetraidrofurano e força iônica de 1,00 mol L-1. Diante dos resultados obtidos, observa-se que o método competitivo adotado neste trabalho, usualmente empregado em estudos realizados em meio totalmente aquoso, também se mostrou apropriado para a determinação das constantes de formação nas condições experimentais investigadas (meios áqüeos-orgânicos). / In this work, the system the iron-III/azide in aqueous-organic media was studied in order to evaluate the formation of complexes under different conditions: ionic strengths in the range of 1.00 to 3.00 mol L-1 and effect of the presence of organic solvents (tetrahydrofuran, acetone and p-dioxan) at T = 20 °C. Besides, in medium containing tetrahydrofuran, the conditional formation constants (b) were determined under different proportions of this solvent (20-40 %, v/v). The method used in the determination of these constants is based on the competition between the metal and the hydrogen ion for the azide, in the buffered system formed between the ligand and the azotidric acid (N3-/HN3). The parameters for the determination of the formation constant of each complexe were obtained by potentiometric measurements, through changes on the solution pH, caused by complexation due the iron ions added into the cell. These parameters were initially analysed by using the Leden method and, subsequently, refined by computational simulation in order to characterize the different complexes in the Fe (III)/N3- system, as well as to determine the value for the global constant of formation for each coexistent species. The results showed the possible coexistence of following four stable complexes: [Fe(N3)]2+, [Fe(N3)2]+, [Fe(N3)3] e [Fe(N3)4]- in aqueous medium containing acetone or p-dioxan. However, in the presence of tetrahydrofuran, the [Fe(N3)4]- was not evidenced. This indicates that a larger competition between the molecules of this organic solvent and the azide ligand, into the coordination sphere of the metallic ion occurs under these experimental conditions. Besides, the organic solvent proportion and the experimental medium are important parameters affecting the formation of these complexes. It was observed that iron complexes with higher stability were produced in the presence of 40 % (v/v) tetrahydrofuran and 1.00 mol L-1 ionic strength. Before the obtained results, it is observed that the competitive method adopted in this work, usually employed in studies accomplished in totally aqueous medium, it was also shown appropriate for the determination of the formation constants in the experimental conditions (aqueous-organic media) investigated.
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Evaluation of the efficiency of treatment techniques in removing perfluoroalkyl substances from water / Utvärdering av behandlingstekniker för att rena vatten från perfluoralkylerade ämnenLundgren, Sandra January 2014 (has links)
Perfluoroalkylated substances (PFASs) are a group of synthetic compounds that have gained growing attention due to their environmental persistence, toxicity and their potential to bioaccumulate. Even though PFASs are not occurring naturally in our environment, they are globally distributed and can be found ubiquitously in air, water, soil, wildlife as well as in humans. PFASs have primarily been used, due to their unique properties of being both hydrophilic and hydrophobic, as surfactants in numerous products such as firefighting foams, paint, leather and textile coating. The occurrence of PFASs in drinking water as well as in wastewater makes it important to develop effective techniques to remove these compounds from drinking water sources and wastewater. To be able to effectively remove PFASs from drinking water and wastewater it is important to understand which treatment process is most efficient and how the removal efficiency is affected by the physicochemical properties of PFASs and characteristics of water. In this study, the removal efficiency of PFASs was investigated using six different water types with varying dissolved organic carbon (DOC) character. Four different treatment techniques were evaluated including anion exchange using MIEX® resins, coagulation with iron (III) chloride (FeCl3), adsorption using powdered activated carbon (PAC) and nanofiltration (NF) membrane. The batch experiments were performed in laboratory-scale for 14 individual PFASs including C3-11, C13 perfluoroalkyl carboxylic acids (PFCAs), C4, C6, C8 perfluoroalkyl sulfonic acids (PFSAs) and perfluorooctane sulfonamide (FOSA). The results showed that the removal efficiency of PFASs was dependent on both perfluorocarbon chain length as well as functional group, with an increase in removal efficiency with increased perfluorocarbon chain length. Short-chained PFASs (C!6) were removed in less extent than the long chained PFASs for all treatment techniques. Amongst the four treatment techniques investigated, NF membrane exhibited the best removal efficiency for both short- and long chained PFASs (on average, 51%). Lower removal efficiencies for PFASs were observed for MIEX (33%) < FeCl3 (16%) < PAC (14%). However, all tested treatment techniques used in this study exhibited generally low removal efficiency (< 78%), in particular for the short-chained PFASs (C!6, < 41%) Results using three different doses of PAC (i.e. 20, 50, 100 mg L-1) showed an increase in removal (i.e. 2.2-41%, 8.0-78% and 12-92% respectively) with increasing dose. No significant trends were found between PFAS removal and DOC removal for any of the treatments (p<0.05, student t-test). However, the removal efficiency was different of the six different water types, which indicates that the DOC characteristics (i.e. Freshness, humification index, pH and absorbance) have an influence on the removal efficiency of PFASs in water. / Perfluoroalkylerade ämnen (PFASer) är en grupp syntetiska ämnen som har fått allt större uppmärksamhet den senaste tiden då de har visat sig vara persistenta, toxiska och bioackumulerande. Även om PFASer inte förekommer naturligt i vår miljö är de globalt fördelade och kan återfinnas i luft, vatten, mark, djur och hos människor. PFASer har främst använts, på grund av sina unika egenskaper att vara både hydrofila och hydrofoba, som tensider i många produkter såsom brandsläckningsskum, färg, läder och textil. Förekomsten av PFASer i dricksvattentäkter och i många reningsverk gör det viktigt att utveckla effektiva metoder för att ta bort dessa föreningar i vattenreningsverk. För att effektivt kunna avlägsna PFASer från dricks- och avloppsvatten är det viktigt att ha kunskap om vilken behandlingsmetod som är effektivast och hur reningseffektiviteten påverkas av ämnenas fysikalisk-kemiska egenskaper och vattnets karaktär. Syftet med denna studie var att undersökta reningseffektiviteten för PFASer i sex olika vatten innehållande olika typer av löst organiskt kol (DOC). Detta undersöktes för fyra olika behandlingsteknikert; jonbyte med MIEX®, koagulering med järnklorid (FeCl3), adsorption med hjälp av pulveriserat aktivt kol (PAC) och nanofiltrering. Försöken gjordes små skaligt i laboratorie och 14 olika PFASer undersöktes; C3-11,13 perfluoralkyl karboxylsyror (PFCAer), C4, C6, C8, perfluoralkyl sulfonsyror (PFSAer) och perfluoroktan sulfonamid (FOSA). Resultaten visar att reningseffektiviteten för PFASer var beroende av både den perfluorerade kolkedjans längd och funktionell grupp, med en ökning av reningseffektivitet med längre perfluorerad kolkedja. PFASer med kort perfluorerad kolkedja (C≤6) renades i mindre utsträckning än PFASer med lång perfluorerad kolkedjade; detta gällde för alla behandlingstekniker. Bland de fyra behandlingstekniker som undersöktes uppvisade nanofiltreringen den bästa reningseffektiviteten för PFASer med både korta och långa kolkedjor (i genomsnitt, 51%.). Lägre reningseffektivitet för PFASer observerades för MIEX®(33%), < FeCl3(16%) < PAC (14%). Totalt sett erhölls en relativt låg reningseffektivitet (<78%) för samtliga reningstekniker, speciellt för de kortkedjade PFASer (C£6, < 41%). Resultat från försök med tre olika doser PAC (e.g. 20, 50, 100 mg L-1) visade på en ökad reningseffektivitet (2,2-41%, 8,0-78% och 12-92%) med ökad dos PAC. Inga signifikanta trender kunde urskiljas vad gäller reningseffektivitet av PFASer och rening av DOC (p<0.05, student t-test), detta gällde för samtliga behandlingstekniker. Det fanns dock tydliga skillnader i reningseffektivitet mellan de sex olika vattentyperna vilket indikerar på att DOC egenskaperna (Freshnessindex, humifieringsindex, pH, absorbans) har en påverkan på reningseffektiviteten för PFASer i vatten.
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Estudo potenciométrico sobre a formação de complexos no sistema ferro (III)/azoteto, em meio não totalmente aquoso / Potentiometric study on the complexes formation in the iron (III)/azide system, in non totally aqueous mediumAdriano Cesar Pimenta 28 April 2006 (has links)
Neste trabalho, a complexação do sistema ferro-III/azoteto em meio áqüeo-orgânico foi estudada para avaliar a formação dessas espécies sob diferentes forças iônicas: 1,00; 2,00 e 3,00 mol L-1 e em presença de diferentes solventes: tetraidrofurano, acetona e p-dioxano (T = 20 °C). Além disso, em meio contendo tetraidrofurano, as constantes de formação condicionais (b) foram determinadas sob diferentes percentagens deste solvente: 20, 30 e 40 % (v/v). O método empregado na determinação de tais constantes baseia-se na competição entre o metal e o íon hidrogênio pelo azoteto, no sistema tampão formado entre o ligante e o ácido azotídrico (N3-/HN3). Os parâmetros necessários para o cálculo das constantes de formação foram obtidos potenciometricamente por meio de variações de pH, provocadas pela complexação após a introdução do metal à célula. Tais parâmetros foram tratados preliminarmente pelo método de Leden e, posteriormente, refinados com alguns programas computacionais visando à caracterização das espécies e a determinação dos valores das constantes de formação globais dos complexos coexistentes no sistema Fe (III)/N3-. Os resultados mostraram evidências de que até quatro espécies complexas estáveis: [Fe(N3)]2+, [Fe(N3)2]+, [Fe(N3)3] e [Fe(N3)4]- podem coexistir tanto em meio contendo acetona quanto naquele contendo p-dioxano. Porém, em meio contendo tetraidrofurano, somente as três primeiras espécies foram detectadas (evidenciadas). Isto indica que uma maior competição entre o solvente orgânico e o ligante azoteto, na esfera de coordenação do íon metálico, ocorre em meios contendo tetraidrofurano, nestas condições estudadas. Verificou-se ainda que tanto a percentagem de solvente orgânico quanto a força iônica do meio têm forte influência na formação dos complexos sucessivos investigados, sendo que os complexos de maior estabilidade foram obtidos em soluções contendo 40 % (v/v) de tetraidrofurano e força iônica de 1,00 mol L-1. Diante dos resultados obtidos, observa-se que o método competitivo adotado neste trabalho, usualmente empregado em estudos realizados em meio totalmente aquoso, também se mostrou apropriado para a determinação das constantes de formação nas condições experimentais investigadas (meios áqüeos-orgânicos). / In this work, the system the iron-III/azide in aqueous-organic media was studied in order to evaluate the formation of complexes under different conditions: ionic strengths in the range of 1.00 to 3.00 mol L-1 and effect of the presence of organic solvents (tetrahydrofuran, acetone and p-dioxan) at T = 20 °C. Besides, in medium containing tetrahydrofuran, the conditional formation constants (b) were determined under different proportions of this solvent (20-40 %, v/v). The method used in the determination of these constants is based on the competition between the metal and the hydrogen ion for the azide, in the buffered system formed between the ligand and the azotidric acid (N3-/HN3). The parameters for the determination of the formation constant of each complexe were obtained by potentiometric measurements, through changes on the solution pH, caused by complexation due the iron ions added into the cell. These parameters were initially analysed by using the Leden method and, subsequently, refined by computational simulation in order to characterize the different complexes in the Fe (III)/N3- system, as well as to determine the value for the global constant of formation for each coexistent species. The results showed the possible coexistence of following four stable complexes: [Fe(N3)]2+, [Fe(N3)2]+, [Fe(N3)3] e [Fe(N3)4]- in aqueous medium containing acetone or p-dioxan. However, in the presence of tetrahydrofuran, the [Fe(N3)4]- was not evidenced. This indicates that a larger competition between the molecules of this organic solvent and the azide ligand, into the coordination sphere of the metallic ion occurs under these experimental conditions. Besides, the organic solvent proportion and the experimental medium are important parameters affecting the formation of these complexes. It was observed that iron complexes with higher stability were produced in the presence of 40 % (v/v) tetrahydrofuran and 1.00 mol L-1 ionic strength. Before the obtained results, it is observed that the competitive method adopted in this work, usually employed in studies accomplished in totally aqueous medium, it was also shown appropriate for the determination of the formation constants in the experimental conditions (aqueous-organic media) investigated.
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Síntese de Seleno-Isoxazóis e Seleno-Indóis via Reações de Ciclização Intramolecular mediadas por Cloreto Férrico / Synthesis of Seleno-Isoxazoles and Seleno-Indoles via Iron(III) Chloride-Mediated Intramolecular Cyclization ReactionsSperança, Adriane 05 March 2013 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work reports the synthesis of a series of 4-organoselenyl-isoxazoles (19 examples), prepared via FeCl3/diorganyl diselenides-promoted intramolecular cyclization of alkynone O-metyloximas. In general, the selenyl-isoxazoles were obtained, in 50 to 70% yield. In addition, an alternative method was developed to promote the intramolecular cyclization reaction of o-alkynyl-N,N-dimethyl-anilines, where FeCl3 and substituted diorganyl diselenides were employed as promoter agents to this process. Through this cyclization protocol a series of N-methyl-3-organoselenyl-indoles could be synthesized (20 examples), in yields varying from 36 to 81%, by using room temperature and ambient atmosphere. In order to evaluate the versatility of the obtained compounds as precursors to the synthesis of functionalized isoxazoles and indoles, the 3,5-diphenyl-4-(phenylselenyl)-isoxazole, N-methyl-2-phenyl-3-(phenylselenyl)-1H-indole and N,5-dimethyl-2-phenyl-3-(phenylselenyl)-1H-indole were submitted to PhSe-Lithium exchange reactions, and the corresponding organolithium intermediates, which were generated by treatment with nBuLi, could be trapped with different electrophiles, affording the functionalized isoxazoles (5 examples) and indoles (4 examples) in good yields (45-80%). / Este trabalho relata a síntese de uma série de 4-organoseleno-isoxazóis (19 exemplos), preparados a partir da reação de ciclização intramolecular de O-metiloximas alquinílicas promovidas por FeCl3 e diferentes disselenetos de diorganoíla. Em geral, os derivados de seleno-isoxazóis foram obtidos de maneira satisfatória, em rendimentos de 50 a 70%. Desenvolveu-se também, um método alternativo para promover a reação de ciclização intramolecular de o-alquinil-N,N-dimetil-anilinas, empregando-se FeCl3 e disselenetos de diorganoíla diferentemente substituídos, como agentes promotores da ciclização. Através deste protocolo de ciclização pode-se sintetizar uma série de N-metil-3-organosseleno-indóis (20 exemplos), em rendimentos que variaram de 36 a 81%, utilizando condições de reação brandas, uma vez que os experimentos foram realizados a temperatura e atmosfera ambiente. A fim de avaliar a versatilidade dos compostos obtidos, como precursores para a síntese de isoxazóis e indóis com diferentes funcionalizações, o 3,5-difenil-4-(fenilselenil)-isoxazol e o N-metil-2-fenil-3-(fenilselenil)-1H-indol e N,5-dimetil-2-fenil-3-(fenilselenil)-1H-indol, foram submetidos à reações de troca PhSe-lítio, e o intermediário litiado correspondente, formado a partir de uma reação utilizando n-BuLi, pôde ser capturado com diferentes eletrófilos, obtendo-se como produtos uma série de isoxazóis (5 exemplos) e indóis (4 exemplos) diferentemente funcionalizados em bons rendimentos (45-80%).
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Study on Methods of Simultaneous Multi-Component Analysis.Ashie, Jennifer Bernice 13 December 2008 (has links) (PDF)
Many new instrumentation and different instrumental techniques have been developed to deal with increasing complexity of samples encountered. Many researchers also have coupled these instrumental techniques with chemometric algorithms to assist in the quantitative analysis of multi-component samples in the hope of alleviating the need of tedious separation and cleanup procedures. These newer chemometric procedures tend to be complex and difficult to understand and implement and are successful under different circumstances and conditions. In this study, we start from the very simple beginning and examine the factors that can present difficulties with obtaining the correct results and observe how the system behaves so as to find a better and simpler chemometric procedure to perform mixture quantitative analysis. We have used simulated and actual experimental data obtained from a UV-VIS spectrophotometric measurement of metal complexes to conduct the study. Well understood and defined systems tend to give good results. The main obstacle has been, and still is, interferences in spectral information one gets from the measurement.
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SÍNTESE DE PIGMENTOS A BASE DE SnO2 DOPADO COM Fe2O3Schmidt, Samara 29 March 2012 (has links)
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Previous issue date: 2012-03-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work a Fe(III)-doped tin oxide (SnO2) system using chemical mixture of SnO2 and Iron(III) nitrate nonahydrate (Fe(NO3)3. 9H2O). This system was calcined at temperatures from 600 ºC to 1200 C. The as-calcined powders were characterized using several techniques: thermal analysis (DTA/TG) to identify the thermal stability;X-ray diffraction to identify the resulting phases; scanning electron microscopy and photocorrelation spectroscopy to study the material morphological structure. The usefulness of the ceramic pigment was evaluated testing the solubility of the oxide
system in frit and its color stability. Also, using UV-visible diffuse reflectance spectroscopy, the CiELab* coordinates of the system were estimated. / Neste trabalho foi desenvolvido um sistema óxido de estanho (SnO2) dopado com óxido de ferro III (Fe2O3) através de mistura química de SnO2 e nitrato ferro III nonahidratado (Fe(NO3)3. 9H2O). Este sistema foi calcinado em intervalos de
temperaturas que variaram de 600 a 1200 C. A caracterização do pó calcinado foi realizada a partir de várias técnicas, entre elas, a análise termogravimétrica e termodiferencial para identificação da estabilidade térmica, a técnica de difração de
raios X para a identificação das fases resultantes, a técnica de microscopia eletrônica de varredura e espectroscopia de fotocorrelação para a compreenção da estrutura morfológica do material. Avaliou-se a eficácia do pigmento cerâmico
através da solubilidade do sistema óxido com a frita bem como a estabildade da cor. Também, através da técnica de espectofotometria na região do UV-Vis, obteve-se as
cores do sistema caracterizados nas coordenadas CIELab*.
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Αντιδράσεις του βρωμιδίου του σιδήρου (ΙΙΙ) με το βενζοτριαζόλιοΜεσσάρη, Δανάη 24 October 2012 (has links)
Υπάρχει ένα συνεχές επιστημονικό ενδιαφέρον για τη σύνθεση και το χαρακτηρισμό συμπλόκων των στοιχείων μετάπτωσης (μεταβατικών μετάλλων) του Περιοδικού Πίνακα. Έχουν λάβει χώρα ενδιαφέρουσες μελέτες πάνω στη χημεία ένταξης διαφόρων μετάλλων με υποκαταστάτες βενζοτριαζόλια. Το ενδιαφέρον αυτό οφείλεται κυρίως στην αντιδιαβρωτική δραστικότητα του βενζοτριαζολίου (btaH) έναντι ορισμένων μετάλλων, κυρίως του Cu και των κραμάτων του. Οι μοριακοί μηχανισμοί της παρεμπόδισης της διάβρωσης των μετάλλων από τα βενζοτριαζόλια δεν έχουν διερευνηθεί πλήρως.
Στην παρούσα Διπλωματική Εργασία αναπτύσσεται ένα μοντέλο παρεμπόδισης της διάβρωσης του Fe από το btaH, και σχηματισμού συμπλόκων του σιδήρου με ουδέτερα βενζοτριαζόλια (btaH), καθώς και με αποπρωτονιωμένα βενζοτριαζόλια (bta-) με τη χρησιμοποίηση ιδεών της Χημείας Ένταξης.
Παρασκευάσθηκε το σύμπλοκο [FeBr3(btaH)2] (1) καθώς και το σύμπλοκο
[Fe14O8(OH)(OMe)9Br9(bta)7(MeOH)2(H2O)2] (2), τα οποία χαρακτηρίσθηκαν με μικροαναλύσεις και φασματοσκοπία IR. Οι μοριακές και κρυσταλλικές δομές των ενώσεων προσδιορίστηκαν με κρυσταλλογραφία ακτίνων-Χ επί μονοκρυστάλλων. Το σύμπλοκο 1 είναι μονοπυρηνικό με πέντε μονοδοντικούς υποκαταστάτες [τρεις αλόγονο (βρώμο) και δύο Ν-δότες]. Το ιόν του FeIII βρίσκεται σε ένα τριγωνικό διπυραμιδικό περιβάλλον ένταξης με τους τρεις βρώμο υποκαταστάτες να ορίζουν το ισημερινό επίπεδο.
Το πολυπυρηνικό μόριο της ένωσης 2.2MeOH έχει δεκατέσσερα τρισθενή ιόντα σιδήρου τα οποία συγκρατούνται μέσω πέντε μ3-όξο (O2-), τριών μ4-όξο (O2-), ενός μ3-υδρόξο (ΟΗ-), εννέα μ2-μεθόξο (OMe-), πέντε η1:η1:η1:μ3 βενζοτριαζολάτο (bta-) και δύο η1:η1:μ2 βενζοτριαζολάτο (bta-) υποκαταστατών. Τα εννέα ιόντα Br-, τα δύο μόρια Η2Ο καθώς και οι δύο MeOH συμπεριφέρονται ως τερματικοί υποκαταστάτες. Τα κέντρα FeIII υιοθετούν τρεις διαφορετικές γεωμετρίες ένταξης (οκταεδρική, τριγωνική διπυραμιδική και τετραεδρική). Τέλος, τα δεκατέσσερα κέντρα του FeIII ορίζουν μία εξαεπιστεγασμένη εξαγωνική διπυραμίδα. Το σύμπλοκο 2 μπορεί να θεωρηθεί ως μοντέλο παρεμπόδισης της διάβρωσης του Fe σε ουδέτερα pH. / There is a continuing scientific interest in the synthesis and characterization of metal complexes of the d block elements of the Periodic Table. Interesting studies have taken place to investigate the ability of various metals to create complexes with benzotriazole as a ligand. This is primarily due to the anticorrosion activity of benzotriazole (btaH) towards certain metals, particularly Cu and its alloys. The molecular mechanisms of the corrosion inhibition of metals by benzotriazoles have not been completely elucidated.
An inorganic chemistry model approach to the corrosion inhibition of the Fe by btaH and to the formation of iron complexes with neutral benzotriazole (btaH) and with deprotonated benzotriazole (bta-), using the Coordination Chemistry approach, has been developed in the present Diploma Thesis.
We have prepared complexes [FeBr3(btaH)2] (1) and [Fe14O8(OH)(OMe)9Br9(bta)7(MeOH)2(H2O)2] (2), which have been characterized using microanalyses and IR spectroscopy. The molecular and crystal structures of the compounds were determined by X-ray crystallography. Complex 1 is mononuclear with five monodentate ligands [three halogenido (bromido) and two N-donors]. The FeIII ion is in a trigonal bipyramidal coordination environment with the three halogenido ligands defining the equatorial plane.
The cluster molecule of 2.2MeOH has fourteen FeIII ions which are held together by five μ3-O2-, three μ3- O2-, one μ3-OH-, nine μ2-OMe-, five η1:η1:η1:μ3 bta- and two η1:η1:μ2 bta- ligands. Nine Br- ions, two molecules of H2O and two molecules of MeOH are terminal ligands. The FeIII centres adopt three different coordination geometries (octahedral, trigonal bipyramidal and tetrahedral). Finally, the fourteen FeIII centres define a hexacapped hexagonal bipyramid. Cluster 2 may be considered as model for the corrosion inhibition of Fe by benzotriazoles at neutral pHs.
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