Dissertations / Theses on the topic 'Platinum group'
To see the other types of publications on this topic, follow the link: Platinum group.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Platinum group.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Tooze, R. P. "Organometallic compounds of platinum group metals." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37880.
Full text
2
Isbilir, Amina. "Tridentate ligands with platinum group metals." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42777.
Full textAbstract:
In this thesis, a series of symmetrical and unsymmetrical pincer ligands are synthesised and explored as supports for platinum group metals, such as palladium, platinum and ruthenium. In Chapters 2 and 3, the synthesis and characterisation of novel pyridine-based dianionic aryl-containing [C,NPy,O] and phenol-containing [O,NPy,O] pincer pro-ligands and their reactivity towards palladium(II) and ruthenium(II) metal precursors is described. [C,NPy,O]-type pincer pro-ligands have been shown to promote sp2 C-H activations upon reaction with palladium(II) and ruthenium(II) metal salts. Phenol-containing [O,NPy,O] pincer pro-ligands demonstrated deprotonation of the phenolic oxygen, resulting in a tridentate coordination upon binding to palladium(II) and ruthenium(III) metal centres. In Chapter 4, six novel paramagnetic ruthenium(III) pincer complexes developed from aryl-containing [C,NPy,O] and phenol-containing [O,NPy,O] pincer pro-ligands, have been employed as efficient catalysts for the transfer hydrogenation of ketones. Chapter 5 describes the synthesis of mono(imino)pyridyl [N,NPy,O] pincer pro-ligands incorporating an ethyl ester group at 6-position and their ability to undergo hydrolysis to a carboxylic acid upon coordination to palladium. Use of platinum(II) metal precursor, on the contrary, did not promote hydrolysis resulting in a bidentate coordination mode in the corresponding complexes. Chapter 6 explores the reactivity of two dien [N,N,N] pincer pro-ligands towards palladium(II) salts. Preliminary investigations demonstrated the ability of the amine-NH donor moieties to promote NH···A (acceptor) hydrogen bond interactions with the acceptor atoms on their corresponding anions in the solid state.
3
Roberts, Yvonne V. "Macrocyclic complexes of platinum group metals." Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/11897.
Full textAbstract:
A series of half-sandwich complexes, [M([9]aneS3)*XY]n+ have been synthesised from MCl2 [M = Pd, Pt,X = Y = Cl-(n = 0), PPh30.5dppm, 0.5dppe,0.5x2, 2'-bipy(n = 2), X = Cl-, Y = PPh3(n&61 1); M = Pd, X = Y = 0.5oxytriphos, 0.5x1, 10-phen(n = 2), X = Cl-, Y = PCy3(n = 1)]. All but one of the crystal structures [M = Pd, X = Y = Cl-, PPh3, 0.5dppm, 0.5oxytriphos, 0.5x2,2'-bipy, 0.5x1,10-phen, X = Cl-, Y&61 PPh3; M = Pt, X = Y&61 PPh3, 0.5dppm] solved show the metal in a square-planar, S2XY co-ordination set, with a long-range apical interaction to the remaining S-atom of [9]aneS3; [Pt([9]aneS3)(PPh3)2]2+ is trigonal bipyramidal. The reductive electrochemistry of the Pd complexes shows the stabilisation of Pd(I) species by bidentate, π-acceptor X,Y ligands. A series of complexes [Ru([9]aneS_3)XYZ]^+ (X-Cl^-, Y = CO or PCy_3, Z&61 H or MeCN; X = H, Y = Z = 0.5x1,5-COD) and [Ru([n]aneS_4)*XY]^m+ (X = Cl^-, Y = PPh_3, n = 12,14,16, m&61 1; X = McCN, Y = PPh_3, n = 12,14, m&61 2; X = Y = McCN, n = 16, m = 2) have also been prepared. The crystral structures of [Ru([9]aneS_3)XYZ]^+ (X = Cl^-, Y = CO, Z&61 McCN; X = H, Y = Z = 0.5x1,5-COD) show the metal to be octahedrally co-ordinated. Such is also the case for [Ru([n]aneS_4)XY]^m+ (n = 14,16, X = Cl^-, Y&61 PPh_3; n = 16, X = Y = MeCN), with the non-macrocyclic ligands mutually cis. A study by nmr spectroscopy of the mechanism of formation of [Ru([9]aneS_3)Cl(PPh_3)(C_4H_3O)H^+ ]^- from [Ru([9]aneS_3)Cl_2(PPh_3)] and Et_2O/THF was undertaken. The former complex, and the dimeric intermediates [Ru([9]aneS_3)(PPh_3)Cl]_2^2+ and [Ru([9]aneS_3(PPh_3)(μ2-Cl)Tl(μ3-Cl)]_2^2+ were characterised by X-ray crystallography. Finally, the novel agostic species [Pd(H[9]aneN_3)Cl_2]_2(PF_6)_2.2([Pd(H[9]aneN_3)Cl_2]_2) is described. The X-ray structure of the dimer shows an unsupported Pd-Pd bond with mutally cis-Cl^- ligands. Only one of the two metal ions in the dimer forms an agostic M-H-N bond. The metal in each of the monomers also forms on M-H-N agostic bond. *[9]aneS_3 = 1,4,7-trithiacyclononane, [14]aneS_4 = 1,4,8,11-tetrathiacyclotetradecane [12]aneS_4 = 1,4,7,10-tetrathiacyclododecane, [16]aneS_4 = 1,5,9,13-tetrathiacyclohexadecane.
4
Xiao, Zhixian 1970. "Characterizing the gravity recoverable platinum group minerals." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115859.
Full textAbstract:
Modeling gravity recovery of platinum group minerals (PGMs) in the grinding circuit is based on three components: Ore characterization of gravity recoverable platinum group minerals (GRPGM), their behavior in grinding mills and hydrocyclones, and the performance of the gravity recovery units. This thesis focuses on the first two components.A laboratory methodology to characterize gravity-recoverable platinum group minerals (GRPGMs) in an ore with four incremental liberation and recovery stages was developed. It was applied to quantify GRPGM content of four ore samples from Canada. To measure the behavior of GRPGMs in the grinding circuit, a methodology to characterize the already liberated (or available) GRPGMs in the circuit streams was developed. The availability of GRPGM in streams, such as ball mill discharge, was used to model the behavior of the GRPGMs in the ball mills and hydrocyclones. Combining with the potential GRPGM in an ore, they can be used for design and/or optimization of platinum group mineral recovery circuit.
The GRPGM content measured by this methodology varied from 5 to 81% depending on the ore. The GRPGM size distribution varied from fine (most GRPGM below 37mum) to coarse (significant content above 212 mum). The stage size-by-size recovery and the total GRPGM content indicate that the methodology can quantify the GRPGM content of ores.
Based on the measurement of the availability of GRPGM in process streams, the behavior of PGMs in ball mills and hydrocyclones is characterized in terms of the less common cumulative selection functions and conventional classification efficiency curves. Mineralogical analysis indicates that sperrylite (PtAs 2) is the dominant platinum mineral at the Clarabelle mill. Its classification efficiency is similar to that of gold, despite its lower density, while grinding rate is significantly higher than gold. The cumulative selection function of platinum and palladium is 1.3 times higher than the ore for size classes above 212 mum and 50 to 70% of the ore below 212 mum.
As a result, sperrylite accumulates in finer sizes than native gold in the grinding circuit. The cumulative selection function of the platinum group minerals was calculated for the Clarabelle grinding circuit based on the survey data and the GRPGM contents in the ball mill discharge, cyclone underflow, and overflow.
The methodology of characterizing the content of GRPGMs in an ore also offers a way to concentrate the minerals for mineralogical study. The use of secondary electron microscopy (SEM), variable pressure SEM and QEM*SEM for qualitative analysis of platinum group mineral mineralogy is presented and discussed. Most of the GRPGMs recovered are well liberated. Qualitative mineralogical analysis of the GRPGM and its associations in ore samples are also discussed.
5
Fotheringham, John David. "Heterobimetallic complexes of the platinum group metals." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/10906.
Full text
6
Tadie, Margreth. "An electrochemical investigation of platinum group minerals." Doctoral thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15748.
Full textAbstract:
The Bushveld complex is the largest ore body in the world hosting platinum group elements (PGEs). It is a stratified orebody with three major reefs namely, the Merensky reef, UG2 reef and the Platreef. Platinum and palladium are the most abundant PGEs found in the Bushveld complex. They occur in the form of minerals/mineral phases with elements such as sulphur, tellurium, arsenic and iron. These minerals/mineral phases are associated with base metal sulphides occuring along grain boundaries. Unlike the Merensky and UG2 reef, the Platreef is almost barren of PGE sulphides and the distribution of base metals sulphides and their association with PGMs is erratic. Froth flotation targeted at the recovery of base metal sulphides is implemented in PGM concentrators to concentrate PGMs. Flotation of sulphide minerals is achieved with the use of thiol collectors to create hydrophobicity, and copper sulphate is often used to improve hydrophobicity and therefore recovery. Sodium ethyl xanthate (SEX) and sodium diethyl dithiophosphate (DTP) are commonly used as collectors on PGM concentrators. The erratic mineral variations in the Platreef ore, however, raise the question of the effectiveness of the application of sulphide mineral flotation techniques on this ore. Previous work by Shackleton, (2007) investigated the flotation of PGE tellurides, sulphides and arsenides. The study highlighted that the mechanisms with which these minerals interact with collectors and with copper sulphate was poorly understood. It is as a result of the findings of Shackleton's work that this study aims to elucidate the fundamental interactions of telluride and sulphide PGMs with thiol collectors and with copper sulphate. Subsequently this work also aims to compare the behaviour of these reagents on sulphide PGMs and telluride PGMs.
7
Sekota, Mantoa Makoena C. "Catalytic reactions of platinum group metal phthalocyanines." Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1006151.
Full textAbstract:
The voltammetric behaviour of I-cysteine and other organic compounds such as hydrazine, hydroxylamine and methionine has been studied on GCE modified with phthalocyanine complexes of osmium, rhodium and ruthenium. For cysteine oxidation, the catalytic activity of the electrode was dependent the nature of the axial ligand. When cyanide and dimethylsulphoxide (DMSO) were used as axial ligands, giving (DMSO)(Cl)Rh(III)Pc, [(CN)₂Rh(III)Pc], (DMSO)₂0S(II)Pc and [(DMSO)₂Ru(II)Pc].2DMSO complexes, the peak current increased with repetitive scanning, indicating the increase in catalytic activity of the electrode after each scan. This behaviour was not observed when pyridine was used as axial ligand. The improvement of the catalytic activity of the GCE after the first scan has been attributed to the formation of the dimeric π-cation radical species at the electrode surface. Water soluble phthalocyanine complex ([(CN)₂Os(II)Pc]²⁻) and the tetramethyltetra-pyridinoporphyrazine complexes of Pd(II) and Pt(II), ([Pd(II)2,3Tmtppa(-2)]⁴⁺, [Pd(II)3,4Tmtppa(-2)]⁴⁺, [Pt(II)2,3Tmtppa(-2)]⁴⁺ and [Pt(II)3,4Tmtppa(-2)⁴⁺) have been prepared. [(CN)₂Os(II)Pc]²⁻ is soluble in water at pH greater 4 without the formation of dimers. The [M(II)Tmtppa(-2)]⁴⁺ (M = Pd or Pt) show high solubility in water and are stable only in acidic pHs. The cyclic voltammetry of the MPc and [M(II)Tmtppa(-2)]⁴⁺ complexes prepared, is also reported. The interactions of amino acids I-histidine and I-cysteine with the [M(II)Tmtppa(-2)]⁴⁺ complexes of Pd(II) and Pt(ll) were studied. All the [M(Il)Tmtppa(-2)]⁴⁺ are readily reduced to the monoanion species [M(Il)Tmtppa(-3)]³⁻ in the presence of histidine and cysteine. The rate constants for the interaction of [M(Il)Tmtppa(-2)]⁴⁺ complexes ofPt(II) and Pd(II), with histidine and cysteine range from approximately 2 x 10⁻³ to 0.26 dm³ mol⁻¹ s⁻¹. Kinetics of the interaction of [Co(Il)TSPc]⁴⁻ with amino acids, histidine and cysteine in pH 7.2 buffer were studied. The rate constants were found to be first order in both [Co(II)TSPc]⁴⁻ and the amino acid. The formation of [Co(III)TSPc]³⁻ in the presence of histidine occurred with the rate constant of 0.16 dm³ mol⁻¹ s⁻¹, whereas the formation of the [Co(I)TSPc]⁵⁻ species in the presence of cysteine gave the rate constant of 2.2 dm³ mo⁻¹ s¹. The relative quantum yield (QΔ) for singlet oxygen production by [(CN)₂Os(Il)Pc]²⁻, and [(CN)⁴Ru(II)Pc]²⁻ in DMF using diphenylisobenzofuran (DPBF) and a chemical quencher were determined. The quantum yield values were obtained as 0.39 ± 0.05 , and 0.76 ± 0.02 for [(CN₂Os(II)Pc]²⁻ and [(CN)₂Ru(II)Pc]²⁻ respectively. The differences in quantum yield values have been explained in terms of donor abilities of both the central metal and the axial ligands.
8
Smale, Simon. "Study of the hydrogen evolution reaction on platinum and platinum group metal surfaces." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54760/.
Full textAbstract:
The hydrogen evolution reaction (HER) has been examined on a variety of Pt and Pt-group metal surfaces to investigate the rate of the reaction. Pt stepped single crystal surfaces were investigated in relation to the HER using cyclic voltammetry, linear sweep voltammetry and multi-frequency AC voltammetry. It was found that the hydrogen evolution reaction activity did not show a dependence on the structure of single crystal platinum electrode surfaces. Thick films of Au, Rh and Pd were deposited onto Pt {111} and successfully annealed to give pseudomorphic surfaces of the bulk metal. The aim of such measurements was to investigate whether strains within the crystal lattice of these films would result in enhanced HER activity. None of the surfaces investigated showed significant HER enhancement. Rather, results similar to those observed using the bulk metals were obtained. Rough Ir and Pt deposits on Pt{111} were also investigated. Enhanced HER activity was observed on these surfaces. This enhancement was interpreted in terms of the structural arrangement of the Ir and Pt deposits. For Pd films on Pt {111} (0 < fVPd < 2 monolayers) it was observed that Pt dominated the HER kinetics for Pd coverages up to one monolayer and was still influential on the HER at two monolayers of Pd. Similarly Pd-Pt surface alloys also showed that Pd had little or no influence on the HER kinetics even with 75 % Pd in the surface layer. Possible mechanisms for this behaviour have been proposed, in particular, the role of subsurface hydrogen in HER on Pt is discussed.
9
Harding, Nigel Anthony. "β-thia-alkyl complexes of platinum group metals." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283721.
Full text
10
Scanlan, Thomas Huw. "Platinum group chemistry of iminophosphines and related ligands." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391972.
Full text
11
Bell, Michael Niall. "Organometallic platinum group metal complexes incorporating macrocyclic ligands." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/13895.
Full text
12
Trenholme, W. J. F. "Metal-organic frameworks for platinum group metal extraction." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32795/.
Full textAbstract:
This Thesis describes the synthesis and characterisation of a variety of functionalised metal-organic frameworks (MOFs). These MOFs have been used for the extraction of platinum group metal (PGM) compounds from aqueous and organic solvents and for the storage of gases such as CO2, CH4 and the C2 hydrocarbons. Chapter 1 contains an introduction to PGM properties and uses with specific focus on the chemical properties which allow for separation of PGMs from base metal compounds and for separation between different PGM compounds. The synthesis and structure prediction of MOFs is then introduced, leading into an overview of the use of functionalised MOFs, especially those used for the encapsulation and extraction of metal ions from solution. General experimental techniques and details are described, as is the theory behind inductively coupled plasma optical emission spectrometry (ICP-OES), the most widely used analytical technique reported in this work. Chapter 2 describes the synthesis of chemically stable amine-functionalised Zr(IV) MOFs; UiO-68-NH2 and UiO-66-NH2, for extraction of PGM anions from aqueous and acidic solutions. ICP-OES was used to show that both materials exhibit close to 100% uptake of PtCl62- when present in just 3.5 equivalents per anion, comparable to the best materials reported for PtCl62- extraction. Furthermore, UiO-66-NH2 exhibited consistently higher PtCl62- uptake from aqueous solutions than four industrially used materials supplied by Johnson Matthey. Back-extraction of PtCl62- was demonstrated simply by heating the doped MOF in 4 M HCl, removing 99% of the PGM while maintaining the phase and crystallinity of UiO-66-NH2. Separation of PdCl62- from PtCl62- from acidic HCl solutions was exhibited by UiO-66-NH2, showing an exceptional selectivity of 20:1 for Pd:Pt from 2 M HCl. Likewise, 100% selectivity for PtCl62- and PdCl62- over CuCl2 and CuSO4 from acidic solutions was demonstrated, even in cases in which Cu was in 100-fold excess. Solid state NMR was employed to confirm the interaction between the framework and the PGM anions, with XPS results suggesting that the encapsulated Pt species within UiO-66-NH2 may be PtCl3(NH2)3 or PtCl4(NH2)2. Chapter 3 describes the synthesis and characterisation of a series of functionalised Cu(II) MOFs, NOTT-151, -155, -125 and -150, for the removal of neutral PGM complexes, Pd(OAc)2, PtCl4 and Rh2(OAc)4, from THF. The design of the MOFs allowed for an investigation into the effect of different topologies (ssa and fof), cage sizes and functional groups (amine, oxamide and methyl) on the uptake of each PGM complex. ICP-OES analysis showed that the MOFs were capable of extracting each PGM complex. The oxamide-functionalised NOTT-125 exhibited the most consistent uptake of Pd(OAc)2 with a maximum capacity of 35 mg g-1 (7 NH(CO)2NH groups per PtCl4). The amine-functionalised NOTT-155 showed the highest uptake of PtCl4, with a maximum capacity of 73 mg g-1 (4 NH2 groups per PtCl4). Uptake of Rh2(OAc)4 was generally low, however NOTT-125 showed a maximum extraction of 87 mg g-1 (3 NH(CO)2NH groups per PGM). The larger pore fof MOFs, NOTT-155 and NOTT-125, were more effective for each extraction than the MOFs of ssa topology, NOTT-151 and NOTT-150. However, of the ssa MOFs, amine-functionalised NOTT-151 was shown to give higher uptake of each PGM than the isostructural methyl-functionalised NOTT-150. This demonstrated the importance of incorporating a functional group capable of coordinating to the metal complex. Chapter 4 introduces the use of a nitrogen-rich triazine core in the synthesis of a variety of organic linkers to prepare MOFs for gas storage applications. The preparation of a novel 3,24-connected Cu(II) MOF of rht topology, denoted NOTT-160, is described and the structure characterised using X-ray crystallography. The material is shown to exhibit good uptake of C2 hydrocarbons with uptake of 128 cc g-1, 115 cc g-1, 110 cc g-1 for C2H2, C2H4, C2H6 respectively at 298 K and 1 bar (this becomes 212 cc g-1, 175 cc g-1 and 201 cc g-1 at 273 K and 1 bar). The selectivities of 79:1 and 70:1 calculated using Henry’s law for the separations of C2H2:CH4 and C2H4:CH4 respectively at 298 K are the third and second highest reported values for a MOF under these conditions. Ideal adsorbed solution theory (IAST) was also employed to calculate and predict these selectivities and shows agreement with the results obtained using Henry’s law. In addition, NOTT-160 shows an exceptional volumetric working capacity for CH4 of 221 cm3 cm-3 at 80 bar and 298 K. This is the second highest working capacity reported for a MOF under these conditions, with the excellent performance attributed to the high porosity and comparatively high crystal density of the material. Chapter 5 contains a summary of the work presented in this thesis.
13
Auer, Derek. "Flow-injection analysis of the platinum-group metals." Doctoral thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/17511.
Full textAbstract:
Includes bibliographical references.To date the principle methods for the determination of the platinum-group metals (PGMs) use an "off-line" assay with flame-atomic absorption spectrometry and visible spectrometry. Both suffer numerous interferences and involve time-consuming and arduous laboratory separation methods prior to analysis. An "on-line" method for the rapid assay of the PGMs is indeed a lacking component in the analysts' repertoire of methods. This study describes the development of spectrophotometric methods for the determination of the PGMs using flow-injection analysis (FIA). The principle of exploiting the remarkably specific and selective reaction of stannous halides with the PGMs to yield a series of intensely coloured complexes in acidic solutions forms the basis of these methods. The reaction is subject to relatively few interferences from other transition metals. A high speed scanning spectrophotometer is employed to obtain second order data. The successful manipulation of the data enables the determination of PGMs as single components and also simultaneously in mixtures. Attention is focused on the establishment of principles for successful multi-component analysis of PGMs. The development of a software program for multi-wavelength data manipulation was mandatory and is described. Criteria for successful selection of analytical wavelengths are discussed. The usefulness of multi-dimensional graphical data representation is demonstrated in a stop-flow study of the palladium reaction with tin (II) chloride. Qualitative information is provided regarding the nature of complexes and their interactions. Correlation of spectrophotometric data with complex solution colour changes is made. The requirements for future progress in multi-component FIA determinations as well as the direction for future research conclude the study.
14
Bradley, Ena. "Electrochemistry of platinum group metals in ionic liquids." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705896.
Full text
15
Garrioch, Rhona Margaret. "Isomerisations of group 10 metallacarboranes." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/582.
Full text
16
Van, Dyk Jacobus Barend. "A detailed kinetic and mechanistic investigation of the multi-step oxidation of [PtIICl4]2- by [IrIVCl6]2- in acidic medium." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/95481.
Full text
17
Li, Tong. "Atomic scale characterisation of platinum group alloy catalyst materials." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669976.
Full text
18
Harlow, Karsten James. "Imidazolidene and alkylidene complexes of the platinum group metals." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313729.
Full text
19
Rioche, Cyrille Christophe. "An investigation of platinum group metals for environmental catalysis." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492038.
Full textAbstract:
Environmental concerns and more stringent regulations have stimulated the development of new cleaner technologies to decrease the emissions of greenhouse gases and other hazardous gas emissions. In this study, the steam reforming of biooil as well as NOx storage and reduction catalysts were investigated. The production of hydrogen by steam reforming of bio-oils obtained from the fast pyrolysis of biomass requires the development of efficient catalysts able to cope with the complex chemical nature of the reactant. Steam reforming of a few model compounds and that of an actual bio-oil was investigated in the temperature range 650-900°C over Pt, Pd and Rh supported on alumina and a ceria-zirconia sample. The use of ceria-zirconia led to higher H2 yields. The supported Rh and Pt catalysts were the most active, while palladium-based catalysts performed poorly. Temperatures close to, or higher than, 800°C were required to achieve significant conversions to COx and H2 (e.g., H2 yields around 70%) ofthe bio-oil. NOx Storage and Reduction (NSR) catalysts are considered to be one of the most promising solutions to meet the upcoming NOx exhaust emission regulations. However, despite the high level of activity in this area, it is surprising that most studies have been conducted under conditions that are far from realistic. A fast transient apparatus has been developed to study these catalysts under realistic temporal conditions. The performance of a typical Pt/Ba/y-Ah03 NSR catalyst was studied as a function ofthe temperature, rich phase duration, reductant concentration, the type of reductant and the space velocity and the importance of the regeneration step in the NSR process was highlighted. The regeneration step was further investigated over Pt and/or Rh based catalysts by coupling of fast transient kinetic switching and the use of 15NO. An unexpected double peak in the evolution of nitrogen was revealed. The first peak occurred immediately on switching from lean to rich conditions, while the second peak started at the point at which the gases switched from rich to lean. Rh/Ba/Ah03 trap was found to be dependent on the rate of NOx storage, since the rate of regeneration was sufficient to remove the NOx stored in the lean phase. pt/Ba/Al203 was found to be limited by the rate of regeneration.
20
Carmichael, J. "Hydrogenation of deactivated carbonyls over platinum group metal catalysts." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426964.
Full text
21
Heaton, Stephen Nicholas. "Vinylsilane and silyl hydride complexes of platinum group metals." Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295650.
Full text
22
Totland, Marina. "Determination of the platinum group metals in geological materials." Thesis, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390298.
Full text
23
Wells, Peter Philip. "Controlled surface modification of supported platinum group metal catalysts." Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438652.
Full text
24
Savage, Paul David. "Organometallic compounds of rhenium and the platinum group metals." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46494.
Full text
25
Stanger, Gillian. "Preparation and characterisation of the platinum group metal fluorides." Thesis, University of Leicester, 1988. http://hdl.handle.net/2381/33924.
Full textAbstract:
An extensive reveiw of the platinum group metal fluorides has been carried out and in the light of this, new preparative routes have been developed and characterisation has been significantly improved. The preparation of the platinum group metal fluorides in both static and dynamic systems is discussed in chapter two. The fluorinations of ruthenium, rhodium and platinum sponges in dynamic systems proved to be of greatest interest. In these studies large amounts of ruthenium hexafluoride and platinum hexafluoride were produced and traces of rhodium hexafluoride were noted, where as previously more forcing conditions had been employed in the preparation of these compounds. It is believed that rigorous drying of the flow line and hydrogenation of the metal in situ are responsible for the success of this new preparative route. When ruthenium is fluorinated in the dynamic system ruthenium hexafluoride and tetrameric ruthenium pentafluoride are produced in large quantities, and smaller amounts of a red glassy material is also formed. There have been no previous reports of any red material forming during this reaction. It is now believed that this material is a trimeric form of ruthenium pentafluoride. The charaterisation of these fluorides was carried out using a large variety of techniques, the most useful being mass spectrometry and matrix isolated infrared spectroscopy. Mass spectrometry proved invaluble in the characterisation of the trimeric ruthenium pentafluoride, while matrix isolation enabled good quality infrared spectra of the reactive hexafluorides to be recorded. These techniques were also utilised to give the first insight into the behaviour of the tetrameric pentafluorides in the gas phase. Iridium pentafluoride has been shown to be monomeric at elevated temperatures, under similar conditions ruthenium and osmium pentafluorides decompose to the metal and fluorine. Platinum pentafluoride is known to be unstable at room temperature and thought to decompose to the hexafluoride and tetrafluoride. Using matrix isolation, direct evidence of this has been obtained.
26
Johnson, T. "Platinum group metal modifications of TiO₂ for environmental remediation." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3006082/.
Full text
27
Totland, Marina. "Determination of the platinum group elements in geological materials." Thesis, Kingston University, 1993. http://eprints.kingston.ac.uk/20571/.
Full textAbstract:
The available instrumental methods for platinum group element (PGE: Ru, Rh, Pd, Os, Ir, Pt) and gold (Au) determinations are reviewed. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ICP-mass spectrometry (ICP-MS) enable rapid, multi-elemental analysis, their instrumental and analytical characteristics being discussed here. The suitability of ICP techniques to quantitatively determine the PGEs + Au is demonstrated. The detection limits by ICP-AES range from 6 to 29 ng.mL[sup]-1, while those for ICP-MS range from 0.3 to 0.22 ng.mL[sup]-1, for the individual PGEs + Au. A digestion step is generally required prior to the analysis of geological materials by ICP-AES and/or ICP-MS. Digestion procedures are reviewed, with particular attention to the new method of microwave digestion. A comparative study of three digestion methods was undertaken, a range of well-characterised rock reference materials being used to evaluate open acid digestion, microwave acid digestion and alkali fusion procedures. The precision and accuracy of results obtained by ICP-AES and ICP-MS for 46 elements demonstrates that no single digestion method is universally applicable. It is concluded that the best digestion procedure for PGE-bearing materials is a combination of microwave acid digestion followed by a fusion of the residue. Such a method was developed and its suitability is demonstrated using reference materials containing high levels of the PGEs + Au, which enable their direct determination by solution ICP-MS. Even with the superior sensitivity of ICP-MS, low concentrations of the PGEs + Au in most geological materials preclude the quantitation of unseparated samples. Separation methods which have been used (fire assay, coprecipitation, ion exchange, solvent extraction, distillation) are reviewed. Two ion-exchange methods were developed to separate the PGEs + Au from their associated matrix elements allowing their preconcentration prior to analysis. An anion-exchange method can be used in conjunction with ICP-MS for the separation and determination of ≥1 ng.g[sup]-1 Ir and> 1 [mu]g.g[sup]-1 Ru, Rh, Pd, Pt or Au. A cation-exchange ICP-MS procedure can be used to determine the PGEs at a wider range of concentrations. An evaluation using all the available PGE reference materials showed good agreement with reference values in most instances. Stable isotopes were used to evaluate this method and the results confirm that quantitative results may be obtained. The cation-exchange procedure can be scaled-up to larger samples thus enabling the determination of < 1 ng.mL[sup]-1 of individual PGEs. This is demonstrated using 5 g sub-samples and guidelines are given for further increases in sample size. Slurry nebulisation ICP-MS was developed for the determination of the PGEs + Au in solid samples without a prior digestion stage. An assessment of the method using reference materials demonstrated that quantitative results may be obtained for all seven PGEs + Au at levels above 50 to 200 ng.g[sup]-1 (depending on the element). This method is ideally suited to the routine analysis of mineralised samples or where only small sample sizes are available.
28
Carroll, Sandy. "The viability of the Kaplats Platinum group element deposit." Access, 2006. http://upetd.up.ac.za/thesis/available/etd-07102008-080330/.
Full text
29
Lord, Richard Alastair. "Platinum-group element mineralisation in the Shetland ophiolite complex." Thesis, Open University, 1991. http://oro.open.ac.uk/57329/.
Full textAbstract:
The Shetland ophiolite complex exhibits the lower part of the definitive Penrose sequence, but chromitites from the Cliff locality contain levels of Pt and Pd which are unusual in ophiolites. Aspects of this mineralisation suggest both magmatic and hydrothermal concentration processes, although neither individually explain the observed paragenesis. This study examines the distribution of PGE within a representative fresh vertical section of the ophiolite stratigraphy, to assess the relative roles of such processes in the concentration and fractionation of PGE. In the field area around Balta Sound, tectonised mantle harzburgites are overlain by a layered ultramafic cumulate sequence. Accessory Ni-Cu sulphides occur throughout these cumulates. Two stratigraphically controlled zones of chromite enrichment have been identified which mark the bases of cyclic repetitions. Such chromite enrichments lack progressive changes in mineral chemistry so repetitions within the cumulate sequence are attributed to influxes of primitive magma during open system fractionation. The distribution of PGE and other chalcophiles show primary lithological associations, indicating a magmatic origin. Os-Ir-Ru concentrations occur in cbromitites, whereas Pt-PdRh concentrations occur in sulphide-bearing dunites, chromite-rich dunites, or basal pyroxenites. Stratigraphically controlled zones of PGE-enriched sulphide-bearing cumulate dunites occur close to the base of each cyclic repetition and are continuous over a strikelength of 2 km. The fractionation between PGE and other cha1cophiles is consistent with magmatic processes. The distribution and fractionation of PGE can be explained by an open system model. Negative slope patterns are produced by the precipitation of PGM from PGE saturated magmas during chromite crystallisation. This initial process buffers the PGE concentrations in each primitive magma pulse. On entering the axial chamber and mixing with the evolving resident magma, sulphide saturation occurs and the remaining PGE are partitioned into immiscible sulphide liquids. Multiple inputs result in repeated PGE enriched zones. This model explains why successive stratigraphic PGE-enriched horizons have similar positive slope patterns but progressively fractionated host silicate and sulphide compositions.
30
Du, Toit Zita. "Simulation of a palladium extraction circuit." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019/536.
Full text
31
Wicks, Joseph Leslie Michael. "Routes to mixed metal compounds of the platinum group : metal σ-acetylide complexes and platinum clusters." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620495.
Full text
32
Arnold, Philip M. "Coordination chemistry of platinum group metals with sulphur-containing ligands." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249298.
Full text
33
Jeffery, Edward. "Hydrogenation of ketones over platinum group metals : a DFT study." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54642/.
Full textAbstract:
The enantioselective hydrogenation of a-ketoesters over a platinum surface modified by cinchona alkaloids has been studied using accurate computational modelling. A series of small prototype compounds were used to interact with the metal surface, leading to the study of acetone adsorption on a platinum surface. It was found that the enol and enolate isomers of acetone may play a crucial role in the surface chemistry. The enol form of acetone was significantly more stable than the keto-form, and the enolate form was also more stable. Vibrational frequency analysis suggests that the enolate form may prove to be a better fit to some of the experimental data than the commonly-accepted ketone form. The interaction of an a-ketoester, methyl pyruvate, with a platinum surface was then studied using the same techniques. The enol form was again the most stable surface species compared to the enolate and ketone forms. Additionally, the cis form of methyl pyruvate was generally more stable than the trans form. A full vibrational analysis was performed, allowing comparison with future experimental work. In order to investigate the conversion between the different types of isomer, an eigenvector following scheme is under development to find reaction barriers and transition states. To date, this has been applied to simpler systems with success and is in the process of being extended to more complicated applications. Concurrently, a technique to study the whole enantioselective reaction system was also being developed. This involves a modified simple QM/MM scheme containing a model for the surface, the substrate and modifier. This was successfully applied to a simple system (methyl pyruvate interacting with the surface and modifier) and yielded predicted ees in agreement with experimental observation. This was extended to a more complex system under study at Cardiff University and reproduced the experimental enantioselectivity this was then used to suggest possible improvements to enhance the ee of this system.
34
Martinez, Josep Vicent Colomer i. "Towards separation of platinum group metal anions from feed solutions." Thesis, University of Southampton, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496074.
Full text
35
Lenthall, Joseph T. "Anion and platinum group metal binding of bis(thioureido) ligands." Thesis, Durham University, 2007. http://etheses.dur.ac.uk/2854/.
Full textAbstract:
A series of bis(thioureido) ligands have been synthesised, which show anion binding in acetone-d(_6). Their structures have been determined by X-ray crystallography and some exhibit hydrogen bonding interactions with the π-electrons of the the thiocarbonyl bond. This hydrogen bonding interaction has been investigated for the general thiocarbonyl and carbonyl bond using the CSD, and a marked difference in the interaction of hydrogen bond donors with the π-electrons of carbonyl and thiocarbonyl bonds has been shown. The bis(thioureido) ligands have been coordinated to platinum group metals and the differing binding modes of the ligands investigated. The reaction of ligands with 2 carbon atoms between thiourea groups with [{Ru(n(^6)-С(_6)Н(_4)МеСН(Ме)(_2))С1(μ- Cl)}(_շ)], yields a mixture of products that may be consolidated into a single product with a water wash. The water instigates a deprotonation of an NH group that allows nitrogen coordination to ruthenium, yielding a S,S,N terdentate Ru(II) half-sandwich complex, with four- and seven-membered adjoining metallacycles. A chiral metal centre is formed and in the solid state, opposite enantiomers hydrogen-bond to each other through chloride counter-ions. Ruthenium complexes with an interaction from the pyridyl nitrogen in ligands containing pyridyl binding moieties have also been characterised. Bidentate S,S coordination is observed for the reaction of bisthiourea ligands with [Pd(dppe)Cl(_2)], forming nine- and ten-membered metallacycles. A similar binding mode is observed in a Pt(II) analogue. A polymer analogue of the bisthiourea ligands has been synthesised, and has been tested to extract metals from mixed metal solutions. Using well-defined metal salts in methanol, ruthenium(II) may be loaded onto the polymer from a single metal solution, acetontrile solvent inhibits the uptake of platinum group metals from mixed metal solutions, the polymer is selective for Cu(II) even when acetonitrile solvent is present and in the absence of Cu(II) or acetonitrile, can selectively extract Pt(II) over Ru(II), Fe(II), Cr(III) and Ni(II). The ruthenium loaded resin may be stripped of Ru(II) effectively using concentrated nitric acid solution in two hours. Testing the bisthiourea polymer in an acetic acid mixed metal solution demonstrated that the polymer was not suitable for platinum group metal extraction from the acetic acid medium, when compared to a commercially available resin.
36
Wenger, J. C. "Surface chemistry of the group IIB metal dimethyls on platinum." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334697.
Full text
37
Freestone, Timothy. "Some aspects of the biocompatibility of the platinum group metals." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316572.
Full text
38
McKenzie, S. G. "The effect of platinum group metals on duplex stainless steel." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37782.
Full text
39
Morton-Fernández, Brian. "Synthesis and characterisation of dithiolato complexes with platinum group metals." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3556.
Full textAbstract:
The interest in biosensors can be attributed to the first described enzyme containing sensor used to detect levels of glucose in 1962. Although research into biosensors was initially slow to pick up, the field has become increasingly popular and research has been widespread for the last 20 years. The continuing research into biosensors is crucial as this will improve current devices to become smaller, faster and more economical and yield new biosensors. This thesis is mostly concerned with the development of an integral component of a biosensor, the redox mediator. Complexes of ruthenium incorporating electron rich sulfur-donor ligands such as naphthalenedithiol should possess interesting redox qualities which could be used to produce better mediators. A second area covered in this thesis is in the structural studies of a series of iridium and rhodium complexes. Two classes of ruthenium complexes with sulfur-donor ligands have been prepared. The first class incorporates the ruthenium bis-bipyridine moiety while the second contains pentamethylcyclopentadienyl ruthenium. Most complexes synthesised exhibited reversible oxidation waves in the region of -0.1 to 0.2 V vs. Ag/Ag⁺. Their possible use as redox mediators was hindered by several factors, particularly difficulties in purification. They also exhibited oxygen sensitivity and low stability when in solution.The second area covered in this thesis is to further understand the bonding of the ligands used in the above study. A series of pentamethylcyclopentadienyl iridium and rhodium complexes were synthesised with three different dithiolato ligands. Two of the three ligands studies produced structures that included more than one metal centre leading to straining of the ligand. In order to study the monomeric form, the clusters were opened with a neutral phosphine ligand. Both the Ir…S and Rh…S bond lengths of all the complexes were within expected parameters.
40
Wilson, Andrew Matthew. "Ditopic reagents for the solvent extraction of platinum group metals." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/16864.
Full textAbstract:
This work aims to develop solvent extractants to recover platinum and palladium from highly acidic chloride solutions bearing other platinum group metals (PGMs). In general, metal values can be recovered by solvent extraction through three different mechanisms: metal cation extraction (1); metalate anion extraction (2); or metal salt extraction (3). Mn- + n(LH)(org) ⇌ [M(L)n](org) + nH+ (1) MClx n- + nL(org) + nH+ ⇌ [MClx(LH)n](org) (2) MClx + nL(org) ⇌ [MClxLn](org) (3) The main objective of this thesis is to establish whether ditopic extractants can be developed which have chemical functionalities that allow both mechanisms (2) and (3) to operate, co-extracting Pt(IV) and Pd(II) as their chloridometalates in an outer sphere binding site (2) and allowing their separation by raising pH to transfer the more kinetically labile Pd(II) to an inner sphere binding site (3) and releasing H2PtCl6 to the aqueous strip solution. A review of the literature is presented in Chapter 1, noting current commercially available extractants and the processes in which they are, or have been, applied. Particular attention is paid to the mode of action of the reported extractants and whether they extract metal cations, anions or metal salts. This chapter also outlines the proposed solvent extraction circuit in which new reagents developed in this thesis would be incorporated and the methods applied during the screening of candidate extractants. Chapter 2 deals exclusively with the use of reagents with inner-sphere binding sites for the selective extraction of palladium over platinum. Work on a series of oxime reagents synthesised for palladium extraction as part of preliminary MSci research (Andrew M. Wilson, MSci Thesis, University of Edinburgh, 2011) is reviewed. Studies of the hydrolytic stability of oximes indicate that they are unsuitable for incorporation into ditopic reagents for use in a circuit with a highly acidic feed solution. Thioethers were studied as alternatives as they show high kinetic selectivity for palladium over platinum and are more stable under acidic conditions. The synthesis and extraction properties of model reagents (largely arylalkyl thioethers) are reported and compared with those of the commercially available di-n-hexylsulfide. Incorporation of a polar group such as an amide provides phase transfer catalysis, accelerating the rate of transport of Pd(II) into the organic phase, but reducing selectivity over Pt(IV). The identification of functionalities that operate as receptors for chloridometalates by forming outer-sphere assemblies is explored in Chapter 3. The synthesis of amine, amide and amino-amide extractants from acid chloride streams and the effects of variations of functional groups on the extraction of PtCl6 2− are described. Secondary amides were found to be stronger extractants than tertiary amides, and aliphatic amides also show better metalate extraction than aromatic amides. The interactions between protonated aminoamide reagents and PtCl6 2− werre analysed by X-ray crystallography, noting that C-H∙∙∙Cl interactions with the “soft” chloridometalate anion are more common than with the “hard” chloride ion which shows a preference for more conventional N-H∙∙∙Cl interactions. Chapter 4 combines the reagent types explored in Chapters 2 and 3, in ditopic extractants that have both inner- and outer sphere binding sites. The synthesis and characterisation of a series of thioether amide reagents are reported and the selective extraction of platinum and palladium over other PGMs are discussed. In-house screenings of aryl- and alkylthioetheramide extractants showed selective co-extraction of Pd(II) and Pt(IV), rejecting Ir(III). Pt(IV) can be selectively water-stripped followed by ammonia-stripping of Pd(II). Industrial screenings at Johnson Matthey Technology Centre further exemplified the selectivity of these extractants over Ru(III) and Rh(III), although third phases were formed when the reagents were used for recovery from highly concentrated metal-feed solutions. The mode of action of the ditopic extractants is discussed, based on DFT calculations, crystal structure determinations and NMR studies, which support the formation of outersphere metalate assemblies and inner-sphere palladium complexes. Chapter 5 describes new difunctional (inner + outer sphere complexation) extraction by a single chemical entity, in this case an unsaturated N-heterocycle (an azole). The synthesis and characterisation of a series of hydrophobic azoles are described. These have basicities which allow protonation when contacted with strongly acidic solutions (2), but can be deprotonated in contact with water to allow their neutral forms to form inner-sphere complexes with Pd(II). Triazole-based reagents show the selective co-extraction of Pt(IV) and Pd(II) and, as with the ditopic thioetheramide reagents reported in Chapter 4, allow the selective water stripping of Pt(IV) and subsequent ammonia stripping of Pd(II).
41
Lopes, Lidia Velazquez. "Sorption of the platinum-group elements in selected solid matrices." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/4210.
Full textAbstract:
Summary in English.Bibliography: leaves 70-75.
Recent research on the platinum-group elements (PGE) has shown increased concentrations in environmental samples, probably as a result of the widespread use of PGE (Pt, Pd and Rh in particular) as catalysts in the chemical and car industry. Most of the recent research on PGE focuses on the analysis of concentrations in environmental samples exposed to anthropogenic sources of PGE, but there are very few studies that have investigated sorption behaviour of PGE in soils.
42
Sperring, Sophie. "Alteration of gold nuggets enriched with Platinum Group Elements (PGEs)." Thesis, Sperring, Sophie (2017) Alteration of gold nuggets enriched with Platinum Group Elements (PGEs). Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/41061/.
Full textAbstract:
Understanding the mechanisms of incorporation, the form, and the solid-state solubility of Platinum Group Elements (PGEs) in gold nuggets at the nanoscale is critical to future works in gold (Au) nanoscale crystallography. Current works looking at similar samples include Mineral company research into extraction methods of similar samples and research in progress at the University of Western Austral using the alloy of the Au samples for medical purposes.
The work completed by this this used Au nugget samples that were taken from Ruby Creek, British Columbia, Canada. The geology specific to the Au samples used is a sub type of the placer alluvial is: Atlin gold placers, which are known for hosting a variety of metals, specific to the Atlin region.
Traditional thought for Au nuggets for monocrystalline structures. This steams from research completed by the minerals industry to extract the gold that lent into mineralogical studies. The gold rich rim consists of spherical particles that do not display the silver rich core parallel lamellae texture. The core structure is truncated where it meets the rim of the particle. No PGE particles within the sample area observed.
As seen with previous studies the Au samples display a rim that is silver (Ag) enriched. The rim could be a leaching mechanism experience by the gold in the presence of aqueous material. The relationship between the Au and the Ag was established as inversely proportional. The PGEs accumulated in the rounded, poly crystalline nanoparticulate Au-rich rim. The rim exhibited greater porosity within this rim area.
Majority of gain boundaries in the silver rich core of gold particles show a pile up of dislocations which result in multiplication of the diffraction maxima. The rim observed on the Au nugget samples were shown to have a PGE accumulation of between 10 to 20 μm.
The presence of the PGEs in solid solution is likely due to their relatively low concentrations and/or association with other trace elements such as Arsenic (As), Selenium (Se) and Sulphur (S), which may help to dissolve PGEs in the gold structure. The distribution seen of the PGEs suggests that during alteration of gold particles under supergene conditions, PGEs are subjected to the enrichment process due to a selective dissolution of Ag. Homogeneous distribution of Ru, Rh and Pd in the gold matrix and lack of PGEs nanoparticles in the pores support this postulation.
The irrefutable evidence obtained from this study is that the PGEs are in solid solution in crystal structure in this sample. Exsolution does not occur at the nanoscale. It can also be said that during the process of alteration, the PGE accumulate in the Ag removed area.
The interest in this project will extend into Nano-SIMS academic activity to have a closer look at the isotopic complexity and to look at the distribution of isotopes of PGEs in gold sample. Looking for exsolution at absolute nanoscales and to see if the isotopes of the PGEs fractionate in the gold formation are also main features of the future work in this area of mineralogy.
43
Penberthy, Catharina Johanna. "The effect of mineralogical variation in the UG2 chromitite on recovery of platinum-group elements." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-11282005-113358/.
Full text
44
Gash, Rosslyn Clare. "Metal haloalkyl in complexes in catalysis." Thesis, University of St Andrews, 1993. http://hdl.handle.net/10023/14706.
Full textAbstract:
In this thesis, the preparation of a number of halomethyl complexes of rhodium, platinum, and palladium is described. Complexes of the type trans-[Rh(CH2X)X(P4)]+ (X = Cl, Br, I, P = PMe3, dmpe) were found to be unstable, decomposing in situ to give a mixtures of dihalo, trihalo, and phosphine ylide species. Platinum and palladium species of the type trans-M(CH2X)X(PEt3)2 (X = Cl, I, M = Pt, Pd), which were formed by the reaction between M(PEt3)3 CH2XY were also unstable. In the case of platinum, phosphine ylide species were isolated from reaction mixtures, whilst the palladium halomethyl species decomposed over a number of days to give dihalide complexes. However, palladium iodomethyl species prepared via reactions involving 2 moles of phosphine per mole of metal were found to be stable. Neutral rhodium halomethyl complexes were also found to be far more stable than their cationic counterparts. The synthesis and characterisation of trans-RhCl(CO)(CH2l)I(P)2/ (P = PMe3, PEt3, or Et2PPh), prepared by oxidative addition of CH2I2 to RhCl(CO)(P)2 is described. When less basic phosphines (such as PPh3) or the sterically hindered phosphine PCy3 were used, no evidence of any reaction between the rhodium complex and the CH2I2 was observed. The molecular structure of trans-RhCl(CO)(CH2l)I(PEt3)2 has been studied by X-ray diffraction analysis. This complex proved to be inert to substitution at the iodomethyl carbon atom by neutral nucleophiles such as H2O, CH3OH, and PEts, but prone to substitution by Cl-. The lability of iodomethyl (and chloromethyl) ligands towards CO insertion has also been studied. There is evidence to suggest that an iodoacyl platinum complex may form in solution after the complex cis-Pt(CH2l)I(PPh3)2 had been left under 1 atm CO for 24 hours. However, in the case of trans-Pd(CH2l)I(PCy3)2 this same reaction took 7 days under 70 atm pressure of CO. All of the rhodium iodomethyl complexes prepared were also inert to CO insertion at ambient temperature and 1 atm CO, but excellent evidence for CO insertion having taken place in irflns-RhCl(CO)(CH2l)I(PEt3)2 was observed at 70°C and 35 atm of CO. Evidence for CO insertion into a rhodium-chloromethyl bond was also observed under the more forcing conditions of 100°C and 70 atm CO. This insertion reaction may prove to be extremely useful in catalytic systems. A report of some preliminary catalytic studies involving the production of diethylmalonate from CH2I2 and C2-products from the hydroformylation of (CH2O)[sub]n under very mild conditions is also presented. It is thought that these catalytic reactions proceed via carbonyl insertion into a rhodium-iodomethyl bond.
45
Machado, Norma Maria Pereira. "Rheological study of nuclear glass melts containing Platinum Group Metal aggregates." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0018.
Full textAbstract:
En France, les produits de fission nucléaire issus du retraitement des combustibles usés sont conditionnés au sein de matrices de verres borosilicatés. Lors du processus de vitrification à haute température (1200 °C), les éléments à confiner réagissent chimiquement avec les additifs de vitrification pour former un verre homogène. Cependant, parmi ces éléments, les platinoïdes ne sont pas solubles dans le bain de verre et restent en suspension sous forme de particules de quelques microns. Ces particules présentent une forte tendance à l'agrégation et les suspensions peuvent alors présenter une viscosité apparente anormalement élevée. Ces systèmes sont caractérisés par un comportement rhéofluidifiant et thixotrope. La présente étude vise à fournir des données importantes sur le comportement rhéologique global de ces systèmes et leurs propriétés, grâce à la caractérisation d'un verre nucléaire simulé contenant 3,0 % massique (1,02 % en volume) de platinoïdes. Une modélisation mathématique du comportement thixotrope de ce verre est présentée pour la première fois en utilisant un modèle similaire à celui proposé par Houska (Houska, 1981). Ce modèle prédictif permet la description des résultats expérimentaux obtenus à partir de mesures en régimes permanent et transitoire. L'impact de la contrainte de cisaillement et du temps sur le degré d'agrégation et la cinétique de sédimentation des particules est déterminé à l'aide d'un rhéomètre à contrainte imposée opéré à haute température et d'analyses d'images obtenues par microscopie électronique à balayage (MEB). Pour la première fois, l'interaction entre le comportement rhéologique du système et le degré d'agrégation est analysé, tout comme le lien avec la sédimentation des particules. Sur la base des données expérimentales acquises, un calcul d'équilibre des forces est réalisé pour illustrer les différents scénarios d'agrégation. Ce travail fournit des nouvelles données pour la modélisation et le contrôle du processus de vitrificationIn France, borosilicate glass is used as a matrix to immobilize nuclear fission products resulting from spent fuel reprocessing. In the high-temperature vitrification process (1200 °C), most of elements to be contained react chemically with the vitrification additives to form a homogeneous glass melt. Platinum Group Metal (PGM) particles are not soluble in the melt and therefore are present as suspended particles of few microns. These particles exhibit an intense aggregation tendency and consequently the suspensions may present an anomalously high apparent viscosity. These systems are characterized by a shear-thinning and a thixotropic behaviors. The present study aims to provide important inputs for the overall rheological behavior of this system and its features through the characterization of a simulated nuclear glass melt containing 3.0 wt% (1.02 vol%) of PGM particles. A mathematical modeling of the thixotropic behavior of glass melts containing PGM particles is presented for the first time using a model similar to that proposed by Houska (Houska, 1981). This predictive model allow to describe experimental results obtained both in steady state and transient conditions. The impact of the shear stress and time on PGM aggregation degree and sedimentation kinetics is determined using an imposed-stress rheometer at high temperature and imaging analyses via Scanning Electron Microscopy (SEM). For the first time, the interplay between the rheological behavior of the system and the aggregation degree is provided, as well as the link with the particles settling. Based on the acquired experimental data, a force balance computation is executed to illustrate the different aggregation scenarios. The work provides a new input for the modeling and control of the vitrification process
46
Alshana, Usama Ahmed. "Separation And Quantitation Of Some Platinum Group Metals By Rp-hplc." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12605760/index.pdf.
Full textAbstract:
In this study, a reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed to separate and determine Pt and Pd after formation of their chelates with N,N-diethyl-N'-benzoylthiourea (DEBT). With the aim of reducing the number of steps in treating the samples, the method developed does not require the elimination of excess chelating reagent before the analysis of metal chelates. The different physical and chemical parameters affecting separation were examined in details. The whole analysis was completed on a C18 column in 16 min at 280 nm, with the mobile phase of acetonitrile-methanol-water (80:10:10, v:v:v) containing 0.20 mol l-1 pH 5.0 acetate buffer at a flow rate of 0.8 ml min-1. Detection limits of the method, based on 3s, were found as 14.2 ug l-1 for Pd and 0.77 mg l-1 for Pt using a 20-ul sample loop. Reproducibility of the method for ten repeated measurements was found as 2.36 % for 0.60 mg l-1 Pd and 2.58 % for 10.0 mg l-1 Pt as % RSD. The proposed method is a rapid, simple and highly selective method for the simultaneous determination of Pt and Pd by HPLC without the need for any interference elimination process.
47
Shi, Peipei. "Geochemical assessment of the bioavailability of platinum group metals for phytomining." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57880.
Full textAbstract:
Phytomining is suggested as a novel technology to obtain platinum group metals (PGMs) nanoparticles from plants grown on the mineralized soil, rock, or on mine wastes. The primary determinant of metal uptake by a plant is the bioavailability of the metal in the soil-plant system. In this thesis project, the bioavailability of PGMs of several PGM-rich materials is assessed with respect to phytomining. Notably, feed, concentrate and tailings from North American Palladium (NAP) in Canada, and two gossan samples from Broken Hill (BH) mineral complex in Australia are assessed in the context of phytomining. Geochemical techniques are used to obtain the mineralogy, the total concentration of PGMs, and concentrations of PGMs extracted by chemicals. These methods assess the bioavailability of PGMs in the samples and enable the estimation regarding the available concentrations of Pd, Pt, Au and Cu to plants. Soil-associated factors such as pH, salinity (EC), and cation exchange capacity (CEC) have been shown to influence indirectly the bioavailability of PGMs. Thus, soil-associated factors were analyzed. Additionally, a selection model for the substrate of phytomining is proposed. The criteria for choosing substrate for the phytomining of Pd include available Pd concentration, pH, EC, CEC and available Cu concentration. This thesis concludes that the PGM species that can be extracted by ammonium acetate are the best indicators of their natural availability to plants. Those PGMs that can be extracted by fulvic acid and citrate-dithionite are good indicators as they can be soluble in soils. According to the selection model, the available Pd concentration of BH gossan 1 is higher than 2 mg/kg. Its low EC, high CEC, and proper pH make it a suitable substrate for plant growth. It is the best “one” of the five samples for phytomining of Pd. One thing to note is that high Cu-tolerant plant species should be chosen to grow on BH gossan 1 due to its high Cu concentration available to plants.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
48
McAslan, Ewan Blyth. "Synthetic, structural and spectroscopic studies on some platinum group metal complexes." Thesis, University of Edinburgh, 1986. http://hdl.handle.net/1842/28560.
Full text
49
Shams, Leyla. "Accumulation of platinum group elements by the marine microalga, Chlorella stigmatophora." Thesis, University of Plymouth, 2010. http://hdl.handle.net/10026.1/309.
Full textAbstract:
Very little information exists on the marine biogeochemistry of Rh, Pd and Pt, or the platinum group elements (PGE), an emerging group of contaminants whose principal emissions are associated with the abrasion of the catalytic converter in motor vehicles and chemotherapy drugs discharged in hospital wastes. In this study, Rh(III), Pd(II) and Pt(IV) were added individually and in combination to cultures of the marine microalga, Chlorella stigmatophora, maintained in coastal seawater at 15oC and under fluorescence lighting both in the presence and absence of trace nutrients (e.g. Fe, Co, Zn and EDTA). The accumulation of PGE was established under varying conditions (pH, algal biomass, PGE concentration, time) by ICP-MS analysis of seawater and nitric acid digests and EDTA washes of the alga, the latter giving a measure of PGE adsorption by C. stigmatophora. Under all conditions the extent of accumulation was in the order: Rh > Pd >> Pt. In short-term (24-h) exposures, accumulation isotherms were quasi-linear up to PGE concentrations of 30 ug L-1, although Pd displayed convexity, hence saturation of available binding sites, at greater concentrations. The pH, adjusted between about 5.5 and 9.5 by addition of acid or base, did not have a great impact on PGE accumulation, with Rh displaying a moderate increase in accumulation and Pd a moderate reduction with increasing pH. More important, all PGE displayed a significant reduction in accumulation on a weight-normalized basis with increasing concentration of algae, an effect not reported for metal-marine algal interactions previously in the literature. Longer-term experiments showed that the rates of both overall accumulation and internalization were greatest for Pd and least for Pt. Consistent with this observation, the toxicity to C. stigmatophora evaluated by both pigment content and growth rate, was significantly greater for Pd than for Pt. Differences in the biogeochemical behaviours among the PGE are attributed to differences in their aqueous speciation in seawater, different affinities for the algal surface, different tendencies to cross the cell membrane, and especially with regard to Pd and Pt, differences in the rates of these interactions. Thus, although the equilibrium chemistries of Pd and Pt are very similar, their differential biogeochemistries are the result of kinetic constraints on reactions involving the latter. Because the environmental concentrations of PGE are predicted to increase with increasing emissions from vehicles and hospitals, the results of this study make an important contribution to an improved understanding of the likely effects and fates of these emerging contaminants in the marine environment. The results are also more generally important to an improved understanding of the interactions of trace metals with microalgae in seawater.
50
Wright, Edward Anthony. "A study of the hydrogen evolution reaction on platinum group metals." Thesis, University of Exeter, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414258.
Full text