Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references. Also available in electronic version.

Submitted in fulfillment of the requirements for the Master of Engineering Degree, Durban University of Technology, Durban, South Africa, 2018. / Ethanol and butanol obtainable through fermentation of lignocellulose biomass have become promising alternative feedstock for production of fuels as they are biodegradable and sustainably regenerated via the photosynthesis cycle. The properties of hydrocarbons produced through alcohol conversion closely resemble those of gasoline. Catalytic systems are reported to play a vital role during alcohol conversion to hydrocarbons. In this study ethanol and butanol were used as a feedstock for production of hydrocarbons over Fe, Zn and Ni catalyst systems supported on zeolite ZSM-5 (Zeolite Socony Mobil-5) and activated carbon (AC). X- Ray Diffraction (XRD), Scanning Electron Microscope (SEM) coupled with Energy- dispersive X-ray spectroscopy (EDS) and Brunauer, Emmet, and Teller (BET) analyses were employed for catalyst characterization. XRD patterns confirmed the success of metal doping on ZSM-5 and activated carbon supports. Major peaks at 7.96° and 23.97° corresponding to ZSM-5 crystals were observed in ZSM-5, and AC was found to be amorphous. Impregnation with metals reduced the crystallinity of ZSM-5 supported catalysts. Whereas SEM analysis showed that catalysts supported on ZSM-5 exhibited irregular shapes and catalyst supported on activated carbon exhibited disordered structures. The BET analyses confirmed that the surface areas of promoted catalysts decreased after metal doping. Evaluation of the catalysts were carried out in a ½ inch stainless steel reactor at 400 °C and atmospheric pressure with a weight hourly space velocity (WHSV) of 2.5 h-1 (g feed)/ (g catalyst). The ZSM-5 support performed better than activated carbon support. More than 90% conversion was achieved over catalysts supported on ZSM-5. Production of hydrocarbons over catalysts supported on activated carbon were as a result of the active component. Conversion of feedstock was observed to produce more benzene, toluene and xylene (BTX) compounds with an increase in butanol content. 100% conversion was achieved with pure butanol and not more than 99.86% conversion was achieved with pure ethanol. Catalyst systems supported on HZSM-5 and activated carbon were successfully synthesised. Ethanol, butanol and ethanol-butanol mixtures were successfully converted to liquid hydrocarbons and the conversion was greater than 90%. On the promoted catalysts, production of BTX were suppressed and various metals were observed to perform differently. / M

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The x-ray structures of several alkyl halide, alkyl dihalide, and hydrogen adducts to pyrazolyl-bridged diiridium complexes [special characters omitted] are determined. The diiridium (bis-pyrazolyl) core of these complexes enables contact between the two centers so that metal-metal bond formation may occur, exemplified by a short iridium-iridium distance of 2.78(I) A in the diiridium(II) complex [special characters omitted]. Oxidation mechanisms are postulated based on reaction kinetics. The oxidative addition of methyl iodide to [special characters omitted] is observed to occur by a two-step mechanism, where a high positive ΔS‡ term may be due to a highly ordered intermediate. This is proposed as evidence for an [special characters omitted] addition, where coordination of the alkyl halide is followed by halide dissociation and migration to a trans diaxial coordination site. Different kinetics of the reaction are observed in THF and benzene, which is also attributed to a polar [special characters omitted] intermediate. Occupation of the 3,3’ and 5,5’ positions of the pyrazolyl ligand decreases the reaction rate by an order of magnitude or greater, which indicates steric inhibition of the reaction by the bridging ligands. Experimental evidence for a competing light-induced reaction that corresponds to a radical-chain mechanism rather than the dark [special characters omitted] reaction is also presented. Oxidative isomerization of an iodo (iodomethylene) complex to the methylene-bridged isomer is determined to be an intramolecular process based on isotope labelling experiments and kinetics. Negligible isomerization to the bridging methylene complex under ambient conditions is attributed to coordinative saturation; the stability of [special characters omitted] is likewise due to coordinative saturation of the metal centers. The addition of hydrogen or hydride to [special characters omitted] is possible through a number of synthetic routes, but the stereochemistry of the iridium(II) hydrido complexes is such that the metal-hydride and iridium-iridium bonds do not occupy coordination sites trans to each other: it is proposed that the strong σ-trans effect of the hydride induces structural rearrangements in substitution reactions so that stereochemistry of parent complexes is not conserved. This is demonstrated by the x-ray structures of [special characters omitted]. The hydride ligand promotes nucleophilic attack on an electron-rich iridium center; thus water and other Lewis bases are found to react with the cationic diiridium hydride complex [special characters omitted]. / Graduate

The ligands of the ten-membered series, [10]-aneS3, [10]- aneS2N, [10]-aneSN2 and the macrobicyclic ligand - 1,4-bis(1-aza- 4,8-dithia-4-cyclodecyl) ethane, and their transition metal complexes were successfully synthesised. Chromium (III) complexes of the homoleptic hexaaza ligands [18]-aneN6 and [20]-aneN6 were synthesised, structurally characterised and their spectral properties studied. Bis complexes of Ni(II) with [10]-aneS3, [10]-aneS2N and [10]-aneSN2 were octahedral as is evident from their crystal structures. The esr spectra of the corresponding Ni(III) complexes are characteristic of a low spin d7 ion in a compressed octahedral coordination in the complex based on [10]-aneS2N and an elongated octahedral coordination in the complexes based on [10]-aneSN2 and [10]-aneS3. The spectral and electrochemical properties of the various Ni(II) complexes are compared with each other. The redox reactivity of the Ni(II) complex based on [10]-aneS3 was studied. The synthesis of a macrobicyclic ligand is described. The Ni(II)complex of the macrobicyclic ligand is a distorted octahedron and the esr spectrum of the Ni(III) complex is characteristic of a low spin d7 ion in a compressed geometry. The covalency parameter K, and the energy separation between the low spin ground state and the first excited high spin state were determined from the esr and the electronic spectra of the Ni(III) complex. Two isomers for the Pd(II) bis complexes of [10]-aneS2N were obtained and characterised by X-ray methods and nmr spectroscopy. Evidence for the formation of a high spin Pd(II) octahedral species has been provided for the first time. Oxidation of the Pd(II) complex is metal centered and the esr spectra of the Pd(III) complexes are characteristic of a low spin d7 PdS4N2 core. Fe(II), Fe (III), Co(II), Co(III), Ni (II) and Pd(ll) bis complexes of the ligand [10]-aneS3 were synthesised and characterised by elemental analysis, nmr and esr spectroscopies, where appropriate, and their spectral and electrochemical properties studied. The crystal structures of Fe(II), Co (II) and Ni(II) bis complexes of [10]-aneS3 were octahedral with three S atoms from each of the thioether ligands coordinated to the central metal ion. The esr spectra of the Fe(III) bis complexes of [9]-aneS3 and [10]-aneS3 were characteristic of a low spin d5 complex ion. The ligand field distortion parameters were obtained from the electronic and esr spectra and the energies of the Jahn-Teller splitting were estimated. The Co(II, bis complex of [10]-aneS3 is low spin. The half-wave potentials due to the [special characters omitted] and [special characters omitted] couples were obtained by cyclic voltammetry. The electron self exchange rate constant for the [special characters omitted] and the [special characters omitted] couples were determined by the 59Co nmr line broadening technique for the first time. The self exchange rate constant for the [special characters omitted] couple was determined by the 'H nmr line broadening technique. The crystal structure of the Pd(II) bis complex of [10]—aneS3 is essentially square planar with significant interactions from the axial S atoms. This complex is fluxional as is evidenced in the variable temperature nmr spectra. / Graduate

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The novel bimetallic hydrides [(n⁵-C₅H₅)W(N0)IH]₂ and [(n⁵-C₅H₅)W(N0)H₂]₂ can be prepared sequentially by the metathesis of [(n⁵-C₅H₅)W(N0)IH₂]₂ with Na[H₂Al(0CH₂CH₂0CH₃)₂]. Analyses of the ¹H NMR spectra of C[(n⁵-C₅H₅)W(N0)IH]₂ and [(n⁵-C₅H₅)W(N0)IH₂]₂ show the former contains hydride ligands bound to tungsten in a terminal fashion, while the latter possesses two terminal and two bridging hydrides. Addition of a Lewis base to [(n⁵-C₅H₅)W(N0)IH]₂ results in the formation of hydride species (n⁵-C₅H₅)W(N0)IHL (L = P(0Ph)₃, P(0Me)₃, PPh₃); in like manner, the dimer [(n⁵-C₅H₅)W(N0)IH₂]₂ is cleaved by triphenylphosphite to form the monomer cis or trans [(n⁵-C₅H₅)W(N0)IH₂[P(0Ph)₃]. A comparison is made of the reactivity of the tungsten-hydrogen link in the nitrosyl hydrides (n⁵-C₅H₅)- W(N0)IH[P(0Ph)₃], (n⁵-C₅H₅)W(N0)₂H, and (n⁵-C₅H₅)W(N0)IH₂[P(0Ph)₃]. The Mo(N0)₂²⁺ unit is obtained as the tetrakis-solvate via chloride abstraction from Mo(N0)₂Cl₂ by AgBF₄ or nitrosylation of Mo(C0)₆ by NOPF₆ in coordinating solvents such as nitromethane, acetonitrile, or tetrahydro-furan. The unsolvated complex [Mo(N0)₂(PF₆)₂][aub=n] is produced if the latter reaction is performed in dichloromethane; however, it readily converts to [Mo(N0)₂S₄](PF₆)₂ upon exposure to coordinating solvents (S). Hard Lewis bases (L = CH₃CN , 0PPh₃ or L₂ = 2 ,2-bipyridine replace the solvent molecules in [Mo(N0)₂S₄]X₂ (X = BF₄⁻, PF₆⁻) forming complexes [Mo(N0)₂L₄]²⁺ or [Mo(N0)₂L₂S₂]²⁺ depending upon the solvent employed. Reagents capable of being oxidized appear to reduce the dinitrosyl dication without permanent coordination to the molybdenum centre. Reduction of [Mo(NO)₂S₄](PF₆)₂ or [Mo(N0)₂(PF₆)₂][sub=b] is effected by sodium amalgam (one equivalent); addition of a ligand L₂ (L₂ = 2,2-bipyridyl, 3,4,7,8-tetramethyl-1,1O-phenanthroline) to the reaction mixture permits the isolation of [M(NO)₂L₂]₂(PF₆)₂. Addition of excess ligand results in the formation of non-nitrosyl containing species [Mp(L₂)₃]PF₆ (L = 0PPh₃ or L₂ = 3,4,7,8-tetramethyl-1 ,10-phenanthro- line). Decomposition of the nitrosyl species results from attempts to reduce [Mo(NO)₂S₄]²⁺ by two electrons. New complexes are identified by the aid of IR and ¹H, ¹⁹F, or ³¹P NMR spectroscopy and conductance measurements. Attempts to prepare thionitrosyl analogues of [Mo(N0)₂L₄]²⁺ have met with limited success; the only wel1-characterized thionitrosyls isolated in this study are the known (n⁵-C₅H₅)Cr(C0)₂NS and the new [(n⁵-C₅H₅)Mo-(N0)(NS)PPh₃]BF₄. Also discussed is the interaction of NOPF₆ with solvents. NOPF₆ has been found to react slowly with acetonitrile, a common solvent for nitro-sonium salts. / Science, Faculty of / Chemistry, Department of / Graduate

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22453号 / 工博第4714号 / 新制||工||1736(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 松原 誠二郎, 教授 杉野目 道紀, 教授 中尾 佳亮 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM