The partial oxidation of methanol to formaldehyde with air as oxidant has been studied with supported monometallic and bimetallic catalysts of copper and silver over a range of temperature and contact times. This was done to investigate the influence the bimetallics could possibly have on either the reaction pathways and/or the product(s) selectivity of the oxidation of methanol. Characterisation of these catalysts was performed by nitrogen adsorption and porosity measurements, XRD, and IR spectroscopy of adsorbed methanol and of adsorbed CO. These results indicated no crystalline phases of the loaded metals to be present. CO adsorption showed the presence of small cluster metal atoms on the surface of the catalysts. The reduction peaks from TPR also revealed the presence of partially oxidised and dispersed metal atoms. Infra-red studies of methanol adsorbed on these sample catalysts revealed the presence of intermediate methoxy and formate species which are believed to be formed in the course of the reactions. Results showed the monometallic copper and silver catalyst to be more active than the bimetallics. Although formaldehyde selectivities and yields were generally low, they were highest for the bimetallics supported on the silica catalyst than the monometalics and alumina supported samples. Copper-silver interaction in the bimetallic was proposed to enhance the reduction of the silver that enhanced the selectivity to formaldehyde. In particular under conditions, low conversions of methanol saw highest selectivities to formaldehyde. There was also a pronounced effect of the supports on product distribution and activities with the alumina based samples being more active than the silica supported ones, with the product distributions on the alumina supported significantly showing high yields of DME while the silica showed high yield for methyl formate with COx and CH4 detected in small quantities on all the catalysts within the parameters investigated.

No description available.

As levels of carbon dioxide continue to increase in the atmosphere, it is appealing to consider the prospect of utilizing CO2 as a C1 building block for the synthesis of value-added organic chemicals. Such transformations offer potential to directly counteract environmental concerns, and could also enhance the recyclability of current materials. To meet this challenge, the development of metal catalysts capable of promoting the functionalization of carbon dioxide is necessary. Furthermore, there is great interest in employing main group metals for these transformations, particularly those metals that are earth-abundant, non-toxic and affordable. To address these needs and others, the research herein has been driven by the synthesis and characterization of main group metal hydride, alkyl and fluoride complexes with the ultimate aim of developing catalysts for CO2 functionalization. Chapter 1 investigates the synthesis of magnesium, zinc and calcium complexes supported by the tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl)]methyl ligand, [TismPriBenz]. Most significantly, the magnesium carbatrane compound, [TismPriBenz]MgH, which possesses a terminal hydride ligand, has been synthesized and structurally characterized. The corresponding magnesium methyl derivative, [TismPriBenz]MgMe, was also prepared, and the reactivity of these compounds with respect to both metathesis and insertion is explored in great detail. The synthesis and characterization of the corresponding zinc hydride complex, [κ3 TismPriBenz]ZnH, is also described, as well as the preparation of a rare example of a monomeric calcium benzyl compound, [TismPriBenz]CaCH2Ph. Some reactivity of the zinc and calcium derivatives is also described. In Chapter 2, the aforementioned magnesium and zinc compounds and their reactivity towards CO2 is described in detail. Systems comprised of [TismPriBenz]MH (M = Mg, Zn) and tris(pentafluorophenyl)borane are highly effective for the room temperature reduction of CO2 with R3SiH to afford sequentially the bis(silyl)acetal, H2C(OSiR3)2, and CH4 (R3SiH = PhSiH3, Et3SiH and Ph3SiH). Notably, the selectivity of the catalytic system may be controlled by the nature of the silane. Catalytic intermediates were isolated and structurally characterized, including an interesting magnesium formatoborate complex, which has helped elucidate an understanding of the mechanism of the catalysis. Most significantly, it was found that H2C(OSiPh3)2 can be prepared on a multi-gram scale as a crystalline solid and can be converted directly into formaldehyde (CH2O), which is an important industrial chemical. Thus, H2C(OSiPh3)2 can serve as a formaldehyde surrogate and its ability to provide a means to incorporate CH and CH2 moieties into organic molecules is described. Isotopologues of H2C(OSiPh3)2, namely D2C(OSiPh3)2, H213C(OSiPh3)2, and D213C(OSiPh3)2, may be synthesized from the appropriate combinations of (12C/13C)O2 and Ph3Si(H/D), thereby providing a direct and convenient means to use carbon dioxide as a source of isotopic labels in complex organic molecules. In Chapter 3, details pertaining to other transformations catalyzed by [TismPriBenz]MgR (R = H, Me) are provided and their mechanisms are discussed. Notably, [TismPriBenz]MgR is a catalyst for hydrosilylation and hydroboration of styrene to afford exclusively the Markovnikov products, Ph(Me)C(H)SiH2Ph and Ph(Me)C(H)Bpin; the magnesium alkyl intermediate in the catalytic process, [TismPriBenz]MgCH(Me)Ph, has been isolated and structurally characterized, providing the first structural evidence for the insertion of an olefin into a magnesium hydride bond. Other catalytic transformations are described, including hydroboration of carbodiimides to form N-boryl formamidines and hydroboration of pyridine to provide N-boryl 1,4- and 1,2-dihydropyridines. Additionally, the ability for the magnesium hydride and methyl complexes to catalyze dehydrocoupling reactions is discussed. Finally, the ability for [TismPriBenz]MgMe to catalyze the isomerization of a terminal alkyne is reported. Chapter 4 outlines the chemistry of magnesium and zinc compounds supported by a different scaffold, namely, the tris(3-tert-butyl-5-methylpyrazolyl)hydroborato, [TpBut,Me], ligand. The magnesium methyl compound, [TpBut,Me]MgMe, was used as a precursor to prepare [TpBut,Me]MgF via metathesis with Me3SnF, and is the first example of a structurally characterized monomeric magnesium fluoride complex. The reactivity of [TpBut,Me]MgF is described, including its ability to serve as a hydrogen bond and halogen bond acceptor, such that it forms adducts with indole and C6F5I. Corresponding zinc chemistry was studied, including interesting reactivity of [TpBut,Me]ZnH and [TpBut,Me]ZnF. Finally, new heterobimetallic compounds containing magnesium or zinc supported by the [TpBut,Me] ligand and tungsten were synthesized and structurally characterized.

No description available.

Thesis (M.S.)--University of Florida, 2004. / Title from title page of source document. Document formatted into pages; contains 60 pages. Includes vita. Includes bibliographical references.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Hydrogen has now become a suitable candidate for alternative energy generation for small scale applications with the aid of fuel cells. On-board production of hydrogen from methane is the most preferred method via a series of catalytic reactions. However, the carbon monoxide (CO) concentrations following these reforming steps is still too high (±1 %) and is detrimental to the anode of the fuel cell. For maximum output and efficiency of the fuel cell CO concentrations must be reduced to less than 10 ppm. Preferential oxidation (PROX) following the water-gas shift reaction is a promising method that could be employed to reduce the CO content in the reformate gas. This project entails the synthesis, characterization and testing of nickel based catalysts for the oxidation of CO in H₂ rich streams, and to dope with Pt to determine the effects of the platinum group metal on the catalyst for this reaction. A series of NiO/Al₂O₃, Pt/Al₂O₃ and Pt/NiO/Al₂O₃ catalysts were prepared by incipient wetness technique. These catalysts were characterized by TGA, ICP-OES, XRD, BET, TPR, TPD, N₂ adsorption desorption isotherms, CO chemisorptions, SEM-EDX and TEM. The catalysts were then tested for the oxidation of CO in H₂ rich streams. XRD patterns of the catalysts indicated the presence of NiO and PtO phases on the respective supports and in situ redox reactions showed catalysts had reversible phase changes (oxide and metallic) that were stable. N2 adsorption-desorption isotherms indicated the presence of mesoporous materials for all catalysts studied. Impregnation of Pt on the NiO/Al₂O₃ catalysts promoted the reduction of the catalyst to lower temperatures. All catalysts were stable for long periods of time in the presence of H₂ at 150 °C. NiO/Al₂O₃ catalysts were not very active for the preferential oxidation of CO within its stipulated temperature ranges giving the highest CO conversion at 290 °C of 11 % with the selectivity towards CO₂ of ± 25 %. The Pt/Al₂O₃ showed much better activity at higher PROX temperatures compared to the NiO/Al₂O₃ with regards to CO conversion and selectivity towards CO₂. The highest CO conversion obtained within the PROX range was ±56 % with a selectivity towards CO₂ of 68 % at 200 °C. The Pt/NiO/Al₂O₃ showed a synergistic effect, with much higher CO₂ selectivity and CO conversion within the PROX temperature ranges compared to both mono-metallic catalysts studied. The highest CO conversion obtained for this catalyst was at 180 °C of 99.9 % with a selectivity towards CO₂ of 74 %. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2012.

Thesis (Ph. D.)--University of North Texas, Dec., 2007. / Title from title page display. Includes bibliographical references.

Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 195-204). Also available online in ProQuest, free to University of Oregon users.

Thesis (M.S.)--West Virginia University, 1998. / Title from document title page. Document formatted into pages; contains xii, 136 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 131-132).