Copper oxide supported on alumina (CuO/Al2O3), silica (CuO/SiO2) and chromia (CuO/Cr2O3) have been synthesized and characterized. These catalysts were characterized using XRD, SEM, TEM, ICP, BET surface area and pore volume, TPR, TPD, TGA-DSC and IR. The hydrogenation of octanal using these catalysts was investigated; however, the primary focus of the project was the influence of water on the reaction and the catalysts. The initial study using CuO/Al2O3 showed that the optimum operating conditions for subsequent catalytic testing was 160 °C and a hydrogen to aldehyde ratio of two. Under these conditions, a conversion of 99 % and selectivity to octanol of 97 % was achieved. Further catalytic testing, using CuO/Al2O3 and CuO/Cr2O3, was carried out by introducing water-spiked feed into the reaction system after steady state was reached using fresh feed. Based on literature, it was initially expected that the presence of water would cause catalyst poisoning and subsequently catalyst deactivation. However, contrary to the expectation, the presence of water did not influence the activity of these two catalysts. Furthermore, the selectivity to octanol increased to 98.5 % when CuO/Al2O3 was used for the reaction, whilst a minor change in the selectivity to octanol (0.5 %) was obtained when CuO/Cr2O3 was used. The interaction of the water with the surface hydroxyls on alumina is most likely the reason for the increase in the selectivity to octanol when using CuO/Al2O3. In contrast to the other two catalysts, the reaction over CuO/SiO2 showed a steady decrease in both the conversion of octanal and the selectivity to octanol with time-onstream when using fresh feed. After 55 hours on stream, the conversion reached 22 %, (from an initial 95 %) whilst the selectivity to octanol reached 89 % (from an initial 98 %). This decline in the conversion and selectivity to octanol was possibly due in part, to the low isoelectric point of silica, with mechanical failure being the major contributing factor to the catalyst’s deactivation. The decrease in the BET surface area and the presence of smaller particles in the SEM image, confirmed that mechanical failure occurred. Since steady state was not reached and deactivation occurred, the reaction over CuO/SiO2 was also carried out using water-spiked feed. The conversion of octanal was seen to gradually decrease to 73 % after 55 hours on stream, whilst the selectivity to octanol remained unchanged at 98 % for the duration of the reaction. This showed the beneficial effect of the presence of water by slowing down the decline in catalytic activity and maintaining the selectivity to octanol. The improved selectivity obtained in the presence of water was attributed to its interaction with the silica surface hydroxyls. Since octanal conversion continued to decrease, it indicated that mechanical failure was the primary cause in the loss of catalytic activity. The used catalysts were characterized using XRD, SEM, EDS composition scanning, TEM, BET surface area and pore volume, TGA-DSC and IR. The catalysts used for the reaction with the fresh feed and the water-spiked feed were characterized and compared. Except for the deactivation of CuO/SiO2, the characterization of these catalysts showed that the presence of water did not negatively impact the make-up of the catalyst. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

PhD, Faculty of Science, University of the Witwatersrand

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the Degree of Doctor of Philosophy. J o h a n n e s b u r g , 2 0 1 3. / Structured carbon nanomaterials have attracted considerable interest because of their unique structures and outstanding properties. Among other structured carbon nanomaterials, carbon nanofibers (CNFs) have been the subject of study for several decades with particular interest having been paid towards their synthesis and application. However, control over the size and shape of these materials still remains a challenge. Three main components necessary for the synthesis of CNFs are the catalyst or template, the carbon source and the source of energy/power. It has been noted that catalyst morphology and the carbon source plays an important role in controlling CNF growth and morphology. As such one of the main challenges is to produce the catalyst particles that would yield the desired CNF morphology. In this study, we investigated methods for controlling the size and morphology of CNFs by synthesizing Ni and Cu catalysts of particular morphology, while using C2H2 and trichloroethylene (TCE) as a carbon source for the synthesis of CNFs. A mixture of TCE/C2H2 was also employed as a carbon source for comparison. The catalysts and synthesized CNFs were characterized by different techniques such as TEM, XRD, TPR, TGA, Raman spectroscopy, IR spectroscopy, etc. The synthesis of Ni nanoparticles (NPs) was achieved by reduction of Ni(acetate)2 with hydrazine (35%). CNFs were synthesized by deposition of TCE, C2H2 and their mixtures using a chemical vapor deposition technique (CVD) in the temperature range 400-800 oC. N2 and CO2 were used as carrier gases. TEM analysis of the Ni particles as a function of time revealed that the Ni underwent a morphological change with time. Further, as the temperature of the reaction changed, so did the shape of the carbon materials. The shapes changed from structures showing bilateral growth at T = 400 oC to tripod-like structures and multipod-like structures at T = 450 oC and T = 500 oC respectively. Irregular shaped materials were observed at T > 500 oC. It was also found that when acetylene or an acetylene/trichloroethylene mixture was used at T = 450 oC, helical (> 80%) and linear fibers were produced respectively. It was also demonstrated that the flow rate of H2, N2 and CO2 had a dramatic influence on the morphology of CNFs. CO2/TCEwas found to produce linear fibers with controlled sizes at 800 oC. The results demonstrated that the formation of tripod CNFs only occurs in a very narrow parameter regime. Manoko S. Maubane The preheating of the TCE prior to its deposition over a Ni particle catalyst was achieved using a double stage CVD reactor. TCE was subjected to high temperatures prior to its deposition at low temperatures. Results showed that the decomposition temperature was the key parameter in the synthesis of CNFs. It was found that during the decomposition, TCE breaks down into different species/radicals which then adsorb onto the catalyst particle to give CNFs of different morphology. Raman studies revealed that the synthesized CNFs showed an increase in graphitic nature when the temperature in the first reactor of a two stage reactor was increased. Decomposition of C2H2 was also performed over Cu NPs, and Cu modified catalysts (Cu@SiO2 and Cu/SiO2) with different silica coatings at 300 oC. These catalysts were prepared by reduction of Cu(acac)2 with hydrazine (35%). TEM images revealed that coiled CNFs were only produced from Cu/SiO2 grown in the presence of H2 (> 90 %; d = 60-70 nm). IR spectra of all the CNFs indicated the presence of surface C=C, C=O, CH3 and CH2 moieties, and that the ratios of peak intensities of C=O/CHx and C=C/CHx species indicated the variable CNF surface that was produced by the gases and the Cu particles used. It was thus revealed that the CNFs produced by different Cu catalysts have different chemical and physical properties and that these properties correlate with catalyst particle size and the gas mixtures used. CuO and SrO modified Cu catalysts (with different Cu/Sr ratios) were also employed using the CVD method for the synthesis of CNFs at 300 oC. These catalysts were prepared by a coprecipitation method. The TEM images of the CNFs revealed a mixture of straight and coiled CNFs with a broad diameter distribution (50-400 nm) dependent on the Cu/Sr ratio of the catalyst used. IR and TGA analysis revealed that the chemical composition of the CNFs changed as the SrO content changed. The SrO content also affected the Cu particle size and influenced the morphology of the Cu particles from which the CNFs grew.

Thesis (M. Tech. degree in Chemistry) Tshwane University of Technology 2013. / Discusses the nanostructured platinum group catalysts provide an efficient route for the oxidative coupling of naphthols. The potential of a new catalytic reaction described in the patent literature has not yet been fully explored, although the reaction could provide an efficient new route to chromophoric systems containing conjugated aromatic rings.

No description available.

The purpose of this study was to develop new catalytic methods to mediate carbon-carbon bond forming reactions with imines under mild conditions and in a general manner. We found that copper catalysts were compatible in cross-coupling of a range of mild organometallic reagents, providing simple, efficient routes to alpha-substituted amides and amines. / Chapter 2 of this thesis describes a new copper-catalyzed multicomponent synthesis of alpha-substituted amides. This reaction was developed based upon previous work in this laboratory, which showed that palladium catalysts were competent in Stille-type cross-coupling of imines, acid chlorides, and organostannanes. While providing a mild method of generating the amide products, a more general procedure able to incorporate a wider range of organostannanes was sought. This chapter details the development of a copper-catalyzed protocol, which, as well as performing the cross-coupling under mild reaction conditions, proceeds with a diverse range of aryl-, heteroaryl-, and vinyl-substituted organostannanes and employs an inexpensive and readily available catalyst. Through this system, control over regioselectivity of addition to alpha,beta-unsaturated imines is also possible. / Chapter 3 demonstrates that, in addition to organostannanes, other substrates are viable in copper-catalyzed cross-coupling with imines and acid chlorides. Herein, the coupling of terminal alkynes with imines and acid chlorides is described, leading to an efficient synthesis of tertiary propargylamides directly from simple starting materials. This synthesis incorporates a wide variety of substituted imines, acid chlorides/chloroformates, and terminal alkynes, providing a rapid synthesis of these useful building blocks (reaction completion in only 15 minutes). In addition, the process is shown to work with aza-aromatic heterocycles, such as pyridine, where the alkynylation occurs exclusively at the 2-position. / Chapter 4 describes the utility of these rapid multicomponent reactions, where the products are directly converted into oxazole heterocycles. Copper-catalyzed- and zinc-catalyzed protocols are developed for the synthesis of secondary propargylamides from silyl-imines, acid chlorides, and terminal alkynes. The secondary propargylamide products are then, in a one pot sequence, transformed into trisubstituted oxazoles. / Chapter 5 describes the development of an atom-economical, non-toxic alternative to the organotin coupling described in Chapter 2. This involves the use of tri- and tetraorgano-indium reagents, which can transfer all of their organic groups in a copper-catalyzed coupling with imines and acid chlorides. This reaction shows good functional group compatibility and further expands the scope of alpha-substituted amides and N-protected amines that can be synthesized through mild copper catalysis. / Chapter 6 explores the enantioselective alkynylation of nitrogen-containing heterocycles. As described in Chapter 3, heterocycles such as pyridine can undergo copper-catalyzed 1,2-addition with terminal alkynes upon activation by chloroformates. As this process generates a stereocenter, it is possible to introduce enantio-control into the reactions by using a chiral copper catalyst. With ligands from the PINAP series, enantioselectivities of up to 84% can be induced in the coupling of nitrogen-containing heterocycles (e.g., quinoline), chloroformates, and terminal alkynes. This provides a mild and simple synthesis of chiral 2-alkynyl-1,2-dihydroquinolines directly from simple starting materials.

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 1, 2009) Vita. Includes bibliographical references.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2006. / Keywords:Cooper, zinc oxide, silica. Includes bibliographical references (leaves. 46-48).

Thesis (M.S.)--Western Washington University, 2010. / Includes bibliographical references. Also issued online.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 116-125).