Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 72-74). Also available on the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 232-249).

Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Jones, Christopher; Committee Member: Agrawal, Pradeep; Committee Member: Teja, Amyn; Committee Member: Weck, Marcus; Committee Member: Zhang, John.

Dissertation (Ph.D.)--Worcester Polytechnic Institute. / Keywords: supported catalyst; spin coating; atomic layer deposition; carbon nanotubes; model catalyst; ferrocene; thin film coating. Includes bibliographical references. (p.256-258)

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 72-74). Also available on the Internet.

No description available.

The current upgrading catalysts are mainly based on the use of expensive noble metals, which are subject to deactivation due to sintering and coking. An alternative would be to introduce a non-noble metal-based catalyst. In this work, supported molybdenum carbide based systems have been assessed for this purpose. These catalysts were formed by impregnation of zirconia (and zirconium hydroxide) and sulfated zirconia (and zirconium hydroxide) with different loadings of MoO3, with an aim of finding a balance between acid sites and metal-like sites (a site capable of performing dehydrogenation and hydrogenation function without necessarily being a metal). The synthesised catalysts were carburised between 823 and 1123 K using a mixture of methane and hydrogen (4:1) in an attempt to obtain β-Mo2C/ZrO2 or β-Mo2C/S ZrO2. Carburisation at 923 K and above resulted in molybdenum carbide with minimal or no oxygen contents. The conversion and specific rate increased with temperature. Conversion was inversely proportional to space velocity. Analysis of the products distribution as a function of conversion implies that the reaction did not simply follow a consecutive reaction pathway, but that other parallel routes were involved. Conversion increased the research octane number (RON) to ca. 66 due to the increased fraction of pentane isomers. Catalyst carburised at 823 K was approximately four times more active compared to those carburised at 923 K and above, but were of similar activity with Pt/sulfated zirconia. The non-noble metal based catalysts were stable at the reaction temperature while the Pt/sulfated zirconia catalyst deactivates.

abstract: Zinc oxide nanowires ( NWs) have broad applications in various fields such as nanoelectronics, optoelectronics, piezoelectric nanogenerators, chemical/biological sensors, and heterogeneous catalysis. To meet the requirements for broader applications, the growth of high-quality ZnO NWs and functionalization of ZnO NWs are critical. In this work, specific types of functionalized ZnO NWs have been synthesized and correlations between specific structures and properties have been investigated. Deposition of δ-Bi2O3 (narrow band gap) epilayers onto ZnO (wide band gap) NWs improves the absorption efficiency of the visible light spectrum by 70%. Furthermore, the deposited δ-Bi2O3 grows selectively and epitaxially on the {11-20} but not on the {10-10} facets of the ZnO NWs. The selective epitaxial deposition and the interfacial structure were thoroughly investigated. The morphology and structure of the Bi2O3/ZnO nanocomposites can be tuned by controlling the deposition conditions. Various deposition methods, both physical and chemical, were used to functionalize the ZnO NWs with metal or alloy nanoparticles (NPs) for catalytic transformations of important molecules which are relevant to energy and environment. Cu and PdZn NPs were epitaxially grown on ZnO NWs to make them resistant to sintering at elevated temperatures and thus improved the stability of such catalytic systems for methanol steam reforming (MSR) to produce hydrogen. A series of Pd/ZnO catalysts with different Pd loadings were synthesized and tested for MSR reaction. The CO selectivity was found to be strongly dependent on the size of the Pd: Both PdZn alloy and single Pd atoms yield low CO selectivity while Pd clusters give the highest CO selectivity. By dispersing single Pd atoms onto ZnO NWs, Pd1/ZnO single-atom catalysts (SACs) was synthesized and their catalytic performance was evaluated for selected catalytic reactions. The experimental results show that the Pd1/ZnO SAC is active for CO oxidation and MSR but is not desirable other reactions. We further synthesized ZnO NWs supported noble metal (M1/ZnO; M=Rh, Pd, Pt, Ir) SACs and studied their catalytic performances for CO oxidation. The catalytic test data shows that all the fabricated noble metal SACs are active for CO oxidation but their activity are significantly different. Structure-performance relationships were investigated. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2017

Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro / A desidrogenação de hidrocarbonetos é um importante processo industrial, devido à grande demanda de hidrocarbonetos insaturados para produtos e processos industriais. Hidrocarbonetos insaturados são utilizados na manufatura de vários produtos, tais como detergentes, gasolina de alta octanagem, produtos farmacêuticos e borrachas sintéticas. Na desidrogenação de hidrocarbonetos, o catalisador comercial utilizado é à base de platina suportado em alumina. A acidez intrínseca do suporte é neutralizada por um metal alcalino ou alcalino terroso, geralmente lítio. Índio e estanho são utilizados como promotores da fase metálica. O presente trabalho teve como objetivo principal o estudo das propriedades de catalisadores de Pt modificados com adição de In e suportados em nióbia, óxido redutível sujeito ao efeito da forte interação metal-suporte (SMSI). Catalisadores Pt/Nb2O5 foram testados recentemente na desidrogenação de alcanos e apresentaram resultados promissores. Catalisadores Pt/Nb2O5 e Pt-In/Nb2O5 foram preparados por impregnação seca e caracterizados por redução à temperatura programada (TPR), espectroscopia no UV-Visível com reflectância difusa (DRS), quimissorção de H2 e CO, dessorção à temperatura programada de H2 e CO (TPD), além de oxidação à temperatura programada (TPO). A atividade catalítica desses catalisadores foi avaliada na desidrogenação do cicloexano, na hidrogenólise do metilciclopentano, na conversão do n-heptano e na reforma do metilciclopentano. A análise dos perfis de TPR permitiu concluir que há uma interação entre Pt e In nos catalisadores bimetálicos, que foi confirmada pelo decréscimo na capacidade de adsorção, medidas pelos consumos de H2 e CO. A adição de In também inibiu o efeito da forte interação metal-suporte (SMSI) entre a platina e a nióbia. A desidrogenação do cicloexano para o catalisador Pt/Nb2O5 mostrou a criação de novos sítios interfaciais. As reações de hidrogenólise foram suprimidas pela presença do efeito SMSI e pela presença do In, como foi observado na hidrogenólise do metilciclopentano. Na conversão do n-heptano, todos os catalisadores suportados em nióbia mostraram uma alta seletividade para a formação de olefinas. A presença do In suprimiu reações de hidrogenólise e favoreceu a atividade e a estabilidade do catalisador. Na reforma do metilciclopentano todos os catalisadores apresentaram boa seletividade para produtos de desidrogenação. / Hydrocarbon dehydrogenation is an important industrial process, due to the high demand of unsatured hydrocarbons for industrial processes and products. Unsatured hydrocarbons are used in the manufacture of several products, such as detergents, high octanage gasoline, pharmaceutical products and synthetic rubber. The commercial catalysts employed in the hydrocarbon dehydrogenation process is based on platinum supported on alumina. The intrinsic acidity of the support is neutralized by an alkaline or alkali earth metal, usually lithium. Indium and tin are used as promoters of the metallic phase. The present work aimed to study the property of niobia supported Pt catalysts modified by In. Nióbia is a reductible oxide, able to promote a strong metal support interaction effect (SMSI). Pt/Nb2O5 catalysts were investigated recently in the dehydrogenation of alkanes and they presented promissing results. Pt/Nb2O5 and Pt-In/Nb2O5 were prepared by incipient wetness and characterized by temperature-programmed reduction (TPR), UV-Vis diffuse reflectance spectroscopy (DRS), H2 and CO chemisorption, H2 and CO temperature-programmed desorption (TPD), besides temperature-programmed oxidation (TPO). The catalytic activity of these catalysts was evaluated in the cyclohexane dehydrogenation, methylcyclopentane hydrogenolysis, n-heptane conversion and methylcyclopentane reforming. The analysis of TPR profiles allowed to conclude that there is an interaction between Pt and In in the bimetallic catalysis, which was confirmed by the decrease in the adsorption capacity measured by the H2 and CO uptakes. In addition it also inhibited the metal support effect (SMSI) between platinum and niobia. Cyclohexane dehydrogenation results demonstrated the creation of new interfacial sites for Pt/Nb2O5 catalysts. Hydrogenolysis reactions were suppressed by the presence of the SMSI effect and by the presence of In, as observed in the methylcyclopentane hydrogenolysis. In the n-heptane conversion, all the niobia-supported catalysts displayed a high selectivity for the olefin formation. The presence of In decreased the formation of hydrogenolysis products and increased the stability of the catalyst. In the reforming methylcyclopentane all the catalysts displayed a high selectivity for the dehydrogenation products.

Seven β-triketimine nickel complexes C1-C7 with composition [L1-7Ni(μ-Br)2NiL1- 7][BArF4]2, where L1 = HC{C(Me)=N(2,4,6-Me3C6H2)}3, L2 = HC{C(Me)=N(2,6- Me2C6H3)}3, L3 = HC{C(Me)=N(2,4-Me2C6H3)}3, L4 = HC{C(Me)=N(2-MeC6H4)}3, L5 = HC{C(Me)=N(2,4,6-Me3C6H2)}2{C(Me)=N(2,6-Me2C6H3)}, L6 = HC{C(Me)=N(2,4,6-Me3C6H2)}{C(Me)=N(2,6-Me2C6H3)}2, and L7 = HC{C(Me)=N(2,4,6-Me3C6H2)}{C(Me)=N(2,6-iPr2C6H3)}2 were synthesized from the interaction of nickel(II) bromide with L1-7 in the presence of NaBArF (BArF = [(3,5- (CF3)2C6H3)4B]−). These complexes were then fully characterized by single-crystal X- ray diffraction (XRD), MALDI-MS and elemental analysis. From XRD results, they were found to be five-coordinated dimeric bromide-bridged species [LNi(μ- Br)2NiL][BArF]2. The geometry at nickel was distorted square pyramidal, with the τ parameter in the range 0.05 to 0.28. In addition, an enamine-diimine nickel complex C8: (L2-NiBr2) was synthesized from triketimine ligand L2 and nickel dibromide in THF, thus lacking the weakly co-ordinating BArF anion. This complex was found to be pseudotetrahedral, where only two of the three imine nitrogen atoms co-ordinated. These two nitrogen atoms and two bromine atoms formed the coordination shell of Ni(II). The six-membered ring [Co-N1-C2-C3-C4-N2] adopted a boat conformation. These complexes (C1-C7) were screened in the polymerization of ethylene monomer using methylaluminoxane (MAO) as cocatalyst in toluene as solvent at 30°C. It was observed that the steric and electronic variations conferred on the complexes by ligands L1-7 had a strong influence on the activity and also on the properties of the produced polyethylene. The catalytic activity decreased in the order C2 > C1 > C6 > C5 > C7 in the range 3229 to 271 kg PE (mol Ni)-1 h-1 for a standard set of conditions (3 bar ethylene, 30 ̊C, Al:Ni 2000), while the catalysts C3 and C4, bearing only a single ortho substituents, were inactive under identical conditions. Those conditions also had strong influences on catalyst activity and polymer properties: Al:Ni ratio in the range 500 to 3000 maximized activity at 2000. For the polymerization temperature in the range 20 to 50 °C, the activity was maximized at 30 °C, while the number of branches increased with temperature while Mn decreased due to increased chain transfer. Increasing the polymerization pressure resulted in fewer branches while the molecular weight increased because of high concentration of ethylene monomer. The effect of the nature of the counterion on polymerization activity and on the polymer properties was investigated when ethylene was polymerized by C8 (N,N-Ni) and C2 (N,N,N-Ni). It was found that polyethylene produced by C8 had significantly greater crystallinity (Tm 59 ̊C, 35 branches per 1000 carbons) than that produced by C2 (Tm 36 ̊C, 53 branches per 1000 carbons). The presence of the weakly nucleophilic counterion (BArF) as in C2, may have facilitated chain walking, resulting in a branched polymer, whereas [MeMAO]- (C8) was a slightly more nucleophilic counterion impeding chain walking. Furthermore, activity was also much greater for C2 than for C8. This is the first report of an anion effect on branching.