A two part study of hydrocarbon utilization by microorganisms was undertaken. In the first part it was decided to attempt the genetic transformation of Bacillus subtilis with respect to the ability to grow on hydrocarbon carbon source. One hundred forty-four cultures of Bacillus organisms were isolated on a medium with refined kerosene as the sole carbon source. Most of these cultures were found to be B. cereus (92 isolates), B. lentus or B. firmus (15 isolates) and B. megaterium (8 isolates). Neither of the 2 strains identified as B. subtilis were capable of sufficient growth on kerosene medium, even with complex supplements added, to warrant a transformation experiment. In the second part of this study, a culture which was classified as a member of the genus Arthrobacter was investigated for its ability to grow rapidly on hydrocarbons. Dodecane was shown to be the n-alkane utilized most readily. The acidity produced by this culture was not due to formation of fatty acids, other organic acids or amino acids and was attributed to the acidity generated by utilization of the ammonium nitrogen source. When grown in a fermentor with pH control, the Arthrobacter spp. oxidized ammonia forming nitrate and nitrogen oxide gases when the dodecane carbon source was exhausted. This is the first time ammonia oxidation has been reported in an n-alkane fermentation system. / Land and Food Systems, Faculty of / Graduate

Thesis (M.S.)--Villanova University, 2010. / Chemistry Dept. Includes bibliographical references.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016. / The production of liquid transportation fuels and chemicals by the Fischer-Tropsch (FT) synthesis continues to garner attention due to its economic and environmental benefits. This interest is also compounded by the flexibility to use readily available materials as feedstocks for synthesis gas production, with coal, natural gas, biomass and recently shale gas being used. Although this process is over 90 years old, challenges still remain. In this study, we have attempted to understand several FT synthesis challenges by exploring the use of carbon spheres as a model support for Co, Fe and Fe-Co FT catalysts. Thus the synthesis, characterization and application of carbon spheres with distinct architectures are described. The synthesis of solid carbon spheres using a sucrose precursor yielded materials that were mono-dispersed (600 nm) and adopted a necklace-like accreted conformation. Upon further investigation, it was demonstrated that annealing is useful for tuning the properties of the as-prepared materials to have high surface areas (> 500 m2/g), good thermal stability (>660 °C) and a mesoporous (> 2 nm) pore structure. Deposition of a Fe-Co bimetallic catalyst yielded oxides of the monometallic species with relatively small crystallites, with sizes in the range 7.9 – 14.4 nm. Reduction of the bimetallic samples was monitored by using in situ PXRD and TPR techniques, which revealed that a Co-Fe type-alloy is one of the phases formed on Co-rich samples at T > 450 °C. Interestingly, high relative abundances of this alloy did not correlate with high C5+ selectivities in Fischer-Tropsch synthesis; instead Co-rich/Fe-poor catalysts gave the best selectivity. The effect of the support morphology in heterogeneous catalysis was investigated by using high surface area solid and hollow carbon spheres (>560 m2/g) prepared from a resorcinol-formaldehyde precursor as support material. Loading the Co and Fe precursors on these two supports was shown by TEM and PXRD to result in smaller and well dispersed metal particles on the hollow support material. This corresponded with high activities and C5+ selectivities for the Co and Fe catalysts supported on the hollow carbon spheres. TEM studies revealed that the Co and Fe particles tended to sinter significantly when dispersed on a material with a solid architecture. iv Post-synthesis N-doping using a melamine precursor was shown by XPS to incorporate high quantities of nitrogen (up to 13%) on to the surface of the 30 nm thick shells of the hollow carbon spheres. On further investigation, N-doping by this method was shown to have minimal effects on the thermal stability and crystallinity of the materials. The N-doped HCSs were shown to be good anchors of Co particles as displayed by the good dispersion, activity and minimal sintering tendency of catalysts supported on N-doped HCSs. Studies conducted herein have demonstrated the versatility of carbon spheres as a model support, and how their properties can be tailored to suit the desired specifications by simply adjusting the synthesis parameters. We have also highlighted how the chemical inertness of these materials allows for studies on metal-metal interactions at elevated temperatures for bimetallic catalyst systems. The monodisperse, morphology-tunable aspects of carbon spheres were particularly useful in modelling the effect of the support morphology in Fischer-Tropsch synthesis. It is believed that the versatility of CSs demonstrated in this study can also be exploited in other heterogeneous catalytic systems. / LG2017

>Magister Scientiae - MSc / Due to the rapid depletion of fossil fuel reserves and the production of environmentally harmful by-products such as carbon dioxide, there is an urgent need for alternate sustainable clean energy. One of the leading candidates in this endeavour is hydrogen, which can be used as an energy carrier since it has a high energy density, zero emissions and is produced from non-depletable resources such as water. The major challenge hindering a hydrogen economy is the lack of safe and effective storage technologies for mobile applications. A prospective solution to this problem lies in the use of porous powdered materials, which adsorb the hydrogen gas. However, the integration of these powdered materials into a storage tank system, results in the pipelines being contaminated during filling cycles. This necessitates the shaping of the porous powdered materials. Among the many shaping techniques available, the electrospinning technique has been proposed as a promising technology since it is a versatile process that is easily scaled-up making it attractive for the applications of the study. Furthermore, the electrospinning process enables the synthesis of nano-sized fibres with attractive hydrogen sorption characteristics. In this regard, the current study employs the electrospinning technique to synthesise electrospun composite fibres for mobile hydrogen storage applications. After electrospinning three polymers, polyacrylonitrile (PAN) was selected as the most suitable polymer because it yielded bead-free electrospun fibres. However, the diameter of the PAN fibres was large/thick which prompted further optimisation of the electrospinning parameters. The optimised electrospinning conditions that yield unbeaded fibres within the desired diameter range (of 300-500 nm) were a PAN concentration of 10 wt%, a flow rate of 0.4 mL/h, a distance of 10 cm between the needle tip and collector plate, and an applied voltage of 8 kV. The study then progressed to the synthesis and characterisation of the pristine porous powdered materials which adsorb hydrogen gas. The porous powdered materials investigated were commercial zeolite 13X, its synthesised templated carbon derivative (ZTC) and Zr (UiO-66) and Cr (MIL-101) based metal-organic frameworks (MOFs). ZTC was synthesised via liquid impregnation coupled with chemical vapour deposition (CVD), and the MOFs were synthesised by the modulated solvothermal method. Analysis of the ZTCs morphology and phase crystallinity show that the carbon templated process using zeolites was successful, however, ZTC was amorphous compared to crystalline zeolite template. The BET surface area was assessed with the aid of nitrogen sorption isotherms for both zeolite 13X and ZTC, and values of 730 and 2717 m²/g, respectively were obtained. The hydrogen adsorption capacity for zeolite 13X was 1.6 wt% and increased to 2.4 wt% in the ZTC material at 77 K and 1 bar. The successful synthesis of well defined, crystalline MOFs was evident from X-ray diffraction and morphological analysis. The BET surface area and hydrogen adsorption for Zr MOF were 1186 m²/g and 1.5 wt%, respectively at 77 K and 1 bar. Cr MOF had a BET surface area of 2618 m²/g and hydrogen adsorption capacity of 1.9 wt% at 77 K and 1 bar. The main focus of the study was to synthesise electrospun composite fibres that can adsorb hydrogen gas and thus provide significant insight in this field of research. As such it examined composite fibres that incorporates porous powdered materials such as zeolite 13X, ZTCs, UiO-66 (Zr) MOF and MIL-101 (Cr) MOF and investigated their ability to adsorb hydrogen gas, which have not been reported previously. The synthesis of composite fibres was achieved by incorporating the porous powdered materials into the PAN resulting in a polymeric blend that was then electrospun. Morphological analysis illustrated that the porous powdered materials were successfully supported by or incorporated within the PAN fibres, forming composite fibres. The BET surface area of the 40 wt% zeolite-PAN and 12.5 wt% ZTC-PAN composite fibres were 440 and 1787 m²/g respectively. Zr MOF and Cr MOF composite fibres had a BET surface area of 815 and 1134 m²/g, respectively. The BET surface area had reduced by 40, 34, 31 and 57% for zeolite 13X, ZTC, Zr MOF and Cr MOF, respectively after these porous powdered materials were incorporated into PAN. The hydrogen adoption capacity for 40 wt% zeolite-PAN, 12.5 wt% ZTC-PAN, 20 wt% Zr MOFPAN and 20 wt% Cr MOF-PAN composite fibres was 0.8, 1.8, 0.9 and 1.1 wt%, respectively. This decrease was attributed to the limited amount of porous powdered materials that could be incorporated into the fibres since only 40 wt% of zeolite 13X, 12.5 wt% of ZTC and 20 wt% of the MOFs were loaded into their respective composite fibres. This was due to the fact that incorporation of greater amounts of porous powdered materials resulted in a viscous polymeric blend that was unable to be electrospun. It is evident from the study that electrospinning is a versatile process that is able to produce composite fibres with promising properties that can potentially advance the research in this field thus providing a practical solution to the problem of integrating loose powdered materials into an on-board hydrogen storage system. / CSIR Young Researchers Establishment Fund (YREF)

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L'objectif de la thèse présentée ici est l'optimisation de matériaux carbonésnanoporeux au moyen de la “conception de matériaux virtuels”. En ce qui concerne cette échelle de travail (~ 10nm), la Nanotomographie FIB-SEM est la seule technique d'imagerie donnant accès à une information sur la géométrie tridimensionnelle. Cependant, pour l'optimisation du comportement, l'espace des pores doit être reconstruit à partir des données tirées des images obtenues. Jusqu'à présent ce problème n'était pas résolu. Pour pouvoir le maîtriser, on a développé une simulation d'images FIB-SEM. Les images FIB-SEM simulées peuvent être utilisées pour la vérification et la validation des algorithmes de segmentation. En utilisant les données d'image simulées, un nouvel algorithme pour la reconstruction de l'espace des pores à partir des données FIB-SEM a été développé.Deux études de cas avec des carbones nanoporeux utilisés pour le stockage d'énergie sont présentées, en utilisant les nouvelles techniques pour la caractérisation et l'optimisation des électrodes Li-ion de type EDLC'S (« electric double-layer capacitors », soit supercondensateurs). L'espace des pores reconstruit est modélisé géométriquement à l'aide de la géométrie stochastique. Enfin, on a simulé les propriétés électriques des matériaux enutilisant des structures modélisées et simulées. / The aim of the work presented here is to optimize nanoporous carbon materials by means of 'virtual material design'. On this length scale (~ 10nm) Focused Ion Beam – Scanning Electron Microscopy Nanotomography (FIB-SEM) is the only imaging technique providing three dimensional geometric information. Yet, for the optimization, the pore space of the materials must be reconstructed from the resulting image data, which was a generally unsolved problem so far.To overcome this problem, a simulation method for FIB-SEM images was developed. The resulting synthetic FIB-SEM images could then be used to test and validate segmentation algorithms. Using simulated image data, a new algorithm for the morphological segmentation of the highly porous structures from FIB-SEM data was developed, enabling the reconstruction of the three dimensional pore space from FIB-SEM images.Two case studies with nanoporous carbons used for energy storage are presented, using the new techniques for the characterization and optimization of electrodes of Li-ion batteries and electric double layer capacitors (EDLC's), respectively. The reconstructed pore space is modeled geometrically by means of stochastic geometry. Finally, the electrical properties of the materials were simulated using both imaged real and modeled structures.

Activated carbons as emerging classes of porous materials have gained tremendous attention because of their versatile applications such as gas storage/separations sorbents, oxygen reduction reaction (ORR) catalysts and supercapacitor electrodes. This diversity originates from fascinating features such as low-cost, lightweight, thermal, chemical and physical stability as well as adjustable textural properties. More interestingly, sole heteroatom or combinations of various elements can be doped into their framework to modify the surface chemistry. Among all dopants, nitrogen as the most frequently used element, induces basicity and charge delocalization into the carbon network and enhances selective adsorption of CO2. Transformation of a task-specific and single source precursor to heteroatom-doped carbon through a one-step activation process is considered a novel and efficient strategy. With these considerations in mind, we developed multiple series of heteroatom doped porous carbons by using nitrogen containing carbon precursors. Benzimidazole-linked polymers (BILP-5), benzimidazole monomer (BI) and azo-linked polymers (ALP-6) were successfully transformed into heteroatom-doped carbons through chemical activation by potassium hydroxide. Alternative activation by zinc chloride and direct heating was also applied to ALP-6. The controlled activation/carbonization process afforded diverse textural properties, adjustable heteroatom doping levels and remarkable gas sorption properties. Nitrogen isotherms at 77 K revealed that micropores dominate the porous structure of carbons. The highest Brunauer-Emett-Teller (BET) surface area (4171 m2 g-1) and pore volume (2.3 cm3 g-1) were obtained for carbon synthesized by KOH activation of BI at 700 °C. In light of the synergistic effect of basic heteroatoms and fine micropores, all carbons exhibit remarkable gas capture and selectivity. Particularly, BI and BIPL-5 derived carbons feature unprecedented CO2 uptakes of 6.2 mmol g-1 (1 bar) and 2.1 mmol g-1 (0.15 bar) at 298 K, respectively. The ALP-6 derived carbons retained considerable amount of nitrogen dopants (up to 14.4 wt%) after heat treatment owing to the presence of more stable nitrogen-nitrogen bonds compared to nitrogen-carbon bonds in BILP-5 and BI precursors. Subsequently, the highest selectivity of 62 for CO2/N2 and 11 for CO2/CH4 were obtained at 298 K for a carbon prepared by KOH activation of ALP-6 at 500 °C.

No presente trabalho de pesquisa foram analisadas diferentes estratÃgias avaliativas com vistas à anÃlise da aprendizagem escolar em quÃmica orgÃnica, especificamente dos conteÃdos: propriedades e classificaÃÃo dos carbonos, classificaÃÃo das cadeias carbÃnicas, nomenclatura de compostos orgÃnicos e isomeria. AtravÃs de anÃlises quantitativas e qualitativas foi possÃvel aplicar diversificados mÃtodos avaliativos. Entre os mÃtodos analisados de avaliaÃÃo geralmente utilizados no ensino mÃdio destacam-se as provas com questÃes de mÃltipla escolha e com questÃes abertas. A aplicaÃÃo dessas metodologias representam uma anÃlise coerente da aprendizagem dos conteÃdos curriculares estabelecidos pelas Diretrizes Curriculares Nacionais do Ensino MÃdio, pois o estudante deve apresentar conhecimentos prÃvios acerca das temÃticas, alÃm de estimular o estudo prÃvio. Utilizou-se a dramatizaÃÃo sobre temÃticas da quÃmica orgÃnica, como as funÃÃes orgÃnicas e quÃmica ambiental, nos quais, os estudantes participantes da pesquisa expressaram-se atravÃs de peÃas teatrais utilizando as artes cÃnicas como forma de expressÃo, alÃm de representarem os efeitos nocivos das drogas e relacionÃ-los com o conhecimento curricular das funÃÃes aminas. Todas as apresentaÃÃes foram documentadas em vÃdeo para anÃlises posteriores. Foi proposto tambÃm a utilizaÃÃo de seminÃrios como procedimento avaliativo, onde os educandos puderam expressar temÃticas diferenciadas divididas em grupos. Os alunos tambÃm realizaram a criaÃÃo de histÃrias em quadrinhos sobre assuntos da quÃmica orgÃnica, anÃlises das disposiÃÃes das falas e sua relaÃÃo com o tema proposto e a consistÃncia do conhecimento quÃmico foram os critÃrios fundamentais que foram elencados para atribuiÃÃo de notas. Em cada mÃtodo de exame, foi realizado um levantamento das notas obtidas em cada procedimento avaliativo. Percebe-se que a avaliaÃÃo da aprendizagem ultrapassa a simples atribuiÃÃo de notas ao desempenho dos estudantes, pois nem sempre os valores atribuÃdos repercutem em efetiva aprendizagem. A produÃÃo textual tambÃm foi uma metodologia de avaliaÃÃo aplicada aos estudantes da turma pesquisada. Foi proposto que eles elaborassem um relatÃrio de prÃticas sobre o estudo dos Ãsteres e sua reaÃÃo com hipoclorito de sÃdio. Logo apÃs a experiÃncia realizada no laboratÃrio interdisciplinar de ciÃncias da escola, foi proposto aos educandos a elaboraÃÃo individual de um relatÃrio da prÃtica e feita uma anÃlise de aspectos como a escrita sobre o tema e anÃlise dos resultados e discussÃes com os elementos inerentes a metodologia cientÃfica. / In this research work were analyzed different evaluative strategies for the assessment of school learning in organic chemistry, specifically the contents: properties and classification of carbon, classification of carbon chains, naming organic compounds and isomerism. Through quantitative and qualitative analysis it was possible to apply diverse evaluation methods. Among the methods analyzed evaluation generally used in high school there are the tests with multiple choice questions and open questions. The application of these methodologies represent a coherent analysis of learning curricula established by the National Curriculum Guidelines for Secondary Education, for the student must submit prior knowledge of the subject, besides stimulating the previous study. We used the drama on topics of organic chemistry, such as bodily functions and environmental chemistry, in which the survey participants-students expressed through plays using the performing arts as a means of expression, besides representing the harmful effects of drugs and relate them to the curricular knowledge of amine functions. All presentations were documented on video for later analysis. It was also proposed the use of seminars as evaluation procedure where the students could express different themes divided into groups. Students also made the creation of comic books on subjects of organic chemistry, analysis of the provisions of the talks and their relation to the theme and the consistency of the chemical knowledge were the key criteria that were listed for grading. In each test method, a survey was conducted of the marks obtained in each evaluation procedure. It is noticed that the assessment of learning goes beyond simply assigning grades to student performance, because not always the assigned values resonate with effective learning. The text production was also a valuation methodology applied to students of the searched class. It was proposed that they prepare a report on the practical study of esters and their reaction with sodium hypochlorite. Soon after the experiment conducted in the interdisciplinary lab school science, it was proposed to students the individual elaboration of a practice report and an analysis of aspects such as writing on the subject and analyzing the results and discussions with inherent scientific methodology elements.