Master of Science / Department of Biological and Agricultural Engineering / Zifei Liu / This study reviewed state-of-the-art cattle enteric methane (CH4) emissions with three reported measuring units: g/head/d, g/kg DMI (dry matter intake), and %GEI (gross energy intake). Cattle emissions studies included in this meta-analysis were reported from 1995 to 2013. Fifty-five published studies were analyzed with specific objectives: (1) to gain basic information regarding magnitudes and distributions of enteric CH4 emission rates with various units, regions, cattle types and feed situations; (2) to identify and evaluate effects of influence factors or diet mitigation techniques on enteric CH4 emissions; and (3) to evaluate Intergovernmental Panel on Climate Change (IPCC) approaches to estimate enteric CH4 emissions. Emissions data (n=165) with the unit of g/head/d had large variances and non-normal distribution, and were not homogeneous across the studies. Emissions data (n=134) with the unit of g/kg DMI were not homogeneous across the studies, while emissions data (n=76) with the unit of %GEI had small variances and normal distribution, and were homogeneous across the studies. Therefore, data with the unit of %GEI may be better for meta-analysis compared to data with the units of g/head/d and g/kg DMI; however, the number of data with the unit of %GEI was small relative to the number of data with the units of g/head/d and g/kg DMI. Enteric CH4 emissions with the unit of g/head/d are significantly influenced by geographic region, cattle classification, sub-classification, humidity, temperature, body weight, and feed intake. Emissions and feed intake had a strong positive linear relationship with R2 of 0.75 (n=148). Emissions with the unit of g/kg DMI are significantly affected by humidity, body weight, and feed intake. The relationship between emissions and feed intake is positive. Emissions with the unit of %GEI are significantly associated with humidity, production stage, and body weight. IPCC Tier 1 and Tier 2 estimated emissions were approximate to most of the measured enteric CH4 emissions; however, the residuals were not normally distributed. Based on results from PRD method and paired t-tests, IPCC Tier 1 overestimated emissions in Asian studies, underestimated emissions in European studies for beef cattle, and underestimated emissions in Oceanian studies for dairy cattle. IPCC Tier 2 underestimated emissions in Asian studies for beef cattle. The underestimated emissions of IPCC Tier 2 in Asian studies might result from no consideration of effects from production stage and body weight.

En esta memoria de Tesis Doctoral queda demostrado que los residuos de petróleo son excelentes candidatos para el diseño y preparación de carbones nanoporosos de elevada área superficial y volumen de poros para ser utilizados en múltiples aplicaciones. No solo se han podido diseñar carbones capaces de capturar grandes cantidades de CO2, sino que también se han preparado carbones activados que demostraron resistencia mecánica al ser compactados y así ser capaces de almacenar grandes cantidades de metano. Además, han demostrado ser los materiales adsorbentes pioneros en la producción de hidrato de metano sintético para poder llevar a la práctica la tecnología “Gas Natural Solidificado (GNS)”, sistemas que fomentan la disminución de las emisiones de CO2 a la atmósfera y que ayudan a aliviar el calentamiento global.

This work aims to develop fundamental insights about the underlying surface and bulk chemical processes instrumental to the efficiency of chemical looping combustion (CLC). CLC, which uses a solid-state oxygen carrier (e.g., metal oxides) to drive hydrocarbon combustion, is a promising combustion alternative that minimizes byproduct formation and facilities capture of CO2. In this work, we compare the performance of different transition metal oxides, namely iron, copper, cobalt, manganese, and nickel oxides, as oxygen carriers in CLC using CH4 as the reducing agent. Experiments used a continuous flow reactor across temperatures ranging from 500 to 800 oC and feed flowrates from 12.5 to 250 h-1. In addition to monitoring size-, temperature- and flow rate-dependent performance trends for CH4 conversion to CO2, microscopic and spectroscopic techniques were used to investigate the solid-state mechanism of oxygen carrier reduction and the coupled surface chemical and bulk material processes influencing performance. Bulk (XRD) and surface (XPS) analysis reveal that oxygen carrier reduction can be generally represented by two models, the unreacted shrinking core model (USCM) and the nuclei growth model (NNGM). The reduction of some metal oxides can also proceed via a two-stage solid-state mechanism; for example, hematite reduction to magnetite follows USCM, while the subsequent reductions of magnetite to wustite and wustite to iron metal follow NNGM. Furthermore, our results reveal that minimizing the particle size promotes oxygen carrier performance, but only for metal oxides reduced according to the USCM, where metal oxide reduction initiates on the particle surface. In contrast, no benefit of decreasing particle size was observed for materials reduced according to the NNGM because the reaction initiates in the particle bulk, such that a more critical determinant of reactivity may be the available oxygen carrier volume rather than surface area. Beyond these fundamental insights, cycling experiments were also performed to provide more practical information about the effect of oxygen carrier particle size on their long-term performance in CLC applications.

Magnetic nanoparticles attract increasing attention because of their current and potential biomedical applications, such as, magnetically targeted and controlled drug delivery, magnetic hyperthermia and magnetic extraction. Increased magnetization can lead to improved performance in targeting and retention in drug delivery and a higher efficiency in biomaterials extraction. We reported an approach to synthesize iron contained magnetic nanoparticles with high magnetization and good oxidation resistibility by pyrolysis of iron pentacarbonyl (Fe(CO)[subscript 5]) in methane (CH[subscript 4]). Using the high reactivity of Fe nanoparticles, decomposition of CH[subscript 4] on the Fe nanoparticles leads to the formation of nanocrystalline iron carbides at a temperature below 260°C. Structural investigation indicated that the as-synthesized nanoparticles contained crystalline bcc Fe, iron carbides and spinel iron oxide. The Mössbauer and DSC results testified that the as-synthesized nanoparticle contained three crystalline iron carbide phases, which converted to Fe[subscript 3]C after a heat treatment. Surface analysis suggested that the as-synthesized and subsequently heated iron-iron carbide particles were coated by iron oxide, which originated from oxidization of surface Fe atoms. The heat-treated nanoparticles exhibited a magnetization of 160 emu/g, which is two times of that of currently used spinel iron oxide nanoparticles. After heating in an acidic solution with a pH value of 5 at 60°C for 20 h, the nanoparticles retained 90 percentage of the magnetization. / Singapore-MIT Alliance (SMA)

Partial oxidation of CH4, CO2 reforming of CH4, and oxidative CO2 reforming of CH4 to produce synthesis gas at 700°C over supported Ni catalysts have been studied. A Ni/Mg-Al catalyst was prepared by the solid phase crystallization (spc-) method starting from a hydrotalcite-type (HT) anionic precursor. From XRD analysis, only Ni0.5Mg2.5Al catalyst consists of the layered hydrotalcite-type structure; not Ni0.5Ca2.5Al and Ni/Al2O3 catalysts. By TPR test, the Ni0.5Mg2.5Al-HT catalyst requires a high reduction temperature than the Ni0.5Ca2.5Al catalyst. It implies that the Ni0.5Mg2.5Al-HT which has a layered structure shows the stronger interaction strength between the molecules. It might increase the resistance of coke formation on the surface of the catalyst. For the reaction tests, the Ni0.5Ca2.5Al showed the highest initial activity for synthesis gas production for all reactions; but, its activity was decreased quickly due to coke formation except during the partial oxidation of CH4. The Ni0.5Mg2.5Al-HT showed a relatively higher reactivity compared to the equilibrium level than Ni/Al2O3 catalyst; and it shows very stable reactivity than other catalysts. By TPO test, the Ni0.5Mg2.5Al-HT has the lower amount of coke formed during the reaction than the Ni0.5Ca2.5Al catalyst. It confirms that the Ni0.5Mg2.5Al-HT catalyst has stronger resistance to coke formation; and it leads to provide stable reactivity in any reforming conditions at high temperature. Therefore, the Ni0.5Mg2.5Al-HT catalyst was the most promising catalyst in terms of activity and stability for partial oxidation, CO2 reforming, and oxidative CO2 reforming of CH4. The Ni0.5Mg2.5Al-HT catalyst was used to investigate the CO2 reforming of CH4 kinetics. With increasing CH4 partial pressures at constant CO2 partial pressure, the rates of CH4 consumption were increased. However, with increasing CO2 partial pressure at constant CH4 partial pressure, CH4 consumption rates was increased at lower CO2 partial pressure, but turned to independent at higher CO2 partial pressure. When the partial pressure of H2 was increased, the CO formation rate was decreased; it confirmed that the reverse water-gas shift (RWGS) reaction was occurring during the CO2 reforming of CH4 reaction. In addition, the reaction kinetic expression was proposed when the CH4 dissociation step was considered as a rate-limiting step.

Thanks to the rapid development of variable production patterns of industries, many kinds of chemicals are used. But the chemicals usually come with dangers of causing fires, explosions, and harming people. In the past decade in Taiwan, these chemicals caused many serious industrial disasters. They happened not only in conventional industries but also in semiconductor and chemical industries. And most of them happened due to the leaking of flammable or toxic gases. In the situation of the outbreak of fires, explosions may occur, and they will generally bring about heat radiation, explosive pressure, and energy releasing. And all of these often harm the workers and the environment, and also bring great loss for the factories. In order to prevent the disasters, except for improving the protection and safety equipment, it¡¦s more important to realize how to use effective ways to reduce them. If the gas pipes pass through a densely populated area, when some toxic gas leaks, it will cause fatal dangers which result from the mixing of gas diffusion and air, the flow process of the mixture, concentration of CH4, and temperature distribution, or explosions. After that, some toxic gas with poisonous substances will be released, and it will turn out to be horrible consequences that are beyond our imagination. So it¡¦s really important to do research on gas leaking and gas diffusion. If gas-leaking simulation is applied on the analysis of the leaking of flammable gas and gas diffusion, it¡¦s much more possible to protect the workers from being hurt, keep public safety, and reduce the loss on the wealth of the society. The thesis focuses on building various hazard patterns of gas leaking, gas explosions, and chemicals, etc. From all of these, the initial conditions and the degrees of dangers will be revealed. In the thesis, numerical simulation is used to analyze the density, pressure, speed of the leaking gas and all the distributions in the flow field. The major analysis is about the effects of parameter and the display of concentration distribution, and hazard range.

Partial oxidation of CH4, CO2 reforming of CH4, and oxidative CO2 reforming of CH4 to produce synthesis gas at 700°C over supported Ni catalysts have been studied. A Ni/Mg-Al catalyst was prepared by the solid phase crystallization (spc-) method starting from a hydrotalcite-type (HT) anionic precursor. From XRD analysis, only Ni0.5Mg2.5Al catalyst consists of the layered hydrotalcite-type structure; not Ni0.5Ca2.5Al and Ni/Al2O3 catalysts. By TPR test, the Ni0.5Mg2.5Al-HT catalyst requires a high reduction temperature than the Ni0.5Ca2.5Al catalyst. It implies that the Ni0.5Mg2.5Al-HT which has a layered structure shows the stronger interaction strength between the molecules. It might increase the resistance of coke formation on the surface of the catalyst. For the reaction tests, the Ni0.5Ca2.5Al showed the highest initial activity for synthesis gas production for all reactions; but, its activity was decreased quickly due to coke formation except during the partial oxidation of CH4. The Ni0.5Mg2.5Al-HT showed a relatively higher reactivity compared to the equilibrium level than Ni/Al2O3 catalyst; and it shows very stable reactivity than other catalysts. By TPO test, the Ni0.5Mg2.5Al-HT has the lower amount of coke formed during the reaction than the Ni0.5Ca2.5Al catalyst. It confirms that the Ni0.5Mg2.5Al-HT catalyst has stronger resistance to coke formation; and it leads to provide stable reactivity in any reforming conditions at high temperature. Therefore, the Ni0.5Mg2.5Al-HT catalyst was the most promising catalyst in terms of activity and stability for partial oxidation, CO2 reforming, and oxidative CO2 reforming of CH4. The Ni0.5Mg2.5Al-HT catalyst was used to investigate the CO2 reforming of CH4 kinetics. With increasing CH4 partial pressures at constant CO2 partial pressure, the rates of CH4 consumption were increased. However, with increasing CO2 partial pressure at constant CH4 partial pressure, CH4 consumption rates was increased at lower CO2 partial pressure, but turned to independent at higher CO2 partial pressure. When the partial pressure of H2 was increased, the CO formation rate was decreased; it confirmed that the reverse water-gas shift (RWGS) reaction was occurring during the CO2 reforming of CH4 reaction. In addition, the reaction kinetic expression was proposed when the CH4 dissociation step was considered as a rate-limiting step.

Introduction High starting radioactivity is usually advantageous for producing radiopharmaceuticals with high specific radioactivity. However, the [11C]CH4 yields from N2-H2 gas target fall short from theoretical amounts, as calculated from the cross section for the well-known 14N(p,α)11C nuclear reaction1. The beneficial effect of increased target chamber temperature on [11C]CH4 yields has recently been brought forward by us2 and others3. In addition to the temperature effect, our attention has also been on the hydrogen content factor. This study intends to examine the N2-H2 target performance in a substantially larger target chamber and at higher temperatures than our setup before and compare the results to the existing data. Materials and Methods Aluminium bodied custom design target chamber is used in fixed 17 MeV proton beam irradiations. Target chamber is equipped with heating elements and cooling circuit for temperature control. In addition to the target chamber body temperature, the target gas loading pressure and irradiation current can be varied. The irradiation product is collected into an ad-sorbent trap that was immersed in a liquid argon cooling bath within a dose calibrator. Results and Conclusion Pursued data will show [11C]CH4 saturation yields (Ysat [GBq/µA]) at different irradiation and target parameters.

Forest rings are large features common in Ontario’s boreal forests that comprise circular topographic depressions in carbonate mineral soil that are filled with peat. This thesis documents differences in peat and soil chemistry along transects across the “Bean” and “Thorn North” rings, which are centered on accumulations of CH4 and H2S, respectively. Within the mineral soil, ring edges are characterized by strong negative anomalies in pH, ORP and carbonate, as well as positive anomalies of Al, Fe and Mn in the results of aqua regia and hydroxylamine-hydrochloride digestions. Within the peat, positive carbonate and pH anomalies are recorded. This antithetic relationship suggests vertical migration of carbonate species from clay to peat. An inverse relationship exists between ORP, versus redox inferred from aqua regia. Strong ORP lows occur where oxidized products show highest concentrations. This is interpreted to reflect the proliferation of autotrophic organisms occupying the strong redox gradient at the ring edge.

The effect of drainage and restoration on the ecology of different types of peatlands in the Šumava Mountains was investigated. The study was focused primarily on peat properties, vegetation dynamics, carbon gas fluxes and their linkages under the affected hydrological regimes.