abstract: The applications utilizing nanoparticles have grown in both industrial and academic areas because of the very large surface area to volume ratios of these particles. One of the best ways to process and control these nanoparticles is fluidization. In this work, a new microjet and vibration assisted (MVA) fluidized bed system was developed in order to fluidize nanoparticles. The system was tested and the parameters optimized using two commercially available TiO2 nanoparticles: P25 and P90. The fluidization quality was assessed by determining the non-dimensional bed height as well as the non-dimensional pressure drop. The non-dimensional bed height for the nanosized TiO2 in the MVA system optimized at about 5 and 7 for P25 and P90 TiO2, respectively, at a resonance frequency of 50 Hz. The non-dimensional pressure drop was also determined and showed that the MVA system exhibited a lower minimum fluidization velocity for both of the TiO2 types as compared to fluidization that employed only vibration assistance. Additional experiments were performed with the MVA to characterize the synergistic effects of vibrational intensity and gas velocity on the TiO2 P25 and P90 fluidized bed heights. Mathematical relationships were developed to correlate vibrational intensity, gas velocity, and fluidized bed height in the MVA. The non-dimensional bed height in the MVA system is comparable to previously published P25 TiO2 fluidization work that employed an alcohol in order to minimize the electrostatic attractions within the bed. However, the MVA system achieved similar results without the addition of a chemical, thereby expanding the potential chemical reaction engineering and environmental remediation opportunities for fluidized nanoparticle systems. In order to aid future scaling up of the MVA process, the agglomerate size distribution in the MVA system was predicted by utilizing a force balance model coupled with a two-fluid model (TFM) simulation. The particle agglomerate size that was predicted using the computer simulation was validated with experimental data and found to be in good agreement. Lastly, in order to demonstrate the utility of the MVA system in an air revitalization application, the capture of CO2 was examined. CO2 breakthrough time and adsorption capacities were tested in the MVA system and compared to a vibrating fluidized bed (VFB) system. Experimental results showed that the improved fluidity in the MVA system enhanced CO2 adsorption capacity. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2019

As mankind attempts to halt climate change and global warming, large-scale carbon dioxide (CO2) capture, utilization and storage (CCUS) technologies are viewed as an indispensable approach to curb CO2 emission. This thesis focused on better understanding CO2-amine interactions during adsorption, while developing in parallel covalently immobilized polyethylenimine (PEI) adsorbents for CO2 adsorption. In addition, catalyst reusability issues reported in the synthesis of cyclic carbonates (CCs) from CO2 and epoxides using metal-free supported immobilized quaternary ammonium salts are addressed, while developing new organosilicas for the synthesis of CCs. The reaction between CO2 and amine was investigated at the gas-solid interface in an attempt to provide a unified CO2-amine interaction both in adsorption and absorption. A combination of density functional theory calculations and experimental data (FTIR and 13C NMR) showed that the formation of the zwitterion intermediate often reported in the literature is highly unlikely, instead a six-atom centered zwitterion mechanism involving the “assisting” effect of water, amine or other functional groups was found to be more feasible due to its lower activation energy. Moreover, evidence was provided to suggest that under humid conditions, bicarbonate and carbonate are formed from the reaction between water and CO2, and not the widely reported carbamate hydrolysis. With a goal of minimizing the leaching of amines on PEI-impregnated adsorbents, PEI was covalently immobilized on mesoporous aluminosilica using 3-glycidoxypropyltrimethoxysilane or 3-triethoxysilylpropyl isocyanate as linkers. The resultant materials were found to be more resistant to leaching (in ethanol) and degradation (air at 100 oC) compared to their impregnated counterparts. Further enhancement in oxidation stability was achieved by covalently grafting epoxide-functionalized PEI onto mesoporous aluminosilica. CO2 uptake over amine-containing adsorbents is widely reported to be enhanced in the presence of moisture. However, the same cannot be said for other adsorbents, such as, carbonaceous and zeolite-based materials, and most MOFs. In a soon to be submitted review manuscript, a comprehensive analysis on the role of water on CO2 uptake (equilibrium and kinetics), material structure and regeneration over a wide range of adsorbents is presented. As for CO2-epoxides fixation to cyclic carbonates, a quaternary ammonium salt supported on SBA-15 was used to investigate the observed literature trend between product yield and substrate type with catalyst reuse. Under mild reaction conditions (1.0 MPa CO2, 100 oC and 4 h), 1,2-butylene carbonate was obtained in high yields (> 95%) over 5 cycles as the substrate is easy to activate and the product can be completely removed from the catalyst surface due to its low boiling point. Nonetheless, using styrene oxide led to decrease in yield over reuse cycles, mainly because styrene carbonate crystals were trapped on the catalysts surface (13C MAS NMR and TGA data), thereby blocking access to active sites. By extensively washing all spent catalysts in acetone and using chromatographic grade SiO2 as support material, styrene carbonate was obtained in very good yield (> 93%) over five cycles. Finally, novel quaternary ammonium iodide-based organosilicas, grouped into disordered, ordered and periodic mesoporous organosilicas, were prepared and tested for the cycloaddition of CO2 to epoxide to yield cyclic carbonates. Under mild reaction conditions (0.5 MPa CO2, 50 oC and 10 – 15 h) catalysts with the ordered mesoporous organosilicas structure were found to be more active owing to their larger surface area and pore volume, enhancing the accessibility of active sites by epoxides.

The overall objective of this thesis is to evaluate the fundamentals of current low concentration CO2 separation technologies and to provide an alternate method using adsorption technology with existing as well as new adsorbents. Two different applications for the adsorption of CO2 are explored; Direct Air Capture (DAC) and excimer gas purification. The investigation of aerogels as possible adsorbent for these applications was also explored. The first application, DAC of CO2 using adsorbents, addresses climate change by reducing the amount of atmospheric CO2 levels that are directly correlated to global warming. Because of DAC being carbon negative, this field has gained significant attention in the literature. DAC as a CO2 reduction strategy was approached in two ways: 1. Chapter 2 investigates capturing and concentrating CO2 from 0.04% in the air to 95% to be able to sequester it into the ground. This research began by doing an adsorbent selection using pure gas gravimetric measurements on seven different commercially available type X zeolites that were determined to have potential for this separation. Breakthrough experiments were then carried out with the most promising zeolite by perturbing the bed with compressed ambient air. In the process studied, a basic four step temperature vacuum swing adsorption (TVSA) cycle was investigated comprising the following steps: pressurization, adsorption, blowdown, and desorption. Four different regeneration temperatures were tested along with four different gas space velocities. With this cycle configuration, CO2 was concentrated to 95% from 0.04% with total capture fractions as high as 81%. This study highlighted methods to reduce the energy consumption per ton of CO2 captured in the system as well as the potential of using low Si/Al ratio faujasite structured zeolites in DAC of CO2 for greenhouse gas reduction. 2. Chapter 3 expands on the research of Chapter 2 by capturing CO2 from 0.04% in the air and concentrating it to high purity CO2 levels where the cost for operating the process will be reimbursed through the value of the produced CO2. The goal of this research was to increase the CO2 to as high as possible because the purer the CO2, the more valuable it is. This research started by conducting an in-depth investigation into the pure gas adsorption of CO2, N2, O2, and Ar on the most promising zeolite from Chapter 2. The data was then fitted to the TD-Toth model which allowed for the evaluation of the TVSA cycle and showed the potential of reducing the pressure and/or elevating the temperature during the blowdown step in order to produce high purity CO2. To confirm this, the TVSA cycle was run on a fixed bed breakthrough experiment where high purity CO2 was produced between a concentration of 99.5% and 99.96% by lowering the blowdown pressure. By controlling the blowdown temperature, the concentration of the product was increased from 99.8% to 99.95%, however with a significant loss of CO2. This effect of N2, O2, and Ar desorbing during the blowdown step with CO2 desorbing during the evacuation step is shown graphically by measuring the concentration and flow rate of the exiting gas species. The results from this study show the potential for producing a valuable product of high purity CO2 from atmospheric concentrations. The second application in this thesis that is explored in Chapter 4 is the purification of trace impurities of CO2, CF4, COF2, and O2 from F2, Kr, and Ne for applications in excimer lasers. Due to the incompatibility of many adsorbents to F2 and HF, aluminas and polymeric adsorbents were selected as potentially compatible materials. To increase the compatibility of these adsorbents, the use of a cryo-cooler was determined to be feasible to precool the feed stream before separation, which increases the adsorption capacity and compatibility of the material to F2 and HF. To determine the adsorption potential in the low concentration of these adsorbents, the concentration pulse chromatographic technique was chosen to determine the Henry’s Law constants of CO2, CF4, and O2. This data was then plotted on the van’t Hoff plot and extrapolated to colder temperatures to determine the benefit of using a cryo-cooler. From this study, it was determined that HayeSep Q was the best polymeric adsorbent with significant adsorption of CO2 at temperatures below -50˚C while being the best performing CF4 adsorbent. AA-300 was the best performing alumina in this study while having significant adsorption of CF4 at temperatures below -135˚C. However, from a compatibility standpoint, both of these materials need to be tested to determine their robustness in the presence of F2 and HF at room and reduced temperatures. Chapters 5 & 6 in this thesis explore the fundamentals of adsorption on aerogels as a prelude to using aerogels as possible adsorbents for DAC of CO2. This investigation into aerogels looks at silica aerogels and carbon aerogels, which are both industrially produced and explores their adsorption with relation to like materials such as silica gel and activated carbons. Both of these Chapters utilize experimentally determined adsorption isotherms of CO2, N2, O2, and Ar as well as characterization to determine adsorption trends in the materials. Some major conclusions for silica aerogels were that common surface modifications to make the material more resilient against water adsorption impacts the adsorption of CO2 significantly with roughly 4 fold difference in adsorption capacity. For carbon aerogels some major conclusions were that the adsorption was increasingly dominated by the heterogeneous nature of the surface at lower pressures and increasingly dominated by the pore size at the higher pressures. Both chapters discuss the adsorption of air along with ideas such as the influence of gas thermal conductivity in the pores with respects to adsorption. L'objectif général de cette thèse est d'évaluer les principes fondamentaux des technologies actuelles de séparation du CO2 à faible concentration et de fournir une méthode alternative utilisant la technologie d’adsorption avec des adsorbants actuels ainsi que d'en découvrir de nouveaux. Deux applications différentes pour l'adsorption du CO2 ont été explorées; la capture directe dans l’air ambient (CAD) et la purification des gaz excimères, ainsi que la recherche d'aérogels comme adsorbant possible pour ces applications. La première application, le CAD du CO2 utilisant des adsorbants, pourrait répondre aux changements climatiques puisque les niveaux de CO2 atmosphérique sont directement corrélés au réchauffement climatique. Dernièrement, le CAD a fait l'objet d'une attention particulière en tant que stratégie de réduction du CO2, par conséquent, deux voies différentes ont été explorées dans cette thèse: 1. Le chapitre 2 étudie la capture et la concentration du CO2 de 0,04% dans l'air à 95% afin de pouvoir l’enfermer dans la terre. Pour ce faire, une sélection d'adsorbant a été effectué en utilisant des mesures gravimétriques à gaz pur sur sept zéolithes de type X disponibles dans le commerce qui ont été déterminés comme ayant un potentiel pour cette séparation. Des expériences révolutionnaires ont ensuite été réalisées avec la zéolite la plus prometteuse en perturbant le lit avec de l'air ambiant comprimé. Dans le processus étudié, un cycle basique à quatre étapes d’adsorption modulée en température et pression (AMTP) a été étudié, comprenant les étapes suivantes: pressurisation, adsorption, purge et désorption. Quatre températures de régénération différentes ont été testées ainsi que quatre vitesses spatiales de gaz différents. Avec cette configuration de cycle, le CO2 était concentré à 95% de 0,04% avec des fractions de capture totales aussi élevées que 81%. Cette étude a mis en évidence des méthodes pour réduire la consommation d'énergie par tonne de CO2 captée dans le système ainsi que le potentiel d'utilisation de zéolithes structurées à base de faujasite à faible rapport Si/Al dans le CAD du CO2 pour la réduction des gaz à effet de serre. 2. Le chapitre 3 approfondit les recherches du chapitre 2 en capturant le CO2 de 0,04% dans l'air et en le concentrant à des niveaux de très haute pureté où le processus sera remboursé par la valeur du CO2 produit. L'objectif de cette partie était d'augmenter la pureté du CO2 le plus possible car plus le CO2 est pur, plus il est précieux. Une enquête approfondie sur l'adsorption de gaz pur de CO2, N2, O2 et Ar sur la zéolite la plus prometteuse du chapitre 2. Les données ont ensuite été ajustées au modèle TD-Toth qui a permis d'évaluer le cycle AMTP et a montré le potentiel de réduire la pression et/ou d'élever la température pendant l'étape de purge afin de produire du CO2 de haute pureté. Pour confirmer cela, le cycle AMTP a été fait par le biais d’une expérience dans un lit fixe où du CO2 de haute pureté a été produit entre une concentration de 99,5% et 99,96% en abaissant la pression de purge. En contrôlant la température de purge, la concentration du produit est passée de 99,8% à 99,95%, mais avec une perte importante de CO2. Cet effet de la désorption de N2, O2 et Ar pendant l'étape de purge avec la désorption du CO2 pendant l'étape d'évacuation est illustré graphiquement en mesurant la concentration et le débit des espèces de gaz sortant. Les résultats de cette étude montrent le potentiel de production d'un produit précieux de CO2 de haute pureté à partir des concentrations atmosphériques. La deuxième application de cette thèse qui est explorée au Chapitre 4 est la purification des traces d'impuretés de CO2, CF4, COF2 et O2 de F2, Kr et Ne pour des applications dans les lasers à excimère. En raison de l'incompatibilité de nombreux adsorbants avec le F2 et le HF, les alumines et les adsorbants polymères ont été sélectionnés comme matériaux potentiellement compatibles. Pour augmenter la compatibilité de ces adsorbants, l'utilisation d'un cryoréfrigérant a été jugée possible pour pré-refroidir le flux d'alimentation avant la séparation, ce qui augmente la capacité d'adsorption et la compatibilité du matériau en F2 et HF. Pour déterminer le potentiel d'adsorption dans la faible concentration de ces adsorbants, la technique de chromatographie pulsée de concentration a été choisie pour déterminer les constantes de la loi de Henry de CO2, CF4 et O2. Ces données ont ensuite été tracées sur le graphique van’t Hoff et extrapolées à des températures plus froides pour déterminer les avantages de l’utilisation d’un cryoréfrigérant. À partir de cette étude, il a été déterminé que HayeSep Q était le meilleur adsorbant polymère avec une adsorption significative de CO2 à des températures inférieures à -50 ° C tout en étant l'adsorbant CF4 le plus performant. L'AA-300 était l'alumine la plus performante de cette étude tout en ayant une adsorption significative de CF4 à des températures inférieures à -135 °C. Cependant, du point de vue de la compatibilité, ces deux matériaux doivent être testés pour déterminer leur robustesse en présence de F2 et de HF à température ambiante et réduite. Les chapitres 5 et 6 explorent les principes fondamentaux de l'adsorption sur les aérogels en prélude à l'utilisation d'aérogels comme adsorbants possibles pour le CAD du CO2. Cette enquête sur les aérogels examine les aérogels de silice et les aérogels de carbone, qui sont tous les deux fabriqués industriellement et explore leur adsorption par rapport à des matériaux similaires tels que le gel de silice et les charbons actifs. Ces deux chapitres utilisent des isothermes d'adsorption déterminés expérimentalement de CO2, N2, O2 et Ar ainsi que la caractérisation pour déterminer les tendances d'adsorption dans les matériaux. Certaines conclusions majeures pour les aérogels de silice étaient que les modifications de surface courantes pour rendre le matériau plus résistant à l'adsorption d'eau ont un impact significatif sur l'adsorption de CO2 avec une différence d'environ 4 fois dans la capacité d'adsorption. Pour les aérogels de carbone, certaines conclusions majeures étaient que l'adsorption était de plus en plus dominée par la nature hétérogène de la surface à des pressions plus faibles et de plus en plus dominée par la taille des pores aux pressions plus élevées. Les deux chapitres discutent de l'adsorption d'air ainsi que des idées telles que l'influence de la conductivité thermique du gaz dans les pores en ce qui concerne l'adsorption.

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Internal combustion engines (ICEs) are essential for the welfare of today’s human civilization yet they contribute to almost 10% of the global CO2 emissions. Reducing the carbon footprint of the ICEs can be achieved by either increasing the engine efficiency to reduce fuel consumption or the utilization of carbon-neutral fuels. This dissertation aims to investigate the effect of the oxidizer composition on the efficiency and performance of the homogenous charge compression ignition (HCCI) engine. It also aims to study the behavior of hydrogen in HCCI engines. The experiments are conducted using a Cooperative Fuel Research (CFR) engine. The study also involves using chemical kinetics simulations to estimate the ignition delay time of hydrogen which is relevant to the HCCI mode of combustion. The results suggest that the specific heat ratio of the oxidizer does not significantly affect the HCCI engine efficiency. On the fuel side, hydrogen showed high sensitivity to engine running conditions due to the lack of negative temperature coefficient (NTC).

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This work presents a techno-economic analysis of multiple direct hydrogen production technologies using different blends of Arabian crude oil and natural gas as feedstock: Auto thermal reforming, steam reforming, and combined reforming technologies are thermodynamically and technically evaluated through development of process flowsheets. Comparative analysis indicates that combined reforming using Arabian light crude oil achieves a 22.69 % of hydrogen recovery with carbon capture, which is higher than auto thermal reforming and steam reforming by 0.7 %. At the same time, auto thermal reforming achieves a 26.70 % of hydrogen recovery without carbon capture, which is higher than steam reforming and combined reforming by 4 %. Arabian heavy, medium, light, and extra light are evaluated using auto thermal reforming technology to estimate hydrogen recovery values. A wide range of crude oil and natural gas prices are included in the analysis to calculate hydrogen production cost. With crude oil price at 90 USD/bb, the hydrogen production cost is 2.9 USD/kg, and natural gas prices at 30 USD/MMBtu (Europe), 20 USD/MMBtu (Japan), and 2.5 USD/MMBtu (GCC region), the hydrogen production cost is 4.5, 3.0, and 0.4 USD/kg respectively.

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