Aziridines and cyclopropanes are valued as important building blocks for the synthesis of a wide range of organic compounds, including biologically active compounds and pharmaceuticals. The development for more efficient and cost-effective catalysts for the atom transfer reaction with olefins is a continuing area of research in both organic and inorganic chemistry. Transition metal complexes, which catalyze reactions of olefins with nitrenes and carbenes, are well-developed efficient, approaches to the direct synthesis of aziridines and cyclopropanes, but traditionally rely on expensive synthetic methods. As part of our efforts in the catalytic formation of C—C and C—N bonds, herein we show the development of a new and efficient copper(II) catalysts that exhibits high reactivity forming cyclopropanes and aziridines from a range of olefins. These catalytic systems have also shown a propensity to conduct these atom-transfer reactions in aqueous solutions, affording the opportunity to use bio-macromolecules, like DNA, to induce enantioselectivity.

Organometallic allylation for the formation of C-C bonds has been a widely developed area over the past several decades for the formation of homoallylic alcohols and amines. One such pathway, the eponymous Hosomi-Sakurai reaction involves the Lewis acid-catalyzed addition of an allylic silane to an acetal, carbonyl, or imine. This work demonstrates an example of a Hosomi-Sakurai reaction using 1,2-ditosyl diazetidine as a slow release formaldimine precursor with good yield and high selectivity. Another less classical field, C-H activation, has also been around for several decades, but has recently exploded in new innovations. Through C-H activation chemists are able to bypass the need for functional groups that are substituted out, but instead utilizes the C-H bond as a synthon for further functionalization. This work will also demonstrate a modular approach for the synthesis of several ruthenium complexes with the potential to catalyze C-H activation.

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The preparation method of the catalyst highly impacts its properties and activity. Optimizing the synthesis conditions mainly targets improving the catalyst performance and overcoming the bottlenecks such as sintering of metal active sites, deactivation, short catalyst lifetime and poor selectivity. In this study, we investigated the influence of the design and preparation method of Silicalite-1 bearing Pt and Ga active species on the properties and the performance of the catalysts for propane dehydrogenation reaction aiming to increase propylene yield. Various synthesis routes, leading to different Pt and Ga location and distances were tested: (1) supporting metals on the zeolite where both Pt and Ga are randomly distributed on the surface, (2) confining of Pt and Ga within the zeolite pores following in-situ approach with no control of their relative positions, and (3) core-shell design where one metal is confined within Silicalite-1 is covered by a Silicalite-1 layer including the second metal. The influence of structure, textural properties, location of Pt and Ga nanoparticles and their synergetic interaction to form Pt-Ga alloys were studied using several characterization techniques such as XRD, BET, TEM-EDX and NMR. Catalytic performance revealed that confining metals improved the selectivity and lifetime of the catalyst. Moreover, spatial separation of Pt and Ga through the core-shell design further boosted the reaction yield with conversions hitting the equilibrium limit. Ga/Pt ratio played a crucial role in tuning the catalyst performance. 0.26%Pt(core)-2.65%Ga(shell)@S-1 catalyst with Ga/Pt of 10 exhibited superior results of 70.5% conversion and 98% selectivity.

The conversion of methane into valuable chemicals remains one of the major challenges in catalysis science. Both academia and industry are showing keen interest in developing direct one-step catalytic processes in contrast to the existing indirect technologies based on syngas (i.e., Fischer-Tropsch, Methanol-to-Hydrocarbons) that are highly energy-intensive and require high capital investment for the syngas preparation-compression units. Therefore, methane dehydroaromatization (MDA) catalysis on transition metal (i.e., Mo, W, Fe, V) loaded zeolites (i.e., ZSM-5, MCM-41, TNU-9) is still being studied by many researchers, as this process is considered to be one of the most promising alternatives despite the thermodynamic limitations and rapid catalyst deactivation. To develop stable catalysts and commercialize this process, one needs to understand the fundamentals of the reaction and investigate the possible process enhancement options. For instance, although several studies proposed the bifunctional pathway (CH4 coupling on activated Mo sites and oligomerization on Brønsted acids), the details of the mechanism are still ambiguous. Besides, there are options like H2O co-addition to enhance the performance and stability of catalysts against high coke deposition rates. However, a proper structure-function relationship during co-feeding was lacking in previously reported works. Furthermore, there can be alternative metals that may replace Mo. For example, tungsten oxides having similar chemical features with molybdenum oxides are thermally more stable; they can persist even during high-temperature air regeneration. However, W-supported catalysts cannot reach the activity levels that those based on Mo display. This performance difference between W and Mo should be investigated to improve the catalytic performance of W/ZSM-5. Also, the utilization of hierarchical zeolites in MDA catalysis has received a great deal of attention in the last two decades, since they have a great potential to help in improving catalysis performance and overall lifetime. However, when literature survey is done regarding this topic, it would be seen that there is a great inconsistency in many aspects (type of hierarchy, process performance, catalyst deactivation etc.) among the previous studies. Therefore, the hierarchical zeolite applications in MDA reactions should be revisited, and a more detailed discussions should be presented to catalysis community. Considering all these, we have developed new strategies to study MDA. First, we investigated the initial C-C bond formation mechanism during the early stages of MDA by applying “mobility-dependent” advanced ssNMR techniques on labeled methane (13CH4) treated Mo/ZSM-5 catalyst. We identified two mechanisms (mono- and bi-functional) leading to an initial C-C bond based on the detected species. Moreover, we elucidated the effects of H2O co-feeding over Mo/ZSM-5 by employing a battery of advanced characterization techniques. It has been found that water does not change the initial C-C bond formation mechanism but results in steam reforming reaction proceeding parallel to MDA. Also, we investigated W/ZSM-5 catalyst for MDA with a different perspective. The experiments conducted indicate that enhanced catalytic performance might be achieved if the dispersion and distribution of W sites on ZSM-5 can be tuned. Lastly, we revisited the hierarchical zeolite application in MDA catalysis. After analyzing our experimental results and the previous studies, a detailed discussion was presented to give some directions to those interested in hierarchy in zeolites.

The Caradonna lab has utilized the enzyme active site of TauD as a model for a synthetic, metal-based, oxidative catalyst. We have developed a series of small molecule, non-heme, manganese catalysts that are analogous to the previously synthesized iron complexes in our lab. These complexes, denoted MnII(N2Ox), where x = 1–3, were spectroscopically characterized, and their scope of utility explored. In addition to oxidizing methanol to formaldehyde, each catalyst in the series has exhibited the ability to epoxidize alkene substrates, including cyclooctene, cyclohexene, and cis-stilbene. After reaction condition optimization, the reactivity studies revealed certain trends in the reactivity of each catalyst, and the range of TONs was 10-120. A heterogeneous catalyst system was also developed in which the iron catalyst was tethered onto a solid support. The iron catalyst, FeII(N2O1), where N2O1 is N-(2-(dimethylamino)ethyl)-N-methylglycine, is susceptible to dimerization and subsequent inactivation when it is in homogeneous solution. Thus, a homogeneous catalyst system was designed with a resin that contained a low concentration of amine functionalization, which was synthetically transformed into an azide-functionalized resin. An alkyne derivative of the N2O1 ligand scaffold was developed which could then be tethered onto the resin via CuAAC “click” chemistry, and low-loading levels of tethered catalyst were obtained. Efforts towards modulating the N2O1 ligand were also explored. We sought to develop a synthetic methodology for facile ligand functionalization, which would provide greater accessibility to adding desired substituents. These substituents could aid in the solubility of the catalyst or provide ligand-directed asymmetric catalysis for prochiral substrates. The ligand was also modified electronically with electron-withdrawing and electron-donating substituents, in order to probe how the electronic structure of the catalyst affects its reactivity. Finally, efforts were made toward spectroscopically establishing the structure of the Fe(IV)-oxo intermediate with isotopically labeled reagents. The development of the manganese-based oxidative complexes and the optimization efforts towards the O2-activating iron-based complexes have exploited the utility of biomimetic, small molecule catalysis.

Climate change, industrial and agricultural activities, and population growth exacerbate global water stress. A variety of advanced technologies have been studied to alleviate water scarcity and water pollution. Membrane technology owing to its low footprints and ease of operation, has drawn intensive attention for water purification and wastewater treatment. Further, integrating membrane technology, electrochemistry and catalysis can improve separation and selectivity of the filtration process. This work aims to fabricate high-performance active and reactive ultrafiltration membranes involving electrically conductive membranes, catalytic membranes and electrocatalytic membranes. Their use in water treatment inspires the development of advanced functionalized membranes and further accelerates the transition to industrial applications. / Thesis / Doctor of Engineering (DEng)

Biodiesel has come to the forefront of the energy community as a clean-burning, renewable energy that can replace the use of No. 2 Diesel fuel. Tall oil fatty acids, a by-product of the pulp and paper industry, may be utilized as a biodiesel feedstock. This thesis presents an empirical study of the acid-catalyzed esterification of tall oil fatty acids into biodiesel. Under atmospheric conditions, factorial design analysis determined the optimum parameters to be methanol ratio (6:1), sulfuric acid (5%), and temperature (60oC). This reaction was tolerant to water up to 1%. A pseudo-homogeneous second order kinetic model was applied to the reaction at the optimal conditions. The Activation Energy was calculated to be 19.73 kJ/mol with a pre-exponential factor of 23.6. Quality tests were performed under ASTM D 6751-06 to evaluate the final product with tall oil methyl esters having exceptional cold flow properties with a cloud point of -10.7oC.