Browsing by Subject "zeolite"

Now showing 1 - 3 of 3
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    Synthesis of Zeolite Nanosheets and Applications in Membranes and Adsorption Separation Processes
    (2016-05) Jeon, Mi Young
    In separation processes, desirable products with high purity are acquired at the expense of high energy cost procedures such as distillation. Alternative separation processes, such as zeolite membrane separation and adsorption processes, are promising to reduce the energy cost of production since zeolites can discriminate molecules on the basis of size/shape and functionality. Indeed, the high cost of zeolite membranes can be reduced by fabricating thin membranes with high throughput. High aspect ratio zeolite nanosheets can be used to fabricate zeolite membranes with high throughput on porous supports. To date, however, there is no published evidence that scientists have successfully achieved nanosheet synthesis under the direct hydrothermal treatment route. This dissertation documents a successful direct hydrothermal synthesis of zeolite nanosheets via seeded-growth—a process that leads to zeolite membranes that exhibit high performance on xylene isomer and butane isomer permeation. To the best knowledge, this is the first achievement to prepare zeolite nanosheets without complicated post treatment such as exfoliation and purification process (density gradient centrifugation). Extensive parametric studies are conducted in order to establish the optimal synthesis condition for high quality zeolite nanosheets. Additionally, in an effort to understand the mechanism of nanosheet formation, the sequential evolution of seed crystals into zeolite nanosheets is observed by time-resolved TEM imaging analysis. Keeping in mind that in the future polymers could be used to reduce the costs of membrane manufacture, the de-templation of MFI nanosheets without formation of aggregates is discussed in this dissertation. In addition to membrane applications, this dissertation probes the roles of hydrophobicity in ethanol adsorption when hydrophobic siliceous zeolites, and defective siliceous zeolite nanosheets with house-of-card architecture are provided as adsorbents. Vapor phase ethanol adsorption and aqueous phase ethanol adsorption are compared to investigate how water molecules affect ethanol adsorption onto siliceous zeolites in the aqueous phase.
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    Tunable Synthesis and Characterization of Oleo-Furan Sulfonate Surfactants from Renewable Furan and Fatty Acids
    (2018-05) Joseph, Kristeen Esther
    An important advance in fluid surface control was the amphiphilic surfactant composed of coupled molecular structures (i.e., hydrophilic and hydrophobic) to reduce surface tension between two distinct fluid phases. Surfactants are widely used in household detergents, cleaners, emulsifiers, foaming agents, and personal care products. Anionic surfactants constitute 50% of the $30 billion global surfactant industry and are widely used in household detergents, and personal care products. Linear alkylbenzene sulfonates (LAS) are widely used due to their low cost and high detergency. Current LAS production methods rely on toxic catalysts and petrochemical-based constituents, such as benzene and long chain hydrocarbons. The reaction has low selectivity to the prescribed linear structure thereby rendering minimal control over the desired composition and properties. Additionally, implementation of simple surfactants such as LAS has been hindered by the broad range of applications in water containing alkaline earth metals (i.e., hard water), which disrupt surfactant function and require extensive use of undesirable and expensive chelating additives. Despite years of technology development, most large-volume surfactants are made from petrochemical sources, while efforts to make renewable surfactants are focused on making existing surfactant structures from renewable sources. In this work, we demonstrate a new surfactant based on the natural structure and chemistry of plant-based oils and sugars with superior function and suitability as a replacement to petrochemicals. Furans obtained from lignocellulosic biomass can be acylated with triglyceride-derived fatty acids and anhydrides in the presence of a heterogenous zeolite catalyst. The results obtained for the reaction of lauric anhydride with furan show that different pore sizes, structures and acidity of zeolites result in varying acylation activity. Preliminary kinetic studies of the indirect acylation using anhydrides provide insight into reaction orders and product inhibition resulting in lowering of catalytic activity. Following acylation, the molecule can be upgraded via several independent and sequential chemistries such as etherification, hydrogenation and aldol condensation and finally subjected to sulfonation to yield surfactant molecules termed as oleo-furan sulfonates (OFS) in high yield. Evaluation of surfactant performance of OFS revealed hundredfold better detergency and stability in hard water conditions in comparison with petroleum-derived counterparts. The synthesis of OFS molecules is, highly tunable and selective where the number of carbon atoms in the linear or branched chain can be easily varied without compromising on reaction yields to achieve desired surfactant properties.