Chemical and Biomolecular Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2751
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Item ENGINEERING HIERARCHICAL MESO-/MICROPOROUS LAMELLAR ZEOLITES WITH VARIABLE TEXTURAL AND CATALYTIC PROPERTIES(2016) EMDADI, LALEH; Liu, Dongxia; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Meso-/microporous zeolites combine the charactersitics of well-defined micropores of zeolite with efficient mass transfer consequences of mesopores to increase the efficiency of the catalysts in reactions involving bulky molecules. Different methods such as demetallation and templating have been explored for the synthesis of meso-/microporous zeolites. However, they all have limitations in production of meso-/microporous zeolites with tunable textural and catalytic properties using few synthesis steps. To address this challenge, a simple one-step dual template synthesis approach has been developed in this work to engineer lamellar meso-/microporous zeolites structures with tunable textural and catalytic properties. First, one-step dual template synthesis of meso-/microporous mordenite framework inverted (MFI) zeolite structures was investigated. Tetrapropyl ammonium hydroxide (TPAOH) and diquaternary ammonium surfactant ([C22H45-N+(CH3)2-C6H12-N+(CH3)2-C6H13]Br2, C22-6-6) were used as templates to produce micropores and mesopores, respectively. The variation in concentration ratios of dual templates and hydrothermal synthesis conditions resulted in production of multi-lamellar MFI and the hybrid lamellar-bulk MFI (HLBM) zeolite structures. The relationship between the morphology, porosity, acidity, and catalytic properties of these catalysts was systematically studied. Then, the validity of the proposed synthesis approach for production of other types of zeolites composites was examined by creating a meso-/microporous bulk polymorph A (BEA)-lamellar MFI (BBLM) composite. The resulted composite samples showed higher catalytic stability compared to their single component zeolites. The studies demonstrated the high potential of the one-step dual template synthesis procedure for engineering the textural and catalytic properties of the synthesized zeolites.Item HETEROGENEOUS POLYMERIZATION OF METHYL METHACRYLATE AT LOW TEMPERATURE IN DISPERSED SYSTEMS(2011) EMDADI, LALEH; CHOI, KYU YONG; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)ABSTRACT Title of thesis HETEROGENEOUS POLYMERIZATION OF METHYL METHACRYLATE AT LOW TEMPERATURE IN DISPERSED SYSTEMS Laleh Emdadi, Master of Science, 2011 Directed by: Professor, Dr. Kyu Yong Choi, Chemical and Biomolecular Engineering Department Dispersion polymerization is a unique method to prepare monodisperse polymer particles of 1-10 µm in a single step process. This process is usually carried out at high temperatures that are not cost effective and suitable for special applications such as encapsulation of bio materials. Production of uniform polymer particles at low temperatures via dispersion polymerization has not been studied widely yet. In this research, dispersion polymerization of methyl methacrylate (MMA) in a nonpolar solvent, n-hexane, using N,N-dimethylaniline (DMA) and lauroyl peroxide (LPO) as redox initiators at low temperature has been studied. The evolutions of monomer conversion, polymer molecular weight distribution (MWD), and particle morphology were determined. Under specific reaction conditions, monodisperse micron-sized polymer particles were produced. The same technique was applied in the confined reaction space of a monomer droplet. Using this new process, called micro dispersive suspension polymerization, polymer particles with different internal morphologies produced with various potential applications.