Chemical Engineering Commons^™

Enhanced Fluidization Of Nanoparticle Agglomerates, Daniel Lepek

Dissertations

Gas fluidization of nanoparticle agglomerates has recently received much attention due to the excellent way in which these novel nanornaterials can be dispersed in a gaseous medium. Nanopowders have a very high surface area to volume ratio which allows them have unique chemical and physical properties especially at the surface. Fluidization is a popular technique for the continuous dispersal of solid materials in the fluidlike state.

Recently it has been found that nanoparticles exist in a highly agglomerate state which allow them to become fluidizable. The fluidization behavior of the nanopowders is dependent on the bulk and material properties of …

Flexography Printing Of Silver Based Conductive Inks On Packaging Substrates, Ramesh Chandra Kattumenu

Dissertations

Printing technologies for the production of flexible electronics have gained much interest due to its potential as a means to reduce the complexity and costs of present technology. High volume printing techniques like flexography are of great importance in order to produce rolls of flexible electronics printed directly on paper substrates. The proposed research will be focused on RFID components being in-line printed using flexography printing as the manufacturing platform. The properties of substrates and inks and printing process parameters are evaluated to study their effect on printed traces and RFID antenna. It was found in the study that properties …

Novel Polypropylene Based Microporous Membranes Via Spherulitic Deformation, Kuan-Yin Lin

Dissertations

A novel method for creating a microporous polypropylene membrane via spherulitic deformation is described. The microporous structure was generated by the combination of intra-spherulitic and inter-spherulitic deformations. Polypropylene was selected due to its unique cross-hatched lamellar morphology facilitating inter-spherulitic deformation. A precursor film with a spherulitic structure was made under low-stress melt processing condition. A tangential lamellae-rich spherulite was created and identified with a positive birefringence sign. A sequential annealing process improved the crystalline structure, and in particular the thickness of the tangential lamellae. The annealing process proved to be critical for initiating the inter-spherulitic deformation. The post-extrusion process conditions …

Degradation Of Polylactic Acid In The Presence Of Microsize And Nanosize Fillers, Quyuan Zhou

Dissertations

Polylactide (PLA)-cationic (montmorillonite, MMT) and anionic (hydrotalcite, HT) clay micro- or nanocomposites based on semicrystalline and amorphous polymers and unmodified and organomodified as well as calcined or non-calcined clays at 5wt% concentration are produced by melt mixing. Depending on the clay type, presence of organomodifiers and calcination, micro- or nanocomposites are produced, as confirmed by XRD and SEM analysis.

Unfilled polymers and their composites are subjected to isothermal degradation in air at 180°C and 200°C. Degradation rate constants are calculated from novel equations incorporating IV. Results show that the thermal degradation rate constants of the amorphous PLA and its composites …

Production Of Nanocrystalline Rdx By Ress : Development And Material Characterization, Victor Stepanov

Dissertations

The aim of the present work was to address the hazardous vulnerability of energetic materials to accidental initiation. An improved form of the explosive RDX with a significantly reduced sensitivity to stimuli including shock and impact was sought. The direction of this research was to investigate the effect of RDX crystal size reduction down to nano-scale dimensions on the sensitivity characteristics. Although size reduction of energetic crystals has been demonstrated often to result in a sensitivity reduction, the effect at the nano-scale particle size has not been investigated.

To generate nanocrystalline RDX a recrystallization process was developed based on rapid …

Removal And Recovery Of Fermentation-Produced Volatile Organic Compounds By A Novel Liquid Membrane-Based Pervaporation Technique, Atsawin Thongsukmak

Dissertations

Pervaporation is an energy -- efficient alternative to distillation for removing volatile organic compounds (VOCs) from water especially solvents from their dilute solutions in a fermentation broth. Liquid membranes have high selectivities for removing solvents from aqueous solutions compared with polymeric membranes or ceramic membranes; however liquid membranes have stability problems due to various losses. The loss of liquid membrane (LM) to the feed solution leads to toxicity for the organisms in a fermentation broth. A new liquid membrane based pervaporation technique has been developed to achieve high selectivity, ensure stability and prevent contamination of the fermentation broth. Trioctylamine (TOA) …

New Approaches To Scaled-Up Carbon Nanotube Synthesis And Nanotube-Based Metal Composites And Sensors, Amit Goyal

Dissertations

The first phase of the work presented in this dissertation is the development of a scaleable process for the cost-effective synthesis of single walled carbon nanotubes (SWNTs) by thermally-induced catalytic chemical vapor deposition (CVD). With the goal of understanding the growth mechanism and optimize the synthesis process, the effect of CVD and catalyst parameters on nanotube formation was investigated in detail. It was found that nucleation and growth of SWNTs occurred within a few seconds of the introduction of the carbon source, carbon monoxide, at temperatures above 675°C over a Co-Mo/MgO catalyst/support system, resulting in the formation of high quality …

In Vitro Studies Of Degradation And Bioactivity Of Aliphatic Polyesther Composites, Georgia Chouzouri

Dissertations

In spite of numerous publications on the potential use of combinations of aliphatic polyester composites containing bioactive fillers for bone regeneration, little information exists on the combined in vitro mechanisms involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for bone regeneration, from experimental data along with their engineering interpretation.

Bioactivity, in terms of apatite growth, was assessed through several experimental methods such as scanning electron microscopy (SEM), energy dispersive …

Hydrodynamics Investigation Of In-Vitro Dissolution Testing, Ge Bai

Dissertations

Dissolution testing is routinely carried out in the pharmaceutical industry to determine dissolution rate of solid dosage forms. The United States Pharmacopoeia (USP) Dissolution Apparatus II is the device most commonly used for this purpose. Despite its widespread use, dissolution testing remains susceptible to significant error and test failures. Limited information is available on the hydrodynamics of this apparatus, although hydrodynamic effects can play a major role on test performance.

Laser-Doppler Velocimetry (LDV) and Computational Fluid Dynamics (CFD) were used here to experimentally map and computationally predict the velocity distribution inside a standard USP Apparatus II under the typical operating …

Solvent Resistant Microporous/Nanoporous Polymeric Hollow Fiber And Flat Film Membranes And Their Applications, Praveen B. Kosaraju

Dissertations

The separation and purification of organic-solvent-based process streams may be carried out by membrane processes such as nanofiltration/ultrafiltration/microfiltration and membrane solvent extraction. Lack of solvent stability and chemical stability of most commercially available membranes is limiting the utilization of the above mentioned membrane technologies. This dissertation was primarily focused on developing solvent resistant hollow fiber and flat film membranes for separation and purification of organic-solvent-based process streams.

Available porous polymeric supports (Polypropylene (PP), Polyethersulfone (PES) and Nylon) suitable for the required solvent-stable applications were chosen first and then the supports were modified to satisfy the requirements for the applications. Membrane …

Enhancement Of Fluidization And Filtration Using Nanoparticle Agglomerates And Aerogels, Jose A. Quevedo

Dissertations

Previous works have classified the fluidization behavior of nanoparticles as Agglomerate Particulate Fluidization (APF) and Agglomerate Bubbling Fluidization (ABE). These fluidization behaviors are quite different in regard to the fluidized bed expansion, the presence of bubbles and the smoothness of the bed surface, with APF nanopowders showing a much more homogeneous fluidization and a much better dispersion than ABE nanopowders which are generally very difficult to fluidize and show vigorous bubbling. In the present work, the fluidization of APF as well as ABF nanopowders is studied in depth, both conventionally, and in the presence of extemal assistance; several related topics …

Reactive Modification And Crystallization Behavior Of Foamed Poly(Butylene Terephthalate), Byeong Joon Jeong

Dissertations

The objective of this study is to investigate the feasibility of preparing low density foams based on poly(butylene terephthalate) (PBT) through modification of its molecular structure and rheological characteristics by reactive extrusion. The scientific and/or engineering interpretation of the experimental data was based on fundamentals of extrusion, crystallization mechanisms, as well as information on reactivity and tendency toward degradation of PBT.

As a preliminary study, the extrusion foaming behavior of a commercial linear semi-crystalline PBT with a chemical blowing agent (CBA) was investigated. Foam characteristics were functions of extrusion operational variables, such as die set temperature and screw speed. Gas …

Applications Of Room Temperature Ionic Liquids In Interfacial Polymerization, Lining Zhu

Dissertations

Room temperature ionic liquids (ILs), with their unique physical and chemical properties, have been of great interest in various areas of chemical science and engineering during the last decade. In this dissertation, polyurea and polyamide films with surface nanostructures were synthesized by interfacial polymerization (IP) with ILs without stirring. Both polymers were prepared at the interface between n-hexane and a series of 1 -alkyl-3-methylimidazolium ILs.

Nanoporous or nanofibrous polymer morphologies with various sizes ranging from 50 to 500 nm and geometries, depending on the ILs used, were observed by scanning electron microscopy (SEM). A correlation length of ~20nm and a …

Phase Transitions Of Poly (L-Lactic Acid) In Bulk And In Solution, Jing Zhang

Dissertations

Poly(L-lactic acid) (PLLA) has been subject to intensive research in recent years because of its biodegradability. Applications of PLLA, such as porous tissue engineering scaffolds and excipients for controlled release, have been developed in the biomedical and pharmaceutical fields. The crystal structures and morphologies of this semicrystalline polyester are the underlying factors that determine the mechanical and degradation properties of PLLA.

A fundamental understanding of the development of crystal structures and morphologies during the phase transitions of PLLA in bulk and in solution is pursued in this dissertation. Synchrotron wide- and small-angle x-ray scattering (WAXS and SAXS) are adopted as …

Optimization Of Sequential Purification Of Beta-Glucosidase From Tricoderma Reesei In Aqueous Two-Phase System, Shalini Gautam

Dissertations

A novel sequential technique was developed for the purification of a valuable enzyme, beta-glucosidase, from microorganism Tricoderma reesei. The fungus T. reesei produces cellulose degrading enzymes, called cellulases: beta-glucosidase, endo-glucanase and exo-glucanase and low molecular weight proteins. For specific applications, the enzyme must be separated from other contaminants. The sequential technique, that included affinity precipitation with chitosan followed by separation with an aqueous two-phase system (ATPS), was implemented for the purification of beta-glucosidase from the culture filtrate of T. reesei.

The cultivation medium (nutrient) was optimized for the production of betaglucosidase from T. reesei cell culture. Treatment of the …

Fluid-Phase Thermodynamics From Molecular-Level Properties And Interactions Based In Quantum Theory, Steven G. Arturo

Dissertations

A methodology to predict the thermodynamics of macroscopic fluid systems from quantum chemistry and statistical thermodynamics has been developed. This work extends the group-contribution concepts most utilized in chemical engineering. Computational chemistry software is used to define the geometries and electron density profiles of target molecules. Atoms in Molecules theory and associated software packages are used to calculate rigorous properties of the functional groups within molecules of interest. These properties are incorporated into an intermolecular potential energy function which describes interactions between entire molecules as a set of interactions between functional groups. This information is applied to a lattice-fluid model …

Crystalization Studies In Hollow Fiber Devices, Dimitrios Zarkadas

Dissertations

Crystallization was examined under a new perspective and in a flow environment much different from that available in currently used industrial devices. Three crystallization techniques were tested in the unique flow environment offered by hollow fiber devices. In addition, a new type of heat exchanger based on hollow fibers was tested as well as the potential use of porous hollow fiber devices as mixing devices. Hollow fiber devices are compact, extremely efficient on a volumetric basis, easy to scale up and control and their inherent characteristics promote the creation of homogeneous temperature and concentration conditions on a scale considerably smaller …

Fluidization Of Nanoparticles, Caroline Hijung Nam

Dissertations

During the past decade, nanoparticles (1-100 nm) and nanocomposites have become the focus of many studies due to the unique properties of nanostructured materials that make them attractive for various applications. Due to their atomic and molecular interactions, nanoparticles and nanocomposites have unique and often favorable catalytic, mechanical, optical, electronic and / or other properties. For instance, nanocrystalline copper is up to 5 times harder than conventional micron sized copper particles. Nanocomposites, such as a homogenous mixture of different nanoparticles, can also exhibit improved properties. Other examples include coating and reacting nanoparticles with a second nanostructured phase. These processes are …

Novel Internally-Staged Ultrafiltration For Protein Purification, Meredith Ann Feins

Dissertations

A new ultrafiltration technique based on a multimembrane stack has been developed to fractionate proteins closer in molecular weight than conventionally possible. The technique is illustrated here by obtaining a pure protein product from a binary protein mixture. By employing membranes in series using the same membrane without any gaskets or spacers in-between, ultrafiltration is carried out to separate two proteins relatively close in molecular weight. Flat membranes, of the same molecular weight cutoff (MWCO) 30,000 or 100,000, are stacked together in the desired number, and ultrafiltration takes place. The membrane rejection of a protein is amplified with each additional …

Studies On Improved Integrated Membrane-Based Chromatographic Process For Bioseparation, Yanke Xu

Dissertations

To improve protein separation and purification directly from a fermentation broth, a novel membrane filtration-cum-chromatography device configuration having a relatively impermeable coated zone near the hollow fiber module outlet has been developed. The integrated membrane filtration-cum-chromatography unit packed with chromatographic beads on the shell side of the hollow fiber unit enjoys the advantages of both membrane filtration and chromatography; it allows one to load the chromatographic media directly from the fermentation broth or lysate and separate the adsorbed proteins through the subsequent elution step in a cyclic process.

Interfacial polymerization was carried out to coat the bottom section of the …

Thermochemistry And Kinetic Analysis On Radicals Of Acetaldehyde + O2, Allyl Radical + O2 And Diethyl And Chlorodiethyl Sulfides, Jongwoo Lee

Dissertations

Thermochemical properties for reactants, intermediates, products and transition states important in the radicals of acetaldehyde + O₂ and allyl radical + O₂ reaction systems are analyzed with density functional and ab initic calculations, to evaluate the reaction paths and kinetics in oxidation and pyrolysis. Ketene is one important product resulting from acetaldehyde oxidation; thus thermochemistry plus isomerization and conversion reactions of ketene are also analyzed. Enthalpies of formation are determined using isodesmic reaction analysis at the CBSQ composite and density functional levels. Entropies and heat capacities are determined using geometric parameters and vibration frequencies obtained at the HF/6-31G(d') …

A Reactive Melt Modification Of Polyethylene Terephthalate, Rahul Ramesh Dhavalikar

Dissertations

This work investigates the structural and chemorheological modification of polyethylene terephthalate in the melt phase with low molecular weight multifunctional glycidyl compounds as reactive additives. Polyethylene terephthalate undergoes chain extension and/or branching reactions with the additives that result in modified rheological properties suitable for certain polymer processing operations such as extrusion blow molding or extrusion foaming to low densities.

Among five different low MW difunctional and trifunctional epoxy compounds, triglycidyl isocyanurate is shown to be an efficient reactive melt modifier for commercially available polyethylene terephthalate polymers. Its stability at the polyethylene terephthalate melt temperatures is confirmed offline through thermogravimetric and …

Study Of Vapor/Gas Permeation Using Thin Immobilized Liquid Membrane, Gordana Obuskovic

Dissertations

To improve liquid membrane selectivity and stability for removal of vapor and gases from a gas stream, a thin immobilized liquid membrane (ILM) has been studied. Low vapor pressure liquid solvent/solutions were immobilized in part of the micropores of a hydrophilic, hydrophobic or ceramic hollow fiber substrate. To prepare such thin ILMs, three approaches were used: evaporation of the a volatile solvent; acrylic acid-grafted hollow fibers providing a thin hydrophilic layer; pressurization technique.

For removal of volatile organic compound (VOC), a thin ILM of silicone oil incorporated in the micropores of a hydrophobic hollow fiber with a silicone rubber coating …

Synthesis And Enzymatic Resolution Of Amino Acid Esters In "Green" Solvents -- Ionic Liquids, Hua Zhao

Dissertations

Chiral separation has attracted tremendous attention in pharmaceutical and chemical fields, especially in the area of chiral drug development. Chiral amino acids are among the most important intermediates in the asymmetric synthesis of modem drugs. This research has developed an effective method for obtaining optically pure amino acids by enzymatic resolution using a "green" solvent, named an ionic liquid.

Ionic liquids, a new type of "green" solvents, have been used in many organic reactions and other chemical processes (such as liquid-liquid extraction) with improved performance. This is mainly due to their favorable properties for chemical applications, such as low vapor …

The Development Of H Homogeneous Nucleation Rate Model For Thermoplastic Foams Based On A Molecular Partition Function And Fickian Diffusion, Ronald G. Gabbard

Dissertations

An improved homogeneous nucleation rate model for thermoplastic foams has been developed. This model does not rely on experimentally determined parameters and only uses pure component physical property data and a binary diffusion coefficient. This model, like those derived from classical nucleation theory, is made up of two parts, one that determines the size of the energy barrier in the nucleation process and one that estimates the forward rate of the process. A statistical-mechanical approach was used to create an energy term that is based on a molecular partition function. In this approach, the bulk phase (polymer and blowing, agent …

Process Control Of A Laboratory Combustor Using Neural Networks, Thana Slanvetpan

Dissertations

Active feedback and feedforward-feedback control systems based on static-trained feedforward multi-layer-perceptron (FMLP) neural networks were designed and demonstrated, by experiment and simulation, for selected species from a laboratory two stage combustor. These virtual controllers functioned through a Visual Basic platform. A proportional neural network controller (PNNC) was developed for a monotonic control problem - the variation of outlet oxygen level with overall equivalence ratio (Φ₀). The FMLP neural network maps the control variable to the manipulated variable. This information is in turn transferred to a proportional controller, through the variable control bias value. The proposed feedback control methodology …

Application Of Chemical Kinetic Modeling To Improve Design And Performance Criteria For A Practical Incineration System, Charles A. Bass Jr.

Dissertations

In this study, detailed thermo-chemical kinetics with networked ideal reactor model were applied to simulate a practical combustion system -the Secondary Combustion Chamber (SCC) of the Rotary Kiln incineration Simulator (RKIS) at the EPA facility at Research Triangle Park, NC. The networked ideal model was developed using analysis of reactor geometry, temperature profile measurements, and SO₂ tracer data provided by EPA. A computer simulation of the networked model was developed using the CHEMKIN H library. A parallel effort considered the effects of non-ideal mixing on detailed thermo-kinetic, simulations. Specifically, an alternate approach was developed to solve the Partially Stirred …

Elementary, Pressure Dependent Model For Combustion Of C1, C2 And Nitrogen Containing Hydrocarbons : Operation Of A Pilot Scale Incinerator And Model Comparison, Chad Sheng

Dissertations

A 140000 BTU/hr pilot scale incinerator has been constructed, tested and run; and an online sampling train capable of taking in situ data has been established. The continuous on-line analytical instruments include a CO analyzer, an NO/NOx analyzer and an 02 analyzer. In addition, two gas chromatographs with flame ionization detector are used to determine CH4, C2H2 + C2H4 and total hydrocarbon concentrations. Typical operating conditions are at an average 02 concentration of 6 - 8 %. The NO concentration ranged from 100 - 200 ppm. Approximately I ppm of CH.4 is also present at steady state operations.

The kinetic …

Evolutionary Polymorphic Neural Networks In Chemical Engineering Modeling, Li Gao

Dissertations

Evolutionary Polymorphic Neural Network (EPNN) is a novel approach to modeling chemical, biochemical and physical processes. This approach has its basis in modern artificial intelligence, especially neural networks and evolutionary computing. EPNN can perform networked symbolic regressions for input-output data, while providing information about both the structure and complexity of a process during its own evolution.

In this work three different processes are modeled: 1. A dynamic neutralization process. 2. An aqueous two-phase system. 3. Reduction of a biodegradation model. In all three cases, EPNN shows better or at least equal performances over published data than traditional thermodynamics /transport or …

Modeling And Experimental Validation Of A Single-Feed Semi-Batch Precipitation Process, Ernesto Uehara-Nagamine

Dissertations

Crystallization is a widely practiced unit operation throughout the chemical and pharmaceutical process industries. Despite its widespread application, crystallization still suffers a disproportionate number of process difficulties due to the complexity of the steps involved in the process. In particular, the final characteristics of the product are strongly affected by the mixing conditions during the process. The development of a validated modeling approach would be highly valuable for the successful prediction of the crystal characteristics under differing mixing conditions.

In the present work, the single-feed semi-batch precipitation process of barium sulfate in a stirred tank was experimentally studied and numerically …