Chemical Engineering Commons^™

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 …

Evaluation Of Unifac Group Interaction Parameters Usijng Properties Based On Quantum Mechanical Calculations, Hansan Kim

Theses

Current group-contribution methods such as ASOG and UNIFAC are widely used for approximate estimation of mixture behavior but unable to distinguish between isomers. Atoms in Molecules (AIM) theory can solve these problems by using quantum mechanics and computational chemistry to compute atomic contributions to molecular properties and to intermolecular interactions. Rigorously defined properties available through AIM theory and new functional group definitions are used for the UNIFAC model to predict the behavior of various mixtures. Results are presented for various mixtures with nine regressed global parameters to optimize model's predictive capability. The results are also compared to analogous results for …

Evaluation Of Knox Group Contribution Parameters Using Quantum Based Molecular And Group Properties, Myriam Carrillo

Theses

Thermodynamic property prediction through the group contribution methods has been improving. However, the approaches considered in the past present not only limitations on the physical basis but often have restrictions as to certain substances, such as isomers. A new group contribution method is proposed that uses AIM theory, which is based on computational chemistry and quantum mechanics, to overcome these limitations by treating each molecule individually. An evaluation of this method as applied to the Knox model is proposed and analyzed for Vapor Liquid Equilibrium (VLE) of mixtures with the help of nine global parameters that are obtained by correlation. …

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 …

Fluidization Of Agglomerates Of Nanoparticles Under Different Force Fields, Jose A. Quevedo

Theses

Nanoparticles are the focus of many research activities, and in the near future they will be handled in large amounts by industry. Fluidization is a very important unit operation which is applied in several industrial processes.

In the present work, fluidization experiments with agglomerates of nanoparticles were done under different force fields: (1) gravity force or conventional fluidization; (2) a magnetic force field, which uses magnetic particles under the influence of a magnetic field; and (3) a centrifugal force, generated by a rotating frame that simulates higher gravity conditions.

Among the significant results with agglomerates of nanoparticles, conventional fluidization was …

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 …

Mathematical Modeling Of Transient State Transdermal Drug Delivery, Alison Nickol Weltner

Theses

In this work, a two-pathway mathematical model for transdermal drug delivery with iontophoresis is presented. The partial differential equations are described and then solved. An alternative, two-pathway, three-layer model is also presented, and the implications of the coefficients within the equation are discussed. Using Franz cell iontophoretic delivery data from three drug substances (amitriptyline HCl, clomipramine HCl, and nortriptyline HCl), the two-pathway model is regressed to determine the diffusion coefficient and the concentration within the skin at the drug reservoir interface. ANOVA analysis indicates a correlation between iontophoretic current and concentration of drug within the stratum corneum.

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 …

Kinetics Of Ho2 Abstraction Of H Atoms From Hydrocarbons And Thermochemical Properties Of Urethane Monomers And Radicals, Rajul Shah

Theses

SECTION I: Kinetics of HO₂ Abstraction of H Atoms From Hydrocarbons

Structures, internal rotational barriers and ideal gas thermochemical properties, ΔH^°_f98 for representative series of transition states for abstraction of H atoms from primary, secondary and tertiary hydrocarbons by the HO₂ radical, TC-HOOH (1), TCC-HOOH (2), TC₂C-HOOH (3), TC₃C-HOOH (4), TC₂CC-HOOH (5), TC₂CC-HOOHC (6) and TC₃CCC-HOOH (7) are analyzed in this study. Molecular structures and vibrational frequencies are determined at the B3LYP/6-3111G(d,p) density functional level. The S°₂₉₈ and C_p(T) values (300≤T/K≤1500) from vibrational, …

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') …

Production Of Nanocrystalline Nitramine Energetic Materials By Rapid Expansion Of Supercritical Solutions, Victor Stepanov

Theses

Nanotechnology is a rapidly evolving field and has been characterized as "the next industrial revolution". Nanostructured materials are receiving increasing amount of attention in fields ranging from electronics to metallurgy due to their novel and unique properties. This work was focused on exploring the benefits of nanofabrication of high density energetic materials. The work primarily focused on the feasibility and viability of recrystallization of nitramine explosives down to the nanometer crystal size (<100 nm). It is anticipated that properties of the high density energetic materials such as sensitivity, packing density, crystal quality, energetic performance will be benefited.

Rapid Expansion of Supercritical Solutions was chosen as the process most appropriate to realize the objective. Solubility of CL-20 in supercritical solutions was studied. Nitramine crystals with …

Modification Of Biodegradable Polyesters With Inorganic Fillers, Georgia Chouzouri

Theses

In attempts to address the growing need of materials with controlled degradation characteristics and good mechanical properties for tissue engineering applications, composites based on biodegradable polymers and a potentially bioactive novel inorganic synthetic filler were produced and characterized. Composites were produced by solution mixing of a commercial polylactic acid, as well as a biodegradable thermoplastic polyester based on butylene adipate/succinate, with synthetic magnesium/aluminum carbonate minerals, known as hydrotalcites. Two types of hydrotalcites, at 30 wto/o filler level, were used: surface coated and uncoated. Composites were also melt-mixed in a twin-screw extruder for comparison.

Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), …

Role Of Catalyst And Substrate In Synthesis Of Single Wall Carbon Nanotubes, Amit Goyal

Theses

The synthesis of single wall carbon nanotubes (SWNTs) by the catalyticdisproportionation of carbon monoxide (CO) (i.e., Boudouard reaction) at I atm pressureand 700-800 C, has been systematically investigated in order to determine whether theprocess can be used for the large scale production. SWNT diameter distribution andmorphology were studied by Raman scattering, and scanning and transmission electronmicroscopy, respectively. X-ray diffraction was used to determine levels of the remnantcatalyst and support. Synthesis experiments were conducted using a three-stage processwith hydrogen to reduce the catalyst-precursor and argon to cool the system. Two typesof catalyst/support synthesis were studied: (1) Combustion synthesis to form catalyst …

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 …

Liquid-Liquid Mixing In Stirred Tanks With Varying Liquid Depths, Sunil Mehta

Theses

Considerable attention has been devoted in the past to the determination of the minimum agitation speed, N_cd, required for the complete dispersion of two immiscible liquids in mechanically stirred tanks. When this situation is achieved the dispersed phase is no longer present as a distinct layer, such as a light oil phase above an aqueous solution, but becomes completely dispersed, in the form of droplets, throughout the continuous phase. The achievement of the dispersed state is of significant importance in many industrial operations. Nevertheless, the effect on N_cd of a number of operating variables remains poorly understood. …

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 …

Dry Particle Coating And Granulation In Rotating Fluidized Beds, Madhuri Kolli

Theses

The practicability of using rotating fluidized bed as dry particle coater and granulator is investigated in this study. Dry particle coating, in which fine guest particles are coated onto bigger host particles in the absence of binders or solvents, is studied for various systems of host and guest particles. Coating results are explained by considering the collisions between the host and guest particles and among themselves. Balance between collisional energy and adhesion energy is suggested to be the limiting condition for the adhesion and hence the coating of guest particles onto host particles. It is observed that the experimental and …

Absorption Of Co2 Through Hollow Fiber Membranes Using Aqueous Solutions Of Various Absorbents, Praveen Babu Kosaraju

Theses

Absorption behavior of CO₂ was studied in different hollow fiber membrane modules fabricated using Celgard (polypropylene) and poly(4-methylpentene-1) microporous hollow fibers. Pure water, aqueous solutions of poly(amidoamine) (PAMAM) dendrimer of generation zero and monoethanolamine (MEA) were used as the absorbent; the absorbent solution flowed through the fiber bore, the gas mixture of C02 and N2 flowed countercurrently on the shell side. The system consisted of absorption in one module and stripping with Helium in another module of the same fibers. The absorption characteristics of the dendrimer solution and the MEA solution were studied in the modules built of Celgard …

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 …

An Investigation Of Centrifugal Blood-Cell Separation, Timothy Edward Roche

Dissertations

This dissertation investigated the centrifugal, batch separation of whole blood into subpopulations of red blood cells (erythrocytes) and white blood cells (leukocytes). Separations took place in a custom-built centrifuge (using a seal-less, anti-twisting feed/withdrawal system) containing, a 25-ml capacity separation chamber. The blood separation chamber had dart-shaped geometry in the radial plane and a constant depth in the axial direction. Separation experiments were performed on whole bovine blood at varying hematocrit, centrifuge speed, and batch duration. A small, companion study of whole human blood separation runs also were conducted; they concentrated on batch duration effect and achieved superior separations.

A …

An Experimental Study Of Dry Particle Coating : Devices, Operating Parameters And Applications, Michelle Ramlakhan Mohan

Dissertations

Dry particle coating, which mechanically coats fine guest particles onto the surfaces of larger host particles, without binders or solvents, is investigated. Several systems of host and guest particles are coated in different devices to study various aspects of dry particle coating. The devices used are Magnetically Assisted Impaction Coating (MAIC) device, Mechanofusion, and the Hybridizer.

MAIC is used to coat fine SiO₂ guest particles onto the surface of larger cornstarch and cellulose host particles. This is done to simultaneously improve the flowability of the host particles, as well as reduce their hydrophilicity. Dry particle coating is used to …

Immobilized Liquid Membranes For Facilitated Transport And Gas Separation, Anjaneya Sarma Kovvali

Dissertations

Separation and purification of gas mixtures is a major area of activity in chemical engineering. Gas separation using facilitated transport membranes has been the subject of considerable research for many years. Immobilized liquid membranes (ILMs) are an important class of facilitated transport membranes. Despite their potential to provide superior performance, they could not achieve commercial success so far due to their instability. Recent research addressed the issue of stability of ILMs by replacing water as the solvent successfully with glycerol. In the present thesis, the relevance of glycerol as an ideal solvent for developing stable ILMs is demonstrated using the …