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Theses/Dissertations

Chemical engineering

1996

Articles 1 - 8 of 8

Full-Text Articles in Engineering

Process Modeling Using Stacked Neural Networks , Dasaratha Sridhar Jan 1996

Process Modeling Using Stacked Neural Networks , Dasaratha Sridhar

Retrospective Theses and Dissertations

Typically neural network modelers in chemical engineering focus on identifying and using a single hopefully optimal neural network model. Using a single optimal model implicitly assumes that one neural network model can extract all the information available in a given data set and that the other candidate models are redundant. In general, there is no assurance that any individual model has extracted all relevant information from the data set. In this work, the stacked neural network approach is introduced. Stacked neural networks (SNNs) allow multiple neural networks to be selected and used to model a given process. The idea is ...


The Selective Hydrogenation Of Crotonaldehyde Over Bimetallic Catalysts , Ann Marie Schoeb Jan 1996

The Selective Hydrogenation Of Crotonaldehyde Over Bimetallic Catalysts , Ann Marie Schoeb

Retrospective Theses and Dissertations

The selective hydrogenation of crotonaldehyde has been investigated over a monometallic Pt/SiO2 catalyst and platinum bimetallic catalysts where the second metal was either silver, copper, or tin. The effects of addition of a second metal to the Pt/SiO2 system on the selectivity to crotyl alcohol were investigated;The Pt-Sn bimetallic catalysts were characterized by hydrogen chemisorption, 1H NMR and microcalorimetry. Pt-Ag/SiO2 and Pt-Cu/SiO2 catalysts were characterized by hydrogen chemisorption. Pt-Sn/SiO2 catalysts selectively hydrogenated crotonaldehyde to crotyl alcohol and the method of preparation of the these catalysts affected the selectivity. The most selective Pt-Sn/SiO2 catalysts ...


Computational Studies Of Glucoamylase Selectivity , Pedro Maldonado Coutinho Jan 1996

Computational Studies Of Glucoamylase Selectivity , Pedro Maldonado Coutinho

Retrospective Theses and Dissertations

Glucoamylase (GA) is an industrial enzyme involved in the production of glucose and fructose syrups from starch. Exhibiting a large spectrum of selectivities, GAs are able to cleave glucose from the nonreducing ends of [alpha]-(1,4) glycosidic bonds of maltooligosaccharide chains and the [alpha]-(1,6) bonds initiating their branches. The high temperatures and glucose concentrations occurring in saccharification lead to the formation of condensation products, reducing the overall glucose yield. Modified versions of Aspergillus GA that better satisfy industrial requirements are desirable. To achieve this, a structure-based multisequence alignment of the primary sequences of the catalytic domains, linkers ...


A Kinetic Study Of The Sulfidation-Regeneration Of Zinc Oxide Sorbent , Oreoluwa Abimbola Sofekun Jan 1996

A Kinetic Study Of The Sulfidation-Regeneration Of Zinc Oxide Sorbent , Oreoluwa Abimbola Sofekun

Retrospective Theses and Dissertations

Experimental studies on the sulfidation/regeneration of zinc oxide have been conducted to obtain precise data on the kinetics and structural changes involved, and to formulate appropriate rate expressions. The regeneration of zinc oxide (oxidation of zinc sulfide) particles conducted in a thermogravimetric analyzer (TGA) was found to be fast and complete between 548 and 630°C, with zinc oxide being the only product formed. However, under the influence of external mass transfer, the presence of an oxysulfate intermediate was observed for the first time. However, this decomposes upon completion of the reaction. The intrinsic kinetic parameters for the oxidation ...


Effect Of Pressure On The Kinetics Of Lysozyme Crystallization , Mungara Venkata Saikumar Jan 1996

Effect Of Pressure On The Kinetics Of Lysozyme Crystallization , Mungara Venkata Saikumar

Retrospective Theses and Dissertations

This work was targeted at characterizing the effect of high pressure on the kinetics of lysozyme crystallization via a series of experiments and mathematical modeling. Pressure effects on nucleation and crystal growth were distinguished by evaluating the rate constants for the two kinetic processes at various pressures;In the first phase of the work, the effect of high pressure on lysozyme crystallization was examined with a primary objective of increasing the rate of crystallization. Lysozyme crystallization was carried out initially at a concentration of 40 mg/mL, pH 4.5 and 0.8 M sodium chloride at pressures of 0 ...


Fundamental Studies Of Supported Bimetallic Catalysts By Nmr Spectroscopy , Nilesh R. Savargaonkar Jan 1996

Fundamental Studies Of Supported Bimetallic Catalysts By Nmr Spectroscopy , Nilesh R. Savargaonkar

Retrospective Theses and Dissertations

Characterization of a bimetallic catalyst in terms of its surface composition is important in understanding the mechanisms of reactions over such catalysts. Since catalytic surfaces are covered with adsorbates under reaction conditions, the influence of adsorbates on the surface compositions of bimetallic catalysts is also important. Hydrogen was found to influence the surface compositions of silica and alumina supported Pt-Rh catalysts to a certain extent as the surfaces of bimetallic catalysts were enriched in Rh under the influence of hydrogen. Although the extent of Rh enrichment of the surface was not large, the surface compositions in the presence of hydrogen ...


Energy Conversion And Entropy Production In Open Systems , Anca Stefanescu Jan 1996

Energy Conversion And Entropy Production In Open Systems , Anca Stefanescu

Retrospective Theses and Dissertations

In this work a macroscopic approach to the energetics of open, multicomponent, unsteady-state systems with chemical reactions has been proposed. A set of uniform equations describing material and energy conservation and entropy production has been derived and then applied to some limited, idealized situations. Simple, ideal systems such as adiabatic rigid tanks, steady-flow adiabatic steam turbines, and a steady-flow continuous stirred-tank reactor have been analyzed from an energy conservation and entropy generation standpoint. The same methodology has then been used to characterize the thermodynamics of complex, open, biological systems. Quantitative determinations of the lost work rates have been made for ...


Microphase Assisted "Autocatalysis" , Jennifer Gail Anderson Jan 1996

Microphase Assisted "Autocatalysis" , Jennifer Gail Anderson

Retrospective Theses and Dissertations

The mathematical model developed in this study considered reaction, crystallization, and microphase processes simultaneously to describe "autocatalytic" microphase action more effectively. Simulations were performed to determine the effect of crystal growth rates, nucleation rates and the initial crystal size distribution on the overall reaction rate enhancement produced by the microphase. The growth kinetics and the crystal size distribution were found to have a significant influence on the heterogeneous reaction rate. These results call into question previous models developed to describe "autocatalytic" microphases, as none of them include appropriate crystallization kinetic models;In the reaction system of solid calcium citrate and ...