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http://hdl.handle.net/11375/20162
Title: | Mass Transfer Across a Liquid-Liquid Interface with and Without Chemical Reaction |
Authors: | Seto, P. |
Department: | Chemical Engineering |
Publication Date: | 1963 |
Abstract: | <p>The present study is divided into two parts. Part I was an attempt to investigate the steady state mass transfer across a liquid-liquid interface accompanied by a very slow, second order, irreversible chemical reaction using a glass vessel. Both liquid phases were well stirred and the lower phase was allowed to flow in and out of the reactor continuously. The system chosen for the study was ethyl acetate-sodium hydroxide solution. In order to simplify the transfer situation, the ethyl acetate phase was pre-situated with water, so that the transfer became uni-directional, from the upper phase into the lower phase. Experimental runs were performed at 25°C, 40°C and 55°C temperature levels and at various sodium hydroxide concentrations ranging from 0.0002 N. up to 0.389 N. (while other experimental conditions, for example, stirrer speeds and lower phase flowrates were kept constant). In each run, transfer rate of ethyl acetate into the lower phase was measured and the mass transfer coefficient was calculated.</p> <p>The results showed (a) Van Krevelen's film model for slow, second order, irreversible reaction system did not apply to ethyl acetate-sodium hydroxide because the reaction involved was too slow to cause any enhancement in mass transfer. (b) Mass trnasfer coefficient for reaction run was smaller than that for physical transfer into water; and the different was accounted for by an interfacial resistance (l/kr) apart from salt effect of sodium hydroxide and sodium acetate.</p> <p>The resistance (1/kr) varied directly as the concentration of sodium acetate, which, in turn, varied as a positive function of input sodium hydroxide concentrations in the bulk lower phase.</p> <p>The cause of the retardation to transfer was still uncertain. However, it was speculated to be due to (a) Modification of hydrodynamic conditions near the interface by salt and reaction effect. (b) Formation of a surface barrier due to the presence of impurities. (c) Formation of an additional reaction zone or film due to a very slow chemical reaction.</p> <p>In addition, an analogue study on concentration profiles of reactants and products in a film model was carried out. Also, J. B. Lewis' experiments were partly repeated and his method of evaluating physical mass transfer coefficients was discussed.</p> <p>Part II was a study of unsteady state diffusion accompanied by a slow, second order, irreversible chemical reaction across unstirred liquid-liquid phases. The systems of ethyl formate-sodium hydroxide and ethyl acetate-sodium hydroxide were chosen.</p> <p>The results of the schlieren investigation showed that when the ethyl ester, pre-saturated with water, was in contact with the sodium hydroxide phase, a zone was formed inside which reaction occurred. Turbulent liquid motion was observed in the zone which extended itself in course of time during the experiment.</p> <p>A great part of the experimental work was spent in an effort to search for information about the zone. The Moire pattern was made use of in studying the zone propagation. Experiments were performed at room temperature, with each of the ethyl ester contacting sodium hydroxide solution at various concentrations (one concentration for each experiment).</p> <p>The reaction zone thus formed was photographed at intervals. About 25 photographs were taken for each run. They were developed and analysed. In some runs, concentrations of reactants inside the zone were measured.</p> <p>The results showed (a) The speed of zone propagation was higher in the ethyl formate-sodium hydroxide system than in the ethyl acetate-sodium hydroxide system. Within the system the speed increased with initial sodium hydroxide concentration used, then passed through a maximum, and decreased with increasing sodium hydroxide concentration. (b) Concentrations of both reactants inside the zone were low as compared to their initial concentrations.</p> <p>A simple model was proposed to describe the zone propagation making use of the concept of eddy diffusivities.</p> |
Description: | Title: Mass Transfer Across a Liquid-Liquid Interface with and Without Chemical Reaction, Author: P. Seto, Location: Thode |
URI: | http://hdl.handle.net/11375/20162 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Seto_P_1963_master.pdf | Title: Mass Transfer Across a Liquid-Liquid Interface with and Without Chemical Reaction, Author: P. Seto, Location: Thode | 77.63 MB | Adobe PDF | View/Open |
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