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Title:Chemical Kinetics of Manganese Catalyzed Sulfur-Dioxide Autooxidation That Occurs in the Solution Phase of Slurries
Author(s):Erwin, Jimell
Department / Program:Chemical Engineering
Discipline:Chemical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Chemical
Abstract:This study deals with the manganese catalyzed oxidation of bisulfite and sulfite anions by molecular oxygen in a tubular flow calorimeter. Solutions of oxygen and sulfur dioxide anions at the same pH and temperature with varying catalyst combined in an efficient Teflon mixer to form the reaction system. This inert, adiabatic, microcomputer-automated reactor used thermistors to capture the resulting temperature profiles for the kinetic determinations by the method of initial slopes. For the sodium based reaction the conditions were: T 25° 20° - 35° °C pH 4.4 - 6, 11 11 {S('4+)} 0.003 - 0.15 M/1 {O(,2)} 0.004 - 0.015 M/1 {Mn} 10 - 2000 0.05 - 10 ppm (wt).
Under these conditions the reaction order is in sulfite and in oxygen although the oxygen order may be an artifact of oxygen's effect on maintaining the manganese in its divalent oxidation state in which it promotes initiations in this free radical chain reaction. Supplying this catalyst only in the sulfite solution surpresses the oxidation rate, while for catalyst in the oxygen solution or in both reservoirs, concentrations 10 to 2000 ppm at pH 6 the rate constant grows from 0.06 to 45 1('2)M('-2)s('-1).
For calcium sulfite oxidation the range of conditions was: T 25° °C pH 3.8 - 4.7 {S('4+)} 0.00136 - 0.00456 M/1 {O(,2)} 0.00642 - 0.0172 M/1 {Mn} 10 - 2000 ppm (wt).
The reactant orders where constant as the catalyst concentration changed by three decades. The catalyst's action though, clouded by Mn(OH)(,2) insolubility and MnO precipitation at 2000 ppm, increased the rate constant from 100 to 1000 1('2)M('-2)s('-1) as Mn grew from 10 to 1000 ppm. As pH advanced beyond pH 4.5, the rate increased at a rate ten times faster (with pH) than at the low pH values.
Succinic acid, in a few batch experiments whose pH was held constant by base addition under computer control, retarded the reaction rate, decreasing the rate constant from 0.13 to 0.0039 1 M('-1)s('-1). This heterogeneous (gas/liquid) reaction did not proceed as fast as the comparable homogeneous case.
The activation energy for the oxidation dropped from 18.4 (+OR-) 5 kcal M('-1) (Z = 8.7 (+OR-) 2.5 x 10('12) 1 M('-1) s('-1)) for 0.05 ppm Mn to14.5 (+OR-) 3.3 kcal M('-1) (Z = 1.1 (+OR-) 0.3 x 10('10) 1 M('-1)s('-1)) with 1.0 ppm Mn when the ratio of oxygen concentration to the sulfite concentration was about 0.5 or higher. Combined with the dual behavior of the catalyst, this change is strong evidence for multiple, independent, simultaneous reactions.
The introduction has a brief history of the research on the reaction and its widespread applications. There are 281 references with many summaries and comparisons from this literature in the background chapter and the discussion.
Issue Date:1980
Description:351 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.
Other Identifier(s):(UMI)AAI8108500
Date Available in IDEALS:2014-12-13
Date Deposited:1980

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