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Micromixing Experiments in the Undergraduate Curriculum Kevin D. Dahm, Robert P. Hesketh and Mariano J. Savelski Chemical Engineering, Rowan University

Abstract An issue that is not typically covered reactor design courses is mixing and reactions. In the 1 chapter on multiple reactions in the standard chemical reaction engineering text by Fogler , it is assumed that the reactions are slow compared to the mixing of species. The classic examples for parallel reactions and series reactions are given, but these examples do not cover the basic concept of micro-mixing with respect to the reactants. Only in the final chapter of this text is the concept of micro-mixing introduced using a mathematical theory that is relatively complex for undergraduates. We believe that it is important for undergraduates to have a concept of the importance of micro-mixing on chemical reactions in industrial reactors. This paper describes a series of experiments designed to introduce the concept of micro-mixing in an undergraduate chemical reaction engineering course. These experiments will give the basic problems associated with this phenomenon and illustrate the limitations of the ideal reactor models.

Introduction In practice the issue of mixing and chemical reactions is very important in economic aspects of chemical reaction engineering. A major priority in industrial reactors is to optimize the yield of desired products. This optimization is a function of reactor geometry, the chemical and physical characteristics of the reacting system, the degree of mixing and the mode of supplying the reactor 2 with reagents. Bourne and Gablinger have shown how process chemistry developed in the laboratory can go awry when scaled to industrial reactors. An excellent example of the classic 3 series-parallel reaction using an azo dye chemistry is presented by Bourne and Gholap. The chemist will optimize the reaction to obtain very high reaction rates for the desired reaction. However, in the industrial reactor, micro-mixing is a limiting factor, negatively impacting the 4 5 process chemistry. However, as explained by Etchells , a typical undergraduate reactor design course focuses on ideal reactors and would overlook the impacts of mixing on the reaction chemistry and the formation of trace byproducts. The goal of the experiments described here is to demonstrate to the student the practical limitations of the idealized models. 6 Baldyga and Bourne summarize a number of experimental examples of product distributions sensitive to mixing. Examples of parallel or competitive reactions include Diazo coupling with 7 8 simultaneous reagent decomposition and Iodate/iodine reaction with neutralization. Examples of parallel – series reactions or competitive-consecutive reactions include Diamines with isocyantes or other acylating agents, nitrations of dibenzyl, durene, and alkyl benzenes and diazo couplings. The experiments described in this paper involve this pair of parallel competitive reactions:

H2BO3- + H+ ↔ H3BO3 (1) 5I- + IO3- + 6H+ ↔ 3I2 + 3H2O (2)

Proceedings of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright  2002, American Society for Engineering Education Main Menu

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Savelski, M., & Hesketh, R., & Dahm, K. (2002, June), Micromixing Experiments In The Undergraduate Curriculum Paper presented at 2002 Annual Conference, Montreal, Canada. 10.18260/1-2--10893