471518 Revisiting the Tubular Flow Reactor Experiment
Revisiting the Tubular Flow Reactor Experiment
Yanir Maidenberg and J. Patrick Abulenicia
The tubular flow reactor experiment is a common reaction kinetics example in the unit operations laboratory sequence. In this experiment, students are typically tasked to examine reaction conversion as a function of both volumetric flow rate and residence time. More specifically, students evaluate if the fluid-flow regime (i.e. laminar or turbulent flow) or the time in the reactor plays a more effective role in generating the desired products.
The chemical reaction that has been traditionally used at our institution, as well as many other institutions, is the saponification of ethyl acetate to form ethanol. Briefly, solutions of sodium hydroxide and ethyl acetate are prepared in separate vessels and then introduced simultaneously at prescribed flow rates into the tubular flow reactor. Students can calculate the degree of conversion for the reaction by either monitoring the conductivity - either at the inlet or outlet - or by performing a titration against hydrochloric acid to calculate uncreacted sodium hydroxide. This process would be repeated over several volumetric flow rates to cover the laminar and turbulent regimes. Although this is a robust reaction, the authors began exploring ways to improve some areas of the tubular flow reactor experiment. First, the conductivity measurements from this setup exhibited great fluctuation as the reactants flowed, which made it difficult for students to reliably collect data. Second, variations among different groups were found due to the bias inherent in determining start point and end point of titrations. Third, sodium hydroxide is a strong base, and can be dangerous if handled improperly (it has a health rating of 3). Last, it was found the reaction proceeded too slowly to discern any statistically meaningful variations.
To this end, the authors began to explore other possible chemical reactions for this experiment, with the following criteria: 1) it had to be safe, 2) conversion should be easily measured, and 3) relatively inexpensive. A fourth (but less important) criterion is that the reaction undergo a color change, so that visual confirmation of the reaction conversion could be observed in the clear glass reactor at the institution. In this presentation, the authors will outline several alternative reactions for the tubular flow reaction experiment, as well as a summary of past work by chemical engineering educators on this topic.
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