Molecules involved in chemical reactions require sufficient energy to overcome the activation energy barrier. This is true in spontaneous reactions at room temperature the fact that they are spontaneous merely means that the required energy is present in the form of ambient thermal energy. In a few cases this activation energy barrier can be lowered through the use of catalysts, and in some the energy can be supplied in alternative forms (other than sensible heat) such as sonochemical, photochemical, and electrical discharge. The primary objective of this work is to examine how non-thermal plasmas generated by electrical discharge through fluids may be used to drive chemical reactions in microchannel reactors. The model reactions chosen are the oxidation of organic molecules dissolved in aqueous media by dissolved atmospheric oxygen and the partial oxidation of methane to methanol. Preliminary work has demonstrated that the corona discharge activated oxidation takes place, and the technical literature suggests that electrical discharge activation of the partial oxidation of methane also occurs. The development of an efficient corona discharge activated microchannel reactor could lead to both an efficient approach to tertiary treatment of potable water by advanced oxidation and a method to constructively use stranded methane that is currently too expensive to recover, and also develop an entirely novel approach to the general activation of chemical reactions that will open new process reaction options for various applications. An important barrier to the implementation of electro-discharge processes in microreactors is the high voltage required to achieve spark or dielectric barrier discharge. The required voltages can be greatly diminished by enhancing the emitter electrode with carbon nanotubes.
Intellectual Merit: This project will systematically explore the development and implementation of corona discharge activated chemical reactions in microchannel reactors through the construction and experimental evaluation of the performance of an experimental device and the crafting of a careful model of the reactor operation. The project will be approached in the following manner:
1. Exploratory implementation of corona discharge activated reactive systems in microreactors: This will explore the manner in which a microchannel reactor within which a chemical reaction can be activated by corona discharge can best be built. In particular, the best methodology for the enhancement of the emitter electrodes with carbon nanotubes will be evaluated.
2. Experimental evaluation of the corona discharge driven oxidation in aqueous media: Using the CNT enabled corona discharge activated microreactor developed in task 1, the effect of varying reaction conditions will be evaluated. Factors to evaluate include applied potential, total power, thickness of the reactor channel, fluid flow rate (i.e., residence time) and dissolved oxygen concentration.
3. Partial oxidation of methane to methanol: Using the CNT enabled corona discharge microreactor, proof of concept followed by full exploration of process parameters will take place. Similar factors as described in 2 will be evaluated with the addition of methane/H2O/O2 ratios in the reactor performance.
4. Development of an explanatory/predictive model for the corona activated microreactor: Using the data collected in Tasks 2 and 3, a model of the reactor will be developed using COMSOL in which the effects of the factors described above will be evaluated. The particular information to be extracted from the model includes reaction rates and the thickness of the reacting volume in the system.
Educational Integration: The reactor system described will be used as a basis for formal education by developing 1) an experimental module where early program undergraduates in Chemical/Environmental Engineering can actually work with an advanced chemical process including the ability of tweaking a few parameters, 2) offering advanced students in the senior capstone experience sequence the opportunity to implement chemical processes using the developed platforms and 3) continuing to mentor undergraduate researchers through hosting Johnson scholars (first year college) and SESEY (high school) students in the laboratory to work on issues based on process implementation in microreactors. These students become an integral part of the research team.
Broader Impact: This research will result in the development of a novel method for chemical reaction activation within microchannel reactors, opening a new area of research for researchers developing reactive processes in microchannel reactors, hopefully enabling various future advances leading to the practical implementation of microreactor based processes. Simultaneously, the work will be used as a platform for informal (general public) and formal education for pre-college, undergraduate and graduate students (and fellow faculty!) on the issues surrounding the elimination of trace organic contaminants in potable water, and the implementation of processes in microstructured reactors in general.