Activation of Chemical Reactions in Microstructured Reactors: Employing Corona Discharge

The use of microchannel-based devices for chemical processing (microreactors and micro-unit operations) at large industrial scale requires massive parallelization of these systems into a microstructured reactor (a.k.a. “numbering up”).  Numbering-up is a straightforward approach to accomplish for homogenous or heterogeneous catalytic reactions and for reaction processes driven by heat.  Other systems, for example photocatalytic processes, are harder to activate due to difficulties indistributing the activating principle into an array of microchannels (light, in the case of a photocatalytic device).  An approach that has been employed to activate reactions in macroscale reactors is the use of electric discharge through the reaction medium which leads to the creation of highly reactive species as a consequence of the electrical discharge [[1]] as an alternative to photocatalyzed approaches [[2]].  Since distribution of electrical power within a microchannel-based device is a straightforward engineering task, we have examined the possibility of creating a corona discharge activated microreactor. To evaluate the performance of a corona discharge microreactor we chose to investigate the oxidation of dibenzothiophene by organic peroxide in a decane solution.  This reaction is of potential technical significance as it forms a promising basis for the oxidative desulfurization of fossil fuels to achieve ultra-low sulfur content in fuel streams.  In the implementation of a microchannel reactor activated in this novel manner, the performance of the emitter electrode was enhanced through the use of a nanostructured material consisting of carbon nanotubes embedded in a conductive epoxy matrix to take advantage of the extreme electric field gradients created by the extremely sharp tips of CNT fibers [[3]]. 

We will present details of the construction of our reactor, electrical performance of the plasma system (turn on voltage and I-V dependence) and chemical conversion efficiency of the corona discharge activated microreactor towards the oxidation of dibenzothiophene in the reactor.

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[1] Kirkpatrick, M. J.; Locke, B. R. “Hydrogen, Oxygen, and Hydrogen Peroxide Formation in Aqueous Phase Pulsed Corona Electrical Discharge” Ind. Eng. Chem. Res. 2005, 44, 4243-4248.

[2] Ollis, D.F.; Pelizzetti, E.; Serpone , N. “Destruction of water contaminants” Environ. Sci. Technol. 1991, 25, 1522-1529.

[3] W. A. de Heer, A. Châtelain, D. Ugarte “A carbon nanotube field-emission electron source” Science 1995, 270, 1179 – 1180.