Dynamic Catalytic Microreactor Design and Operation in Overcoming Inherent Thermodynamic Limitations

Armstrong, Cameron

Etd

Dynamic Catalytic Microreactor Design and Operation in Overcoming Inherent Thermodynamic Limitations

Public Deposited

Over a century of catalyst science has proven that kinetic catalytic rates are restricted by the thermodynamics of the surface-species interactions. This kinetic barrier is described by Sabatier’s rule and dictated by the scaling relations. These rules tell us that the more a catalyst is able to stabilize a transition state, the lower the activation barrier and thus the higher the kinetic rates. Stabilizing too much, however, becomes a problem as a products may never desorb off the catalyst surface, inhibiting the catalytic binding sites, and thus reaction rates. Sabatier’s rule suggests compromising by finding a material where a reactant is stable, but not so stable the product will never desorb. Recent studies have found creative ways to better optimize or even overcome this thermodynamic limitation, including alloyed catalysis, single atom catalysis, and dynamic catalysis. Dynamic catalysis involves periodically operating a reactor in a controlled, oscillatory fashion and is one such way to overcome the scaling relations as it moves away from thermodynamic equilibrated driving forces. Applied thermal oscillations which match the time scales of inherent catalytic phenomena has been a topic of particular interest over the past few years. Although these studies are primarily theoretical, matching an applied frequency to its natural frequency (i.e. catalytic turnover frequency) can lead to order of magnitude rate enhancements. Here, we investigate the design, fabrication, and validation in developing a catalytic microreactor capable of millisecond heating and cooling and challenge the isothermal paradigm chemical engineers have for so long operated under. We go on to build a full reactor test stand to determine the effects of thermal oscillations on a catalytic system and give insights as to what is happening at a molecular level.

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