Development of a Photocatalytic Oxidation-Based TOC Analyzer Part II: Effect of Reactor Design and Operation Parameters on Oxidation Efficiency of VOCs

This project sought to develop a photocatalytic oxidation (PCO) based total organic carbon (TOC) analyzer for real time monitoring of air quality in spacecraft. Specific requirements for this application were to convert volatile organic contaminants (VOC) into CO₂ stoichiometrically in a single pass through a small reactor with low power requirement. One of the greatest challenges of this TiO₂-mediated PCO was the incomplete oxidation of some recalcitrant VOCs leading to less reactive intermediates that deactivate the catalyst over time. Dichloromethane (DCM) is one of these VOCs. The effect of some design factors (e.g. TiO₂ catalyst surface area to volume ratio and UV photon flux field) as well as operating conditions of an annular reactor (e.g. VOC residence time and relative humidity) on the efficiency in converting DCM to CO₂ were investigated. Results demonstrated that UV irradiated TiO₂ surface areas and VOC residence time were key controlling factors for overall conversion efficiency and sustainability of the catalyst activity.