Regeneration of the catalyst deactivated during the photocatalytic oxidation process run at high humidity requires much shorter catalyst treatment time than that for the catalyst deactivated by photocatalytic oxidation run at low humidity. This phenomenological behavior suggests that hydroxyls play a significant role in both the oxidation and regeneration processes. The methylamine photocatalytic disappearance rate follows first order kinetics for inlet concentrations below 20 ppm v , with a shift to a fractional order at higher concentrations. The destruction rate is inhibited by the presence of water vapor. Under the conditions of the experiments, selectivity to desired carbon dioxide was inversely correlated with conversion, and was enhanced by water vapor and low methylamine concentration.
Nitrogen builds up in a variety of forms on the catalyst surface.
However, the catalyst appears to be reasonably robust in that N adatom buildup does not significantly slow the methylamine destruction rate. In the absence of UV irradiation shows bands indicative of methylamine adsorbs molecularly on titania. Bands for the complete oxidation product carbon dioxide were also observed. No evidence was found for creation of nitrate groups on the catalyst surface. The major conclusions of this research for each target VOC are summarized above.