Photocatalytic oxidation of methanol using silica-titania composites in a packed-bed reactor

The processing of forest products into pulp, paper, paperboard, and other wood products results in the generation of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). This work focused on the development of a photocatalytic packed-bed reactor for the oxidation of methanol, which is the primary constituent in high volume low concentration gases emitted from pulp and paper mills. Bench-scale studies using an annular reactor packed with silica-titania composite (STC) pellets were conducted to maximize methanol removal and minimize the formation of byproducts, such as form-aldehyde. Parameters such as STC pore size (ca. 40, 120, and 260 Å) and UV wavelength (UVA and UVC) were varied. In the dark, the STC pellets removed methanol via adsorption and had a finite adsorption capacity dependent on the surface area of the composite. When irradiated with UV light, the STC pellets adsorbed and oxidized methanol simultaneously. At the bench-scale, 40 Å STC pellets irradiated with UVC light achieved the greatest methanol removal (ca. 90%) with minimal byproduct formation (i.e., effluent formaldehyde concentration was <1 ppm _v). Based on these results, a 40 acfm pilot reactor was fabricated and achieved methanol removal rates up to 66% ± 7% with <1 ppm _v formaldehyde production at steady state.