Application of Optical-fiber Photoreactor for CO₂ Photocatalytic Reduction

An optical-fiber photoreactor, comprised of 216 catalyst-coated fibers, was designed and assembled to transmit and spread light uniformly inside the reactor. The power loss of light transmission inside an optical fiber was calculated using beam propagation method. The optimum length of optical fiber was estimated to be near 11 cm long in order to entirely spread out light energy over surface catalyst. Vapor-phase CO₂ was photocatalytically reduced to methanol using the photoreactor under UV irradiation in a steady-state flow system. The solutions of metal-loaded titania were prepared by thermal hydrolysis method. Metal-loaded TiO₂ film was coated on optical fibers by dip-coating method. TiO₂, Cu/TiO₂ and Ag/TiO₂ films were uniformly on the fibers and their thicknesses ranged from 27 to 33 nm. The films consisted of very fine spherical particles with diameters of 10–20 nm. The XRD spectra indicated anatase phase for all films. Methanol yield increased with UV irradiative intensity. Maximum methanol rate was 4.12 μmole/g-cat h using 1.0 wt%-Ag/TiO₂ catalyst at 1.13 bar of CO₂, 0.03 bar of H₂O pressures, and 5,000 s mean residence time under 10 W/cm² UV irradiation.