Oxidation of Light Alkanes Using Photocatalytic Thin Films

摘要

This investigation studied the photocatalytic oxidation of light alkanes using photocatalytic thin films. In the research presented, nearly complete oxidation of isobutane, n-butane and propane using ZrO2/TiO2 thin films in a single pass reactor was demonstrated. The importance of reactor design on the effectiveness of the photocatalytic reaction is discussed in terms of photocatalyst packing and adequate illumination for catalyst activation. The influence of relative humidity in the contaminant feed stream and the reactor operating temperature were evaluated to establish optimal operating conditions for the photocatalytic reactor. Further photocatalytic studies used propane as a probe compound to investigate metal-modification of photocatalytic thin films as a means to improve propane oxidation and mineralization. Six precious metals (Ag, Au, Pd, Pt, Rh, and Ru) were tested at 1 weight percent loadings in TiO2, SiO2/TiO2, and ZrO2/TiO2 thin films. The photocatalytic reactor was operated at temperatures up to 100 C with the expectation that a thermal catalytic enhancement due to the precious metals would be observed. Propane conversion data revealed that at 1% loading, the addition of metals to the thin films reduced the activity for conversion of propane, regardless of temperature. However, the reactor temperature iii significantly affected light irradiance. Reaction rates adjusted for the influence of temperature on reactor irradiance revealed the highest reaction rates occurred at 100 C, but evaluation of Langmuir-Hinshelwood-Hougen-Watson kinetics showed that temperature significantly reduced the surface adsorption of propane. Of the 21 materials tested, an unmodified ZrO2/TiO2 thin film had the best activity for propane conversion and mineralization. Lastly, a novel method to investigate the photoinduced change in surface potential of photocatalytic thin films was investigated.