so much so at time t = 0.5 h, the concentration of benzene decreased, and degradation compounds lighter than benzene, started appearing (Figure ). The molar mass of benzene is M = 78.11 g.mol -1 . A recent work by Chen et al., by means of in-situ diffuse reflectance infrared Fourier transform spectroscopy over ZnWO4 nanorods, proposed methylene (CH2, M = 14.03 g.mol -1 ), coming from the breaking of the aromatic ring, as a possible initial degradation by-product of benzene photocatalytic oxidation . Ollis and co-authors, by means of GC/MS analysis, found carboxylic acids -acetic and formic acid (M = 60.05, and 46.03 g.mol -1 , respectively) -as intermediates of benzene photocatalytic oxidation over TiO2 . Thus, the presence of those intermediates is reasonable here. At t = 2 h, and t = 4 h irradiation time (Figure ), there is an increase in concentration of lighter degradation compounds of benzene. As a result, it is evident that different reaction conditions give different reaction mechanisms/paths for the gas-phase photocatalytic oxidation of benzene . Yet, a real application requires a stable reuse of the photocatalytic material. Stability of Cu-G1.0/450 over three consecutive photocatalytic runs is displayed in Figure .