Photo-catalytic degradation of volatile organic compounds [VOCs: benzene, toluene and p-xylene (BTX)] was investigated using a batch reactor having a TiO2 (catalyst)-coated aluminum sheet and a source of UV light (sunlight or UV lamp). To study the photo-oxidation, experiments were conducted under the following configurations: (1) TiO2 (m): microparticle (0.32–3.31 µm) and sunlight (2) TiO2 (n): nanoparticle (0.80–4.70 nm) and sunlight, (3) TiO2 (m) and UV lamp and (4) TiO2 (n) and UV lamp. Degradation of BTX followed first-order decay for individual compounds. The degradation rate constant in min−1 cm−2 (coated surface area) was the highest for configuration (4) (benzene 1.07 × 10−3, toluene 1.36 × 10−3 and p-xylene 2.93 × 10−3) followed by configuration (2), thus indicating the importance of particle size of the catalyst in degradation. Degradation of BTX mixture did not follow first-order decay. Benzene was an intermediate product of oxidation of toluene. Benzene and toluene were intermediate products of oxidation of p-xylene. For degradation of BTX mixture, a mathematical model was proposed to predict concentrations as a function of time. Experimental and model results showed similar trends in BTX degradation. The model accounted for increases in mass of toluene and benzene due to the degradation of p-xylene.