Promotion of low temperature oxidation of toluene vapor derived from the combination of microwave radiation and nano-size Co3O4

Co3O4 nano-particles were prepared deriving from the complexation reaction of ultrasonic treatment at room temperature and atmospheric pressure for low temperature oxidation of toluene under microwave radiation. Differences of catalytic performance of nano-and bulk Co3O4 under microwave radiation and conductive heating were investigated using the removal rate and the mineralization rate as assessment criteria. The result shows that the low temperature oxidation of toluene was promoted apparently by the combination of microwave radiation and nano-Co3O4. For effects of microwave radiation, maximum increases of removal rate and mineralization rate are 4.76 and 95.93 times respectively. FTIR spectra of the surface of the post-reaction catalyst shows that the amount of OH and H2O is larger under microwave heating and residual toluene or by-product of the incomplete decomposition is detected under conductive heating, which the results may be explained by the hypothesis of hot spots induced by microwave radiation. For effects of the nano-Co3O4 material properties, maximum increases of removal rate and mineralization rate are 1.84 and 220.9 times, respectively. Though XRD patterns of both nano-and bulk Co3O4 present a pure phase of Co3O4, catalytic activity of nano-Co3O4 is higher, because of smaller the particle size distribution, larger the surface area, higher levels of the Co2+/Co3+ and the Olatt/Oads, which may be due to reciprocal action between complexation reaction and ultrasonic treatment. Moreover, for integrated advantages of both microwave radiation and nano-Co3O4, maximum increases of removal rate and mineralization rate are 3.54 and 220.9 times, respectively.