Byproduct shape selectivity in supercritical water oxidation of 2-chlorophenol effected by CuO/ZSM-5

Reduction of trace polycyclic aromatic hydrocarbon (PAH) byproducts in supe rcritical water oxidation (SCWO) of a-chlorophenol (2CP) effected by CuO/ZS M-5 has been investigated in the present work. In the channels of ZSM-5, du e to a restricted environment, formation of undesired PAH byproducts in the SCWO of 2CP was significantly suppressed. Only trace light-PAHs with a mol ecular size less than 6 Angstrom were formed in the SCWO of 2CP. Carcinogen ic PAHs (heavy-PAHs) were not found. Structures of CuO and Cu2O in the chan nels of ZSM-5 that involved in the catalytic SCWO of 2CP were studied by X- ray photoelectron spectroscopy (XPS). The Cu2O-to-CuO ratio was approximate ly 0.15. Existence of the Cu(I) and Cu(II) was also confirmed by the preedg e X-ray absorption near edge structural (XANES) spectroscopy. The copper ox ides with a square-plane structure were observed by electron paramagnetic r esonance (EPR) spectra. Furthermore, the extended X-ray absorption fine str uctural (EXAFS) spectra suggest that the copper oxides in the channels of Z SM-5 may form Cu3O2 clusters with Cu-Cu and Cu-O bond distances of 2.79 and 1.91 Angstrom, respectively. The Cu3O2 clusters were oxidized to Cu3O4 by H2O2 in supercritical water.