Shape selectivity of trace by-products for supercritical water oxidation of 2-chlorophenol effected by CuO/ZSM-48

Shape selectivity of trace by-products in supercritical water oxidation (SC WO) of 2-chlorophenol (2CP) catalyzed by CuO/ZSM-48 has been investigated. Experimentally, destruction efficiency of 2CP in the SCWO process is effect ively enhanced by CuO/zeolite catalysts. In the two-dimensional (2D) channe ls of ZSM-48, formation of undesired by-products such as polycyclic aromati c hydrocarbons (PAHs) and higher chlorinated phenols (via the Cl-reinsertio n) is extremely suppressed in the SCWO of 2CP compared to those observed fo r zeolites ZSM-5 and Y with three-dimensional (3D) channel structure and la rger pore sizes, respectively. The main oxidation active species on CuO/ZSM -48 surfaces were CuO and Cu2O determined by X-ray photoelectron spectrosco py (XPS). Ratios of the surface species CuO/Cu2O are between 13.4 and 14.1 in the SCWO process. However, the existence of the Cu-O and Cu-Cu species w ith a Cu-O/Cu-Cu ratio of 3.5 in the copper catalyst is also observed by ex tended X-ray absorption fine structure (EXAFS) spectroscopy. Furthermore, s ince the absence of Cu-Cl species in the XPS and EXAFS spectra, one would s uggest that copper in the channels of ZSM-48 is unlikely involved in the ab straction of Cl species from 2CP in the SCWO process. (C) 1999 Elsevier Sci ence B.V. All rights reserved.