Titanium-mordenites catalysts prepared by impregnation (TiMimp), solid-solid interaction (TiMss) and in situ incorporation during synthesis
(TiMin); using ortho-phenylenediamine as a new templating agent under hydrothermal conditions (TiCl4, 160 ◦C, 6 days), were thoroughly characterized
by TG/DTA, N2 adsorption, XRD, FTIR, UV–vis and pyridine-FTIR. They were tested; in comparison with TiO2 Degussa, for degradation
of meta-chlorophenol (MCP) in the presence of UV-light irradiation. It was possible to correlate the results obtained for MCP degradation over
various catalysts with their structural and acidic properties. The photocatalytic degradation of MCP has been modeled to Langmuir-Hinshelwood
rate law. TiMss showed the highest degradation rate (0.060 min−1) followed by those of TiMimp (0.050 min−1), TiMin (0.025 min−1) and TiO2-
Degussa (0.018 min−1), respectively. The marked higher rate observed for the former catalyst was due to the larger pore radius (29A° ), acidity and
the extra-framework TiO2 anatase species (of absorption at 340 nm). Very strong emphasize to the state of titania within the three samples (TiM)
was demonstrated and most importantly Si O Ti linkages (950–940 cm−1) were observed and correlated with photoactivities of all samples.
Degradation products of MCP, including both aromatic and aliphatic intermediates, were monitored by HPLC. Chloride ions, on the other hand,
were followed up during the degradation processes. Formic acid (formate) was identified as a final intermediate in the solution before it further
mineralized to CO2. Reasonable degradation pathway for MCP molecule is proposed on the basis of structural identification of several by-products.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Mordenite; Synthesis; Ti-incorporation; Characterization |
