Fixed-bed catalytic wet peroxide oxidation of phenol with titania and Au/titania catalysts in dark

It was established that nanostructured TiO2 with crystal size in range of 4.5-30 nm display stable operation in phenol CWPO in dark [PhOH = 200 ppmw] yielding 52-76% TOC conversion in a fixed-bed reactor at pH = 2.5, T = 80 degrees C and LHSV = 3.8 h(-1). Deposition of similar to 3 wt.% of Au nanoparticles increases the catalytic activity of TiO2 in CWPO of phenol defined as pseudo-first-order rate constant of substrate mineralization by a factor of 2.0-2.8 depending on Au crystal size. Small 3-4 nm Au nanoparticles aggregate at reaction conditions with complete deactivation of Au component. Larger 7-8 nm Au nanoparticles are stable against aggregation and deactivation. No leaching of Ti and Au was detected in runs with duration up to 300 h. The CWPO with both Au and TiO2 catalysts proceeds according to radical mechanism mostly in the part of catalysts layer where H2O2 is completely decomposed. At proper operation conditions TiO2 and Au/TiO2 catalysts allow reaching > 95% mineralization of phenol and stable operation. (C) 2014 Elsevier B.V. All rights reserved.