The preparation of Fe ₂ O ₃ -ZSM-5 catalysts by metal-organic chemical vapour deposition method for catalytic wet peroxide oxidation of <i>m</i> -cresol

Abstract

Fe 2 O 3 -ZSM-5 catalysts (0.6 wt% Fe load) prepared by metal-organic chemical vapour deposition (MOCVD) method were evaluated in the catalytic wet peroxide oxidation (CWPO) of m -cresol in a batch reactor. The catalysts have a good iron dispersion and small iron crystalline size, and exhibit high stability during reaction. In addition, the kinetics of the reaction were studied and the initial oxidation rate equation was given. Catalysts were first characterized by N 2 adsorption–desorption isotherms, scanning electronic microscopy, energy-dispersive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results show that extra-framework Fe 3+ species (presenting in the form of Fe 2 O 3 ) are successfully loaded on ZSM-5 supports by MOCVD method. Performances of catalysts were tested and effects of different temperature, stirring rate, catalyst amount on hydrogen peroxide, m -cresol, total organic carbon (TOC) conversion and Fe leaching concentration were studied. Results reveal that catalytic activity increased with higher temperature, faster stirring rate and larger catalyst amount. In all circumstances, m -cresol conversion could reach 99% in 0.5–2.5 h, and the highest TOC removal (80.5%) is obtained after 3 h under conditions of 60°C, 400 r.p.m. and catalyst amount of 2.5 g l −1 . The iron-leaching concentrations are less than 1.1 mg l −1 under all conditions. The initial oxidation rate equation <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>−</mml:mo> <mml:mrow> <mml:msub> <mml:mi>r</mml:mi> <mml:mrow> <mml:mi>A</mml:mi> <mml:mn>0</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>7.2</mml:mn> <mml:mo>×</mml:mo> <mml:mrow> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:msup> <mml:mtext>e</mml:mtext> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>81300</mml:mn> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>R</mml:mi> <mml:mi>T</mml:mi> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:msub> <mml:mi>C</mml:mi> <mml:mi>A</mml:mi> </mml:msub> </mml:mrow> </mml:math> is obtained for m -cresol degradation with Fe 2 O 3 -ZSM-5 catalysts.