Bifunctional mesoporous Cu-Al-MCM-41 materials for the simultaneous catalytic abatement of NOx and VOCs

Abstract

This study explored the possibility of using waste organic solvent as the source of volatile organic compound (VOC) and it served as a reducing agent of selective catalytic reduction (SCR) deNO(x) process, in which the VOC itself can be catalytically oxidized on the mesoporous Cu and/or Al substituted MCM-41 catalysts. The synthesized Cu-Al-MCM-41 catalysts were extensively characterized by powder low-angle X-ray diffraction (XRD), N-2 adsorption-desorption measurements, transmission electron microscopy (TEM), UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS), Al-27 magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR), electron paramagnetic resonance spectroscopy (EPR) and inductively coupled plasma-mass spectrometer (ICP-MS) analysis. The XRD, TEM and N2 adsorption-desorption studies clearly demonstrated the presence of a well ordered long range hexagonal array with uniform mesostructures. The Cu-Al-MCM-41 materials showed a better long-term-stability than that of copper ion-exchanged H-ZSM-5 (Cu-ZSM-5) zeolite. The Cu-Al-MCM-41 material was found to be an efficient catalyst than that of Cu-MCM-41 without aluminum for the simultaneous catalytic abatement of NOx and VOCs, which was attributed to the presence of well dispersed and isolated Cu2+ ions on the Cu-Al-MCM-41 catalyst as observed by UV-Vis DRS and EPR spectroscopic studies. And the presence of aluminum (Al3+ ions) within the framework of Cu-Al-MCM-41 stabilized the isolated Cu2+ ions thus it led to higher and stabilized activity in terms of NOx reduction. (C) 2008 Elsevier Inc. All rights reserved.