Influence of Preparation Methods of In 2 O 3 /Al 2 O 3 Catalyst on Selective Catalytic Reduction of NO by Propene in the
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Catalysis Letters Vol. 103, Nos. 1–2, September 2005 (Ó 2005) DOI: 10.1007/s10562-005-6506-6
Influence of preparation methods of In2O3/Al2O3 catalyst on selective catalytic reduction of NO by propene in the presence of oxygen Junhua Li*, Jiming Hao, Xiangyu Cui, and Lixin Fu Department of Environmental Science and Engineering, Tsinghua University, Beijing, 100084 P.R. China
Received 7 March 2005; accepted 12 May 2005
Selective catalytic reduction of NO with propene was investigated over In2O3/Al2O3 catalysts prepared by three methods, namely, a single sol-gel (SG), impregnation (IM), and co-precipitation method (CP). The catalysts were characterized by means of BET, XRD, XPS, and TPD. The maximum NO conversion over In2O3/Al2 O3 prepared by sol-gel method was 95% at 400 °C in the absence of H2O, and the activity decreased slightly in the presence of H2O, and it was still 76% even in the presence of H2O and SO2. Although the retarding effect of SO2 on the activity was observed for the three catalysts, In2O3/Al2O3 (SG) showed relatively high activity. It is found that the high surface area and low average pore diameter are important to the catalytic activity, and the strong interaction between indium and alumina for In2O3/Al2O3 catalyst prepared by sol-gel method may be the reason of high activity for NO reduction. The reaction and surface studies showed that NO3) and partially oxidized hydrocarbons (RCOO) species) are mainly intermediates, and the oxidation C3H6 to RCOO) species maybe the key reaction process in the SCR of NO with C3H6. KEY WORDS: NO reduction; selective catalytic reduction; lean-burn; de-NOx catalyst; Indium/Alumina; preparation method.
1. Introduction Nitrogen oxides are major pollutants in the atmosphere and need to be removed from exhaust gases. Selective catalytic reduction (SCR) of nitrogen oxides is an efficient way to remove NO from lean burn gasoline and diesel exhaust [1,2]. Several precious metal, metal oxide and zeolite catalysts have been reported to efficiently reduce NO. However, the poor hydrothermal stability of zeolite-based catalysts leads to an irreversible deactivation of the catalyst at high temperature in the presence of water vapor [3–5]. Noble metal-based catalysts have high activity and stability at low temperature in the presence of water vapor and SO2, but the inevitable greenhouse gas N2O and narrow operation temperature window are serious problems for practical application [6–9]. Metal-oxide based catalysts have high NO reduction activity over the high temperature range, and have been widely investigated in recent years [10–14]. Indium has previously been reported to be an active element supported on the zeolite and metal oxide support materials under lean burn conditions [15–18]. Among them, indium supported on alumina seems to be a promising catalyst for selective catalytic reduction of NO in the presence of oxygen. Nevertheless, almost all the catalysts reported were prepared by a single method. Apparently, the preparation method is a critical factor to the catalytic ac
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