Selective catalytic reduction of NOx with C3H6 over an Ag/Al2O3 catalyst with a small quantity of noble metal

Abstract

The selective catalytic reduction of NO x with C 3 H 6 (C 3 H 6 -SCR of NO x ) was carried out in the presence of water vapor over various trace noble metal (Pt, Au and Pd) co-impregnated with Ag/Al 2 O 3 catalysts. The Ag-Pd (0.01%)/Al 2 O 3 shows a higher NO x conversion than Ag/Al 2 O 3 does, especially at temperatures ranging from 300 to 500 • C. However, the additions of Au and Pt to Ag/Al 2 O 3 only resulted in a decrease of activity for the C 3 H 6 -SCR of NO x . In situ DRIFTS spectra suggests that the presence of trace Pd (0.01%) catalyzed the formation of an enolic species which was converted from C 3 H 6 , whereas the presence of Pt and Au did not show this effect. The surface enolic species is very active towards NO 2 and NO 3 − , resulting in the formation of an NCO species which is the key reaction intermediate in the selective catalytic reduction of NO x .

Effect of SO2 on the performance of Ag-Pd/Al2O3 for the selective catalytic reduction of NOx with C2H5OH

“…Both the partial oxidation of reductant and the formation of nitrates are the important steps during the SCR of NOx (Shimizu et al, 2000a;Satokawa et al, 2001;Burch et al, 2002;Corro et al, 2003;He et al, 2003He et al, ,2004He and Yu, 2005;Yu et al, 2003Yu et al, , 2004Wang et al, 2004). Meunier et al reported that the oxidation of NO was suppressed over Ag/A1203 upon sulfation (Meunier and Ross, 2000).…”

Selective catalytic reduction of NOx over Ag/Al2O3 catalyst: from reaction mechanism to diesel engine test

“…In our recent papers [36][37][38][39][40][41], the formation and dynamic performance of partial oxidation products of C 2 H 5 OH and C 3 H 6 over Ag/Al 2 O 3 were studied by an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) method, and we found a novel enolic species originating from the partial oxidation of C 2 H 5 OH. As shown in Fig.…”

“…Taking our earlier works [16,17,[36][37][38][39][40][41][42][43][44][45] into account, we proposed a mechanism for the NO x reduction by C 2 H 5 OH, which can be described by a simplified reaction scheme, as shown in Scheme 2. The reaction starts with the formation of both adsorbed nitrates via NO oxidation by O 2 and enolic species and acetate via the partial oxidation of C 2 H 5 OH over Ag/Al 2 O 3 .…”

“…The supported catalysts, Ag/Al 2 O 3 and Cu/Al 2 O 3 , were prepared by an impregnation method with an aqueous solution of silver and copper nitrate, followed by evaporawww.elsevier.com/locate/cattod Catalysis Today 100 (2005) [37][38][39][40][41][42][43][44][45][46][47] tion to dryness in a rotary evaporator under pressure reduction at 60 8C. The wet sample was dried at 120 8C for 12 h, and then calcined in air at 600 8C for 3 h [39].…”

Promotional Effect of Titanium on the Catalytic Performance of Anodic Alumina Supported Silver Catalyst for the Selective Reduction of NO with Propene

“…The higher formation rate of isocyanate, which was a major reaction intermediate, was considered to be a main reason. The addition of 0.01 wt% Pd to 5 wt% Ag/Al 2 O 3 was also found to increase the de-NO x activity in SCR with C 3 H 6 at low temperatures, both in the absence and presence of SO 2 (He et al, 2003;Wang et al, 2004). The results of in situ DRIFTS spectra suggested that the presence of trace Pd catalyzed the formation of enolic species which were converted from C 3 H 6 , whereas the presence of Pt and Au did not show this effect.…”