Influence of Al2O3 support on the activity of Ag/Al2O3 catalysts for SCR of NO with decane

Abstract

The role of the Al 2 O 3 support on the activity of supported Ag catalyst towards the selective catalytic reduction (SCR) of NO with decane is elucidated. A series of Ag/Al 2 O 3 catalysts were prepared by impregnation method and characterized by N 2 pore size distribution, XRD, UV-Vis, in-situ FT-IR and acidity measurement by NH 3 and pyridine adsorption. The catalytic activity differences of Ag/Al 2 O 3 are correlated with different properties of Al 2 O 3 supports and the active Ag species formed. 4wt% Ag supported on sol-gel prepared Al 2 O 3 (Ag/Al 2 O 3 (SG), showed higher NO x conversion (65% at 400°C), compared with the respective catalysts made from commercial Al 2 O 3 (Ag/Al 2 O 3 (GB), Ag/Al 2 O 3 (ALO), ($26 and 7% at 400°C). The higher surface area, acidity and pore size distribution in sol-gel prepared Al 2 O 3 (SG) results in higher NO and hydrocarbon conversion. Based on the UV-vis characterization, the activity of NO reduction is correlated to the presence of Ag n d+ clusters and acidity of Al 2 O 3 support was found to be one of the important parameter in promoting the formation and stabilization of Ag n d+ clusters. Furthermore from pyridine adsorption results, presence of more number of Bronsted acid sites in Ag/Al 2 O 3 (SG) is confirmed, which could also contribute to low temperature hydrocarbon activation and improve NO conversion. In situ FT-IR measurements revealed the higher rate of -CN and -NCO intermediate species formation over 4wt% Ag/Al 2 O 3 (SG). We conclude that the physico-chemical properties of Al 2 O 3 play a crucial role in NO x conversion over Ag/Al 2 O 3 catalysts. Thus, the activity of the Ag/ Al 2 O 3 catalyst can be tailored by using a proper type of Al 2 O 3 support.

Role of the support on the behavior of Ag-based catalysts for NH 3 selective catalytic oxidation (NH 3 -SCO)

“…The following parameters were used to collect data: 800-200 nm measurement range and 200 nm/min scanning speed. The measured spectra were converted into Kubelka-Munk functions and deconvoluted into Gaussian subbands that could be quantitatively assigned to the different Ag species [12,[18][19][20][21].…”

Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx reaction: Structural and reactivity effects

“…There are many species (spectra not shown) formed on the addition of H 2 over both catalysts. Below 2000 cm −1 , nitrates (1302 cm −1 ), formates (1393 and 1377 cm −1 ), acetates (1460 cm −1 ), and carboxylates (1589 cm −1 ) are observed [15,22,23,31,32,[34][35][36][37][38]43]. In addition, bands appearing between 2886 and 3000 cm −1 are associated with CH 3 and CH 2 stretching vibrations of hydrocarbon species [13,22,23,31,32,43].…”

“…Silver-based catalysts are one of the most promising and cost effective systems for NO x HC-SCR but are relatively inactive at temperatures below 300 • C [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Various modifications to the standard wet impregnation preparation technique have been G Model CATTOD-9316; No.…”

“…of Pages 9 investigated with a view to improving the activity of aluminasupported Ag catalysts. For example, co-precipitation [20], sol-gel processes [21][22][23][24][25] and hydrolysis [26][27][28] methods have been reported but, until recently, the highest activity catalysts prepared by these methods are produced via wet impregnation from aqueous solutions using AgNO 3 as the Ag precursor. In addition, the effect of the addition of hydrogen has been extensively studied [29][30][31][32][33][34][35][36][37][38][39].…”

Lean-burn NOx Reduction by Propene over Gold Supported on Alumina Catalysts Derived from the Sol–Gel Method

“…In addition, materials prepared by different methods resulted in different adsorption capacities of NO, water, and so on, leading to different catalytic performances [26]. It was also reported that the surface acidity contributed from the sol-gel improved hydrocarbon activation and NO conversion [27].…”