Low temperature propylene SCR of NO by copper alumina catalyst

Abstract

NO reduction to N-2 by C3H6 was investigated on various copper alumina catalysts prepared by a precipitation method with different copper (Cu) weight percentages to that of aluminium (Al). The catalysts were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), Fourier transformed infrared (FT-IR) spectroscopy, Brunner Emmett Teller surface area (BET-SA), X-ray photoelectron spectroscopy (XPS), H-2-TPR (temperature programmed reduction) and scanning electron microscopy (SEM) techniques. It is found that the catalyst preparation method as well as the copper content exerts a significant influence on catalytic activity for NO to N-2 conversion. From the DTA analysis it is found that there is a loss of water and CO2 at 114 to 390 C and total weight loss by TGA at at found 600 C. A high conversion (70%) of NO to N-2 is obtained by the Cu-Al (3:7) catalyst at 300 degrees C in the presence of 600 ppm NOx + 600 ppm C3H6 + 8 vol.% O-2. The order of catalysts for higher NO to N-2 conversion is as follows: Cu-Al (3:7) > Cu-Al (2:8) > Cu-Al (4:6) > Cu-Al (1:9) > Cu-Al (7:3). The XPS results show that the Cu-Al (3:7) catalyst calcined at 600 C possess highly dispersed surface copper (Cu2+) species. The presence of high surface availability of copper (44.8%), in particular as CuAl2O4 phase, with a high percent intensity of 44 in the Cu-Al (3:7) catalyst is the key to obtaining high efficiency (70%) in a wide range of temperatures (250-400 C). From in situ diffused reflectance infrared Fourier transformed (DRIFT) spectral analysis, evolution of different intermediate species like -NO2, R-NO, -COO-, -CN, -NCO and -NH2 were observed with varying intensities on different Cu-Al catalysts at different reaction temperatures. (c) 2008 Elsevier B.V. All rights reserved.