Low Temperature Selective Catalytic Reduction of No by Co over Titania Supported Catalysts
Pavani M. Sreekanth, University of Cincinnati, 2600 Clifton Avenue, Cincinnati, OH 45221 and Panagiotis (Peter) Smirniotis, Chemical & Materials Engineering Department, University of Cincinnati, 2600 Clifton Avenue, Cincinnati, OH 45221.
A series of transition metal oxide (M = Cr, Mn, Fe, Co, Ni, Cu) promoted anatase titania catalysts were prepared by wet impregnation method using dilute solutions of metal nitrate precursors. The catalytic activity of these materials was evaluated for selective catalytic reduction (SCR) of NO with CO in the presence of excess oxygen at low temperatures (175–250 °C). The reaction was carried out by varying the NO/CO mole ratios for different O2 concentrations in the feed. All catalysts showed good NO conversion levels ranging from 40-80 % in the temperature region of 175-250°C and at high space velocity of 50,000 h1. Among all the catalysts tested, Cu-based samples exhibited very promising NO conversion with high N2 selectivity. This can be attributed to the generation of facile one electron redox couple (Cu2+ ↔ Cu+), which is very important for the NO decomposition and the HC-SCR reactions over Cu based catalysts. TPR studies revealed the one electron redox behavior of highly dispersed copper oxide on titania support. The effect of inner transitional metal Ce was systematically investigated on the activity of these catalysts. Cerium promoted catalysts showed superior activity than un-promoted catalysts. The promotional effect of Ce is due to the enhanced redox properties of the M-Ce mixtures. The specific surface area of the prepared catalysts was significantly lower than the pure TiO2 support.