Novel technologies for SO{sub x}/NO{sub x} removal from flue gas. Technical report, March 1--May 31, 1995

The goal of this project is to develop a cost-effective low temperature deNO{sub x} process. Work done in previous quarters suggested that the best approach for NO{sub x} removal between 120 C and 150 C was the catalytic oxidation of NO to NO{sub 2}, followed by adsorption of NO{sub 2} with an effective sorbent. The effort this quarter was concentrated on further evaluation of catalysts for NO oxidation. This included more detailed studies of Co/Al{sub 2}O{sub 3} and searching for other active and stable catalysts. The initial increase and subsequent decline in NO oxidation activity of Co/Al{sub 2}O{sub 3} in the presence of SO{sub 2} in the feed was investigated by measuring the dependence of NO oxidation activity on the time of pretreatment in a stream of 0.1% SO{sub 2}, 4% O{sub 2} and 10% H{sub 2}O. The results suggests that NO oxidation might be effected by SO{sub 3} that was formed by the oxidation of SO{sub 2}, and the subsequent decline in activity might be due to the formation of stable inorganic sulfate. Au/Al{sub 2}O{sub 3} was ineffective for NO oxidation. However, a 5 wt.% Au/Co{sub 3}O{sub 4} catalyst (prepared by co-precipitation with Na{sub 2}CO{sub 3} as the precipitating agent) showed high activity. At a W/F of 0.0071 g-min/cc, and a feed composition of 400 ppm NO and 4% O{sub 2}, a NO conversion of 45% to NO{sub 2} at 200 C was obtained, but no activity was observed at 150 C. When H{sub 2}O and SO{sub 2} were included in the feed, NO conversions between 48%--50% were observed between 120 and 150 C. The enhancement of NO oxidation activity by the presence of SO{sub 2} is of particular interest in view of the high sulfur content of the Illinois coal. Furthermore, this activity was stable for the 15 h duration that the catalyst was tested