Low-Temperature NO_x Removal for Flue Gas Cleanup

Abstract

NO x reduction with hydrocarbons is studied at temperatures around 150 °C to develop an easy retrofit NO x removal process to be located downstream of the particulate control device for flue gas cleanup. Acetone is the most active hydrocarbon reductant for NO reduction in the presence of O2 and H2O. At 150 °C, 35% NO reduction was obtained over 5% Cu−2% Ag/PCB. The activity, however, is greatly decreased by the presence of SO2. NO oxidation to NO2 is studied for further improving the NO reduction activity because NO2 is known to be more reactive than NO. Active carbon fibers and PCB active carbon are both active for NO oxidation at low temperature, but the activity decreased with temperature. Ten percent Co3O4/Al2O3 and 5% Au/Co3O4 are not active for NO oxidation in the absence of SO2 and at 150 °C, but are very active in the presence of SO2 and H2O. Five percent Au/Co3O4 is especially stable for NO oxidation to NO2 at temperatures from 120 to 150 °C for more than 15 h.

Insights from Theory on the Relationship Between Surface Reactivity and Gold Atom Release

“…Supported gold nanoparticles can catalyze a wide variety of reactions including the reduction of NO x by hydrocarbons [35,36], the oxidation CH 4 [37,38], CO [39], and propene [40], and the epoxidation of propylene [41]. Gold is extensively used as a substrate for selfassembled monolayers (SAM) [42,43] in materials science [44], as interconnects in electronic devices [45][46][47], as a substrate for conducting polymers in chemical sensors [48], and in many different types of biosensors [49,50].…”

Gold, an alternative to platinum group metals in automobile catalytic converters

“…A method was also described for preparing GNPs supported on CoO x which exhibited high resistance to SO 2 and H 2 O and high catalytic activity for the selective oxidation of NO at a relatively low temperature of 120°C [90]. Interestingly, it was found that SO 2 enhanced the catalytic activity of Au/CoO x in the oxidation of NO [91]. However, development of catalysts with high sulphur resistance remains a challenge.…”

Promotional effects of carbon nanotubes on V2O5/TiO2 for NOX removal

“…Thus, developing active SCR catalysts that can be used at relatively low temperatures (for example below 250 • C) is needed, so that SCR systems could be installed downstream of the desulfurizer and electrostatic precipitator. Low-temperature catalysts contribute to lower energy consumption and help simplify the retrofitting of SCR devices for flue gas cleaning [12].…”