Catalytic Activity of Lime for N₂O Decomposition under Coal Combustion Conditions

Abstract

To understand the contribution of lime to the abatement of N2O emission from fluidized coal combustor, the catalytic activity of the lime for the decomposition of N2O under coal combustion conditions was studied. Lime was active for the catalytic decomposition of N2O, and its activity was stable in the simulated coal combustion flue gas in the absence of SO2 at 800 °C. The catalytic activity of lime was depressed by the presence of CO2, H2O, and SO2. The affect of the presence of SO2 seemed to be most important: the catalytic activity of the lime gradually decreased as the degree of sulfation increased, and the specific surface area decreased with the progression of sulfation. From N2O pretreatment and temperature-programmed desorption studies on the used lime, it was found that two oxygen species and one species of NO desorbed. A surface character change due to sulfation is expected from these gas desorptions. From the relation of the activity to the surface area or the desorption of the gases or both, it was concluded that a decrease in the surface area contributed to the decay of the activity more effectively than the surface character change caused by the sulfation.

Experimental and Kinetic Study on the Influence of CaO on the N2O + NH3 + O2 System

“…The presence of the adsorption band of nitrate verified the production of calcium nitrate in the previous study. 16 The DRIFTS experiment showed that the main adsorption species of N 2 O on the CaO surface was cis-dimer nitroso. The two N atoms in N 2 O interacted with the coordinately unsaturated lattice oxygen on the CaO surface 19,20 to form the adsorbed N 2 O molecule, as shown in eq 6.…”

“…NH 3 dissociation to NH 2 was the rate-controlling step of NH 3 conversion and occurred through eqs 9 and 10. Thus, the reaction rate of NH 3 can be expressed as eq16 …”

Simultaneous catalytic reduction of N2O and NOx produced in a fluidized bed incineration of sewage sludge

“…Secondly, while the conversion from HCN to NO increases, that to N 2 O decreases with increasing temperature . The emission of N 2 O is mostly controlled by operating conditions such as the combustion temperature and the choice of sorbent for capturing SO x . In contrast to chemical plants for N 2 O abatement during nitric acid production, the catalytic abatement technology for N 2 O has not been developed yet for fluidized bed combustion.…”

“…8 Th e emission of N 2 O is mostly controlled by operating conditions such as the combustion temperature 4 and the choice of sorbent for capturing SO x . 9,10 In contrast to chemical plants for N 2 O abatement during nitric acid production, 11 the catalytic abatement technology for N 2 O has not been developed yet for fl uidized bed combustion. Santiago et al 12 suggested that a promising zeolite catalyst (Fe/ZSM-5) could be installed in the fl uidized bed combustion system operated within 530-830 °C for N 2 O direct decomposition.…”

Catalytic reduction of N2O with CH4 and C3H6 over Ag–Rh/Al2O3 bimetallic catalyst in the presence of oxygen

“…In contrast, CaO was active for the direct decomposition of N 2 O in spite of the presence of oxygen and methane. A serious problem related to the practical applications of CaO in real exhaust gases is the deactivation due to the formation of CaSO 4 in the presence of SO 2 20. On the other hand, in several cases, the presence of SO 2 has a promotional effect on the deNO x activity of silver catalysts under lean‐burn conditions 8, 9…”