The NOx storage-reduction on PtK/Al2O3 Lean NOx Trap catalyst

Influence of the surface potassium species in Fe–K/Al2O3 catalysts on the soot oxidation activity in the presence of NOx

“…500 ppmv NO, 5% O 2 in Ar were first flown through the monolithic catalyst, keeping temperature constant at 350ºC for 30 minutes. Let us remark here that 350°C has been previously found to be the optimal temperature for nitrate formation upon NO x adsorption on alkali compounds [3], this being the reason for our choice. After this adsorption step, gas flow was changed to 50 mL/min Ar, and temperature was increased from 350 to 650ºC, at 5ºC/min heating rate.…”

“…The wellknown trade-off between soot and NO x formation sets a limit to emission control via engine modifications, thus, after-treatment technologies had to be considered. NO x emission can be controlled by means of Selective Catalytic Reduction (SCR) and NO x Storage-Reduction (NSR) [2,3]. Soot can be retained in a filter that must be periodically regenerated [4][5][6].…”

Simultaneous removal of soot and NO over K- and Ba-doped ruthenium supported catalysts

“…higher than that of typical Pt-Ba/Al 2 O 3 and Pt-K/Al 2 O 3 LNT catalytic systems[66,67]). Adsorbed amounts of NO x near 0.37 mmol/g cat have been estimated at the end of the NO dose, values which are only slightly lower than those reported in literature for typical LNT catalytic systems[67,68].When the NO and O 2 inlet concentrations are switched off (t = 1770 s and 2400 s, respectively) a tail (and a puff in correspondence of O 2 closure) is observed in the NO concentration profile, due to the desorption of weakly adsorbed NO x species [69 and refs herein reported] causing a decrement of roughly 53% in the amount of stored NO x . After NO and oxygen shutoff, hydrogen is admitted to the reactor (t = 3210 s) in order to regenerate the catalyst surface.…”

Enhanced soot combustion over partially substituted hydrotalcite-drived mixed oxide catalysts CoMgAlLaO

“…It is found that the La-substituted catalysts exhibit much larger NO x storage capacities than the La-free sample, especially the sample CMALa 10 which shows the maximal NSC of 300 mol/g. Generally, nitrites and nitrates are arising from the oxidation of NO or NO 2 by surface oxygen species [32,33]. The sample CMALa 10 has the largest BET surface area, the best reducibility and the largest amount of surface lattice oxygen, which determine its highest NO x storage capacity and best oxidation performance for soot combustion.…”