Beneficial and problematic interactions between NOx trapping materials and carbonaceous particulate matter

Abstract

due to a co-generated exotherm. However, it has been noted that the presence of soot prevents NO x traps from employing their full trapping capacity.

The effect of C(s) on the trapping of NOx onto Pt/Ba/Al2O3 catalysts

“…Furthermore, it has been reported that the presence of a NSR system improves particulate removal from diesel exhausts [1,[18][19][20]. Previously, [21] we have shown that the reason for this improved activity is related to the increased transient concentration of NO x present during regeneration of the NSR material rather than to any inherent catalytic activity in the components of the NSR material.…”

“…In that case the rate of NO 2 assisted soot combustion would be lower. Reference [21] shows (albeit comparing T= 300 °C and 400 °C) an order of magnitude increase in the production of CO 2 The adsorbed NO x also appears to be somewhat less stable (in terms of T initial and T max of the evolved NO TPD profiles) in the presence of soot. We ascribe this to any NO x adsorbed close to a C (s) particle reacting as the temperature is raised, thereby getting reduced to less stable NO-containing species and desorbing.…”

“…This in turn has an effect on the fuel efficiency of any vehicle that operates such a system. While several groups have studied the effect of NO x (and NO x trapping materials) on soot combustion [18][19][20][21][22][23] very few have studied systematically the reverse interactions, i.e. the effect of soot on the activity and capacity of a NO x trap.…”

Structured Catalysts for Soot Combustion for Diesel Engines

“…Once it is saturated, the alkali-metal trap should be regenerated by running the engine in rich conditions or by adding fuel into the exhaust stream. However, in another work [16] it is reported that the presence of soot particles prevents NOx traps from employing their full trapping capacity, which could result in a lack of efficiency of the DPNR Toyota technology.…”

Attempts at an in situ Raman study of ceria/zirconia catalysts in PM combustion

“…Because of the detrimental effects on human health as well as the global and local environment the remediation of Particulate Matter (PM) formed in diesel and gasoline combustion chambers is an area of considerable research activity both within our group and worldwide [1][2][3][4][5][6][7][8][9][10]. The use of catalysts to promote the oxidation of PM has resulted in much research in technologies such as the diesel particulate filter (DPF) [3][4] and the diesel particulate NO x reduction systems (DPNR) [9][10].…”