Composition/Performance Evaluation of Lean NO_x Trap Catalysts for Coupling with SCR Technology

Abstract

The washcoat composition and the catalytic properties of two commercially available lean NOx traps (LNTs) were investigated. Both catalysts contained nominally the same NOx storage and catalytic materials but differed strongly in their amount and activity as well as in the composition of their layered washcoat architecture. In lean‐rich cycle experiments under realistic engine‐out gas compositions using a laboratory gas test bench, the LNTs showed comparable NOx storage behavior. At temperatures below 250 °C, the lean phase durations last up to 300 s until 50 % of the NOx storage capacity is reached. The simultaneously calculated NOx storage efficiencies drop rapidly below 35 %, resulting in a high NOx slip. Strong variations were observed in N2O and NH3 selectivity and in CO slip during regeneration of both LNTs caused by the different oxygen storage capacity (OSC), water gas shift (WGS) activity and rhodium distribution in the catalytic layers. Based on the obtained results, proposals were made to optimize the storage and regeneration performance, leading to highly efficient LNT catalysts for coupling with a downstream SCR catalyst.

Impact of unintentionally formed CH2O in oxygenated fuel exhausts on DeNOx-SCR at different NO2/NOx ratios under close to real conditions

“…It is well-known that NO 2 /NO x ratios greater than 50% can lead to an enhanced formation of NH 4 NO 3 on the catalyst surface according to eqn (11). 17,[42][43][44] This situation is often accompanied by catalyst deactivation and sudden decomposition of NH 4 NO 3 at temperatures >200 °C.…”

“…10 One challenge with lean-burn combustion engines, however, is the exhaust gas aftertreatment system required for efficient nitrogen oxides (NO x ) reduction since there is a lack of reducing agent in the exhaust gas of lean-burn engines due to the high oxygen content. [11][12][13] Currently, the most efficient method of reducing NO x from engine exhaust gases is selective catalytic reduction (SCR) technology, in which the nitrogen oxides from the engine react with ammonia as a reducing agent on a zeolite or TiO 2 , V 2 O 5 and WO 3 -based catalyst. [14][15][16] The main SCR reactions are distinguished as follows: eqn (1) is referred to the standard SCR reaction and largely occurs at temperatures around 250 °C and above.…”

Experimental Study on NOx Reduction of Diesel Engine by EGR Coupled with SCR

“…For the study of SCR temperature, Qiu et al 31 carried out the temperature characteristic test of the inlet and outlet of the SCR system on the bench and arranged the SCR carrier temperature sensor to collect the temperature, which provided data support for the subsequent Matlab/Simulink modeling. Schonebaum et al 32 studied the effect of the LNT-SCR combined system on ammonia storage and NO x emissions and the five thermocouples (K-type) in each catalyst to study the temperature distribution of the entire catalyst.…”

Sorption and Reaction of Biomass Derived HC Blends and Their Constituents on a Commercial Pt–Pd/Al2O3 Oxidation Catalyst

“…The Research Cluster of Excellence "The Fuel Science Center" at RWTH Aachen University investigates the production and application of new bio-hybrid fuels from bio-based carbon feedstocks, CO 2 , and hydrogen from renewable electricity generation. The cluster research involves the production pathways from biomass, CO 2 , and H 2 to fuels as well as the usage of these fuels in internal combustion engines and the corresponding exhaust gas aftertreatment [2][3][4]. A variety of different promising fuels for compression and spark ignition engines were identified and investigated for their suitability [5][6][7][8][9][10][11][12].…”