Modeling and analysis of dual-layer NOx storage and reduction and selective catalytic reduction monolithic catalyst

Shakya, Bijesh M.; Harold, Michael P.; Balakotaiah, Vemuri

doi:10.1016/j.cej.2013.10.008

Cited by 30 publications

(11 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the runs performed with 0.2% of hydrogen (Figure 4a), it is observed that the NO x concentration at the outlet increased throughout the cycles, but 1 v/v % of H 2 is enough for the complete reaction with the adsorbed nitrates. The conversion values obtained in these conditions ( Table 3) indicated that total regeneration is possible when working with reducing agent content around five times the stoichiometric value, which is consistent with other authors [50] for higher flowrates and dual-layer systems. For the runs performed with 2.5 v/v % of H 2 (Figure 4c), the amount of H 2 was overestimated for the regeneration of the catalyst and a minimum amount of NO x was detected (as can be observed in the inset).…”

Section: Lean Phasesupporting

confidence: 90%

Hybrid Technology for DeNOxing by LNT-SCR System for Efficient Diesel Emission Control: Influence of Operation Parameters in H2O + CO2 Atmosphere

et al. 2020

View full text Add to dashboard Cite

The behavior and operation parameters were analyzed for the hybrid LNT-SCR (Lean NO x -Trap-Selective Catalytic Reduction) system with advanced catalyst formulations. Pt-Ba-K/Al 2 O 3 was used as an NSR (NO x Storage and Reduction) or LNT catalyst effective in NO x and soot simultaneous removal whereas Cu-SAPO-34 with 2 wt.% of copper inside the structure was the small pore zeolite employed as the SCR catalyst. Under alternating and cyclic wet conditions, feeding volumetric concentrations of 1000 ppm of NO, 3% of O 2 , 1.5% of water, 0.3% of CO 2 , and H 2 as a reductant, the NO x -conversion values were above 95% and a complete mineralization to nitrogen was registered using θ ≤ 3 (20 s of regeneration) and a hydrogen content between 10,000 and 2000 ppm in the whole temperature range tested. An excess of hydrogen fed (above 1% v/v) during the rich phase is unnecessary. In addition, in the low temperature range below 250 • C, the effect is more noticeable due to the further ammonia production and its possible slip. These results open the way to the scale up of the coupled catalytic technologies for its use in real conditions while controlling the influence of the operation map.

show abstract

Section: Lean Phasesupporting

confidence: 90%

Hybrid Technology for DeNOxing by LNT-SCR System for Efficient Diesel Emission Control: Influence of Operation Parameters in H2O + CO2 Atmosphere

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Modelling dual layer and dual zoned LNT and SCR catalysts has shown that the dual layer catalyst operation was much more complex than the dual zoned catalyst, due to diffusion in the different washcoat layers . In comparing dual zone and dual layer LNT‐SCR systems with a focus on understanding differences in performance and the effect of washcoat thickness, the authors found that the dual layer configuration was the better design compared to the zoned configuration when the LNT catalyst generated large amounts of NH 3 . The dual zone configuration was better when small amounts of NH 3 were generated over the LNT, mainly due to the counter‐diffusion of NH 3 from the bottom LNT layer reacting with the top SCR layer.…”

Section: Selective Catalytic Reduction (Scr) and Lean Nox Trap (Lnt) mentioning

confidence: 99%

Heterogeneous catalyst design: Zoned and layered catalysts in diesel vehicle aftertreatment monolith reactors

Hazlett

Epling

2018

Can J Chem Eng

View full text Add to dashboard Cite

There have been ongoing research efforts focused on layering or zoning different washcoats/active metals on the catalysts constituting diesel aftertreatment systems: the diesel oxidation catalyst (DOC), the selective catalytic reduction (SCR) catalyst, the lean NOX trap (LNT), the ammonia slip catalyst (ASC), and the diesel particulate filter (DPF). This review paper aims to shed insight into the state‐of‐the‐art research on catalyst design in this area and how these catalyst designs may evolve to tackle engine emission reductions in the future. First, we discuss the motivation for zoning or layering catalysts and pioneering work on three‐way catalyst (TWC) design for reducing gasoline engine emissions; then, we focus on the catalytic systems used for diesel exhaust aftertreatment. The configuration of the aftertreatment systems for diesel engines generally consist of an oxidation catalyst for hydrocarbon (HC), CO, and NO oxidation (over the DOC), a NOX reduction catalyst (over one or combined SCR/LNT/ASC catalysts), and a particulate matter (PM) filter (using a DPF). The research to date consistently demonstrates that zoning and layering catalyst regions leads to improved performance and/or smaller system volumes required.

show abstract

“…There is no definite agreement in the literature if the dual‐layer NSR–SCR outperforms its sequential NSR+SCR counterpart. From our experiments, we can infer that the NSR+SCR combination provides better features than the dual‐layer NSR–SCR configuration, in agreement with the results simulated by Koltsakis et al., but in contradiction to what was later reported by Shakya et al . Their modelling results showed that the dual‐layer configuration was superior to the sequential double‐monolith.…”

Section: Discussionmentioning

confidence: 99%

“…The SCR catalyst should be highly active and preferably inhibit the adsorption of NH 3 . By using individually calibrated global kinetic models Shakya et al . simulated the behavior of the dual‐layer NSR–SCR monolith catalyst.…”

Section: Coupling Of Nsr and Scr Technologiesmentioning

confidence: 99%

NO_x Storage and Reduction Coupled with Selective Catalytic Reduction for NO_x Removal in Light‐Duty Vehicles

et al. 2018

View full text Add to dashboard Cite

There are two alternative, main technologies for removal of nitrogen oxides (NOx) from vehicle exhaust gases, namely, selective catalytic reduction (SCR) and NOx storage and reduction (NSR). The SCR technology consists of using ammonia (NH3), produced by hydrolysis of urea that is stored into an on‐board tank in the vehicle, to reduce NOx selectively to nitrogen (N2). In the NSR strategy, the conversion of NOx into N2 occurs through a two‐step cyclic operation. During the fuel‐lean stage, the NOx is trapped on the catalyst; then, the engine is switched to a fuel‐rich condition, under which NOx is released and reduced preferentially to N2, although some NH3 can also be produced. The concept of coupling NSR with SCR is based on tuning the operation of the NSR catalyst to produce a controlled amount of NH3, which is stored on the SCR catalyst during the fuel‐rich stage and used to reduce the remaining NOx on the SCR catalyst, placed downstream of the NSR catalyst in a sequential NSR+SCR configuration. Alternatively, the same concept applies to the dual‐layer architecture, which comprises a SCR layer deposited on top of the NSR layer in a single monolith. The internal generation of NH3 in the NSR catalyst avoids the need of external supply from the on‐board tank, but also achieves impressive NOx‐to‐N2 efficiency, apparently allowing zero‐level pollutant emission.

show abstract

Modeling and analysis of dual-layer NOx storage and reduction and selective catalytic reduction monolithic catalyst

Cited by 30 publications

References 37 publications

Hybrid Technology for DeNOxing by LNT-SCR System for Efficient Diesel Emission Control: Influence of Operation Parameters in H2O + CO2 Atmosphere

Hybrid Technology for DeNOxing by LNT-SCR System for Efficient Diesel Emission Control: Influence of Operation Parameters in H2O + CO2 Atmosphere

Heterogeneous catalyst design: Zoned and layered catalysts in diesel vehicle aftertreatment monolith reactors

NO_x Storage and Reduction Coupled with Selective Catalytic Reduction for NO_x Removal in Light‐Duty Vehicles

Contact Info

Product

Resources

About

Modeling and analysis of dual-layer NOx storage and reduction and selective catalytic reduction monolithic catalyst

Cited by 30 publications

References 37 publications

Hybrid Technology for DeNOxing by LNT-SCR System for Efficient Diesel Emission Control: Influence of Operation Parameters in H2O + CO2 Atmosphere

Hybrid Technology for DeNOxing by LNT-SCR System for Efficient Diesel Emission Control: Influence of Operation Parameters in H2O + CO2 Atmosphere

Heterogeneous catalyst design: Zoned and layered catalysts in diesel vehicle aftertreatment monolith reactors

NOx Storage and Reduction Coupled with Selective Catalytic Reduction for NOx Removal in Light‐Duty Vehicles

Contact Info

Product

Resources

About

NO_x Storage and Reduction Coupled with Selective Catalytic Reduction for NO_x Removal in Light‐Duty Vehicles