scholarly journals Analysis of Ion-Exchanged ZSM-5, BEA, and SSZ-13 Zeolite Trapping Materials under Realistic Exhaust Conditions

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 449
Author(s):  
Todd J. Toops ◽  
Andrew J. Binder ◽  
Pranaw Kunal ◽  
Eleni A. Kyriakidou ◽  
Jae-Soon Choi
Keyword(s):  
Nox Reduction ◽  
Nox Storage ◽  
Minimal Effect ◽  
Hydrothermal Aging ◽  
Evaluation Protocol ◽  
Nox Adsorption ◽  
Moderate Effect

An industry-defined evaluation protocol was used to evaluate the hydrocarbon trapping (HCT) and passive NOx adsorption (PNA) potential for BEA, ZSM-5, and SSZ-13 zeolites with ion-exchanged Pd or Ag. All materials underwent 700 °C degreening prior to exposure to an industry-derived protocol gas stream, which included NOx, ethylene, toluene, and decane as measured trapping species as well as common exhaust gasses CO, H2O, O2, CO2, and H2. Evaluation showed that BEA and ZSM-5 zeolites were effective at trapping hydrocarbons (HCs), as saturation was not achieved after 30 min of exposure. SSZ-13 also stored HCs but was only able to adsorb 20–25% compared to BEA and ZSM-5. The presence of Ag or Pd did not impact the overall HC uptake, particularly in the first three minutes. Pd/zeolites had significantly lower THC release temperature, and it aided in the conversion of the released HCs; Ag only had a moderate effect in both areas. With respect to NOx adsorption, the level of uptake was much lower than HCs on all samples, and Ag or Pd was necessary with Pd being notably more effective. Additionally, only Pd/ZSM-5 and Pd/SSZ-13 continue to store a portion of the NOx above 200 °C, which is critical for downstream selective catalytic NOx reduction (SCR). Hydrothermal aging (800 °C for 50 h) of a subset of the samples were performed: BEA, Pd/BEA, ZSM-5, Pd/ZSM-5, and Pd/SSZ-13. There was a minimal effect on the HC storage, ~10% reduction in capacity with no effect on release temperature; however, only Pd/SSZ-13 showed significant NOx storage after aging.

Optimization of Mode Switching Timing Control for a Lean-Burn Gasoline Engine With a Prototype Passive SCR System

2018 ◽  
Author(s):  
Dakota Strange ◽  
Pingen Chen ◽  
Vitaly Y. Prikhodko ◽  
James E. Parks
Keyword(s):  
Gasoline Engine ◽  
Nox Reduction ◽  
Cost Effective ◽  
Nox Storage ◽  
Mode Switching ◽  
Timing Control ◽  
Lean Burn ◽  
Gasoline Engines ◽  
Effective Manner ◽  
Passive Scr

Passive selective catalytic reduction (SCR) has emerged as a promising NOx reduction technology for highly-efficient lean-burn gasoline engines to meet stringent NOx emission regulation in a cost-effective manner. In this study, a prototype passive SCR which includes an upstream three-way catalyst (TWC) with added NOx storage component, and a downstream urealess SCR catalyst, was investigated. Engine experiments were conducted to investigate and quantify the dynamic NOx storage/release behaviors as well as dynamic NH3 generation behavior on the new TWC with added NOx storage component. Then, the lean/rich mode-switching timing control was optimized to minimize the fuel penalty associated with passive SCR operation. Simulation results show that, compared to the baseline mode-switching timing control, the optimized control can reduce the passive SCR-related fuel penalty by 6.7%. Such an optimized mode-switching timing control strategy is rather instrumental in realizing significant fuel efficiency benefits for lean-burn gasoline engines coupled with cost-effective passive SCR systems.

scholarly journals Identification of Ru/Ceria Among Single Atom Ceria Catalysts as a Stable and Superior Material for Abatement of Diesel and Gasoline Engine Pollutants

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Nicholas R. Jaegers ◽  
Libor Kovarik ◽  
Jinshu Tian ◽  
Xavier Isidro Pereira Hernandez ◽  
...  
Keyword(s):  
Gasoline Engine ◽  
No Oxidation ◽  
Oxidation Catalyst ◽  
Single Atom ◽  
Hydrothermal Aging ◽  
Gasoline Engines ◽  
Nox Adsorption ◽  
Ceria Catalysts ◽  
Better Than ◽  
Three Way Catalysis

Atomically dispersed transition metals (Ru, Pd and Pt) have been prepared on CeO<sub>2</sub> and evaluated for NOx/CO abatement applications for diesel and gasoline engines, such as low temperature passive NOx adsorption (PNA), NO and CO oxidation, and three-way-catalysis (TWC). 0.5 wt% Ru/CeO<sub>2</sub> catalyst (Ru is ~27 and ~7 times cheaper than Rh and Pd) shows remarkable PNA performance, better than 1 wt% Pd/Zeolite: it achieves 100% removal of NOx during vehicle cold start. FTIR measurements reveal the formation of stable Ru(NO) complexes as well spill-over of NO to CeO<sub>2</sub> surface via the Ru-O-Ce shuttle, explaining high NO storage. Notably, Ru/ceria survives hydrothermal aging at 750 ⁰C without loss of PNA capacity. It is also a robust NO oxidation catalyst, considerably more active than Pt or Pd/CeO<sub>2</sub>. Expanding the repertoire of Ru/CeO<sub>2</sub> catalytic applications, we further find 0.1 and 0.5 wt% Ru/CeO<sub>2</sub> to be excellent TWC catalysts, rivaling best single-atom Rh supported materials. Our study pushes the frontier of precious metal atom economy for environmental catalysis from uber expensive Rh/Pd/Pt to more sustainable cheaper Ru and highlights the utility of single-atom catalysts for industrially relevant applications.

Effect of hydrothermal aging on NOx reduction performance for Sb–V–CeO2/TiO2 catalyst

2018 ◽  
Vol 44 (11) ◽  
pp. 6803-6829 ◽  
Author(s):  
Young Eun Jeong ◽  
Pullur Anil Kumar ◽  
Heon Phil Ha ◽  
Kwan-young Lee
Keyword(s):  
Nox Reduction ◽  
Hydrothermal Aging ◽  
Tio2 Catalyst

scholarly journals Perovskite-Based Catalysts as Efficient, Durable, and Economical NOx Storage and Reduction Systems

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 208
Author(s):  
Jon A. Onrubia-Calvo ◽  
Beñat Pereda-Ayo ◽  
Juan R. González-Velasco
Keyword(s):  
Removal Efficiency ◽  
Diesel Engines ◽  
Nox Reduction ◽  
Platinum Group Metals ◽  
Nox Storage ◽  
Automotive Application ◽  
Nox Removal ◽  
Nox Storage And Reduction ◽  
Nox Storage Capacity ◽  
Nox Removal Efficiency

Diesel engines operate under net oxidizing environment favoring lower fuel consumption and CO2 emissions than stoichiometric gasoline engines. However, NOx reduction and soot removal is still a technological challenge under such oxygen-rich conditions. Currently, NOx storage and reduction (NSR), also known as lean NOx trap (LNT), selective catalytic reduction (SCR), and hybrid NSR–SCR technologies are considered the most efficient control after treatment systems to remove NOx emission in diesel engines. However, NSR formulation requires high platinum group metals (PGMs) loads to achieve high NOx removal efficiency. This requisite increases the cost and reduces the hydrothermal stability of the catalyst. Recently, perovskites-type oxides (ABO3) have gained special attention as an efficient, economical, and thermally more stable alternative to PGM-based formulations in heterogeneous catalysis. Herein, this paper overviews the potential of perovskite-based formulations to reduce NOx from diesel engine exhaust gases throughout single-NSR and combined NSR–SCR technologies. In detail, the effect of the synthesis method and chemical composition over NO-to-NO2 conversion, NOx storage capacity, and NOx reduction efficiency is addressed. Furthermore, the NOx removal efficiency of optimal developed formulations is compared with respect to the current NSR model catalyst (1–1.5 wt % Pt–10–15 wt % BaO/Al2O3) in the absence and presence of SO2 and H2O in the feed stream, as occurs in the real automotive application. Main conclusions are finally summarized and future challenges highlighted.

scholarly journals Improved NOx Storage/Release Properties of Ceria-Based Lean NOx Trap Compositions with MnOx Modification

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2127 ◽  
Author(s):  
Marcos Schöneborn ◽  
Thomas Harmening ◽  
Javier Giménez-Mañogil ◽  
Juan Carlos Martínez-Munuera ◽  
Avelina García-García
Keyword(s):  
Storage Capacity ◽  
Nox Storage ◽  
Pt Catalyst ◽  
Lean Nox Trap ◽  
Incipient Wetness Impregnation ◽  
Nox Trap ◽  
Remarkable Effect ◽  
Nox Storage Capacity ◽  
Nox Adsorption ◽  
Lean Nox

Ceria/spinel-based lean NOx trap compositions with and without barium were modified with MnOx via incipient wetness impregnation. The effect of the MnOx layer on the aged materials (850 °C) as to the NOx storage and release properties was investigated via NOx adsorption (500 ppm NO/5% O2/balance N2) carried out at 300 °C in a dual-bed with a 1% Pt/Al2O3 catalyst placed upstream of the samples to generate sufficient amounts of NO2 required for efficient NOx storage. Subsequent temperature programmed desorption (TPD) experiments were carried out under N2 from 300 °C to 700 °C. The addition of MnOx to the barium free composition led to a slightly reduced NOx storage capacity but all of the ad-NOx species were released from this material at significantly lower temperatures (ΔT ≈ 100 °C). The formation of a MnOx layer between ceria/spinel and barium had a remarkable effect on ageing stability as the formation of BaAl2O4 was suppressed in favour of BaMnO3. The presence of this phase resulted in an increased NOx storage capacity and lower desorption temperatures. Furthermore, NOx adsorption experiments carried out in absence of the Pt-catalyst also revealed an unexpected high NOx storage ability at low NO2/NO ratios, which could make this composition suitable for various lean NOx trap catalysts (LNT) related applications.

Impact of dopants on the sulfation, desulfation and NOx reduction performance of Ba-based NOx storage-reduction catalysts☆

2011 ◽  
Vol 160 (1) ◽  
pp. 131-136 ◽  
Author(s):  
Todd J. Toops ◽  
Nathan A. Ottinger ◽  
Chengdu Liang ◽  
Josh A. Pihl ◽  
E. Andrew Payzant
Keyword(s):  
Nox Reduction ◽  
Nox Storage ◽  
Nox Storage Reduction ◽  
Nox Storage Reduction Catalysts ◽  
Reduction Catalysts

A Laboratory Study of NOX Reduction During the Rich Operating Period Over a NOX Storage Catalyst

1999 ◽  
Author(s):  
S. Fendeleur ◽  
C. Pope ◽  
H. Mahzoul ◽  
J-F. Brilhac ◽  
P. Gilot ◽  
...  
Keyword(s):  
Laboratory Study ◽  
Nox Reduction ◽  
Nox Storage ◽  
Operating Period ◽  
Nox Storage Catalyst ◽  
The Rich ◽  
Storage Catalyst

scholarly journals Increasing Al-Pair Abundance in SSZ-13 Zeolite via Zeolite Synthesis in the Presence of Alkaline Earth Metal Hydroxide Produces Hydro-Thermally Stable Cobalt and Pd-SSZ-13 Materials for Pollutant Abatement Applications

2021 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Miroslaw A. Derewinski ◽  
Nicholas R. Jaegers ◽  
Daria Boglaienko ◽  
Xavier Isidro Pereira Hernandez ◽  
...  
Keyword(s):  
Alkaline Earth ◽  
Air Flow ◽  
Earth Metal ◽  
Ambient Air ◽  
Critical Issue ◽  
Alkaline Earth Metal ◽  
Thermally Stable ◽  
Hydrothermal Aging ◽  
Nox Adsorber ◽  
Nox Adsorption

<div> <p>We show that replacing alkaline (NaOH) for alkaline-earth metal (Sr(OH)<sub>2 </sub>as an example) in the synthesis of SSZ-13 zeolite with Si/Al~10 produces SSZ-13 zeolite material with novel, advantageous properties. Its NH<sub>4</sub>-form ion-exchanges higher amount of Co(II) ions than the conventional one: this is the consequence of increased number of Al pairs in the structure induced by the +2 charge of Sr(II) cations in the synthesis gel that force two charge-compensating AlO<sub>4</sub><sup>-</sup> motives to be closer together. We characterize the +2 state of Co(II) ions in these materials with infra-red spectroscopy and XANES measurements. They can be used for NOx pollutant adsorption from ambient air: the ones derived from SSZ-13 with higher Al pair content contain more cobalt(II) and thus, perform better as ambient-air NOx adsorbers before reaching full saturation capacity. Notably, Co(II)/SSZ-13 material with increased number of Al pairs is significantly more hydrothermally stable than its NaOH-derived analogue. Loading 1.7 wt% Pd into Co-SSZ-13 synthesized in the presence of Sr(II) produces a passive NOx adsorber (PNA) material that can be used for NOx adsorption from simulated diesel engine exhaust. The critical issue for these applications is hydrothermal stability of Pd-zeolites. Pd/SSZ-13 synthesized in NaOH media loses most of its PNA capacity after ~800 ⁰C hydrothermal aging in the flow of air and steam (10 hours in 10% H<sub>2</sub>O/air flow). The 1.7 wt% Pd/Co/SSZ-13 material with Si/Al ~10 does not lose its PNA capacity after extremely harsh aging at 850 and 900 ⁰C (10 hours in 10% H<sub>2</sub>O/Air flow) and loses only ~55% capacity after hydrothermal aging at 930 ⁰C. It shows considerably enhanced stability compared with previous record for Pd/FER, Pd/SSZ-39 and Pd/BEA materials that could survive hydrothermal aging no higher than 820 ⁰C. We herein reveal a new, simple, and scalable strategy for making remarkably (hydro)thermally stable metal-zeolite materials/catalysts with a number of useful applications. </p> </div>

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