PGM based catalysts for exhaust-gas after-treatment under typical diesel, gasoline and gas engine conditions with focus on methane and formaldehyde oxidation

Gremminger, Andreas; Pihl, Josh A.; Casapu, Maria; Grunwaldt, Jan‐Dierk; Toops, Todd J.; Deutschmann, Olaf

doi:10.1016/j.apcatb.2019.118571

Cited by 66 publications

(65 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…All in all, the poor activity of noble‐metal‐based catalysts to oxidize formaldehyde at low temperatures to CO 2 under realistic reaction conditions (i.e., long‐term run and SO 2 presence) and also the practically impossible complete conversion of formaldehyde even at high temperatures due to the too low diffusion rate, result in an inevitable exposure of the NO x ‐removal catalysts to HCHO emissions. In this context, this study uncovers the formation of HCN as a potential major hazard during the application of conventional NH 3 ‐SCR catalysts for NO x removal in the exhaust of NG engines.…”

Section: Figuresupporting

confidence: 91%

“…As shown by recent studies, fresh noble metal‐based oxidation catalysts are able to significantly convert formaldehyde. However, when using more complex gas mixtures or upon catalyst ageing (i.e., SO 2 poisoning or field aging) the activity significantly decreases, particularly at low temperatures. Furthermore, complete conversion is virtually impossible to achieve at high gas hourly space velocity with a typical catalyst length due to the low diffusion rate of formaldehyde from the gas phase to the catalyst surface, especially at low concentrations …”

Section: Figurementioning

confidence: 99%

See 1 more Smart Citation

Emission of Toxic HCN During NO_x Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

et al. 2020

Self Cite

View full text Add to dashboard Cite

Reducing greenhouse gas and pollutant emissions is one of the most stringent priorities of our society to minimize their dramatic effects on health and environment. Natural gas (NG) engines, in particular at lean conditions, emit less CO2 in comparison to combustion engines operated with liquid fuels but NG engines still require emission control devices for NOx removal. Using state‐of‐the‐art technologies for selective catalytic reduction (SCR) of NOx with NH3, we evaluated the interplay of the reducing agent NH3 and formaldehyde, which is always present in the exhaust of NG engines. Our results show that a significant amount of highly toxic hydrogen cyanide (HCN) is formed. All catalysts tested partially convert formaldehyde to HCOOH and CO. Additionally, they form secondary emissions of HCN due to catalytic reactions of formaldehyde and its oxidation intermediates with NH3. With the present components of the exhaust gas aftertreatment system the HCN emissions are not efficiently converted to non‐polluting gases. The development of more advanced catalyst formulations with improved oxidation activity is mandatory to solve this novel critical issue.

show abstract

Section: Figuresupporting

confidence: 91%

Section: Figurementioning

confidence: 99%

Emission of Toxic HCN During NO_x Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Moreover, its advantageous hydrogen-to-carbon ratio also makes methane a highly attractive energy carrier, hence natural gas (NG) engines could play an important role in the near future [3]. Despite high fuel efficiency and comparatively low raw emissions, efficient exhaust gas after-treatment systems of natural gas engines are indispensable nowadays, especially in the mobility sector [4,5]. Emissions of CH 4 , with over 20 times higher global warming potential compared to CO 2 [6], need to be avoided under any circumstances.…”

Section: Introductionmentioning

confidence: 99%

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

et al. 2020

Self Cite

View full text Add to dashboard Cite

Water, which is an intrinsic part of the exhaust gas of combustion engines, strongly inhibits the methane oxidation reaction over palladium oxide-based catalysts under lean conditions and leads to severe catalyst deactivation. In this combined experimental and modeling work, we approach this challenge with kinetic measurements in flow reactors and a microkinetic model, respectively. We propose a mechanism that takes the instantaneous impact of water on the noble metal particles into account. The dual site microkinetic model is based on the mean-field approximation and consists of 39 reversible surface reactions among 23 surface species, 15 related to Pd-sites, and eight associated with the oxide. A variable number of available catalytically active sites is used to describe light-off activity tests as well as spatially resolved concentration profiles. The total oxidation of methane is studied at atmospheric pressure, with space velocities of 160,000 h−1 in the temperature range of 500–800 K for mixtures of methane in the presence of excess oxygen and up to 15% water, which are typical conditions occurring in the exhaust of lean-operated natural gas engines. The new approach presented is also of interest for modeling catalytic reactors showing a dynamic behavior of the catalytically active particles in general.

show abstract

“…Wie aktuelle Studien zeigen, können frische Oxidationskatalysatoren auf Edelmetallbasis Formaldehyd signifikant umwandeln. Bei Verwendung komplexerer Gasgemische oder bei Alterung des Katalysators (z. B.…”

Section: Figureunclassified

“…Insgesamt führt die geringe Aktivität von Edelmetallkatalysatoren bezüglich der Oxidation von Formaldehyd zu CO 2 bei niedrigen Temperaturen unter realitätsnahen Reaktionsbedingungen (z. B. bei Langzeitbetrieb in Präsenz von SO 2 ) und die unvollständige Umsetzung des Formaldehyds zu einer unvermeidlichen Belastung der NO x ‐Entfernungskatalysatoren durch HCHO‐Emissionen.…”

Section: Figureunclassified

Freisetzung von toxischem HCN bei der Stickoxidreduktion mittels NH₃‐SCR in mager betriebenen Erdgasmotoren

et al. 2020

Self Cite

View full text Add to dashboard Cite

Die Reduzierung der Emissionen von Treibhausgasen und gesundheitsgefährdenden Schadstoffen ist eines der wichtigsten Ziele unserer Industriegesellschaft. Erdgasmotoren sind insbesondere bei magerem Betrieb attraktiv, da sie weniger CO2 ausstoßen als Verbrennungsmotoren, die mit flüssigen Kraftstoffen betrieben werden. Sie benötigen allerdings ein katalytisches Kontrollsystem, um Stickoxide (NOx) aus dem Abgas zu entfernen. Hier haben wir das Zusammenspiel der aktuellen Technologie zur Stickoxidreduktion, die selektive katalytische Reduktion (SCR) mittels NH3, und Formaldehyd, einer schädlichen Emission in Erdgasmotoren, untersucht. Bei der NOx Entfernung werden beachtliche Mengen an toxischem Cyanwasserstoff (HCN) gebildet. Alle getesteten Katalysatoren wandeln Formaldehyd teilweise in HCOOH und CO um. Zusätzlich werden Sekundäremissionen von HCN über die katalytische Reaktion von Formaldehyd und dessen Oxidationsintermediaten mit NH3 beobachtet. Da die HCN Emissionen mit den derzeitigen Komponenten nicht effizient in schadstofffreie Gase umgewandelt werden können, ist die Entwicklung von Katalysatoren mit einer gesteigerten Oxidationsaktivität nötig, um dieses kritische Problem zu lösen.

show abstract

PGM based catalysts for exhaust-gas after-treatment under typical diesel, gasoline and gas engine conditions with focus on methane and formaldehyde oxidation

Cited by 66 publications

References 74 publications

Emission of Toxic HCN During NO_x Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

Emission of Toxic HCN During NO_x Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

Freisetzung von toxischem HCN bei der Stickoxidreduktion mittels NH₃‐SCR in mager betriebenen Erdgasmotoren

Contact Info

Product

Resources

About

PGM based catalysts for exhaust-gas after-treatment under typical diesel, gasoline and gas engine conditions with focus on methane and formaldehyde oxidation

Cited by 66 publications

References 74 publications

Emission of Toxic HCN During NOx Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

Emission of Toxic HCN During NOx Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

Freisetzung von toxischem HCN bei der Stickoxidreduktion mittels NH3‐SCR in mager betriebenen Erdgasmotoren

Contact Info

Product

Resources

About

Emission of Toxic HCN During NO_x Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

Emission of Toxic HCN During NO_x Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

Freisetzung von toxischem HCN bei der Stickoxidreduktion mittels NH₃‐SCR in mager betriebenen Erdgasmotoren