HCN synthesis from NH3 and CH4 on Pt at atmospheric pressure

Suárez, M.P.

doi:10.1016/0021-9517(86)90054-0

Cited by 12 publications

(7 citation statements)

References 5 publications

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“…HCN has been reported previously in vehicle exhaust (Bradow and Stump, 1977;Keirns and Holt, 1978;Cadle et al, 1979;Garbe, 1979, 1980;Karlsson, 2004;Baum et al, 2007;Moussa et al, 2016). It may form over the catalytic converters in the vehicle emission control systems (Voorhoeve et al, 1975;Suárez and Löffler, 1986;Baum et al, 2007). A recent study for Toronto reported comparable HCN mixing-ratio values (Moussa et al, 2016).…”

Section: Hcnmentioning

confidence: 71%

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

et al. 2017

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Abstract. Traffic emissions contribute significantly to urban air pollution. Measurements were conducted over Highway 401 in Toronto, Canada, with a long-path Fourier transform infrared (FTIR) spectrometer combined with a suite of micrometeorological instruments to identify and quantify a range of air pollutants. Results were compared with simultaneous in situ observations at a roadside monitoring station, and with output from a special version of the operational Canadian air quality forecast model (GEM-MACH). Elevated mixing ratios of ammonia (0-23 ppb) were observed, of which 76 % were associated with traffic emissions. Hydrogen cyanide was identified at mixing ratios between 0 and 4 ppb. Using a simple dispersion model, an integrated emission factor of on average 2.6 g km −1 carbon monoxide was calculated for this defined section of Highway 401, which agreed well with estimates based on vehicular emission factors and observed traffic volumes. Based on the same dispersion calculations, vehicular average emission factors of 0.04, 0.36, and 0.15 g km −1 were calculated for ammonia, nitrogen oxide, and methanol, respectively.

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Section: Hcnmentioning

confidence: 71%

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

et al. 2017

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“…However, there is some information available for pathways of HCN formation in other exhaust gas cleaning processes. Thus, Voorhoeve et al reported that HCN is formed from NO, CO, and H 2 at 400−800 °C on a Pt-containing three-way catalyst (eq 17), 27 while Suaŕez and Lofer postulated HCN formation from NH 3 and CH 4 (eq 18) on catalysts containing platinum, 28 rhodium, or iridium. 29 Cant et al have found that HCN can be formed by dehydration of formamide (eq 19), which they used as the reducing agent instead of NH 3 in SCR of NO on Co/Cu-ZSM-5 catalysts.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Effect of Formaldehyde in Selective Catalytic Reduction of NO_x by Ammonia (NH₃-SCR) on a Commercial V₂O₅-WO₃/TiO₂ Catalyst under Model Conditions

Ngo

Vuong

Atia

et al. 2020

Environ. Sci. Technol.

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The impact of formaldehyde (HCHO, formed in vehicle exhaust gases by incomplete combustion of fuel) on the performance of a commercial V 2 O 5 -WO 3 /TiO 2 catalyst in NH 3 -SCR of NO x under dry conditions has been analyzed in detail by catalytic tests, in situ FTIR and transient studies using temporal analysis of products (TAP). HCHO reacts preferentially with NH 3 to a formamide (HCONH 2 ) surface intermediate. This deprives NH 3 partly from its desired role as a reducing agent in the SCR and diminishes NO conversion and N 2 selectivity. Between 250 and 400 °C, HCONH 2 decomposes by dehydration (major pathway) and decarbonylation (minor pathway) to liberate toxic HCN and CO, respectively. HCN was proven to be oxidized by lattice oxygen of the catalyst to CO 2 and NO, which enters the NH 3 -SCR reaction.

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“…The oxidation of ammonia for nitric acid production 53 is conducted optimally at 810−940 °C with a Pt catalyst, depending on the pressure and NH 3 volume ratio. Other examples include solid oxide fuel cells 54 (500−1000 °C on Ni), carbon nanotube formation 55 (750 °C on Fe), and the synthesis of hydrocyanic acid from ammonia and methane 56 (1200 °C on Pt). Moreover, since the reactions take place at the interfaces between the gas and the solid phase, for strong exothermic reactions such as Fischer−Tropsch and Haber-Bosch processes, much reaction heat is released at the interface (i.e., the catalyst surface).…”

Section: ■ Introductionmentioning

confidence: 99%

Surface Activation of Transition Metal Nanoparticles for Heterogeneous Catalysis: What We Can Learn from Molecular Dynamics

2018

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Many heterogeneous reactions catalyzed by nanoparticles occur at relatively high temperatures, which may modulate the surface morphology of nanoparticles during reaction. Inspired by the discovery of dynamic formation of active sites on gold nanoparticles, we explore theoretically the nature of the highly mobile atoms on the surface of nanoparticles of various sizes for 11 transition metals. Using molecular dynamics simulations, on a 3 nm Fe nanoparticle as an example, the effect of surface premelting and overall melting on the structure and physical properties of the nanoparticles is analyzed. When the nanoparticle is heated up, the atoms in the outer shell appear amorphous already at 900 K. Surface premelting is reached at 1050 K, with more than three liquid atoms, based on the Lindemann criterion. The activated atoms may transfer their extra kinetic energy to the rest of the nanoparticle and activate other atoms. The dynamic studies indicate that the number of highly mobile atoms on the surface increases with temperature. Those atoms with a high Lindemann index, usually located on the edges or vertices, attain much higher kinetic energy than other atoms and potentially form different active sites in situ. When the temperature passes the surface premelting temperature, a drastic change in the coordination number (SCN) of the surface atoms occurs, with attendant dramatic broadening of the distribution of the SCN, suppling active sites with more diverse atomic coordination numbers. The electronic density of states of a nanoparticle tends to “equalize”, due to the breaking of the translational symmetry of the atoms in the nanoparticle, and the d-band center of the nanoparticle moves further away from the Fermi level as the temperature increases. Besides Au, other nanoparticles of the transition metals, such as Pt, Pd, and Ag, may also have active sites easily formed in situ.

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HCN synthesis from NH3 and CH4 on Pt at atmospheric pressure

Cited by 12 publications

References 5 publications

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

Effect of Formaldehyde in Selective Catalytic Reduction of NO_x by Ammonia (NH₃-SCR) on a Commercial V₂O₅-WO₃/TiO₂ Catalyst under Model Conditions

Surface Activation of Transition Metal Nanoparticles for Heterogeneous Catalysis: What We Can Learn from Molecular Dynamics

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HCN synthesis from NH3 and CH4 on Pt at atmospheric pressure

Cited by 12 publications

References 5 publications

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

Effect of Formaldehyde in Selective Catalytic Reduction of NOx by Ammonia (NH3-SCR) on a Commercial V2O5-WO3/TiO2 Catalyst under Model Conditions

Surface Activation of Transition Metal Nanoparticles for Heterogeneous Catalysis: What We Can Learn from Molecular Dynamics

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Effect of Formaldehyde in Selective Catalytic Reduction of NO_x by Ammonia (NH₃-SCR) on a Commercial V₂O₅-WO₃/TiO₂ Catalyst under Model Conditions