Molecular decompositions of acetaldehyde and formamide: theoretical studies using Hartree—Fock, Møller-Plesset and density functional theories

MARTELL, JAIME; YU, HENGTAI; Goddard, John P.

doi:10.1080/00268979709482121

Cited by 18 publications

(33 citation statements)

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“…The context of the present work does not deal with the study of kinetics and reaction mechanisms but it can be inferred, based on [2], in accordance with experimental data that there was predominance of the de-carbonation mechanism as compared to hydrogenation as there was an increase in temperature, which agrees to literature [29]. The inlet temperatures in the SCR shown are equal to 272, 377, 459 and 562 °C in ESC modes 9, 3, 4 and 8 respectively.…”

Section: Co Emissions Evaluationsupporting

confidence: 79%

Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

Lourenço¹,

Almeida²,

Glovaski³

2015

Anais Do XXIII Simpósio Internacional De Engenharia Automotiva

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Diesel engine technology has been driven by stringent regulation. To fulfill this demands emission control systems are constantly improving. In this context exhaust gas aftertreatment development assumes an important role however the in-cylinder emissions control is fundamental to comply with future legislations.Among the aftertreatment systems applied to reduce diesel engines combustion products the Selective Catalytic Reduction (SCR), which converts nitrogen oxides, (NO x ) into nitrogen N 2 and water H 2 O via dosing a chemical reducing agent containing ammonia in the exhaust system is an already proven solution for most medium and heavy duty Diesel (MDD and HDD) applications.The current work aims to compare the behavior of different urea and formamide-based reducing agents using a selective catalytic reduction aftertreatment system (ATS) when it comes to NO x reduction. Another purpose of this study in addition to studying the NO x reduction is also to understand the effects or side-effects in other gases like carbon monoxide (CO), carbon dioxide (CO 2 ), hydrocarbon (HC), oxygen (O 2 ), ammonia (NH 3 ) and to discuss in detail the potential of using this alternative reducing agents to comply with EURO VI standards and optimized SCR systems towards increasing their efficiency.Regarding the SCR catalyst system as to NO x reduction it is possible to say that urea-based mixtures are the most efficient ones but on the other hand are also those that present higher values of ammonia slip. The formamide-based mixtures do not present efficiency as significant as the urea-based mixtures but the ammonia slip levels produced by those mixtures are virtually none.With regard to CO and HC emissions the formamide-based mixtures have presented significant increase on the emissions of those two gases while in the urea-based mixtures the values have remained virtually unchanged.

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Section: Co Emissions Evaluationsupporting

confidence: 79%

Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

Lourenço¹,

Almeida²,

Glovaski³

2015

Anais Do XXIII Simpósio Internacional De Engenharia Automotiva

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“…1b. However, if the value k 3 = 1.00 × l0 16 exp(-85.0 kcal/RT) s −1 was assumed, the calculated CH 4 yield was not reproduced as shown in Fig. 1a.…”

Section: Ch 3 Cho Reactionmentioning

confidence: 80%

“…Reactions (15) and (16) (16). These values were used in Table XII. CH 3 CO and CH 2 CHO Radical Reactions…”

Section: Ch 3 Cho Reactionmentioning

confidence: 99%

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Shock‐tube and modeling study of acetaldehyde pyrolysis and oxidation

Yasunaga

Kubo

Hoshikawa

et al. 2007

Int J of Chemical Kinetics

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Pyrolysis and oxidation of acetaldehyde were studied behind reflected shock waves in the temperature range 1000-1700 K at total pressures between 1.2 and 2.8 atm. The study was carried out using the following methods, (1) time-resolved IR-laser absorption at 3.39 µm for acetaldehyde decay and CH-compound formation rates, (2) time-resolved UV absorption at 200 nm for CH 2 CO and C 2 H 4 product formation rates, (3) time-resolved UV absorption at 216 nm for CH 3 formation rates, (4) time-resolved UV absorption at 306.7 nm for OH radical formation rate, (5) time-resolved IR emission at 4.24 µm for the CO 2 formation rate, (6) time-resolved IR emission at 4.68 µm for the CO and CH 2 CO formation rate, and (7) a single-pulse technique for product yields. From a computer-simulation study, a 178-reaction mechanism that could satisfactorily model all of our data was constructed using new reactions, CH 3 CHO (+M) → CH 4 + CO (+M), CH 3 CHO (+M) → CH 2 CO + H 2 (+M),

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“…The B3LYP level 60 with the 6-311G͑d , p͒ basis set has been found useful in determining structure, energy, and vibrational frequencies. 54,61 Geometry optimization for the ground state of reactants and possible products of benzaldehyde and acetophenone systems were carried out at the B3LYP level using the 6-311G͑d , p͒ basis set. UB3LYP/ 6-311G͑d , p͒ was used for radical product candidates such as those involving H, methyl, formyl, acetyl, benzoyl, and phenyl radicals as well as for the triplet state of molecules.…”

Section: A Ground Statementioning

confidence: 99%

Ultrafast electron diffraction: Excited state structures and chemistries of aromatic carbonyls

Park

Feenstra

Zewail

2006

The Journal of Chemical Physics

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The photophysics and photochemistry of molecules with complex electronic structures, such as aromatic carbonyls, involve dark structures of radiationless processes. With ultrafast electron diffraction ͑UED͒ of isolated molecular beams it is possible to determine these transient structures, and in this contribution we examine the nature of structural dynamics in two systems, benzaldehyde and acetophenone. Both molecules are seen to undergo a bifurcation upon excitation ͑S 2 ͒. Following femtosecond conversion to S 1 , the bifurcation leads to the formation of molecular dissociation products, benzene and carbon monoxide for benzaldehyde, and benzoyl and methyl radicals for acetophenone, as well as intersystem crossing to the triplet state in both cases. The structure of the triplet state was determined to be "quinoidlike" of * character with the excitation being localized in the phenyl ring. For the chemical channels, the product structures were also determined. The difference in photochemistry between the two species is discussed with respect to the change in large amplitude motion caused by the added methyl group in acetophenone. This discussion is also expanded to compare these results with the prototypical aliphatic carbonyl compounds, acetaldehyde and acetone. From these studies of structural dynamics, experimental and theoretical, we provide a landscape picture for, and the structures involved in, the radiationless pathways which determine the fate of molecules following excitation. For completeness, the UED methodology and the theoretical framework for structure determination are described in this full account of an earlier communication ͓J. S. Feenstra et al., J. Chem. Phys. 123, 221104 ͑2005͔͒.

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Molecular decompositions of acetaldehyde and formamide: theoretical studies using Hartree—Fock, Møller-Plesset and density functional theories

Cited by 18 publications

References 0 publications

Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

Shock‐tube and modeling study of acetaldehyde pyrolysis and oxidation

Ultrafast electron diffraction: Excited state structures and chemistries of aromatic carbonyls

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