The Development of Urea-SCR Technology for US Heavy Duty Trucks

Miller, William R.; Klein, John T.; Mueller, Raimund; Doelling, W.; Zuerbig, Juergen

doi:10.4271/2000-01-0190

Cited by 78 publications

(25 citation statements)

References 2 publications

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“…The Selective Catalytic Reduction (SCR) of NOx is achieved by injection of urea into the exhaust system upstream of an appropriate catalyst, thereby providing NH 3 (through the thermal decomposition of urea) as the chemical reductant for a number of reactions which collectively result in the reduction of NOx. To date, this technology has been used primarily for the reduction of NOx from stationary sources [1], though feasibility for vehicle onboard use has been proven by work at multiple vehicle manufacturers [2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Hydrocarbons on the Selective Catalyzed Reduction of NOx over Low and High Temperature Catalyst Formulations

Montreuil

Lambert

2008

SAE Int. J. Fuels Lubr.

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Selective Catalytic Reduction of NOx is a promising technology to enable diesel engines to meet certification under Tier 2 Bin 5 emissions requirements. SCR catalysts for vehicle use are typically zeolitic materials known to store both hydrocarbons and ammonia. Ammonia storage on the zeolite has a beneficial effect on NOx conversion; hydrocarbons however, compete with ammonia for storage sites and may also block access to the interior of the zeolites where the bulk of the catalytic processes take place. This paper presents the results of laboratory studies utilizing surrogate hydrocarbon species to simulate engine-out exhaust over catalysts formulated to operate in both low ( §175-500°C) and high temperature ( §250-600°C) regimes. The effects of hydrocarbon exposure of these individual species on the SCR reaction are examined and observations are made as to necessary conditions for the recovery of SCR activity. An evolution of SCR catalysts is observed, culminating in nearly complete resistance to hydrocarbon inhibition for the low temperature formulations.Further improvement is needed for the high temperature versions.

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Section: Introductionmentioning

confidence: 99%

The Effect of Hydrocarbons on the Selective Catalyzed Reduction of NOx over Low and High Temperature Catalyst Formulations

Montreuil

Lambert

2008

SAE Int. J. Fuels Lubr.

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“…Furthermore, combinations of aftertreatment technologies with the use of various fuel blends have also been reported in some studies to control diesel engine exhaust emissions [6,7]. The urea-SCR system is a well-known and promising technology with the potential to reduce NO x pollutants by over 70% in the European steady-state cycle (ESC) and the European transient cycle (ETC) [8], to reduce both NO x and PM on cold US-Transient and hot US-Transient cycles [9], and to improve the economy of the engine together with the abatement of NO x pollutants [10]. Schaer et al [11] worked on a urea-SCR system for a mobile heavy duty diesel (HDD) engine and reported 80 and 90% NO x conversion efficiencies on ESC and ETC, respectively.…”

Section: Introductionmentioning

confidence: 99%

Impact of a Urea-Selective Catalytic Reduction System on Volatile Organic Compound Emissions from a Diesel Engine

Shah

Jiang

2011

Arab J Sci Eng

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The impact of a vanadium based urea-water selective catalytic reduction (SCR) system on volatile organic compounds emissions from the tailpipe of a diesel engine were studied. The engine was run on an AC electrical dynamometer in an 8-mode steady-state cycle and the gas-phase VOCs were collected in Tenax TA ® tubes from diluted exhaust. Collected samples were extracted by a thermal desorber and analyzed by gas chromatograph-mass spectrometry. It was found that VOCs were in abundance under a full engine load upstream and downstream of the SCR system and that the SCR positively abated these pollutants. Toluene exhibited the maximum relative contribution (RC) to total VOCs at about 43 and 48% upstream and downstream of the SCR, respectively. After toluene, benzene, ethyl benzene, and undecane were the next major contributors, with a similar order of magnitude. Styrene and butyl acetate were the lowest relative contributors. The RC of benzene was reduced but those of toluene and ethyl benzene were increased downstream of the SCR. The VOC conversion rate (CR) exceeded 17% over the catalyst temperature and space velocity ranges 321-435 • C and 27.63 × 10 3 -37.94 × 10 3 h −1 , respectively. The optimum catalyst temperature was 321 • C, giving a maximum CR of 33%. The CR of benzene and styrene revealed maxima during the full-load modes and minima during the lowest-load modes of the cycle. The CR of benzene increased with increasing catalyst temperature.

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“…This highly indicated that current available technologies: Three-way catalyst (TWC) [5][6][7], Urea-SCR (Selective Catalytic Reduction) [8][9][10], Lean NO x Traps (NSR) [11][12][13] and combination thereof still need to be significantly improved since almost all Euro 6 certified diesel cars in the RDE testing emitted on average 8 times higher than the current NOx emission standard [1][2][3] In future, the NO x emission will become more and more stringent. Therefore, effective exhaust emissions after-treatment technologies will be needed.…”

Section: Introductionmentioning

confidence: 99%

Reaction Mechanism Study of the Di-Air System and Selectivity and Reactivity of NO Reduction in Excess O₂

Makkee¹,

Wang²

2017

SAE Int. J. Engines

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We studied the mechanism of NO reduction as well as its selectivity and reactivity in the presence of excess O 2 . Results show that fuel injection and/or pretreatment are important for ceria catalyst reduction and carbon deposition on the catalyst surface. Oxygen defects of reduced ceria are the key sites for the reduction of NO into N 2 . The deposited carbon acts as a buffer reductant, i.e., the oxidation of carbon by lattice oxygen recreates oxygen defects to extend the NO reduction time interval. A small amount of NO showed a full conversion into only N 2 both on the reduced Zr-La doped ceria and reduced Pt-Zr-La doped ceria. Only when the catalyst is oxidised NO is converted into NO 2 .

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The Development of Urea-SCR Technology for US Heavy Duty Trucks

Cited by 78 publications

References 2 publications

The Effect of Hydrocarbons on the Selective Catalyzed Reduction of NOx over Low and High Temperature Catalyst Formulations

The Effect of Hydrocarbons on the Selective Catalyzed Reduction of NOx over Low and High Temperature Catalyst Formulations

Impact of a Urea-Selective Catalytic Reduction System on Volatile Organic Compound Emissions from a Diesel Engine

Reaction Mechanism Study of the Di-Air System and Selectivity and Reactivity of NO Reduction in Excess O₂

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The Development of Urea-SCR Technology for US Heavy Duty Trucks

Cited by 78 publications

References 2 publications

The Effect of Hydrocarbons on the Selective Catalyzed Reduction of NOx over Low and High Temperature Catalyst Formulations

The Effect of Hydrocarbons on the Selective Catalyzed Reduction of NOx over Low and High Temperature Catalyst Formulations

Impact of a Urea-Selective Catalytic Reduction System on Volatile Organic Compound Emissions from a Diesel Engine

Reaction Mechanism Study of the Di-Air System and Selectivity and Reactivity of NO Reduction in Excess O2

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Reaction Mechanism Study of the Di-Air System and Selectivity and Reactivity of NO Reduction in Excess O₂