NOx self-inhibition in selective catalytic reduction with urea (ammonia) over a Cu-zeolite catalyst in diesel exhaust

Xu, Lifeng; McCabe, Robert W.; Hammerle, R. H.

doi:10.1016/s0926-3373(02)00074-7

Cited by 33 publications

(19 citation statements)

References 20 publications

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“…Results have shown that urea is a slightly more effective reductant when using a CUzeolite catalyst (Xu, et al, 2002). However, under steady state low temperature reaction conditions using ammonia performed better which was assumed to occur because of the possible incomplete hydrolysis of urea to ammonia below 250°C (Xu, et al, 2002).…”

Section: Selective Catalytic Reduction (Scr)mentioning

confidence: 99%

“…However, under steady state low temperature reaction conditions using ammonia performed better which was assumed to occur because of the possible incomplete hydrolysis of urea to ammonia below 250°C (Xu, et al, 2002). SCR has been shown to lower NOx as much as 40% in a light-duty truck application (Lambert, et al, 2006).…”

Section: Selective Catalytic Reduction (Scr)mentioning

confidence: 99%

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Combustion and emissions characteristics of compression-ignition engine using dual ammonia-diesel fuel

Reiter

Kong

2011

Fuel

515

132

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Section: Selective Catalytic Reduction (Scr)mentioning

confidence: 99%

Section: Selective Catalytic Reduction (Scr)mentioning

confidence: 99%

Combustion and emissions characteristics of compression-ignition engine using dual ammonia-diesel fuel

Reiter

Kong

2011

Fuel

515

132

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“…Conversely, SCR is a continuous process. It is described as an attractive way to reduce NOx in excess of O2, with the possible use of a large choice of reductants like hydrocarbons (HC) [3][4][5][6][7][8], ammonia [9][10][11][12], urea [13], hydrogen, alcohol [14,15], etc. While HC-SCR has been largely studied in the past decades for automotive applications, the NH3-SCR is now accepted as exhibiting the highest potential to reduce NOx emission in the lean condition, with different reaction pathways described by Equations (1)- (3).…”

Section: Introductionmentioning

confidence: 99%

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

et al. 2015

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Abstract:The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars requires the use of an ammonia precursor, provided by a urea aqueous solution in the conventional process. Although the thermal decomposition and hydrolysis mechanisms of urea are well documented in the literature, the influence of the direct use of urea on the NOx reduction over SCR catalysts may be problematic. With the aim to evaluate prototype powdered catalysts, a specific synthetic gas bench adjusted to powdered material was developed, allowing the use of NH3 or urea as reductant for direct comparison. The design of the experimental setup allows vaporization of liquid urea at 200 °C under 10 bar using an HPLC pump and a micro injector of 50 μm diameter. This work presents the experimental setup of the catalytic test and some remarkable catalytic results towards further development of new catalytic formulations specifically dedicated to urea-SCR. Indeed, a possible divergence in terms of DeNOx efficiency is evidenced depending on the nature of the reductant, NH3 or urea solution. Particularly, the evaluated catalyst may not allow an optimal NOx conversion because of a lack in ammonia availability when the urea residence time is shortened. This is attributed to insufficient activity of isocyanic acid (HNCO) hydrolysis, OPEN ACCESSCatalysts 2015, 5 1536 which can be improved by addition upstream of an active solid for the hydrolysis reaction such as ZrO2. Thus, this µ-scale synthetic gas bench adjusted to powdered materials enables the specific behaviour of urea use for NOx reduction to be demonstrated.

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“…ZSM-5 is commonly studied for the use of diesel engine exhaust catalyst. Zeolites with metal exchange have also been studied (Yahiro, 2001;Xu, 2002;Bhattacharyya, 2011). Yang (2009) studied adsorption of nitrogen oxides onto commercial powdered zeolite Na X and Na Y.…”

Section: Catalyst Mediamentioning

confidence: 99%

Selective catalytic reduction of nitric oxide over cerium-doped activated carbons

Athappan

Sattler

Sethupathi

2015

Journal of Environmental Chemical Engineering

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NOx self-inhibition in selective catalytic reduction with urea (ammonia) over a Cu-zeolite catalyst in diesel exhaust

Cited by 33 publications

References 20 publications

Combustion and emissions characteristics of compression-ignition engine using dual ammonia-diesel fuel

Combustion and emissions characteristics of compression-ignition engine using dual ammonia-diesel fuel

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

Selective catalytic reduction of nitric oxide over cerium-doped activated carbons

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