Isocyanic acid hydrolysis over Fe-ZSM5 in urea-SCR

Piazzesi, Gaia; Devadas, Mukundan; Kröcher, Oliver; Elsener, Martin; Wokaun, Alexander

doi:10.1016/j.catcom.2006.01.022

Cited by 59 publications

(29 citation statements)

References 15 publications

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“…Fe-ZSM5 showed a much higher activity than H-ZSM5 and Fe 2 O 3 , which is clearly discernible below 300°C. Interesting enough hydrothermal ageing at 650°C for 5 h even improves the hydrolysis activity of Fe-ZSM5 as reported in our previous investigation [11].…”

Section: Catalytic Activitymentioning

confidence: 62%

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Investigation of HNCO adsorption and hydrolysis on Fe-ZSM5

et al. 2007

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At 150°C, HNCO adsorbs dissociatively on Fe-ZSM5 producing principally isocyanate species (-NCO) adsorbed on Al and Fe sites. In the presence of water the hydrolysis of the -NCO groups to NH 3 was observed. Comparison of the DRIFT results with measurements of the catalytic activity of coated cordierite monoliths suggests that -NCO groups are likely intermediate species in the hydrolysis of HNCO over Fe-ZSM5.

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Section: Catalytic Activitymentioning

confidence: 62%

“…Despite the increasing knowledge about the SCR reaction on Fe-ZSM5, only very little information is available about the preceding HCNO hydrolysis occurring on Fe-supported catalysts [10,11]. Solymosi et al investigated the HNCO adsorption, but specifically on Cu-ZSM5 and hydrolysis was no issue in this study [12].…”

Section: Thermo-hydrolysis Of Ureamentioning

confidence: 95%

Investigation of HNCO adsorption and hydrolysis on Fe-ZSM5

et al. 2007

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“…It is clear that the metal ammine system is much simpler than the ureabased system conversion of isocyanic acid is well-studied and several catalysts have been investigated since it is of crucial importance for urea-SCR. It is well-known that several side reactions may take place in parallel during urea decomposition (i.e., the isocyanic acid undergoes a series of condensation reactions that lead to the formation of different solids), so the picture is far from as simple as expressed in the two reaction schemes above [12]. This leads to an uncertainty on the degree of conversion of urea to ammonia, which of course is undesirable since it is necessary to control the NH 3 -NO x ratio accurately.…”

Section: Indirect Ammonia Storage Technologiesmentioning

confidence: 97%

Improved Automotive NO x Aftertreatment System: Metal Ammine Complexes as NH3 Source for SCR Using Fe-Containing Zeolite Catalysts

Johannessen¹,

Schmidt²,

Frey

et al. 2009

Catal Lett

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“…The best hydrolysis catalyst known for the urea-SCR application is anatase TiO 2 [10,37,[47][48][49]. Also, V 2 O 5 /WO 3 -TiO 2 [13,50] and zeolite-based [10,11,51] SCR catalysts provide high hydrolysis activities. [11,36,37] If byproducts form on the catalyst in spite of its hydrolysis activity, or if byproduct-containing aerosols are deposited on the catalyst, even these byproducts can be hydrolyzed catalytically.…”

Section: Urea Decomposition Byproducts and Catalyst Deactivationmentioning

confidence: 99%

“…The addition of V 2 O 5 and/or WO 3 to TiO 2 decreases its hydrolysis activity [50,54]. Also, zeolite catalysts show lower hydrolysis activity than pure TiO 2 [51,54]. Still, HNCO hydrolysis on SCR catalysts is faster than the actual SCR reaction, indicating that increasing the size of the SCR catalyst is better than placing a hydrolysis catalyst in front of it [50].…”

Section: Catalytic Urea Decompositionmentioning

confidence: 99%

Ammonia Storage and Release in SCR Systems for Mobile Applications

Peitz

Bernhard

Kröcher

2014

Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts

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The SCR reaction requires ammonia for the reduction of nitrogen oxides. While compressed or liquefied ammonia is used for the supply of ammonia in stationary applications, the odorous ammonia gas had to be replaced in mobile SCR applications by an ammonia precursor compound for the safe storage and reliable release of ammonia in the right quantities and right dynamics. Thus, significant innovation was needed before mobile SCR systems could be realized, even though commercial operation of ammonia SCR systems in coal power plants ([250 MW) started already around 1980 [1]. After the invention of HC-SCR for mobile NO x sources, to avoid handling NH 3 [2], and the discovery of cyanuric acid as a safe NH 3 storage compound, [3] urea was proposed as a storage material for NH 3 in 1988 [4]. By then, urea was already known to work as an NH 3 precursor for SCR in stationary applications for 3 years [5]. First results on mobile urea-based SCR were publically presented in 1990, already showing NO x conversions above 90 % from 250°C at gas hourly space velocities (GHSV) of 12,900 h -1 [6]. The first patented mobile applications of urea solutions for SCR were registered in 1990 [7].Due to the large-scale production of urea as a bulk commodity, it is readily available in large quantities. Since the involved reactants CO 2 and NH 3 needed for urea synthesis are bulk chemicals that are produced directly from air and natural gas, using the well-known industrial Haber-Bosch process, urea can be produced at a low price [8]. Also, urea is nontoxic, noncorrosive and can easily be handled as aqueous solutions, such as a 32.5 wt % solution with the trade name AdBlue

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Isocyanic acid hydrolysis over Fe-ZSM5 in urea-SCR

Cited by 59 publications

References 15 publications

Investigation of HNCO adsorption and hydrolysis on Fe-ZSM5

Investigation of HNCO adsorption and hydrolysis on Fe-ZSM5

Improved Automotive NO x Aftertreatment System: Metal Ammine Complexes as NH3 Source for SCR Using Fe-Containing Zeolite Catalysts

Ammonia Storage and Release in SCR Systems for Mobile Applications

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