Transient operando study on the NH3/NH4+ interplay in V-SCR monolithic catalysts

Rasmussen, Søren Birk; Portela, Raquel; Bazin, Philippe; Ávila, P.; Bañares, Miguel Á.; Daturi, Marco

doi:10.1016/j.apcatb.2017.10.026

Cited by 50 publications

(54 citation statements)

References 41 publications

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“…More recent operando TIR configurations are capable of characterizing shaped industrial catalyst conformed monolithic catalysts. The instrument measures chemisorption profiles along the length of the of the bed, which is a powerful advance to understand reaction mechanisms of commerical catalytic materials …”

Section: Uncertaintymentioning

confidence: 99%

Experimental methods in chemical engineering: Fourier transform infrared spectroscopy—FTIR

Guerrero‐Pérez

Patience

2019

Can J Chem Eng

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When molecules absorb infrared radiation (IR), their vibrational mode—stretching and bending of the electric dipole—changes to an excited state. Functional groups in organic molecules absorb IR related to their characteristic vibrational modes. A Fourier transform infrared absorption (FTIR) analyzer measures the absorbed IR to identify molecular composition of surfaces, structural and geometric isomers, orientation in polymers and solutions, and quantify impurities. We describe the power of FTIR instruments and their basic operating principles, including the main experimental setups available: transmission, diffuse reflectance (DRIFTS), reflection adsorption infrared spectroscopy (RAIRS), and attenuated total reflection (ATR), including the recent advances related to time‐resolved and operando applications. In catalytic studies, FTIR spectroscopy has demonstrated its versatility over the last several decades to understand reaction mechanisms, measure gas phase composition, and identify active sites. Over 3000 articles include catalysis and FTIR as keywords but 50 000 articles per year mention IR. We generated a bibliometric map of keywords in articles that Web of Science indexed in 2016 and 2017. The map identified four broad clusters of research related to or applying FTIR: nano‐composites, composites, and mechanical properties; nano‐particles, degradation, graphene oxide, and photo‐catalysis; adsorption, aqueous solutions, and waste water; and drug delivery, silver and gold nano‐particles, green synthesis, and antibacterial activity. Together with a synopsis of the principals of IR spectroscopy and a review of the applications, we discuss uncertainties and limitations of the technique.

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Section: Uncertaintymentioning

confidence: 99%

Experimental methods in chemical engineering: Fourier transform infrared spectroscopy—FTIR

Guerrero‐Pérez

Patience

2019

Can J Chem Eng

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“…With coverage of more than 50%, the stability of the catalyst and the conversion of NO x at high temperatures cannot be guaranteed [7,14]. The vanadium coverage of conventional catalysts is below the dispersion limit that monolayer 6–7 atom /nm 2 to avoid the crystalline V 2 O 5 [15]. It is generally believed that in the dry anatase surface at low loading V 2 O 5 , the dehydrated surface vanadium generally tend to possess isolated four-fold coordination.…”

Section: Composition Of Vanadium Based Catalystmentioning

confidence: 99%

“…In practical application, the vanadium species mainly exists in the form of polyvanadate, as shown in Figure 1b. This species has higher SCR reactivity than the monomer (Ti-O) 3 V=O [3,15,16]. At high loading V 2 O 5 , crystalline vanadia is generated on sulfated TiO 2 (Figure 1c).…”

Section: Composition Of Vanadium Based Catalystmentioning

confidence: 99%

“…The adsorbed ammonia on oxo vanadia Lewis acid sites and ammonium ions associated with Brønsted acid sites selective reduce weakly adsorbed NO via the E-R mechanism, and the water appears to shift the equilibrium between NH 3 and NH 4 + . At this time, the ratio between Lewis acid, Brønsted acid sites and V=O sites depend on the content of water vapor [15]. Because of the low SO 2 resistance of V 2 O 5 -WO 3 /TiO 2 , there are experiments showing that selecting Ce to replace V and the prepared Ce 0.2 W 0.2 TiOx has good NOx conversion activity and N 2 selectivity [42].…”

Section: Performance Improvement Of Vanadium Based Catalystsmentioning

confidence: 99%

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Research Status and Prospect on Vanadium-Based Catalysts for NH3-SCR Denitration

Zhang

Chen

et al. 2018

Materials

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Selective catalytic reduction of NOx with NH3 is one of the most widely used technologies in denitration. Vanadium-based catalysts have been extensively studied for the deNOx process. V2O5/WO3(MoO3)TiO2 as a commercial catalyst has excellent catalytic activity in the medium temperature range. However, it has usually faced several problems in practical industrial applications, including narrow windows of operation temperatures, and the deactivation of catalysts. The modification of vanadium-based catalysts will be the focus in future research. In this paper, the chemical composition of vanadium-based catalysts, catalytic mechanism, the broadening of the temperature range, and the improvement of erosion resistance are reviewed. Furthermore, the effects of four major systems of copper, iron, cerium and manganese on the modification of vanadium-based catalysts are introduced and analyzed. It is worth noting that the addition of modified elements as promoters has greatly improved the catalytic performance. They can enhance the surface acidity, which leads to the increasing adsorption capacity of NH3. Surface defects and oxygen vacancies have also been increased, resulting in more active sites. Finally, the future development of vanadium-based catalysts for denitration is prospected. It is indicated that the main purpose for the research of vanadium-based modification will help to obtain safe, environmentally friendly, efficient, and economical catalysts.

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“…In this sense, the comparison of SCR performance in dry and wet conditions could lead to strong deviations on the Lewis‐to‐Brønsted acid V−O sites ratio which could make difficult any relevant relationships with catalytic properties. As a matter of fact, Rasmussen recently found that NH 3 or NH 4 + intermediates can interplay . By using integral catalytic reactor suited for operando spectroscopic measurements on a monolith, these authors revisited the reaction mechanism of the NH 3 −SCR on a vanadia‐based catalyst facing important technical problems for extracting relevant spectroscopic information in real exhaust conditions especially to distinguish adsorbed ammonia and water.…”

Section: The Surface Chemistry Of Benchmark V2o5 Scr‐catalysts: What mentioning

confidence: 99%

What News in the Surface Chemistry of Bulk and Supported Vanadia Based SCR‐Catalysts: Improvements in their Resistance to Poisoning and Thermal Sintering

Granger

Siaka

Umbarkar

2018

The Chemical Record

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This paper reports a short review on the impact of poisoning effects and thermal aging on the reactivity of surface vanadate species on benchmark V2O5−WO3/TiO2 Selective‐Catalytic‐Reduction catalysts. A renewed interest of this SCR technology is related to its diversification notably as after‐treatment systems to treat the exhaust from Diesel engines with higher running temperature especially when SCR catalysts are coated on Diesel Particulates Filters. Particular attention is also paid to poisoning effects in conjunction with the progressive replacement of fossil fuels by bio‐fuels containing alkaline contaminants which drastically deactivate the catalyst through neutralization of strong acid sites. Most of the investigations show that better insight into the mechanisms of poisoning and aging processes is needed especially to understand the relative sensibility of various vanadate species. This could provide original guidelines to catalyst preparation and or the developments of more stable bulk systems as exemplified.

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Transient operando study on the NH3/NH4+ interplay in V-SCR monolithic catalysts

Cited by 50 publications

References 41 publications

Experimental methods in chemical engineering: Fourier transform infrared spectroscopy—FTIR

Experimental methods in chemical engineering: Fourier transform infrared spectroscopy—FTIR

Research Status and Prospect on Vanadium-Based Catalysts for NH3-SCR Denitration

What News in the Surface Chemistry of Bulk and Supported Vanadia Based SCR‐Catalysts: Improvements in their Resistance to Poisoning and Thermal Sintering

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