Evaluation of Hydrothermally Aged Vanadia SCR on High-Porosity Substrate

Asako, Tsuyoshi; Kai, Ryuji; Toyoshima, Tetsuo; Vogt, Claus; Hirose, Shogo; Nakao, Shiori

doi:10.4271/2016-01-2320

Cited by 5 publications

(8 citation statements)

References 12 publications

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“…Thermal stability at temperatures above 600 °C in power plants 8 is a problem. Meanwhile, extreme operating points 9 and the regeneration of diesel particulate filter (DPF) 10 can result in temperature above 650 °C. Thus, the challenge for the Vanadia-SCR catalyst is the hydrothermal durability.…”

Section: Introductionmentioning

confidence: 99%

“…Rasmussen and Abrams 14 demonstrated that vanadium tungsten catalyst was stable under hydrothermal conditions at 550 °C (110 h) and the deactivation was not due to vanadium evaporation. Xi et al 15 aged the Vanadia-SCR catalyst from 525 to 700 °C for 2 h. Asako et al 10 aged vanadia catalyst for 100 h at 550 °C and found that it lost 40–60% activity. Madia et al 9 performed progressive aging experiments for 100 h at 550 °C and 30 h at 600 °C and found that 2 wt % V 2 O 5 had the best hydrothermal stability.…”

Section: Introductionmentioning

confidence: 99%

“…17 Aging leads to a decrease in NH 3 storage capacity. 10 Therefore, changes of NH 3 storage capacity during hydrothermal aging needs further study. Furthermore, the reduction in the BET surface area originates from anatase sintering and phase transition.…”

Section: Introductionmentioning

confidence: 99%

“…Besides, ammonia storage capacity decreases as aging temperature increases and it is facilitated by Brønsted acid sites . Aging leads to a decrease in NH 3 storage capacity . Therefore, changes of NH 3 storage capacity during hydrothermal aging needs further study.…”

Section: Introductionmentioning

confidence: 99%

“…The main disadvantage of vanadium-based SCR is the deactivation at temperatures exceeding 600–650 °C . Pure V 2 O 5 has a melting point of 670 °C, which easily leads to sintering of V 2 O 5 particles and a decrease in catalytic activity. , As mentioned by Asako et al, DPF regeneration raises the SCR inlet temperature to 650 °C. By estimation, this situation lasts for 50 h throughout the life of the after treatment system .…”

Section: Introductionmentioning

confidence: 99%

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New Findings in Hydrothermal Deactivation Research on the Vanadia-Selective Catalytic Reduction Catalyst

Yao

et al. 2019

ACS Omega

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Considering the risks of hydrothermal deterioration in vehicles, power plants, and oceangoing vessels, V 2 O 5 -WO 3 /TiO 2 catalysts were subject to hydrothermal and thermal aging at 600, 625, 635, and 650 °C for 4–48 h. The different ratio and significant loss of active sites are main reasons for catalyst deactivation. Both Lewis and Brønsted acid sites are involved in the selective catalytic reduction reaction. Brønsted acid sites are more susceptible. High temperature plays a major role in the aging. It causes sintering, particle growth, and the anatase phase transition. Phase transformation turns out to be less important than sintering. Sintering leads to the reduction of the BET surface area, which in turn causes decrease of NH 3 adsorption amount and changes of active sites. Aging time can accelerate the degree of deactivation. It also helps to change the proportion of active sites. Water vapor has no significant effect on NO X conversion rates.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New Findings in Hydrothermal Deactivation Research on the Vanadia-Selective Catalytic Reduction Catalyst

Yao

et al. 2019

ACS Omega

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Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NO_x Emissions with NH₃

et al. 2021

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Supported V2O5–WO3/TiO2 materials are employed as selective catalytic reduction (SCR) catalysts for NO x emission control from power plants. Fresh SCR catalysts usually receive exposure to harsh treatments in the industry to accelerate catalyst activation (calcination in air at 650 °C) and catalyst aging (hydrothermal aging at 650 °C) in a way that represents various points in the catalyst/product lifetime. The present study investigates the catalyst structural and chemical changes occurring during such harsh treatments. Three series of supported V2O5–WO3/TiO2 catalysts were prepared by incipient-wetness impregnation of aqueous ammonium metavanadate and metatungstate precursors. The catalysts were subsequently dried and calcined at 550 °C in O2, 650 °C in O2, and hydrothermal conditions (10% O2, 8% H2O, 7% CO2, and 75% N2) at 650 °C. The resulting catalysts were physically characterized by numerous techniques (in situ Raman; in situ IR; in situ high-field–high-spinning solid-state 51V MAS NMR; in situ electron paramagnetic resonance; X-ray diffraction; Brunauer, Emmett, and Teller surface area; and inductively coupled plasma) and chemically probed with adsorbed ammonia, SCR–TPSR, and the SCR reaction. The surface WO x sites on the TiO2 support behave as a textural promoter that stabilizes the TiO2 (anatase) phase from sintering and transforming to the undesirable crystalline TiO2 (rutile) phase that can lead to formation of a Ti1–x V x O2 (rutile) solid solution with reduced V4+ cations (∼7–15%). The surface VO x sites are mostly oligomerized as surface V5+O x sites (∼50–85% oligomers) and the extent of oligomerization tends to increase with surface WO x coverage and calcination temperature. A major difference between the calcined and hydrothermally treated catalysts was the low concentration of surface NH3 * species on Lewis acid sites for the hydrothermally treated catalysts, yet the SCR activity was almost comparable for both catalysts. This finding suggests that surface NH4 +*, primarily associated with the surface VO x sites, are able to efficiently perform the SCR reaction. Given that multiple catalyst parameters were simultaneously varying during these treatments, it was difficult to correlate the SCR activity with any single catalyst parameter. A correlation, however, was found between the SCR TOF/activity and the sum of the surface NH3 * and NH4 +* species, which is dominated by the surface NH4 +* species.

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Role of Vanadium in Thermal and Hydrothermal Aging of a Commercial V2O5-WO3/TiO2 Monolith for Selective Catalytic Reduction of NOx: A Case Study

Consentino,

Pantaleo,

La Parola

et al. 2024

Catalysts

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In recent years, increased attention to air pollutants such as NOx has led the scientific community to focus meaningfully on developing strategies for NOx reduction. Selective catalytic reduction of NOx by ammonia (NO SCR by NH3) is currently the main method to remove NOx from diesel engine exhaust emissions. The catalysts with typical V2O5-WO3/TiO2 (VWTi) composition are widely used in NH3-SCR for their high NOx conversion activity, low cost, and robustness, especially concerning sulfur poisoning. However, in real diesel engine working conditions, the thermal and hydrothermal aging of catalysts can occur after several hours of operation at high temperature, affecting the catalytic performance. In this study, the stability of a commercial VWTi monolith, self-supported and containing glass fibers and bentonite in its matrix, was investigated as a case study. In laboratory conditions, NO SCR tests were performed for 50 h in the range of 150 to 350 °C. Subsequently, the VWTi monolith was thermally and hydrothermally aged at 600 °C for 6 h. The thermal aging increased the NOx conversion, especially at low temperature (<250 °C), while the hydrothermal aging did not affect the SCR. The differences in NOx conversion before and after aging were associated with the change in vanadium and tungsten oxide surface coverage and with the reduction in the surface area of catalysts. In order to correlate the change in SCR activity with the modifications occurring after aging processes, the monolithic samples were characterized by several techniques, namely XRD, SSA and pore analysis, TPR, XPS, Raman, TGA and SEM/EDX.

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Evaluation of Hydrothermally Aged Vanadia SCR on High-Porosity Substrate

Cited by 5 publications

References 12 publications

New Findings in Hydrothermal Deactivation Research on the Vanadia-Selective Catalytic Reduction Catalyst

New Findings in Hydrothermal Deactivation Research on the Vanadia-Selective Catalytic Reduction Catalyst

Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NO_x Emissions with NH₃

Role of Vanadium in Thermal and Hydrothermal Aging of a Commercial V2O5-WO3/TiO2 Monolith for Selective Catalytic Reduction of NOx: A Case Study

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Evaluation of Hydrothermally Aged Vanadia SCR on High-Porosity Substrate

Cited by 5 publications

References 12 publications

New Findings in Hydrothermal Deactivation Research on the Vanadia-Selective Catalytic Reduction Catalyst

New Findings in Hydrothermal Deactivation Research on the Vanadia-Selective Catalytic Reduction Catalyst

Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NOx Emissions with NH3

Role of Vanadium in Thermal and Hydrothermal Aging of a Commercial V2O5-WO3/TiO2 Monolith for Selective Catalytic Reduction of NOx: A Case Study

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Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NO_x Emissions with NH₃