Activity and durability of Fe/ZSM-5 catalysts for lean burn NOx reduction in the presence of water vapor

Chen, Hai-Ying; Sachtler, Wolfgang M.H.

doi:10.1016/s0920-5861(98)00078-9

Cited by 509 publications

(325 citation statements)

References 30 publications

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“…At 450° C mesoporous catalyst is even more active: 93% against 86% for 3% V 2 O 5 /TiO 2 . It should be also mentioned that the catalysts tested in this work have lower catalytic activity than the overexchanged Fe-ZSM-5 catalysts prepared by chemical vapor deposition [3] or ''Improved Liquid Ion Exchange'' technique [4,5] However, due to the complicated procedure for the preparation of ion-exchanged Fe-ZSM-5 and lack or reproducibility, the large-scale utilization of these catalysts in industry is limited. Therefore we first apply very simple method of incipient wetness impregnation, which, in contrast to the ionexchange procedure, enables us to introduce active component in more controlled way, which is more important for the fair comparison of the conventional and mesoporous samples.…”

Section: Resultsmentioning

confidence: 99%

“…In view of these challenges, the recent discovery of the remarkable activity of over-exchanged Fe-ZSM-5 catalysts in the SCR of NO with isobutene [1] and ammonia [2] was considered a breakthrough. Later it was shown that iron-modified ZSM-5 catalysts prepared by chemical vapor deposition of iron (III) chloride onto the H-form of the zeolite yield high activities most reproducibly [3]. Several recent works have reported very active Fe-ZSM-5 catalysts obtained by the ''Improved Liquid Ion Exchange'' technique [4,5] as well as by solidstate ion-exchange [6].…”

Section: Introductionmentioning

confidence: 99%

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Mesoporous Fe-containing ZSM-5 zeolite single crystal catalysts for selective catalytic reduction of nitric oxide by ammonia

et al. 2007

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Mesoporous and conventional Fe-containing ZSM-5 catalysts (0.5-8 wt% Fe) were prepared using a simple impregnation method and tested in NO selective catalytic reduction (SCR) with NH 3 . It was found that mesoporous Fe-ZSM-5 catalysts exhibit higher SCR activities than comparable conventional catalysts. Furthermore, conventional Fe-ZSM-5 catalysts have maximum activity at ~ 2.5 wt% Fe while for the mesoporous system, optimal NO conversion is obtained for the catalysts with ~ 6 wt % Fe.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mesoporous Fe-containing ZSM-5 zeolite single crystal catalysts for selective catalytic reduction of nitric oxide by ammonia

et al. 2007

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“…The samples were stored at room temperature in dry air. 5 and described in more detail by Battiston and co-workers. 8 The H + removal efficiency (98%), determined by HCl titration, indicated that during the Fe-exchange procedure nearly all the Brönsted acid sites were removed from the H/ZSM-5.…”

Section: Methodsmentioning

confidence: 99%

Kβ-Detected XANES of Framework-Substituted FeZSM-5 Zeolites

et al. 2004

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The valence and local symmetry of iron in framework-substituted FeZSM-5 with a high Fe dilution (Si/Fe ) 360) was studied by means of K -detected X-ray absorption spectroscopy. This technique combines highresolution (∆E ∼1 eV) fluorescence detection of the 3p to 1s (K ) transition with the X-ray absorption near-edge structure (XANES) at the Fe K-edge. An absorption-like spectrum is recorded by detecting the K fluorescence intensity as a function of the incident energy that is scanned through the K absorption edge. K -detected XANES spectra allow for a more precise separation of the weak K pre-edge structure from the main edge as compared to conventional absorption spectroscopy. Subsequent analysis and interpretation of the pre-edge spectral features therefore is more accurate. The pre-edge is sensitive to changes in the local coordination and oxidation state of Fe. Using this technique we were able to quantitatively determine the degree of iron extraction out of a zeolite framework upon steaming. With the use of appropriate reference compounds, the pre-edge analysis was used to monitor the activation of low-loaded, framework-substituted FeZSM-5 (0.3 wt % Fe). Template removal and calcination distort the zeolite framework and induce a deviation from T d symmetry for incorporated iron. The (deliberate) presence of water at high temperature (T > 500°C) facilitates the hydrolysis of the Si-O-Fe bonds and increases the formation of extraframework iron species. The amount of Fe III occupying tetrahedral sites in the MFI-type zeolite decreases to 32% and 19%, respectively, for mild-and hard-steamed samples.

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“…In the case of Laponite, only a small peak appears at 309 • C, which can be attributed to the slight reduction of Laponite. Moreover, for the catalysts, All curves are dominated by one main reduction peak at 440 • C, which can be assigned to the reduction of Fe 3+ to Fe 2+ [28,29]. And the peak intensity increases with the rise of iron loading.…”

Section: Reductive Properties Of Catalystsmentioning

confidence: 91%

Selective catalytic oxidation of H2S over iron oxide supported on alumina-intercalated Laponite clay catalysts

Zhang

Dou

Wang

et al. 2013

Journal of Hazardous Materials

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h i g h l i g h t s• Fe/Al-Lap catalysts with mesoporous structure were synthesized.• Iron oxide mainly exists in form of isolate Fe 3+ in an oxidic environment.• Fe/Al-Lap catalysts show high catalytic activities at low temperature.• The high catalytic activities are ascribed to the interaction between iron oxide and alumina.• The formed Fe 2 (SO 4 ) 3 and elemental sulfur deposits on surface cause catalyst deactivation. g r a p h i c a l a b s t r a c tThe catalytic reaction and deactivation mechanisms for H 2 S selective oxidation over Fe/Al-Lap catalysts are shown in the illustration. The catalytic reaction follows Mars-van Krevelen mechanism. Moreover, the interaction between iron oxide and alumina, the strong acidity of the catalysts and the well dispersion of iron oxide improve the catalytic performance efficiently. Meanwhile, the catalyst deactivation is mainly due to the formation of Fe 2 (SO 4 ) 3 and elemental sulfur deposits on the surface. a r t i c l e i n f o b s t r a c tA series of iron oxide supported on alumina-intercalated clay catalysts (named Fe/Al-Lap catalysts) with mesoporous structure and high specific surface area were prepared. The structural and chemical properties were studied by nitrogen sorption isotherms, X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FTIR), H 2 temperature-programmed reduction (H 2 -TPR) and NH 3 temperature-programmed desorption (NH 3 -TPD) techniques. It was realized that iron oxide mainly existed in the form of isolated Fe 3+ in an oxidic environment. Fe/Al-Lap catalysts showed high catalytic activities in the temperature range of 120-200 • C without the presence of excessive O 2 . This can be attributed to the interaction between iron oxide and alumina, which improve the redox property of Fe 3+ efficiently. In addition, the strong acidity of catalysts and good dispersion of iron oxide were also beneficial to oxidation reaction. Among them, 7% Fe/AlLap catalyst presented the best catalytic performance at 180 • C. Finally, the catalytic and deactivation mechanisms were explored.Crown

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Activity and durability of Fe/ZSM-5 catalysts for lean burn NOx reduction in the presence of water vapor

Cited by 509 publications

References 30 publications

Mesoporous Fe-containing ZSM-5 zeolite single crystal catalysts for selective catalytic reduction of nitric oxide by ammonia

Mesoporous Fe-containing ZSM-5 zeolite single crystal catalysts for selective catalytic reduction of nitric oxide by ammonia

Kβ-Detected XANES of Framework-Substituted FeZSM-5 Zeolites

Selective catalytic oxidation of H2S over iron oxide supported on alumina-intercalated Laponite clay catalysts

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