46 In-situ UV-visible spectroscopic study for dynamic analysis of silver catalyst

Satsuma, Atsushi; Shibata, Junji; Wada, Akio; Shinozaki, Yoshio; Hattori, Tadashi

doi:10.1016/s0167-2991(03)80203-3

Cited by 57 publications

(63 citation statements)

References 5 publications

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“…Satokawa and co-workers studied the effects of hydrogen on Ag/Al 2 O 3 [5][6][7] and Ag supported on a variety of zeolites [8][9][10]. Initially, they used UV-Vis spectroscopy to show that high activity during the H 2 assisted SCR reaction over a 2 wt% Ag/Al 2 O 3 catalyst was linked to high concentrations of Ag clusters [7].…”

Section: Effect Of H 2 On the Structure Of Silvermentioning

confidence: 99%

“…Initially, they used UV-Vis spectroscopy to show that high activity during the H 2 assisted SCR reaction over a 2 wt% Ag/Al 2 O 3 catalyst was linked to high concentrations of Ag clusters [7]. However, in a later paper [9] they noted that as a result of optical absorption due to Al 2 O 3 it is difficult to observe UV absorption bands below 300 nm when using Al 2 O 3 as a support material.…”

Section: Effect Of H 2 On the Structure Of Silvermentioning

confidence: 99%

“…Several authors have investigated this 'hydrogen' effect using different catalyst formulations and different gas mixes [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The aim of this paper is to review the recent work with particular emphasis on the effect that hydrogen has on the catalyst structure and reaction mechanism for NO x reduction.…”

Section: Introductionmentioning

confidence: 99%

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A review of the effect of the addition of hydrogen in the selective catalytic reduction of NO x with hydrocarbons on silver catalysts

Breen¹,

Burch²

2006

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Research is progressing fast in the field of the hydrogen assisted hydrocarbon selective catalytic reduction (HC-SCR) over Agbased catalysts: this paper is a review of the work to date in this area. The addition of hydrogen to the HC-SCR reaction feed over Ag/Al 2 O 3 results in a remarkable improvement in NO x conversion using a variety of different hydrocarbon feeds. There is some debate concerning the role that hydrogen has to play in the reaction mechanism and its effect on the form of Ag present during the reaction. Many of the studies use in situ UV-Vis spectroscopy to monitor the form of Ag in the catalyst and appear to indicate that the addition of hydrogen promotes the formation of small Ag clusters which are highly reactive for NO x conversion. However, some authors have expressed concern about the use of this technique for these materials and further work is required to address these issues before this technique can be used to give an accurate assessment of the state of Ag during the SCR reaction. A study using in situ EXAFS to probe the H 2 assisted octane-SCR reaction has shown that small Ag particles (containing on average 3 silver atoms) are formed during the SCR reaction but that the addition of H 2 to the feed does not result in any further change in the Ag particle size. This points to the direct involvement of H 2 in the reaction mechanism. Clearly the addition of hydrogen results in a large increase in the number and variety of adsorbed species on the surface of the catalyst during the reaction. Some authors have suggested that conversion of cyanide to isocyanate is the rate-determining step and that hydrogen promotes this conversion. Others have suggested that hydrogen reduces nitrates to more reactive nitrite species which can then activate the hydrocarbon; activation of the hydrocarbon to form acetates has been proposed as the key step. It is probable that all these promotional effects can take place and that it very much depends on the reaction temperature and feed conditions as to which one is most important.

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Section: Effect Of H 2 On the Structure Of Silvermentioning

confidence: 99%

Section: Effect Of H 2 On the Structure Of Silvermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A review of the effect of the addition of hydrogen in the selective catalytic reduction of NO x with hydrocarbons on silver catalysts

Breen¹,

Burch²

2006

Top Catal

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“…We know from earlier work on the SCR of NO by hydrocarbons over Ag/Al 2 O 3 Hoost et al, 1997;Kung et al, 1997;Burch et al, 2002;Satsuma et al, 2003) and our own previous work (Guo et al, 2008), that generally, in a Ag/Al 2 O 3 catalyst with low or moderate Ag loadings (from 1 to 3 wt%), Ag + ions are dominant and highly dispersed, which is related to higher NO conversions. In contrast to this, increasing silver loading is related to the formation of metallic Ag on the catalytic surface, which favors oxidation of the reductant by oxygen, and leads to limited de-NO x activity.…”

Section: Effect Of Ti Additivementioning

confidence: 91%

Promotional Effect of Titanium on the Catalytic Performance of Anodic Alumina Supported Silver Catalyst for the Selective Reduction of NO with Propene

Chen

Guo

Uesawa

et al. 2009

J. Chem. Eng. Japan / JCEJ

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“…The surface NO x are continually reduced to reactive nitrite species, which, in turn, can activate hydrocarbons [10,15]. Hydrogen could also influence chemical state of Ag species [13,14,16,17], which, in turn, affects activation process of NO x and reductant.…”

Section: Introductionmentioning

confidence: 99%

H2-Induced NO x Adsorption/Desorption over Ag/Al2O3: Transient Experiments and TPD Study

et al. 2011

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NO adsorption/desorption over 1 wt% Ag/ Al 2 O 3 was studied by a combination of isothermal transient adsorption/desorption and NO x temperature-programmed desorption (NO x -TPD) methods. NO x -TPD profiles obtained for Ag/Al 2 O 3 were identified by comparison with decomposition profiles of ''model'' AgNO 3 /Al 2 O 3 and Al(NO 3 ) 3 / Al 2 O 3 prepared by impregnation of Al 2 O 3 with individual AgNO 3 and Al(NO 3 ) 3 compounds. The data obtained indicate that H 2 -induced NO adsorption leads to the formation of surface Ag and Al-nitrates. Their accumulation on the catalyst surface is accompanied by an intensive NO 2 evolution, which proceeds primarily via reaction of surface nitrates with NO. Thus, NO 2 formation appears to result from an intrinsic stage of the H 2 -induced NO x adsorption process, rather than from the direct oxidation of NO by gaseous oxygen catalyzed by Ag.

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46 In-situ UV-visible spectroscopic study for dynamic analysis of silver catalyst

Cited by 57 publications

References 5 publications

A review of the effect of the addition of hydrogen in the selective catalytic reduction of NO x with hydrocarbons on silver catalysts

A review of the effect of the addition of hydrogen in the selective catalytic reduction of NO x with hydrocarbons on silver catalysts

Promotional Effect of Titanium on the Catalytic Performance of Anodic Alumina Supported Silver Catalyst for the Selective Reduction of NO with Propene

H2-Induced NO x Adsorption/Desorption over Ag/Al2O3: Transient Experiments and TPD Study

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