Alumina-Supported Cu–Ag Catalysts for Ammonia Oxidation to Nitrogen at Low Temperature

Lü, Gang; Anderson, B.; Grondelle, J. van; Santen, Rutger A. van; Gennip, W.J.H. van; Niemantsverdriet, J.W.; Kooyman, Patricia J.; Knoester, Arie; Brongersma, H.H.

doi:10.1006/jcat.2001.3470

Cited by 96 publications

(78 citation statements)

References 21 publications

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“…14,18 The catalytic effect of silver nanoparticles on SCO reactions as well as their interactions with other metal systems were also investigated in the literature. 6,12,19,20 However, a detailed fundamental understanding of the ammonia SCO reaction mechanism on silver single crystals at the atomic/molecular level is still missing. As can be seen in the principal ammonia oxidation reactions given in eqs 1−3, the product distribution in ammonia SCO reaction depends on the active oxygen quantity, and thus, understanding the nature of oxygen is critical in terms of the selectivity of the catalyst.…”

Section: ■ Introductionmentioning

confidence: 99%

Selective Catalytic Ammonia Oxidation to Nitrogen by Atomic Oxygen Species on Ag(111)

Karatok¹,

Vovk

Koç³

et al. 2017

J. Phys. Chem. C

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Ammonia-selective catalytic oxidation was studied on the planar Ag(111) single-crystal model catalyst surface under ultra-highvacuum (UHV) conditions. A variety of oxygen species were prepared via ozone decomposition on pristine Ag(111). Surface coverages of oxygen species were quantified by temperature-programmed desorption (TPD) and X-ray photoemission spectroscopy techniques. Exposure of ozone on Ag(111) at 140 K led to a surface atomic oxygen (O a ) overlayer. Lowenergy electron diffraction experiments revealed that annealing of this atomic oxygen-covered Ag(111) surface at 473 K in UHV resulted in the formation of ordered oxide surfaces (O ox ) with p(5×1) or c(4×8) surface structures. Ammonia interactions with O/Ag(111) surfaces monitored by temperature-programmed reaction spectroscopy indicated that disordered surface atomic oxygen selectively catalyzed N−H bond cleavage, yielding mostly N 2 along with minor amounts of NO and N 2 O. Higher coverage O/Ag(111) surfaces, whose structure was tentatively assigned to a bulklike amorphous silver oxide (O bulk ), showed high selectivity toward N 2 O formation (rather than N 2 ) due to its augmented oxygen density. In contrast, ordered surface oxide overlayers on Ag(111) (where the order was achieved by annealing the oxygen adlayer to 473 K) showed only very limited reactivity toward ammonia. The nature of the adsorbed NH 3 species on a clean Ag(111) surface and its desorption characteristics were also investigated via infrared reflection absorption spectroscopy and TPD techniques. Current findings demonstrate that the Ag(111) surface can selectively oxidize NH 3 to N 2 under well-defined experimental conditions without generating significant quantities of environmentally toxic species such as NO 2 , NO, or N 2 O.

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Section: ■ Introductionmentioning

confidence: 99%

Selective Catalytic Ammonia Oxidation to Nitrogen by Atomic Oxygen Species on Ag(111)

Karatok¹,

Vovk

Koç³

et al. 2017

J. Phys. Chem. C

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“…The results for Ag are not shown here, but previous data [4] indicated that the binding energies of the 3d electrons in Ag 0 , Ag + , or Ag 2+ were similar. Therefore, it was difficult to get the oxidation state of the Ag species from the XPS results.…”

Section: Xpsmentioning

confidence: 53%

“…Adding a suitable amount of CeO 2 improved the catalytic activity of Ag/Al 2 O 3 for NH 3 oxidation at temperatures below 160 o C, and slightly influenced N 2 selectivity by improving the catalyst's ability to adsorb and activate O 2 and the adsorption and activation of NH 3 .Key words: ammonia; silver; cerium; alumina oxide; supported catalyst; oxygen uptake; high resolution transmission electron microscopy; in situ diffuse reflectance infrared Fourier transform spectroscopyThe selective catalytic oxidation (SCO) of NH 3 to nitrogen (N 2 ) and water can reduce NH 3 emissions from chemical processes such as the selective catalytic reduction (SCR) of NO x by NH 3 and from soda production [1][2][3][4][5]. In particular, the low temperature oxidation of NH 3 to N 2 has important environmental applications.…”

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confidence: 99%

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Effects of Adding CeO2 to Ag/Al2O3 Catalyst for Ammonia Oxidation at Low Temperatures

Zhang¹,

Yu²,

Zhang³

et al. 2011

Chinese Journal of Catalysis

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Abstract:The effects of adding CeO 2 to Ag/Al 2 O 3 on the selective catalytic oxidation of ammonia to nitrogen were investigated by activity test and N 2 physisorption, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse-reflectance spectroscopy, high resolution transmission electron microscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy of NH 3 adsorption, and O 2 -pulse adsorption. Adding a suitable amount of CeO 2 improved the catalytic activity of Ag/Al 2 O 3 for NH 3 oxidation at temperatures below 160 o C, and slightly influenced N 2 selectivity by improving the catalyst's ability to adsorb and activate O 2 and the adsorption and activation of NH 3 .Key words: ammonia; silver; cerium; alumina oxide; supported catalyst; oxygen uptake; high resolution transmission electron microscopy; in situ diffuse reflectance infrared Fourier transform spectroscopyThe selective catalytic oxidation (SCO) of NH 3 to nitrogen (N 2 ) and water can reduce NH 3 emissions from chemical processes such as the selective catalytic reduction (SCR) of NO x by NH 3 and from soda production [1][2][3][4][5]. In particular, the low temperature oxidation of NH 3 to N 2 has important environmental applications. Noble metals such as Pt and Ir are the most active but least selective [5][6][7]. Gang et al. [6,8] reported that an alumina-supported Ag (10 wt% Ag/Al 2 O 3 ) catalyst was extremely active for NH 3 oxidation at low temperatures, and was superior to the noble metals. Nonetheless, there is still a considerable need for better catalysts that are active at low temperatures. The addition of CeO 2 improves the NH 3 oxidation activities of Au-, Cu-, and Ag-based catalysts [2,3]. Lippits et al. [3] found that adding CeO x to Ag-based catalyst lowered the temperature for the onset of oxidation from 300 to 200 o C. However, the role of CeO 2 in the Ag-based catalyst has not been studied in detail. Recently, we investigated the SCO of NH 3 over a 10 wt% Ag/Al 2 O 3 catalyst and discovered that the Ag valence state and particle size were significant for activity and N 2 selectivity at low temperatures [7]. To further improve the catalytic performance at low temperatures, we investigated the catalytic effects and the role of CeO 2 addition on Ag/Al 2 O 3 for the oxidation of NH 3 . Experimental Catalyst preparation and H 2 -pretreatmentThe

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“…For instance, Ag has been used industrially for the epoxidation of ethylene (22,23) and the oxdehydrogenation of methanol to formaldehyde. (24)(25)(26) In addition, Ag is well-used for NO x abatement, (27,28) and the oxidation of ammonia, (29) methane, (30) carbon monoxide, (31) organic volatile compounds. (32) Ag with support materials such as ZrO 2 , TiO 2 , Al 2 O 3 and CeO 2 also showed remarkable performance for diesel soot oxidation.…”

Section: Introductionmentioning

confidence: 99%

Sensing of Soot Oxidation by Using Combustion-Type Sensor with Ag-Supported Catalyst

2016

Sensors and Materials

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Soot-sensing properties of the combustion-type sensor coated with Ag-supported catalysts (Ag/TiO 2 , Ag/α-Al 2 O 3 , and Ag/CeO 2 ) were investigated. The catalyst with a high carbon black (CB) oxidation activity in the tight contact (TC) mode had a high response speed, although the response speed had no relationship with the CB oxidation activity in the loose contact (LC) mode. Moreover, the difference in CB oxidation activities between TC and LC modes was consistent with the difference in response speed between V 10 and V 50 , where V 10 and V 50 indicate the response speed of the CB oxidation at 10 and 50% of total output voltage. The catalyst with high intrinsic CB combustion activity improves the response property at initial combustion. On the other hand, the catalyst with the CB combustion activity, which does not depend on the contact state between the CB and the catalyst, improves the response property at later combustion.

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Alumina-Supported Cu–Ag Catalysts for Ammonia Oxidation to Nitrogen at Low Temperature

Cited by 96 publications

References 21 publications

Selective Catalytic Ammonia Oxidation to Nitrogen by Atomic Oxygen Species on Ag(111)

Selective Catalytic Ammonia Oxidation to Nitrogen by Atomic Oxygen Species on Ag(111)

Effects of Adding CeO2 to Ag/Al2O3 Catalyst for Ammonia Oxidation at Low Temperatures

Sensing of Soot Oxidation by Using Combustion-Type Sensor with Ag-Supported Catalyst

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