NO reduction by CH4 in the presence of excess O2 over Pd/sulfated zirconia catalysts

Chin, Ya-Huei; Pisanu, Adriana; Serventi, Lorena K.; Alvarez, Walter E.; Resasco, Daniel E.

doi:10.1016/s0920-5861(99)00205-9

Cited by 62 publications

(41 citation statements)

References 21 publications

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“…It has been shown that simple oxides with strong acidity, such as sulfated and tungstated zirconia, possess the ability to stabilize highly dispersed Pd(II) species analogous to the acidic zeolites [11,12,[21][22][23]. Lowloading palladium catalysts supported on sulfated and tungstated zirconia exhibit catalytic properties in the CH 4 -SCR of NO under dry conditions comparable to those of zeolitic catalysts and they show improved selectivity in the presence of H 2 O and SO 2 [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Kantcheva

Çayırtepe

2006

Journal of Molecular Catalysis A: Chemical

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Surface species obtained during the adsorption of NO and NO/O 2 coadsorption at room temperature on Pd-free (WZ) and Pd-promoted tungstated zirconia (Pd/WZ) are identified by means of in situ FT-IR spectroscopy. The WZ and Pd/WZ samples have a tetragonal structure and contain randomly distributed mesoporous phase. Dispersed palladium(II) species are present in two different environments: (i) Pd 2+ ions, which have only Zr 4+ ions in their second coordination sphere and (ii) Pd 2+ ions, which are linked to both zirconium and tungsten ions via oxygen bridges. On the Pd/WZ sample, NO undergoes oxidation to various NO x species depending on the temperature. The compounds formed at room-temperature oxidation are adsorbed N 2 O 3 and products of its self-ionization, NO + and NO 2 − . In this process W(VI) is involved, being reduced to W(IV). At high temperature N 2 O 3 decomposes, restoring the W O species. Under these conditions, NO undergoes oxidation to NO 2 by the Pd(II) ions, which are reduced to Pd(I). The nitrosyls of Pd(I) display high thermal stability and do not disappear upon evacuation at 623 K. During NO/O 2 coadsorption on the Pd/WZ catalyst at room temperature, the amounts of surface nitrates and NO 2 /N 2 O 4 formed in the gas phase are significantly lower than those observed under identical conditions in the presence of tungstated zirconia. It is concluded that promotion of tungstated zirconia with palladium(II) suppresses the oxidation of NO by molecular oxygen at room temperature due to the elimination of acidic protons involved in the process.

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Section: Introductionmentioning

confidence: 99%

“…Maximum activity in the CH 4 -SCR of NO is observed on zirconia catalysts containing up to 16-20 wt.% WO 3 and 0.1-0.17 wt.% Pd [21][22][23][24]. Tungstated zirconia is usually prepared by impregnation of hydrated zirconia with ammonium metatungstate, followed by calcination in the 873-1100 K range [25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Kantcheva

Çayırtepe

2006

Journal of Molecular Catalysis A: Chemical

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“…Therefore, strict legislation around the world has led to the development of efficient DeNO x technologies in order to preserve the global environment. Over the last several years, the use of hydrocarbons as a substitute for ammonia in the selective catalytic reduction (SCR) of NO from oxygen-rich streams has drawn much attention [1][2][3][4][5][6][7][8][9][10][11]. Among various hydrocarbons, methane is the most preferable, because it is the main component of natural gas [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Over the last several years, the use of hydrocarbons as a substitute for ammonia in the selective catalytic reduction (SCR) of NO from oxygen-rich streams has drawn much attention [1][2][3][4][5][6][7][8][9][10][11]. Among various hydrocarbons, methane is the most preferable, because it is the main component of natural gas [5][6][7][8][9][10][11]. Many kinds of catalysts such as Co- [5,[12][13][14], Ni- [13], Mn- [15][16][17], Ga- [18], In- [19][20][21][22][23][24], and Pd- [25,26] loaded ZSM-5 have been reported to be active for the catalytic reduction of NO with methane.…”

Section: Introductionmentioning

confidence: 99%

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Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

2004

Journal of Catalysis

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In this work, the structural and surface properties of Co-loaded sulfated zirconia (SZ) catalysts were studied by X-ray diffraction (XRD), N 2 adsorption, NH 3 -TPD, FT-IR spectroscopy, H 2 -TPR, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and NO-TPD. NH 3 -TPD and FT-IR spectra results of the catalysts showed that the sulfation process of the support resulted in the generation of strong Brønsted and Lewis acid sites, which is essential for the SCR of NO with methane. On the other hand, the N 2 adsorption, H 2 -TPR, UV/vis DRS, and XPS of the catalysts demonstrated that the presence of the SO 4 2− species promoted the dispersion of the Co species and prevented the formation of Co 3 O 4 . Such an increased dispersion of Co species suppressed the combustion reaction of CH 4 by O 2 and increased the selectivity toward NO reduction. The NO-TPD proved that the loading of Co increased the adsorption of NO over SZ catalysts, which is another reason for the promoting effect of Co.  2004 Elsevier Inc. All rights reserved.

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Pd-supported on sulfated monoclinic zirconia for the reduction of NO2 with methane under lean conditions

2006

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NO 2 reduction with methane under lean conditions is studied as a part of a two-stage scheme where NO is first oxidized to NO 2 over an oxidation catalyst and NO 2 is subsequently reduced to N 2 over a reduction catalyst. Pd supported on a sulfated monoclinic zirconia support was observed to have good activity for the reduction of NO 2 with CH 4 under lean conditions, giving N 2 yields over 60% over a broad temperature range below 450°C. Sulfate groups are shown to be thermally stable below the calcination temperature.

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NO reduction by CH4 in the presence of excess O2 over Pd/sulfated zirconia catalysts

Cited by 62 publications

References 21 publications

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

Pd-supported on sulfated monoclinic zirconia for the reduction of NO2 with methane under lean conditions

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