The Impact of Sulphur Storage on Emissions From Three-Way Catalysts

Diwell, A.F.; Hallett, Christopher; Taylor, Jeffrey R.

doi:10.4271/872163

Cited by 20 publications

(13 citation statements)

References 2 publications

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“…However, it has been shown that sulfate formation can also occur on ceria in the absence of noble metals. , Diwell et al found temperature-dependent uptake of S on CeO 2 following exposure to 1% SO 2 in N 2 that was a attributed to chemisorbed SO 2 at 300 K and Ce 2 (SO 4 ) 3 at 823 K. This assignment was based on comparison of the Ce 3d spectrum with cerrous nitrate and on the intensity increase and BE increase in the S 2p peaks at 823 K compared to a sample exposed to SO 2 at room temperature. Waqif et al showed by thermogravimetry and FT-IR that formation of the sulfate is thermally activated and that bulk sulfate formation occurs in an SO 2 atmosphere above 500 K. These results therefore suggest that the reaction can occur without a metal catalyst at sufficiently high temperature.…”

Section: Discussionmentioning

confidence: 99%

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Chemisorption and Reaction of Sulfur Dioxide with Oxidized and Reduced Ceria Surfaces

et al. 1999

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The interaction of SO2 with highly oriented ceria films is studied as a function of coverage, temperature, and degree of oxidation of the ceria. Soft X-ray photoemission (SXPS) is used to analyze the oxidation state of the ceria and the evolution of the SO2-derived species, while thermal desorption spectroscopy is used to analyze the desorption products. The principle interaction is chemisorption of SO2 at oxygen anions, which reversibly desorbs as SO2 over a broad temperature range from 200 to 600 K. This interaction is characterized as a Lewis acid−base interaction and occurs with approximately equal facility if the surface is hydroxylated or sulfided. On reduced ceria the adsorption is more heterogeneous, suggesting a variety of local bonding environments, including a small, distinguishable amount of adsorption at Ce3+ sites. A significant portion of the chemisorbed SO2 converts to sulfide above 300 K, and the resulting sulfide then equilibrates between bulk and surface sites above 600 K. Adsorption at a sulfide site leads to a 1.5 eV shift in the sulfide S 2p state toward higher binding energy. Thermal conversion of chemisorbed SO2 to sulfate is not observed. The results are compared with previous studies of NO adsorption on ceria films and with similar studies of SO2 chemisorption on titania.

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Section: Discussionmentioning

confidence: 99%

“…It is claimed that SO 2 reduces ceria at 773 K to form Ce 2 (SO 4 ) 3 , which decomposes around 1173 K . Evidence of ceria reduction has been reported by UV−visible diffuse reflectance 7 and Ce XPS measurements. , …”

Section: Introductionmentioning

confidence: 99%

Chemisorption and Reaction of Sulfur Dioxide with Oxidized and Reduced Ceria Surfaces

et al. 1999

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“…The interaction between SO 2 and CeO 2 has been widely investigated in the literature, since CeO 2 is a well known promoter currently used in three way catalytic mufflers [13][14][15][16][17]. Some works evidenced an increase of SO 2 uptake on CeO 2 with respect to Al 2 O 3 [18][19][20] associated with the higher basic strength of ceria [17,18]. On the other hand a decrease of adsorbed SO 2 onto CeO 2 and CeO 2 -ZrO 2 in the presence of noble metals was reported in reference [21].…”

Section: Introductionmentioning

confidence: 99%

Regeneration of S-poisoned Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts for the combustion of methane

et al. 2007

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This work investigates the regeneration of S-poisoned Pd/Al 2 O 3 and Pd/CeO 2 /Al 2 O 3 catalysts under different CH 4 containing atmospheres. Under lean combustion conditions in the presence of excess O 2 , partial regeneration took place for both systems only above 750°C after decomposition of stable sulphate species adsorbed on the support. Under alternate lean combustion/CH 4 -reducing pulse regeneration is markedly anticipated down to 550-600°C. Experiments evidenced an effective role of ceria in preventing PdO from sulphation and in promoting regeneration via sulphates decomposition under reducing conditions.

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“…There are several studies which propose that SO 2 can sulfate the cerium oxides, forming various types of cerium sulfates. [36][37][38] The type of sulfates and the reaction pathway depends on the oxidation state of ceria sites and temperature of the catalyst. This complicates the modeling of the sulfation and desulfation pathways of the ceria sites.…”

Section: Resultsmentioning

confidence: 99%

“…The modeled phenomena on the bCe include Oxygen storage and reduction reactions (rxn9–rxn11) and sulfur storage and release on bulk ceria (rxn12–rxn15). There are several studies which propose that SO 2 can sulfate the cerium oxides, forming various types of cerium sulfates . The type of sulfates and the reaction pathway depends on the oxidation state of ceria sites and temperature of the catalyst.…”

Section: Resultsmentioning

confidence: 99%

Modeling of the desulfation process in NO_x storage and reduction catalysts

et al. 2016

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One of the major challenges for the NOx Storage and Reduction Catalysts technology used in automotive exhaust remains the sulfur susceptibility, which calls for efficient desulfation strategies. The sulfation and desulfation processes are systematically studied via measurements and mathematical modeling of the physicochemical processes. The role of oxygen storage which influences the reducing agents availability for desulfation is explained and a respective reaction model is presented. The bulk oxygen storage component appears to be involved in sulfur storage, which further emphasizes the importance of oxygen–sulfur storage interactions. Next, the observed release of sulfur species under lean mode is discussed along with a proposed reaction mechanism which involves SO2 formation via O2 reaction with elemental sulfur on the surface. The parameters of the complex reaction model are calibrated in order to reproduce the observed trends at least in a qualitative manner. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2117–2127, 2017

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The Impact of Sulphur Storage on Emissions From Three-Way Catalysts

Cited by 20 publications

References 2 publications

Chemisorption and Reaction of Sulfur Dioxide with Oxidized and Reduced Ceria Surfaces

Chemisorption and Reaction of Sulfur Dioxide with Oxidized and Reduced Ceria Surfaces

Regeneration of S-poisoned Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts for the combustion of methane

Modeling of the desulfation process in NO_x storage and reduction catalysts

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The Impact of Sulphur Storage on Emissions From Three-Way Catalysts

Cited by 20 publications

References 2 publications

Chemisorption and Reaction of Sulfur Dioxide with Oxidized and Reduced Ceria Surfaces

Chemisorption and Reaction of Sulfur Dioxide with Oxidized and Reduced Ceria Surfaces

Regeneration of S-poisoned Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts for the combustion of methane

Modeling of the desulfation process in NOx storage and reduction catalysts

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Product

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Modeling of the desulfation process in NO_x storage and reduction catalysts