Sulfur Poisoning of a Pt/Al2O3 Oxidation Catalyst: Understanding of SO2, SO3 and H2SO4 Impacts

Hamzehlouyan, Tayebeh; Sampara, Chaitanya S.; Li, Juhnui; Kumar, Ashok; Epling, William S.

doi:10.1007/s11244-016-0592-0

Cited by 32 publications

(23 citation statements)

References 19 publications

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“…As already mentioned, with rising temperature SO2 is oxidized to SO3 over the noble metal sites, namely Pt, and finally, H2SO4 is formed in the presence of H2O [20]. As a consequence, surface or bulk sulfates/ sulfites are formed at the noble metal sites or with the support.…”

Section: Laboratory Catalyst Testsmentioning

confidence: 87%

“…This points out a slower deactivation of the ceria-zirconia supported sample. Such an effect could be due to the oxidation of some SO2 at the Pt sites [20], present as monometallic nanoparticles not in the close vicinity of Pd (according to the HAADF-STEM images in Fig. 1), with storage as bulk support sulfates/sulfites, which probably additionally delays the poisoning of the Pd active sites.…”

Section: Laboratory Catalyst Testsmentioning

confidence: 99%

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Regeneration of Sulfur Poisoned Pd–Pt/CeO2–ZrO2–Y2O3–La2O3 and Pd–Pt/Al2O3 Methane Oxidation Catalysts

et al. 2018

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The poisoning of Pd-Pt/Al2O3 and Pd-Pt/CeO2-ZrO2-Y2O3-La2O3 methane oxidation catalysts by SO2 was studied under conditions typical for lean burn gas engines. Regeneration of sulfur-poisoned catalysts was achieved by applying rich conditions at 500 °C and 550 °C. The presence of NOx resulted in a slower deactivation rate. While Pd-Pt/CeO2-ZrO2-Y2O3-La2O3 showed a superior catalytic activity, durability and regeneration ability over Pd-Pt/Al2O3 under NOx-free reaction conditions, its reactivation by a rich treatment was strongly inhibited if NOx was present during the aging and regeneration process. Operando X-ray absorption spectroscopy (XAS) was used to monitor the evolution of Pd and Pt during poisoning and regeneration, revealing the formation of PdS and metallic Pd during reactivation of Pd-Pt/Al2O3, followed by transition to PdO after changing to lean reaction gas mixture. On the other hand, Pd species supported on CeO2-ZrO2-Y2O3-La2O3 could not be reduced by rich treatment and no regeneration occurred.

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Section: Laboratory Catalyst Testsmentioning

confidence: 87%

Section: Laboratory Catalyst Testsmentioning

confidence: 99%

Regeneration of Sulfur Poisoned Pd–Pt/CeO2–ZrO2–Y2O3–La2O3 and Pd–Pt/Al2O3 Methane Oxidation Catalysts

et al. 2018

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“…All reduction reactions involving hydrogen consumption have been reported in the Appendix A. The H 2 consumption peaks were identified as the reduction of PdSO 4 (peak centered at 223 • C for Pd-monometallic [39]), surface sulfites (337 • C [53]), surface aluminum sulfates (from 437 • C to 510 • C), surface magnesium/ceria sulfates (542 • C [14,54]), and bulk-like sulfates species (579 • C [38]). Surface aluminum sulfates and bulk-like sulfates were slightly shifted towards higher temperatures (+20 • C) for Mg-Al 2 O 3 and Mg-Ce-Al 2 O 3 samples.…”

Section: Sulfur Regenerationmentioning

confidence: 99%

Sulfur Poisoning Effects on Modern Lean NOx Trap Catalysts Components

2019

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In the present work, a series of different materials was investigated in order to enhance the understanding of the role of modern lean NO x trap (LNT) components on the sulfur poisoning and regeneration characteristics. Nine different types of model catalysts were prepared, which mainly consisted of three compounds: (i) Al 2 O 3 , (ii) Mg/Al 2 O 3 , and (iii) Mg/Ce/Al 2 O 3 mixed with Pt, Pd, and Pt-Pd. A micro flow reactor and a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) were employed in order to investigate the evolution and stability of the species formed during SO 2 poisoning. The results showed that the addition of palladium and magnesium into the LNT formulation can be beneficial for the catalyst desulfation due mainly to the ability to release the sulfur trapped at relatively low temperatures. This was especially evident for Pd/Mg/Al 2 O 3 model catalyst, which demonstrated an efficient LNT desulfation with low H 2 consumption. In contrast, the addition of ceria was found to increase the formation of bulk sulfate species during SO 2 poisoning, which requires higher temperatures for the sulfur removal. The noble metal nature was also observed to play an important role on the SO x storage and release properties. Monometallic Pd-based catalysts exhibited the formation of surface palladium sulfate species during SO 2 exposure, whereas Pt-Pd bimetallic formulations presented higher stability of the sulfur species formed compared to the corresponding Pt-and Pd-monometallic samples.Catalysts 2019, 9, 492 2 of 18 urea [4]. Nevertheless, the LNT system is highly susceptible to sulfur, and its performance can be severely affected as NO x storage sites are blocked by sulfur [5][6][7]. Sulfates formed on the NO x storage sites have higher thermal stability than nitrates and nitrites and, therefore, their decomposition needs very high temperatures and alternating rich/lean exhaust mixtures [8,9]. This does not only lead to higher fuel consumption due to regular desulfation events, but may also cause structural deactivation of the catalyst, such as sintering of precious metals and the formation of mixed oxides (e.g., BaAl 2 O 4 for the reaction between Al 2 O 3 and BaO at high temperatures), affecting the overall NO x storage and reduction activity of the catalyst [10][11][12].Therefore, the sulfur tolerance of modern LNT catalysts should be improved by replacing the NO x trapping material with a component with lower affinity towards sulfation, and with enhanced desorption of sulfur species during regeneration. Barium is frequently employed as a storage material because of its high thermal stability, however, it is responsible for the major LNT catalyst deterioration due to its high affinity for sulfation [13]. Ji et al. [14] studied the incorporation of ceria to Ba-based LNT catalysts and determined to provide a positive impact on LNT performance in the presence of sulfur. Ceria was found to enhance sulfur tolerance of the LNT catalyst by storing sulfur species, which mitigates the sulfation o...

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“…Especially with gold nanoparticles the complete oxidation at very low temperatures of −70 °C could be realized . Compared to the high activity, however, the main disadvantages are the high price of the active components and the susceptibility to poisoning and deactivation, e. g. by SO 2 . Therefore, the use of large quantities of these materials under ambient conditions is not feasible.…”

Section: Introductionmentioning

confidence: 99%

“…[13] Compared to the high activity, however, the main disadvantages are the high price of the active components and the susceptibility to poisoning and deactivation, e. g. by SO 2 . [14][15][16] Therefore, the use of large quantities of these materials under ambient conditions is not feasible. In the search for alternative and less expensive catalysts, materials based on metal oxides such as cobalt oxide, manganese oxide, cerium oxide, copper oxide and mixed oxides were investigated.…”

Section: Introductionmentioning

confidence: 99%

Molecular Precursors for Tailoring Humidity Tolerance of Nanoscale Hopcalite Catalysts Via Flame Spray Pyrolysis

et al. 2019

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A systematic investigation of copper‐ and manganese‐carboxylate precursors derived from various organic acids (arylcarboxylate, alkylcarboxyate) and their transformation into copper manganese nanoparticles via flame spray pyrolysis (FSP) reveals significant impact on their physical and catalytic properties. A sodium‐free protocol is essential to achieve high purity copper(II) and manganese(II) 2‐ethylhexanoates, benzoates, 1‐naphthenates and 9‐ anthracenates as revealed by infrared spectroscopy (IR) and thermogravimetry (TG). In order to exclude the influence of other parameters, the FSP syntheses were carried out using fixed air/feed ratio. Especially aromatic precursors lead to smaller nanoparticles with high surface areas up to 180 m2g−1 and that these also have a higher carbon content. TPR investigations have shown that the copper and manganese atoms are in close contact with each other, which significantly reduces their reduction temperature. In catalytic CO oxidation, all samples synthesized from organometallic precursors have shown higher CO conversions at room temperature under dry conditions and improved long‐term stability under wet conditions compared to a commercial reference. The activity depends mainly on the Cu : Mn ratio and the specific surface area. At room temperature under dry conditions, catalytic CO conversion exceeding 80 % could be achieved. A decreased deactivation rate under humid conditions could be related to an increased carbon content of the nanocatalysts. By optimization of the synthesis parameters and the use of pure precursors, it was possible to show that flame spray pyrolysis is an efficient, scalable and single‐stage synthesis method for Hopcalite nanoparticles, which additionally provides more active catalysts than those from alternative synthesis methods.

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Sulfur Poisoning of a Pt/Al2O3 Oxidation Catalyst: Understanding of SO2, SO3 and H2SO4 Impacts

Cited by 32 publications

References 19 publications

Regeneration of Sulfur Poisoned Pd–Pt/CeO2–ZrO2–Y2O3–La2O3 and Pd–Pt/Al2O3 Methane Oxidation Catalysts

Regeneration of Sulfur Poisoned Pd–Pt/CeO2–ZrO2–Y2O3–La2O3 and Pd–Pt/Al2O3 Methane Oxidation Catalysts

Sulfur Poisoning Effects on Modern Lean NOx Trap Catalysts Components

Molecular Precursors for Tailoring Humidity Tolerance of Nanoscale Hopcalite Catalysts Via Flame Spray Pyrolysis

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