Deceleration of SO2 poisoning on PtPd/Al2O3 catalyst during complete methane oxidation

Sadokhina, Nadezda; Smedler, Gudmund; Nylén, Ulf; Olofsson, Marcus; Olsson, Louise

doi:10.1016/j.apcatb.2018.05.018

Cited by 55 publications

(28 citation statements)

References 59 publications

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“…In the presence of NOx the deactivation process follows a similar trend for the Pd-Pt/CZ sample, with complete deactivation after about 13 h SO2 exposure. In contrast, for Pd-Pt/Al2O3 the deactivation is significantly slowed down, as recently reported also by Sadokhina et al [28]. Moreover, the final state shows about 15 % higher 7 CH4 conversion in comparison to the catalyst poisoned in the absence of NOx.…”

Section: Laboratory Catalyst Testssupporting

confidence: 70%

“…Moreover, the final state shows about 15 % higher 7 CH4 conversion in comparison to the catalyst poisoned in the absence of NOx. On the one hand, this effect could be due to the positive contribution of NOx on CH4 conversion over Pd-Pt/Al2O3 catalysts [28], which is also known do decelerate the H2O deactivation process [29,30]. On the other hand, considering that in both cases irrespective of the NOx presence the SO2-exposure led to complete saturation of the catalysts (after approx.10 h for Pd-Pt/Al2O3…”

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 Testssupporting

confidence: 70%

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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“…Furthermore, the absence of the peak at approximately 1465 cm −1 associated with PdSO 4 demonstrates that no stable sulfates are formed on Pd surface for Pt-Pd bimetallic samples under the conditions investigated. These results are consistent with the study by Sadokhina et al [44], where Pd/Pt/Al 2 O 3 was more resistant to sulfur poisoning compared to Pd/Al 2 O 3 during methane oxidation.…”

Section: Influence Of Sulfur On Different Precious Metal Speciessupporting

confidence: 93%

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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“…It is well known that sulphur and phosphorus originating from fuel and/or lubricating oil decrease efficiency of diesel and natural gas oxidation catalysts, for example, [11,[15][16][17][18]. For example, in the Pd-rich catalysts for methane oxidation in natural gas engine exhausts, aluminum sulphate species formed under SO 2 exposure.…”

Section: Introductionmentioning

confidence: 99%

“…For example, in the Pd-rich catalysts for methane oxidation in natural gas engine exhausts, aluminum sulphate species formed under SO 2 exposure. This inhibited the CH 4 oxidation reaction in a broad temperature range [18]. In the Pt-based diesel oxidation catalysts, the formation of phosphates decreased the specific surface area of the catalyst and decreased catalyst efficiency [16].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Characteristics of Vehicle-Aged Heavy-Duty Diesel Oxidation Catalyst and Natural Gas Three-Way Catalyst

et al. 2019

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Techniques to control vehicle engine emissions have been under increasing need for development during the last few years in the more and more strictly regulated society. In this study, vehicle-aged heavy-duty catalysts from diesel and natural gas engines were analyzed using a cross-sectional electron microscopy method with both a scanning electron microscope and a transmission electron microscope. Also, additional supporting characterization methods including X-ray diffractometry, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and catalytic performance analyses were used to reveal the ageing effects. Structural and elemental investigations were performed on these samples, and the effect of real-life ageing of the catalyst was studied in comparison with fresh catalyst samples. In the real-life use of two different catalysts, the poison penetration varied greatly depending on the engine and fuel at hand: the diesel oxidation catalyst appeared to suffer more thorough changes than the natural gas catalyst, which was affected only in the inlet part of the catalyst. The most common poison, sulphur, in the diesel oxidation catalyst was connected to cerium-rich areas. On the other hand, the severities of the ageing effects were more pronounced in the natural gas catalyst, with heavy structural changes in the washcoat and high concentrations of poisons, mainly zinc, phosphorus and silicon, on the surface of the inlet part.

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Deceleration of SO2 poisoning on PtPd/Al2O3 catalyst during complete methane oxidation

Cited by 55 publications

References 59 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

Microstructural Characteristics of Vehicle-Aged Heavy-Duty Diesel Oxidation Catalyst and Natural Gas Three-Way Catalyst

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