X‐Ray Absorption and Emission Spectroscopy for Catalysis

Lamberti, Carlo; Bokhoven, Jeroen A. van

doi:10.1002/9781118844243.ch13

Cited by 32 publications

(38 citation statements)

References 167 publications

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“…Extended X-ray adsorption fine structure (EXAFS) data were measured at the Pd K-edge (24.35 keV) in transmission mode on pelletized samples at the SuperXAS beamline of the Swiss Light Source (SLS, Paul Scherrer Institut). The Fourier transformation of the k 2 -weighted EXAFS functions was performed the range 3-12 Å −1 [20]. Data reduction was performed using the Athena software package [21].…”

Section: Catalyst Characterizationmentioning

confidence: 99%

Deactivation Aspects of Methane Oxidation Catalysts Based on Palladium and ZSM-5

et al. 2016

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Catalytic methane oxidation is used in exhaust gas after treatment to reduce methane emissions in stationary combustion processes as well as in natural gas vehicles. Pd/zeolite catalysts provide higher activity than the commonly used Pd/Al2O3, but suffer from rapid deactivation under reaction conditions and in the presence of steam. This work presents a detailed study of deactivation of 1 wt.% Pd/H-ZSM-5 catalyst in reaction conditions in dry and wet feed including characterization of both the active phase and the support. Initially well-dispersed PdO particles are not stable and sinter immediately after the exposure to the reaction mixture even in dry feed and stabilize at lower dispersion level. Despite the reasonable methane oxidation activity exhibited by the large particles, the initial PdO particles could potentially provide a 40 o C lower methane oxidation temperature. In the presence of water in the feed at moderate temperature (450°C), support degradation governs the deactivation of the catalyst, which is evidenced by a significant decrease in BET surface area and generation of extra-framework aluminium species. These results suggest that active and stable catalysts could be obtained by careful choice and design of the support material with the aim to guarantee high dispersion of PdO.

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Section: Catalyst Characterizationmentioning

confidence: 99%

Deactivation Aspects of Methane Oxidation Catalysts Based on Palladium and ZSM-5

et al. 2016

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“…Synchrotron-based X-ray absorption spectroscopy (XAS) has developed to be the method of choice to determine redox-type reaction mechanisms by studying the electronic and local atomic structures of the metal of interest within the heterogeneous catalysts under operating conditions 23,24 . However, there are no reported XAS studies focused on deciphering the active sites in heterogeneous or homogeneous Wacker oxidation.…”

mentioning

confidence: 99%

“…Therefore, we used transient XAS, with which the dynamic speciation of palladium and copper can be determined. When the kinetically relevant step is directly affected by disturbing the system, be it by changing the pressure, concentration or temperature, the active site yields a quick response while the spectator species would elicit a slower response 24 .…”

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Elucidating the mechanism of heterogeneous Wacker oxidation over Pd-Cu/zeolite Y by transient XAS

et al. 2020

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The heterogenization of Wacker catalysts using chloride-free systems can potentially be a good alternative for the commercial homogeneous Wacker oxidation of ethylene, which utilizes excessive aqueous chloride solvents. However, the mechanism of the heterogeneous system has not been clarified, preventing the rational design of better catalysts. Here, we report a transient X-ray absorption spectroscopic (XAS) investigation of the heterogeneous Wacker oxidation over Pd-Cu/zeolite Y coupled with kinetic studies and chemometric analysis. Insight is obtained by operando quickXAS allowing the quantitative determination of rates and thereby revealing a rapid redox reaction involving copper. Our work demonstrates that copper is not only the site of oxygen activation, but is also involved in the formation of undesired carbon dioxide. Without detecting the presence of Cu(0) and Pd(I), our results suggest that two one-electron transfers to two Cu(II) ions to reoxidize Pd(0) is at work in this heterogeneous Wacker catalyst.

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“…Ранее было обнаружено [10], что температур-ная обработка электрокатализаторов PtCu/C при 300 • C приводит к структурным изменениям, проявляемым в сдвиге дифракционных максимумов на порошковых рентгеновских дифрактограммах. С целью выяснения ха-рактера таких изменений с изменениями в архитектуре биметаллических наночастиц PtCu в результате терми-ческой обработки в настоящей работе выполнены струк-турные исследования электрокатализаторов PtCu/C, полученных в результате температурной обработки при T = 350 • C. Структурные исследования выполнены с использованием 1) PtL 3 -и CuK-спектров рентгеновского поглощения в протяженной энергетической области за краем поглощения (extended X-ray absorption fine structure -EXAFS) [11][12][13][14]; 2) просвечивающей электронной микроскопии (transmission electron microscopy -ТЕМ); 3) порошковой рентгеновской дифракции (X-ray diffraction -XRD). Еще одной целью работы является установление чувствительности метода EXAFS-спектроскопии к изменениям архитектуры мно-жества биметаллических наночастиц в результате прове-денного термического воздействия.…”

Section: Introductionunclassified

Влияние термообработки на атомную структуру core-shell наночастиц PtCu в составе электрокатализаторов PtCu/C

Прядченко¹,

Беленов²,

Shemet³

et al. 2017

Физика Твердого Тела

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Электрокатализаторы PtCu/C, содержащие биметаллические наночастицы PtCu, синтезированы методом последовательного химического восстановления Cu 2+ и Pt(IV) в углеродной суспензии, приготовленной на основе водного раствора этиленгликоля. Исследование атомной структуры приготовленных наночастиц PtCu, а также полученных после термической обработки при 350 • C было выполнено с помощью PtL 3 -и CuK-спектров рентгеновского поглощения в протяженной области (EXAFS), методов просвечивающей электронной микроскопии (ТЕМ) и порошковой рентгеновской дифракции (XRD). Согласованный анализ TEM-микрофотографий, XRD-профилей, а также EXAFS-спектров позволил установить, что в состав полученных электрокатализаторов входят наночастицы PtCu со структурой Cu-ядро−Pt-оболочка, а также оксиды меди Cu 2 O и CuO. Термическая обработка электрокатализаторов при 350 • C приводит к сплавлению биметаллических наночастиц с формированием как однородных, так и упорядоченных твердых растворов PtCu, а также к частичному восстановлению медных оксидов.Исследования структурных характеристик наночастиц PtCu проведены при финансовой поддержке Южного федерального университета (грант № ВнГр-07.2017-06). Методика синтеза катализатора PtCu/C разработана в рамках выполнения гранта РФФИ № 14-29-04041 офи_м.

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X‐Ray Absorption and Emission Spectroscopy for Catalysis

Cited by 32 publications

References 167 publications

Deactivation Aspects of Methane Oxidation Catalysts Based on Palladium and ZSM-5

Deactivation Aspects of Methane Oxidation Catalysts Based on Palladium and ZSM-5

Elucidating the mechanism of heterogeneous Wacker oxidation over Pd-Cu/zeolite Y by transient XAS

Влияние термообработки на атомную структуру core-shell наночастиц PtCu в составе электрокатализаторов PtCu/C

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