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Study on thermal stabilities and symmetries of chemisorbed species formed on K-zeolites upon CO2 adsorption by TPD and in situ IR spectroscopy
Authors: Ganjkhanlou Yadolah | Bulánek Roman | Kikhtyanin Oleg | Frolich Karel
Year: 2018
Type of publication: článek v odborném periodiku
Name of source: Journal of Thermal Analysis and Calorimetry
Publisher name: Springer
Place: Dordrecht
Page from-to: 355-364
Titles:
Language Name Abstract Keywords
cze Studie tepelné stability a symetrie chemisorbovaných částic tvořených na K-zeolitech při CO2 adsorpci pomocí TPD a in situ IR spektroskopie K-zeolity s odlišnou strukturou, Si/Al poměrem a morfologií byly připraveny a charakterizovány různými technikami včetně in situ IR spektroskopie při CO2 adsorpci a CO2-TPD s cílem porozumět povaze bazických poloh přítomných na jejich povrchu a katalytických poloh pro aldolovou kondenzaci. TPD; zeolit; CO2 adsorpce; bazická poloha; K; IR spektroskopie
eng Study on thermal stabilities and symmetries of chemisorbed species formed on K-zeolites upon CO2 adsorption by TPD and in situ IR spectroscopy In the current study, K-zeolites with different structure, Si/Al ratio and morphology have been prepared and then characterized by different techniques including in situ IR spectroscopy upon CO2 sorption and CO2-TPD with the aim of understanding the nature of basic sites present on their surface acting as catalytic sites in aldol condensation reaction. Results showed that depending on the zeolite structure, pore size and Si/Al ratio, two categories of basic sites could be present in potassium modified zeolites. Symmetries of chemisorbed CO2 on these sites are different and comparing the results of TPD and in situ IR spectroscopy; it can be concluded that highly symmetric species (e.g., monodentate carbonates) have higher thermal stability than low symmetric adsorbed species (e.g., bidentate carbonates). It was found that in the zeolite with relatively smaller pore size or less accessible pores (e.g., MFI), second type of adsorbed species is more popular, while highly symmetric species tend to form on large pore zeolites and on materials with some mesoporosity (e.g., BEA or dealuminated FAU zeolites). It is observed that almost all the bidentate species are desorbed at 80 A degrees C, while monodentate species are thermally stable at least up to 130 A degrees C. Based on combination of experimental data obtained from TPD with IR spectroscopy results, origin and assignment of the TPD peaks were discussed. TPD; Zeolite; CO2 adsorption; Basic sites; Potassium; IR spectroscopy

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