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CO and NO adsorption on VOx/SBA-15 catalysts: an FT-IR spectroscopic study
Authors: Bulánek Roman | Drenchev Nikola Lyudmilov | Čičmanec Pavel | Setnička Michal
Year: 2013
Type of publication: článek v odborném periodiku
Name of source: Adsorption - Journal of the International Adsorption Society
Publisher name: Springer
Place: Dordrecht
Page from-to: 339-347
Titles:
Language Name Abstract Keywords
cze CO a NO adsoprce na VOx/SBA-15 katalyzátorech: FT-IR spektroskopická studie Adsoprce CO a NO na VO (x)-SBA-15 mezoporézních materiálech s odlišným obsahem vanadu byla zkoumána pomocí FT-IR spektroskopie. Vanadiové komplexy byly redukovány in situ pomocí vodíkové atmosféry při 450 C po 3 h. Spektra redukovaných vzorků vykazují vzrůstající intenzitu silanolových skupin zapříčiněnou disocizcí V-O(Si) vazbami a tvorbou nových H-O-(Si) vazeb. vanad; SBA-15; FT-IR; karbonyly; nitrozyly
eng CO and NO adsorption on VOx/SBA-15 catalysts: an FT-IR spectroscopic study The adsorption of CO and NO over VO (x) -SBA-15 mesoporous materials with different vanadium content was investigated by FT-IR spectroscopy. Vanadium complexes were reduced in situ by hydrogen atmosphere at 450 A degrees C for 3 h. Spectra of reduced samples show increasing in intensity of silanol groups, caused by dissociation of V-O(Si) bonds and formation of new H-O(Si) bonds. Reduction occurs with formation of water. The band corresponds to overtone of V=O stretching modes decreases in intensity because of oxygen withdrawing from V=O species. Presence of V4+ and V3+ species was observed. Inspection of CO adsorbed IR spectra evidenced existence at least two different type of V3+-CO complexes on the silica surface differing in both stretching frequencies and complex stabilities. We did not found principal difference between spectra of absorbed CO at -196 A degrees C on the samples with different concentration of vanadium, probably because of relative low degree of reduction. As well as heterogeneity of surface V3+ and V4+ species was evidenced by adsorption of NO. Both V3+ and V4+ ions possess two effective coordinative vacancies and as a result can adsorb two NO molecules forming dinitrosyls. A part of V3+ cations forms only mononitrosyls characterize by band at 1724 cm(-1). Results obtained after NO adsorption reveal existence of three different kinds of vanadium species. Probably two of them are isolated and associated vanadium sites. The third type of vanadium has different surrounding than other two types. It was demonstrated that NO is a better probe than CO for testing the oxidation and coordination state of reduced vanadium species. vanadium; SBA-15; FT-IR; carbonyls; nitrosyls

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