On the nature of Pb species in Pb-exchanged zeolite stellerite (STI): A combined experimental and theoretical study

Roos, Diana P.; Scheinost, Andreas C.; Churakov, Sergey V.; Nagashima, Mariko; Cametti, Georgia

doi:10.1016/j.micromeso.2021.111444

Cited by 2 publications

(24 citation statements)

References 39 publications

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“…From RT to 100°C, the unit-cell volume gradually decreases by 3.5% with respect to that measured at RT [19]. This change agrees with the common trend observed for STI framework type zeolites (Fig.…”

Section: Structural Modi Cations Upon Heatingsupporting

confidence: 88%

“…At 75°C, the structure is partially hydrated and between 100 and 125°C, in correspondence of the increase of the unit-cell volume, the cluster formation starts. Residual water might be retained up to 250-270°C, and in a subsequent step completely released, as indicated by the slight unit-cell volume decrease between 250 and 450°C and by TGA curve [19]. The clustering of Pb(OH) + species during the dehydration prevents the collapse of the structure because no enough space is left in the channels to accommodate the " ipping" of the tetrahedra, which would be involved in the breaking of T-O-T bonds, typical of zeolites with STI framework type.…”

Section: Discussionmentioning

confidence: 99%

“…The latter was re ned as several low occupied sites, close to each other. At RT, the EF species were mainly concentrated at the centre of the ten-membered ring channels and in the middle of the eight-membered ring window between two t-sti-1* cavities [19]. With the increase of temperature and subsequent shrinking of these channels, Pb and eventually OH groups came closer to the wall of the framework.…”

Section: Structural Modi Cations Upon Heatingmentioning

confidence: 98%

“…The most surprising observation is the expansion of the zeolitic framework after the initial contraction, which is induced by dehydration. According to TGA [19] and IR analysis, H 2 O is lost as a function of increasing temperature whereas, as demonstrated by IR spectra collected at higher temperatures, the OHgroups are retained in the dehydrated structure.…”

Section: Structural Models Of the High Temperature Phasementioning

confidence: 99%

“…A distinction between H 2 O and OHby infrared (IR) analysis was complicated by the fact that these molecules vibrate at similar frequencies. Vibrational Density of States (VDOS) curves were calculated for hydrogen atoms (H) based on the DFT-equilibrated Pb-stellerite structure at room temperature from our previous study [19]. Different bands in the IR spectra were assigned to speci c molecular groups (Supplementary material S1): vibrations of H 2 O are found as a sharp peak between 1500 and 1800 cm -1 and a broader peak between 3000 and 3800 cm -1 , while only one rather sharp vibrational peak of OHis found between 3500 and 3800 cm -1 (Fig.…”

Section: Structural Modi Cations Upon Heatingmentioning

confidence: 99%

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Pbx(OH)y cluster formation in STI framework-type zeolites: anomalous thermal behaviour and increased thermal stability

Cametti

Roos

Prieur

et al. 2022

Preprint

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For the first time, the structural investigation of a Pb-exchanged zeolite (Pb13.4(OH)10Al17.4Si54.6O144 ∙38H2O) with STI framework type, revealed a highly unusual and intriguing sudden volume increase under continuous heating. Understanding the fundamental mechanisms leading to such an unusual behaviour is essential for technological applications and interpretation of chemical bonding in zeolites. The dehydration was tracked in situ from 25 to 450 °C by single crystal X-ray diffraction, infrared and X-ray absorption spectroscopy. Further interpretation of the experimental observations was supported by ab initio molecular dynamics simulations. Initially, Pb-STI unit-cell volume contracts (ΔV = -3.5%) from 25 to 100°C. This agrees with the trend observed in STI zeolites. Surprisingly, at 125°C, the framework expanded (ΔV = +2%), adopting a configuration, which resembles that of the room temperature structure. Upon heating, the structure loses H2O but no de-hydroxylation occurred. The key mechanism leading to the sudden volume increase was found to be the formation of Pbx(OH)y clusters, which prevent the shrinking of the channels, rupture of the tetrahedral bonds and occlusion of the pores. This zeolite has therefore an increased thermal stability with respect to other STI metal-exchanged zeolites, with important consequences on its applications.

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Section: Structural Modi Cations Upon Heatingsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Section: Structural Modi Cations Upon Heatingmentioning

confidence: 98%

Section: Structural Models Of the High Temperature Phasementioning

confidence: 99%

Section: Structural Modi Cations Upon Heatingmentioning

confidence: 99%

See 3 more Smart Citations

Pbx(OH)y cluster formation in STI framework-type zeolites: anomalous thermal behaviour and increased thermal stability

Cametti

Roos

Prieur

et al. 2022

Preprint

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Pbx(OH)y cluster formation and anomalous thermal behaviour in STI framework-type zeolites

Cametti¹,

Roos²,

Prieur

et al. 2022

Sci Rep

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For the first time, the structural investigation of a Pb-exchanged zeolite (Pb13.4(OH)10Al17.4Si54.6O144 ∙38H2O) with STI framework type, revealed a highly unusual and intriguing sudden volume increase under continuous heating. Understanding the fundamental mechanisms leading to such an unusual behaviour is essential for technological applications and interpretation of chemical bonding in zeolites. The dehydration was tracked in situ from 25 to 450 °C by single crystal X-ray diffraction, infrared and X-ray absorption spectroscopy. Further interpretation of the experimental observations was supported by ab initio molecular dynamics simulations. Initially, Pb-STI unit-cell volume contracts (ΔV = − 3.5%) from 25 to 100 °C. This agrees with the trend observed in STI zeolites. Surprisingly, at 125 °C, the framework expanded (ΔV = + 2%), adopting a configuration, which resembles that of the room temperature structure. Upon heating, the structure loses H2O but no de-hydroxylation occurred. The key mechanism leading to the sudden volume increase was found to be the formation of Pbx(OH)y clusters, which prevent the shrinking of the channels, rupture of the tetrahedral bonds and occlusion of the pores. This zeolite has therefore an increased thermal stability with respect to other STI metal-exchanged zeolites, with important consequences on its applications.

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On the nature of Pb species in Pb-exchanged zeolite stellerite (STI): A combined experimental and theoretical study

Cited by 2 publications

References 39 publications

Pbx(OH)y cluster formation in STI framework-type zeolites: anomalous thermal behaviour and increased thermal stability

Pbx(OH)y cluster formation in STI framework-type zeolites: anomalous thermal behaviour and increased thermal stability

Pbx(OH)y cluster formation and anomalous thermal behaviour in STI framework-type zeolites

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