Details
| Original language | English |
|---|---|
| Pages (from-to) | 1641-1649 |
| Number of pages | 9 |
| Journal | Zeitschrift fur Anorganische und Allgemeine Chemie |
| Volume | 646 |
| Issue number | 19 |
| Publication status | Published - 14 Oct 2020 |
Abstract
Basic sodalite (hydroxysodalite) was synthesized from two Si-Al sources: (1) kaolin to obtain |Na7.5(OH)1.5(H2O)3.5|[AlSiO4]6 sodalites (SOD) with small crystals (< 0.5 μm) and (2) a mixture of cristobalite and corundum (CC) to obtain larger microcrystals (1–5 μm) with ideal composition |Na8(OH)2(H2O)2|[AlSiO4]6. Both SOD were exposed to thermal stress by long-time heating at 773 K under open conditions, in N2 and CO2 atmosphere and in presence of a NaOH-Na2CO3 melt. The crystals obtained from kaolin were dehydrated and developed remarkable degrees of carbonate cage fillings already under open conditions. The large microcrystals obtained from CC exhibit this effect only at very low scale even after long-time heating in CO2 atmosphere. Whereas heating in presence of the melt showed no effect, investigations in CO2 clearly indicate an intra-cage reaction between CO2 and the enclathrated [Na4OH]3+ ions as the carbonate generating mechanism instead of destruction of hydroxysodalite followed by recrystallization. A model is proposed, in which cage fillings [Na3□]3+ with a vacancy in the Na tetrahedron known from dehydrated hydrosodalites |Na6|[AlSiO4]6 are required to induce the intra-cage reaction of hydroxysodalite. As those fillings only occur in a noticeable number in dehydrated hydroxysodalite obtained from kaolin, the large extent of the carbonate formation inside this sample becomes obvious. The results are significant for future improvement of hydroxysodalite membranes.
Keywords
- Aluminosilicates, IR spectroscopy, Microporous materials, Phase transitions, X-ray diffraction
ASJC Scopus subject areas
- Chemistry(all)
- Inorganic Chemistry
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In: Zeitschrift fur Anorganische und Allgemeine Chemie, Vol. 646, No. 19, 14.10.2020, p. 1641-1649.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - On the Carbonate Formation in Thermally Stressed Hydroxysodalite
T2 - Some Facts to Notice for SOD Application in Separation Processes
AU - Peschke, Irma
AU - Hildebrand, Hagen
AU - Pioch, Robert
AU - Buhl, Josef Christian
N1 - Funding Information: IP and JB gratefully acknowledge the Deutsche Forschungsgemeinschaft (DFG) for financial support of the project BU1020/22–1.
PY - 2020/10/14
Y1 - 2020/10/14
N2 - Basic sodalite (hydroxysodalite) was synthesized from two Si-Al sources: (1) kaolin to obtain |Na7.5(OH)1.5(H2O)3.5|[AlSiO4]6 sodalites (SOD) with small crystals (< 0.5 μm) and (2) a mixture of cristobalite and corundum (CC) to obtain larger microcrystals (1–5 μm) with ideal composition |Na8(OH)2(H2O)2|[AlSiO4]6. Both SOD were exposed to thermal stress by long-time heating at 773 K under open conditions, in N2 and CO2 atmosphere and in presence of a NaOH-Na2CO3 melt. The crystals obtained from kaolin were dehydrated and developed remarkable degrees of carbonate cage fillings already under open conditions. The large microcrystals obtained from CC exhibit this effect only at very low scale even after long-time heating in CO2 atmosphere. Whereas heating in presence of the melt showed no effect, investigations in CO2 clearly indicate an intra-cage reaction between CO2 and the enclathrated [Na4OH]3+ ions as the carbonate generating mechanism instead of destruction of hydroxysodalite followed by recrystallization. A model is proposed, in which cage fillings [Na3□]3+ with a vacancy in the Na tetrahedron known from dehydrated hydrosodalites |Na6|[AlSiO4]6 are required to induce the intra-cage reaction of hydroxysodalite. As those fillings only occur in a noticeable number in dehydrated hydroxysodalite obtained from kaolin, the large extent of the carbonate formation inside this sample becomes obvious. The results are significant for future improvement of hydroxysodalite membranes.
AB - Basic sodalite (hydroxysodalite) was synthesized from two Si-Al sources: (1) kaolin to obtain |Na7.5(OH)1.5(H2O)3.5|[AlSiO4]6 sodalites (SOD) with small crystals (< 0.5 μm) and (2) a mixture of cristobalite and corundum (CC) to obtain larger microcrystals (1–5 μm) with ideal composition |Na8(OH)2(H2O)2|[AlSiO4]6. Both SOD were exposed to thermal stress by long-time heating at 773 K under open conditions, in N2 and CO2 atmosphere and in presence of a NaOH-Na2CO3 melt. The crystals obtained from kaolin were dehydrated and developed remarkable degrees of carbonate cage fillings already under open conditions. The large microcrystals obtained from CC exhibit this effect only at very low scale even after long-time heating in CO2 atmosphere. Whereas heating in presence of the melt showed no effect, investigations in CO2 clearly indicate an intra-cage reaction between CO2 and the enclathrated [Na4OH]3+ ions as the carbonate generating mechanism instead of destruction of hydroxysodalite followed by recrystallization. A model is proposed, in which cage fillings [Na3□]3+ with a vacancy in the Na tetrahedron known from dehydrated hydrosodalites |Na6|[AlSiO4]6 are required to induce the intra-cage reaction of hydroxysodalite. As those fillings only occur in a noticeable number in dehydrated hydroxysodalite obtained from kaolin, the large extent of the carbonate formation inside this sample becomes obvious. The results are significant for future improvement of hydroxysodalite membranes.
KW - Aluminosilicates
KW - IR spectroscopy
KW - Microporous materials
KW - Phase transitions
KW - X-ray diffraction
UR - http://www.scopus.com/inward/record.url?scp=85087295900&partnerID=8YFLogxK
U2 - 10.1002/zaac.202000051
DO - 10.1002/zaac.202000051
M3 - Article
AN - SCOPUS:85087295900
VL - 646
SP - 1641
EP - 1649
JO - Zeitschrift fur Anorganische und Allgemeine Chemie
JF - Zeitschrift fur Anorganische und Allgemeine Chemie
SN - 0044-2313
IS - 19
ER -