Abstract
IR and Raman spectra of morpholine, a structure-directing agent, entrapped within the chabasite-related structures of both ALPO-34 and SAPO-34, are discussed. It is revealed that some vibrational features of the morpholine, which is present in the protonic form, are very sensitive to both host-guest (framework-morpholine) and guest-guest (morpholine-morpholine and morpholine-water) interactions occurring within the zeolites. FTIR spectroscopy shows that: (a) the NH2 group of the protonated morpholine is H-bonded to the zeolitic frameworks (more strongly in SAPO-34); (b) the CH2 vibrations in the 1500-1300cm-1 region are sensitive to the surrounding being different for the ALPO-34 compared with the SAPO-34. Raman spectroscopy reveals that the ring-breathing mode of the morpholine has a small red-shift (from 822cm-1 for the protonated molecule in solution, to 815cm-1 in SAPO-34), and is deeply decreased in intensity when the molecule is in the constrained space of the zeolitic cages. In this case, two new modes at 472 and 245cm-1, tentatively assigned to morpholine-framework motions, are also present. IR and Raman bands are better resolved in the case of morpholine in ALPO-34 where the template-framework interactions are weaker.
Original language | English |
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Pages (from-to) | 145-153 |
Number of pages | 9 |
Journal | Microporous and Mesoporous Materials |
Volume | 30 |
Issue number | 1 |
DOIs | |
Publication status | Published - Aug 1999 |
Keywords
- Aluminophosphates
- Characterization
- FTIR
- Morpholine
- Raman
- SAPO-34
- Synthesis
- TGA