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Download file29Si NMR Studies of Zeolite Precursor Solutions
journal contribution
posted on 2006-01-12, 00:00 authored by Chil-Hung Cheng, Daniel F. ShantzSolution 29Si NMR spectroscopy results of zeolite precursor solutions of composition 1 SiO2:4 C2H5OH:0.36/n R+n[OH-]n:20 H2O are reported. This work employs isotopically enriched 29Si materials to aid in
spectral interpretation. Using both 1D and 2D methods, spectra of solutions containing tetrapropylammonium
hydroxide are wholly consistent with the existing silicate chemistry literature and indicate that the majority
of the species are high-symmetry silicate clusters previously observed in aqueous solutions. The results are
inconsistent with the nanoblock or nanoslab model proposed by Kirschhock and co-workers. Mixtures
containing the 4,4‘-trimethylene-bis(1,1‘-dimethylpiperidinium) dihydroxide cation were also studied. These
mixtures have similar speciation to the TPA solutions, although the relative populations of the species are
different. Preliminary variable temperature 29Si NMR of these mixtures shows that the exchange properties
of the high-symmetry silicate species, most notably the tetrahedral tetramer, depend on the organocation
identity.
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Keywords
mixturespeciesorganocation identityexchange properties29 Si materialssilicate chemistry literatureTPA solutionszeolite precursor solutionsnanoslab modeltemperature 29 Si NMRZeolite Precursor Solutions Solution 29 Si NMR spectroscopy results1 Dtetrapropylammonium hydroxideOHtetrahedral tetramer2 D methods29 Si NMR Studies