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Two crystallographically non-equivalent and unequally populated tetrahedral aluminium sites are identified by magic-angle-spinning 27Al n.m.r. spectroscopy in the parent zeolite (Si/Al = 4.24 ± 0.05); after treatment with SiCl4 at 500 °C relatively mobile, 6-co-ordinated aluminium is generated (most of it released from one of the tetrahedral sites) and there is evidence for some realumination of the tetrahedral framework.
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Klinowski et al. (1983) studied this question.
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