Beidellite synthesis

It is a matter of some significance catalytically to be able to ascertain whether the aluminum present in a natural clay or its synthetic analogue is in a state of octahedral substitution (as in montmorillonite) or whether there is some tetrahedral substitution (as in beidellite). 27A1 MAS NMR readily provides the necessary answers. For example, Diddams et at. (462) in a study of the synthesis, characterization, and catalytic performance of synthetic beidellites and their pillared analogues, monitored the fate of AI from the gel precursor to the sheet silicate and to its pillared state by 27A1 MAS NMR (see... 

Fig. 80. 2,A1 (at 104.22 MHz) and 2 Si (at 79.8 MHz) MAS NMR spectra of (a) dried gel precursor used for synthesis (b) Na+-exchanged synthetic beidellite (c) Al3 + -exchanged variant of (b) (d) Al-pillared variant of (b). Peaks labeled SS are spinning sidebands. The precursor gel is seen to contain its silicon predominantly in the Si(4Si) environment (Q ), but some Si(3Si,OH) cannot be ruled out (462).

Diddams, P.A. et al. 1984. Synthesis, Characterization and Catalytic Activity of Beidellite-Montmorillonite Layered Silicates and their Pillared Analogues. J. Chemical Society (A) Chemical Communications 1340-42. 

An interesting comparison of catalytic activities of synthetic beidellite and montmorillonite and PILCS prepared from them was recently reported [69]. The reactions examined included secondary amine formation from cyclohexylamine, ester production from 1-hexene and acetic acid and ether synthesis from pentanol. In all cases, the reactivity of the PILCS was much lower than that of the unpillared clays, whereas the montmorillonite was generally more effective than the beidellite. These results are not surprising in that all of the reactions are Br<(Jnsted-acid-catalyzed and the observed decreased activity of the PILCS may derive from a greater loss of protons to the layers by the pillared clays. This is also in keeping with the findings of Occelli and Tindwa [5] that the PILCS are mainly Lewis acids after heat treatment. 

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