Characterization of synthetic dioctahedral clays by solid-state silicon-29 and aluminum-27 nuclear magnetic resonance spectrometry

Abstract--Ammonium-saponite is hydrothermally grown at temperatures below 300~ from a gel with an overall composition corresponding to (NH4)o.6Mg3Alo.,Sia.4Ot0(OH)2. Using 27A1 and 29Si solid-state Magic Angle Spinning NMR techniques it is demonstrated that synthetic ammonium-saponites have a rather constant Si/A1 Iv ratio (~5.5) and an AFV/A1 vl ratio that varies between 1.5 and 3.8. The above ratios are independent of the synthesis temperature, although an increasing amount of Si, I'4, and, to a lesser extent, Al are incorporated in an amorphous phase with increasing temperature. 27A1 MAS-NMR is unable to differentiate between AI at octahedral and AP + at interlayer sites. CEC, XRD, and the inability to swell prove the Al v~ to be mainly on the interlayer sites. Based on the NH4-exchange capacity, X-ray fluorescence, 27A1 and 29Si MAS-NMR, it is possible to calculate a relatively accurate structural formula.

Section: Resultsmentioning

confidence: 87%

Solid-State Nuclear Magnetic Resonance Spectroscopy on Synthetic Ammonium/Aluminum-Saponites

Kloprogge

Breukelaar

Wilson

et al. 1994

“…up at about -93, -88, and -82 ppm correspond (following Alma et aL, 1984) to Si bound to (0 Apv)(2 Alvi), (1 AlVI)(2 AlV'), and (2 Ally)(2 AlW), respectively. The modifications brought about by the calcination were marked by a decrease of the signal due to Si near (0 AlW)(2 A1 v~) and an increase of the contribution of the two other signals.…”

Section: Characterization O F the Synthetic Beidellitesmentioning

confidence: 96%

Preparation and Characterization of Bidimensional Zeolitic Structures Obtained from Synthetic Beidellite and Hydroxy-Aluminum Solutions

Schutz

Stone

Poncelet

et al. 1987

147

Abstract--Beidellite was synthesized hydrothermally from a noncrystalline gel at 320~ and 130 bar pressure. The beidellitic character of the product was verified by infrared spectroscopy on the NH4 § exchanged form. Intercalation was achieved with hydroxy-aluminum solutions having different OH/A1 molar ratios. The solutions were investigated by several methods, including 27A1 nuclear magnetic resonance. Essentially, two Al species were detected: monomeric A1 and a polymerized form containing A1 in four-fold coordination. This latter species was found to be selectively fixed in the interlamellar region, which resulted in a stable spacing of 18 ,~ at 110~ and 16.2 ~ at 700~ The pillared beidellites had specific surface areas of > 300 m2/g, mainly due to micropores. Both Br6nsted and Lewis acid sites were evidenced by infrared spectroscopy using pyridine as a probe molecule.

“…The most common to date are studies of the organisation of the silicate sheets, especially the problem of AI ordering by 29Si and 27A1 NMR (Alma et aL, 1984;Lipsicas et al, 1984;Serratosa, 1984a, 1984b;Thompson, 1984;Barron et al, 1985;Herrero et al, 1985;Kinsey et aL, 1985;Weiss et aL, 1987;Woessner, 1989). Then, there are investigations aimed at determining the structure and state of motion of water in the interlayer space by proton or deuterium magnetic resonance (Hougardy et aL, 1976;Woessner, 1979;Kadi-Hanifi, 1980;Lipsicas et al, 1985).…”

Section: Introductionmentioning

confidence: 99%

³⁹K Solid-State NMR Studies of Potassium Tecto- and Phyllosilicates: The In Situ Detection of Hydratable K⁺ in Smectites

Lambert

1992

Abstract--We report the first application of 39K solid-state NMR to the study of tecto-and phyllosilicates. Under high field (11.7 Tesla) and with the application of a spin-echo sequence, informative 39K spectra can be obtained for several compounds of interest to the geologist and the agronomist. Tectosilicates and phyllosilicates can be distinguished from the uncorrected frequency (Sc6) of the observed NMR peak. A series of montmorillonites submitted to increasing numbers of wetting and drying cycles was studied in order to discriminate between mobile and "fixed" forms of K+: when the spectra are run on hydrated samples, two different signals are observed corresponding to K § in different hydration states, and NMR data can be correlated with the amount of exchangeable K + measured by ion exchange. Thus, it appears that NMR can provide useful information on K fixation complementary to classical chemical methods.