27Al NMR

Figure 2 (Left) shows the 27Al NMR spectra for the aluminosilicates. All of them displayed a tetrahedral incorporation of aluminum inside the silica network. That is corroborated by the signal at 55 ppm [9, 10] which also become more intense with the decreasing of Si/Al ratio. Octahedral aluminum was observed just for the samples with the lowest Si/Al ratio. Tetrahedral aluminum gives place to strong Bronsted acid sites, which were identified by the interaction of these groups with pyridine that generates a...

Much recent work on NaCl/AlCl3 and related haloaluminate systems has concerned their behaviour as molten salts and non-aqueous electrolytes, and their use as aprotic reaction media.345-352 A1C13 with n-butylpyridinium chloride, and allied low-melting combinations provide useful model systems for fused salt behaviour and have attracted considerable attention on this account.353-356 There is evidence, particularly from 27Al NMR spectra, that Al2Cly and also Al3Clr0 are present in AlCl3-rich systems.354,355... 

Al NMR Ordered aluminum-incorporated mesoporous molecular sieves have been successfully synthesized in accordance with the experimental procedure mentioned above. 

Figure 4 31P and 27Al NMR data and molecular structure of the methylene-bridged... 

Figure 7 27Al NMR spectra of potassium aluminosilicate solution 6e prepared by Method 2 of mixing. Acquisition time was 0.067s and the number of scans averaged 6000. All data was collected in 4K and transformed in 32K. Spectrum 1 = normal mixing as in Method 1,2 = 22% of excess alkali added to the silicate soltuion before mixing with aluminate, 3 = 44% of excess alkali, 4 = 66% of excess alkali and 5 = 88% of excess alkali.

Because of the quadrupolar nature of Al, 27Al NMR spectra of aluminosilicate solutions exhibit broad lines from which it is possible to determine the coordination of Al and its connectivity with Si, but the precise environment of each Al atom cannot be defined. A peak for Al(OH>4 is observed at 75 - 79 ppm, and up to three peaks in the range 58 - 72 ppm which have been assigned to various Al(0Si)n(O")4 n building units. 

NMR peaks in the range of -187 to -194 ppm (19F-NMR) and 49 to 52 ppm (27Al-NMR) were observed for the TFA salts prepared via anhydrous routes. Thus, they correspond to tetrahedral aluminum coordinated by four fluorine atoms. This is demonstrated, for example, in the coupling for [PSH] [TFA] in CD3CN, which was observed as a sextet from 19F-27Al in the 19F-NMR, and a quintet from 27Al-19F in the solid state 27Al-NMR. 

Thomas, F. et al., Aluminum(III) speciation with acetate and oxalate, a potentiometric and 27Al NMR Study, Environ. Sci. Technol., 25, 1553, 1991. 

Fig. 9. Evolution with time of the NMR characteristics of AIPO4—02. (a) pH variation at 150°C from, 4N NMR (b) A1 atomic fraction in solution versus time at 150°C (c) in situ 27Al NMR spectra during the first 5 h of synthesis at 150°C (d) in situ l9F at 150"C (e) in situ 27A1 NMR spectra during nucleation and growth (f) chemical shift evolution of the prenucleation cluster peak vs time (with courtesy of C. In Gerardin and F. Taulelle).

Figure 5 27Al NMR spectra of potassium aluminosilicate solutions prepared by Method 1 of mixing. Acquisition time was 0.067s and the number of scans averaged 10000. All data was collected in 4K and transformed in 32K.

TABLE II 27Al NMR CHEMICAL SHIFT RANGES (PPM) FOR ALUMINOSILICATE SOLUTIONS. 

Compounds of Other Group 13 Elements. A review of 19F and 27Al NMR studies of organoaluminium fluorides has appeared.635... 

Multinuclear NMR (1H, 13C, 31P, 27Al), together with 2-D 111-111 NOESY data, were used to study the complexation of coenzyme NAD+ by Al3+-evidence was found for A1(LH2)3+, A1(LH)2+ and A1L2. ll0° The liquid-state 27Al NMR spectra were used to identify aluminium species formed by the... 

Figure 8. Normalized 27Al-NMR line intensity as a function of flip angles. (The intensities for tetra- and octahedral Al atoms are normalized to the total amount of Al in mordenite.) (Reproduced with permission from ref. 34. Copyright 1988 Elsevier.)...

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