I synthesized some ZSM-5 in my lab and did 27Al-NMR on it. From the literature, generally there was a peak at 55 ppm and 0 ppm to tell framework Al or not. But in my results, although there was a small peak at 0 ppm, there were a broad peak at 10-40 ppm and another broad peak at 40-60 ppm. Why?
Hi Junfei, this looks like a disordered aluminium spectra with a range of AlO6, AlO5 and AlO5 resonances (see 27Al NMR on glasses - Chapter 27Al NMR Studies of Aluminosilicate Glasses
). It seems like your samples has quite extreme local disorder and is probably not single phase ZSM-5.Best, G
Dear Gregory J Rees ,
Thank you very much for your reply. According to your comment, there are a lot of AlO5 (10-50ppm), some AlO6 (0ppm), and much less AlO4 (55ppm). Could you please give more explanation on what may cause this kind of local disorder?
One point I want to mention is that the sample I used for NMR is ZSM-5 film grown on the cordierite (Mg2Al4Si5O18). Please check the attachment below for the 27Al-NMR results of cordierite. From the results, cordierite also showed a wide range of peak at 0-60ppm, and the peak at 40-60ppm was an extra peak in addition to the cordierite substrate.
Best,
Junfei
Ah ok, so most of the broad component is the disordered cordierite.
The narrow (more ordered) resonance at 55 ppm is your zeolite.
The film growth seems to be having a greater affect on the cordierite, causing a shift change and possibly an increase in AlO6 (~15 ppm). I presume the experimental parameters are the same in both.
You could probably deconvolute these resonances using a MQMAS.
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