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Nature of the acidic protons in H-mordenite and H-MCM-22 as studied by variable temperature 1H MAS NMR

✍ Scribed by Toshihide Baba; Norito Komatsu; Yoshio Ono; Hisashi Sugisawa; Toshiro Takahashi

Publisher
Elsevier Science
Year
1998
Tongue
English
Weight
198 KB
Volume
22
Category
Article
ISSN
1387-1811

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✦ Synopsis

The temperature dependence of the line-shape of 1H MAS NMR spectra of H-mordenite and H-MCM-22 was examined. Upon raising the temperature of measurements stepwise from 298 to 503 K, the line-width of 1H MAS NMR of acidic protons in H-mordenite with SiO 2 /Al 2 O 3 ratio of 106 increased, went through a maximum, and then decreased. This temperature dependence of the spectrum was explained by the thermal motion of protons. The activation energy of the thermal motion was 28±2 kJ/mol. On the other hand, the temperature dependence of the line-width due to acidic protons in H-mordenite with SiO 2 /Al 2 O 3 ratios of 19 and 40 and in H-MCM-22 with SiO 2 /Al 2 O 3 ratio of 31 was much less pronounced. These results indicate that the mobility of protons in these zeolites is lower than that in H-mordenite with SiO 2 /Al 2 O 3 ratio of 106.

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