Physical Chemistry

Bulletin of the Academy of Sciences of the USSR, Division of chemical science

, Volume 31, Issue 7, pp 1300-1305

Structural changes in mordenite during its dealuminization

  • G. K. BeierAffiliated withInstitute of Physical Chemistry, Academy of Sciences of the USSRCentral Scientific-Research Institute for Chemistry, Hungarian Academy of Sciences
  • , I. M. Belen'kayaAffiliated withInstitute of Physical Chemistry, Academy of Sciences of the USSRCentral Scientific-Research Institute for Chemistry, Hungarian Academy of Sciences
  • , M. M. DubininAffiliated withInstitute of Physical Chemistry, Academy of Sciences of the USSRCentral Scientific-Research Institute for Chemistry, Hungarian Academy of Sciences
  • , F. KhangeAffiliated withInstitute of Physical Chemistry, Academy of Sciences of the USSRCentral Scientific-Research Institute for Chemistry, Hungarian Academy of Sciences

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Conclusions

  1. 1.

    Treatment with acids leads to the dealuminization of mordenite, condensation of pairs of hydroxyl groups in alternate hydroxyl clusters carrying five-membered rings over to four-membered rings. Dehydroxylation proceeds in such way that two OH groups are first eliminated from each of the hydroxyl clusters, without any loss of crystallinity. Loss of crystallinity is observed only on eliminating the second pair of OH groups from the cluster.

     
  2. 2.

    Hydrothermal treatment of the acid-dealuminized mordenite gives a product with enhanced structural stability. This effect results from the healing of vacancies induced by dealuminization, and from an increase in anion skeleton Si/Al ratio arising from Si and O atom migration, the situation here being similar to that met in the hydrothermal stabilization of H-zeolite.

     
  3. 3.

    The data suggest that the aluminum atoms which leave the H-mordenite lattice during dehydroxylation do not pass over into the cation state.