Sl. Lawton et al., ZEOLITE MCM-49 - A 3-DIMENSIONAL MCM-22 ANALOG SYNTHESIZED BY IN-SITUCRYSTALLIZATION, Journal of physical chemistry, 100(9), 1996, pp. 3788-3798
As-synthesized MCM-49 is a three-dimensional (3D) microporous aluminos
ilicate zeolite with the MCM-22 framework topology. It is formed hydro
thermally in a reaction gel and is the first example of a zeolite with
this topology to be produced by direct synthesis, in contrast with th
e conventional procedure in which a precursor is formed first and is t
hen calcined. When hexamethyleneimine (HMI) is used as the directing a
gent, a SiO2/Al2O3 ratio of the framework as low as 17/1 can be achiev
ed. X-ray powder diffraction (XRD), temperature programmed base desorp
tion (TPBD) experiments, and multinuclear NMR analyses of this zeolite
and others in this series (viz., calcined MCM-22 and its precursor) p
rovide new insights into the novelty of this class of materials. TPBD
and C-13 NMR experiments, for example, provide experimental evidence t
hat support the coexistence of different dual pore systems within both
the MCM-22 precursor and MCM-49. The Al-27 MAS NMR spectra of MCM-22
and calcined MCM-49 exhibit three distinct Td resonances, a feature no
t previously observed for any other zeolite. And finally, aluminum enr
ichment of the T1-O1-T1 bridge in MCM-49 is postulated on the basis of
the length of its unit eel c-parameter.