The influence of the expanding and exfoliating conditions on the structural transformation of the layered zeolite Nu-6(1)

The conditions for the transformation of the Nu-6(1) zeolite into the low-surface area, narrow pore Nu-6(2) zeolite, as well as into a high surface area material, called ITQ-18, have been investigated by applying XRD, SEM, FTIR, thermoanalysis (TG/DTA) and N-2 adsorption measurements. The creation of a free accessible surface area of zeolite Nu-6(1) by desorption of the interlayer 4,4'-bipyridine molecules occurs already during vacuum treatment at 350 degrees C. As a result zeolite Nu-6(2) is formed. Intermediate expanding and ultrasonic treatment had the effect, that low-ordered materials are formed, which have BET specific surface areas up to about 500 m(2)/g. XRD measurements of this material show weak reflexes of zeolite Nu-6(2) but no long-range ordering. Therefore, the recipe for transformation of precursor Nu-6(1) into a well-structured material (ITQ-18) may lead to materials with high specific surface area but, which not necessarily must have the characteristic long-range ordering of crystalline ITQ-18. (c) 2007 Elsevier Inc. All rights reserved.