SMALL-ANGLE X-RAY-SCATTERING FROM MCM41 AND ITS SYNTHESIS GELS - OPTIMIZATION OF THE SYNTHESIS PARAMETERS

We have found optimised conditions for alkaline synthesis of the large pore molecular sieve, MCM-41, by determining small angle X-ray scatte ring and adsorption isotherms from materials at various stages of the preparation. The presence of highly curved surfaces, sealed structures , and quasicrystalline hexagonal products coexisting with true MCM-41 are all detected by transmission electron microscopy. Calcination must be carried out with care. The product is most crystalline from unstir red preparations which have been heated at 100 degrees C for no longer than three days. Under these conditions, a maximum BET surface area o f 1950 m(2) g(-1) was attained, with evident crystallinity observed by electron diffraction and transmission electron microscopy. In the sti rred system, which appears to be in a nonequilibrium state, materials after calcination exhibiting Bragg d-spacings of 35 Angstrom 37 Angstr om and 38 Angstrom have been identified.