EFFECT OF CRYSTALLIZATION TEMPERATURE ON STRUCTURAL TRANSFORMATIONS OF MESOPOROUS MOLECULAR-SIEVE M41S MATERIALS

The effect of crystallization temperature on the structural transforma tions of molecular sieve M41S materials was described for the cetyltri methylammonium-silicate system at a low surfacrant/silica ratio and a low surfactant concentration. With increasing crystallization temperat ure to 135 degrees C, the texture of originally formed hexagonal MCM-4 1 is changed. When crystallization temperature increases to 150 degree s C, the thermal stability oi M41S materials is decreased due to the t ransformation of mesoporous structure from hexagonal MCM-41 lattice to thermally unstable lamellar phase. Further increasing crystallization temperature ro or above 165 degrees C, the microporous ZSM-5 type zeo lite instead of mesoporous M41S materials is formed in the same synthe tic system, resulting from the structural transformation of M41S to ZS M-5.