IMPROVEMENT OF HYDROTHERMAL STABILITY OF MCM-41 USING SALT EFFECTS DURING THE CRYSTALLIZATION PROCESS

Low hydrothermal stability in hot water and aqueous solutions was a cr itical problem for many applications of the mesoporous molecular sieve MCM-41, compared with conventional zeolites such as Y and ZSM-5. The hydrothermal stability of MCM-41 has been found to improve remarkably by using various salts such as sodium chloride, potassium chloride, so dium acetate, and ethylenediaminetetraacetic acid tetrasodium salt dur ing the hydrothermal crystallization process performed at 370 K. High- quality MCM-41 samples obtained by using the salt effect indicated neg ligible structural losses as judged by X-ray diffraction during heatin g for 12 h in boiling water.