Synthesis of MCM-41 type materials with remarkable hydrothermal stability from UTM-1

A microporous zeolite UTM-1 was prepared and transferred to MCM-41 type materials by refluxing with surfactant at the presence of NaOH and by a subsequent pH adjusting process. The pH value affected the long-range order of these mesostructures greatly, and MCM-41 type products were obtained at pH = 7 and pH = 5 (designated as MS-7 and MS-5, respectively). The as-synthesized MS-7 showed smaller particle sizes (about 500 nm) and cylindrical pores. MS-7 showed a high BET specific surface area of 1003 m2/g and a high pore volume of 1.20 cm3/g after calcination at 823 K as well as two pore size distributions centred at 2.4 and 3.7 nm, respectively. The calcined MS-7 exhibited remarkable hydrothermal stability. After being treated in boiling water for 312 h, the material remained a high BET specific surface area of 922 m2/g and a high pore volume of 1.08 cm3/g without degrading its well-ordered mesostructure. Compared with MS-7, the 823 K calcined MCM-41 showed poor hydrothermal stability and preserved only a BET specific surface area of 150 m2/g and a pore volume of 0.35 cm3/g upon being treated in boiling water for 24 h. The remarkable hydrothermal stability of MS-7 was ascribed by solid-state NMR results to the presence of higher percentage of 4-fold coordinated Al species and the highly polymerized pore walls.