Synthesis and characterization of nanoscale aluminosilicate mesoporous materials by microwave irradiation

Abstract

A series of nanoscale alkaline-free aluminosilicate mesoporous molecular sieves were prepared by microwave hydrothermal techniques for 5 to 120 minutes. These nanoscale nanoporous materials own high surface area (600≈1000 m2/g), pore volume (1.0≈2.0 m3/g), narrow pore size distribution and nano-particle size between 20 and 100 nm and four-coordinated aluminum site in major, which were characterized by XRD, N2 adsorption/desorption, TEM, SEM, ICP, 27Al solid-state NMR and cumene cracking reation. Microwave irradiation temperature and time play an important role on their properties of products. These nanoscale aluminosilicate mesoporous catalysts exhibited much higher cumene cracking activity than those prepared by hydrothermal method. The 31P MAS NMR of adsorbed trimethylphosphine oxides (TMPO) observed by Liu et al. revealed the existence of strong Bronsted acid sites at 83 ppm, which is comparable to TMPO adsorbed in conventional zeolites or dissolved in concentrated HCl or H2SO4.