Comparative studies of Zr-based MCM-41 and MCM-48 mesoporous molecular sieves: Synthesis and physicochemical properties

摘要: Abstract Two surfactant-templated synthetic routes are developed for the preparation of new types mesoporous molecular sieves, Zr-MCM-41 and Zr-MCM-48, using different Si sources but keeping same zirconium precursor (zirconium- n -propoxide). When fumed silica was used as precursor, a Zr-MCM-48 material cubic structure formed with surface area 654.8 m 2 /g an unimodal pore diameter distribution. It shows low stability: after calcination at 600 °C, ordered transformed into relatively disordered worm-like mesostructure many defects silanol groups. The use tetraethyl orthosilicate source led to formation solid, which had good thermal stability highly hexagonal arrangement, 677.9 m uniform Fourier transform infrared (FT-IR) characterization 29 NMR analysis confirm that ions indeed incorporated framework solid. in situ FT-IR spectroscopy pyridine adsorption reveals both, Lewis Bronsted acid sites, were on these materials. strength number sites solid greater than those Zr-MCM-41, due lower degree condensation reaction during synthesis more structural groups stretching from surface.