Catalysis Over Pore-Expanded MCM-41 Mesoporous Materials

Pore-expanded MCM-41 (PE-MCM-41) silica was obtained via a two-step strategy consisting of synthesis of MCM-41 in the presence of cetyltrimethylammonium cations (CTMA(+)) followed by hydrothermal treatment in the presence of an aqueous suspension of dimethyldecylamine (DMDA). It is believed that the two surfactants self-organize into concentric cylinders comprised of an inverted DMDA micelle within a regular CTMA(+) micelle. The amine head groups point towards the pore center, thus creating a hydrophilic channel within the pores. Selective extraction of DMDA afforded PE-MCM-41E, a highly porous material with hydrophobic surface. Calcination of as-synthesized PE-MCM-41 or PE-MCM-41E gave rise to PE-MCM-41C which exhibits a unique combination of large pores (up to 20 nm), large pore volume (up to 3.5 cm(3)/g) and large surface area, often exceeding 1000 m(2)/g. All three mesophases were used as starting materials for the development of innovative catalysts and adsorbents. Moreover, post-synthesis alumination of PE-MCM-41 and PE-MCM-41C led to novel large pore aluminosilicates with different Si/Al ratios, which provided new opportunities in acid and bifunctional catalysis. This contribution is an overview of the catalytic applications of pore-expanded mesoporous silica and aluminosilica.