Synthesis of mesoporous mordenite zeolite using organosilane surfactant

Abstract

Mesoporous mordenite zeolites were hydrothermally synthesized using amphiphilic organosilane surfactants as mesopore-generating agents by the aid of mordenite seeds. The hydrophobic alkyl tail of the surfactant directed the mesoporous structure while the silica moiety was incorporated in the resultant zeolite frameworks. The resultant mordenite zeolites were characterized by a complementary combination of powder X-ray diffraction (XRD), $N_2$ isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and carbon replication method. The mordenite zeolites exhibited agglomeration of mordenite crystals with nanoneedle morphologies possessing highly uniform mesopores, the size of which could be systematically controlled from 2.6 to 4.3 nm by changing the tail length of the organosilane surfactants. The individual nanoneedle mordenite had a fairly uniform crystal thickness, which progressively decreased from 19 to 11 nm on average as the amount of organosilane surfactant was increased in the synthesis gel. The mesoporous mordenite that consisted of nanononeedle mordenite with a crystal thickness of 11 nm exhibited a high external surface area of $382 m^2g^{-1}$ and a large pore volume of $0.432 ccg^{-1}$. Due to the remarkable increase in external surface area, the mesoporous mordenite showed significantly enhanced catalytic conversion in the alkylation of benzene with benzyl alcohol.