Synthesis, Characterization, and Catalytic Properties of a Microporous/Mesoporous Material, MMM-1

Abstract

A microporous–mesoporous material composed of MCM-41 and MFI was produced by a two-step synthetic process. The solid, called “MMM-1,” was characterized by X-ray diffraction (XRD), N 2 physisorption, and transmission electron microscopy (TEM). At early stages of crystallization at 170°C, MCM-41 was formed exclusively, while at heating times longer than 96h MFI was formed. At intermediate times, MMM-1 was formed with varying amounts of MFI depending on the crystallization time. XRD revealed that the material could be severely oriented by sample preparation, which was consistent with an unusual ribbon-like morphology observed in TEM. This morphology was not seen for either pure MCM-41 or MFI. The N 2 physisorption isotherm for MMM-1 showed two distinct regions of capillary condensation, with H2 hysteresis. Synthesis and subsequent use of Al-MMM-1 in the isomerization of m-xylene and comparison to Al-MCM-41 and Al-MFI showed that although the latter material had a higher total conversion, Al-MMM-1 had a higher selectivity for p-xylene. Al-MMM-1 had a much higher selectivity and conversion than Al-MCM-41, which makes it promising for use in future catalytic applications.