Synthesis of mesoporous MOR materials by varying temperature crystallizations and combining ternary organic templates

An approach, which involved perturbations of synthesis conditions in crystallization temperature and organic template composition, has been proposed for derivation of mesopores from bulk structural defects formed in mordenite (MOR) phases, based on the character of intrinsic crystal defects and tensional distortions of two compressed 8-membered rings in MOR framework. Consequently, hierarchically porous materials with MOR structures were prepared by varying temperature synthesis and using ternary organic micelles templates. The synthesized materials were characterized by powder X-ray diffraction, nitrogen adsorption at 77 K and transmission electron microscopy. These crystalline materials combined the advantages of both mordenites with the micropore system and mesoporous materials by featuring an additional intracrystalline mesopore system in MOR single crystals, resulting in a hierarchical pore distribution in range of 1.7–80.0 nm together with the significant specific surface areas. In particular, individual crystal morphologies of typical mesoporous MOR materials showed the defect-rich structures responding essentially to the mesoporosity; the mesoporous materials were substantiated matchable well to normal mordenites in acid capacity and acid strength distribution. Furthermore, several factors acting on intracrystalline mesopore formation were elucidated for explicating the perturbation synthesis approach, and whole reaction routes for synthesizing different solid products under related crystallization conditions were summarized coupling with a demonstration of part TEM micrographs. The overall results suggested that the investigative approach of perturbation imposed on crystal growth provides an alternative route for direct hydrothermal synthesis of mesoporous zeolite materials and implied that bulk structural defects within single crystals lead to the formation of intracrystalline mesopores in various sizes.

TEM micrographs of disordered mesoporous material, two composite materials including MOR subunits or crystallites and the crystalline mesoporous MOR material; the routes of transformation were denoted by direct (green), expectative (blue) and prohibitive (red) arrowheads: (a) noncrystalline disordered mesoporous materials, (b) partially crystalline mesoporous material entity corresponding index electron diffraction pattern, (c) mesoporous material including MOR crystallites and (d) crystalline mesoporous MOR materials with bulky defects.Figure optionsDownload as PowerPoint slideHighlights
► A new approach on perturbation synthesis of mesoporous mordenites was proposed.
► Condition perturbations imposed on crystal growth with bulky structural defects.
► Mesoporous MOR zeolites were prepared by the perturbation synthesis method.
► Significant mesoporosity and zeolitic acid property were demonstrated available.
► Intracrystalline mesopores derived from the bulky structural defects formed.