Interfacial effects between carbon nanotube templates and precursors on fabricating a wall-crystallized hierarchical pore system in zeolite crystals

Abstract

The failure in some direct synthesis of hierarchical zeolite with a hard- or soft-templating method would be caused by the brittle binding forces between the templates and zeolite precursors or frameworks. In present work, high-quality hierarchically porous ZSM-5 with crystalline pore walls is synthesized by using hydroxylated carbon nanotubes (CNTs) as templates. Mesopores structure with a size of about 10–35 nm similar to the diameters of the CNTs template is successfully fabricated in the as-synthesized ZSM-5 zeolite. The structural and textural properties of the as-synthesized samples are revealed by characterization of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, in situ infrared spectroscopy of pyridine, temperature-programmed desorption of ammonia (NH3-TPD), N2 adsorption–desorption, and nuclear magnetic resonance spectroscopy in details. Catalytic cracking of tri-isopropylbenzene is chosen as a probe reaction so as to explore the catalytic performances of the hierarchical zeolite because of its notably increased external surfaces resulted from the created hierarchical pore system. A hierarchically cracking manner of bulky reactants is found over the as-synthesized the meso-zeolite ZSM-5.