The hierarchical ZSM-5 zeolites with interconnected meso-/microporosity have been successfully synthesized by using the commercial organosilane surfactant TPOAC as the mesopore structure-directing agent, and the influence of the TPOAC/SiO 2 ratio in the initial synthesis gel on the crystallinity, hierarchical structure, and acidity of the obtained hierarchical ZSM-5 zeolites were systematically investigated through a combination of XRD, FTIR, SEM, TEM, N 2 adsorption, TGA, ICP, and NH 3 -TPD techniques. The catalytic performance was evaluated by the methanol-to-propylene (MTP) reaction, and the obtained results indicated that the hierarchical ZSM-5 catalysts directed by TPOAC exhibited significant enhancement in the catalytic performance reflected at activity, lifetime, product yield, P/E ratio, and coke toleration by virtue of their superior meso-/micropore interconnectivity and appropriately weakened acidity, comparing with the commercial bulky ZSM-5 and the conventional sole micropore ZSM-5.

Two-dimensional (2D) layered zeolites are new forms of 3D zeolite frameworks. They can be pillared to form more open porous structures with increased access for reactants that are too big for the micropores of zeolites. The current pillaring procedure, however, requires intercalation of pillaring precursors by dispersing 2D zeolite in an alkoxide liquid and hydrolizing entrapped alkoxide to form inorganic oxide pillars in an aqueous alkaline solution. Both steps use excess solvents, generate significant waste, and require multiple synthesis and separation steps. Here we report a vapor-phase pillarization (VPP) process to produce pillared zeolites from 2D layered zeolite structures. The VPP process has ∼100% efficiency of alkoxide usage in the intercalation step, requires less (and, in some cases, zero) water addition in the hydrolysis step, does not require separation for product recovery, and generates no liquid waste. Furthermore, synthesis of pillared zeolites via the VPP process can be accomplished within a single apparatus with one-time operation. The pillared zeolite prepared by the VPP method preserved the zeolitic layered structure as well as acidity and showed enhancement in catalytic alkylation of mesitylene with benzyl alcohol compared to 2D layered zeolite without pillarization treatment.

No abstract

The hierarchical layered-bulky ZSM-5 (LBZ5) hybrid composites with a core−shell structure were synthesized by epitaxial growth of layered ZSM-5 nanosheets over bulky ZSM-5 crystals. The systematic balance of zeolitic microporosity and interlayered mesoporosity was achieved by elaborate regulation of the ratio between layered phase and bulky phase, resulting in a series of layered-bulky ZSM-5 hybrid composites with the controllable thickness of the layered shell ranging from 98 to 307 nm. The evaluation of catalytic performance in the methanol-to-propylene (MTP) reaction indicated the LBZ5 materials to be candidated catalysts for the MTP process with prolonged catalytic lifetime, superior coke toleration, and enhanced propylene selectivity compared with the parent bulky ZSM-5 (BZ5) and layered ZSM-5 (LZ5) due to their well-retained zeolitic framework, hierarchical meso-/microporosity by the layered-bulky composite structure, and appropriate strong acidity.

No abstract