Caterpillar-shaped hierarchical ZSM-5 resulted from the self-assembly of regularly nano-sized primary ZSM-5 zeolite crystals

Abstract

Abstract Hierarchical ZSM-5 with a caterpillar-shaped morphology is hydrothermally synthesized, and characterized by XRD, SEM, TEM, N2 adsorption-desorption, and NH3-TPD. The synthetic parameters influence on the formation of the caterpillar-shaped hierarchical ZSM-5 are investigated and discussed in details. The results suggest that nano-sized ZSM-5 zeolite crystals is yielded from an appropriate precursor and then forms the caterpillar-shaped hierarchical ZSM-5 by in-situ self-assembly of the primary nanocrystals. SEM and TEM images display that the primary crystals in the caterpillar-shaped zeolite samples formed by self-assembly along b-axis of MFI zeolite have a size of about 100 nm. Catalytic cracking of triisopropylbenzene (TIPB) is selected as a probe reaction so as to investigate the catalytic performances of the as-synthesized caterpillar-shaped hierarchical ZSM-5 zeolite. The results show that the as-synthesized hierarchical ZSM-5 zeolite with the increased external surfaces exhibits an elevated catalytic activity during the catalytic cracking of TIPB, and the corresponding traditional ZSM-5 zeolite displays very little activity because of the small external surfaces. The results also shows that for the hierarchical ZSM-5-40-5.32-2.1, due to the high external surfaces and the interpenetrated hierarchical pore system, a multi-stage cracking process for the reaction TIPB molecule is detected. That may offer a potential highly effective catalyst for the catalytic cracking of bulky reactant molecule.