Controllable synthesis of hierarchical beta nanozeolites from tailorable seeds

Abstract

Hierarchical beta nanozeolites were controllably synthesized by tailoring seeds (or protozeolitic units, nanocrystals) grafted with phenylaminopropyltrimethoxysilane (PHAPTMS). The investigation of beta zeolite crystallization reveals that it proceeds through condensed-step mechanism, gradually growing in size along two populations of particles and evolving in internal structure. Based on the zeolitic seeds formation process, there were two roles of organosilane: the more-like mesoporogen agent in short precrystallization time and the growth inhibitor after the formation of secondary particles with significant amounts of terminal silanol groups. It was also found that both the mesopore properties and the crystal size of the prepared hierarchical beta nanozeolites were also strongly dependent on the properties of seeds. Moreover, the mechanisms for the formation of hierarchical beta nanozeolites, including size of the nanoseeds as well as its nature on the final crystal size, pore characteristics, crystallinity, and morphology were proposed and discussed in detail.