Synthesis of ZSM-5 aggregates made of zeolite nanocrystals through a simple solvent-free method

Abstract

In the traditional hydrothermal synthesis of zeolites, the solvent of water is necessary for crystallization, so large amount of wastewater containing NaOH and organic pollutants could be inevitably produced. The solvent-free route is considered to remarkably enhance the synthesis efficiency and reduce the energy and pollutants in large scale production of zeolites, but the zeolites obtained usually consist of micrometer sized single crystals which only possess micropores and long diffusion pathway for molecules. In this study, a novel solvent-free synthesis system made of solid raw materials of anhydrous silica and aluminum sources, organic template and Na2CO3·10H2O, was demonstrated to synthesize ZSM-5 zeolite particles composed of nanocrystals of about 10–40 nm in size. The obtained ZSM-5 particles possess high crystallinity and surface area, and well-developed mesoporosity (5.2 nm) and excellent catalytic activity in polymer cracking, such as low-density polyethylene (LDPE), which is the main source of white pollution. The ZSM-5 aggregate particles with the micro-/meso- porous structure have the potential used as catalysts and adsorbents in industry.