Synthesis of hierarchically porous zeolite A crystals with uniform particle size in a droplet microreactor

Abstract

Simple and fast synthesis of zeolite A nanocrystals with uniform particle size and bimodal mesoporous-microporous distribution is presented. It takes only tens of minutes to synthesize rather than hours to days that are usually needed. A microfluidic system is devised and used for the hydrothermal synthesis, in which monodispersed nanolitre droplets containing a gel type precursor solution are generated in a lab-on-a-chip part of the system and then passed through a capillary tube part at 100 °C. A water-soluble alginate polymer was introduced into the gel to generate a hierarchically mesoporous-microporous zeolite A crystals with around 100 nm particle size and high crystallinity, which showed a superior catalytic performance in alkyl borate synthesis. The approach presented here could open a new avenue for producing high quality inorganic nanoparticles continuously with no clogging problem that is inherent in the synthesis of nanoparticles.