Silicalite-1 zeolites for toluene sorption: Effects of the particle size and intracrystalline mesopores

The diffusion limitation of conventional silicalite-1 zeolites was addressed by particle size modulation and intracrystalline mesopore introduction, and the two effects on toluene sorption over silicalite-1 zeolites were systematically investigated. The diffusion rate of toluene increases as the particle size of silicalite-1 zeolites decreases, while the introduction of mesopores into zeolite crystals can further increase the diffusion rate. However, higher diffusion rates of toluene do not always result in better adsorption capacity. The breakthrough time of silicalite-1 zeolites with different particle sizes shows a “volcano” shape. And the breakthrough time decreases after the introduction of intracrystalline mesopores into silicalite-1 zeolites. For toluene adsorption capacity, the microporous structure plays the main role, the mesoporous structure mainly diminishes diffusion limitation and improves the utilization of micropores. The nanosized zeolites with dispersed intracrystalline mesopores exhibit the best dynamic adsorption capacity with the lowest diffusion limitation. The short microporous diffusion path and abundant micropore structure are the vital parameters for silicalite-1 zeolite adsorbents with high performance.