Selective Adsorption of p‐Cresol from a Mixture of m‐Cresol and p‐Cresol over ZSM‐5 with Controlled Micro‐ and Mesoporosity

Abstract

Ammonium hexafluorosilicate (AHFS) 1 at different concentrations was utilized as a mesopore‐generating agent to synthesize hierarchical ZSM‐5 (Si‐ZSM‐5) adsorbents; K+‐exchanged hierarchical ZSM‐5 (K−Si‐ZSM‐5) was successfully prepared by an impregnation method. The properties of adsorbents were characterized using XRD, XRF, N2 adsorption‐desorption and NH3‐TPD. The selectivity separation of p‐cresol 2 and m‐cresol 3 on adsorbents were experimentally investigated using a liquid breakthrough method. The enhanced adsorption capacity of Si‐ZSM‐5 is attributed to the creation of mesopores, which probably led to higher adsorption diffusion. The introduction of K+ into hierarchical ZSM‐5 diminishes the acid sites, strengthens adsorption sites, and reduces the mesopore diameter. Thus, K−Si‐ZSM‐5 possessed higher separation efficiency compared with the parent HZSM‐5. The concentration of AHFS had significant impact on adsorption capacity and the separation efficiency of adsorbents, and AHFS at a concentration of 0.5 M exhibited the optimal adsorption performance. Furthermore, the adsorbent is easy to prepare under laboratory conditions, and through a large scaled‐up breakthrough experiment, it is suitable for practical industrial applications. Also, we propose separation mechanisms of m‐cresol 3 and p‐cresol 2, and these are mainly controlled by shape selection and adsorbent‐adsorbent interactions.