The effect of ZSM-5 zeolite crystal size on p-xylene selectivity in toluene disproportionation

Albahar, M; Li, C; Zholobenko, V; Garforth, AA

Abstract

The effect of crystal size was explored in this work aiming at enhancing p-xylene selectivity through toluene disproportionation over ZSM-5 zeolite. The different physicochemical properties of ZSM-5 were investigated using various characterization techniques including X-ray diffraction (XRD), pyridine adsorption, Fourier transform infra-red (FTIR), BET surface area by N2 adsorption, inductively coupled plasma (ICP) and scanning electron microscopy (SEM). Each catalyst was tested in a fixed bed reactor at a temperature 475 °C, weight hourly space velocity (WHSV) 3-83 h-1 and two different pressures (1 and 10 bar). ZSM-5 zeolites with crystal sizes 5, 50 and 100 µm were synthesized in house and compared with the commercially obtained ZSM-5 having a crystal size of 0.5 µm. As a result of increasing the crystal size the p-xylene selectivity was improved. This was attributed to the longer diffusion path lengths of the large crystals which imposed more diffusion constraints on the other xylene isomers. ZSM-5 zeolite with the largest crystal size 100 µm achieved the highest p-xylene selectivity (58%) at the highest WHSV 83 h-1. However, this was accompanied by a low conversion (2 wt %). The best combination of p-xylene selectivity (40%) alongside 15 wt % toluene conversion were achieved over ZSM-5 having 5 µm crystal size.

Citation

Albahar, M., Li, C., Zholobenko, V., & Garforth, A. (2020). The effect of ZSM-5 zeolite crystal size on p-xylene selectivity in toluene disproportionation. Microporous and Mesoporous Materials, https://doi.org/10.1016/j.micromeso.2020.110221

• Acceptance Date: Mar 30, 2020
• Publication Date: Apr 8, 2020
• Journal: Microporous and Mesoporous Materials
• Print ISSN: 1387-1811
• Publisher: Elsevier
• DOI: https://doi.org/10.1016/j.micromeso.2020.110221
• Keywords: ZSM-5 zeolite; Toluene; Disproportionation; Selectivity; Para-xylene
• Publisher URL: https://doi.org/10.1016/j.micromeso.2020.110221