Catalytic conversion of castor oil to bio-based benzene, toluene, and xylenes using an H-ZSM-5/Al2O3 catalyst

Catalytic conversion of castor oil to bio-based benzene, toluene, and xylenes (bio-BTX) was studied in a continuous-flow fixed-bed reactor with an H-ZSM-5/Al₂O₃ catalyst. The goal was to optimize BTX yield, understand catalyst deactivation mechanisms, and evaluate regenerability. A correlation between temperature and BTX yield was identified, with a peak BTX yield of 28.1 ± 2.4 wt% at 650 °C and a total BTX production of 1428.2 mg g −1 catalyst over an 8-h catalyst lifetime. The fresh, used, and regenerated catalysts were characterized by N 2 and Ar physisorption, NH 3 -TPD, Py-IR, XRD, MAS ssNMR, TEM-EDX, TGA, and elemental analysis. Catalyst characterizations revealed a dual deactivation mechanism: reversible deactivation caused by coke deposition and irreversible deactivation resulting from dealumination of the zeolite framework. Although the used catalyst was regenerated through oxidative coke removal at 680 °C, it could not restore the framework integrity or recover the acidity lost due to dealumination. As a result, the regenerated catalyst only retained about 18% of its original acidity, leading to a 50% decrease in BTX yield. This study highlights the crucial balance between activity and stability, emphasizing the importance of developing hydrothermally stable catalysts for sustainable bio-BTX production from non-edible vegetable oils.