Phosphorus modification increases catalytic activity and stability of ZSM-5 zeolite on supercritical catalytic cracking of n-dodecane

Supercritical catalytic cracking of hydrocarbon fuel for active thermal protection of aircraft is a promising technique. The catalytic reaction with stable activity is crucial for practical application. Phosphorus-modified ZSM-5 zeolites (ZSM-5-P) were prepared by impregnation and applied in supercritical cracking of n-dodecane to enhance the stability of thermal protection. ZSM-5-P were characterized by XRD, N₂ adsorption-desorption, SEM mapping, NH₃-TPD and pyridine-absorbed FTIR. The acid amount of ZSM-5-P decreased with the increase of phosphorus content. The catalytic performance achieved maximum at phosphorus content of 0.5 wt% (ZSM-5-0.5P). Its gas generation rate (GGR) achieved 64.2%, and heat sink reached 3094 kJ/kg, which was 20.2% higher than that of unmodified catalyst (2576 kJ/kg). The carbon deposition decreased with the increase of phosphorus content. Besides, ZSM-5-0.5P and ZSM-5-1P maintained stable activity (over 50% for GGR) and high heat sinks (3000 kJ/kg) even after reaction for 60 min.