Rational design of P-La modified ZSM-5 from perspectives on interactions among La P and ZSM-5

P-La modification has been industrially demonstrated as a successful approach to enhance the hydrothermal stability of ZSM-5 zeolites. ZSM-5 is widely used as the catalytic component in processes such as fluid catalytic cracking (FCC) and methanol-to-propylene (MTP), which involve harsh reaction/regeneration conditions. With the P-La modified ZSM-5 as the research subject, the interactions among phosphorus, lanthanum, and ZSM-5 during modification and their influence on catalytic performance were systematically investigated through characterization methods including XRD, 27 Al, 29 Si, 31 P MAS NMR, and 2D 31 P{ 27 Al} D-HMQC MAS NMR. The mechanism on enhancement of hydrothermal stability of ZSM-5 zeolite through interactions among P, La and ZSM-5 was proposed. Specifically, during the modification, phosphorus and lanthanum tends to form LaPO 4 and lanxthanum polyphosphate species. This P-La interaction not only suppresses channel blocking and damage in ZSM-5 caused by lanthanum, but also significantly reduces the degree of phosphorus polymerization, facilitating the re-dispersion of phosphorus during hydrothermal treatment and ultimately strengthening the interaction between phosphorus and ZSM-5. Directed by the mechanism, the P-La modified approach was optimized, and the subsequent impregnation of P and La onto ZSM-5 strategy was developed to further improve the hydrothermal stability of ZSM-5.