La/SAPO-11 was synthesized via one-pot method. Lanthanum ions protect framework from distortion under the severe thermal (600 °C, 4 h) and hydrothermal (800 °C, 4 h) conditions. A higher retention of Brønsted acid sites (45.5%) is obtained after hydrothermal treatment. Lanthanum ions enhance the depolymerization of phosphorus species and interaction with phosphorus and aluminum species. In the coexistence of silicon and lanthanum ions, lanthanum ions could not incorporate into zeolite framework. LaPO4preserves framework structure from steam attack. In addition, [La(OH)2]+ions compensate structure tensions and increase the bond strength of Al–O inhibiting the desilication reaction during the thermal treatment. The hydrolyzed species of Si (4Al) and Si (3Al) can be recovered by dehydroxylation. In the cracking reaction of n-dodecane, La/SAPO-11 molecular sieve possessing moderate acid sites enhance isomerization reaction (increasing iso-paraffin by 9.5%) and inhibit cracking. The narrow pore has restriction for di-molecular reactions (e.g., hydrogen transfer reaction).
- Lanthanum ion
ASJC Scopus subject areas
- Physical and Theoretical Chemistry