Artigo Revisado por pares

Characterization and hydroisomerization performance of SAPO-11 molecular sieves synthesized in different media

2007; Elsevier BV; Volume: 332; Issue: 1 Linguagem: Inglês

10.1016/j.apcata.2007.07.047

ISSN

1873-3875

Autores

Shengzhen Zhang, Sheng‐Li Chen, Peng Dong, Guimei Yuan, Keqi Xu,

Tópico(s)

Mesoporous Materials and Catalysis

Resumo

Abstract Silicoaluminophosphates SAPO-11 molecular sieves were synthesized from a conventional aqueous medium, a two-liquid phase medium and a HF medium, respectively, and were characterized by various methods such as XRD, SEM, pyridine-FT-IR, NH 3 -TPD, 29 Si MAS-NMR. The morphologies of the SAPO-11 molecular sieves obtained from the conventional aqueous medium and the two liquid-phase media exhibit pseudo-spherical aggregates ranging from 7 to 10 μm assembled from cubic plate microcrystallites, whereas the SAPO-11 molecular sieves synthesized from the HF medium exhibit hexagonal prismatic aggregates of about 1–3 μm length. The synthesis media used highly influenced the number and the strength of SAPO-11 acid sites. Compared to SAPO-11 obtained from conventional aqueous medium, SAPO-11 prepared from two-liquid phase media possessed a similar number of BrOnsted acid sites but a much larger number of Lewis acid sites, whereas the SAPO-11 synthesized from HF medium had a similar number of Lewis acid sites but a much lower number of BrOnsted acid sites. The 29 Si MAS-NMR spectra showed that the HF could change the manner of Si incorporation into the SAPO-11 framework. The hydroisomerization of n -hexadecane on Pt/SAPO-11 samples showed that Pt/SAPO-11 obtained from the two-liquid phase media had the largest yield of isomers. The conversion activity of n- hexadecane was dependent on the amount of BrOnsted acid of SAPO-11 molecular sieves, while its hydrocracking activity was related to the strong acid sites of SAPO-11.

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