One-step direct synthesis of SAPO-36 using 4-pyrrolidinopyridine as an efficient structure-directing agent

• Published in: Microporous and mesoporous materials 2024-02, Vol.366, p.112950, Article 112950
• Main Authors: Liang, Jun, Hu, Wende, Li, Xiangcheng, Liu, Chuang, Chen, Xueli, Wang, Yu, Fu, Wenhua, Yuan, Zhiqing, Wang, Chuanming, Wang, Zhendong, Yang, Weimin
• Format: Article
• Language: English
• Subjects: 4-Pyrrolidinopyridine; ATS; MeAPO-36; Molecular sieves; SAPO-36; Structure-directing agent; Zeolite synthesis
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2023.112950

The synthesis of ATS-type aluminophosphate is challenging due to the formation of AFI-type aluminophosphate as a competitive phase when using traditional tripropylamine (Pr3N) as an organic structure-directing agent (OSDA). SAPO-36, the ATS-type silicoaluminophosphate, is less reported due to the rigorous synthetic conditions. Herein, a novel organic compound, 4-pyrrolidinopyridine (Ppyr), was found to be an effective OSDA for the first time to synthesize SAPO-36 via direct hydrothermal method. Various techniques, including XRD, SEM, TEM, nitrogen sorption, ICP-AES, XPS, TGA, solid NMR, NH3-TPD, and Py-IR, were carried out to characterize the synthesized SAPO-36 samples with different Si contents. It was experimentally and computationally demonstrated that Ppyr was a better OSDA than conventional Pr3N to direct the crystallization of the ATS-type structure. Heteroatom (Mg, Co, Fe, and Zn) isomorphically substituted ATS-type molecular sieve analogues can be successfully synthesized using Ppyr as OSDA. [Display omitted] •Direct hydrothermal synthesis of pure SAPO-36 molecular sieve was realized using 4-pyrrolidinopyridine as OSDA.•Calculated stabilization energy of 4-pyrrolidinopyridine in SAPO-36 is much lower than that of tripropylamine.•In comparison with tripropylamine, 4-pyrrolidinopyridine was better to direct the crystallization of ATS-type structure.•MeAPO-36 (Me = Mg, Co, Fe, Zn) molecular sieves were also synthesized.