Myristyl sulfobetaine-assisted synthesis of SAPO-34 molecular sieves with improved methanol-to-olefins (MTO) performance

Abstract

The SAPO-34 molecular sieves were synthesized via a hydrothermal method using tetraethylammonium hydroxide and triethylamine as dual templates, with myristyl sulfobetaine (SB3-14) as a crystal growth inhibitor. The synthesized samples were systematically characterized by XRD, SEM, ICP, N₂ adsorption–desorption, NH₃-TPD, pyridine-adsorption IR, and FT-IR techniques to analyze their composition, acidity, and structural properties. Results demonstrated that increasing the molar ratio of SB3-14 to Al₂O₃ from 0.01 to 0.04 caused significant variations in morphology, chemical composition, and acidic characteristics of the samples. When the molar ratio of SB3-14 to Al₂O₃ was 0.02, the synthesized sample NS-0.02 exhibited the smallest crystal size, the largest specific surface area, and moderately reduced acidity. The catalytic performance was evaluated in the MTO reaction. The NS-0.02 sample exhibited superior catalytic performance with 94.5% selectivity to light olefins and a catalytic lifetime of 600 min.