Synthesis of Small-Sized SAPO-34 Crystals with Varying Template Combinations for the Conversion of Methanol to Olefins

• Main Authors: Yanjun Zhang, Zhibo Ren, Yinuo Wang, Yinjie Deng, Jianwei Li
• Format: Article
• Language: English
• Published: MDPI AG 2018-11-01
• Series: Catalysts
• Subjects: SAPO-34; mixed template; silicon to aluminum ratio; methanol to olefins
• Online Access: https://www.mdpi.com/2073-4344/8/12/570

SAPO-34 molecular sieves were synthesized under hydrothermal conditions using different combinations of tetraethyl ammonium hydroxide (TEAOH)/morpholine (Mor)/triethylamine (TEA) as templates, with different silicon:aluminum ratios. The physicochemical properties of the synthesized SAPO-34 were characterized using XRD, SEM, N₂ adsorption⁻desorption, XRF, TG, NH₃-TPD, FT-IR, and ²⁹Si MAS NMR analyses. According to the SEM and the N₂ adsorption⁻desorption of the catalysts produced by the ternary template exhibited a larger surface area and a smaller crystal size than those produced by the single or binary templates. The FT-IR analysis indicated the increased acidity of the catalyst prepared by the ternary template. A high activity and selectivity to olefins (C₂⁼ + C₃⁼) and an optimal silicon to aluminum ratio of 0.4 were obtained from the catalyst synthesized with the ternary template. At the reaction temperature of 450 °C, the methanol conversion approached 100% and the ethylene⁻propylene selectivity and the lifetime of the catalyst reached maximums of 89.15% and 690 min, respectively.