Seed-assisted grinding synthesis of SAPO-34 catalyst and its prolonged catalytic lifetime in the conversion of methanol to olefins
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A cost-effective route has been developed for the synthesis of nano-sized triclinic SAPO-34 zeolite via seed-assisted grinding method using lower dosage of morpholine as the sole template. The synthesis conditions including silica source, silica concentration, crystallization temperature and time were refined to obtain SAPO-34 zeolite with high phase purity and crystallinity. Particularly, seed crystals preactivated by different methods were utilized to induce the synthesis of nano-sized SAPO-34 zeolites in the subsequent study. The resultant SAPO-34 samples were characterized by XRD, SEM, N2 physisorption and NH3-TPD techniques. It was found that the introduction of seed crystals activated by mechanical milling for 20 min and chemical etching with 0.0001 M and 0.01 M H3PO4 can not only effectively reduce the crystal size of SAPO-34 zeolites from 3–4 μm to 500–800 nm level, but also can modify their texture and acid properties. This nano-sized SAPO-34 catalyst exhibits a remarkably prolonged catalytic lifetime in methanol to olefins (MTO) reaction in comparison to the conventional micron-sized counterpart. Analogous to solvent-free synthesis of zeolites, this seed-assisted grinding synthesis method is simpler, more efficient than conventional hydrothermal synthesis. More importantly, this method provides a new avenue for preparing superior MTO catalyst.
KeywordsZeolite synthesis Activated seeds Triclinic SAPO-34 Methanol to olefins reaction
This work was supported by the National Natural Science Foundation of China (Grant No. 21666019) and the Natural Science Foundation of Gansu Province, China (Grant No. 17JR5RA124). We cordially thank the Reviewers and Editors for providing us with valuable comments and suggestions.
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