Green-Economic Strategy for the Rapid Synthesis of Nanosized Hollow SAPO-34 Zeolite with Industrial MTO Waste Catalyst

Nanosized or hierarchical SAPO-34 zeolites are of great interest due to their high performance in the methanol-to-olefin (MTO) reaction. However, special structures inevitably involve costly reagents. Herein, we used MTO waste catalysts as the parent materials to rapidly synthesize the nanosized SAPO-34 zeolite with a hollow structure without adding an additional organic directing agent. The abundant zeolite nanocrystalline fragments and secondary building units within waste catalysts shorten the crystallization induction period and reduce the crystal size of SAPO-34. While the subsequent dissolution of the tiny nanocrystalline fragments wrapped in the crystals and extraction of framework atoms during the crystallization cogenerated the hollow structure. The nanosize and hollow structure endow the catalyst with a lifetime of 470 min, much longer than that of the conventional counterpart (150 min). Of note is noteworthy that the hollow structure supplies the large "coke storage tank," which obviously enhances the carbon tolerance capacity of the catalyst. This study gives inspiration to synthesize nanosized hollow zeolites and also provides a green efficient way for the resourceful utilization of waste zeolite catalysts.