Sodium persulfate promoted interzeolite transformation of USY into SSZ-13 via a solid-state grinding route and its enhanced catalytic lifetime in the methanol-to-olefins reaction

SSZ-13 has been widely used in catalysis and adsorption due to its excellent hydrothermal stability and large specific surface area. It was reported that the long crystallization time was one of the primary challenges limiting its industrial progress. In this paper, we reported a novel solid-state grinding route of synthesizing SSZ-13 zeolite, which was based on interzeolite transformation strategy and promoted by sodium persulfate (Na 2 S 2 O 8 ). The effects of the amount of Na 2 S 2 O 8 and crystallization time on the purity and crystallinity of SSZ-13 zeolite were studied by XRD measurements in detail. The results indicated that the crystallization time could be significantly shortened from 72 to 24 h when the molar ratio of Na 2 S 2 O 8 /SiO 2 was changed from 0 to 0.01, proving that Na 2 S 2 O 8 has the ability of accelerating the crystallization of SSZ-13 as a hydroxyl radical reagent. Three typical SSZ-13 materials and a reference sample were used as the catalysts for methanol-to-olefins reaction (MTO) and their physicochemical properties were analyzed by SEM, N 2 physisorption and NH 3 –TPD techniques. The SEM characterization results showed that the crystal size of SSZ-13 synthesized in the presence of Na 2 S 2 O 8 was larger than that of the one in the absence of it. The NH 3 –TPD results showed that the introduction of Na 2 S 2 O 8 could modulate the acid properties of SSZ-13 zeolites. The MTO tests revealed that the catalytic lifetime of one sample with Na 2 S 2 O 8 promoter (SSZ-13-0.01M-24h) was much longer than that of the other three samples. The observed difference in catalytic stability was mainly attributed to their various concentrations of medium strong acid sites.