Efficient synthesis of high silica SSZ-13 zeolite via a steam-assisted crystallization process
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High silica SSZ-13 zeolite was synthesized by an efficient and green steam-assisted crystallization (SAC) method under a low alkalinity and low organic templates amount system. The as-prepared samples were characterized by XRD, SEM, N2 adsorption–desorption, TG–DTG and NH3-TPD. The results showed that the SAC method can not only remarkably improve zeolite yield but also enhance the crystallization rate of SSZ-13 zeolite compare to conventional hydrothermal route. Meanwhile, it was also found that the various content of the organic structure directing agent (N,N,N-trimethyladamantammonium hydroxide, TMAdaOH) in the dry gel can adjust flexibly the crystal size, morphology and acidity of samples. The zeolite samples with smaller particles and more strong acidity amount were more likely obtained under the higher TMAdaOH/SiO2 ratio (0.2) condition. In addition, the catalytic evaluation in methanol-to-olefins (MTO) reaction showed that the high silica SSZ-13 catalysts synthesized by SAC method exhibited longer lifetime and comparative selectivity to ethylene and propene than those of the SSZ-13s obtained by conventional hydrothermal route. Thus, the SAC route is believed to be a competitive strategy to synthesize high silica SSZ-13 zeolites with improved MTO catalytic performance.
KeywordsSSZ-13 CHA zeolite Steam-assisted crystallization High SiO2/Al2O3 ratios MTO reaction
The authors gratefully acknowledge the financial supports of the National Natural Science Foundation of China (No. 51371123), the Natural Science Foundation of Shanxi Province (No. 201701D121024), and Shanxi Scholarship Council of China (No. 2017-042).
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