Synthesis of SAPO-34 using metakaolin in the presence of β-cyclodextrin

SAPO-34 molecular sieves were synthesized by the addition of β-cyclodextrin (β-CD) as crystal growth inhibitor using metakaolin as silicon and aluminum sources. Properties of the obtained samples were characterized by XRD, SEM, N2 adsorption–desorption, FTIR, XRF, EDX, NH3-TPD and 29Si MAS NMR. When β-CD was added, crystal size of the SAPO-34 crystals decreased. Variation of Si content from the crystal center to surface decreased while total Si content hardly changed. 29Si MAS NMR results showed that β-CD contributed to better Si dispersion and decreased the size of Si(4Si) patches. Moreover, the MTO (methanol-to-olefin) process was conducted to investigate the influence of β-CD on catalytic performance. The synthesized sample with molar ratio of β-CD/Al2O3 equaling 0.055 remained active for 610 min while the sample synthesized without β-CD for only 280 min, which indicates that the lifetime of catalyst synthesized with β-CD is greatly prolonged.

Graphical abstract SAPO-34 crystals of small particle size and low surface acid site density were synthesized using metakaolin by adding β-cyclodextrin as crystal growth inhibitor, with catalytic performance greatly improved.Figure optionsDownload full-size imageDownload as PowerPoint slide