Spatial confinement effects of cage-type SAPO molecular sieves on product distribution and coke formation in methanol-to-olefin reaction

• Propene and butenes were predominantly formed over SAPO-18 and SAPO-34.
• Ethene and propene especially ethene were favored over SAPO-35.
• Coke species greatly depended on the reaction temperature.
• Catalyst deactivation originated from adamantane hydrocarbons at 300 oC.
• Confined aromatics and adamantanes reflected spatial confinement of cage structure.

Three kinds of 8-membered ring silicoaluminophosphate (SAPO) molecular sieves with different cage structures, SAPO-34, SAPO-18 and SAPO-35, were employed in methanol-to-olefin (MTO) reaction. The main products over SAPO-34 and SAPO-18 were propene and butenes, whereas ethene and propene especially ethene were predominantly generated over SAPO-35. Coke species formation greatly depended on reaction temperature and varied systematically with cage size. The differences in production distribution and generated coke species in the MTO reaction suggest great spatial confinement effects imposed by cage structure of SAPO catalysts.

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