SAPO-34/AlMCM-41, as a hierarchical nanocomposite molecular sieve was prepared by sequential
hydrothermal and dry-gel methods studied for catalytic conversion of methanol to light olefins. Pure
AlMCM-41, SAPO-34, and their physical mixture were also produced and catalytically compared.
Physicochemical properties of materials were mainly investigated using XRD, N2 isothermal adsorptiondesorption, FESEM, FT-IR, NH3-TPD, and TG/DTG/DTA techniques. Micro-meso hierarchy of prepared
composite could be demonstrated by XRD and BET analyses. Catalytic performance of materials illustrated
that the methanol conversion on the prepared composite was about 98% for 120 min which showed a higher
activity than the other catalysts. The initial reaction selectivity to light olefins for the composite was also
comparable with those for the other catalysts. Furthermore, the results revealed that SAPO-34/AlMCM-41
preparation decreased the concentration and strength of active acid sites of the catalyst which could
beneficially affect the deposition of heavy molecular products on the catalyst. However, as observed, the
prepared composite was deactivated in olefins production faster than pure SAPO-34. The small mean pore
diameter of composite could be mainly responsible for its pore blockage and higher deactivation rate.
Meanwhile, since the SAPO-34 prepared by dry-gel method had inherently high mesoporosity, the
AlMCM-41 introduction didn't promote the molecular diffusion in the composite structure. The coke
content was found 15.5% for deactivated composite smaller than that for the SAPO-34 catalyst which could
be due to the pore blockage and deactivation of the composite in a shorter period.
Keywords: SAPO-34/AlMCM-41 nanocomposite, heterogeneous catalysis, hierarchical structure, characterization,
methanol to olefins (MTO), reaction time
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