![]() The enhanced catalytic performance of the bifunctional catalyst with hierarchical SAPO-34 could be attributed to the hierarchical structure of SAPO-34 that can increase the rate of mass transfer to avoid further hydrogenation and conversion of olefin products on the catalyst, thus could improve the selectivity of C2–C4 olefins. ![]() Importantly, the bifunctional catalyst with hierarchical SAPO-34 has a good catalytic stability with no obvious deactivation over 100 h of testing. Compared with the bifunctional catalyst obtained from the SAPO-34 molecular sieves without post-treatment, the bifunctional catalyst with hierarchical SAPO-34 obtained by mother liquor post-treatment showed enhanced performance with higher selectivity of light olefins. The obtained hierarchical SAPO-34 were mixed with ZnCrAlOx oxide to prepare the bifunctional catalyst, and the catalytic performance for direct conversion of syngas to light olefins was examined. The physical and chemical properties of the resulting molecular sieves were characterized by XRD, SEM, TEM, N2 adsorption–desorption, XRF and NH3-TPD. In this study, we present a facile post-treatment approach to obtain hierarchical SAPO-34 by treating the crystallized product in mother liquor at low temperature. The designed capsule catalyst has superior potential for scale-up in the industrial application, at the same time extending the horizontal of hybrid catalysts for other tandem catalysis reactions through this strategy.ĭirect synthesis of light olefins from syngas (STO) using bifunctional catalyst composed of oxide and zeolite has attracted extensive attention in both academia and industry. The light olefins space time yield (STY) of the capsule catalyst is beyond twice of that of the typical physical mixture catalyst. Due to the difference between the adsorption energies of Zn-Cr metallic oxide/SAPO zeolite physical mixture and capsule catalysts, the formed water and light olefins are easily removed in the capsule catalyst after formation, suppressing the side reactions. The confinement effect, hierarchical structure and extremely short distance between the two active components realize this capsule catalyst having better mass transfer and diffusion with boosted synergic effect. It can not only break through the limitation of Anderson-Schulz-Flory distribution but also overcome the disadvantages in the physical mixture catalysts such as the plenty of CO2 formation. An elegant catalyst is designed via encapsulation of the metallic oxide Zn-Cr inside of zeolite SAPO34 as a core-shell structure to realize the coupling of methanol-synthesis and methanol-to-olefins reactions.
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