Direct CO2 hydrogenation to light olefins over ZnZrOx mixed with hierarchically hollow SAPO-34 with rice husk as green silicon source and template

Abstract

Here, we present a new preparation strategy for hollow SAPO-34 with hierarchical porous structures using rice husk as a sole silicon source and porous template (viz., bio-SAPO-34). The hollow feature and acidity amount of the bio-SAPO-34 were highly dependent on the amount of rice husk in the synthetic solutions. The bio-SAPO-34 exhibited very high olefin selectivity (94.5 %) in the methanol-to-olefins reaction. Bifunctional catalysts consisting of ZnZrOx and bio-SAPO-34 were fabricated for the direct conversion of CO2 to light olefins. The C2=-C4= selectivity of 83 % and C2=-C4= space-time yield of 6.14 mmol gcat−1 h−1 was achieved with only 1 % undesired CH4 at 13.8 % CO2 conversion. Particularly, the CO selectivity from the reverse water-gas shift reaction was suppressed to a low value (40 %). Furthermore, the in-situ DRIFTS result indicates that CH3O* is the key intermediate forming on the ZnZrOx surface and transferring to the Brønsted acid site of bio-SAPO-34 for selective C-C coupling.