A research team led by Prof. Pan Xiulian and Prof. Bao Xinhe of the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) discovered dynamic confinement of SAPO-17 cages on the selectivity control of syngas conversion.
This study was published in National Scientific Review on July 26.
In 2016, the team proposed a new catalyst concept based on metal oxide-zeolite bifunctional catalysts (OXZEO), which enabled the direct conversion of syngas into light olefins with high selectivity.
In this study, the researchers reported the dynamic confinement effect of zeotype cages, which controlled product selectivity during the induction period of syngas conversion. They gradually increased the ethylene selectivity from 19% to 44%, while C. fell4+ hydrocarbon selectivity of 39% to 9% within the first 22 hours of operation. After the induction period, the catalytic performance leveled off.
“This was caused by the gradual accumulation of carbonaceous species in the SAPO-17 cages as the reaction progressed. It led to a gradually reduced free space in the cage,” said Prof. Bao.
They found that the diffusion coefficient ratio of C2 to C4 was negatively correlated with an effective space coefficient (ESC), a descriptor defined to describe the effective space in the SAPO-17 cage. It indicated more hindered diffusion for C4 then for C2 with the reduced free space of the cage. In addition, a limited free space would also hinder the secondary reaction of ethylene and thus be beneficial for C2 selectivity.
“This study reveals a significant effect of SAPO-17 cage dynamic confinement on product selectivity,” said Prof. Pan. Although most micropores were occupied (93%) when the induction period was completed, the catalyst was not deactivated and ran quite stably in the syngas conversion.
This dynamic confinement is expected to be common to a number of reactions involving hydrocarbons over zeolites. The understanding is essential for the further design of high performance zeolite catalysts for C1 chemistry and other reactions involving hydrocarbons.
Direct synthesis of isoparaffin-rich gasoline from syngas
Haodi Wang et al, Dynamic confinement of SAPO-17 cage on the selectivity control of syngas conversion, National Scientific Review (2022). DOI: 10.1093/nsr/nwac146
Provided by the Chinese Academy of Sciences
Quote: Dynamic Confinement of SAPO-17 Cages on Syngas Conversion Selectivity Control (2022, Sept. 7) Retrieved Sept. 7, 2022 from https://phys.org/news/2022-09-dynamic-confinement-sapo-cages-syngas.html
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