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Long-chain α-olefins have a high added value as important raw materials for many highly marketable products. Fishcher–Tropsch synthesis products contain ultrahigh-content α-olefins, which are of great value if the challenging separation of α-olefin/paraffin is achieved through energy-saving ways, for which adsorption separation is an attractive technology. One of the most significant differences between the adsorption separation of long-chain and light hydrocarbons is the steric hindrance of the molecular chain. Herein, we propose a combination of window size, metal node spacing, and bending degree to quantitatively describe the adsorption cavity structure for the separation of long-chain α-olefin/paraffin. The general cavity structural characteristics of microporous materials with good separation performance for long-chain α-olefin/paraffin are revealed. The selective adsorption of liquid C6 and C8 α-olefin/paraffin mixtures on CuBTC (BTC = benzene-1,3,5-tricarboxylate) was studied in detail to reveal the influence of the cavity structure on the adsorption and interaction using a combination of batch adsorption experiments and molecular simulation techniques. CuBTC exhibited 360 and 366 mg/g olefin adsorption capacities for C6 and C8 linear α-olefins, respectively. The adsorption energies were −0.540 and −0.338 eV for C8 linear α-olefin and paraffin, respectively. The contributions of different types of interactions to the overall adsorption energy were quantified to illustrate the adsorption energy difference between α-olefin/paraffin and CuBTC. This work provides a new understanding of the long-chain hydrocarbon adsorption behavior different from ethylene/ethane and propylene/propane, which guides the design of adsorbents for α-olefin/paraffin separation.

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Publication history

Received: 20 July 2022
Revised: 30 September 2022
Accepted: 20 October 2022
Published: 24 November 2022

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© Tsinghua University Press 2022

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Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Nos. 21878169 and 21991102), the National Key Research and Development Program of China (No. 2019YFA0905100), and the Tsinghua University Initiative Scientific Research Program (No. 2018Z05JZY010).

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Email: nanores@tup.tsinghua.edu.cn

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