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Industrial purification processes for ethylene from steam pyrolysis or cracking gases generally employ multiple energy-intensive steps to remove C2H2, C2H6, CO2, and C3 hydrocarbons. Designing multifunctional molecular separators that integrate multiple structural characteristics capable of removing several impurities simultaneously is highly desired but not yet realized. Here, we address this challenge using a custom-designed multifunctional, and industry-compatible ultramicroporous crystalline physisorbent (CALF-20) to purify C2H4 from a seven-component cracking gas mixture (C2H4, C2H2, C2H6, CO2, C3H4, C3H6, and C3H8) by one-step separation with remarkable performance. Verified by breakthrough experiments, C2H4 (>99.99 can be recovered not only from binary C2H6/C2H4 (50/50), ternary C2H2/C2H4/C2H6 (33/33/33), and quaternary C2H2/C2H4/C2H6/CO2 (25/25/25/25) mixtures, but also from a typical seven-component gas cracking mixture of C2H2/C2H4/C2H6/CO2/C3H4/C3H6/C3H8 (0.6/62/10/0.3/0.6/26/0.5), even at the high humidity of 74 CALF-20 can be easily produced on the kilogram scale, showing great commercial application potential. Together with its framework flexibility and appropriate pore geometry, CALF-20 exhibits a sorbent-sorbate induced-fit behavior strengthening multiple specific recognition sites for the corresponding guests, validated by single-crystal X-ray diffraction study and molecular modeling. This work is the first example of using a single physisorbent to purify C2H4 from a seven-component cracking gas mixture and opens an avenue to address complicated hydrocarbon mixture separation challenges.
Peng et al. (Thu,) studied this question.