One-Step Ethylene Purification from a Seven-Component Cracking Gas Mixture with Sorbent-Sorbate Induced-Fit
Xiaowan Peng, Li Zhao, Yun‐Lei Peng, Chenghua Deng, Yassin H. Andaloussi, Huiyuan Pan, Yongjun Tian, Jin‐Sheng Zou, Rajamani Krishna, Bei Liu, Chun Deng, Peng Xiao, Chang‐Yu Sun, Michael J. Zaworotko, Guangjin Chen, Zhenjie Zhang
Abstract
Industrial purification processes for ethylene from steam pyrolysis or cracking gases generally employ multiple energy-intensive steps to remove C<sub>2</sub>H<sub>2</sub>, C<sub>2</sub>H<sub>6</sub>, CO<sub>2</sub>, and C<sub>3</sub> 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 C<sub>2</sub>H<sub>4</sub> from a seven-component cracking gas mixture (C<sub>2</sub>H<sub>4</sub>, C<sub>2</sub>H<sub>2</sub>, C<sub>2</sub>H<sub>6</sub>, CO<sub>2</sub>, C<sub>3</sub>H<sub>4</sub>, C<sub>3</sub>H<sub>6</sub>, and C<sub>3</sub>H<sub>8</sub>) by one-step separation with remarkable performance. Verified by breakthrough experiments, C<sub>2</sub>H<sub>4</sub> (>99.99 can be recovered not only from binary C<sub>2</sub>H<sub>6</sub>/C<sub>2</sub>H<sub>4</sub> (50/50), ternary C<sub>2</sub>H<sub>2</sub>/C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub> (33/33/33), and quaternary C<sub>2</sub>H<sub>2</sub>/C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub>/CO<sub>2</sub> (25/25/25/25) mixtures, but also from a typical seven-component gas cracking mixture of C<sub>2</sub>H<sub>2</sub>/C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub>/CO<sub>2</sub>/C<sub>3</sub>H<sub>4</sub>/C<sub>3</sub>H<sub>6</sub>/C<sub>3</sub>H<sub>8</sub> (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 C<sub>2</sub>H<sub>4</sub> from a seven-component cracking gas mixture and opens an avenue to address complicated hydrocarbon mixture separation challenges.