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Green NCU-20 for C₃H₆/C₃H₈ Sieving
Summary:
The authors from Nanchang University, Arizona State University, and Fujian Normal University developed an isomeric CALF-20 adsorbent (NCU-20) with tailored pore size, green scalability, and high stability, achieving excellent propylene/propane (C₃H₆/C₃H₈) molecular sieving performance.
Background:
1. C₃H₆ purification via C₃H₆/C₃H₈ separation is industrially critical, but their similar properties and the need for low-cost, high-performance adsorbents pose challenges. Previous CALF-20 synthesis relied on organic solvents, leading to high costs and environmental risks, while existing sieving adsorbents lack balanced capacity and selectivity.
2. The authors proposed a hydrothermal method using water as the sole solvent to synthesize NCU-20, achieving contracted pore size, high C₃H₆ uptake, and low production cost.
Research Content:
1. Synthesis
The authors synthesized NCU-20 via hydrothermal reactions: small-scale synthesis used 3Zn(OH)₂·2ZnCO₃, oxalic acid, 1H-1,2,4-triazole (Tz), and water at 180 °C for 2 days (85.7% yield); large-scale synthesis scaled up reagents and water, reacting at 180 °C for 3 days (78.3% yield).
2. Characterizations
1) BET specific surface area: 384 m² g⁻¹ (CO₂ at 195 K) and 321 m² g⁻¹ (N₂ at 77 K); total pore volume: 0.24 cm³ g⁻¹; pore size centered at ~5.0 Å, with contracted channel aperture (4.2 × 4.7 Ų).
2) Crystal size: small-scale (~174 nm), large-scale (~239 nm); block-shaped colorless single crystals with P2₁/n space group.
3) Thermal stability up to 600 K; chemical stability in air, water, boiling water, pH 2–12 solutions, and organic solvents; PXRD confirmed phase purity and structural integrity.
3. Application
- Static adsorption: 94.41 cm³ cm⁻³ C₃H₆ uptake (298 K, 1.0 bar), 22.2 C₃H₆/C₃H₈ uptake ratio (0.5 bar), negligible C₃H₈ adsorption.
- Dynamic breakthrough: 65.39 cm³ cm⁻³ high-purity C₃H₆ (>99.5%) productivity from equimolar mixture; stable performance over 5 cycles and at elevated temperatures (up to 353 K).
4. Mechanism
- DFT calculations showed C₃H₆ diffusion energy barrier (21.8 kJ mol⁻¹) is much lower than C₃H₈ (99.1 kJ mol⁻¹), enabling size exclusion.
- C₃H₈ is excluded by NCU’s 4.2 × 4.7 Ų pores (between C₃H₆’s 4.16 × 4.65 Ų and C₃H₈’s 4.20 × 4.80 Ų).
- C₃H₆ adsorbs via C-H···O and C-H···N interactions at two sites, with zigzag chain packing enhancing capacity.
Outlook:
This research innovates green, scalable synthesis of NCU-20, achieving record C₃H₆ uptake and balanced sieving performance. It addresses industrial separation needs with low cost ($10 kg⁻¹) and high stability, promising wide industrial application.
Green and Scalable Preparation of an Isomeric CALF‐20 Adsorbent with Tailored Pore Size for Molecular Sieving of Propylene from Propane
Authors: Zhenning Deng, Longsheng Yang, Hanting Xiong, Junhui Liu, Xing Liu, Zhenyu Zhou, Shixia Chen, Yanan Wang, Hao Wang, Jingwen Chen, Shuguang Deng, Banglin Chen, Jun Wang
DOI: 10.1002/smtd.202400838
Link: https://onlinelibrary.wiley.com/doi/10.1002/smtd.202400838
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