Benchmarking selective capture of trace CO₂ from C₂H₂ using an amine-functionalized adsorbent

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Purifying acetylene (C2H2) requires efficient removal of trace carbon dioxide (CO2).
• The similar physical properties of CO2 and C2H2 present a significant challenge for selective separation.
• Existing adsorbents struggle to achieve high selectivity and capacity for CO2 removal in C2H2 streams.

Purpose of the Study:

• To develop a highly selective adsorbent for capturing trace CO2 from C2H2.
• To investigate the adsorption performance and mechanism of a novel PEI@HP20 adsorbent.
• To demonstrate the scalability and efficiency of the PEI@HP20 adsorbent for industrial acetylene purification.

Main Methods:

• Loading polyethyleneimine (PEI) onto a commercial resin adsorbent (HP20) to create PEI@HP20.
• Characterization using multinuclear solid-state Nuclear Magnetic Resonance (NMR) and Fourier Transform infrared spectroscopy (FTIR).
• Computational analysis using density functional theory (DFT) calculations.
• Pilot-scale pressure-temperature swing adsorption (PSA) experiments.

Main Results:

• PEI@HP20 exhibits a high CO2 adsorption capacity of 4.35 mmol/g at 100 kPa and 298 K.
• Achieved a record CO2/C2H2 uptake ratio and an ideal adsorbed solution theory (IAST) selectivity of 1.33×10^7.
• Pilot-scale PSA demonstrated >99.99% purity C2H2 with a yield of 344.7 g/cycle from CO2/C2H2 (1/99, v/v) mixtures.
• The adsorbent's performance is attributed to a dual chemisorption/physisorption mechanism.

Conclusions:

• PEI@HP20 is a highly efficient and selective adsorbent for CO2 capture from C2H2.
• The dual mechanism of PEI@HP20 contributes to its superior performance.
• This work presents a promising, scalable method for developing green, cost-effective CO2-selective adsorbents for acetylene purification.