CO2 adsorption reaction mechanism using TEPA/HPS (insitu-IR)

https://doi.org/10.1016/j.jiec.2017.05.018

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In situ infrared (IR) spectroscopy was employed to study the adsorption mechanism over HPS-TEPA-60% adsorbents, as shown in Fig. 9. The nature of adsorbed CO₂ can be revealed by examining relationships among variations of intensities of the NH band at 3298 cm⁻¹, NH₂ at 3365 cm⁻¹, NH₃⁺ at 1639 cm⁻¹, CO at 1685 cm⁻¹ from carbamic acid (NCOOH) and OCO⁻ at 1494 cm⁻¹ from carbamate (NHCOO⁻) during CO₂ adsorption [58]. Upon CO₂ adsorption, the intensity of NH₂ at 3365 cm⁻¹ decreased while the intensities of NHCOO− at 1494 cm⁻¹ and NH₃+ at 3046 cm⁻¹ increased. In contrast, the intensities of NH at 3298 cm⁻¹ and NCOOH at 1685 cm⁻¹ showed a gradual change [59]. The chemically adsorption mechanism can be expressed as follows according to the differences in dynamic behavior of these species.

(3)CO₂ + 2RNH₂ → RNHCOO⁻ + RNH₃⁺

(4)CO₂ + 2R₁R₂NH → R₁NCOO⁻ + R₂NH₂⁺

(5)CO₂ + R₁NH₂ + R₂NH → R₁NH₃⁺ + R₂NCOO⁻

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“Fig. 9. In situ IR absorbance spectra of the HPS-TEPA-60%.”