Amine-Functionalized Lignin for CO 2 Capture─Part 2: A Double Amine Grafting Strategy

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Abstract
Global warming has been exacerbated by the escalating emissions of greenhouse gases from fossil fuel power plants and other industrial and transportation sources. Postcombustion CO2 capture by amine-containing materials has evolved into a burgeoning industry for mitigating point-source emissions. Nevertheless, the deployment of sustainable and biodegradable solid-supported amine adsorbents remains underexplored despite their tunable surface chemistry that can be leveraged for CO2 adsorption. Therefore, the purpose of this study is to valorize lignin for CO2 capture using a double amine functionalization method. Lignin was subjected to two separate grafting procedures: one with diethylenetriamine (DETA) to produce DETA-aminated lignin (DAL) and another procedure involving 3-aminopropyltrimethoxysilane (APTMS) and triaminosilane (TRI) to make APTMS- and TRI-grafted lignin. Subsequently, DAL was further grafted by TRI (TRI/DAL) to increase amine content and improve CO2 capture. TRI/DAL was found to achieve a considerably higher CO2 uptake than that of individually modified materials. In the presence of 15% dry CO2/N2 at 25 °C, CO2 uptake reached 1.31 mmol/g, representing a 72% increase compared to DAL (0.76 mmol/g) and more than 250% of TRI/Lignin-1 (0.37 mmol/g). Humidity further promoted CO2 capture, with a CO2 uptake of 1.84 mmol/g and an amine efficiency of 0.43 mol CO2/mol N at 55% relative humidity (RH). In addition to enhancing CO2 uptake, the presence of moisture improved the cyclic stability of the material, with TRI/DAL retaining 97.5 and 95% of its initial capacity after ten cycles at 25 and 50 °C in the presence of 15% CO2/N2 with 55% RH.
Funding Information
  • Natural Sciences and Engineering Research Council of Canada (ALLRP 586596-23, RGPIN-2024-06127)
  • Mitacs (ALLRP 586596-23)

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