(552i) Scalable and Sustainable Synthesis of Nitrogen-Functionalized Porous Carbon from Lignin Waste for CO2 Capture Using a Single-Step Aerosol Method

There is a growing demand to develop environmentally benign materials for capturing CO₂ emissions, which are a leading contributor to climate change [1, 2]. Among different materials for CO₂ capture, porous carbons with nitrogen functional groups have gained special importance due to tunable porosity properties, high selectivity, and excellent cyclability. However, conventional synthesis techniques involve multistep batch processes, require long processing times, and utilize activating agents/templates that are not environmentally benign, limiting their potential for large-scale synthesis [3, 4].

To overcome the challenges of conventional synthesis methods, this study demonstrates the scalable synthesis of nitrogen-functionalized porous carbon nanoparticles through a single-step continuous gas phase aerosol reactor without the use of activating agents or templates. This single-step approach requires a significantly lower time for synthesis: an order of seconds in comparison to hours for conventional methods. Lignin, a renewable and biorefinery waste by-product, and urea are used respectively as precursors for carbon and nitrogen functional groups. The effects of temperature, residence time, and the urea-to-lignin ratio on carbon nanoparticle functional groups, pore size distribution, surface area, and morphology are systematically investigated. Our findings indicate that surface area increases with temperature and residence time in the aerosol reactor. Furthermore, the as-obtained carbon nanoparticles are tested for CO₂ adsorption. The material with a maximum surface area of 1051 m²/g exhibited a CO₂ adsorption capacity of 62 mg/(g of carbon) and excellent cyclability. The effect of in-situ nitrogen functionalization on CO₂ adsorption is currently under investigation.

Overall, the aerosol technique has great potential for advancing the scalable and sustainable synthesis of carbon-based materials for CO₂ capture as it utilizes waste by-product lignin as a carbon precursor, requires no use of activating/templating agents, and offers continuous operation and in-situ nitrogen functionalization.

References:

[1] D.I. Stern, R.K. Kaufmann, Anthropogenic and natural causes of climate change, Clim. Change 122(1) (2014) 257-269.

[2] O. Okonkwo, P. Biswas, Synthesis of Novel Catalysts for Carbon Dioxide Conversion to Products of Value, Catalysis for Clean Energy and Environmental Sustainability, Springer2021, pp. 527-556.

[3] X. Gao, S. Yang, L. Hu, S. Cai, L. Wu, S. Kawi, Carbonaceous materials as adsorbents for CO2 capture: synthesis and modification, Carbon Capture Science & Technology (2022) 100039.

[4] Y. Qiao, C. Wu, Nitrogen enriched biochar used as CO2 adsorbents: a brief review, Carbon Capture Science & Technology 2 (2022) 100018.