(121b) Properties of Activated Carbon from Two Lignin Waste Streams in Lignocellulosic Biorefineries

Creating fuels and chemicals from lignocellulosic biomass offers a promising alternative to fossil fuels for accomplishing carbon neutrality and minimizing greenhouse gas emissions. To economically produce the fuels from biomass, it is essential to convert the “ligno-” components to valuable products. Activated carbon (AC) is a suitable product because it’s market is large enough to consume the amount of lignin separated during the biofuel production and it does not have a stringent requirement for its precursor. Currently, the two main lignin streams from biorefineries are the black liquor produced during alkaline pre-treatment and solids remaining after enzymatic digestion.

In this work, we use the solid contents of the two main lignin streams from biorefineries as precursors to produce AC. These streams are briefly separated and purified to create solid fractions with reduce ash and enriched with lignin. Solid fractions with varying ash (impurities), lignin content, and lignin properties were used as precursors for AC to identify how the precursor properties affect AC properties. The pore structure was analyzed using BET analysis and the aqueous adsorption capacities were characterized by using iodine number and methylene blue value. Using standard ZnCl₂ activation and low-temperature carbonization, we synthesized ACs with surface areas up to 2500 m²/g, which can likely be increased by optimizing the synthesis conditions. Importantly, we found that ash content had a small affect and sugar content had a strong influence on the AC pore properties. Furthermore, the proposed method for synthesizing AC is not complicated and is appropriate for bulk production.