(406e) Carbon Dioxide Capture on Superactivated Hydrochars Derived from Loblolly Pine and Functionalized By Deep Eutectic Solvents

The rising emission of CO₂ primarily from the global combustion of fossil fuel have contributed to global warming in an alarming level. In fact, 70% of CO₂ emission is attributed to different forms of energy generation in various industrial processes like cement production, oil refinery, power plant processes etc. The increased emission of CO₂ has urged the global community to work towards CO₂ capture and utilization which could reduce greenhouse gas emission and mitigate the climate change associated with CO₂ pollution. Although various efforts have been undertaken to capture CO₂ in metal-organic frameworks (MOFs) due to their favorable surface morphology, it is not economically feasible to store bulk amounts of CO₂ in MOFs as that could be cost intensive. Hence, our research focused on producing superactivated hydrochar materials from abundantly available biomass to capture CO₂. Loblolly pine, a woody biomass prolific in U.S, could be a very low-cost feedstock to synthesize such CO₂ storage material. On the other hand, Deep Eutectic Solvents (DES) have been considered as promising green solvents to improve CO₂ capture efficiency by improving surface functionality, henceforth reducing CO₂ capture cost. Thus, the objective of this study was to produce superactivated hydrochars from loblolly pine that were further functionalized with nitrogen-containing groups by using choline chloride-urea, methyl triphenyl phosphonium bromide-glycerine, and tetra alkyl ammonium chloride- ethylene glycol in order to develop materials that can effectively store CO₂. Hydrochar from loblolly pine was produced at 260 °C and activated using KOH at 800°C using KOH: Hydrochar mass ratio of 4:1. The superactivated hydrochars were then ultrasonicated with each DES in the mass ratio of 1:2 (superactivated hydrochar: DES) for 4 hours. Fourier Transform Infrared (FTIR) spectroscopy was used to identify the developed surface functional groups and ultimate analysis was carried out to correlate with nitrogen content (due to functionalization) in the superactivated hydrochars. BET surface area analysis was conducted of the superactivated hydrochars to determine the surface morphology parameters (specific surface area, pore type, pore volume). In addition, High-Pressure Volumetric Analyzer (HPVA) was used to measure the volumetric uptake of CO₂ at 25°C and up to pressure of 5 bar. Analyses showed that the CO₂ storage capacity of superactivated hydrochars were driven by the synergistic effect of both surface morphology and functionality. The materials developed the maximum of BET surface area of around 2800 m²/g and total pore volume 1.8 cm³/g. The CO₂ storage capacity of the developed materials was substantially high, owing to high surface area and nitrogen containing functional groups. Henceforth, a correlation between surface morphology (specific surface area, pore type, pore volume) and surface functionality (nitrogen containing groups) with CO₂ storage capacity was also derived through this study.