CO2 Adsorption using Mg-MOF-74/Activated Biochar Composites Produced from the Pyrolysis of Lignocellulosic Biomass

Author

Conner Brosdan PopeFollow

Orcid ID

https://orcid.org/0000-0003-3717-4461

Date of Award

5-2022

Degree Type

Thesis

Degree Name

Master of Science

Major

Biosystems Engineering

Major Professor

Nour Abdoulmoumine

Committee Members

Nicole Labbe, Nour Abdoulmoumine, Julie Carrier

Abstract

Adsorption is a promising carbon capture and storage (CCS) technology with porous solids like activated biochar (AB), graphene oxides (GO), and metal-organic frameworks (MOF) exhibiting different advantages related to separating carbon dioxide (CO₂) from gas mixtures. Accordingly, the synthesis of MOF/GO composites demonstrates synergism between CO₂ adsorption-driving physicochemical characteristics of MOFs and GOs. However, the synthesis of MOF/AB composites has not been explored in the literature to date even though AB shares many physical and chemical similarities with GO. This research project aimed to synthesize MOF/AB composites with appropriate physicochemical characteristics and CO₂ adsorption capacities for adsorbing CO₂ from flue gas and other important industrial gas mixtures using AB derived from lignocellulosic biomass. Biochars were created by pyrolyzing hybrid poplar, loblolly pine, and switchgrass through intermediate pyrolysis at 500°C and used to adsorb CO₂ from a nitrogen gas (N₂) and CO₂ gas mixture. ABs were developed by activating loblolly pine biochar using potassium hydroxide (KOH) through KOH activation at 800°C and used to adsorb CO₂ from a N₂ and CO₂ gas mixture. MOF/AB composites were synthesized by growing magnesium-metal-organic framework-74 (Mg-MOF-74) crystals on loblolly pine AB through solvothermal synthesis at 125°C and used to adsorb CO₂ from a N₂ and CO₂ gas mixture. All biochars had low CO₂ adsorption capacities ranging from 0.17-0.18 mmol/g which was associated with biochars having low specific surface areas, total pore volumes, and alkalinities. Loblolly pine AB had an increased CO₂ adsorption capacity of 0.51 mmol/g compared to 0.18 mmol/g for loblolly pine biochar which was assumed to be connected to loblolly pine AB having a higher specific surface area, total pore volume, and alkalinity and lower average pore width than those of loblolly pine biochar. Mg-MOF-74/loblolly pine AB composites had a higher CO₂ adsorption capacity of 0.59 mmol/g relative to 0.51 mmol/g for loblolly pine AB which was assumed to correspond to Mg-MOF-74/loblolly pine AB composites having a higher amount of micropores than that of loblolly pine AB. Future work will investigate different MOF synthesis methodologies and surface functionalization of MOF/AB composites to improve CO₂ adsorption.

Recommended Citation

Pope, Conner Brosdan, "CO2 Adsorption using Mg-MOF-74/Activated Biochar Composites Produced from the Pyrolysis of Lignocellulosic Biomass. " Master's Thesis, University of Tennessee, 2022.
https://trace.tennessee.edu/utk_gradthes/6409