Date of Graduation
Davis College of Agriculture, Natural Resources and Design
Forest Resource Management
Benjamin E Dawson-Andoh
One of the greatest challenges in the world today is to replace exhaustible fossil fuel resources with renewable alternatives that will satisfy the increasing worldwide energy and chemical demands in a sustainable way. Using renewable precursors has a low impact on environmental health since it reduces pollution, greenhouse gas emissions and limits global warming and problems associated with waste management. Lignocellulosic biomass is the most available feedstock for developing sustainable chemicals and energy. A major challenge to the efficiency of the forest biorefinery industry is lack of suitable technologies for the conversion of its waste or by-products (lignin and hemicelluloses) into value-added products. In this research, lignin was hydrothermally treated at different temperatures, and the resulting carbonaceous materials (CMs) were functionalized with amine groups to capture carbon dioxide (CO2).;Experimental measurements and characterization techniques were used to evaluate optimum temperature for the hydrothermal treatment of lignin. The yield of CMs decreased with increasing temperature. Thermal degradation analysis showed that at 350°C, a more carbonaceous material was formed, which showed more coal-like features. This was further supported by Raman spectroscopy and X-ray diffraction analysis. Scanning electron micrographs of the CMs also showed both open and closed vesicles after hydrothermal carbonization.;The chemical transformations occurring during hydrothermal carbonization of lignin was investigated. Overall, major structural changes in the HP-L TM lignin only occurred after 300oC. Fourier transform infrared (FTIR) analysis and X-ray photoelectron spectroscopy (XPS) analysis showed that bands due to lignin functionalities disappeared at 350°C. Deconvolution and peak analysis using nuclear magnetic resonance (NMR) revealed the evolution of a more condensed structure characterized by aromatic C when temperature reached 350°C. Lignin remained relatively unchanged up until 350°C where significant aromatization occurs. Based on the above characterizations, a mechanism for HTC was suggested.;Activated samples were functionalized with polyethylenimine (PEI) at different loadings to evaluate their synergistic effect in capturing CO 2. Activation improved to surface area from 2.8 m2/g to 1341 m2/g. The highest CO2 uptake (2 mmolg-1) was attained by samples loaded with 5% PEI after which sorption capacity decreased with increasing PEI loadings. This was ascribed to blockage of the micropores in the activated samples during PEI impregnation. Also, activated samples showed faster adsorption kinetics compared with PEI functionalized activated samples.;Lastly, the hydrothermal treatment (HTT) or carbonization (HTC) of three commercial types of lignin to carbonaceous materials was also investigated. SEM analysis showed that hydrothermally derived carbonaceous materials from Mascoma lignin contained spherical particles with diameters ranging from 50 to 250 nm whereas that from ammonium and sodium ligno-sulfonate lignins contained similar particles but were highly agglomerated. The better characteristics of the post- HTC Mascoma carbon vis-a-vis post-HTC ammonium and sodium carbons are also evident in the results obtained from XRD, TGA and FTIR analysis. It is possible to produce carbonaceous materials from low-value commercial lignins via HTC and their properties are influenced by the type of lignin.
Atta-Obeng, Emmanuel, "Carbon Dioxide Capture Using Amine Functionalized Carbonaceous Materials from Bio-Refinery Waste Streams" (2017). Graduate Theses, Dissertations, and Problem Reports. 5129.