(266d) Hydrothermal Carbonization of Biomass: Examination of Post Synthesis Treatment and Characterization Techniques

Hydrothermal carbonization is a thermal treatment process during which biomass is converted to a carbon-rich, highly aromatic and chemically active solid (hydrochar). The solid produced is useful as a solid fuel, fertilizer, soil amendment, gas storage, and water purification. In this work hydrothermal chars formed from simple sugars have been modified via the addition of acid during synthesis, the addition of acid after synthesis, the addition of nitrogen containing compounds and via ball-milling. The structure of hydrochar was then investigated using Infrared spectroscopy, NMR spectroscopy, elemental analysis and Raman spectroscopy. To date, Raman spectroscopy has been an underutilized technique for hydrochar characterization, despite the sensitivity of the method toward the carbon-carbon bonds that compose hydrochar. The main reason for the underuse of Raman spectroscopy is the lack of a model to interpret hydrochar’s complex, overlapping spectrum. We have determined that the characteristic D and G band of carbonaceous materials is an incorrect interpretation for hydrothermal chars, and is resultant from thermal changes in the material and not from how the material is synthesized. In this work a new method for taking the Raman spectra of hydrothermally treated carbons is demonstrated. We then apply fitting methods derived Density Functional Theory to examine the structure of the molecules, taking a brief look at how the different treatment methods listed above change the furan to arene ratio of the material.