(117r) Predictions of Hydrochar Properties Using Molecular Structure Determined By Solid State NMR

Hydrothermal carbonization (HTC) is a process where wet biomass is converted to a solid hydrothermal char by a chemical process under moderate temperature and autogenous pressure. Hydrochar can be used for a variety of environmental applications including water treatment, soil amendments, combusted as a solid bio-fuel, etc. A major challenge in the field is development of structure-property relationships that can be used to select an optimal application for a hydrochar based on its structure. A major step forward in the development of structure-property relationships is the finding of a molecularly detailed structure by collaborators at Brandeis University, based on solid state Nuclear Magnetic Resonance Spectroscopy (NMR) data. Solid state NMR provides molecularly detailed insight into hydrochar structure; however, NMR analysis is a time consuming, expensive, and complicated process that is not always practical. To determine similar information via simpler methods, predictions from the NMR were compared with other characterization methods such as Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, Boehm Titration, and zeta potential measurements. A peak fitting process was used to quantify functional groups based on FT-IR bands which was compared to functional groups quantified in the NMR model structure. Density Functional Theory (DFT) analysis based on the NMR model structure was used to simulate its hypothetical Raman spectrum, which was then compared to an experimental Raman spectrum for glucose hydrochar. Acid surface sites measured experimentally through Boehm Titration were compared to those quantified in the NMR model structure. Finally, a predictive mathematical model was developed based on the NMR model structure data to determine if macroscopic hydrochar properties, like zeta potential, could be predicted based on surface characteristics. Experimental data and other characterization methods displayed good agreement with the NMR model structure, providing both confidence in the model structure and the use of simpler techniques to determine hydrochar properties. The results of this study are an important step in the design of hydrochars.