Loading...
On the Importance of Surface Chemistry Upon Time-Domain Nuclear Magnetic Resonance Methods
Toledo Suekuni, Murilo
Toledo Suekuni, Murilo
Citations
Altmetric:
Abstract
Classic surface area characterization techniques require sample preparation and testing conditions that may be destructive to certain materials, misleading conclusions about their native properties. Particularly, ex-situ surface area and porosimetry analyses limit the ability to assess the material under relevant practical conditions. Time-domain nuclear magnetic resonance (TD-NMR) or relaxometry is a non-invasive and convenient alternative for studies with fluid-saturated samples. This dissertation used solvent relaxometry experiments to investigate the porosity and solid-fluid chemical affinity in different systems. Besides analytical research work, complementary studies were conducted on the chemical derivatization of polysaccharides.Solvent relaxation rates of polymer particle suspensions elucidated the role of surface chemistry in TD-NMR methods through the solid-fluid affinity parameter, surface relaxivity (ρ2). Polymers with a high heteroatom (O, N) content generally showed higher ρ2 values for water than n-decane. The comparison of ρ2 with water contact angles from the literature yielded an inverse relationship, indicating that TD-NMR can predict polymer wettability. In addition, the equivalence of laboratory-scale relaxometry experiments to well-logging technologies was further explored in studies with isolated kerogens, i.e., the insoluble sedimentary organic matter in shale rocks. First, kerogen samples were extensively characterized via solid-state techniques, resulting in a comprehensive data set of bulk and surface properties. After suspension in water and n-decane, kerogens displayed more complex trends of ρ2 than polymers, indicating mild correlations to its surface composition but strong influence from organic free radicals.Additional research comprised the use of solvent longitudinal and transverse relaxation time distributions to obtain further insights from multiple fluid-saturated porous media. The results elucidated the versatility of TD-NMR in characterizing drying phenomena in nanocellulose slurries, the water mobility in hydrogel networks, and the adsorption energy of liquids on catalyst supports.Ultimately, the findings reported in this dissertation highlight the importance of understanding the surface chemistry role in time-domain NMR experiments and its value to rapidly and accurately characterize different porous materials.
Description
Date
2023-08-31
Journal Title
Journal ISSN
Volume Title
Publisher
University of Kansas
Collections
Research Projects
Organizational Units
Journal Issue
Keywords
Chemical engineering, Kerogen, Polymers, Relaxometry, Solid-Fluid Interactions, Surface Chemistry, TD-NMR