Adsorptive desulfurization of liquid fuels is an emerging technology that may allow for the portable generation of electricity using jet fuel-powered fuel cell systems. Pyrolytic remediation of oil-contaminated soils is a thermal treatment that may sustainably detoxify oil-contaminated soils using less energy and preserving soil integrity. This work investigates the underlying mechanisms of these processes through advanced thermo-analytical techniques and mathematical analysis. First, adsorptive desulfurization with CuNa-Y zeolite was studied at temperatures between 30 °C and 180 °C as an approach to remotely remove sulfur present in liquid fuels for fuel cell applications. The amount of sulfur selectively removed from jet fuel and adsorbed onto the Cu sites of the zeolite increased by almost 14x as the temperature was raised from 30 °C or 80 °C to 180 °C. Elevated temperatures promoted the formation of covalent sulfur-metal bonds that displaced other aromatics that do not contain sulfur, which are present at much higher concentrations and compete for adsorption. Operating a flow-through adsorber at 180 °C could effectively reduce the sulfur content in jet fuel to ultra-low levels (1-10 ppmw) over a broad range of liquid hourly space velocities (0.13 to 3.24 h^(-1)). Detailed characterization revealed that desulfurization occurs in two stages. Sulfur is initially removed via adsorption (chemisorption) on the CuNa-Y zeolite, an assertion supported by simulations with a transient heterogeneous model. As the adsorbent becomes saturated, however, surface chemical reactions start taking place leading to the decomposition of benzothiophenes. As a result, the process continues to remove sulfur from the jet fuel feed even after it has exceeded its theoretical adsorption limit. Second, pyrolytic remediation of soils contaminated with heavy hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), was studied at temperatures between 300 °C and 420 °C. Our team developed a novel methodology that combines thermo-analytical measurements and mathematical methods to inform the reliable pyrolytic temperatures for specific soil/contaminant systems. To achieve that, we characterized the complex network of soil and contaminant transformations using thermogravimetry coupled with evolved gas analysis. Additionally, we investigated the contribution of clays during pyrolytic remediation of soils. Clays were found to be the primary component in soil that retains PAHs such as pyrene and therefore sets the remediation intensity requirements. Bentonite modified with Fe(III), Fe-bentonite, performed as a catalyst under pyrolytic conditions, decreasing the temperature at which hydrocarbon decomposition reactions were triggered. The addition of 10%wt Fe-bentonite decreased the residual total petroleum hydrocarbon (TPH) content by 65.9% for treatments at 370 °C and by 79.3% for treatments at 300 °C. Moreover, treatment at 300 °C with the addition of Fe-bentonite resulted in a similar residual TPH when compared to the treatment at 370 °C with no additives. Using such earth-abundant amendments during pyrolytic remediation of oil-contaminated soils could improve energy usage, reduce associated carbon dioxide emissions and lessen unwanted soil transformations.
Overall, this work elucidates the extent and the mechanism of separation and transformation of contaminants like benzothiophenes, heavy hydrocarbons and PAHs at selected temperatures. The findings reported here contribute to the development of efficacious approaches to remove such contaminants from sensitive environments.