(569ff) Understanding the Fate of Sulfur in Hydrothermal Liquefaction of Sewage Sludge

With the development of hydrothermal liquefaction (HTL) of sewage sludge, desulfurization will inevitably play a role in the mix of activities associated with the upgrade of biocrude to a transportation fuel. Increasing studies show high levels of sulfur content in the biocrude produced from various feedstock. Furthermore, the sulfur compound constituents originating from sewage sludge, an inexpensive feedstock from which renewable transportation fuels can be extracted, vary significantly from one wastewater treatment plant to another, and research on the chemistry and mechanisms involved is scarce, considering existing research has focused on using model feedstocks. Thus, shedding light to understand the fate of sulfur in hydrothermal liquefaction of sewage sludge is necessary.

Hydrodesulfurization (HDS) has long been used in crude oil refineries as the primary method for sulfur removal. Other desulfurization methods such as Oxidative Desulfurization (ODS) and Adsorptive Desulfurization (ADS) have been explored, but their application has been limited as none proves economically viable at commercial scales. In this study, we will characterize the biocrude produced from HTL and a radical initiated hydrothermal liquefaction process (RI-HTL) using Gas Chromatography with Sulfur Chemiluminescence Detection (GC-SCD), Gas Chromatography Pulsed Flame Photometric Detection (GC-PFPD) and X-Ray Fluorescence (XRF) Spectroscopy. Early results show that sulfur in these biocrudes is distributed among many compounds, likely primarily sulfides and similar, since benzothiophenes and dibenzothiophenes cannot have as many isomers as sulfides due to constraint on structure. Based on this realization, our attention has been focused on HDS-HTL and high temperature ADS-HTL, yielding promising results.