ABS 007: The Role Of Neuroinflammation In The Pharmacodynamics Of Antiepileptic Drugs And How This Interaction Affects Seizure Control

Wyatt F. Brooks ¹, Huyen Nguyen ³, Scott R. Cleary ¹, Runeem M. Al-Abssi ¹, Wenda Hu ², Vannessa Caballero ², Caleb C. Curran-Velasco ¹, Yong Wang ², C. Michael McGuirk ¹

¹ Department of Chemistry, Colorado School of Mines, Golden, CO
² Pacific Northwest National Laboratory, Richland, WA
³ Department of Chemistry, Brown University, Providence, RI

The Van Wickle Journal (2026) Volume 2, ABS007

Introduction: Closed-loop chemical recycling is a promising strategy to address the global plastic waste crisis, yet efficient depolymerization of polyolefins, which comprise over half of all plastics, remains challenging. Conventional approaches often require harsh conditions, noble-metal catalysts, or generate complex product mixtures better suited for low-value fuels. Superacidic sulfated zirconia (SZrO) offers a promising heterogeneous alternative because it can activate hydrocarbons under comparatively mild conditions, with prior reports demonstrating polyolefin decomposition near 200 °C at ambient pressure. However, the catalytic performance of SZrO depends strongly on its active-site structure, surface acidity, crystallographic phase, and synthesis history.

Despite decades of study, the synthetic requirements for producing highly active SZrO remain unclear. In particular, the roles of hydrolysis, zirconium precursor concentration, reflux temperature, pH, base addition, and calcination/hydration conditions are often underreported or inconsistently controlled. These variables influence whether zirconia crystallizes into the desired tetragonal phase, which is associated with higher surface area and greater acid-site density than monoclinic zirconia. Poor control over crystallization therefore limits reproducibility and prevents systematic understanding of SZrO structure–activity relationships.

In this work, we refine the synthesis of sulfated zirconia to promote tetragonal phase formation and improve understanding of how synthetic conditions govern crystallization, phase purity, crystallite size, surface area, and Brønsted/Lewis acid-site density. Powder X-ray diffraction was used to evaluate phase evolution, while pyridine-based spectroscopic analysis informed changes in acid-site character across synthetic conditions. By connecting synthesis parameters to structural and acid-site outcomes, this study establishes an optimized platform for investigating SZrO active-site chemistry and its application in efficient polyolefin depolymerization.

Methods: Sulfated zirconia samples were synthesized through controlled hydrolysis of zirconium oxychloride precursors followed by precipitation, sulfation, calcination, and hydration. Synthetic variables, including base addition rate, pH, reflux temperature, zirconium precursor concentration, and calcination conditions, were systematically adjusted to evaluate their influence on zirconia crystallization and phase purity. Optimized conditions used NH4OH addition to promote controlled hydrolysis and growth, followed by filtration and washing to remove residual ions before sulfate incorporation. Samples were then calcined to generate sulfated zirconia and hydrated to regenerate surface acid sites. Powder X-ray diffraction was used to determine phase composition, monitor tetragonal versus monoclinic zirconia formation, and estimate crystallite size. Pyridine-based infrared spectroscopy was used to evaluate the relative density and distribution of Brønsted and Lewis acid sites. Surface area and microscopy measurements were used to compare morphology and textural properties across synthetic conditions.

Results: We demonstrated that controlled hydrolysis and optimized zirconium precursor concentration promote crystallization of tetragonal sulfated zirconia over the less active monoclinic phase. Increasing reflux temperature and tuning ZrOCl2 concentration improved crystallite size control and phase purity, while rapid or poorly controlled base addition reduced crystallinity and reproducibility. We further showed that synthesis conditions influence surface area and the relative abundance of Brønsted and Lewis acid sites, as measured by pyridine spectroscopy. Overall, optimized synthesis produced smaller, higher-surface-area tetragonal SZrO with stronger acid-site density, providing a more reliable platform for polyolefin depolymerization studies.

Discussion: These findings show that sulfated zirconia activity can be improved by treating synthesis as a controllable crystallization process rather than a fixed preparation method. By linking hydrolysis, phase formation, surface area, and acid-site density, this work helps clarify why SZrO performance has been difficult to reproduce across studies. Establishing reliable access to tetragonal, high-surface-area SZrO creates a stronger foundation for studying active-site structure and hydrocarbon activation mechanisms. Future work should connect these structural and acidity trends directly to polyolefin depolymerization performance, product selectivity, catalyst stability, and resistance to deactivation under realistic recycling conditions.