Defense Date


Graduation Date

Fall 1-1-2017


One-year Embargo

Submission Type


Degree Name



Chemistry and Biochemistry

Committee Chair

Bruce D Beaver

Committee Member

Stephanie Wetzel

Committee Member

Michael Van Stipdonk


Diesel, Oxidation, ULSD, SMORS, oxidative stability, thermal stress


Dissertation supervised by Professor Bruce D. Beaver

The oxidative stability of ultra-low sulfur diesel (ULSD) has generally been expected to continuously decline over time. However, recent studies have suggested that it may fluctuate.1-2 In this study, the oxidative stability of stored commercially purchased ULSD was monitored with a methanol extraction method.3 In this methodology, proposed by Hardy and Wechter, fuel blends are extracted with methanol before and after thermal stressing.4 The methanol-soluble layer contains the oxygenated and oxidizable components of the fuel (SMORS) and the change in this mass upon stressing thus represents the oxidative stability of the fuel. Over the course of 145 days of storage under various conditions; this mass difference – called the SMORS mass was observed to recover, decline and recover again.

In a concurrently run study – phenol was generated within two simplified ULSD blends consisting of 25% cumene in heptane after 38 days of lab storage. The amount of phenol peaked between days 62 and 76. Within the same time frame, the oxidative stability of the similarly stored ULSD peaked. This suggests that phenol was also generated within the ULSD and that this in situ generated phenol served to increase the oxidative stability. Infrared spectra of deposits formed during stress runs suggests the formation of quinones. This in turn suggests that the subsequent loss of oxidative stability is due to the conversion of the generated phenols to quinones – which would then undergo coupling reactions, eventually yielding high molecular weight deposits.3