Gasolines are constrained to have a minimum level of resistance to oxidation in the liquid phase, based on the ASTM D525 test.  This test exposes the fuel to 690 kPa of O<sub>2</sub> at 100°C and the requirement is that pressure be maintained for at least 240 minutes.  For petroleum-derived gasolines this test primarily limits the content of reactive di-olefins.  This study that examined the stability a broad range of high octane number bio-derived blendstocks when blended into a commercial gasoline blendstock.  Ethanol, n-propanol, i-propanol, i-butanol, diisobutylene, and bioreformate (bio-derived aromatics) all exhibited adequate stability and showed no evidence of oxidation.  Dimethyl furan and methyl furan oxidized extensively and produced high levels of oxidative gum (insoluble polymeric materials), while cyclopentanone oxidized but did not produce gum.  We propose a density functional theory-based analysis of possible reaction pathways for alkyl furans, showing that OH radicals can form by reaction of the alkyl group and that addition of OH radicals to the furan ring is energetically favored and leads to ring opening products.  These products can react with each other or the original alkyl furan to produce observed reaction products and ultimately higher molecular weight gums.  Oxidation of cyclopentanone is shown to require the presence of olefins in the petroleum-derived hydrocarbon blendstock – for example no oxidation occurs for cyclopentanone blended into isooctane, but oxidation does occur in a mixture of cyclopentanone, isooctane, and 1-hexene.  A mechanism for this interaction will be presented.

Oxidation stability of bio-derived gasoline blendstocks: Novel oxidation chemistry for alkyl furans and cyclopentanone

256th National Meeting (2018)

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