The effect of oxidation on the distribution of alkylphenols in crude oils

Alkylphenols in crude oils can be affected by oxidation during storage. A crude oil and an alkylphenol mixture were exposed to light and air for various time periods, resulting in significant alterations of the alkylphenol distributions. Most affected were ortho/para substituted isomers, such as 2,4-/2,6-dimethylphenol and 2,4,6-trimethylphenol, whereas phenol, and meta substituted isomers such as m-cresol and 3,5-dimethylphenol were least affected. The alkylphenol distributions in two crude oils from the same accumulation, one of which was stored for 34 years, were found to be different in a manner consistent with a scenario where the stored oil had been affected by oxidation. These results suggest that the alkylphenol distributions in crude oils can be severely altered by oxidation which is enhanced by exposure to light. Therefore, if precautions are not taken to minimise the effects of oxidation during sampling and storage, alkylphenol distributions may be altered. Significant oxidation can be avoided by storing samples in opaque containers such as metal tins and drums and reducing or flushing air from the containerʹs headspace.