Antioxidants from Wood-derived Pyrolyzates (Bio-oils)

Biodiesel (derived from soybeans) has been produced on a large scale over the past ten years. However, several problems have precluded its general adoption, including poor storage properties due to its susceptibility to peroxidation. The addition of synthetic antioxidants has improved storage stability; however, the use of naturally occurring antioxidants may be preferable due to consumer concerns.

B.K. Sharma, senior research engineer at ISTC, and Richard Larson (Department of Natural Resources and Environmental Science at the University of Illinois at Urbana-Champaign) investigated several natural phenolic compounds with antioxidant activity that were produced by pyrolysis from wood (birch hardwood), corn stover, and lignin. The phenols were isolated from the bio-crude oil by extraction with alkali and their antioxidant activities were determined. Preliminary evidence showed that a diesel/biodiesel mixture responded differently to the naturally derived phenol antioxidants than when they were added to biodiesel alone.

The total phenolic extracts from birch wood pyrolysis and kraft lignin were active antioxidants in all analyses and were comparable in effectiveness to the synthetic antioxidant butylated hydroxytoluene (BHT). However, many simple phenolic monomers were found to have little or no activity when tested with biodiesel (derived from soybeans). Chromatographic separation and analysis of the extracts indicated that the bulk of the activity was associated with a more complex fraction, made up principally of dimers in the size range of lignans, with molecular weights from 272 to 344.

This project was funded by the Hazardous Waste Research Fund (Grant No.: HWR12220). More details on this research are available in the Research Report (RR-129).