Determination of Low-Level Biogenic Gasoline, Jet Fuel, and Diesel in Blends Using the Direct Liquid Scintillation Counting Method for 14C Content

The direct liquid scintillation counting (LSC) method was investigated for quantitative measurement of 14C in low-level biogenic gasoline, jet fuel, and diesel range hydrocarbons in fuel blendstock to determine the biogenic content. Carbon-14 (14C) is an ideal tracer for biogenic fuel products, due to the depletion of 14C in fossil-based fuel. Biogenic gasoline, jet fuel, and diesel range hydrocarbons prepared from distillation of hydrotreated pyrolysis oils were blended with toluene at 1-10 wt%. The blends were analyzed by the direct LSC method using both Perkin-Elmer Quantulus and TriCarb instruments, using an internal 14C standard as an indication of signal quench. This study shows that it is feasible to accurately determine the biogenic fraction of blended fuels containing 1 wt% biogenic fuel using the direct LSC method, suggesting that direct LSC could be an option for quality assurance testing of biomass-derived liquids at co-processing facilities. The Quantulus and TriCarb instruments were found to be comparable for low-level detection of 14C in blended samples, suggesting that some instrument flexibility may be available to potential users. Quenching effects were considered and several methods for quench correction were compared.