With increasing pressures for the adoption of renewable transportation fuels there is a need for refiners and regulators to be able to track renewable/fossil content. To date this has been accomplished using methods identified in ASTM D6866, however, additional progress needs to be made to enable the rapid turnarounds, accuracy, and precision at low blending or co-processing levels, i.e., less-than 10% biogenic carbon, to minimize losses of biogenic carbon during the refining process. In this work, we present results comparing bulk δ13C analysis of fuel blendstocks using isotope ratio mass spectrometry (IRMS) with measurements made on fractions of each fuel blendstock. Fractions were obtained using chemical separations to segregate saturates and aromatics and by boiling point ranges. Using δ13C to assess biogenic carbon content requires knowledge of the biogenic and fossil feedstock in order to define the isotope range covered by the analysis. This is particularly important for fuel samples containing biogenic carbon from C3 sources because the δ13C values overlap considerably with those from fossil sources, and conceivably could be very small (e.g., &lt; 5‰ between fossil and C3 end members). Analysis of fuel components by chemical class or by boiling point may allow a greater range of isotope values than might be obtained by measuring the whole sample, thereby improving the accuracy of the IRMS measurement. Herein we present the results of our ongoing work.

Using separation-enhanced isotope ratio mass spectrometry to enable increased renewable carbon content in transportation fuels

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