Low cost, high throughput analyses that track biocarbon at low percentages (0-10%) for bio-fossil fuel blends and for co-processed feedstocks can be used to optimize refinery process conditions to maximize the biogenic carbon content in transportation fuels. Isotope ratio mass spectrometry (IRMS) can provide δ13C measurements in ~30 minutes and has been shown to provide reproducible biogenic content in fuels and bio-oils. In this work, we determined the variation in δ13C values of fossil fuels blended with 0% to 10% C3 and C4 blendstocks using IRMS to estimate the precent of biogenic carbon in fuels. To this end, a method was developed to combust fuels and capture the resulting CO2 which was then analyzed for δ13C values via dual inlet IRMS. We produced δ13C mixing curves for these fuel blends, where the δ13C of biogenic and fossil endmembers have ranges of 4.94‰ and 15.92‰ for C3 and C4 blendstocks, respectively. 95% confidence intervals were obtained for these mixing curves and provide a measure of precision for estimating the percentage of biogenic carbon in blended and co-processed fuels with different endmember ranges. The CO2 samples used in this work were also analyzed using infrared spectroscopy at Aerodyne Research, Inc. (Billerica, MA) to evaluate an alternative high throughput analytical capability. Initial data indicate good agreement between spectroscopic and spectrometric methods, highlighting the potential of two different analytical techniques for evaluating δ13C of fuels.

Determining percent biocarbon in C3 and C4 fuel blends using δ13C values by isotope ratio mass spectrometry and moving to online analysis

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