Measuring the Light Crude Oil (LCO) content in standard biodiesel/LCO blends by thermal analysis

The goal of the present study was to determine the potential use of thermal analysis for the measurement of the light crude oil (LCO) content of standard biodiesel mixtures. Standard samples of biodiesel/LCO blends were prepared with different ratios of biodiesel; LCO: 1:0 (biodiesel only), 1:3, 1:1, 3:1, 0:1 (LCO only). Thermogravimetry (TG) and differential scanning calorimetry were used to determine the usefulness of thermal analysis for quantification of the LCO in the mixtures. Proton nuclear magnetic resonance (^1H NMR) spectroscopy was also used to confirm the composition of the samples. It was found that thermogravimetric curves were not appropriate for the LCO measurements. However, the DSC signal of wax crystallization exhibited a good linear (R² = 0.99) correlation with the LCO content in the blend. Furthermore, it was shown that aliphatic protons (-CH_2-)_n in biodiesel and light crude oil can also be used to determine LCO in biodiesel/LCO blends. (author)