Crude Oil and Biodiesel Analysis with GC-VUV

Methanol can be identified in biodiesel and crude oil, but for different reasons. During the process of transportation and drilling, methanol is utilized in crude oil to stop the creation of gas hydrates.

To make biodiesel, methanol is a reagent for transesterification of vegetable oils, recycled greases, or animal fats, creating fatty acid methyl esters (FAMEs).

If residual methanol is found in either biodiesel or crude oil, it can result in expensive issues, for example affecting the refinery water treatment facilities or failing regulatory limits prior to the blending of fuel.

Standards like the EN 14110 and ASTM D7059 are employed to track the levels of methanol in biodiesel and crude oil, respectively.

Conventional techniques like ASTM D7059 entails a gas chromatograph being directly injected with crude oil.

A backflush capability is required to correctly analyze methanol with a flame ionization detector (FID), which can be challenging. EN 14110 utilizes static headspace GC-FID to identify the amount of methanol in biodiesel.

EN 14110 and ASTM D7059 require that the quantification limits of methanol are between 0.01% to 0.50% (m/m) and 5 to 1,000 ppm respectively.

Crude Oil and Biodiesel Analysis with GC-VUV

Figure 1. Shows a biodiesel headspace chromatogram with .050% (m/m) methanol.  The plot on the right shows the absorbance spectrum of methanol, which is distinct from water and oxygen.Image Credit: VUV Analytics

In Figure 1, methanol is seen to be baseline resolved in crude oil and biodiesel by using static headspace GC-VUV (vacuum ultraviolet spectroscopy).

Crude Oil and Biodiesel Analysis with GC-VUV

Figure 2. Absorbance spectrum of methanol. Image Credit: VUV Analytics

Biodiesel has a much lower presence of volatile compounds compared to the crude oil matrix. Figure 2 presents the absorbance spectrum of methanol, which is unique to any other compounds found in crude oil or biodiesel.

Crude Oil and Biodiesel Analysis with GC-VUV

Figure 3. Calibration curves for Biodiesel and Crude Oil Image Credit: VUV Analytics

Figure 3 shows the calibration curves produced in line with the limits of quantification described in ASTM D7059 and EN 14110. GC-VUV can adhere to these specifications with detection limits of 0.005% methanol in biodiesel and 1 ppm for methanol in crude oil.

Static headspace GC-VUV is utilized to quantify methanol in biodiesel and crude oil as an alternative to using two different sampling methods.  

This process simplifies the GC configuration and protects the GC inlet and column from contamination by biodiesel or crude oil. Quantification of methanol and spectral identification is provided for both matrices.

Static headspace GC-VUV could be a viable alternative to conventional techniques like EN 14110 and ASTM D7059 that quantify methanol in fuel matrices.

Acknowledgments

  • Produced from materials originally authored by James Diekmann from VUV Analytics.

This information has been sourced, reviewed and adapted from materials provided by VUV Analytics.

For more information on this source, please visit VUV Analytics.

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