Exploring Opportunities for Ionic Liquid Capillary Columns in Petroleum Analysis

• Author / Creator

  Weber, Brandon M

• Petroleum samples consist of hundreds to thousands of components and require well-designed experiments to accurately determine quality and composition. The challenges with petroleum samples in this thesis are three-fold, focusing on: alkyl phosphate contamination, group-type composition, and biodiesel content. Alkyl phosphates in petroleum samples are of great interest to refineries that process oil produced from the Western Canadian Sedimentary Basin or other water-sensitive geologies. This interest is due to the presence of residual phosphates from oil-based fracturing fluids causing premature fouling of equipment and poisoning of catalysts, leading to frequent maintenance outages. Group-type composition is of particular importance due to the correlation with emission and performance properties for fuel. ASTM D5186 has previously been used for this purpose, and relies on supercritical fluid chromatography. Unfortunately, this instrumentation is difficult to access and is not able to perform adequate separations on samples containing biodiesel. Our third challenge is one facing industry and consumers who operate in cold climates. Government regulations frequently mandate that industry use biodiesel in their operations to lessen the reliance on fossil fuels and decrease emissions of carbon dioxide [ ]. Therefore, closer regulation of biodiesel is possible with accurate determination of biodiesel content. Ionic liquid capillary columns for gas chromatography provide great potential for a number of applications, due to their unique and tunable properties. They provide complex retention mechanisms that depend on multiple types of intermolecular forces, leading to unique retention properties. This thesis explores the application of ionic liquid capillary columns to these separations challenges. Retention behaviours of alkyl phosphates were studied on a number of ionic liquid gas chromatography columns. The selectivity for alkyl phosphates on ionic liquid columns were compared with selectivity on a 5% phenyl column to evaluate the potential of ionic liquids for separation of alkyl phosphates in petroleum samples. Most interestingly, separation temperature was shown to affect the elution order of a homologous series. Thermodynamic modeling was then used to predict the retention times for a series of alkyl phosphates in first- and second-dimensions. Ionic liquid columns perform best in the primary dimension for alkyl phosphates. Unknown phosphate retention coordinates were also predicted, based on the thermodynamic parameters determined by a set of standard alkyl phosphates. However, retention times of alkyl phosphates on some ionic liquid columns were unstable, due to suspected reactions between the column and analyte. Ionic liquid columns were then compared for their ability to perform a diesel-range group-type separation providing relative abundances of saturates, mono-, di-, and polyaromatics by gas chromatography. The SLBIL-111 column provides the best resolution for the group-types of interest based on 10 model compounds. Selective detection via vacuum ultraviolet detection (VUV) was necessary for determination of saturates and monoaromatics. The optimized gas chromatography method coupled to a VUV to measure group-type composition of 10 oil sand-derived Synfuel light diesel samples, three Syncrude light gas oils, and one quality control sample. The Synfuel results using both the conventional supercritical fluid chromatography method and the new VUV method had good agreement, with an absolute error of 0.8%. The quality control sample also performed well when comparing both methods (absolute % error of 0.2) and the results agreed within error for saturate, mono- and polyaromatics. Lastly, percent biodiesel content in diesel samples was determined using the method optimized for group-type separation. This is necessary as both biodiesel content and group-type composition results need to be collected simultaneously. Using the VUV method it was possible to determine the % biodiesel content with 0.9% error, while still maintaining our original group-type results within an error of 0.6%. Overall, this work presents a significant step towards a method for identifying alkyl phosphates in petroleum samples. While also presenting a few of the possible challenges in using ionic liquid columns for some compounds (such as phosphates). In addition, this thesis presents a viable new method for replacement of ASTM D5186, while adding in the ability to also determine biodiesel content. This will be important to companies across North America where government regulations require specific aromatic content, as well as regulated biodiesel percentages.

• Subjects / Keywords

  • Vacuum ultraviolet detector
  • Petroleum
  • Ionic liquid capillary columns
  • Gas chromatography

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3M32NM62

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.