Denitrogenation of Thermally Cracked Naphtha

• Author / Creator

  Rao, Yuan

• Three main areas were investigated: characterization of the thermally cracked naphtha, development of novel denitrogenation reactions to remove basic nitrogen compounds from the naphtha, and fundamental study of chemistry that removes neutral nitrogen compounds from model oil. Identification and quantification of nitrogen-containing compounds in thermally cracked naphtha was the first to be investigated, to understand the nature of the nitrogen compounds, in order to strategically plan the development of denitrogenation methods. A base pretreatment method using nickel (II) carbonate, along with silica column chromatography was conducted to remove the complex matrix of the naphtha, and extract nitrogen compounds for qualitative and quantitative analysis. Gas chromatography coupled with mass spectrometry (GC-MS) was used to identify nitrogen compounds. Quantification was conducted with gas chromatography coupled with both flame ionization detector (FID) and nitrogen phosphorus detector (NPD). Measurements of NPD response to different classes of nitrogen compounds were performed, thus the results have revealed that the response would be structure dependent. A non-hydrotreating denitrogenation reaction with bromoacetic acid, through N-alkylation, was developed to selectively remove basic nitrogen containing compounds from the thermally cracked naphtha. In addition, a recycling method of basic nitrogen compounds was discovered. Strong base sodium hydroxide was used to break carbon nitrogen bond of the product from bromoacetic acid reaction, to achieve the recovering of the basic nitrogen compounds. Around 75 % of basic nitrogen compounds removal was measured by gas chromatography coupled NPD. Concentrations of neutral (95 ppm) and basic (263 ppm) nitrogen compounds in naphtha were calculated based on the concentrations of total nitrogen compounds (358 ppm) and the basic nitrogen compounds removal from dichloromethane and acetone fractions of the silica column chromatography. Furthermore, denitrogenation methods that specifically targeted the neutral nitrogen compounds from naphtha were explained. Combinations of chemical reactions with liquid-liquid extractions have been studied in detail. Sulfonic group extractions, acid extractions, and oxidative acid extractions were conducted. Hydrochloric acid and peroxide acid treatments in combination with aqueous phase extraction were proven to be effective for neutral nitrogen compounds removal. Both hydrochloric acid and peroxide acid treatments had 100% neutral nitrogen compounds removal when it was tested with pyrrole (2000 ppm) and indole (2000 ppm) in toluene model oil. Fundamental chemistry behind these extractions was explained, for better understanding of how neutral nitrogen compounds were removed by strong acid and peroxy acid.

• Subjects / Keywords

  • Cracked
  • Denitrogenation
  • Naphtha
  • Thermally

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3BR8MS5R

• 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.