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Upgrading of crude lipid pyrolysis liquid product into drop-in hydrocarbon fuel

  • Author / Creator
    Koranteng, Samuel
  • The use of fatty acid feedstock to produce renewable fuel and value-added chemicals has recently gained a lot of attention. Pyrolysis has been used in fatty acids conversion to yield products with fuel characteristics like fossil fuel equivalent. However, the conventional heating at commercial scale is done through the walls of the reactor, placing limits on how fast the commercial reactors can heat up, in the fatty acids pyrolysis conversion process. In addition, the crude pyrolysis liquid product generated may contain residual fatty acids, which may require some level of upgrading process to make it compatible with the existing fossil fuel infrastructure, hence impacting the operational cost.
    The first objective of this thesis involved incorporation of microwave-assisted heating to pyrolyze model fatty acid, focusing on the heating rate and deoxygenation reaction. Stearic and oleic acid were pyrolyzed with silicon carbide (SiC) as heating aid in a microwave reactor at 430 ˚C for 1 hour under N2 at an initial pressure of 100 psi (689 kPa). The results showed that the set reaction temperature was successfully achieved within one minute in the stearic acid run, while in the case of the oleic acid run, the set temperature was not reached throughout the reaction time. The gas product consisted of deoxygenation products as well as light hydrocarbons, predominantly C1-C3. On the other hand, the liquid product consisted of aromatic compounds as the main product, although the conversion was low. The predominance of aromatic compounds pointed to the presence of hotspots or a lack of uniform heating, which was confirmed using a thermal paper.
    The second study investigated the catalytic effect of a stainless-steel mesh on oleic acid pyrolysis, focusing on liquid product yield and composition. Oleic acid pyrolysis was conducted in a 15 mL microreactor at 430 ˚C for 2 hours under N2, starting at atmospheric pressure. The stainless-steel mesh was thermally and chemically treated. The gas, liquid, and solid product yield varied between 9.2 – 11.7 wt. %, 82.4 – 85.5 wt.%, and 5.3 – 5.9 wt. % respectively. The liquid analysis revealed alkanes with carbon numbers ranging from C6 to C19 and residual fatty acids with carbon numbers C6 - C18. The results revealed no significant catalytic effect of the stainless-steel mesh and the microreactor material on the liquid yield and composition.
    The third study focused on incorporating deoxygenation catalysts to remove residual fatty acids in crude pyrolysis liquid product. The crude pyrolysis liquid product was treated with 65 wt.% loading of nickel on silica-alumina, 1 wt.% loading of platinum on silica, silica support, and silica-alumina support catalysts in a 15 mL microreactor at 350 ˚C for 0.5 – 2 hours under N2 at atmospheric pressure. The results revealed that the nickel on silica-alumina catalyst at 2 hours treatment resulted in complete deoxygenation of residual fatty acids in the crude pyrolysis liquid product, whereas the other catalyst and supports tested still contained acids under similar conditions.
    The final study focused on the scale-up of the catalytic deoxygenation using the nickel on silica-alumina catalyst in a continuously stirred 1 L batch reactor at 300 ˚C and 350 ˚C for 1.5 hours under N2 at atmospheric pressure. Deoxygenation was complete in the fresh nickel catalyst at 300 ˚C and 350 ˚C treatment, whereas the regenerated nickel catalyst at 300 ˚C treatment did not result in complete deoxygenation of residual fatty acid. This study demonstrated the feasibility of scaling up the deoxygenation work using nickel on silica-alumina catalyst.
    Overall, the preliminary data from the microwave study revealed some critical concerns of the microwave technology as the fatty acids feedstock did not absorb the microwave energy and the heating aid used to absorb the microwave generated hotspot in the reactor thus, influencing the formation of aromatic compounds and incomplete fatty acids conversion. Nevertheless, further investigations are required to improve the uniformity of heating in the reactor to successfully incorporate microwave-assisted heating into the existing fatty acid conversion technology. Secondly, the thesis revealed the successful incorporation of a less expensive deoxygenation catalyst to remove residual fatty acids in the crude pyrolysis liquid product to yield liquid hydrocarbon fuel.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-4vt0-s386
  • 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.