Upgrading of biofuel by hydrotreatment process

The hydrothermal liquefaction (HTL) technique for liquefying lignocellulose biomass feedstock is often associated with low biocrude yield and poor fuel properties. As a fourth chapter of my doctoral dissertation, I have studied the HTL of southern yellow pine sawdust and the hydrotreatment (HYD) of produced biocrudes in an effort to address these challenges. Pine HTL treatment was performed within water and water–ethanol mixed reaction medium using metallic iron (Fe) as a catalyst. The rising reaction temperature in a water medium and increasing ethanol content in a mixed reaction medium were found to be effective in enhancing the biocrude yield from the non-catalytic pine HTL process. The iron catalyst facilitated enhanced biocrude yield compared to non catalytic reaction. The use of an iron catalyst also raised the calorific value of produced biocrudes in both water and water–ethanol media. The HYD treatment reduced the oxygen content of upgraded oils compared to the parent HTL biocrudes with 35–37 MJ/kg calorific values. The simulated distillation detected the maximum gasoline range compounds in upgraded oil from catalyst and water–ethanol conditions, whereas the GC–MS analysis revealed the production of increased aromatic hydrocarbons in all upgraded HYD oils.

I have also participated in biochar-supported catalysts development to combine the effect of biochar support and metal catalyst to upgrade a non-edible vegetable oil named carinata oil(Brassica carinata) for transportation fuel. Nonedible oil like carinata was selected due to its lower price compared to edible vegetable oil, no competition with food commodities and the capability to grow in harsh environment. To evaluate the role of biomass derived biochar as a catalyst support, we have incorporated widely used metallic catalysts nickel (Ni) and cobalt(Co) on biochar support. The synthesized catalysts were put into a closed reactor with carinata oil under high hydrogen pressure to remove the impurities by a process called hydrotreatment. The hydrotreatment facilitated the reaction between hydrogen and carinata oil in the presence of a catalyst to convert undesirable compounds into stabilized products. The characteristics of the catalysts were compared by analyzing the upgraded oil. Moreover, a chemical reaction mechanism was proposed based on chemical analysis of a single compound named erucic acid which can be a substitute of carinata oil. This project was a Ph.D. objective of my colleague where I played an important role in characterizing catalysts, upgraded oil and analyzing the results to assist my colleague’s publication. I have also contributed to her another Ph.D. objective where we mixed bio-oil from pyrolysis technique with carinata oil and chicken fat separately and upgraded by hydrotreatment by two type of catalysts supports: biochar and alumina. Our research goal was to understand the synergistic effect of blending pyrolysis oil with fat from animal waste or vegetable oil for hydrotreatment under different catalyst supports, and the impact on the oil quality. In summary, biochar supported catalyst performed better in the mixture of pyrolysis oil and poultry fat for upgrading by hydrotreatment technique than alumina supported catalyst and carinata oil. We also explained how different characteristics of biochar support have augmented the catalytic activities. In this work, my role was to help my colleague to thoroughly characterize the oils and analyzing the data for the bigger picture. In the last PhD objective of my colleague, the biofuel from municipal sewage sludge, algae, vegetable oil and animal fat were upgraded by hydrotreatment process to utilize as lubricant oil. The lubrication properties of these upgraded oils were compared with mineral base oil. Upgraded biocrudes from algal and sewage sludge feedstocks performed better by inducing minimum friction where animal fat derived lubricant has better low-temperature operation ability. We have identified the chemical compounds responsible for these lubricant properties from different feedstocks. My contribution was to supply algae, sludge biofuel and help my colleague to measure lubricant properties of the hydrotreated oils. Moreover, we collaborated to perform the statistical analysis of this study.

Please check the associated publication with this project:

- Hydrothermal liquefaction of southern yellow pine with downstream processing for improved fuel grade chemicals production’, Energy Conversion and Management: X, Volume 24, October 2024, 100735, DOI: https://doi.org/10.1016/j.ecmx.2024.100735

- Performance of biochar assisted catalysts during hydroprocessing of non-edible vegetable oil: Effect of transition metal source on catalytic activity,Energy Conversion and Management, Volume 252, 15 January 2022, 115131 , DOI: https://doi.org/10.1016/j.enconman.2021.115131

- Hydrotreatment of pyrolysis bio-oil with non-edible carinata oil and poultry fat for producing transportation fuels, Fuel Processing Technology, Volume 245,2023,107753,
DOI: https://doi.org/10.1016/j.fuproc.2023.107753

- Hydrocarbon biolubricants from hydrotreated renewable and waste derived liquid intermediates, Journal of Cleaner Production, Volume 409,2023,137120, DOI: https://doi.org/10.1016/j.jclepro.2023.137120