Upgrading hydrothermal liquefaction biocrude oil for sustainable aviation fuel

Summers, Sabrina

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https://hdl.handle.net/2142/130081 Copy

Description

Title

Upgrading hydrothermal liquefaction biocrude oil for sustainable aviation fuel

Author(s)

Summers, Sabrina

Issue Date

2025-07-18

Director of Research (if dissertation) or Advisor (if thesis)

Zhang, Yuanhui

Doctoral Committee Chair(s)

Zhang, Yuanhui

Committee Member(s)

• Yang, Hong
• Allen, Cody
• Reid, John
• Watson, Jamison

Department of Study

Engineering Administration

Discipline

Agricultural & Biological Engr

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Circular economy
• food waste
• renewable energy
• thermochemical conversion
• transportation fuels
• waste valorization

Abstract

Increasing urbanization has led to reliance on fossil fuels, higher production of waste, and rising greenhouse gas emissions. Sustainable waste management and value-added renewable bioproducts from wet biowaste could be achieved in an integrated biorefinery via a hydrothermal liquefaction (HTL) pathway. Waste biomass is a significant feedstock for potential valorization technologies and is already the single largest source of renewable energy in the United States. HTL’s key advantage over other conversion methods is its ability to directly convert high moisture and non-lipid feedstocks into biocrude at high carbon and energy efficiencies. The yielded biocrude can be upgraded to a wide range of value-added bioproducts including fuels, chemicals, polymers, and asphaltenes. This dissertation explored the development of a novel pathway, converting food waste to sustainable aviation fuel (SAF) and other value-added products through HTL, emulsion, pretreating, and hydrotreating. First, the development and evaluation of a mobile pilot-scale HTL continuous plug flow reactor was investigated for scale-up of the HTL process. Two types of food wastes, from a food processing plant and grocery store, were processed at 280 °C for 30 min, producing biocrude oil yields of 52.19 wt% and 47.06 wt%, energy recoveries of 68.17 and 70.77%, and carbon recoveries of 66.91 and 64.78%, respectively. Due to its high feedstock capacity and reaction volume, large amounts of biocrude oil and HTL aqueous phase (HTL-AP) were obtained from this pilot-scale reactor to allow downstream research on upgrading biocrude oil for transportation fuels. Second, the production of diesel blends by emulsion of HTL biocrude fractions with the aid of a block copolymer surfactant was explored through centrifugation and ultrasonification. Four emulsion treatment variables were considered: biocrude fraction, surfactant fraction, retention time, and RPM (rotations per minute) for centrifuge or temperature for ultrasonic. Emulsion produced fuel blends with better HHV, viscosity, and TAN in comparison to HTL biocrude oil, and high solubility levels were achieved with surfactant addition and increased retention time. Additionally, thermogravimetric analysis, elemental analysis, combustion characteristics, and thermal properties gave further insight into the fuel quality of the emulsions and showed that emulsion of HTL biocrude could be an efficient and economical pathway for producing sustainable diesel blends. Third, a 3-stage pretreatment process was developed, removing water, salt, and ash, to produce a HTL biocrude oil precursor suitable for hydroprocessing. The influence of water to oil (W:O) ratio, temperature, and time on desalting efficiency was determined. After pretreatment, 81% of salt was removed, reducing total salt content to <0.1%. Improvements in elemental composition and physicochemical fuel properties were observed in biocrude oils from two feedstocks, with up to 39.8% decrease in oxygen content, 55% decrease in sulfur content, 22.2% decrease in nitrogen content, 9.86% increase in higher heating value, 73.4% decrease in total acid number, 99.9% decrease in viscosity, and 17.0% decrease in density. Compared with a single-step distillation as pretreatment, 3-stage pretreatment resulted in increased salt and heteroatom removal, improved heating value, and lower acidity. The precursor quality was viable for subsequential hydrotreating and other downstream refinery processes. Fourth, hydrotreating catalysts and parameters were screened to determine their effect on heteroatom removal. In contrast to existing work, this dissertation also established parametric relationships between hydrotreating conditions and fuel properties, such as carbon and energy recovery, boiling point distribution, and hydrocarbon abundances. It was found that molybdenum-based catalysts had comparable performance to noble metal catalysts like platinum and palladium, achieving complete deoxygenation and producing high fractions in the gasoline, kerosene, and diesel range. Temperature, catalyst load, and retention time significantly impacted the conversion efficiency and fuel properties. Furthermore, fuel properties of the hydrotreated biocrude could be accurately predicted using a regression model. Accordingly, hydrotreating conditions can be tuned to optimize carbon and energy recovery, target fuel ranges, and desired hydrocarbon types. This work contributes to the recovery of renewable carbon from waste biomass, enabling the advancement of circularity for transportation fuels. Fifth, establishment of effective catalysts and parameters enabled the hydrotreating of HTL biocrude oil to a novel SAF candidate from food waste. Specifically, this dissertation demonstrated a pathway from food waste HTL to SAF through single-stage hydrotreating using cobalt molybdenum catalyst. The SAF candidate met critical ASTM jet fuel properties without blending, including low sulfur limits, along with combustor operability limits via ASTM prescreening Tier alpha tests such as density, flash point, and freeze point. Finally, a scalable circularity index (0%

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/130081

Copyright and License Information

Copyright 2025 Sabrina Summers

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